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Narrowband high temperature superconducting receiver for low frequency radio waves

D. Reagor

Published Jan 23, 2023• 0 citations
OpenAlex

Abstract

An underground communicating device has a low-noise SQUID using high temperature superconductor components connected to detect a modulated external magnetic flux for outputting a voltage signal spectrum that is related to the varying magnetic flux. A narrow bandwidth filter may be used to select a portion of the voltage signal spectrum that is relatively free of power line noise to output a relatively low noise output signal when operating in a portion of the electromagnetic spectra where such power line noise exists. A demodulator outputs a communication signal, which may be an FM signal, indicative of a modulation on the modulated external magnetic flux.

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An underground communicating device has a low-noise SQUID using high temperature superconductor components connected to detect a modulated external magnetic flux for outputting a voltage signal spectrum that is related to the varying magnetic flux. A narrow bandwidth filter may be used to select a portion of the voltage signal spectrum that is relatively free of power line noise to output a relatively low noise output signal when operating in a portion of the electromagnetic spectra where such power line noise exists. A demodulator outputs a communication signal, which may be an FM signal, indicative of a modulation on the modulated external magnetic flux.
We have developed a receiver for low-frequency radio waves using high-temperature superconducting quantum interference devices (SQUIDs). The primary application of such a receiver is to communicate in underground areas where the overburden results in significant losses at the usual radio frequencies. The receiver constructed consists of a SQUID, a small dewar, control electronics, and a battery pack. The SQUID was fabricated in our laboratory using an edge junction technology, discussed in previous publications. For this work we increased the effective area by including a standard galvanically coupled pickup loop. We have investigated background noise spectra and found that the low noise door of the SQUIDs can be fully utilized in the receiver, provided that the signals be encoded with a bandwidth narrower than the 60 Hz spacing between powerline harmonics. The most significant advantage of SQUIDs for this application is that they allow the compact construction of three-axis receivers that are necessary to overcome a dominant source of vibrational or motional noise.
The authors have developed a method for communicating in underground areas with voice. This system utilizes low-frequency electromagnetic radiation and high-temperature superconducting quantum interference devices (SQUIDs) as receivers. The system is primarily used to communicate in underground areas using through-the-earth electromagnetic waves. The underground areas are typically mines, but the application is not restricted to that purpose. The communication channel is being used to send voice that has been digitally compressed. Typical rock masses do not allow conventional radio frequency electromagnetic waves to penetrate significant distances. Here, the authors use carrier frequencies of a few kilohertz that penetrate hundreds of meters into rock masses. They are using low-noise broadband superconducting receivers and have established that the signals propagate several hundred meters with modest power levels. Audio has been successfully received at distances in excess of 100 m through solid rock.
The invention is directed to a device and method to engineer the superconducting transition width by suppressing the phonon populations responsible for the Cooper-pair decoherence below the superconducting transition temperature via phononic bandgap engineering. The device uses phononic crystals to engineer a phononic frequency gap that suppresses the decohering thermal phonon population just below the Cooper-frequency, and thus the normal conduction electron population. For example, such engineering can relax the cooling requirements for a variety of circuits yielding higher operational quality factors for superconducting electronics and interconnects.
A method is provided for sensing a magnetic field in a magnetic gradiometer of the kind in which pump light and light constituting an optical carrier traverse first and second atomic vapor cells that contain host atoms and that are separated from each other by a known distance. According to such method, the host atoms are prepared in a coherent superposition of two quantum states that differ in energy by an amount that is sensitive to an ambient magnetic field. Modulation of the optical carrier in the respective cells gives rise to sidebands that interfere to generate a beat frequency indicative of the magnetic field gradient. The host atoms are prepared at least in a mode that allows measurement of ambient magnetic field components perpendicular to the axis of the pump light. In such mode, the host atoms are spin-polarized by pump light while subjected to a controlled magnetic field directed parallel to the pump beam, and then the controlled magnetic field is adiabatically extinguished.
Superconducting quantum interference devices (SQUIDs) are promising for detection of extremely weak power regimes for the Internet of Things and long-distance satellite networks. In low-frequency magnetic signal measurements, it has demonstrated superior performance over the traditional systems. We review the resistively and capacitively shunted junction model of dc SQUIDs and investigate its transfer function to magnetic flux signals while taking thermal fluctuation into account. We numerically evaluate the influence of bias current and bias flux signal to determine the operating parameters of the device. The performances related to SQUID ring inductance operating at 4.2 K and 77 K are demonstrated. Combined with common radio frequency front-end modules, including low-noise amplifier and low-pass filter, we evaluate the bit-error-rate performance of the system under different inductance values and inferred that the sensitivity of the system can reach −99 dBm at 100 MHz bandwidth.