CiteULike: dcastro's Liu

A novel metamaterial-inspired electrically small antenna fed by CPW

Meng Li — 2008-07-24T12:21:02-00:00

Microwave and Millimeter Wave Technology, 2008. ICMMT 2008. International Conference on, Vol. 4 (2008), pp. 1613-1616.

This article presents the design of an inexpensive, efficient, and electrically small antenna based on metamaterial- inspired structure fed by the coplanar waveguide (CPW). The size of the proposed antenna is 12 mm x 12 mm with the resonant frequency of 1.47 GHz. Details of the proposed antenna are presented, with full-wave simulation results to support the design.

The effect of nonlinearity on a QPSK-OFDM-QAM signal

Chia-Liang Liu — 2008-06-27T10:40:41-00:00

Consumer Electronics, IEEE Transactions on, Vol. 43, No. 3. (1997), pp. 443-447.

The effect of nonlinearity on a QPSK-OFDM-QAM signal is analyzed. One of the characteristics of an OFDM-QAM signal is its wide range of envelope fluctuation: its crest factor, defined as the ratio of the peak instantaneous power to the average (rms) power in dB, is typically greater than 10. When an OFDM-QAM signal drives a nonlinear device, nonlinearity will result in signal compression and intermodulation among the sub-carriers at the output. An analytical method is used to predict the input back-off needed to keep the intermodulation below an acceptable level. For sufficient large number of sub-carriers, we show that to keep the intermodulation power 30 dB below the signal power, we need to back-off the input power by 6.5 dB. However, from the BER point of view, the degradation is less than 2 dB at BER=0.01% even for 1 dB input back-off

Performance Analysis of GPS Receivers in Non-Gaussian Noise Incorporating Precorrelation Filter and Sampling Rate

L Liu — 2008-05-19T19:45:47-00:00

Signal Processing, IEEE Transactions on [see also Acoustics, Speech, and Signal Processing, IEEE Transactions on], Vol. 56, No. 3. (2008), pp. 990-1004.

<para> Global positioning system (GPS) receivers find growing applications in indoor and outdoor communication environments, including urban and rural areas. Interference and noise sources for GPS receivers may assume Gaussian or non-Gaussian distributions. The GPS receiver performance under Gaussian additive noise has been studied. Non-Gaussian noise may equally contaminate the GPS satellite signals and disturb the receiver delay lock loops (DLL), producing significant tracking errors. These sources include impulsive noise, ultra-wideband (UWB) signals, and impulse and noise radar signals for target tracking and indoor imaging applications. This paper considers non-Gaussian noise of finite variance and examines its effect on the discriminator outputs for the commercial GPS receiver that uses the coarse acquisition (C/A) code. The correlator noise output components are produced from the correlation between the noise sequence and the early, late, and punctual reference C/A code. Due to the long time averaging, which is characteristic of the GPS correlation loops, these components assume Gaussian distributions. The discriminator tracking error variance is derived, incorporating the effect of noise, the front-end precorrelation filter, and the sampling rate. </para>

Properties Of The Half-Normal Distribution And Its Application To Quality Control

Chao-Yu Chou — 2008-05-19T19:39:02-00:00

The Official Electronic Publication of the National Association of Industrial Technology (1998)

An efficient multiuser loading algorithm for OFDM-based broadband wireless systems

H Yin — 2008-05-19T18:32:45-00:00

Global Telecommunications Conference, 2000. GLOBECOM '00. IEEE, Vol. 1 (2000), pp. 103-107 vol.1.

In this paper we present a novel loading algorithm for OFDM-based multiuser communication system to maximize the total system throughput while satisfying the total power and users' rate constraints. The new scheme determines the subcarrier, bit, and power allocation by decoupling an NP-hard combinatorial problem into two steps: (1) resource allocation (how much power and how many subcarriers for each user) based on users' average channel gains and their rate requirements; and (2) subcarrier assignment and bit loading based on users' channel profiles across all subcarriers. Compared to existing iterative methods, the two-step approach offers comparable capacity gain with much lower complexity

Dipole with left handed loading with optimised efficiency

Qing Liu — 2008-05-18T14:13:40-00:00

Antennas and Propagation, 2007. EuCAP 2007. The Second European Conference on (2007), pp. 1-4.

Dipole loaded with left handed transmission lines allows operation with higher order mode current distributions and small size. Use in a meandered configuration can give polarisation orthogonal to the dipole length. In this paper a new printed implementation using distributed elements is proposed with improved efficiency. Comparisons are made between this antenna and previous antenna structures implemented with lumped and distributed elements, consisting of interdigitated capacitors and meandered line inductors. The simulated results show good input impedance match and radiation pattern typical of a dipole. This antenna also achieved an improved radiation efficiency of 73.84% and a gain of 0.809 dBi was obtained. Experimental results validate the performance of this antenna.

Double-ring active microstrip antenna and self-mixing oscillator in C-band

JC Liu — 2008-05-09T07:33:51-00:00

Microwaves, Antennas and Propagation, IEE Proceedings -, Vol. 147, No. 6. (2000), pp. 479-482.

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

Dual-mode double-ring resonators for microstrip band-pass-filter applications

JC Liu — 2008-05-09T07:26:03-00:00

Microwaves, Antennas and Propagation, IEE Proceedings -, Vol. 151, No. 5. (2004), pp. 430-434.

A novel design of a dual-mode resonator with a double-ring structure for band-pass filter applications is presented in this paper. Conventionally, dual-mode ring resonators are used to obtain band-pass filters. Based on voltage/current couplings, a dual-mode double-ring resonator was recently constructed to improve the responses of the conventional dual-mode ring resonator. In order to obtain a low insertion loss, a wide band and higher rejection, three filters using a dual-mode double-ring resonator are designed for 2.4 GHz ISM band applications.

Design of an LTCC tri-band transceiver module for GPRS mobile applications

Yo-Shen Lin — 2008-05-08T06:40:28-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 52, No. 12. (2004), pp. 2718-2724.

This paper presents the design and results of a low-temperature co-fired ceramic (LTCC) module for tri-band general packet radio service (GPRS) mobile applications. The proposed transceiver module integrates the tri-band (EGSM900/DCS1800/PCS1900) antenna switch, the surface-acoustic-wave filters for band selection, and a fully integrated tri-band transceiver integrated circuit into one LTCC package. By taking advantages of the three-dimensional layout capability of the LTCC substrate, the embedded circuit elements can be arranged vertically for size reduction. In addition, the utilization of mutual coupling leads to a novel design of miniature lumped-element realization of the transmission line. By combining these miniature passive component designs, the proposed module features a compact size of 13.8 mm /spl times/ 8.1 mm, with a packaged height of 1.8 mm. The module is compliant with the European Telecommunications Standards Institute regulations for GPRS mobile applications and is currently in use in commercially available mobile phones.

A novel microstrip diplexer design using defected ground structure

Haiwen Liu — 2008-05-08T06:28:47-00:00

Communications, Circuits and Systems, 2005. Proceedings. 2005 International Conference on, Vol. 2 (2005)

A simple microstrip diplexer using defected ground structure (DGS) is described in this letter. The diplexer has been designed, fabricated, and measured. Results show the new diplexer exhibits an isolation of greater than 26 dB between channels.

Broadband monolithic passive baluns and monolithic double-balanced mixer

Chen — 2008-05-06T18:33:19-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 39, No. 12. (1991), pp. 1980-1986.

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 IP<sub>3</sub> of this mixer is better than 15 dBm over the 4 to 5.75 GHz frequency band

Analysis and design of active antenna arrays

K Liu — 2008-05-06T17:42:47-00:00

Microwave Symposium Digest, 2001 IEEE MTT-S International, Vol. 2 (2001), pp. 1383-1386 vol.2.

In this paper, the FDTD method is extended successfully to analyze active antennas using Z-transform method for small signal model and by a stable scheme for large signal model. The two approaches are validated by comparison with analytical impedance expression in frequency domain. Through these approaches, we analyze active antennas and antenna arrays containing tunnel diodes. Effects of various device parameters are investigated in order to find desired oscillations. Single and array active antennas are designed and tested. Experimental and simulated results are given and compared

Optimum subcarrier assignment for OFDMA uplink

Zhongren Cao — 2008-04-22T13:02:16-00:00

Signals, Systems and Computers, 2003. Conference Record of the Thirty-Seventh Asilomar Conference on, Vol. 1 (2003), pp. 708-712 Vol.1.

Future broadband wireless communication requires the physical layer technology can be efficient in resource utilization, smooth in transition in a heterogenous system and suitable for future spectrum management policies. The interleaved subcarrier assignment is investigated in this paper. A scalable transmitter is proposed which is applicable in OFDM system as well as the interleaved OFDMA systems with various numbers of subcarriers. The frequency diversity of the interleaved OFDMA is compared with the sub-band based OFDMA.

Capacity improvement for uplink OFDMA

D Kivanc — 2008-04-22T11:27:45-00:00

Signals, Systems and Computers, 2002. Conference Record of the Thirty-Sixth Asilomar Conference on, Vol. 2 (2002), pp. 1809-1812 vol.2.

The combination of OFDM and FDMA, called OFDMA (orthogonal frequency division multiple access), is proposed for future communications systems. The paper studies the problem of receiver design in uplink communications in an OFDMA system. The aim is to provide a receiver design to support efficient resource allocation among multiple users. We look at blind subspace based estimation methods for synchronization and interference cancellation to improve the OFDMA uplink. The paper investigates the performance of the resulting receiver under the conditions of frequency offset and multipath fading. The issues of frequency offset synchronization as well as channel estimation are addressed.

Ultra-wideband for multiple access communications

RC Qiu — 2006-11-27T14:36:00-00:00

Communications Magazine, IEEE, Vol. 43, No. 2. (2005), pp. 80-87.

Ultra-wideband wireless communications techniques have many merits, including an extremely simple radio that inherently leads to low-cost design, large processing gain for robust operations in the presence of narrowband interference, covert operations, and fine time resolution for accurate position sensing. However, there are a number of challenges in UWB receiver design, such as capturing multipath energy, intersymbol interference especially in a non-line-of-sight environment, and the need for high-sampling-rate analog-to-digital converters. In this article, we provide a comprehensive review of UWB multiple access and modulation schemes, and their comparison with narrowband radios. We also outline the issues with UWB signal reception and detection, and explore various suboptimal low-complexity receiving schemes.

Subcarrier allocation and power control for OFDMA

D Kivanc — 2008-04-15T17:40:52-00:00

Signals, Systems and Computers, 2000. Conference Record of the Thirty-Fourth Asilomar Conference on, Vol. 1 (2000), pp. 147-151 vol.1.

We study the problem of finding an optimal subcarrier and power allocation strategy for downlink communication to multiple users in an OFDM based wireless system. We formulate the problem of minimizing total power consumption with constraints on BER and transmission rate for users requiring different classes of service, and derive simple algorithms which perform well. We divide the larger problem of joint allocation into two steps. In the first step, the number of subcarriers that each user is determined based on the users' average SNR. Numerical results demonstrate that the proposed low complexity algorithms offer comparable performance with an existing iterative algorithm

Full-wave analysis of coplanar waveguide and slotline using the time-domain finite-difference method

GC Liang — 2008-04-10T06:45:10-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 37, No. 12. (1989), pp. 1949-1957.

The authors present a detailed full-wave analysis of a coplanar waveguide (CPW) and a slotline by the time-domain finite-difference (TD-FD) method. The transient waveforms propagating along the coplanar waveguide and slotline, which are excited by retarded Gaussian pulses, are found in the time domain. After the time-domain field distributions are obtained, frequency-domain parameters such as the effective dielectric constant and the complex characteristic impedance are calculated using Fourier transformations. The results agree well with available theoretical and experimental data over a wide frequency range. The validity of the quasi-TEM assumptions for CPW and slotline analyses is also checked by evaluating the ratios of the longitudinal and transverse field components directly

Experimental and analytical studies on a high-resolution OFDM carrier frequency offset estimator

U Tureli — 2008-03-11T10:27:34-00:00

Vehicular Technology, IEEE Transactions on, Vol. 50, No. 2. (2001), pp. 629-643.

In orthogonal frequency-division multiplexing (OFDM) communications, carrier frequency offset must be estimated and compensated at the receiver to maintain orthogonality. In this paper, we examine the performance of a blind carrier frequency offset estimation algorithm for OFDM communications, Experiments were conducted on a system operating at close to 2 Mbits/s. Insights obtained from these experiments provided the motivation to explore the fundamental relationships between estimator performance and multiple system parameters such as the signal-to-noise ratio, number of data samples, frequency-selective fading, and power loading. We examine the sensitivity of the blind carrier frequency offset estimation algorithm using first-order perturbation analysis. In particular, we derive a closed-form expression for the mean square error of the carrier frequency offset estimator and present tradeoff studies for the high-resolution blind estimator performance. The analytical and simulation studies are in good agreement with experimental results

Implementing an OFDM receiver on the RaPiD reconfigurable architecture

C Ebeling — 2008-03-10T10:06:52-00:00

Computers, IEEE Transactions on, Vol. 53, No. 11. (2004), pp. 1436-1448.

Field-programmable gate arrays (FPGAs) have become an extremely popular implementation technology for custom hardware because they offer a combination of low cost and very fast turnaround. Because of their in-system reconfigurability, FPGAs have also been suggested as an efficient replacement for application-specific integrated circuits (ASICs) and digital signal processors (DSPs) for applications that require a combination of high performance, low cost, and flexibility. Unfortunately, the use of FPGAs in mobile embedded systems platforms is hampered by the very large overhead of FPGA-based architectures. Coarse-grained configurable architectures can reduce this overhead substantially by taking advantage of the application domain to specialize the reconfigurable architecture via coarse-grained components and interconnects. This paper presents the design and implementation of an OFDM receiver in the RaPiD reconfigurable architecture as a case study for comparing the relative cost and performance of ASIC, DSP, FPGA, and coarse-grained reconfigurable architectures. RaPiD is a coarse-grained reconfigurable architecture specialized to the domain of signal and image processing. The RaPiD architecture provides a reconfigurable pipelined datapath controlled by efficient reconfigurable control logic: We have implemented the computationally intensive parts of an OFDM receiver on the RaPiD architecture and have developed careful estimates of corresponding implementations in representative ASIC, DSP and FPGA technology. Our results show that, for this application, RaPiD fills the cost/performance gap between programmable DSP and ASIC architectures, achieving a factor of 6 better than a DSP implementation but a factor of 6 less than an ASIC implementation.

High accuracy frequency offset correction with adjustable acquisition range in OFDM systems

Zhongshan Zhang — 2008-02-25T15:40:02-00:00

Wireless Communications, IEEE Transactions on, Vol. 4, No. 1. (2005), pp. 228-237.

A new carrier frequency offset estimation scheme in orthogonal frequency-division multiplexing (OFDM) systems is proposed in this paper. Both the carrier frequency offset acquisition and tracking are based on a fixed-length training-symbol-block, which consists of multiple small identical training symbols. When each training symbol is shortened, the number of training symbols in the training-symbol-block should be increased accordingly to keep the total training-symbol-block length fixed. The proposed scheme extends Moose's estimator, where the estimation error is only dependent on total training symbol energy and cannot be reduced any more, once the total training symbol energy is determined. The proposed scheme can shorten each training symbol in a training-symbol block and select an appropriate estimator simultaneously, which can lead to further reduction of estimation error and increase of acquisition range, even with the total training-symbol-block energy being fixed. Performance analyzes for the proposed scheme in both the additive white Gaussian noise channel (AWGN) and the multipath channel are also presented in this paper. All estimators in the proposed scheme are conditionally unbiased, and simulation results demonstrate that they can work well both in the multipath channel and in the AWGN channel.

Joint frame synchronization and frequency offset estimation in OFDM systems

Zhongshan Zhang — 2008-02-25T15:27:23-00:00

Broadcasting, IEEE Transactions on, Vol. 51, No. 3. (2005), pp. 389-394.

A new joint frame synchronization and carrier frequency offset estimation scheme in orthogonal frequency division multiplexing (OFDM) systems is proposed in this paper, where both frame synchronization and carrier frequency offset estimation can be performed by using only ONE training symbol. Frame synchronization and carrier frequency offset acquisition are performed simultaneously in the proposed scheme. Reliable frame synchronization is obtained in the proposed scheme even in low SNR. The maximum carrier frequency offset acquisition range of the proposed scheme can be up to one half of the total signal bandwidth. The same training symbol can also be utilized to carrier frequency offset Fine Adjustment, which estimates the remaining carrier frequency offset after acquisition with higher accuracy. The performance comparison of the proposed Fine Adjustment algorithm and Schmidl's algorithm by using computer simulation illustrates and verify the superior performance of the proposed algorithm with regard to estimation accuracy.

A high-efficiency carrier estimator for OFDM communications

H Liu — 2008-02-25T15:24:35-00:00

Communications Letters, IEEE, Vol. 2, No. 4. (1998), pp. 104-106.

While multipath induced phase rotations can be dealt with by differential encoding in orthogonal frequency division multiplexing (OFDM) communications, the loss of orthogonality due to the carrier offset must be compensated before discrete Fourier transform (DFT)-based demodulation can be performed. In this letter, we present a high-performance/low-complexity blind carrier offset estimation algorithm by exploiting intrinsic structure information of OFDM signals. The algorithm offers the accuracy of a super resolution subspace method, viz. MUSIC, without involving computationally intensive subspace decompositions

Signal processing techniques in network-aided positioning: a survey of state-of-the-art positioning designs

Guolin Sun — 2007-01-08T07:26:34-00:00

Signal Processing Magazine, IEEE, Vol. 22, No. 4. (2005), pp. 12-23.

Wireless positioning has attracted much research attention and has become increasingly important in recent years. Wireless positioning has been found very useful for other applications besides E911 service, ranging from vehicle navigation and network optimization to resource management and automated billing. Although many positioning devices and services are currently available, it is necessary to develop an integrated and seamless positioning platform to provide a uniform solution for different network configurations. This article surveys the state-of-the-art positioning designs, focusing specifically on signal processing techniques in network-aided positioning. It serves as a tutorial for researchers and engineers interested in this rapidly growing field. It also provides new directions for future research for those who have been working in this field for many years.

Software radio architecture with smart antennas: a tutorial on algorithms and complexity

J Razavilar — 2008-02-09T01:17:47-00:00

Selected Areas in Communications, IEEE Journal on, Vol. 17, No. 4. (1999), pp. 662-676.

There has been considerable interest in using antenna arrays in wireless communication networks to increase the capacity and decrease the cochannel interference. Adaptive beamforming with smart antennas at the receiver increases the carrier-to-interference ratio (CIR) in a wireless link. This paper considers a wireless network with beamforming capabilities at the receiver which allows two or more transmitters to share the same channel to communicate with the base station. The concrete computational complexity and algorithm structure of a base station are considered in terms of a software radio system model, initially with an omnidirectional antenna. The software radio computational model is then expanded to characterize a network with smart antennas. The application of the software radio smart antenna is demonstrated through two examples. First, traffic improvement in a network with a smart antenna is considered, and the implementation of a hand-off algorithm in the software radio is presented. The blocking probabilities of the calls and total carried traffic in the system under different traffic policies are derived. The analytical and numerical results show that adaptive beamforming at the receiver reduces the probability of blocking and forced termination of the calls and increases the total carried traffic in the system. Then, a joint beamforming and power control algorithm is implemented in a software radio smart antenna in a CDMA network. This shows that, by using smart antennas, each user can transmit with much lower power, and therefore the system capacity increases significantly

Integrated laptop antennas - design and evaluation

Duixian Liu — 2007-12-07T10:18:11-00:00

Antennas and Propagation Society International Symposium, 2002. IEEE, Vol. 4 (2002), pp. 56-59 vol.4.

Two performance parameters are used to define integrated antennas for laptop applications. One is SWR, and another is the average antenna gain. Based upon link budget models and system requirements, the integrated antennas should have a 2:1 SWR bandwidth, wide enough to cover the 2.4 GHz ISM band to ensure a wireless system to have reliable, high data rate performance over a useful range or coverage area. The antenna should have average gain values similar to that of an isotropic radiator. The average gain value can be used in a communication link budget model to predict system level performance such as throughput and range. The antenna polarization is not a critical parameter for laptop applications since laptops are primarily used in indoor environment where there is high scattering and mixing of signals. As one would expect, the best location for integrated antennas in laptops is to place the antenna on the laptop display as high as possible. But using this location forces a design trade-off between the antenna's "visibility" and the necessity of a lossy feed cable, since wireless cards are usually placed in the base of a laptop. The ultimate system cost, time to market and performance are consciously traded off for each and every application.

Survey of Wireless Indoor Positioning Techniques and Systems

H Liu — 2007-12-06T16:49:43-00:00

Systems, Man and Cybernetics, Part C: Applications and Reviews, IEEE Transactions on, Vol. 37, No. 6. (2007), pp. 1067-1080.

<para> Wireless indoor positioning systems have become very popular in recent years. These systems have been successfully used in many applications such as asset tracking and inventory management. This paper provides an overview of the existing wireless indoor positioning solutions and attempts to classify different techniques and systems. Three typical location estimation schemes of triangulation, scene analysis, and proximity are analyzed. We also discuss location fingerprinting in detail since it is used in most current system or solutions. We then examine a set of properties by which location systems are evaluated, and apply this evaluation method to survey a number of existing systems. Comprehensive performance comparisons including accuracy, precision, complexity, scalability, robustness, and cost are presented. </para>

OFDM blind carrier offset estimation: ESPRIT

U Tureli — 2007-11-28T10:35:10-00:00

Communications, IEEE Transactions on, Vol. 48, No. 9. (2000), pp. 1459-1461.

In orthogonal frequency-division multiplex (OFDM) communications, the loss of orthogonality due to the carrier-frequency offset must be compensated before discrete Fourier transform-based demodulation can be performed. This paper proposes a new carrier offset estimation technique for OFDM communications over a frequency-selective fading channel. We exploit the intrinsic structure information of OFDM signals to derive a carrier offset estimator that offers the accuracy of a super resolution subspace method, ESPRIT

A broadband left-handed (LH) coupled-line backward coupler with arbitrary coupling level

C Caloz — 2007-11-26T20:28:44-00:00

Microwave Symposium Digest, 2003 IEEE MTT-S International, Vol. 1 (2003), pp. 317-320 vol.1.

A novel broadband left-handed (LH) coupled-line backward coupler with arbitrary coupling level is presented. This coupler is composed of two LH transmission lines (TL) constituted of series interdigital capacitors and shunt shorted-stub inductors. A quasi-0dB implementation of the coupler is demonstrated by simulation and measurement results, and shown to exhibit a bandwidth of 35% despite the relatively wide lines-gap of 0.3mm. An even/odd modes analysis is presented to explain the working principle of the component. A 3dB-quadrature implementation, with 37% bandwidth, is also demonstrated. Finally, parametric results illustrate the versatility of the LH coupler and its strongly enhanced backward coupling compared with the conventional coupled-line coupler.

Sequential Monte Carlo Methods for Dynamic Systems

Jun Liu — 2006-07-12T10:58:25-00:00

Journal of the American Statistical Association, Vol. 93, No. 443. (1998), pp. 1032-1044.

We provide a general framework for using Monte Carlo methods in dynamic systems and discuss its wide applications. Under this framework, several currently available techniques are studied and generalized to accommodate more complex features. All of these methods are partial combinations of three ingredients: importance sampling and resampling, rejection sampling, and Markov chain iterations. We provide guidelines on how they should be used and under what circumstance each method is most suitable. Through the analysis of differences and connections, we consolidate these methods into a generic algorithm by combining desirable features. In addition, we propose a general use of Rao-Blackwellization to improve performance. Examples from econometrics and engineering are presented to demonstrate the importance of Rao-Blackwellization and to compare different Monte Carlo procedures.

Carrier frequency offset estimation for OFDM-based WLANs

Jian Li — 2007-11-11T16:35:46-00:00

Signal Processing Letters, IEEE, Vol. 8, No. 3. (2001), pp. 80-82.

We present an efficient carrier frequency offset (CFO) estimation algorithm for the orthogonal frequency-division multiplexing (OFDM)-based wireless local area networks (WLANs). The packet preamble information we use is based on the high rate WLAN standards adopted by the IEEE 802.11 standardization group. Numerical results are presented to demonstrate the effectiveness of the proposed algorithm

Frequency offset estimation with fast acquisition in OFDM system

Zhongshan Zhang — 2007-11-11T15:43:57-00:00

Communications Letters, IEEE, Vol. 8, No. 3. (2004), pp. 171-173.

A new carrier frequency offset estimation scheme in orthogonal frequency-division multiplexing (OFDM) system is proposed. The carrier frequency offset estimation includes acquisition and tracking, and the acquisition range is as large as one half of overall signal bandwidth. The proposed tracking estimator is a maximum-likelihood estimator, and in AWGN channel, the Cramer-Rao lower bound is met at high signal-to-noise ratio (SNR); in multipath channel, the tracking algorithm works well at moderate SNR. Timing synchronization can be also performed during the course of acquisition.

Arbitrarily dual-band components using simplified structures of conventional CRLH TLs

Xian Lin — 2007-11-05T20:33:09-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 54, No. 7. (2006), pp. 2902-2909.

Microwave components with nonlinear phase responses are developed using a simplified composite right/left-handed (CRLH) transmission-line (TL) structure without the series capacitance or the shunt inductance. Using such a simplified CRLH structure, arbitrarily dual-band microstrip components have been realized in compact sizes such as a quarter-wavelength short-circuited stub and dual- band branch-line couplers. Simulation and measurement results are given to demonstrate the efficiency and good performance of the proposed components. For the quarter- wavelength short-circuited stub based on the simplified CRLH-TL structure without the series capacitance, it has been shown that the insertion loss is less than -0.1dB. For the arbitrarily dual-band branch-line coupler, experiment results exhibit that S/sub 21/ and S/sub 31/ are larger than -3.6dB, the isolations are smaller than -30dB, the return losses are smaller than -20dB, and the phase differences are within 90/spl deg//spl plusmn/1.8/spl deg/.

Compact Resonator Filters and Power Dividers Designed with Simplified Meta-Structures

Lin — 2007-09-16T04:23:41-00:00

Journal of Electromagnetic Waves and Applications, Vol. 21, No. 12. (2007), pp. 1663-1672.

Realization of arbitrary dual-band components using an improved CRLH transmission-line model

Xian Lin — 2007-11-02T17:41:40-00:00

Microwave Conference Proceedings, 2005. APMC 2005. Asia-Pacific Conference Proceedings, Vol. 1 (2005), 4 pp..

In this paper, new structures with nonlinear phase responses are proposed based on the composite right /left-handed (CRLH) transmission lines. Using such improved CRLH structure, arbitrary dual-band microstrip components have been realized, such as a quarter-wavelength open/short-circuited stub, and a dual-band branch-line coupler, etc. This has been demonstrated by both simulated and measured results. Compared to the conventional CRLH structures, the novel components are more compact and are easier to be realized.

A New Metamaterial Structure to Amplify Evanescent Waves and Its Applications in Microwave Components

Tie Cui — 2007-10-24T10:20:52-00:00

Antenna Technology: Small and Smart Antennas Metamaterials and Applications, 2007. IWAT '07. International Workshop on (2007), pp. 527-527.

Summary form only given. In this talk, we present a new structure to amplify the evanescent waves. The structure is composed of two layers. The first layer is realized by a periodic structure with unit cell of series inductor and shunt capacitor (LC), and the second layer is realized by a periodic structure with unit cell of series capacitor and shunt inductor (CL). We show that both the LC and CL structures are equivalent to the crystal bandgap metamaterials, whose equivalent permittivity and permeability have been derived. Under certain frequency bands, evanescent waves are supported in both LC and CL structures. When such two structures are cascaded together to form a bilayer, we show that evanescent waves existing in two single layers can be amplified exponentially if the resonant conditions are satisfied. Such resonant conditions are equivalent to the anti-matching conditions for the permittivity and permeability of the crystal bandgap metamaterials. We present circuit-simulation results of the LC and CL structures arid theoretical predictions of the equivalent crystal bandgap materials, which have excellent agreements. From the simulation results, we clearly observe the exponentially increasing and decreasing distribution of electric field. We further propose an experiment using lumped capacitors and inductors mounted on a printed circuit board to verify the EWA phenomena. The EWA feature in the LC-LC structure can find important applications in the new-concept microwave components, for example, the extremely-narrow band filters.