CiteULike: dcastro's receiver

Performance analysis of a stand-alone high-sensitivity receiver

Macgougan — 2008-07-24T11:47:54-00:00

GPS Solutions, Vol. 6, No. 3. (24 December 2002), pp. 179-195.

Abstract. The use of GPS for personal location using wireless devices requires satellite signal measurements both outdoors and indoors. In the outdoor environment propagation paths may range from line-of-sight to shaded or blocked. The indoor environment may range from single-floor wooden constructions to high-rise buildings and underground facilities. In this paper, a high-sensitivity receiver which operates in unaided stand-alone mode is tested under a range of shaded and blocked signal environments, ranging from residential outdoor areas to urban canyons and residential houses. The measurement analysis is performed in both the observation and position domains. The results show that the receiver tested is able to yield measurements with C/N0 degradations in excess of 20 dB-Hz, as compared to line-of-sight measurements. Position results are a function of the geometry of the remaining satellites, which in turn is a function of the environment.

Performance analysis of uncoded and coded OFDM broadband transmission over low voltage power-line channels with impulsive noise

P Amirshahi — 2008-07-10T07:12:37-00:00

Power Delivery, IEEE Transactions on, Vol. 21, No. 4. (2006), pp. 1927-1934.

Broadband communications for indoor power-line networks with impulsive noise using orthogonal frequency division multiplexing (OFDM) is considered. From earlier investigations, it is known that this channel suffers from multipath fading and frequency selectivity along with man-made impulsive bursty noise. Nevertheless, the calculated channel capacity limit promises very high data rates over this channel. Enhancement techniques, such as coding can help an OFDM system to tackle impulsive noise burst. In this paper, the bit error rate (BER) performance of the OFDM system under impulsive noise and frequency fading is theoretically analyzed and closed form expression for the performance is derived. Two different impulsive noise environment models are studied and it is confirmed that both models represent the same environment. Furthermore, a theoretical upper bound on the performance of coded OFDM system is obtained, given perfect interleaving. The effect of the interleaver length on coding performance is also studied. Simulations show that the upper bound is quite tight for the case of employing a longer interleaver. The effect of interleaver size on the system performance is studied, as well.

Performance Of A Convolutionally Coded Hard-decision Ds Receiver In Pulsed Noise Interference

J Juntti — 2008-07-10T07:12:35-00:00

Spread Spectrum on Techniques and applications, 1990., IEEE International Symposium on (1990), pp. 81-86.

Channel tracking for RAKE receivers in closely spaced multipath environments

G Fock — 2008-05-20T12:01:59-00:00

Selected Areas in Communications, IEEE Journal on, Vol. 19, No. 12. (2001), pp. 2420-2431.

This paper deals with the problem of channel tracking for RAKE receivers in propagation environments characterized by closely spaced multipath components. After outlining why conventional single-path channel tracking algorithms fail in such scenarios, several new estimation algorithms are developed that are tailored to channels with closely spaced multipaths. This is achieved by removing or minimizing self-interference caused by multipath components. Other interfering users are treated as noise. Both timing tracking and phasor tracking and their interaction are covered in this paper. The derived algorithms are benchmarked against perfect channel knowledge on one hand and conventional tracking algorithms on the other hand, both in a UMTS test scenario. In moderate scenarios, the use of these new algorithms leads to performance improvements of up to 2 dB, in terms of signal-to-noise ratio (SNR) at moderate bit error rates, and even manages to track the channel in conditions where conventional tracking algorithms fail completely

Noise standards, measurements, and receiver noise definitions

CKS Miller — 2008-06-24T12:41:07-00:00

Proceedings of the IEEE, Vol. 55, No. 6. (1967), pp. 865-877.

This paper consists of four sections covering 1) basic principles of noise measurement, 2) the switching radiometer, 3) a survey of noise sources, and 4) concepts of noise factor and noise temperature. The first section presents basic formulas used in analyzing radiometers. The second discusses the switching radiometer, briefly tracing its development and usage in the standards field. The third section surveys the development of hot and cold thermal noise sources, noise diodes, and gas-discharge noise generators. The last section presents and discusses the basic definitions of receiver noise performance.

Broadband transmission using OFDM: system performance and receiver complexity

M Speth — 2008-06-17T19:01:32-00:00

Broadband Communications, 1998. Accessing, Transmission, Networking. Proceedings. 1998 International Zurich Seminar on (1998), pp. 99-104.

This paper investigates the system performance of coherent OFDM transmission over frequency selective fading channels taking into account the constraints imposed by the receiver complexity. The effects of synchronization errors in the receiver are analyzed. In a properly designed inner receiver, these errors lead to extra noise. Specifying the limits for this additional noise allows one to derive the requirements for each component and thus to design and optimize the inner receiver independently from the outer receiver. The resulting receiver structure and the synchronization algorithms applied are introduced. Particular attention is paid to the channel estimation unit since its accuracy is most essential for system performance. A short analysis of the complexity of the algorithms allows one to determine the limits of the single components. System simulations including inner and outer receiver are used to evaluate the ideal vs. the realizable performance of the receiver and thus show how it is bounded by receiver complexity

GIOVE-A SIS Experimentation and Receiver Validation: Laboratory Activities at ESTEC

Massimiliano Spelat — 2008-06-13T06:47:47-00:00

Satellite Communications and Navigation Systems (2008), pp. 241-257.

The European Space Agency (ESA) and the Surrey Satellite Technology LTD (SSTL) have completed the on-orbit preparation and activated the payload of GIOVE-A, the first Galileo satellite launched last December, the 28th. After successful launch and platform commissioning achievement, GIOVE-A started signals transmission on 12 January 2006. For the time being the quality of the signal broadcast by GIOVE-A is under examination by mean of sophisticated equipments and facilities, including the ESA ground station in Redu (Belgium) and the Rutherford Appleton Laboratory (RAL) Chilbolton Observatory in the United Kingdom. It is clear that the European Galileo satellite navigation system is moving into a crucial phase concerning the development process; therefore the possibility of testing and validating hardware/software tools (e.g. user receivers) will play a key role from the manufacturers point of view. In this context the navigation laboratory at ESA's European Space Research and Technology Centre (ESTEC), in the Netherlands, could be considered relevant in the receivers validation procedures, as well as in the Signal-In-Space (SIS) experimentation activity, where the GSTB-v2 Experimental Test Receiver (GETR) plays a key role. The paper will provide the overview of the set-up available in the navigation laboratory at ESTEC, describing the equipments composing the test bench. The Galileo Signal Validation Facility (GSVF-v2) will be presented pointing out the capabilities in the Galileo-like signal generation. In particular, the Galileo L1 Open Service (OS) signal will be analyzed, and the corresponding GETR tracking performance will be presented in terms of code tracking noise curves, autocorrelation function and multipath envelope. Tracking performance for the Galileo L1 OS signal in multipath environments will be evaluated in terms of static and dynamic contributions. Finally, some screenshots of the GETR graphical user interface (while tracking GIOVE-A signals) will also be included in the paper, as the prove that the entire set-up has been fully integrated with the Space Engineering's Galileo antenna for the reception and process of live GIOVE-A signals.

A modular architecture for the real-time reconfigurability of GNSS receivers

F Dovis — 2008-06-11T20:26:39-00:00

Electronics in Marine, 2004. Proceedings Elmar 2004. 46th International Symposium (2004), pp. 336-341.

The increased interest for the design of applications based on both navigation and communication systems, represents an important driver for the design and implementation of innovative receivers architectures. The realization of civil GPS applications, the advent of the European navigation system Galileo, and the integration of localization services in communication network, make the reconfigurability an indispensible requirement for the development of innovative Global Navigation Satellite systems (GNSS) platforms. In addition, it must be pointed out that several problem as indoor positioning and multipath recovery, are pushing the research activity in order to provide users of flexible devices able to adapt their functionalities according to the environment. From this standpoint, the Software Defined Radio (SDR) approach constitutes an interesting perspective to develop modular architectures. In this paper, the implementation of a reconfigurable user terminal integrating both navigation and communication capabilities will be discussed. The work will be presented focusing the attention on the real-time reconfigurability, based on a set of software-designed functionalities. In particular, the reconfigurable module for multipath mitigation in the tracking phase will be discussed as an example of adaptability of the receiver to the operating environment.

Practical Review of Advanced CDMA Receivers with Emphasis in the Downlink

Panayiotis Papadimitriou — 2008-06-05T06:43:49-00:00

In this paper, we will review the scientific literature on the advanced cdma receivers. Special emphasis will be given towards receivers applicable to the cdma downlink (base-station to mobile link), and the presentation will be given from the perspective of the modem design engineer to the extent the limited paper space allows.

An open baseband processing architecture for future mobile terminal design [accepted from open call]

WW Lu — 2008-06-03T19:01:30-00:00

Wireless Communications, IEEE [see also IEEE Personal Communications], Vol. 15, No. 2. (2008), pp. 110-119.

Optimum Performance of Suppressed Carrier Receivers with Costas Loop Tracking

M Simon — 2008-05-21T12:54:41-00:00

Communications, IEEE Transactions on [legacy, pre - 1988], Vol. 25, No. 2. (1977), pp. 215-227.

The performance of suppressed carrier receivers with Costas loop tracking is optimized by proper choice of loop arm filter bandwidth. In particular, it is shown that for a variety of passive arm filter types, there exists, for a given data rate and data signal-signal-to-noise ratio, an optimum filter bandwidth in the sense of minimizing the loop's squaring loss. For the linear theory case, this is equivalent to minimizing the loop's tracking jitter. When symbol synchronization is known, it is shown that by replacing the passive arm filters with active filters, i.e., integrate-and-dump circuits, one can acheive an improvement in carrier-to-noise ratio of as much as 4 to 6 dB depending on the passive arm filter type used for comparison and the value of data signal-to-noise ratio.

Receiver implementation for a MIMO OFDM system

AN Mody — 2008-05-21T09:33:28-00:00

Global Telecommunications Conference, 2002. GLOBECOM '02. IEEE, Vol. 1 (2002), pp. 716-720 vol.1.

We present preamble and receiver design for a Q transmit L receive multi-input multi-output OFDM system. Tasks performed by the receiver are synchronization in time and frequency domains, followed by channel estimation and noise variance estimation. An algorithm is developed such that only Q OFDM symbols of a generalized length are required to perform functions of the preamble. Coarse time synchronization is performed using inherent periodicity in the preamble. Frequency offset estimation is then performed in the time domain, followed by residual frequency offset estimation in the frequency domain followed by fine time synchronization. The channel estimation algorithm is developed using least squares principle. Simulations are carried out for a broadband fixed wireless access scenario using a preamble with and without zero-padding of tones in the frequency domain.

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>

A High Bandwidth GPS L1/L2 C/A Code Software Receiver For Real Time Kinematic Positioning

Thomas Pany — 2008-05-19T18:51:49-00:00

Design and Validation of Digital Channels for a Galileo Receiver Prototype

F Rossi — 2008-05-18T14:17:34-00:00

Digital System Design: Architectures, Methods and Tools, 2006. DSD 2006. 9th EUROMICRO Conference on (2006), pp. 545-549.

This paper describes the design activity for the digital baseband processing of a prototype receiver for the Galileo system. According to the applied hardware-software partitioning, the high rate elaborations have been implemented on a dedicated hardware, a Xilinx Virtex2 FPGA, while the remaining low rate processing has been programmed on an analog device DSP. A customarily designed prototype board has been used to validate the receiver under real working conditions: a dynamic GPS and Galileo scenario. Particularly, the paper focuses on the receiver digital channel, which is the critical core of the FPGA, from VHDL modeling to hardware implementation and testing

GPS receiver search techniques

PW Ward — 2008-05-18T14:07:47-00:00

Position Location and Navigation Symposium, 1996., IEEE 1996 (1996), pp. 604-611.

GPS receivers must perform a two-dimensional sequential search process for the GPS signals. The two-dimensional search pattern consists of discrete search cells with each cell representing one code bin and one carrier Doppler bin. The code bin width is usually ½-half chip. The longer the dwell time per binary decision (the predetection integration time), the narrower the Doppler bin width and weaker GPS signals can be acquired, but the search time increases. The replica C/A-code generates larger than normal sidelobes if the Doppler bin is too wide (when predetection integration time is too short), False acquisition of the sidelobes can occur if the search threshold is set too low. At the heart of the receiver search process is the search detector. There are significant performance differences between search detector algorithms. This paper describes, analyzes and compares two powerful sequential search algorithms: the fixed-dwell-time M-of-N detector and the variable dwell time Tong detector (1973)

The Acquisition Process of a Maximum Likelihood GPS Receiver

Progri — 2008-05-18T12:45:37-00:00

Proc. Institute of Navigation GPS 2003 (2003)

Performance Assessment of the TurboDLL for Satellite Navigation Receivers

Fabio Dovis — 2008-05-16T14:53:41-00:00

Satellite Communications and Navigation Systems (2008), pp. 273-282.

In this paper a detailed evaluation of the performance of the architecture named “Turbo Delay Lock Loop” (TurboDLL) is presented. Such an architecture has been introduced by the authors in [1], as an innovative solution for improving the performance of satellite navigation receivers in multipath affected scenarios. The relevant innovation resides in the fact that the architecture aims at tracking each multipath component and, after a transient time, use them to wipe the multipath components off the input signal. The iterative procedure allows for a major improvement in the error induced in the code-based pseudorange measurement. The architecture uses a preliminary estimation of the propagation channel in terms of number of not negligible reflections, and of their relative amplitude. In this paper the robustness of the TurboDLL architecture with respect to imperfect channel estimation is demonstrated.

A noncoherent sequential PN code acquisition scheme in DS/SS receivers

Jia-Chin Lin — 2008-05-16T11:35:46-00:00

Global Telecommunications Conference, 1998. GLOBECOM 98. The Bridge to Global Integration. IEEE, Vol. 4 (1998), pp. 2168-2173 vol.4.

A noncoherent sequential PN code acquisition technique is proposed. Noncoherent detection is employed to handle the seriously noisy environments, while the carrier frequency offset and data modulation effects can be simultaneously taken care of. To realize the sequential acquisition, the out-of-phase and in-phase sequences are properly modeled to avoid the significantly high error probabilities caused by the conventional widely used zero sequence model. Extensive computer simulation results indicated that the proposed PN code acquisition outperforms the fixed-dwell-time counterparts by roughly 2-6 dB with much lower false alarm and miss probabilities, and the superiority of the proposed technique becomes more significant at lower SNR conditions

C-band direct conversion receiver front-end using a resistive FET mixer

S Lin — 2008-05-15T12:09:03-00:00

Microwave Symposium Digest, 1999 IEEE MTT-S International, Vol. 4 (1999), pp. 1409-1411 vol.4.

A C-band direct conversion receiver front-end based on a resistive FET mixer has been developed. Resistive FET mixers, as opposed to other configurations, require only gate bias and no drain bias. Thus the baseband signal can be easily filtered from the drain terminal. The resistive FET mixer is integrated with rectangular microstrip patch antenna, yielding a compact receiver front-end. A prototype was constructed and demonstrated satisfactory demodulation of a BPSK modulated RF signal

Galileo receivers - challenges and performance

M Hollreiser — 2008-05-13T10:06:32-00:00

Microwave Conference, 2004. 34th European, Vol. 1 (2004), pp. 321-324.

Performance Analysis and Parameter Optimization of DLL and MEDLL in Fading Multipath Environments for Next Generation Navigation Receivers

M Sanchez-Fernandez — 2008-05-10T00:01:43-00:00

Consumer Electronics, IEEE Transactions on, Vol. 53, No. 4. (2007), pp. 1302-1308.

In this paper the choice of DLL parameters is studied with special focus on multipath and Doppler sensitivity. The envisaged application is code tracking on navigation receivers and the multipath fading environments defined for next generation navigation systems are considered. Given the particular properties of these propagation environments, multipath estimating delay lock loop is shown to have the best performance within a particular signal to noise ratio range if some specific parameters such as the Predetection Integration Time and channel estimation time interval match the time-varying nature of the channel and the spacing in the early-late scheme is chosen accordingly to the multipath characteristics.

Compact low noise receiving antenna

TD Ormiston — 2008-05-09T23:43:01-00:00

Electronics Letters, Vol. 34, No. 14. (1998), pp. 1367-1368.

The authors report a novel active integrated receiving antenna providing between 12 and 24 dB gain when referred to a passive equivalent at 1.335 GHz. The antenna is of a compact coplanar form, integrating DC and RF requirements to obtain both high gain and low noise

A novel scheme for reception using an active microstrip antenna

BN Biswas — 2008-05-09T06:44:41-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 48, No. 10. (2000), pp. 1765-1768.

An unique aspect of the injection-locked active microstrip antenna incorporating a Gunn diode, i.e., the variation of the device current within the lock band, is exploited for the demodulation of an FM microwave signal. A simple experimental arrangement has been presented to demonstrate the demodulation performance of the receiver even in a multichannel environment. Using two such separate antennas as transmitter and receiver, a two-way short-range communication system has been demonstrated that may be suited for certain commercial and military applications

A transmit/receive active antenna with fast low-power optical switching

J Vian — 2008-05-09T06:44:38-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 48, No. 12. (2000), pp. 2686-2691.

This paper presents an optically switched X-band active antenna element for half-duplex transmit/receive (T/R) applications. The antenna element is designed to be a unit cell of a quasioptical array with fast switching between T and R and with built-in phase-shifterless beamforming. The measured performance of the active element is 14 dB gain contributed by the power amplifier (PA) in transmission and 16 dB gain contributed by the low-noise amplifier in reception, with 30 dB isolation between T and R. The switching is accomplished with only 1 μW of optical power for 1.7 μs switching time (1.7 pJ of optical energy) and a rise time of 2 ns at 10 GHz with 7 mW of optical power (14 pJ of optical energy). The design, implementation, and measured performance of the optically controlled transmit/receive circuit are presented

Fading Channel Models for the Assessment of GNSS Receivers

R Prieto-Cerdeira — 2008-05-08T08:45:14-00:00

Antennas and Propagation, 2007. EuCAP 2007. The Second European Conference on (2007), pp. 1-5.

Applications based on Global Navigation Satellite System (GNSS) positioning for difficult environments, such as indoor, the urban canyon or low Earth orbiting satellites, have become very attractive in recent years. For a rigorous assessment of receiver performances in controlled laboratory conditions with respect to their objective environment, a precise knowledge of the electromagnetic radio channel is required. Different propagation mechanisms (diffraction, reflection and scattering) are combined together originating signal variations that affect receiver performance. Shadowing and blockage due to obstacles, frequency selective fading due to multipath, large building penetration losses or strong fading due to ionospheric scintillation are some examples of the impairments that GNSS receivers may encounter. In this paper, fading channel models that generate time-series are analysed for establishing procedures to assess the performance of GNSS receivers in different environments by, first setting error bounds in software implementations, and later, using RF signal simulators.

Real-time acquisition and tracking for GPS receivers

A Alaqeeli — 2008-05-07T06:24:49-00:00

Circuits and Systems, 2003. ISCAS '03. Proceedings of the 2003 International Symposium on, Vol. 4 (2003), pp. IV-500-IV-503 vol.4.

Current GPS receivers spend much time in base-band processing, performing acquisition and tracking. This is due to the large number of required operations in the software-based signal processing. This paper presents a novel signal acquisition and tracking method that reduces the number of operations, simplifies hardware implementation and decreases the acquisition time. The implementation of this method in an FPGA provides very fast processing of incoming GPS samples that satisfies real-time requirements.

Active quasi-Yagi antenna direct conversion receiver array with digital beamforming

SS Jeon — 2008-05-06T18:30:54-00:00

Antennas and Propagation Society International Symposium, 2000. IEEE, Vol. 3 (2000), pp. 1268-1271 vol.3.

A four-element array single card receiver for indoor wireless applications at C-band is presented. A broadband quasi-Yagi antenna is adopted as the antenna array element due to its broad beamwidth and low mutual coupling characteristics. The integrated receiver circuit uses a multilayer architecture, where RF and baseband circuits are placed above and below the antenna substrate, resulting in a very compact design. Using digital signal processing, the array element patterns are calculated from the four-channel amplitude and phase information of the baseband outputs. An initial test of the integrated receiver shows a scanning range of 70°, without the use of any adaptive algorithm

A low noise active integrated antenna receiver for monopulse radar applications

S Lin — 2008-05-06T18:30:51-00:00

Microwave Symposium Digest, 2001 IEEE MTT-S International, Vol. 2 (2001), pp. 1395-1398 vol.2.

A low noise active integrated antenna receiver is presented. This new design consists of a pair of low noise amplifiers (LNA) integrated on each feed of a dual-feed planar quasi-Yagi antenna. The outputs of the LNAs are combined to form a sum and difference radiation pattern suitable for monopulse radar applications. Simulation and measurement methodology for designing a low noise active integrated antenna receiver is also presented. A peak gain of 7.7 dB and minimum noise figure of 3.6 dB is measured for a C-band prototype

Advanced and intelligent RF front end technology

KMKH Leong — 2008-05-06T17:15:56-00:00

Wireless Communication Technology, 2003. IEEE Topical Conference on (2003), pp. 190-193.

This paper discusses the recent developments by the author's group in the field of RF front-end technology. This includes standalone RF front-end components such as a self-heterodyne mixer as well as more functional front-end circuitry such as digital and analog beamformers.

A PC-based software receiver using a novel front-end technology

M Laddomada — 2008-05-05T14:19:02-00:00

Communications Magazine, IEEE, Vol. 39, No. 8. (2001), pp. 136-145.

Since the software radio concept was introduced, much progress has been made in the past few years in making it a reality. Many software radio based systems have been designed through the development efforts of both commercial and noncommercial organizations. While the term software radio has meant many things, the ultimate goal in software radio has been the realization of an agile radio that can transmit and receive signals at any carrier frequency using any protocol, all of which can be reprogrammed virtually instantaneously. Such a system places great demands on the limits of data converter and processor technologies since it requires real-time disposition of gigasamples of data produced by direct conversion of wireless signals into digital data. From a processing standpoint, the challenge in software radio is to exploit the three basic processor types-fixed architecture processors, FPGAs, and programmable DSPs/RISCs/CISCs-in such a way as to optimize the three-way trade-offs between speed, power dissipation, and programmability. With respect to the latter characteristic, the issues of high-level language interfaces, portability, and reprogramming speed must be considered. This article describes the architecture and operation of a PC-based software radio receiver. The development environment is a real-time PC-based platform that allows testing to be done in a simple manner using the main software functionality of a PC. The front-end of the receiver implemented in hardware represents a novel wideband design (bandwidth of up to 100 MHz centered at a carrier frequency of up to 2 GHz) that functionally converts wireless signals directly into a gigasample digital data stream in the receiver (and vice versa in the transmitter). This direct conversion approach shows the greatest promise in realizing the main goal of software radio

Impedance matching in active integrated antenna receiver front end design

AS Andrenko — 2008-05-05T08:07:18-00:00

Microwave and Guided Wave Letters, IEEE [see also IEEE Microwave and Wireless Components Letters], Vol. 10, No. 1. (2000), pp. 16-18.

The active integrated antenna (AIA) concept has been realized in the design of integrated amplifier front end, which enables its applications in novel adaptive antenna systems. To address the problem of mismatch between antenna element and amplifier, we present the matching renditions of both gain impedance and noise figure minimum impedance. In addition, the application of these principles is demonstrated in the design of ultra-compact helical AIA receiver front end for operation at 2.1 GHz. Amplifier simulation and measurements have been carried out to confirm the design procedure. It is shown that the proposed configuration can be successfully used in novel wireless handsets

Active patch antennas integrated with Rx/Tx front end

D Radulovic — 2008-05-05T08:05:26-00:00

Telecommunications in Modern Satellite, Cable and Broadcasting Service, 2003. TELSIKS 2003. 6th International Conference on, Vol. 1 (2003), pp. 49-52 vol.1.

In this paper is described one method for variation of impedance of patch antennas. With this method both phase and magnitude of impedance can be varied in wide range of different values. This gives us possibility of integration of antenna with variety of different active microwave semiconductors. First of all we described method and its characteristics such as values of patch impedance, which can be attained, and later we demonstrated application of method in case of patch antenna integrated with low noise amplifier (LNA) in receiver.

A design for OFDMA receiver

Jianhua Zhang — 2008-04-23T18:38:14-00:00

Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st, Vol. 2 (2005), pp. 1268-1272 Vol. 2.

In this paper, a design for OFDMA receiver is given. Timing synchronization is achieved by ML algorithm with Gold sequence and then multipath delay estimate is achieved by the correlation operation between the local training sequence and the sampled received signal. In order to decrease the overhead for channel estimation, multiple users are combined as a group to share the pilot subcarriers and Walsh codes are used as pilots for different users. For such user group, LS algorithm with the forward estimated delay is adopted to estimate the channels of users. The simulation results show that this receiver can achieve the timing synchronization, multipath delay estimate at low SNR and good BER performance with accurate channel estimation.

Multiuser interference cancellation receivers for OFDMA uplink communications with carrier frequency offset

R Fantacci — 2008-04-23T18:20:57-00:00

Global Telecommunications Conference, 2004. GLOBECOM '04. IEEE, Vol. 5 (2004), pp. 2808-2812 Vol.5.

In multiple access OFDM systems (OFDMA) the separation of different users is achieved by exploiting the orthogonality of the subcarriers. However, a well-known problem in OFDM-based systems is the vulnerability to synchronization errors which leads to a loss of orthogonality. In this paper, a method is proposed to counteract the effect of different frequency offsets among users in an OFDMA uplink system with a frequency selective Rayleigh fading channel. The multiple access interference due to the user frequency misalignments is reduced by reconstructing and removing the interfering signals in the frequency domain. This is performed by means of a successive or selective cancellation method. In particular, the performance of these cancellation schemes is analyzed by assuming either an ideal or estimated frequency offset. Simulation results show that it is possible to achieve, with the interference cancellation, a performance close to the ideal case, i.e., without frequency offset among users.

Analysis of two receiver schemes for interleaved OFDMA uplink

Zhongren Cao — 2008-04-22T13:01:47-00:00

Signals, Systems and Computers, 2002. Conference Record of the Thirty-Sixth Asilomar Conference on, Vol. 2 (2002), pp. 1818-1821 vol.2.

In the uplink of OFDMA (orthogonal frequency division multiple access, a combination of OFDM and FDMA), the interleaved carrier assignment scheme is preferred for its maximum frequency diversity. Two receiver schemes are presented. The first is a group synchronization scheme, in which the uplink receiver compensates the effect of carrier frequency offsets and tries to recover the synchronized spectrum of one OFDMA block. The other one, a user separation scheme, exploits the signal's algebraic structure on the uplink of the interleaved OFDMA system, by which the signal waveform of each single user is separated and synchronized at the same time. We present the algorithms for each scheme and analyze their performance in terms of signal-to-interference-plus-noise ratio and residual interference.

Broadband powerr amplifier distortion cancellation with model estimation inthe receiver

Fernando Gregorio — 2008-04-23T17:41:26-00:00

Signal Processing Advances in Wireless Communications, 2007. SPAWC 2007. IEEE 8th Workshop on (2007), pp. 1-5.

This paper proposes a practical receiver cancellation technique for removing nonlinear power amplifier (PA) distortion in OFDM systems. By performing the estimation of the PA model parameters at the receiver, the implementation complexity of the transmitter can be reduced. Furthermore, a simple adaptation rule is provided to enable tracking of the PA model parameters. As a consequence, cancellation of nonlinear distortion can be achieved without assuming that the PA model is known a priori at the receiver. Simulation results show that good levels of distortion cancellation are possible for a system with a broadband PA with memory.

A novel iterative receiver for uplink OFDMA

Man-On Pun — 2008-04-22T11:27:43-00:00

Global Telecommunications Conference, 2005. GLOBECOM '05. IEEE, Vol. 5 (2005), 5 pp..

In this work we consider the uplink of an OFDMA system and present a novel receiver that performs joint frequency offset acquisition, channel estimation and data detection for each active user. The proposed receiver can be used with any subcarrier assignment scheme, and it operates in an iterative fashion. Users' separation is accomplished at the base station through space-alternating generalized-expectation (SAGE) techniques. Each separated user's signal is then passed to an expectation-conditional maximization (ECM)-based processor that jointly performs frequency acquisition, channel estimation and data detection at each iteration. Compared to conventional OFDMA systems, the proposed receiver allows significant reduction of the synchronization overhead as it dispenses from the need of returning estimated frequency offsets back to active users for frequency adjustment. Simulations indicate that the proposed scheme provides accurate data detection for unsynchronized OFDMA uplink transmissions over doubly-selective fading channels.

Noise Figures of Radio Receivers

HT Friis — 2008-04-15T18:17:28-00:00

Proceedings of the IRE, Vol. 32, No. 7. (1944), pp. 419-422.

A rigorous definition of the noise figure of radio receivers is given in this paper. The definition is not limited to high-gain receivers, but can be applied to four-terminal networks in general. An analysis is made of the relationship between the noise figure of the receiver as a whole and the noise figures of its components. Mismatch relations between the components of the receiver and methods of measurements of noise figures are discussed briefly.

A Receiver Architecture for Dual-Antenna Systems

H Rafati — 2008-03-27T08:23:01-00:00

Solid-State Circuits, IEEE Journal of, Vol. 42, No. 6. (2007), pp. 1291-1299.

<para> The signals received by two antennas can be processed by a single time-shared receiver but only in the absence of interferers and channel-select filters. A low-IF receiver architecture is introduced that translates two antenna signals to positive and negative frequencies in the complex domain, reducing the number of baseband A/D converters by a factor of two. A dual-receiver prototype designed and fabricated in 0.18-<formula formulatype="inline"><tex>$mu$</tex></formula>m CMOS technology provides a sensitivity of <formula formulatype="inline"><tex>$-72$</tex> </formula> dBm with an EVM of <formula formulatype="inline"><tex>$-25$</tex> </formula> dB for 64 QAM signals while drawing 60.2 mW from a 1.8-V supply. </para>

Radio astronomy receivers

M Tiuri — 2008-03-14T10:01:27-00:00

Antennas and Propagation, IEEE Transactions on [legacy, pre - 1988], Vol. 12, No. 7. (1964), pp. 930-938.

A general survey of the principles of radio astronomy receivers is presented. System noise temperature, the sensitivity of different receiver types, and the calibration of receivers are studied. A total-power receiver is analyzed as a basic radio telescope receiver and the results are used to obtain the performance of other receiver types such as the Dicke receiver, Graham's receiver, correlation receiver, and phase-switching receiver.

WiMAX/WLAN radio receiver architecture for convergence in WMANS

BJ Farahani — 2008-03-11T10:30:31-00:00

Circuits and Systems, 2005. 48th Midwest Symposium on (2005), pp. 1621-1624 Vol. 2.

The trend toward increasing the data rate and providing the customers with wireless broadband access has initiated WIMAX systems. IEEE 802.16e, the mobile version of IEEE 802.16, provides WMAN (wireless metropolitan area network). Such system would need to work in the hostile environment of cellular phones and hence has the tough blocker requirements of GSM while providing the quality of service of WLAN (IEEE 802.11a/g). Combination of these factors imposes stringent requirements on system and block level. Convergence of WiMAX and WLAN facilitates the broadband accessibility by using the already existing wireless networks wherever there is a WLAN hot spot. This paper proposes a fully integrated solution for a multiband WIMAX/WLAN system based on a zero-IF architecture. System requirements are analyzed and block level specifications are derived. Challenges in system and block level are discussed and solutions are offered based on the current sub-micron CMOS technologies.

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.

On the baseband compensation of IQ imbalances in OFDM systems

A Tarighat — 2008-02-26T19:58:18-00:00

Acoustics, Speech, and Signal Processing, 2004. Proceedings. (ICASSP '04). IEEE International Conference on, Vol. 4 (2004), pp. iv-1021-4 vol.4.

OFDM is a widely recognized and standardized modulation scheme for future high bit rate communications. Implementation of OFDM-based systems suffers from inphase-quadrature phase (IQ) imbalances in the front-end analog processing. The IQ imbalances can severely limit the operating SNR and, consequently, the supported constellation sizes. In this paper, the effect of IQ imbalances on OFDM receivers is analyzed and system level algorithms to compensate for these distortions are proposed. The algorithms include different post and pre-FFT estimation and correction techniques.

Optimum receiver design for wireless broad-band systems using OFDM. I

M Speth — 2008-02-25T15:39:04-00:00

Communications, IEEE Transactions on, Vol. 47, No. 11. (1999), pp. 1668-1677.

Orthogonal frequency-division multiplexing (OFDM) is the technique of choice in digital broad-band applications that must cope with highly dispersive transmission media at low receiver implementation cost. In this paper, we focus on the inner OFDM receiver and its functions necessary to demodulate the received signal and deliver soft information to the outer receiver for decoding. The effects of relevant nonideal transmission conditions are thoroughly analyzed: imperfect channel estimation, symbol frame offset, carrier and sampling clock frequency offset, time-selective fading, and critical analog components. Through an appropriate optimization criterion (signal-to-noise ratio loss), minimum requirements on each receiver synchronization function are systematically derived. An equivalent signal model encompassing the effects of all relevant imperfections is then formulated in a generalized framework. The paper concludes with an outline of synchronization strategies

Robust OFDM receivers for dispersive time-varying channels: equalization and channel acquisition

A Gorokhov — 2008-02-25T15:33:52-00:00

Communications, IEEE Transactions on, Vol. 52, No. 4. (2004), pp. 572-583.

In orthogonal frequency-division multiplexing, time variations of a multipath channel lead to a loss of orthogonality between the subcarriers, and thereby limit the achievable throughput. This paper proposes a general framework for a controlled removal of intercarrier interference (ICI) and channel acquisition. The core idea behind our method is to use a finite power series expansion for the time-varying frequency response, along with the known statistical properties of mobile radio channels. Channel acquisition and ICI removal are accomplished in the frequency domain and allow for any desired tradeoff between the residual ICI level, the required training for channel acquisition, and processing complexity. The proposed approach enables a high spectral efficiency (64-quadrature amplitude modulation mode) of digital video broadcasting-terrestrial in highly mobile environments.

Optimum receiver design for OFDM-based broadband transmission .II. A case study

M Speth — 2008-02-25T15:14:45-00:00

Communications, IEEE Transactions on, Vol. 49, No. 4. (2001), pp. 571-578.

This paper details on the design of OFDM receivers. Special attention is paid to the OFDM-specific receiver functions necessary to demodulate the received signal and deliver soft information to the outer receiver for decoding. In part I of the paper, the effects of nonideal transmission conditions have been thoroughly analyzed. To show the impact of the synchronization algorithms-which are most critical in OFDM-on system performance and complexity we consider the design of a complete receiver consisting of symbol synchronization, carrier/sampling clock synchronization and channel estimation. The performance of the algorithms is analyzed and a qualitative estimate of the resulting complexity is given. This allows one to draw conclusions concerning the achievable system performance under realistic complexity assumptions

A Unified Approach to Serial Search Spread-Spectrum Code Acquisition--Part II: A Matched-Filter Receiver

A Polydoros — 2008-02-25T15:11:03-00:00

Communications, IEEE Transactions on [legacy, pre - 1988], Vol. 32, No. 5. (1984), pp. 550-560.

The unified theory developed in Part I [1] is employed here in the analysis of a noncoherent, matched-filter (fast-decision-rate) code acquisition receiver in a direct-sequence spread-spectrum system. The results illustrate the dynamic dependence of the mean acquisition time on system parameters, such as the predetection signal-to-noise ratio (SNR), the decision threshold settings, and the ratio of the decision rate to the code rate.

Experimental and theoretical comparison of some algorithms for beamforming in single receiver adaptive arrays

BG Wahlberg — 2008-02-24T13:45:23-00:00

Antennas and Propagation, IEEE Transactions on, Vol. 39, No. 1. (1991), pp. 21-28.

Adaptive null steering in single receiver adaptive arrays is discussed. The single receiver structure allows only output power for a given set of weights to be measured. The problem, then, is to adaptively adjust the weights of the antenna array based on output power measurements only so as to reject interference signals while maintaining a fixed response in a given look direction. The authors determine the optimal beamformer weights in a single step, by estimating the covariance matrix of the array sensor outputs using a weight perturbation technique. Based on this covariance matrix estimate, three different approaches for finding the beamformer weights are studied. The first corresponds to a sample matrix inversion scheme, with the sample covariance matrix replaced by the one obtained from the perturbation estimation method, while in the second approach the weights are determined using an eigenvalue decomposition of the covariance matrix estimate. In the third approach the directions-of-arrival (DOAs) of the incoming wavefronts are first estimated, and then, in a second step, the beamformer weights are calculated from the DOA estimates. The advantage of the third approach is that this method is not affected by correlation between the different sources

A smart antenna receiver array using a single RF channel and digital beamforming

JD Fredrick — 2008-02-24T12:58:53-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 50, No. 12. (2002), pp. 3052-3058.

A new type of smart antenna array receiver with adaptive beamforming is proposed. The novel system offers a drastic reduction in hardware requirements for the smart antenna system through the use of a new Spatial Multiplexing of Local Elements (SMILE) scheme. In this scheme, a single element of the array is sequentially connected to signal processing circuitry in order to sample the incoming modulated carrier. The sampling rate is higher than the signal bandwidth so that the information of the original signal can be fully restored in the post stages using low-pass filters. This system offers an N times reduction in RF hardware for an N-element array. A four-element prototype is built. System principles, SNR, advantages, and hardware, including a new type of array feed network, are discussed. The system performance is validated through a link test with digitally modulated data.