Multichannel Receiver Research Articles

Average Error Probability of an Optically Pre-Amplified Pulse-Position Modulation Multichannel Receiver under Malaga-ℳ Fading

We present analytical results on the average probability of error (PER) performance of an optically pre-amplified pulse-position modulation (PPM) receiver under Malaga- M fading. The results are in the form of a finite sum whose number of terms depends on the PPM modulation order and the noise modes of the amplifier, enabling the efficient calculation of the average PER. In addition, we utilized the presented analysis to evaluate the performance of a equal-gain-combining (EGC) diversity receiver that operates in conjunction with optical amplification and PPM. The results show that the utilization of diverse and relatively low PPM orders achieves a drastic reduction in the average PER.

Opposite-Side Ambiguities in Radar Sounding Interferometry

We report the analysis of opposite-side ambiguities in single-pass radar sounding interferometry. Nadir pointing radar sounders suffer inherent cross track ambiguities that cannot be separated with the power image alone. Interferometry can be used to interpret these ambiguities when data are collected with multichannel receivers. However, opposite-side surface clutter, volume scattering, and cross track range misalignment create unique interferometric phase and correlation signatures. Such signatures are observed experimentally in data collected by the Polarimetric Airborne Radar Ice Sounder (POLARIS) P-band multichannel radar sounder. We derive analytic expressions to predict the observations and validate them with simulation. In addition, we observe and explain a correlation dropout feature that is due to volume scattering competing with surface clutter in the null of the cross track antenna pattern. The purpose of this article is to explain opposite-side ambiguity signatures in radar sounder interferometry and provide models and techniques for scientific interpretation of interferograms.

Rao Detector for Passive MIMO Radar With Direct-Path Interference

This article deals with the problem of target detection in a passive multiple-input multiple-output (MIMO) radar network involving noncooperative illuminators of opportunity (IOs) and geographically dispersed multichannel receivers. The signal model considers the direct-path interference (DPI). We employ the Rao test to solve the problem and derive a closed-form detector. Then, by considering the properties of the ambiguity functions of most IO waveforms, an approximated version of the detector with a simpler form is derived. Two detectors in the case of an active MIMO network are also provided as the upper bounds of the passive situations. Moreover, considering target echo signal fluctuation, we have analyzed the performance of the detectors in terms of probability of miss-detection when being used in a multistatic configuration and have specified the conditions under which the full diversity gain is achieved. Numerical results verify the effectiveness of the proposed detectors and demonstrate that the proposed detectors have performance very close to the active situation.

L대역 신호 수집을 위한 소형 디지털 수신기 설계 및 제작

In this paper, we have designed and fabricated a compact digital receiver for acquiring L-band signals. A receiver, based on direct RF sampling, has been designed for a compact multi-channel receiver. The design of the receiver is based on the system parameters and it is further fabricated on the basis of the simulation model. The performance of the fabricated digital receiver is analyzed by comparing it with the performance of the simulation model. It is observed that the fabricated digital receiver exhibits a receive sensitivity of −102 dBm, and eventually reaches the dynamic range of 62.7 dB.

Microwave multi-frequency measurement based on an optical frequency comb and a photonic channelized receiver.

A new method, to the best of our knowledge, to measure frequencies of received microwave signal based on an optical frequency comb (OFC) and a photonic multi-channel receiver is proposed and simulated. The measurement system mainly includes a seed laser, an OFC generator composed of two cascaded Mach-Zehnder modulators, a frequency shifter, an intensity modulator, a wavelength-division demultiplexer, photodiodes (PDs), and electrical filters. Two sets of beat signals need to be obtained in the measurement process. By analyzing the two sets of beat signals, multiple frequency components of the microwave signal can be measured at a time. The validity of the proposed scheme is verified by VPI simulation software. It is shown that microwave frequencies within dozens of gigahertz can be precisely measured, and factors affecting the frequency measurement range are also studied.

COBIS: Opportunistic C-Band Bistatic SAR Differential Interferometry

Monitoring large built structures, landslides, volcanoes, or glaciers implies relative height measurements and line-of-sight (LOS) displacement measurements, which are typically performed with monostatic spaceborne synthetic aperture radar (SAR) sensors. In this case, for each satellite that illuminates a given location, we can usually exploit only the information available from one ascending/descending orbit, and if the satellite uses multiple subswaths, the information is obtained only from one subswath per orbit. A bistatic configuration with spaceborne transmitter and fixed ground-based (GB) receiver opens the possibility to exploit the information available from more than one orbit and one subswath per orbit. Additionally, such a configuration offers new perspectives for target tracking and characterization (e.g., multiple LOSs and bistatic scattering signatures). This article presents an opportunistic C-band bistatic SAR differential interferometry architecture that uses a multichannel GB stationary receiver and a separate transmitter, which can be either the Sentinel-1A/B satellite, used opportunistically, or a specially designed GB sliding transmitter. The combination of the operation modes based on spaceborne and GB transmitter allows monitoring a small critical area of interest with many acquisitions triggered by the GB transmitter and surveying of the whole surrounding area with a small number of acquisitions corresponding to the satellites passes. The hardware platforms are presented along with the bistatic interferometric processing flow, and the potential of the proposed architecture is assessed in the context of monitoring large built structures.

Experimental Evaluation of Multiple Channel SDR Signal Receivers Effectiveness

Introduction. The SDR technology makes it possible to build multichannel signal receivers for replacing single-channel devices. In this the amount of real time calculations grows considerably. For these calculations it is expedient to apply parallel computations based on the multi-core central and graphic processors. The theoretical efficiency evaluation of the such receivers ignores many factors. The purpose of the article is an experimental efficiency evaluation of the SDR multichannel signal receivers’ construction.Modeling, analysis and testing. The multichannel research firmware receiver consisted of an SDR receiver, a USB controller and a computer. On a computer in a single server shell worked functionally completed software signal processingmodules.They provided reception of IQ-samples from the SDR receiver, their transfer to zero frequency, low-frequency filtration with decimation of the received samples. The experimental dependences of the maximum number of receiving channels from the decimation coefficient are obtained. At a decimation coefficient from 20 to 100 dependencies are hyperbolic, and from 100 to 10000 dependencies are directly proportional. The obtained dependences on the direct proportional section are approximated by the method of least squares. For a selected hardware platform, the proportionality coefficient is 6,1 for filters from 61 to 1001 order and 0,8 for filters from 1001 to 3901 order.Conclusions. It’s possible to increase the number of receiving channels by: increasing the decimation coefficient. The group signal and receiving channel spectrum bandwidth are the source data. Therefore, there is no possibility to increase the number of receiving channels by the decimation coefficient; decreasing filter order. The signal filtering quality depends from the filter order. Therefore, the choice of the filter order requires a compromise. The adequacy of the selected filter order to ensure a qualitative filtration with a given decimation coefficient is experimentally evaluated by the ratio of the given filtration band to the received. The obtained dependencies confirm the theoretical data: to ensure a high-quality filter with the increase of the decimation coefficient the order of the filter should be increased. With a fixed decimation coefficient, in order to achieve qualitative filtration, the order of the filter should be increased. It’s will reduce the number of receiving channels. To increase the number of receiving channels it’s necessary to reduce the order of the filter, which will lead to deterioration of the filtration quality.

Master-slave carrier recovery for M-QAM multicore fiber transmission.

Master-slave carrier recovery is a digital signal processing technique that uses correlated phase noise in multi-channel receivers to eliminate redundant carrier recovery blocks. In this paper we experimentally investigate the performance of master-slave carrier recovery for multicore fiber transmission in the presence of inter-channel nonlinear interference. Using a triple parallel loop setup we jointly receive three spatial channels in a 7-core fiber for transmission distances of up to 1600 km. We find that an increased launch power causes a moderate penalty on the slave channels. Furthermore, we study the penalty from a non-zero inter-core skew.

Fast measurement method for received array antenna

The classic method of testing array antenna is measuring the beam pattern separately, which suffers from low efficiency. In this study, a fast measurement method used for received array antenna has been present. Firstly, the patterns of element antennas have been tested using multi-channel receiver. Then the entire pattern could be computed by weighting the information of elements. The information contains amplitude and phase, which could be obtained by theory or measurement.

Low-Complexity Channelizer Based on FRM for Passive Radar Multi-channel Wideband Receiver

The low-complexity channelizer is essential in passive radar multi-channel wideband receiver using array antennas. The digital filter bank is usually used to realize the channelizer. In the paper, a low-complexity channelizer based on frequency response masking (FRM) is proposed to reduce the high computational complexity of the narrow transition bandwidth filter bank. A half-band filter is used to design the prototype filter of the proposed low-complexity channelizer based on FRM. Compared to the maximally decimated filter bank, the decimation coefficient of the non-maximally decimated filter bank can be different from the number of channels, which makes the low-complexity channelizer more flexible. The low-complexity channelizer based on FRM can be directly applied to a wideband receiver without the limit of the sampling rate. The simulation and complexity analysis results show that the proposed low-complexity channelizer is correct and significantly reduces computational and hardware complexities. The proposed low-complexity channelizer makes it possible to implement passive radar multi-channel wideband receiver on a single hardware processor; thus, it is suitable to applied in passive radar multi-channel wideband receiver using array antennas.

Physical-Layer Security for Frequency Diverse Array Communication System Over Nakagami-m Fading Channels

In this paper, we propose frequency diverse array (FDA) antenna for artificial-noise (AN) aided secure communication over independent but not necessarily identical distributed Nakagami-m fading channels, where a multichannel receiver structure is adopted to address the time-variance property of FDA beampattern. Closed-form expressions for probability of nonzero secrecy capacity, secrecy outage probability, and system secrecy throughput are derived to characterize the performance of the considered system. All derivations are verified by simulation results, which show that the proposed security scheme achieves higher probability of nonzero secrecy capacity, lower secrecy outage probability, and delivers superior secrecy throughput comparing with the conventional phased-array communication scheme. This implies that FDA provides superiority for physical-layer security communication in the range dimension, whereas in the angle dimension, we show that the performance comparison between the two schemes significantly relates to the angle difference of the desired and eavesdropper direction.

Development of Software‐Defined Multichannel Receiver for EAR

AbstractThe Equatorial Atmosphere Radar (EAR) is a very high frequency Doppler radar operated with an active phased‐array antenna system at 47 MHz. It is located at the equator in Kototabang, West Sumatra, Indonesia (0.20°S, 100.32°E) and was established with a single receiving channel. Here, we present the development of a multichannel receiver system for EAR using a combination of the Universal Software Radio Peripheral X300 (USRP X300) series and GNU Radio software. Two USRP X300 devices, corresponding to four receiving channels, were synchronized using 10‐MHz reference clocks and a one‐pulse per second signal. Received signals were collected by the existing EAR antennas, fed to the USRPs for digital conversion, and then stored on a hard disk drive. Signal postprocessing was carried out to estimate wind velocity profiles. Wind profiles estimated using full correlation analysis indicate that the spaced antenna method from multichannel receivers agrees well with EAR standard observational data.

A Robust Phase-Ambiguity-Immune DOA Estimation Scheme for Antenna Array

A direction-of-arrival (DOA) estimation scheme that is immune to phase ambiguity is proposed for directional uniform circular array in the context of software defined radio based engineering implementation, where phase calibration is often required in multi-channel receiver for high-resolution, multi-source DOA estimation algorithms to work. The proposed scheme makes use of sparse signal representation technique, and is robust in the sense that no phase calibration is required when implemented by multi-channel receiver and can achieve multi-source DOA estimation when single-channel receiver is used. To facilitate the performance evaluation, a Cramer–Rao lower bound to the proposed estimation scheme is derived. Implemented by $\ell _1$ -regularized least squares program, the feasibility of the proposed scheme is validated via simulations.

DISTORTION COMPENSATION FOR WIDEBAND DIRECT RF DIGITIZATION RECEIVER

This paper studies the effect of distortions due to low noise amplifiers (LNA) nonlinearity and the compensation techniques on the multichannel wideband direct RF digitization conversion receivers. The distortion models have been analytically derived and verified by both simulation and the device measurements. The state-of-the-art techniques to reduce and compensate the LNA’s distortions in both RF and digital processing domains have been discussed in detail. This work also proposes a modified algorithm using a sub-channel reference to compensate the distortions and demonstrates the effectiveness the proposed technique using on four channel QPSK wideband receiver. Results show that the proposed linearization substantially improve the SFDR of the received signal by 20 dB (30 dB) for nearby (far-away) distortion.

The Room Temperature Multi-Channel Heterodyne Receiver Section of the PHAROS2 Phased Array Feed

This paper describes the design, fabrication, and test results of a room temperature multi-channel heterodyne receiver operating across the 2.3–8.2 GHz radio frequency (RF) band. Such a “Warm Section” (WS) receiver is part of phased arrays for reflector observing systems 2 (PHAROS2), a C-band phased array feed (PAF) demonstrator with digital beamformer for radio astronomy application. The WS receiver is cascaded to the PHAROS2 cryostat, which includes an array of Vivaldi antennas with low noise pre-amplification stages. The WS can handle up to 32 RF signals and, for each of them, realizes the operations of filtering, RF amplification and down-conversion from the RF to the 375–650 MHz intermediate frequency (IF). Also, the WS incorporates an IF-to-optical signal conversion through analogue wavelength division multiplexing IF over fiber (IFoF) and fiber-optic transmitters (OTXs). The 32-channel WS receiver consists of four eight-channel WS RF/IF modules, one local oscillator (LO) splitter module and one monitoring and control module, all hosted in a standard 6U × 19-inch rack.

Numerical Calculations of Multi-Channel Receiver Coil Array with High-Pass Spoke Coil for Parallel MRI

The proposed study reports the design and testing of spoke coil (SC), that compensates for the degradation in the g-factor that is caused by the insufficient sensitivity of the coil array along the main magnetic field direction. Electromagnetic (EM) simulations were performed to evaluate the performance of the proposed coil in a 7-T MRI system. 25-channel surface loop array and short dipole array containing SC or circular loop coil (LC) on the top of the phantom are 3D modeled. The SENSE g-factor and SNR of coil arrays are calculated and evaluated, and the quality factor (Q), scaling factor (α), and noise-corelated resistance (R) are considered. The directed effective magnetic field (B1−) generated by the SC improves the g-factor by compensating for the insufficient sensitivity information gathered by the array. However, this arrangement should be optimized to increase the available sensitivity information, depending on the type and structure of the coil elements in the array.

Monolithically integrated L-band PICs and transceiver modules with 6λ x 200 Gbps (1.2 Tbps) for C + L band communication systems.

We present monolithically integrated multi-channel coherent L-band transmitter (Tx) and receiver (Rx) photonic integrated circuits (PICs) on InP substrates. The L-band PICs are able to provide post-forward error correction (FEC), error-free operation for dual-polarization (DP) 16-QAM coherent transmission at 33 Gbaud. These transceivers operate at 200 Gbps per channel and support 1.2 Tbps aggregate capacity per 6 channel PIC. We also demonstrate in this work a C + L band communication system with two C-band superchannels (2 x 6λ) and three L-band superchannels (3 x 6λ) over a 600 km link. The received signals all have Q > 7.7 dB, which is well above the error-free threshold of the FEC used in this work.

Surface Clutter Discrimination Analysis for Radar Sounding Interferometry

This paper reports a method to analyze surface clutter discrimination for radar sounding interferometry. Nadir-looking low-frequency radar sounders cannot easily resolve off-nadir surface echoes from subsurface nadir echoes. Sounders equipped with multichannel receivers can use interferometric phase to discriminate whether a feature is at nadir or not. We developed a method to evaluate the performance of this application of interferometry and used it to analyze the selected Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) instrument on NASA's Europa Clipper mission to Jupiter's moon Europa.

Stacked Multi-Channel Receiver Architecture for Power-Efficient High-Speed Optical Links

The power supply discrepancy between advanced CMOS technology and legacy optical module leads to poor power efficiency or extra DC–DC component. A new stacked multi-channel receiver architecture and its synergetic power supply scheme for power-efficient optical links are proposed to solve the problem. Consequently, power reduction can be achieved thanks to the full utilization of available power supply headroom and the reuse of supply current. As a proof of concept, a stacked $2 \times 10$ Gb/s optical receiver with a synergetic-integrated linear multi-output regulator is implemented in 0.18- $\mu \text{m}$ CMOS technology, demonstrating the feasibility of the proposed architecture. State-of-the-art receiver performance and power efficiency are achieved.

Compressed sensing reconstruction of 7 Tesla 23Na multi-channel breast data using 1H MRI constraint

PurposeTo reduce acquisition time and to improve image quality in sodium magnetic resonance imaging (23Na MRI) using an iterative reconstruction algorithm for multi-channel data sets based on compressed sensing (CS) with anatomical 1H prior knowledge. MethodsAn iterative reconstruction for 23Na MRI with multi-channel receiver coils is presented. Based on CS it utilizes a second order total variation (TV(2)), adopted by anatomical weighting factors (AnaWeTV(2)) obtained from a high-resolution 1H image. A support region is included as additional regularization. Simulated and measured 23Na multi-channel data sets (n = 3) of the female breast acquired at 7 T with different undersampling factors (USF = 1.8/3.6/7.2/14.4) were reconstructed and compared to a conventional gridding reconstruction. The structural similarity was used to assess image quality of the reconstructed simulated data sets and to optimize the weighting factors for the CS reconstruction. ResultsCompared with a conventional TV(2), the AnaWeTV(2) reconstruction leads to an improved image quality due to preserving of known structure and reduced partial volume effects. An additional incorporated support region shows further improvements for high USFs. Since the decrease in image quality with higher USFs is less pronounced compared to a conventional gridding reconstruction, proposed algorithm is beneficial especially for higher USFs. Acquisition time can be reduced by a factor of 4 (USF = 7.2), while image quality is still similar to a nearly fully sampled (USF = 1.8) gridding reconstructed data set. ConclusionEspecially for high USFs, the proposed algorithm allows improved image quality for multi-channel 23Na MRI data sets.