arXiv subjects

Leonid Belostotski

Publications and source records attributed to Leonid Belostotski.

8 recordsLinked to original sources

arXiv2026

The Anatomy of RF Chains: Metrics, Measures, and Operating Efficiency

In 1958, Haus and Adler [1] introduced the concept of noise measure. Noise measure is a single quantitative metric that provides a comprehensive basis for comparing devices (individual circuits or outcomes of optimization iterations) in terms of their contribution to overall system noise by incorporating both noise factor and available power gain. Unlike noise factor alone, which reflects how much a device degrades the signal-to-noise ratio, noise measure captures the trade-off between noise and gain, making it a system-aware metric. This distinction is especially important when comparing devices in multistage systems, where both parameters jointly influence the overall system noise. Building on Haus and Adler's work, this article aims to advance RF system design by extending traditional device metrics, such as noise factor and noise measure, with new system-aware metrics: linearity, dynamic range, power efficiency, and waste measures. These new measures are interpretable, computable, and cascadable, making them well-suited for comparing the impact of individual devices or tracking the convergence of circuit design iterations on overall system-level performance. Additionally, a new metric--operating efficiency--is introduced, which unifies power efficiency, dynamic range, and data rate by incorporating signal statistics and variability in communication circuits and systems. Operating efficiency enables robust evaluation of devices under realistic and transient operating conditions, including interference, modulated signals, and adaptive modulation schemes.

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arXiv2026

Overview of the Canadian Hydrogen Observatory and Radio Transient Detector (CHORD) Project

The Canadian Hydrogen Observatory and Radio-transient Detector (CHORD) is a next-generation wideband radio interferometer currently being constructed and commissioned at the Dominion Radio Astrophysical Observatory in British Columbia, Canada. CHORD is designed for precision 21\,cm cosmology, fast radio transient discovery, spectral line galaxy surveys, and pulsar science using a highly redundant large-N, small-diameter drift-scan array architecture. The telescope consists of a 512-element core array of 6\,m dishes operating from 300--1500\,MHz in drift-scan mode, together with two 64-dish outrigger stations located at the Hat Creek Radio Observatory and the Green Bank Observatory for long-baseline transient localization. The instrument supports multiple simultaneous digital backends for interferometric correlation, FRB detection, pulsar beamforming, and high spectral resolution surveys. CHORD is designed with an emphasis on precision beam control and stable instrumental response, incorporating lessons learned from the Canadian Hydrogen Intensity Mapping Experiment (CHIME) while providing a substantial increase in sensitivity. Initial performance has been evaluated using a three-dish engineering array, and a 64-dish pathfinder array is currently being commissioned. The full array will be commissioned in 2028.

astro-ph.IM↗

arXiv2025

0.3-to-1.5-GHz LNA with Wideband Noise and Power Matching for Radio Astronomy

This paper presents a low-noise amplifier (LNA) that was developed for a new radio telescope comprised of 512 parabolic dish antennas. The LNA closely interfaces to a custom-made antenna feed with an impedance co-designed to provide noise matching over a 5:1 bandwidth. Additionally, a method of broadband noise and power matching that allows the input impedance to be controlled independently from the optimum signal-source impedance to achieve minimum noise is also discussed. When measured in a 50-Ωsystem, the LNA exhibits a return loss (RL) of > 8 dB between 0.32 to 1.5 GHz, S21 of 32 dB \pm 1.2 dB, IP1dB > -37 dBm, and IIP3 > -20 dBm. Noise parameter measurements show Tmin \approx 13 \pm 4K and noise temperatures T50Ω \approx 18 \pm 6K between 0.5 to 1.4 GHz.

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arXiv2025

General Framework for Array Noise Analysis and Noise Performance of a Two-Element Interferometer With a Mutual-Coupling Canceler

This article investigates the noise performance of a two-element phased array and interferometer containing a recently introduced self-interference canceler, which in the context of this work acts as a mutual-coupling canceler. To this end, a general framework is proposed to permit noise analysis of this network and a large variety of other networks. The framework-based numerical analysis for a two-element-phased array shows that the addition of the canceler significantly increases the beam-equivalent noise temperature. For a two-element interferometer used in cosmology, this increase in noise temperature is still acceptable as the sky noise temperature in the 20-to-200 MHz band is high. When used in an interferometer, the canceler provides the ability to null mutual coherence at the interferometer output. The ability to provide matching to reduce the sensitivity of the null in mutual coherence to the phase of the 90deg hybrids in the canceler is discussed.

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arXiv2024

Towards a Low-SWaP 1024-beam Digital Array: A 32-beam Sub-system at 5.8 GHz

Millimeter wave communications require multibeam beamforming in order to utilize wireless channels that suffer from obstructions, path loss, and multi-path effects. Digital multibeam beamforming has maximum degrees of freedom compared to analog phased arrays. However, circuit complexity and power consumption are important constraints for digital multibeam systems. A low-complexity digital computing architecture is proposed for a multiplication-free 32-point linear transform that approximates multiple simultaneous RF beams similar to a discrete Fourier transform (DFT). Arithmetic complexity due to multiplication is reduced from the FFT complexity of $\mathcal{O}(N\: \log N)$ for DFT realizations, down to zero, thus yielding a 46% and 55% reduction in chip area and dynamic power consumption, respectively, for the $N=32$ case considered. The paper describes the proposed 32-point DFT approximation targeting a 1024-beams using a 2D array, and shows the multiplierless approximation and its mapping to a 32-beam sub-system consisting of 5.8 GHz antennas that can be used for generating 1024 digital beams without multiplications. Real-time beam computation is achieved using a Xilinx FPGA at 120 MHz bandwidth per beam. Theoretical beam performance is compared with measured RF patterns from both a fixed-point FFT as well as the proposed multiplier-free algorithm and are in good agreement.

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arXiv2023

Low-cost, Low-loss, Ultra-wideband Compact Feed for Interferometric Radio Telescopes

We have developed, built, and tested a new feed design for interferometric radio telescopes with "large-$N$, small-$D$" designs. Those arrays require low-cost and low-complexity feeds for mass production on reasonable timescales and budgets, and also require those feeds to be compact to minimize obstruction of the dishes, along with having ultra wide bands of operation for most current and future science goals. The feed presented in this paper modifies the exponentially tapered slot antenna (Vivaldi) and quad-ridged flared horn antenna designs by having an oversized backshort, a novel method of maintaining a small size that is well-suited for deeper dishes ($f/D\leq 0.25$). It is made of laser cut aluminum and printed circuit boards, such that it is inexpensive ($\lesssim$ 75 USD per feed in large-scale production) and quick to build; it has a 5:1 frequency ratio, and its size is approximately a third of its longest operating wavelength. We present the science and engineering constraints that went into design decisions, the development and optimization process, and the simulated performance. A version of this feed design was optimized and built for the Canadian Hydrogen Observatory and Radio-transient Detector (CHORD) prototypes. When simulated on CHORD's very deep dishes ($f/D=0.21$) and with CHORD's custom first stage amplifiers, the on-sky system temperature $T_\mathrm{sys}$ of the complete receiving system from dish to digitizer remains below 30 K over most of the 0.3-1.5 GHz band, and maintains an aperture efficiency $η_\mathrm{A}$ between 0.4 and 0.6. The entire receiving chain operates at ambient temperature. The feed is designed to slightly under-illuminate the CHORD dishes, in order to minimize coupling between array elements and spillover.

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arXiv2023

Fano-Qubits for Quantum Devices with Enhanced Isolation and Bandwidth

Magneto-optical isolators and circulators have been widely used to safeguard quantum devices from reflections and noise in the readout stage. However, these devices have limited bandwidth, low tunability, are bulky, and suffer from high losses, making them incompatible with planar technologies such as circuit QED. To address these limitations, we propose a new approach to quantum non-reciprocity that utilizes the intrinsic nonlinearity of qubits and broken spatial symmetry. We show that a circuit containing Lorentz-type qubits can be transformed into Fano-type qubits with an asymmetric spectral response, resulting in a significant improvement in isolation (up to 40 dB) and a twofold increase in spectral bandwidth (up to 200 MHz). Our analysis is based on realistic circuit parameters, validated by existing experimental results, and supported by rigorous quantum simulations. This approach could enable the development of compact, high-performance, and planar-compatible non-reciprocal quantum devices with potential applications in quantum computing, communication, and sensing.

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arXiv2020

Design Equations for a Closely-Spaced Two-Element Interferometer Including Internal Noise Coupling

We present design equations for a two-element closely-spaced interferometer for measuring the noise temperature of a uniform sky. Such an interferometer is useful for observing highly diffuse radio sources such as the Milky Way and Cosmological signals. We develop a simple equivalent circuit based on radiophysics and antenna theory to describe the interactions between key design parameters such as antenna self and mutual impedance and noise parameters of the receiver; the latter is considered internal noise. This approach straightforwardly facilitates design studies as the response of the uniform signal and the systematic error due to internal noise coupling can be analyzed using the same equivalent circuit. The equivalent circuit shows that mutual coherence due to internal noise coupling is non-negligible and an inherent property of a closely-spaced interferometer. A realistic example design involving two closely-spaced horizontal dipoles over a lossy ground for Cosmological signal detection from 50 to 100 MHz is discussed as an illustration.

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