Broadband Simultaneous Transmit and Receive

To date, Simultaneous Transmit and Receive (STAR) solutions have primarily relied on a circulator in the RF frontend, paired with digital signal processing (DSP) to suppress the approximately known transmitted signal. These techniques have demonstrated only limited isolation and bandwidth and struggle to remove non-linear harmonics and transmit noise. Moreover, the limited isolation of circulators puts a heavy burden on digital techniques, in turn driving up the hardware requirements (e.g. ADC precision) of the radio. Thus a critical requirement is increased suppression of coupled self-interference at the RF stages, to reduce modification in the radio. The objective of this proposal is to enable the in-place upgrade of legacy systems to realize wideband full-duplex STAR, with minimal modification of the existing radio hardware. Critical to our approach is increased suppression of coupled self-interference (including harmonics and noise) at the antenna and RF stage (prior to LNA and digitization). Specifically, we propose three stages of cancellation to achieve >110dB isolation over >100MHz bandwidth: 1) high isolation multi-port antennas, 2) self-interference cancelling RF filter, and 3) digital signal suppression. Notably increased RF isolation enables higher power applications (e.g. jamming) while simultaneously lending itself to low cost, maximum linearity, and high integration.