Receive Antenna Array Research Articles

A 77-GHz Cooperative Radar System Based on Multi-Channel FMCW Stations for Local Positioning Applications

In this paper, a radar system for local positioning applications is presented. The system consists of frequency modulated continuous-wave (FMCW) stations operating in W-band that are loosely coupled using time-delayed ramp start signals. A centralized signal processing approach allows to relax the required synchronization accuracy between the stations and further leads to a cancellation of phase noise and phase distortions caused by imperfect FMCW ramps. All stations are equipped with an antenna array and multiple receivers. Thus, a signal processing approach is developed in this work that combines the positive effects from the centralized processing with the information from the antenna array in a digital-beamforming based approach to improve the multipath robustness of the overall system. The developed theory is confirmed in measurements carried out with a prototype system consisting of two stations. Various measurements in multipath environments confirm the improved robustness leading to a worst-case root-mean-square position error of 15 mm under strong multipath conditions which were simulated inside an anechoic chamber.

Direction of Arrival Estimation under Spread Spectrum Reference Signal Assisted Radio

In the present work, a direction of arrival estimator, under spread spectrum reference of signal-assisted radio operating in a Rayleigh fading channel, is proposed. The analysis, which is applied to general receiver antenna array configurations, demonstrates the high performance of the estimator which is due to the double dispreading (code word and reference signal). The probability distribution function of the estimator is extracted and the system’s robustness in regard to large number of interferers is demonstrated.

Radar interferometer calibration of the EISCAT Svalbard Radar and a additional receiver station

The EISCAT Svalbard Radar has two parabolic dishes. In order to attempt to implement radar aperture synthesis imaging methods three smaller, passive receive array antennas were built. Several science goals for this new receiver system exist, the primary of which is to study so called naturally enhanced ion acoustic lines. In order to compare radar aperture synthesis imaging results with measurements from optical imagers, calibration of the radar interferometer system is necessary. In this work we present the phase calibration of the EISCAT Svalbard interferometer including one array antenna. The calibration was done using the coherent scatter from satellites passing through the radar beam. Optical signatures of the satellite transits provide accurate position for the satellites. Using transits of a number of satellites sufficient for mapping the radar beam, the interferometric cross-phase was fitted within the radar beam. The calibration technique presented in this work will be applied to all antenna pairs of the antenna configuration for future interferometry studies.

Chebyshev Stopbands for CIC Decimation Filters and CIC-Implemented Array Tapers in 1D and 2D

The stopbands of a cascaded integrator-comb (CIC) decimation filter are ordinarily very narrow, as each results from a single multiple zero. Here response sharpening with a Chebyshev polynomial, using a previously reported CIC variant, separates each such multiple zero into an equiripple stopband. By trading unneeded depth at stopband center for improved depth at the stopband edge, the latter depth improves by some 6(N-1) dB in an Nth-order system. Increased computational complexity is modest: a few low-speed additions and multiplications by small integer coefficients that can often be chosen as powers of two. Alternatively, parameters can be configured to replace the many small stopbands with one large one, and this is demonstrated here with example spatial-processing CIC designs that create pencil beams for 1D and 2D receive antenna arrays.

Joint Space-Time Parameter Estimation for Underwater Communication Channels with Velocity Vector Sensor Arrays

In this paper, the problem of joint space-time parameter estimation for underwater wireless communication channels in a multipath environment is addressed. We consider the receive antenna array to be configured with multiple vector sensors, each of which consists of a pair of orthogonal velocity sensors. A quadrilinear model for the channel is formulated, and a quadrilinear decomposition method developed for joint angle and delay estimation (JADE). In addition, a computationally simple subspace-based algorithm is proposed for the problem under consideration. The basic idea behind this algorithm is to use the angle information embedded in the velocity vector sensors to start two polynomial rooting procedures for the angle and delay in succession. Simulation results are finally presented to verify the efficacy of the proposed algorithms.

Full-Duplex MIMO Relaying: Achievable Rates Under Limited Dynamic Range

In this paper we consider the problem of full-duplex multiple-input multiple-output (MIMO) relaying between multi-antenna source and destination nodes. The principal difficulty in implementing such a system is that, due to the limited attenuation between the relay's transmit and receive antenna arrays, the relay's outgoing signal may overwhelm its limited-dynamic-range input circuitry, making it difficult-if not impossible-to recover the desired incoming signal. While explicitly modeling transmitter/receiver dynamic-range limitations and channel estimation error, we derive tight upper and lower bounds on the end-to-end achievable rate of decode-and-forward-based full-duplex MIMO relay systems, and propose a transmission scheme based on maximization of the lower bound. The maximization requires us to (numerically) solve a nonconvex optimization problem, for which we detail a novel approach based on bisection search and gradient projection. To gain insights into system design tradeoffs, we also derive an analytic approximation to the achievable rate and numerically demonstrate its accuracy. We then study the behavior of the achievable rate as a function of signal-to-noise ratio, interference-to-noise ratio, transmitter/receiver dynamic range, number of antennas, and training length, using optimized half-duplex signaling as a baseline.

The spatial features of the up- and downshifted maxima in stimulated electromagnetic emissions

The determination of the source regions of some of the spectral components of stimulated electromagnetic radio emissions (SEE) is reported. The investigation was performed using observations made in 2005 during heating campaigns with the EISCAT heating facility near Tromsø, Norway. A four-channel high-frequency interferometer, designed by the Polar Geophysical Institute (PGI), was used to determine the arrival direction of the SEE signal. Three channels of the interferometer were connected to three antennas of the receiving antenna array. The antennas were installed in the meridional (north-south) and zonal (east-west) planes. The distance between the heating facility and receiver antenna array was 12.6km. The measurements allowed determination of the azimuth and elevation angles of the intensity-weighted mean location of the SEE source regions by the phase difference method. In order to increase accuracy and eliminate the effects of interferences, data were selected based on the coherence of the signals. The results show that different parts of the down- and up-shifted maxima (DM, UM) features in the SEE spectrum are generated in different regions of the ionosphere, possibly in an elongated region along the magnetic field.

Improved Noise Modeling with Mutual Coupling in Receiving Antenna Arrays for Direction-of-Arrival Estimation

A new method for modeling correlated noise in receiving antenna arrays for direction-of-arrival (DOA) estimation is introduced. The array noise is divided into a coupled and an uncoupled components which originate from the array environment and the internal circuitry of the antenna elements, respectively. While the uncoupled noise power can be determined a priori and be removed from the array received power, the antenna mutual coupling in the coupled noise component can be decoupled in the same way as the antenna mutual coupling in the signals. This results in a very simple but effective MUSIC DOA estimation algorithm. Simulation results are presented to validate and demonstrate the performance of the new method.

System integration and radiation pattern measurements of a phased array antenna employing an integrated photonic beamformer for radio astronomy applications

In this paper we describe the system integration and the experimental demonstration of a photonically beamformed four-element receiving array antenna for radio astronomy applications. To our knowledge, the work described here is the first demonstration of the squint-free, continuously tunable beamsteering capability offered by an integrated photonic beamformer based on optical ring resonator true-time-delay units, with measured radiation patterns. The integrated beamformer is realized in a low loss, complementary metal-oxide-semiconductor (CMOS) compatible optical waveguide technology. The measurements show a wideband, continuous beamsteering operation over a steering angle of 23.5 degrees and an instantaneous bandwidth of 500 MHz limited only by the measurement setup.

Fading model for antenna array receiver for a ring-type cluster of scatterers

This correspondence presents an alternate method for simulating the time-varying flat fading wireless channels for the antenna array receivers, in which the discrete ring of scatterers is incorporated around the mobile transmitter to model the spreading of azimuth. The ring-type cluster of scatterers continuously changes due to the movement of the mobile unit. Under this time-varying environment, each scatterer, at successive stages of the ring, is correlated with the scatterers at preceding stages of the ring using the second-order Markov modelling. The correlation of fading waveforms generated with the proposed paradigm is compared with the expected analytical correlation, which clearly depicts that the simulation results are consistent with the findings based on Jakes’ model.

A New Combination of RAKE Receiver and Adaptive Antenna Array Beamformer for Multiuser Detection in WCDMA Systems

The aim of this paper is to combine smart antenna beamforming and RAKE receiver in wideband code division multiple access (WCDMA). The proposed method combines spatial diversity as well as temporal diversity to improve the performance and overcome both interferences and multipath fading. This investigation has focused on one of the new proposed blind beamforming algorithms. It is based on constrained constant modulus (CCM) algorithm which is used for deriving a recursive-least-squares (RLS-) type optimization algorithm. We illustrate the comparison of bit error rate (BER) of the proposed receiver with simple correlator and also 1D-RAKE receiver in multiuser detection (MUD) WCDMA. The simulation results show that the proposed 2D-RAKE receiver offers lower BER rather than conventional ones, that is, it is an effective solution for decreasing the effect of interference and increasing the capacity, in a joint state.

Sparse Antenna Array Design for MIMO Active Sensing Applications

In active sensing applications, MIMO systems permit increased flexibility for transmit beampattern design, via waveform diversity, compared to phased-array approaches. When uniform arrays are not mandated, additional degrees of freedom for transmit beampattern design can be obtained via sparse array design considerations. Herein, we extend the motivation behind sparse receive array methodologies to that of sparse MIMO transmit array design. We propose a cyclic approach to MIMO transmit array design that can be used to approximate desired transmit beampatterns. Furthermore, we illustrate how this iterative approach can be adapted to design sparse receive antenna arrays using both vector and matrix weighting techniques.

Wideband Analysis of Mutual Coupling Compensation Methods

The performance of various mutual coupling estimation and compensation methods is quantified and compared for wideband operation. Their main limitations and the required procedures to estimate the coupling matrix are outlined. It is determined that only the full-wave method is accurate at all frequencies. The performance tradeoffs associated with the other methods are described. General guidelines based on the electrical size and separation of the array elements are formulated for each method. The results can be valuable for both wideband and narrowband receiving antenna arrays.

Non-linear effects of intensity-modulated and directly detected optical links on receiving a linear frequency-modulated waveform

Limitations imposed by the non-linearity of optical links, in the front end of a receiving array antenna, on the performance of a pulse compression radar are studied. Particularly linear frequency-modulated waveforms backscattered from a pair of targets are inspected. Inter-modulation and gain compression by noise are presented as two remarkable phenomena. For an interconnection of two dual-drive Mach-Zehnder modulators, the sensitivity of the compressed echo at the output of a matched filter receiver to certain tunable parameters is studied numerically. Finally, certain values of DC bias and phase shift between the modulators- electrodes are recommended.

무인 차량 탑재형 전방 관측 영상 레이다 가능성 연구

This study describes the design and verification of short range UWB(Ultra Wideband) imaging radar that is able to display high resolution radar image for front area of a UGV(Unmanned Ground Vehicle). This radar can help a UGV to navigate autonomously as it detects and avoids obstacles through foliage. We describe the relationship between bandwidth of transmitting signal and range resolution. A vivaldi antenna is designed and it`s radiation pattern and reflection are measured. It is easy to make array antenna because of small size and thin shape. Aperture size of receiving array antenna is determined by azimuth resolution of radar image. The relation of interval of receiving antenna array, image resolution and aliasing of target on a radar image is analyzed. A vector network analyzer is used to obtain the reflected signal and corner reflectors as targets are positioned at grass field. Applicability of the proposed radar to UGV is proved by analysis of image resolution and penetrating capability for grass in the experiment.

Semi-blind adaptive beamforming for high-throughput quadrature amplitude modulation systems

A semi-blind adaptive beamforming scheme is proposed for wireless systems that employ high-throughput quadrature amplitude modulation signalling. A minimum number of training symbols, equal to the number of receiver antenna array's elements, are first utilised to provide a rough initial least squares estimate of the beamformer's weight vector. A concurrent constant modulus algorithm and soft decision-directed scheme is then applied to adapt the beamformer. This semi-blind adaptive beamforming scheme is capable of converging fast to the minimum mean-square-error beamforming solution, as demonstrated in our simulation study.

Unified Definitions of Efficiencies and System Noise Temperature for Receiving Antenna Arrays

Two methods for defining the efficiencies and system noise temperature of a receiving antenna array have recently been developed, one based on the isotropic noise response of the array and the other on an equivalent system representation. This letter demonstrates the equivalence of the two formulations and proposes a new set of standard definitions of antenna figures of merit for beamforming arrays that accounts for the effect of interactions between antenna element mutual coupling and receiver noise on system performance.

Impact of the Receive Antenna Arrays on Spatio-Temporal Availability in Satellite-to-Indoor Broadcasting

This contribution presents the results of our study on spatio-temporal availability in satellite-to-indoor broadcasting. We compare the performance of single and multiple antenna arrays consisting of theoretical and measured antennas with various polarimetric radiation patterns and coupling effects for different satellite elevation angles. The spatial satellite to indoor channels are obtained by a 3D ray tracing engine and by a geometry-based channel modeling tool. The temporal fluctuations of the channels are modeled by the PDF of a truncated normal distribution and are based on satellite-to-indoor measurements. The additional antennas at the receiver reduce both the spatial and the temporal variability of the received power, leading to a significant reduction of the transmit power required to achieve the same target availability. The simulation results suggest that the spatial correlation in the line-of-sight room area is higher than in the non-line-of-sight room area. In the line-of-sight areas, the best performance is achieved by multiple circularly polarized receive antennas. For elevations higher than 50 in the non-line-of-sight areas, a combination of horizontally and vertically (orthogonal) polarized antennas shows the best performance, especially if high availabilities are considered. Furthermore, the influence of coupling effects between closely spaced receive antennas on the availability is studied. In general, antenna coupling effects should be handled by increasing the required link margin. The influence of the temporal changes due to a person movement on the availability is found to be not very significant.

SINR Feedback Based Rate Control for Dual-Antenna-Array Multi-Cellular Networks with Cochannel Interference

We propose in this paper a dual-antenna-array (with transmitter antenna array and receiver antenna array) architecture, where the antenna elements are divided into several antenna element sets and each traffic channel is transmitted over an antenna element set, to realize the multiple traffic channels set up by a user. A SINR feedback based algorithm, which can regulate the transmission rate by iteratively adjusting the power on each traffic channel, is proposed to execute the rate control for the proposed dual-antenna-array architecture under cochannel interference. It is shown that the proposed algorithm can make the throughput meet the throughput requirement or achieve the weighted bandwidth sharing for certain fairness. In addition, we further propose a traffic channel configuration algorithm to help the SINR feedback based algorithm find the optimal traffic channel configuration that can meet the throughput requirement for each traffic channel or results in the maximal total throughput for each user.

Optimization of Training Signal Transmission for Estimating MIMO Channel under Antenna Mutual Coupling Conditions

This paper reports investigations on the effect of antenna mutual coupling on performance of training-based Multiple-Input Multiple-Output (MIMO) channel estimation. The influence of mutual coupling is assessed for two training-based channel estimation methods, Scaled Least Square (SLS) and Minimum Mean Square Error (MMSE). It is shown that the accuracy of MIMO channel estimation is governed by the sum of eigenvalues of channel correlation matrix which in turn is influenced by the mutual coupling in transmitting and receiving array antennas. A water-filling-based procedure is proposed to optimize the training signal transmission to minimize the MIMO channel estimation errors.