Filter Bank Receiver Research Articles

Automotive Radar Optimization Design in a Spectrally Crowded V2I Communication Environment

A main challenge for radar-aided millimeter wave (mmWave) vehicle-to-infrastructure (V2I) communication application, is that it requires mitigating the mutual interference between vehicular radar and communication operating at same frequency bands. This paper considers the joint design of the multiple-input multiple-output (MIMO) transmit waveform and receive filter bank for road side unit (RSU)-mounted radar in a spectrally crowded V2I communication environment. With the criterion of maximizing the average signal-to-interference-plus-noise ratio (SINR), a non-convex problem, which involves the weighted-sum waveform energy over the overlayed space-frequency bands, energy and similarity constraints, is formulated. An iterative algorithm is proposed to solve the joint optimization problem. At each iteration, the transmit waveform is optimized based on the alternating direction method of multipliers (ADMM) method with a significantly lower computational complexity. As a consequence, accurate location information derived from the optimized radar is used to reduce the beam training overhead of V2I communication links. Finally, simulation results display the effectiveness of the devised method in finding feasible and enhanced solutions, importantly outperforming several counterparts.

MIMO Radar Design for Extended Target Detection in a Spectrally Crowded Environment

Multiple-input multiple-output (MIMO) radar design for extended targets in a spectrally crowded environment is a challenge owing to the high sensitivity of the target impulse response (TIR) and the increasing requests for spectrum. Assuming unknown TIR, this paper proposes a joint design method to optimize the transmit waveforms and receive filter bank in MIMO structure ensuring spectral compatibility with the overlayed radiators. A priori information is used to impose a spectral constraint on the waveforms, which is the result of a non-convex optimization problem aimed at enhancing the average signal-to-interference-plus-noise-ratio (SINR) over a finite uncertainty set for the TIR. The new method realizes an improved spectral cohabitation with the surrounding radiators through an appropriate modulation of the transmitted energy. In addition, we develop an iterative optimization algorithm which successively enhances the average SINR. Each iteration of the algorithm involves a hidden convex problem, which can be solved resorting to the rank-one decomposition procedure. Finally, the performance is assessed by studying the trade-off among the achieved SINR and spectral shape. The reported results are presented to analyze the performance of the devised method against several counterparts in terms of the SINR value and robustness.

Joint Design Method of Transmit-Receive for Airborne MIMO Radar Based on Feasible Point Pursuit

Consider the moving target detection performance degradation of airborne multiple-input multiple-output (MIMO) radar in the presence of inaccurate target prior information. This paper proposes a joint design method of transmit waveform and receive filter bank of airborne MIMO radar based on feasible point pursuit successive convex approximation (FPP-SCA). Firstly, a set of receive filter banks is designed in the region where the target may appear on the angle-Doppler plane, and the worst-case output signal-to-clutter-plus-noise ratio (SCNR) is maximized as the optimization criterion. Secondly, considering the energy constraint and similarity on the transmit waveform, the maximin joint design problem is formulated to improve the robustness of the MIMO space-time adaptive processing (STAP) radar against the uncertainty of target parameters. Finally, an FPP-SCA algorithm is employed to solve the maximin nonconvex joint design problem. Simulation results demonstrate the effectiveness of the proposed method in terms of better output SCNR, lower computational load, and more robustness against the errors of target parameters.

Maximin Joint Design of Transmit Waveform and Receive Filter Bank for MIMO-STAP Radar Under Target Uncertainties

This letter deals with the joint design of transmit waveform and receive filter bank for airborne multiple-input multiple-output (MIMO) radar under the target uncertainties. Assuming that the spatial angle and the Doppler frequency of the target are unknown, we formulate the maximin joint design problem by maximizing the worst-case signal-to-interference-plus-noise ratio (SINR) under the energy constraint, flexible modulus constraint, and similarity constraint on the transmit waveform. To tackle this problem, we develop a computationally efficient algorithm based on iterative feasible point pursuit successive convex approximation (FPP-SCA). Numerical results are provided to demonstrate the effectiveness and robustness of the proposed algorithm.

Joint Design of Colocated MIMO Radar Constant Envelope Waveform and Receive Filter to Reduce SINR Loss.

In this paper, we aim at the problem that MIMO radar’s target detection performance is greatly reduced in the complex multi-signal-dependent interferences environment. We propose a joint design method based on semidefinite relaxation (SDR), fractional programming and randomization technique (JD-SFR) and a joint design method based on coordinate descent (JD-CD) to solve the actual transmit waveform and receive filter bank directly to reduce the loss of strong interference to the output signal-to-interference-plus-noise ratio (SINR) of the radar system. Therefore, the maximization of output SINR is taken as the criterion of the optimization problem. The designed waveforms take into account the radar transmitter’s hardware requirements for constant envelope waveforms and impose similarity constraints on the waveforms. JD-SFR uses SDR, fractional programming and randomization technique to deal with the non-convex optimization problems encountered in the solution process. JD-CD transforms the optimization problem into a function of the phase of the waveform and then solves the transmit waveform based on CD. Compared with other methods, the proposed method has lower output SINR loss under strong power interference and forms deep nulls on the direction beampattern of multiple interference sources, which indicates that it has better anti-interference performance.

Robust Transceiver Design in the Presence of Eclipsing Loss for Spectrally Dense Environments

Radar system design for the detection of targets with unknown actual range in spectrally crowded environments is a challenge due to increasing demands for spectrum and the possibly experienced echo eclipsing. Assuming unknown target echo delay, this article deals with robust joint design of the radar code and receive filter bank guaranteeing spectral compatibility with the surrounding electromagnetic radiators. The average signal-to-interference-plus-noise ratio (SINR) at the output of the filter bank is considered as the performance measure to optimize under both similarity and spectral compatibility constraints on the radar code. Through an appropriate reformulation of the resulting nonconvex optimization problem, we devise an alternate optimization algorithm, which sequentially improves the average SINR and converges to a point fulfilling the Karush-Kuhn-Tucker (KKT) conditions of the design problem. Each iteration of the algorithm involves both a convex and a hidden convex optimization problem, which can be solved via the rank-1 decomposition procedure. Finally, the performance is assessed by studying the tradeoff among the SINR, spectral shape, and autocorrelation. Numerical results reveal that the new method has better flexibility and robustness compared to several counterparts, which are presented in open literature.

Hidden Convexity in Robust Waveform and Receive Filter Bank Optimization Under Range Unambiguous Clutter

This letter deals with the robust joint design of radar transmit waveform and receive filter bank in a background of range unambiguous signal-dependent clutter. Assuming an unknown Doppler shift for the target, the worst-case Signal-to-Interference-plus-Noise-Ratio (SINR) at the output of the receive filter bank is considered as the figure of merit. The transceiver design is pursued considering a max-min optimization problem with some constraints on the transmit energy, similarity, and signal dynamic range. Hidden convexity is shown and a procedure to derive optimal waveform and filters is given. Simulation results highlight the effectiveness of the devised method.

주파수 공유기법을 적용한 RF 송수신기에 대한 연구

In this paper Communication data link equipment on a high speed-hopping method to use the frequency resources efficiently for the frequency environment is introduced such as sensing techniques, using the same frequency band by using the received two-channel technique and the receive filter bank unit applied to be shared with other equipment such as radar and so on. The real-time measurement and analysis were operated for measurement the frequency environment of the operating band in advance. and primarily equipment to develop is analyzed how the interference effect to the radar minimize the operation of radar equipment. In reverse, to use the same frequency band the methods such as frequency sharing techniques are presented in this paper. Finally, by design of the main items of the RF transceiver NF, transmission output, and a simulation of the IMD, such as whether the key is verified prior to meet specifications.

Wideband Waveform and Receiver Filter Bank Design for Clutter Suppression

Modern wideband radar systems with long integration time, equipped with arbitrarily waveform generators, raise a demand for advanced signaling transmission schemes. In this paper, we propose two algorithms to select transmit waveforms and receiver filters. The techniques are based on a clutter suppression criterion. For the first algorithm, we employ an optimized filter bank, and for the second algorithm, we use a matched filter bank. Clutter suppression is achieved by minimizing the correlation between receiver filters and interfering clutter echoes. The algorithm, for the optimized filter bank, is extended to adapt the transmission scheme and receiver filters to a time-evolving scenario. Adaptation parameters are based on estimates of a clutter map and detected target characteristics. To estimate the clutter map we propose a Kalman filter, whereas target parameters are calculated using a least-squares fit to data. The efficiency of the algorithms and the adaptation scheme are visualized through a numerical simulation.

Progress of microwave collective Thomson scattering in LHD

Microwave collective Thomson scattering (CTS) by using a 77 GHz gyrotron is routinely working in LHD and the improvements of the system is now underway. The targets of this diagnostic are measurements of energetic fast ion distribution and ion ratio. In the present system, 800kW 77 GHz gyrotron is injected horizontally and scattered radiation is received changing scattering angle. The system works with existence of electron cyclotron resonance layer. Thus, most of the power is absorbed at the layer like beam damping and stray radiation dramatically decreases. Gyrotron is modulated at 40 Hz, then, background ECE, which is signal in gyrotron off phase, is subtracted from scattered signal in gyrotron on phase. The perturbation of electron temperature due to the gyrotron injection is almost negligible. Temporal evolution of CTS spectrum is obtained by 32ch filter bank receiver through discharge and fine spectrum is obtained by 10 GHz sampling fast digitizer for 80 ms. Change of the width and asymmetry of CTS spectrum is observed after turning off of tangentially injected neutral beam (NB). This is qualitatively consistent with reduction of fast ion density. Preliminary data of ion ratio between hydrogen and helium are also obtained.

Blind Capon-like adaptive ST-BC MIMO-CDMA receiver based on constant modulus criterion

In this paper, we present a new Capon-like blind receiver based on linearly constrained constant modulus (LCCM) criterion for the multiple-input multiple-output (MIMO) antennas system along with space–time block code (ST-BC) using direct-sequence code division multiple access (CDMA) modulation technique. A time-varying channel model with generalized sidelobe canceller (GSC) associated with the recursive least squares (RLS) algorithm is implemented to reduce the complexity of receiver design. In our derived algorithm, the parameter of constant modulus, α, relating to the desired user power is updated adaptively via stochastic gradient algorithm to track userʼs amplitude variation. Also we prove theoretically that in the two-branch filter bank receiver design the weight vector of one branch can be updated simply using the other one, which has been obtained with our proposed CM-GSC-RLS algorithm, with simple pre-calculated transform. Hence computation complexity of the proposed adaptive blind receiver can be further reduced significantly. Via intense simulations it reveals that our proposed scheme has robust performance against the userʼs acquisition inaccuracies comparing with current available algorithms.

Efficient narrowband interference cancellation in ultra‐wide‐band rake receivers

In this study, different pulse modulation parameters, such as symbol error rate (SER), power loss and bandwidth were investigated to highlight the most suitable parameter for narrowband interference cancellation in ultra-wide-band (UWB) Rake receivers. Thus, the performance of transmitter pulse was evaluated at the UWB Rake receiver. Finally, comparison of various filter bank receivers in terms of number of filters and SER was achieved by using a new accurate indoor UWB IEEE model channel with different propagation scenarios.

LEAST MEAN SQUARED BACKGROUND CALIBRATION FOR OFDM MULTICHANNEL RECEIVERS

This paper presents a data estimation scheme for wide band multichannel charge sampling filter bank receivers together with a complete system calibration algorithm based on the least mean squared (LMS) algorithm. A unified model has been defined for the receiver containing all first order mismatches, offsets, imperfections, and the LMS algorithm is employed to track these errors. The performance of this technique under noisy channel conditions has been verified. Moreover, a detailed complexity analysis of the calibration algorithm is provided which shows that sinc filter banks have much lower complexity than traditional continuous-time filter banks.

Analytical framework and bandwidth optimisation of orthogonal frequency division multiplexing low-order multi-channel filter-bank receivers for achieving sampling clock-jitter robustness

Stringent jitter specifications in the sampling clocks severely limit the evolution of future generations of wideband high-performance receivers. For instance, it is shown that a conventional single-channel receiver requires 1.5 ps of jitter standard deviation to achieve 34 dB signal-to-noise ratio (SNR) when sampling a 10 GHz orthogonal frequency division multiplexing (OFDM) signal. This study presents an analytical framework for the design of jitter-tolerant multi-channel filter-bank OFDM receivers. Additionally, the study presents an optimisation method for the filter-bank bandwidth that is able to reduce the filter-bank order saving power and area and achieving optimal signal quality. Simulations that confirm the analytical result show that 34 and 38 dB SNR are achieved with 5-channel and 10-channel receivers, respectively, when using second-order bandwidth-optimised filter-bank that samples a 10 GHz OFDM signal tolerating 6 ps of jitter.

Clock-Jitter-Tolerant Wideband Receivers: An Optimized Multichannel Filter-Bank Approach

Clock jitter is one of the most fundamental obstacles in realizing future generations of wideband receivers. Stringent jitter specifications in the sampling clocks of high-performance single-channel and multichannel time-interleaved analog-to-digital converters severely limit the evolution of baseband receivers. This paper presents an analytical framework for the design of clock-jitter-tolerant low-order multichannel filter-bank receivers, with techniques to dramatically lower the sampling-clock-jitter specifications. Although it is well understood that high-order frequency-channelized receivers provide higher tolerance to sampling jitter, this paper shows that low-order bandwidth-optimized multichannel receivers can achieve similar sampling-jitter tolerance. Additionally, this paper presents design tradeoffs and specifications of an example multichannel receiver that can process a 5-GHz baseband signal with 40 dB of signal-to-noise-ratio using sampling clocks that can tolerate up to 5 prmss clock jitter. In comparison, existing architectures based on time-interleaving require 0.5 prmss clock jitter for the given specifications. This extreme jitter tolerance allows for relaxed design of clocking systems, which averts a major roadblock in future wideband-communication-receiver development and provides the potential to enable several high-data-rate communication applications.

Maximum SINR Synchronization Strategies in Multiuser Filter Bank Schemes

We consider synchronization in a multiuser filter bank uplink system with single-user detection. Perfect user synchronization is not the optimal choice as the intuition would suggest. To maximize performance the synchronization parameters have to be chosen to maximize the signal-to-interference-plus-noise ratio (SINR) at each equalizer subchannel output. However, the resulting filter bank receiver structure becomes complex. Therefore, we consider two simplified synchronization metrics that are based on the maximization of the average SINR of a given user or the aggregate SINR of all users. Furthermore, a relaxation of the aggregate SINR metric allows implementing an efficient multiuser analysis filter bank. This receiver deploys two fractionally spaced analysis stages. Each analysis stage is efficiently implemented via a polyphase filter bank, followed by an extended discrete Fourier transform that allows the user frequency offsets to be partly compensated. Then, sub-channel maximum SINR equalization is used. We discuss the application of the proposed solution to Orthogonal Frequency Division Multiple Access (OFDMA) and multiuser Filtered Multitone (FMT) systems.

Millisecond Pulsar Timing at Kalyazin Observatory

Pulsar timing of millisecond pulsars are carried on at Kalyazin radio astronomical observatory (Russia) since 1995. Seven pulsars are observed at 0.6 GHz by full steerable 64-m dish radio telescope RT-64 and filter-bank receiver. The millisecond pulsar B1937+21 is being monitored at Kalyazin observatory (0.6 GHz) and Kashima space research centre of NICT (Japan) (2.3 GHz), simultaneously since 1996.

Computationally efficient algorithm for reducing the complexity of software radio receiver's filter bank

In this paper, a computationally efficient method for extracting individual radio channels from the output of the wideband analog to digital converter (ADC) is presented. In a software radio, the extraction of individual channels from the output of the wideband ADC is by far the most computationally demanding task; hence it is very important to devise computationally efficient algorithms for this task. We proposed a new algorithm by assuming the symmetric signal with periods of the length-P (number of coefficients in low pass filter prototype) as an input signal to the subsampled filter bank. Also we divide the complex input x[n] into real and imaginary parts, then we perform operations in each part using two parallel filter banks. Finally, we add the outputs in two parts. By employing this algorithm to the subsampled filter bank channelizer, the complexity of the proposed algorithm was reduced by considerable amount of 81%.

The influence of flight speed on the ranging performance of bats using frequency modulated echolocation pulses.

Many species of bat use ultrasonic frequency modulated (FM) pulses to measure the distance to objects by timing the emission and reception of each pulse. Echolocation is mainly used in flight. Since the flight speed of bats often exceeds 1% of the speed of sound, Doppler effects will lead to compression of the time between emission and reception as well as an elevation of the echo frequencies, resulting in a distortion of the perceived range. This paper describes the consequences of these Doppler effects on the ranging performance of bats using different pulse designs. The consequences of Doppler effects on ranging performance described in this paper assume bats to have a very accurate ranging resolution, which is feasible with a filterbank receiver. By modeling two receiver types, it was first established that the effects of Doppler compression are virtually independent of the receiver type. Then, used a cross-correlation model was used to investigate the effect of flight speed on Doppler tolerance and range-Doppler coupling separately. This paper further shows how pulse duration, bandwidth, function type, and harmonics influence Doppler tolerance and range-Doppler coupling. The influence of each signal parameter is illustrated using calls of several bat species. It is argued that range-Doppler coupling is a significant source of error in bat echolocation, and various strategies bats could employ to deal with this problem, including the use of range rate information are discussed.

A low complexity reduced-rank MMSE receiver for DS/CDMA communications

The minimum mean squared error (MMSE) receiver is a linear filter which can achieve optimal near-far resistance in direct-sequence code-division multiple-access communications. However, one of the main problems of this receiver is the required number of filter taps, which is typically large. This is especially true in systems with a large processing gain in which case the receiver's computation burden becomes very high. As a result, methods for reducing the complexity of the MMSE receiver have been of great interest in recent years. We propose an efficient partitioned MMSE receiver based on a classification algorithm. It is shown that the computational complexity (in terms of the filter taps) of the proposed receiver can be reduced significantly while good performance is maintained. Based on the special structure of our proposed receiver, we also propose a release-merge adaptive partition algorithm which can update the partition and the receiver's coefficients simultaneously. In particular, it is demonstrated that the proposed receiver can perform much better than previously proposed reduced-rank MMSE receivers, such as the partial despreading MMSE receiver and the cyclically shifted filter bank receiver, with even a smaller number of taps.