Techniques for Achieving High Isolation in RF Domain for Simultaneous Transmit and Receive

Satheesh Bojja Venkatakrishnan,Elias A Alwan,Toshifumi Nakatani,Alexander D Johnson,Alexander Hovsepian,John L Volakis

doi:10.1109/ojap.2020.3009185

Abstract

With the growth of wireless data traffic, additional spectrum is required to meet consumer demands. Consequently, innovative approaches are needed for efficient management of the available limited spectrum. To double the achievable spectral efficiency, a transceiver can be designed to receive and transmit signals simultaneously (STAR) across the same frequency band. However, due to the coupling of the high power transmitted signal into the collocated receiver, the receiver’s performance is degraded. For successful STAR realization, the coupled high-power transmit (Tx) signal should be suppressed by 100-120 dB over the entire operational bandwidth. So far, most STAR implementations are narrowband, and not useful for ultra wideband (UWB) communications. In this paper, we present a review of novel approaches employed to achieve improved cancellation across wide bandwidths in RF and propagation domains. Both single and multi-antenna systems are considered. Measurements show an average cancellation of 50 dB using two stages of RF signal cancellation.

Highlights

N EXT generation mobile and wireless communication systems (5G and beyond) will require increasingly high data rates to support the growing volume of data exchange and expected integration with Internet of Things (IoT) sensors
With a single antenna radio, full duplex is achieved either by employing time division duplexing (TDD) or frequency division duplexing (FDD). These radios employ a single antenna for transmission and reception using a single feed network that divides the transmitter and receiver circuits as depicted in Fig. 2 [24]–[27]
To improve the achieved stage-1 isolation, we propose an antenna agnostic feed network technique that can provide

Summary

INTRODUCTION

N EXT generation mobile and wireless communication systems (5G and beyond) will require increasingly high data rates to support the growing volume of data exchange and expected integration with Internet of Things (IoT) sensors. Recent STAR realizations [6], [12]–[15], [15]–[22] have successfully demonstrated 80 - 110 dB interference suppression This was achieved over a narrow bandwidth (< 80 MHz) using not more than three cancellation stages. With a single antenna radio, full duplex is achieved either by employing time division duplexing (TDD) or frequency division duplexing (FDD) These radios employ a single antenna for transmission and reception using a single feed network that divides the transmitter and receiver circuits as depicted in Fig. 2 (left) [24]–[27]. We present techniques to suppress direct interference components using the first 2 cancellation stages for single antenna and multi-antenna radios.

SINGLE ANTENNA RADIOS

STAGE-2

CONCLUSION