A Two-Stage Wideband RF Cancellation of Coupled Transmit Signal for Bi-Static Simultaneous Transmit and Receive System

Abstract

Wireless technology is growing at a fast rate to accommodate the expanding user demands. Currently, the radio frequency (RF) spectrum is overcrowded. Hence, it is more susceptible to signal fratricide and interference. To enhance spectrum access, in-band full duplex systems are implemented to achieve simultaneous transmission and reception (STAR) and double the spectral efficiency. However, STAR systems require suppression of the high power transmit signals that can leak into the receiver chain. This type of self-interference (SI) can significantly reduce the receiver.s dynamic range and often leads to its desensitization. Therefore, successful STAR implementation requires considerable isolation between the transmitter and receiver to reduce the SI signal. To do so, RF self-interference cancellation (RFSIC) stages are considered. In this paper, we present a two-stage SIC system that includes transmit and receive antennas isolation and RFSIC filter stages. Notably, the isolation between the transmit and receive antennas is based on a novel symmetric suppression technique. The RFSIC filter is based on a hybrid finite impulse response (FIR) filter and resonator architecture. Adding a resonator to the FIR filter provides improved matching to approximate and suppress the direct SI coupling. Our design achieves ∼52 dB isolation on average across a 500 MHz bandwidth (viz. 1-1.5 GHz) in simulation. Simulation results show a minimum cancellation of 41 dB and a maximum cancellation of 65 dB. A prototype was fabricated and tested, showing an average of ∼ 44 dB cancellation which is in good agreement with our simulation.INDEX TERMS Coupling signal, in-band full duplex (IBFD), STAR, self-interference cancellation (SIC).

Wideband, Low Profile Coupling Suppression Circuit for Simultaneous Transmit and Receive System Based on Hybrid Finite Impulse Response and Resonator Topology

“…3. Details of the antenna design, fabrication, and testing are provided in our previous work [23]. Figs.…”

“…In our previous study, we developed a novel hybrid 6tap FIR and resonator design to achieve >25dB cancellation across 500MHz [23]. In this paper, we extend the design of our FIR-resonator circuit [23], depicted in Fig. 2, to operate across 800MHz of bandwidth.…”

Improving Isolation in Monostatic Simultaneous Transmit and Receive Systems Using a Quasi-Symmetrical Self-Interference Cancellation Architecture

“…However, with the rise and development of 5G and 6G technologies [3], [4], [5], systems able to simultaneous transmit and receive, and hence double the spectral efficiency, have become a necessity with the remarkably congested Radio Frequency (RF) spectrum. As such, STAR systems with high Tx/Rx isolation [6] is a challenge that must be tackled swiftly to alleviate the overcrowded RF spectrum. A failure to do so implies an increased spectral vulnerability to signal fratricide and interference, as well as falling short to accommodate the growing number of users, of both humans and connected machines.…”

Development of a single LMS loop three channels analog adaptive co-site interference cancelling system

“…In wireless communication, the in-band full duplex (IBFD) radio was proposed to exploit the scarce frequency resources [ 21 ]. Self-interference (SI) cancellation, a related technology, has been extensively explored to enable transceivers to broadcast and receive signals in the same frequency range at the same time [ [22] , [23] , [24] , [25] , [26] , [27] , [28] ]. The analog domain cancellation of SI is particularly important for preventing receiver front-end saturation.…”