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Same Frequency Simultaneous Transmit and Receive Radio for Military and Commercial Applications

Description:

TECHNOLOGY AREA(S): Electronics 

OBJECTIVE: US Army RF systems, such as communication networks and radar, encounter an increasingly congested and contested electromagnetic spectrum. Increasing the spectral efficiency by utilizing Same Frequency Simultaneous Transmit and Receive (SF-STAR) Radios will greatly enhance Military and Commercial communications and radar systems. 

DESCRIPTION: The United States Army and Joint Services utilize tactical communication systems that are adversely affected by the recent Advanced Wireless Service spectrum auction. These systems will be required to operate in more restricted frequency bands and therefore stand to lose capacity and throughput if technology is not developed to maintain and improve spectral efficiency (defined as bits per second per Hertz, or bits/s/Hz). Current tactical communication systems are unable to simultaneously transmit (Tx) and receive (Rx) at the same radio frequency (RF), placing an inherent limitation on spectrum usage imposed by conventional duplexing and networking techniques. The purpose of this solicitation is to close this technology gap to enable more efficient use of available spectrum for affected systems in 1 – 6 GHz bands (or higher frequency bands up to and including mm-wave bands) by developing innovative prototype designs leading to mature, operationally-relevant tactical communication systems capable of same frequency full duplex functionality. Commercial systems (including WiFi, and fifth generation, 5G, systems) will benefit greatly from the development of SF-STAR radios given that spectrum is a scare resource. Developing a SF-STAR radio for commercial applications is an active research topic with no products currently available. Unlike commercial systems, Army systems operate in congested and contested hostile environments. For Army applications, SF-STAR radios require greater suppression of self-interference and external hostile uncooperative interference from jammers as well as greater bandwidth (above 80 MHz). This necessitates higher levels of linearity and dynamic range than commercial SF-STAR systems. Typically, interference suppression may be carried out in the digital domain using digital signal processing (DSP) or the analog domain. The focus of this solicitation are the analog domain techniques which can be realized using innovative multi-feed antennas, and novel RF frontend circuitry (including correlators, and non-magnetic circulators). The goal is to achieve greater than 70 dB of isolation between transmit and receive, as well as 20 dB suppression of uncooperative interferers in nearby (10% above the center frequency) bands, under practical operating conditions. DSP techniques (which are outside the scope of this solicitation) can be employed to enhance the isolation further. The SF-STAR operation should be achieved over a minimum of 100 MHz instantaneous bandwidth with a minimum transmitted output power of 23 dBm, a minimum receiver input IP3 of 10 dBm, a minimum Tx/Rx isolation of 70 dB, and a minimum jammer suppression of 20 dB in nearby bands. Higher the levels of integration are desired to reduce size weight and power (SWAP). 

PHASE I: Investigate design space and define specifications; evaluate architecture choices and trade-offs for various approaches leading to SF-STAR. Simulate chosen solution and assess operating margins. Determine minimum and maximum attainable Tx/Rx isolation, transmitted output power, receiver sensitivity, linearity, and spurious-free dynamic range, signal bandwidth, frequency of operation, and potential for implementation (including sensitivity to component tolerances, and impedance mismatch). The SF-STAR design should achieve 100 MHz bandwidth or greater, 23 dBm output power or greater, a receiver input IP3 of 10 dBm or greater, a Tx/Rx isolation of 70 dB or greater, and a jammer suppression of 20 dB or greater in nearby bands. It should tolerate process and/or component tolerances, impedance mismatch, and noise leakage from the transmitter to the receiver chain. 

PHASE II: Design, and prototype a SF-STAR radio using analog techniques based on phase I analysis, achieving 100 MHz bandwidth or greater, 23 dBm output power or greater, a receiver input IP3 of 10 dBm or greater, a Tx/Rx isolation of 70 dB or greater, and a jammer suppression of 20 dB or greater in nearby bands. The prototype should tolerate process and/or component tolerances, impedance mismatch, and noise leakage from the transmitter to the receiver chain. The prototype should be delivered to the Army at the end of phase II. 

PHASE III: Design and build a radio demonstrating SF-STAR for a specific military or commercial system that satisfies the specifications of the specific application selected; transition technology to defense and commercial applications. Identify benefits and drawbacks of the SF-STAR radio over existing systems. 

REFERENCES: 

1: Harish Krishnaswamy and Gil Zussman, "1 Chip 2x Bandwidth," IEEE Spectrum, July 2016.

2:  B Debaillie et. al., "Analog/RF Solutions Enabling Compact Full-Duplex Radios," IEEE Journal on Selected Areas in Communications, Volume 32, Issue 9, Sept. 2014.

3:  A Sabharwal et. al., "In-Band Full-Duplex Wireless: Challenges and Opportunities," IEEE Journal on Selected Areas in Communications, Volume 32, Issue 9, Sept. 2014.

KEYWORDS: Simultaneous Transmit And Receive, Full Duplex, And Radio Frequency Integrated Circuits 

CONTACT(S): 

Ali Darwish 

(301) 394-2532 

ali.m.darwish.civ@mail.mil 

Edward Viveiros 

(301) 394-0930 

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