Sat, 26 Jul 2008 06:03:25 BST CiteULike: dcastro's Chang http://www.citeulike.org/user/dcastro/author/Chang CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/dcastro/article/3008096 <i>Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st, Vol. 3 (2005), pp. 1763-1767 Vol. 3.</i><br /><br />This paper proposes the novel OFDM transmission scheme that can effectively overcome ISI by adjusting CP length. As a way of combating ISI caused by multipath delay longer than guard interval, interference canceller or powerful channel coding has been proposed. Such approaches may reduce ISI, but it needs much complex computation or considerably decreases transmission efficiency to completely eliminate ISI. In our proposed scheme, CP length can be adaptively controlled by simply adjusting sampling rate. Hence it does neither much increase receiver complexity nor decrease effective data rate, compared to the conventional schemes. Our simulation results show that by employing the proposed OFDM transmission scheme, ISI can be effectively avoided in mobile environment with various multipath delays. Novel OFDM transmission scheme to overcome caused by multipath delay longer than cyclic prefix Chiwoo Lim Youngbin Chang Jaeweon Cho Panyuh Joo Hyeonwoo Lee doi:10.1109/VETECS.2005.1543624 Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st, Vol. 3 (2005), pp. 1763-1767 Vol. 3. 2008-07-16T11:27:19-00:00 2005 Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st 3 1763 1767 Vol. 3 multipath ofdm http://www.citeulike.org/user/dcastro/article/2941928 <i>Journal of Applied Physics, Vol. 90, No. 11. (2001), pp. 5483-5486.</i><br /><br />View This Record in Scopus Full-wave verification of the fundamental properties of left-handed materials in waveguide configurations C Caloz CC Chang T Itoh Journal of Applied Physics, Vol. 90, No. 11. (2001), pp. 5483-5486. 2008-06-29T18:02:13-00:00 2001 Journal of Applied Physics 90 11 5483 5486 AIP crlh lh metamaterial http://www.citeulike.org/user/dcastro/article/2920520 <i>Microwave and Wireless Components Letters, IEEE, Vol. 18, No. 1. (2008), pp. 25-27.</i><br /><br />A broadband quadrature power splitter (QPS) is developed using the metamaterial transmission line (MM TL). It consists of a Wilkinson power divider and two phase-adjusting TLs, namely a MM TL and a microstrip (MS). The slope of the phase-response curve of the MM TL is synthesized to be the same as that of the MS along with the 90deg phase increment at two design frequencies. Hence, the broadband quadrature phase difference over the desired frequency range can be obtained. In this letter, the QPS is developed at the center frequency of 2 GHz. Over the frequency range of 1.1-3.5 GHz, an amplitude imbalance of less than 0.9 dB and a phase error of less than plusmn5deg have been experimentally demonstrated. A Broadband Quadrature Power Splitter Using Metamaterial Transmission Line Chao-Hsiung Tseng Chih-Lin Chang doi:10.1109/LMWC.2007.911981 Microwave and Wireless Components Letters, IEEE, Vol. 18, No. 1. (2008), pp. 25-27. 2008-06-24T07:20:16-00:00 2008 Microwave and Wireless Components Letters, IEEE 18 1 25 27 broadband circuit divider metamaterial power http://www.citeulike.org/user/dcastro/article/2822776 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 41, No. 9. (1993), pp. 1648-1650.</i><br /><br />A slotline type of annular ring element has been developed as a new circuit component for resonator, filter, and hybrid coupler applications. Various coupling methods were devised for the use of this slotline ring in many applications. A new type of slotline dual-mode filter has been developed with a bandwidth of 12.3% and a stopband attenuation of more than 30 dB at the center frequency of 3.5 GHz. Another slotline type of cross-over hybrid ring coupler which utilized a slotline T-junction and a resistively-coupled slotline ring has also been developed with a bandwidth of more than 80%, an excellent power dividing balance of ±0.2 dB, and a fairly good isolation of 35 dB. With the ease of adding series and shunt components, the slotline annular ring element should have many applications for MICs and MMICs Slotline annular ring elements and their applications to resonator, filter and coupler design Chien-Hsun Ho Lu Fan Kai Chang doi:10.1109/22.245694 Microwave Theory and Techniques, IEEE Transactions on, Vol. 41, No. 9. (1993), pp. 1648-1650. 2008-05-22T10:40:33-00:00 1993 Microwave Theory and Techniques, IEEE Transactions on 41 9 1648 1650 coupler filter microwave resonator ring http://www.citeulike.org/user/dcastro/article/2822775 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 42, No. 12. (1994), pp. 2440-2448.</i><br /><br />The uniplanar coplanar waveguide (CPW) and slotline on a dielectric substrate have many applications to MIC and MMIC designs. A new reverse-phase CPW hybrid-ring coupler and a uniplanar CPW magic-T were developed. Experimental results showed that the hybrid-ring coupler has a 60% bandwidth centered at 3 GHz and the magic-T has a bandwidth of one octave from 2 to 4 GHz with 0.4 dB amplitude imbalance and 3.5° phase imbalance. Also, this paper presents theoretical analyses of CPW-slotline transitions using the transmission line models. Accurate modeling of nonuniform CPW and slotline radial stubs was developed using tandem connected uniform lines. Measured results of various CPW-slotline transitions agree very well with calculation. Design curves of the transitions are given for practical applications. To fully use the advantages of uniplanar structures, a 180° reverse-phase CPW-slotline back-to-back balun and a tee junction are described. Both circuits provide good amplitude and phase characteristic over a broad bandwidth due to the phase change of the circuits being independent of frequency New uniplanar coplanar waveguide hybrid-ring couplers and magic-T's Chien-Hsun Ho Lu Fan Kai Chang doi:10.1109/22.339779 Microwave Theory and Techniques, IEEE Transactions on, Vol. 42, No. 12. (1994), pp. 2440-2448. 2008-05-22T10:39:55-00:00 1994 Microwave Theory and Techniques, IEEE Transactions on 42 12 2440 2448 coplanar coupler ratrace http://www.citeulike.org/user/dcastro/article/2805135 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 44, No. 12. (1996), pp. 2411-2420.</i><br /><br />Uniplanar coplanar waveguide (CPW), coplanar strip (CPS), and slotline on dielectric substrates have many applications in microwave integrated circuit (MIC) and monolithic microwave/millimeter wave integrated circuit (MMIC) designs. New power dividers using one-section and two-section coupled CPW have been developed. These circuits provide substantially improved performance over a wider bandwidth than conventional microstrip power dividers. Measured results show that the one-section CPW power divider has greater than 20-dB isolation, less than 0.3-dB insertion loss, a 0.2-dB power dividing imbalance, and a 20 phase imbalance over a bandwidth of more than 30% centered at 3 GHz. The two-section CPW power divider has greater than 24-dB isolation, less than 0.5-dB insertion loss, a 0.1 dB power dividing imbalance, and a 1.6° phase imbalance over a bandwidth of more than 66% centered at 3 GHz. Experimental results agree well with calculated ones. In-phase and 180° out-of-phase power dividers constructed by the circuit configuration method are described in this paper. The even-odd mode excited method is used to analyze the power dividers. Also two other power dividers using asymmetrical coplanar strip (ACPS) have been developed with good performance. A 180° out-of-phase power divider is demonstrated with an amplitude imbalance of 0.4 dB and a phase difference of 180°±1° over a wide bandwidth Uniplanar power dividers using coupled CPW and asymmetrical CPS for MICs and MMICs Lu Fan Kai Chang doi:10.1109/22.554570 Microwave Theory and Techniques, IEEE Transactions on, Vol. 44, No. 12. (1996), pp. 2411-2420. 2008-05-16T11:49:28-00:00 1996 Microwave Theory and Techniques, IEEE Transactions on 44 12 2411 2420 divider microwave power tl http://www.citeulike.org/user/dcastro/article/2801362 <i>Antennas and Propagation Society International Symposium, 1999. IEEE, Vol. 4 (1999), pp. 2694-2697 vol.4.</i><br /><br />Modern military and commercial platforms such as aircraft, ship and land vehicles are congested with large number of antennas. Typically, these are operated at different frequencies with different polarization and radiation characteristics. It is therefore highly desirable to develop an antenna architecture, which cover multiple functions over different frequency bandwidths. This will greatly reduce the weight, size and cost of antenna platforms. We previously proposed and demonstrated a novel concept of reconfigurable leaky mode/patch antenna structure. One major advantage of this concept is that different types of antennas are available without increasing the total area of the antenna structure. The proposed structure is a combination of leaky mode based microstrip line and several patch antennas operated at different frequencies. The properties of this reconfigurable antenna can be controlled either by microelectromechanical (MEMS) switches or conventional switches. This paper represents, for the first time, a fully electronically controlled reconfigurable aperture using PIN diode switches, to realize the switching between the leaky mode/patch antenna operation A reconfigurable leaky mode/patch antenna controlled by PIN diode switches BCC Chang Y Qian T Itoh doi:10.1109/APS.1999.789363 Antennas and Propagation Society International Symposium, 1999. IEEE, Vol. 4 (1999), pp. 2694-2697 vol.4. 2008-05-15T11:29:14-00:00 1999 Antennas and Propagation Society International Symposium, 1999. IEEE 4 2694 2697 vol.4 antenna patch reconfigurable http://www.citeulike.org/user/dcastro/article/2782059 <i>Electronics Letters, Vol. 30, No. 22. (1994), pp. 1861-1862.</i><br /><br />A novel ring resonator topology was developed which exhibits mode suppression characteristics. The resonator achieves the mode suppression by incorporation of a stepped impedance lowpass filter directly into the ring resonator. Experimental results show that complete suppression of a ring resonator's second mode can be achieved with no increase in circuit size. The topology effectively increases the rejection bandwidth of the ring resonator Microstrip mode suppression ring resonator JM Carroll K Chang Electronics Letters, Vol. 30, No. 22. (1994), pp. 1861-1862. 2008-05-10T00:01:38-00:00 1994 Electronics Letters 30 22 1861 1862 microstrip resonator http://www.citeulike.org/user/dcastro/article/2782029 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 51, No. 4. (2003), pp. 1241-1246.</i><br /><br />This paper presents a new compact, low insertion-loss, sharp-rejection, and wide-band microstrip bandpass filter. A bandstop filter is introduced that uses a ring resonator with direct-connected orthogonal feed lines. A new bandpass filter based on the bandstop filter uses two tuning stubs to construct a wide-band passband with two sharp stopbands. Without coupling gaps between feed lines and rings, there are no mismatch and radiation losses between them and, therefore, the new filters show low insertion loss. In addition, a dual-mode characteristic is used to increase the stopband bandwidth of the new filters. A simple transmission-line model used to calculate the frequency responses of the filters shows good agreement with measurements. The filter using three cascaded rings has 3-dB fractional bandwidth of 49.3%, an insertion loss of better than 1.6 dB in the passband, a return loss of larger than 13 dB from 4.58 to 7.3 GHz, and two rejections of greater than 40 dB within 2.75-4.02 and 7.73-9.08 GHz. The high-performance, compact-size, and low-cost filter was designed for reducing the interference in full duplex systems in satellite communications. Compact, low insertion-loss, sharp-rejection, and wide-band microstrip bandpass filters Lung-Hwa Hsieh Kai Chang doi:10.1109/TMTT.2003.809643 Microwave Theory and Techniques, IEEE Transactions on, Vol. 51, No. 4. (2003), pp. 1241-1246. 2008-05-09T23:50:43-00:00 2003 Microwave Theory and Techniques, IEEE Transactions on 51 4 1241 1246 bandpass compact filter loss low microstrip http://www.citeulike.org/user/dcastro/article/2782013 <i>Circuits and Systems II: Express Briefs, IEEE Transactions on [see also Circuits and Systems II: Analog and Digital Signal Processing, IEEE Transactions on], Vol. 52, No. 6. (2005), pp. 336-338.</i><br /><br />Signal-to-noise ratio (SNR) measurement is required in many receivers and systems of communications. In this brief, we derive a new SNR's estimator based on the second and fourth-order moments of the complex signals of quadrature phase-shift keying modulations. The mean square error of the estimated SNR by the proposed algorithm is smaller than that by other methods for a low SNR with limited samples. A new SNR's estimator for QPSK Modulations in an AWGN channel Guangliang Ren Yilin Chang Hui Zhang doi:10.1109/TCSII.2005.849008 Circuits and Systems II: Express Briefs, IEEE Transactions on [see also Circuits and Systems II: Analog and Digital Signal Processing, IEEE Transactions on], Vol. 52, No. 6. (2005), pp. 336-338. 2008-05-09T23:47:09-00:00 2005 Circuits and Systems II: Express Briefs, IEEE Transactions on [see also Circuits and Systems II: Analog and Digital Signal Processing, IEEE Transactions on] 52 6 336 338 channel estimator modulation noise qpsk snr http://www.citeulike.org/user/dcastro/article/2782006 <i>Microwave Symposium Digest, 1988., IEEE MTT-S International (1988), pp. 963-966 vol.2.</i><br /><br />A description is presented of active antennas and arrays fabricated using microstrip patch antennas and Gunn diodes. Injection-locking experiments were carried out on these <e1>X</e1>-band antennas to achieve frequency coherency and to calculate the circuit <e1>Q</e1>-factor. An electronic tuning range of over 9% has been achieved for the single active patch element. A two-element active array was also developed. The output power levels from the two elements were combined in free space, resulting in higher power in the main beam. The tuning range was much narrower and the antenna pattern broke from a single beam into two separate beams as the DC bias voltage was varied. The breakup limits the practical tuning range Microstrip active antennas and arrays KA Hummer K Chang doi:10.1109/MWSYM.1988.22191 Microwave Symposium Digest, 1988., IEEE MTT-S International (1988), pp. 963-966 vol.2. 2008-05-09T23:43:10-00:00 1988 Microwave Symposium Digest, 1988., IEEE MTT-S International 963 966 vol.2 active antenna array microstrip http://www.citeulike.org/user/dcastro/article/2776280 <i>Antennas and Propagation Society International Symposium, 1993. AP-S. Digest (1993), pp. 656-659 vol.2.</i><br /><br />The design and measurement of the passive and active slotline ring antennas are discussed. A simple transmission line method is used to predict the resonant frequency of the slotline ring antenna. Two feed methods for the passive slotline ring antenna are described. A new type of FET active slotline ring antenna is also presented. The measured H-field radiation patterns of the passive and active slotline ring antennas showed that the active antenna had improved copolar pattern and crosspolar level. This active radiating element offers a simple, lightweight, low-cost, small, reproducible, and truly planar active source for quasi-optical power combiners and mixers. The circuit is also amenable to monolithic circuit integration for mass production On the study of passive and active slotline ring antennas CH Ho L Fan K Chang doi:10.1109/APS.1993.385261 Antennas and Propagation Society International Symposium, 1993. AP-S. Digest (1993), pp. 656-659 vol.2. 2008-05-09T16:41:53-00:00 1993 Antennas and Propagation Society International Symposium, 1993. AP-S. Digest 656 659 vol.2 active antenna passive http://www.citeulike.org/user/dcastro/article/2776274 <i>Electronics Letters, Vol. 29, No. 6. (1993), pp. 521-522.</i><br /><br />A new active slotline ring antenna using an FET is presented. A simple transmission line method was used to predict the resonance frequency of the FET active slotline ring antenna with good agreement. The active antenna radiated 21.6 mW with 18% efficiency at 7.7 GHz New FET factive slotline ring antenna CH Ho L Fan K Chang Electronics Letters, Vol. 29, No. 6. (1993), pp. 521-522. 2008-05-09T16:40:19-00:00 1993 Electronics Letters 29 6 521 522 active antenna fet http://www.citeulike.org/user/dcastro/article/2776223 <i>Electronics Letters, Vol. 27, No. 23. (1991), 2117.</i><br /><br />A 35 GHz integrated circuit rectifying antenna (rectenna) has been developed using a microstrip dipole antenna and beam-lead mixer diode. Greater than 33% conversion efficiency has been achieved. The circuit should have applications in microwave/millimetre-wave power transmission and detection 35 GHz integrated circuit rectifying antenna with 33% efficiency TW Yoo K Chang Electronics Letters, Vol. 27, No. 23. (1991), 2117. 2008-05-09T16:09:23-00:00 1991 Electronics Letters 27 23 2117 active antenna http://www.citeulike.org/user/dcastro/article/2774605 <i>Microwave Symposium Digest, 1996., IEEE MTT-S International, Vol. 1 (1996), pp. 333-336 vol.1.</i><br /><br />A cavity backed, Gunn diode driven, self-mixing active inverted stripline circular patch antenna has been developed. The active antenna provides good radiation patterns with cross-polarization levels 18 dB below copolarization at boresight. The self-mixing performance shows that the circuit has a 2 dB conversion gain for IFs up to 450 MHz and a double sideband noise figure of 15 dB at 200 MHz. The antenna is suitable for use as a transceiver for short communications links or as a microwave identification transceiver A self-mixing active antenna for communication and vehicle identification applications CM Montiel L Fan K Chang doi:10.1109/MWSYM.1996.508524 Microwave Symposium Digest, 1996., IEEE MTT-S International, Vol. 1 (1996), pp. 333-336 vol.1. 2008-05-09T07:25:52-00:00 1996 Microwave Symposium Digest, 1996., IEEE MTT-S International 1 333 336 vol.1 active antenna mixer http://www.citeulike.org/user/dcastro/article/2774626 <i>Microwaves, Antennas and Propagation, IEE Proceedings -, Vol. 147, No. 6. (2000), pp. 479-482.</i><br /><br />An active microstrip antenna with self-mixing oscillator is introduced with double-ring geometry. It is simple to implement and presents a dual-frequency response in the operating range of C-band (3.7-4.2 GHz). The circuit with common-drain FET is used as an oscillator as well as a mixer. This active microstrip antenna can be applied in ROTV of satellite communication as the down converter Double-ring active microstrip antenna and self-mixing oscillator in C-band JC Liu PC Lu DC Chang CC Chang doi:10.1049/ip-map:20000794 Microwaves, Antennas and Propagation, IEE Proceedings -, Vol. 147, No. 6. (2000), pp. 479-482. 2008-05-09T07:33:51-00:00 2000 Microwaves, Antennas and Propagation, IEE Proceedings - 147 6 479 482 active antenna c-band microstrip mixer oscillator http://www.citeulike.org/user/dcastro/article/2774599 <i>Microwave Symposium Digest, 1998 IEEE MTT-S International, Vol. 2 (1998), pp. 997-1000 vol.2.</i><br /><br />This paper presents a novel idea that the power is fed from the patch antenna coupler to form a five-element Chebyshev active antenna FET amplifying linear array. An equivalent lumped element circuit was developed to model the mutual coupling having good agreement with experiments. The power level coupled to the transmission line can be controlled by adjusting the length and the gap of the transmission line. The active patch-fed antenna coupler array has the advantages of a single input port, no power divider required, good and controllable radiation patterns, ease of bias, and compactness Novel active antenna amplifying arrays Yao-Chou Yang Shyh-Jong Chung Kai Chang doi:10.1109/MWSYM.1998.705160 Microwave Symposium Digest, 1998 IEEE MTT-S International, Vol. 2 (1998), pp. 997-1000 vol.2. 2008-05-09T07:24:23-00:00 1998 Microwave Symposium Digest, 1998 IEEE MTT-S International 2 997 1000 vol.2 active amplifier antenna array http://www.citeulike.org/user/dcastro/article/2774540 <i>Signals, Systems, and Electronics, 1995. ISSSE '95, Proceedings., 1995 URSI International Symposium on (1995), pp. 13-16.</i><br /><br />We consider an inverted stripline active antenna configuration for system applications. Solid-state devices can be directly integrated with the antenna to perform various functions. A two-way communication system using two integrated active antenna transceivers was demonstrated. The transmitter provides 63 mW output power with an estimated maximum link distance of 4.8 km Integrated microstrip active antennas and their applications Kai Chang doi:10.1109/ISSSE.1995.497923 Signals, Systems, and Electronics, 1995. ISSSE '95, Proceedings., 1995 URSI International Symposium on (1995), pp. 13-16. 2008-05-09T06:48:28-00:00 1995 Signals, Systems, and Electronics, 1995. ISSSE '95, Proceedings., 1995 URSI International Symposium on 13 16 active antenna integrated http://www.citeulike.org/user/dcastro/article/2774529 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 46, No. 10. (1998), pp. 1546-1551.</i><br /><br />The general theory for oscillator and mixer design is applied to develop an X-band self-mixing oscillator antenna. The antenna uses a Gunn diode as the active device that provides the oscillations and self-mixing operations. The circuit uses a slotline ring resonator for frequency stabilization and can be modified to include a varactor diode for wide-band frequency tuning. The circuit performance is compared with theoretical results derived from simple transmission-line models. The radiation patterns of the self-mixing oscillator antenna are also compared with those measured from a similarly configured passive antenna. Since the radiated power also serves as the local oscillator (LO) frequency for the self-mixing operation, the circuit is useful as a half-duplex transceiver. When the self-mixing operation is not required, a single oscillator antenna can be used as a transmitter and several units can be assembled in a planar array for spatial powercombining applications An X-band self-mixing oscillator antenna for transceiver and spatial power-combining applications CM Montiel Lu Fan Kai Chang doi:10.1109/22.721163 Microwave Theory and Techniques, IEEE Transactions on, Vol. 46, No. 10. (1998), pp. 1546-1551. 2008-05-09T06:44:52-00:00 1998 Microwave Theory and Techniques, IEEE Transactions on 46 10 1546 1551 active antenna oscillator transceiver http://www.citeulike.org/user/dcastro/article/2768630 <i>Antennas and Propagation Society International Symposium, 2001. IEEE, Vol. 2 (2001), pp. 490-493 vol.2.</i><br /><br />This paper presents a new diplexer using one-dimensional (1D) photonic band gap (PBG) structures to switch transmit/receive paths in a multiband transceiver antenna system. The 1D PBG structure consists of periodically etched holes on the ground plane along a microstrip-line. The new diplexer is optimized by parametric analysis, tapering and meandering of PBG bandstop filters, and full-wave simulation. A diplexer operating at four bands of 10, 12, 19, and 21 GHz is demonstrated with measured and simulated results. The new 1D PBG diplexer should be useful in multiband transceiver systems A new PBG diplexer for a multiband transceiver antenna system Tae-Yeoul Yun Kai Chang doi:10.1109/APS.2001.959768 Antennas and Propagation Society International Symposium, 2001. IEEE, Vol. 2 (2001), pp. 490-493 vol.2. 2008-05-08T06:28:49-00:00 2001 Antennas and Propagation Society International Symposium, 2001. IEEE 2 490 493 vol.2 antenna diplexer multiband pbg transceiver http://www.citeulike.org/user/dcastro/article/2768626 <i>Microwave and Wireless Components Letters, IEEE, Vol. 15, No. 4. (2005), pp. 268-270.</i><br /><br />A compact wideband high-rejection microstrip bandstop filter (BSF) is presented. This filter combines two traditional BSFs: open-stub filter and spurline filter. Due to the inherently compact characteristics of the spurline, the proposed filter shows a better rejection performance than open-stub BSF without increasing the circuit size. From 3.7 to 5.4 GHz, the proposed BSF has a rejection of better than 20 dB and the maximum rejection level of 61 dB. Application of this BSF to suppress the second harmonic of an open-loop ring bandpass filter is also investigated with a 40-dB suppression improvement achieved. Compact microstrip bandstop filter using open stub and spurline Wen-Hua Tu Kai Chang doi:10.1109/LMWC.2005.845739 Microwave and Wireless Components Letters, IEEE, Vol. 15, No. 4. (2005), pp. 268-270. 2008-05-08T06:28:24-00:00 2005 Microwave and Wireless Components Letters, IEEE 15 4 268 270 compact filter microstrip http://www.citeulike.org/user/dcastro/article/2768625 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 49, No. 10. (2001), pp. 1818-1820.</i><br /><br />This paper introduces a three-port microstrip multifrequency diplexer used in a phased-array transceiver system that employs band-stop filters with open-circuited stubs for band selection and separation. The diplexer is designed to take 10, 12, 19, and 21 GHz into port 1 and to separate 10 and 19 GHz to port 2 and 12 and 21 GHz to part 3 with minimal dispersion. The insertion loss for each frequency varies from 0.4 to 3.4 db and the return loss is better than 10 dB. The isolation between channels at the four frequencies is greater than 50 dB. Each passband created between adjacent stopbands has a bandwidth over 1 GHz. The microstrip diplexer is designed using periodic stubs that collectively have the advantages of low insertion loss, high isolation and rejection, wide-band performance on each channel, and easy fabrication. This type of diplexer has many applications in multifrequency transceivers for communication systems Wide-band low-loss high-isolation microstrip periodic-stub diplexer for multiple-frequency applications B Strassner K Chang doi:10.1109/22.954789 Microwave Theory and Techniques, IEEE Transactions on, Vol. 49, No. 10. (2001), pp. 1818-1820. 2008-05-08T06:28:18-00:00 2001 Microwave Theory and Techniques, IEEE Transactions on 49 10 1818 1820 diplexer frequency high isolation loss low microstrip multiple wideband http://www.citeulike.org/user/dcastro/article/2762269 <i>Microwave Symposium Digest, 1993., IEEE MTT-S International (1993), pp. 585-588 vol.2.</i><br /><br />A novel uniplanar hybrid ring coupler using coplanar waveguide (CPW) and slotline is presented. The coupler provides substantially improved amplitude and phase characteristics over a broad bandwidth compared to the conventional microstrip hybrid ring couplers. Experimental results show that the new coupler has a bandwidth of one octave from 2 GHz to 4 GHz with a +or-0.25-dB power dividing balance and a +or-1 degrees phase balance.<<ETX>> A broad-band uniplanar slotline hybrid ring coupler with over one octave bandwidth CH Ho L Fan K Chang doi:10.1109/MWSYM.1993.276870 Microwave Symposium Digest, 1993., IEEE MTT-S International (1993), pp. 585-588 vol.2. 2008-05-06T18:38:50-00:00 1993 Microwave Symposium Digest, 1993., IEEE MTT-S International 585 588 vol.2 broadband coupler http://www.citeulike.org/user/dcastro/article/2762267 <i>Antennas and Propagation, IEEE Transactions on, Vol. 51, No. 10. (2003), pp. 3006-3009.</i><br /><br />A novel single-feed broadband circularly polarized patch antenna is proposed. The proposed antenna has a simple structure, consisting of a corner-truncated square radiating patch, an L-shaped ground plane, and a probe feed. Through a via hole in the vertical ground of the L-shaped ground plane, the radiating patch is easily excited by a probe feed oriented in the same plane as the patch, and circular polarization (CP) radiation over a wide frequency range (>10%) is achieved. Experimental results of a constructed prototype with the center operating frequency at about 2500 MHz showed that the antenna has an impedance bandwidth (1.5:1 VSWR) of about 30%, a 3-dB axial-ratio CP bandwidth of about 10.4%, and a gain level of 8.5 dBi or larger within the CP bandwidth. In addition to the low cost of the proposed antenna due to its simple structure, the obtained CP performance is among the best that have been reported for single-feed single-element patch antennas. Low-cost broadband circularly polarized patch antenna Fa-Shian Chang Kin-Lu Wong Tzung-Wern Chiou doi:10.1109/TAP.2003.818010 Antennas and Propagation, IEEE Transactions on, Vol. 51, No. 10. (2003), pp. 3006-3009. 2008-05-06T18:38:45-00:00 2003 Antennas and Propagation, IEEE Transactions on 51 10 3006 3009 antenna broadband circularly patch polarisation http://www.citeulike.org/user/dcastro/article/2762266 <i>Microwave Symposium Digest, 1994., IEEE MTT-S International (1994), pp. 1749-1752 vol.3.</i><br /><br />A novel circular patch rectifying antenna (rectenna) has been developed which converts microwave energy into DC power at 2.45 GHz. Dual polarization is achieved by two orthogonal microstrip feed lines. Rectification is achieved by GaAs Schottky-barrier diodes located on each feed line. A 48% conversion efficiency from microwave power to DC power was achieved. The design was based on a nonlinear circuit analysis A dual polarized circular patch rectifying antenna at 2.45 GHz for microwave power conversion and detection JO Mcspadden K Chang doi:10.1109/MWSYM.1994.335103 Microwave Symposium Digest, 1994., IEEE MTT-S International (1994), pp. 1749-1752 vol.3. 2008-05-06T18:38:43-00:00 1994 Microwave Symposium Digest, 1994., IEEE MTT-S International 1749 1752 vol.3 antenna circular dual patch polarisation http://www.citeulike.org/user/dcastro/article/2762265 <i>Electronics Letters, Vol. 24, No. 21. (1988), pp. 1347-1348.</i><br /><br />An FET source has been integrated with a microstrip patch antenna to form an active radiating module. The patch antenna serves both as a radiating element and a resonator in the feedback loop for the FET oscillator. Power output of 17 mW was achieved at 5.7 GHz Active radiating element using FET source integrated with microstrip patch antenna K Chang KA Hummer GK Gopalakrishnan Electronics Letters, Vol. 24, No. 21. (1988), pp. 1347-1348. 2008-05-06T18:38:41-00:00 1988 Electronics Letters 24 21 1347 1348 active antenna fet microstrip patch http://www.citeulike.org/user/dcastro/article/2762264 <i>Electronics Letters, Vol. 26, No. 12. (1990), pp. 774-775.</i><br /><br />A new transmission line based theory is developed to study symmetric/asymmetric microstrip ring resonators. The selective splitting of odd modes in certain asymmetric structures can be used to realise bandpass filters. The theory predicts the characteristics of these resonators quite accurately Bandpass characteristics of split-modes in asymmetric ring resonators GK Gopalakrishnan K Chang Electronics Letters, Vol. 26, No. 12. (1990), pp. 774-775. 2008-05-06T18:38:39-00:00 1990 Electronics Letters 26 12 774 775 bandpass resonator ring http://www.citeulike.org/user/dcastro/article/2762256 <i>Microwave Symposium Digest, 1990., IEEE MTT-S International (1990), pp. 793-796 vol.2.</i><br /><br />A Gunn device integrated with a planar, endfire notch antenna is described. A simple transmission-line model, has been developed to optimize the passive and active circuit parameters. An electronic tuning bandwidth of 275 MHz centered at 9.33 GHz with a maximum power output of 37.5 mW was accomplished. Two active notches in a broadside array configuration were injection-locked at 9.484 GHz with a 30-MHz locking bandwidth and well over 90% power combining efficiency Active endfire antenna elements and power combiners using notch antennas JA Navarro YH Shu K Chang doi:10.1109/MWSYM.1990.99699 Microwave Symposium Digest, 1990., IEEE MTT-S International (1990), pp. 793-796 vol.2. 2008-05-06T18:35:58-00:00 1990 Microwave Symposium Digest, 1990., IEEE MTT-S International 793 796 vol.2 antenna array http://www.citeulike.org/user/dcastro/article/2762254 <i>Microwave Symposium Digest, 1991., IEEE MTT-S International (1991), pp. 589-592 vol.2.</i><br /><br />A novel microwave optoelectronic mixer was fabricated on semi-insulating GaAs by monolithically integrating Schottky diode photodetectors into a microstrip ring resonator. Resistive mixing occurs when the conductance of the detector is modulated, and parametric amplification occurs when the capacitive reactance of the detector is modulated. The mixer shows very good potential for application in wideband fiber optic systems Resistive mixing and parametric up-conversion of microwave optoelectronic signals in a microstrip ring resonator GK Gopalakrishnan BW Fairchild CL Yeh CS Park K Chang MH Weichold HF Taylor doi:10.1109/MWSYM.1991.147071 Microwave Symposium Digest, 1991., IEEE MTT-S International (1991), pp. 589-592 vol.2. 2008-05-06T18:35:56-00:00 1991 Microwave Symposium Digest, 1991., IEEE MTT-S International 589 592 vol.2 mixer resonator ring http://www.citeulike.org/user/dcastro/article/2762255 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 36, No. 12. (1988), pp. 1733-1739.</i><br /><br />A microstrip ring resonator circuit loaded with two p-i-n diodes has been developed for use as a switchable filter. By replacing one p-i-n diode with a varactor diode, the switchable filter can be made electronically tunable. Isolation exceeding 20 dB with 9% tuning bandwidth was demonstrated. An analysis based on transmission line theory was used to model both circuits. The analysis includes the effects of diode parasitics, coupling gaps, dispersion, and mounting-gap capacitance. The experimental results agree very well with the theoretical calculation Theoretical and experimental investigation of novel varactor-tuned switchable microstrip ring resonator circuits TS Martin F Wang K Chang doi:10.1109/22.17407 Microwave Theory and Techniques, IEEE Transactions on, Vol. 36, No. 12. (1988), pp. 1733-1739. 2008-05-06T18:35:57-00:00 1988 Microwave Theory and Techniques, IEEE Transactions on 36 12 1733 1739 resonator ring http://www.citeulike.org/user/dcastro/article/2762253 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 50, No. 2. (2002), pp. 453-460.</i><br /><br />A transmission-line model is used to extract the equivalent lumped-element circuits for the closed- and open-loop ring resonators. The unloaded Q values of the ring resonators can be calculated from the equivalent lumped elements G, L, and C. Four different configurations of microstrip ring resonators fabricated on low and high dielectric-constant substrates are used to investigate the lumped elements and unloaded Qs. The largest difference between the measured and calculated unloaded Q is 5.7%, which is due to measurement uncertainties and accuracies of the calculation. These simple expressions introduce an easy method for analyzing ring resonators in filters and provide, for the first time, a means of predicting their unloaded Q Equivalent lumped elements G, L, C, and unloaded Q's of closed- and open-loop ring resonators Lung-Hwa Hsieh Kai Chang doi:10.1109/22.982223 Microwave Theory and Techniques, IEEE Transactions on, Vol. 50, No. 2. (2002), pp. 453-460. 2008-05-06T18:35:53-00:00 2002 Microwave Theory and Techniques, IEEE Transactions on 50 2 453 460 lumped resonator ring http://www.citeulike.org/user/dcastro/article/2762251 <i>Electronics Letters, Vol. 30, No. 2. (1994), pp. 148-149.</i><br /><br />Perturbations not affecting the intrinsic resonance of a microstrip ring are introduced to increase the coupling periphery between the feedline and the resonator. Compared to conventional excitation, the authors demonstrate an average improvement of approximately 6 dB in the insertion loss.<<ETX>> Novel excitation schemes for the microstrip ring resonator with lower insertion loss GK Gopalakrishnan K Chang Electronics Letters, Vol. 30, No. 2. (1994), pp. 148-149. 2008-05-06T18:35:49-00:00 1994 Electronics Letters 30 2 148 149 microstrip resonator ring http://www.citeulike.org/user/dcastro/article/2762250 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 36, No. 3. (1988), pp. 505-513.</i><br /><br />An analytical method based on the aperture coupling theory and the derivation of the <e1>S</e1>-parameter matrix has been developed for modeling a microstrip line coupled to a microstrip patch antenna using a circular coupling aperture. Closed-form solutions were derived for scattering parameters of the coupling circuit. Input impedance and matching condition can be calculated from the equivalent six-port network. The theoretical results agree well with the measurements. The analysis should have many applications in active array and spatial power combining systems Network modeling of an aperture coupling between microstrip line and patch antenna for active array applications X Gao K Chang doi:10.1109/22.3542 Microwave Theory and Techniques, IEEE Transactions on, Vol. 36, No. 3. (1988), pp. 505-513. 2008-05-06T18:35:45-00:00 1988 Microwave Theory and Techniques, IEEE Transactions on 36 3 505 513 active antenna array coupling line microstrip patch http://www.citeulike.org/user/dcastro/article/2762249 <i>Microwave Symposium Digest, 1991., IEEE MTT-S International (1991), pp. 1257-1260 vol.3.</i><br /><br />A Gunn device in a varactor-tuned slotline coplanar waveguide (CPW) resonator has been integrated with a planar, endfire notch antenna. The varactor provides more than 14% tuning bandwidth centered at 9.6 GHz, with a power output of 14.5±-0.8 dBm. Wideband tunable quasi-optical power combiners have also been developed using the active elements. The signal spectrum remains clean and very stable with nearly constant power output throughput the electronic tuning range. These results offer a simple, lightweight, low-cost, reproducible, and truly planar active wideband tunable source for many microwave applications Wideband integrated varactor-tunable active notch antennas and power combiners JA Navarro YH Shu K Chang doi:10.1109/MWSYM.1991.147250 Microwave Symposium Digest, 1991., IEEE MTT-S International (1991), pp. 1257-1260 vol.3. 2008-05-06T18:35:43-00:00 1991 Microwave Symposium Digest, 1991., IEEE MTT-S International 1257 1260 vol.3 active antenna combining integrated power wideband http://www.citeulike.org/user/dcastro/article/2762248 <i>Electronics Letters, Vol. 28, No. 20. (1992), pp. 1853-1854.</i><br /><br />A novel dual-FET active patch antenna element for quasi-optical power combining arrays is described. The circuit uses two FETs which symmetrically load a split patch antenna. The push-pull operation of the devices decreases H-plane crosspolarisation dramatically. A power output of 47 mW was achieved at 8.1 GHz Novel FET active patch antenna XD Wu K Leverich K Chang Electronics Letters, Vol. 28, No. 20. (1992), pp. 1853-1854. 2008-05-06T18:35:40-00:00 1992 Electronics Letters 28 20 1853 1854 active antenna fet patch http://www.citeulike.org/user/dcastro/article/2762241 <i>Microwave and Guided Wave Letters, IEEE [see also IEEE Microwave and Wireless Components Letters], Vol. 4, No. 9. (1994), pp. 301-302.</i><br /><br />We report the design, measured and simulated performance of a novel W-band monolithic, singly balanced resistive FET mixer utilizing 0.1-μm pseudomorphic AlGaAs/InGaAs on GaAs HEMT technology. At an LO drive of +8 dBm, this mixer has exhibited a minimum measured conversion loss of 12.8 dB, nearly a 10 dB improvement over previously reported data in this frequency range. Furthermore, the mixer figure of merit, defined as P_1-dB,in-P_LO, is at least +2 dBm, which is nominally 6 dBm better than that of comparable diode mixers at W-band. These results indicate the excellent potential of this mixer for integration with other circuit components in fully monolithic subsystems A W-band monolithic, singly balanced resistive mixer with low conversion loss KW Chang EW Lin H Wang KL Tan WH Ku doi:10.1109/75.311514 Microwave and Guided Wave Letters, IEEE [see also IEEE Microwave and Wireless Components Letters], Vol. 4, No. 9. (1994), pp. 301-302. 2008-05-06T18:33:22-00:00 1994 Microwave and Guided Wave Letters, IEEE [see also IEEE Microwave and Wireless Components Letters] 4 9 301 302 balanced mixer http://www.citeulike.org/user/dcastro/article/2762240 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 39, No. 12. (1991), pp. 1980-1986.</i><br /><br />The design and fabrication of four broadband monolithic passive baluns including CPW Marchand, multilayer MS Marchand, planar-transformer and broadside-coupled line baluns are presented. Operational frequencies range from 1.5 GHz to 24 GHz. Maximum relative bandwidths in excess of 3:1 are achieved. Simulated performances using full wave electromagnetic analysis are shown to agree with the measured results. Two accurate equivalent circuit models constructed from either electromagnetic simulated or measured S-parameters are developed for the MS Marchand and transformer baluns making the optimization of baluns and circuit design using the baluns much more efficient. The design of monolithic double-balanced diode mixer using two planar-transformer baluns is also presented. Without DC bias, the mixer shows a minimum conversion loss of 6 dB with the RF at 5 GHz and a LO drive of 15 dBm at 4 GHz. The measured input IP₃ of this mixer is better than 15 dBm over the 4 to 5.75 GHz frequency band Broadband monolithic passive baluns and monolithic double-balanced mixer Chen KW Chang SB Bui H Wang GS Dow LCT Liu TS Lin WS Titus doi:10.1109/22.106536 Microwave Theory and Techniques, IEEE Transactions on, Vol. 39, No. 12. (1991), pp. 1980-1986. 2008-05-06T18:33:19-00:00 1991 Microwave Theory and Techniques, IEEE Transactions on 39 12 1980 1986 balanced balun broadband mixer passive http://www.citeulike.org/user/dcastro/article/2762226 <i>Microwave Symposium Digest, 1998 IEEE MTT-S International, Vol. 1 (1998), pp. 327-330 vol.1.</i><br /><br />This paper presents several power amplifier approaches that promise to significantly improve efficiency, while meeting the linearity requirements of advanced, spectrally efficient wireless systems. The approaches include: a) use of active integrated antenna structures that provide harmonic terminations for high efficiency Class F amplifiers; b) integrated dc-dc converters for power conditioning and envelope restoration; c) switching mode amplifiers based on bipolar transistors with controlled saturation; and d) the use of band-pass delta-sigma modulators to tailor input signals Device and circuit approaches for improved linearity and efficiency in microwave transmitters PM Asbeck T Itoh Y Qian MF Chang L Milstein G Hanington PF Chen V Schultz DW Lee DW Lee J Arun A10 doi:10.1109/MWSYM.1998.689385 Microwave Symposium Digest, 1998 IEEE MTT-S International, Vol. 1 (1998), pp. 327-330 vol.1. 2008-05-06T18:30:58-00:00 1998 Microwave Symposium Digest, 1998 IEEE MTT-S International 1 327 330 vol.1 efficiency microwave transmitter http://www.citeulike.org/user/dcastro/article/2762221 <i>Electrical Performance of Electronic Packaging, 1998. IEEE 7th topical Meeting on (1998), pp. 79-82.</i><br /><br />A novel interconnect and packaging concept for high-density, broadband mixed signal silicon MMICs is presented. Compared to conventional microstrip or stripline-based structures, the proposed silicon/metal/polyimide (SIMPOL) interconnect is very promising for extremely high isolation (>100 dB) between adjacent channels from DC up to 50 GHz, as indicated by simulations using a pre-verified full-wave FDTD code A novel high isolation interconnect for broadband mixed signal silicon MMICs Y Qian MF Chang T Itoh doi:10.1109/EPEP.1998.733839 Electrical Performance of Electronic Packaging, 1998. IEEE 7th topical Meeting on (1998), pp. 79-82. 2008-05-06T18:30:49-00:00 1998 Electrical Performance of Electronic Packaging, 1998. IEEE 7th topical Meeting on 79 82 broadband mixer http://www.citeulike.org/user/dcastro/article/2762217 <i>Microwave Symposium Digest, 1999 IEEE MTT-S International, Vol. 4 (1999), pp. 1419-1422 vol.4.</i><br /><br />This paper reports a novel technique for high efficiency and broadband excitation of the first higher order leaky mode in microstrips. A uniplanar microstrip-to-CPS transition is employed to launch the odd leaky mode, and the mode purity is enhanced by suppressing the even fundamental mode using an optimized mode suppressor. An X-band prototype demonstrates excellent mode conversion efficiency as predicted by simulations. A record bandwidth of 20.2% is achieved for a microstrip leaky-wave source based on this newly proposed structure High efficiency and broadband excitation of leaky mode in microstrip structures Y Qian BCC Chang T Itoh KC Chen CKC Tzuang doi:10.1109/MWSYM.1999.780215 Microwave Symposium Digest, 1999 IEEE MTT-S International, Vol. 4 (1999), pp. 1419-1422 vol.4. 2008-05-06T18:28:46-00:00 1999 Microwave Symposium Digest, 1999 IEEE MTT-S International 4 1419 1422 vol.4 antenna broadband microstrip http://www.citeulike.org/user/dcastro/article/2762107 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 37, No. 7. (1989), pp. 1078-1084.</i><br /><br />Two types of active antenna elements have been studied experimentally. One type uses a microstrip antenna with an active device mounted directly on the antenna. The other uses an active device coupled to a microstrip patch antenna through an aperture. Microstrip active antenna elements and two-element arrays have been demonstrated for both types of circuits. Injection locking of the antenna elements has been achieved through space and mutual coupling. The circuit <e1>Q</e1> factor was calculated based on the locking gain and the locking bandwidth. The power output from two elements has been successfully combined in free space with a combining efficiency of over 90%. For a single active antenna with a Gunn diode mounted directly on the patch, an electronic tuning range exceeding 9% has been achieved by varying the DC bias. The results should have many applications in low-cost active arrays, active transmitters, and spatial power combiners Experiments on injection locking of active antenna elements for active phased arrays and spatial power combiners K Chang KA Hummer JL Klein doi:10.1109/22.24551 Microwave Theory and Techniques, IEEE Transactions on, Vol. 37, No. 7. (1989), pp. 1078-1084. 2008-05-06T17:19:30-00:00 1989 Microwave Theory and Techniques, IEEE Transactions on 37 7 1078 1084 active antenna array phased http://www.citeulike.org/user/dcastro/article/2755560 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 44, No. 10. (1996), pp. 1642-1649.</i><br /><br />Integrated and active antennas incorporate component functions directly at the antenna terminals thereby reducing the size, weight, and cost of many microwave systems. Active integrated antennas have been used for distributed oscillators in spatial and quasi-optical power combining arrays, but the concept can be extended to include such applications as Doppler sensors, radars, and wireless communications to produce compact, low-cost products. In this paper, we report that a field-effect transistor (FET) and a Schottky mixer diode have been integrated within an inverted patch antenna for transceiver applications. The position of the mixer diode on the patch was optimized to achieve a minimum conversion loss. Preliminary results exhibit a 5.5 dB isotropic mixer conversion loss at 6 GHz for a 200 MHz intermediate frequency. The FET serves as both the transmitter and the local oscillator at 5.8 GHz. A two-way communication system using these transceivers is proposed Low cost and compact active integrated antenna transceiver for system applications RA Flynt Lu Fan JA Navarro Kai Chang doi:10.1109/22.538955 Microwave Theory and Techniques, IEEE Transactions on, Vol. 44, No. 10. (1996), pp. 1642-1649. 2008-05-05T08:00:29-00:00 1996 Microwave Theory and Techniques, IEEE Transactions on 44 10 1642 1649 active antenna integrated http://www.citeulike.org/user/dcastro/article/2755519 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 50, No. 3. (2002), pp. 937-944.</i><br /><br />This paper provide a review of the active integrated antenna (AIA) technologies. After a brief introduction on the definition and some historical remarks, the paper concentrates on the research effort on the past decades or so. The AlAs are reviewed in its various functions. First, an oscillator-type AIA is presented, followed by very interesting aspects of coupled oscillator arrays for phase control. Use of an AIA concept for efficient RF front ends is described with examples on high-power amplifier AlAs. Next, a phase-conjugation-based retrodirective array is reviewed. Finally, AIA systems for receiving, transmitting, and duplexing are reviewed Active integrated antennas K Chang York PS Hall T Itoh doi:10.1109/22.989976 Microwave Theory and Techniques, IEEE Transactions on, Vol. 50, No. 3. (2002), pp. 937-944. 2008-05-05T07:59:39-00:00 2002 Microwave Theory and Techniques, IEEE Transactions on 50 3 937 944 active antenna integrated http://www.citeulike.org/user/dcastro/article/2085926 <i>Antenna Technology: Small Antennas and Novel Metamaterials, 2005. IWAT 2005. IEEE International Workshop on (2005), pp. 270-273.</i><br /><br />In general, a microstrip antenna has a narrow 3-dB AR bandwidth. Techniques for achieving wideband impedance and 3-dB AR bandwidth characteristics in the practical design of circular polarization (CP) antennas are important. This paper describes a method to enhance the AR bandwidth of a CP microstrip single-feed ring antenna (SFRA). The experimental results verify that the antenna has an impedance bandwidth of 34% and a 3-dB AR bandwidth of more than 33%. Enhancing AR bandwidth of circularly polarization microstrip antenna Dau-Chyrh Chang Huan-Cheng Lien Antenna Technology: Small Antennas and Novel Metamaterials, 2005. IWAT 2005. IEEE International Workshop on (2005), pp. 270-273. 2007-12-10T14:46:49-00:00 2005 Antenna Technology: Small Antennas and Novel Metamaterials, 2005. IWAT 2005. IEEE International Workshop on 270 273 antenna circularly microstrip patch polarisation http://www.citeulike.org/user/dcastro/article/2072422 <i>Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th, Vol. 2 (2004), pp. 989-993 Vol. 2.</i><br /><br />An increasing number of systems are adopting orthogonal frequency division multiple access (OFDMA) as their high-speed wireless transmission method supporting multiple users, and impacts on performance of OFDMA systems under mobile cellular environments are currently being investigated. In this paper, channel state and quality estimation performance issues are addressed for varying types of pilot structures in the transmitted burst. It is demonstrated that significant performance variations can occur in estimation of the state and quality of the wireless link depending on the pilot pattern used in the preamble symbol. In particular, advantages of using disjoint patterns for downlink transmission from adjacent cells are quantitatively presented, by evaluating the bit error rate and the carrier-to-interference ratio (CIR) estimation performance. Performance improvement of channel estimation based on pilot structure variations for cellular OFDMA systems Junghoon Lee Jaewon Chang Wonjin Sung Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th, Vol. 2 (2004), pp. 989-993 Vol. 2. 2007-12-07T10:20:40-00:00 2004 Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th 2 989 993 Vol. 2 channel estimation mobile ofdma performance pilot http://www.citeulike.org/user/dcastro/article/1026660 <i>Communications, 2006 IEEE International Conference on, Vol. 12 (2006), pp. 5595-5599.</i><br /><br />In the IEEE 802.16 network the SINR per subcarrier, the average SINR, and the SINR RMS are stochastic processes. In this paper, we analyze the statistical properties of these stochastic processes using system level simulation. We present the probability density functions for the SINR per subcarrier and the average SINR stochastic processes expressed in both logarithmic and linear scales. We also present the probability density function for the SINR RMS stochastic process, expressed in the logarithmic scale. The results, obtained in this paper, allow using the statistical approach while developing the adaptive transmission algorithms for the IEEE 802.16 network. Analysis of the Statistical Properties of the SINR in the IEEE 802.16 OFDMA Network SN Moiseev SA Filin MS Kondakov AV Garmonov Do Yim Jaeho Lee Sunny Chang Communications, 2006 IEEE International Conference on, Vol. 12 (2006), pp. 5595-5599. 2007-01-05T13:38:36-00:00 2006 Communications, 2006 IEEE International Conference on 12 5595 5599 80216 network ofdm sinr statistical http://www.citeulike.org/user/dcastro/article/1942324 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 41, No. 12. (1993), pp. 2116-2125.</i><br /><br />Novel uniplanar 180° and 190° hybrids suitable for MIC and MMIC applications are described. The uniplanar crossover hybrid-ring coupler using a coplanar waveguide (CPW) and slotline provides substantially improved amplitude and phase characteristics over a broad bandwidth compared to conventional microstrip hybrid-ring couplers. Experimental results show that the new coupler has a bandwidth of more than one octave from 2 GHz to 4 GHz with a ±0.4-dB power dividing balance and a ±1° phase balance. A uniplanar two-branch directional coupler using a coupled rectangular slotline ring has also been developed. CPW-to-slotline transitions using uniform and nonuniform CPWs or slotlines are also discussed. These transitions are uniplanar and simple to fabricate. No via-holes are needed for ground connections, and integration with solid-state devices is easy. A pair of broadband transitions using CPW shorts and slotline radial stubs is demonstrated with a 1-dB bandwidth of more than 5.2:1 Broad-band uniplanar hybrid-ring and branch-line couplers Chien-Hsun Ho Lu Fan Kai Chang Microwave Theory and Techniques, IEEE Transactions on, Vol. 41, No. 12. (1993), pp. 2116-2125. 2007-11-20T08:38:55-00:00 1993 Microwave Theory and Techniques, IEEE Transactions on 41 12 2116 2125 branch-line broadband coupler ratrace http://www.citeulike.org/user/dcastro/article/1898930 <i>Vehicular Technology Conference, 2000. IEEE VTS-Fall VTC 2000. 52nd, Vol. 4 (2000), pp. 1832-1835 vol.4.</i><br /><br />Orthogonal frequency division multiplexing (OFDM) is a possible candidate for high-rate data transmission in wireline and wireless communications. However, OFDM systems are very sensitive to frequency and timing offsets. The sensitivity causes the system performance to degrade drastically. Therefore, in this paper we propose a new estimation scheme for frequency and timing offsets in OFDM systems. This estimation is based on an ambiguity function. Simulation results show that frequency and timing offsets are estimated very accurately using our presented method A new estimation scheme for frequency and timing offsets in OFDM systems S Chang EJ Powers Vehicular Technology Conference, 2000. IEEE VTS-Fall VTC 2000. 52nd, Vol. 4 (2000), pp. 1832-1835 vol.4. 2007-11-11T15:24:34-00:00 2000 Vehicular Technology Conference, 2000. IEEE VTS-Fall VTC 2000. 52nd 4 1832 1835 vol.4 estimation frequency ofdm offset system time