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In this paper, we analyze properties of the noise in the time-frequency representations. We show that time-frequency representations can be improved by denoising. However, the task and conditions in which noise removal should be performed are not typical for filter design. We demonstrate that leaked noise has specific statistics and spatial correlation characteristics. Some opportunities of denoising...
A likelihood function for a multi-sensor, passive sonar Bayesian tracker may use data directly from the array elements or, alternatively, from the output of a conventional beamformer (CBF). Here, we compare the performance of a Bayesian tracker when using element- versus CBF-level data. We observed that, provided the CBF's beams are sufficiently closely spaced, the tracker's performance with CBF-level...
We present a Bayesian tracker for broadband passive sonar. The Bayesian formulation in Cartesian coordinates facilitates multi-sensor fusion of a distributed field of receivers. The likelihood functions used in the tracker are formulated so as to leverage a priori knowledge about the signal-of-interest's bandwidth and spectral mask when available. The use of a priori knowledge about the signal enables...
In this paper, the problem of estimating the directions of arrival (DOAs) for an unknown number of sound sources is addressed using a microphone array. In outdoor environments, the reverberation is not considered, so the pure delay mixture model is typically adopted here. Since the sound signal is usually wide-band and non-stationary, the Short Time Fourier Transform (STFT) is employed. However in...
In this paper, we look to address the problem of estimating the dynamic direction of arrival (DOA) of a narrowband signal impinging on a sensor array from the far field. The initial estimate is made using a Bayesian compressive sensing (BCS) framework and then tracked using a Bayesian compressed sensing Kalman filter (BCSKF). The BCS framework splits the angular region into N potential DOAs and enforces...
Differential front-end design presents a good prospect to be integrated with differential beamformer inputs without a transformer needed otherwise for a single-ended front-end design. A front-end solution with a complete differential configuration is presented. The potential advantages of this design are: planar antenna elements mean a lower cost; differential LNAs in close proximity to the antenna...
A design of conjugated resistive frequency selective surfaces with capacitively coupled phased Fractal Octagonal Rings Array (FR-ORA) has been proposed for low-frequency aperture array radio astronomy. The presence of the resistive loading has expanded the bandwidth of the array to a ratio of 8:1, but at the expense of its radiation efficiency performance (at the high end of its operating frequency)...
Recent experimental results for the sensitivity of aperture arrays at room temperature show 40 K array noise temperatures over the frequency range from 1000 MHz to 1500 MHz. Further reduction of array noise temperature is important to comply with the SKA sensitivity requirements at affordable cost. Furthermore the frequency range should be extended to a lowest frequency of 500 MHz, in order to meet...
Giant Ukrainian Radio Telescope (GURT) is a low-frequency one with active phased antenna array, which is being built in Ukraine in addition to the existing UTR-2 radio telescope. In this paper we consider the signal-to-noise ratio in active antenna, which is used as an element of GURT radio telescope antenna array. The sensitivity of the element mainly determines the sensitivity of not only the entire...
Phased-array feeds (PAFs) can provide multi-beam capability for reflector antennas at microwave bands. For radio astronomy applications it is critical that the effective noise temperature of the PAF system be as low as practicable to be competitive with more conventional optimised single-beam systems. We describe our efforts to reduce the noise of a Vivaldi-element array by three means. The first...
Noise parameter measurements of six candidate transistors for a Square Kilometer Array (SKA) low-noise amplifier (LNA) are presented. They provide reliable data in the frequency range where some low-noise transistors are inadequately characterized. The results of these measurements inform the design of an LNA for SKA1-Survey Band 2 with measured minimum noise temperature of 21 K.
The SKA dishes will be used with single pixel feeds (resulting in a single on-axis main beam) as well as phased array feeds that will generate multiple offset beams. The final optics will be shaped to improve the performance of the single pixel systems. This shaping may, however, be to the detriment of the offset beams of the multi-beam systems. It is important to understand the extent of this. A...
We discuss the readout of a kind of novel 64-pixel quantum dots photodetector array which has high current gains but low dark currents and thus has high signal to noise ratio. Photocurrent spectrum tests demonstrated that the photodetector shows excellent light absorption from 600nm to 900nm both in room temperature (300K) and liquid nitrogen temperature. High gain-adaptive capacitive trans-impedance...
The square and rectangular shape of the pixels in the digital images for sensing and display purposes introduces several inaccuracies in the representation of digital images. The major disadvantage of square pixel shapes is the inability to accurately capture and display the details in the objects having variable orientations to edges, shapes and regions. This effect can be observed by the inaccurate...
A low-noise cryogenic phased array feed (PAF) is in development for the Green Bank Telescope (GBT). The feed consists of electrically small elements tuned to operate near 1.4 GHz and optimized for active impedance matching to cooled front end low noise amplifiers (LNAs). A prototype cryogenic PAF with analog fiber link, down-converters and streaming data acquisition system was recently tested on the...
Selected results of the optics analysis of the proposed offset Gregorian reflector with Phased Array Feed (PAF) are presented. The approach used to analyze the phased array feed with the Gregorian reflector is described.
We discuss the theory and implementation of phased array receivers in the focal plane of a telescope as applied to the mm-wave band. Simulated performance and construction details are given for a 64 element, 70–95 GHz array receiver for use on the Green Bank Telescope (GBT).
This paper presents a system consisting of an array of thin-film microphone channels on glass, which can be formed on large substrates. Each microphone channel consists of a polyvinylidene difluoride (PVDF) piezoelectric transducer as well as amplifier and scan circuits basedon amorphous-silicon (a-Si) thin-film transistors (TFTs). The scan circuits multiplex signals from multiple channels to a CMOS...
The development of next-generation networks has been driven by a number of use cases aimed at supporting innovative applications and services. Among these drivers the Internet of Things has gained momentum due to its potential to leverage Machine Type Communications (MTC), a term used to denote machine-centered communications among sporadic, bursty traffic generating devices. While scalability issues...
This paper presents a system consisting of an array of thin-film microphone channels on glass, which can be formed on large substrates. Each microphone channel consists of a polyvinylidene difluoride (PVDF) piezoelectric transducer as well as amplifier and scan circuits based on amorphous-silicon (a-Si) thin-film transistors (TFTs). The scan circuits multiplex signals from multiple channels to a CMOS...
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