An Efficient Digital Background Control for Hybrid Transformer-based Receivers

The design and hardware implementation of a
digital control system tailored to a hybrid transformer-based
duplexer is proposed. Working at Nyquist sampling frequency,
it finds the optimal transmit-receive isolation in about 150 μs
even when modulated signals with high PAPR (16-QAM) are
transmitted. A simple tracking algorithm, operating in background,
preserves this condition over time. Uninterrupted system
operation can be guaranteed through an auxiliary receiver with
sub-mW power dissipation, minimizing the overhead of the
entire control system. The algorithms are implemented on FPGA
to carry out the experimental validation of the full hardware
implementation. Moreover, the hardware overhead of the digital
control algorithm is analyzed, synthesizing the digital circuit
in 40-nm CMOS technology.