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This paper presents the design results for a self-interference canceller (SIC) based on a symmetric delay-line radio frequency finite impulse response (RF-FIR) filter with a ladder structure. The proposed SIC effectively removes self-interference signals in the receiver caused by the low isolation of the circulator applied to the monostatic radar front end and the impedance mismatch of the antenna. Consequently, it enhances the isolation between the transmitter and receiver. The proposed filter consists of six taps with adjustable sizes and phases. The phase-delay values for each filter tap are implemented at a reference frequency of 3.1 GHz. The measurement results demonstrate that the proposed SIC achieves over 25 dB suppression of self-interference signals in the frequency range of 3.05 to 3.22 GHz. When applied to a monostatic radar transceiver with an RF circulator, it exhibits isolation strength of over 50 dB in the frequency range of 3.04 to 3.22 GHz. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the effect of mobility on the performance of full-duplex radio. For this, we implement a full-duplex radio prototype using a software-defined radio that is powered by a battery and can thus function in mobile environments. In addition, we compare the performance of self-interference cancellation schemes for two cases considering multi-antenna based full duplex radio and circulator based full duplex radio, respectively. Finally, we show a negative effect of mobility on the self-interference cancellation performance of the full-duplex radio system, and analyze the effect of the update period of the self-interference cancellation filter on the performance. In particular, when the update period is reduced by about 1000 times, the power of self-interference is reduced by 5.7dB for circulator-based full-duplex radio and 3.1dB for both antenna-based full-duplex radio. [ABSTRACT FROM AUTHOR]