Non-reciprocal coupling network for beam-steering coupled oscillator arrays

A non-reciprocal coupling network for beam-steering coupled oscillator arrays (COAs) is investigated. It is shown that this non-ferrite circuit based on the non-reciprocal behaviour of microwave transistor amplifiers generates explementary phases between adjacent coupled oscillators. Thus, this coupling network can be used to increase the array stability while extending the achievable scanning range. Numerical simulations of a multistage coupling network have shown the possibility of obtaining non-reciprocal coupling phases up to +/- 180 degrees with transmission coefficients better than -2 dB. The circuit is also useful for compensating the reciprocal coupling effect between the antenna elements. It has been shown numerically that a multistage coupling network leads to non-reciprocal coupling phases up to +/- 180 degrees with transmission coefficients better than -7.5 dB for a weakly COA of patch antennas at 10 GHz. A single-stage circuit with non-reciprocal coupling phases of +/- 1758 was designed, fabricated and tested. Numerical simulations of the circuit show non-reciprocal coupling phases of +179.5 degrees and -175.1 degrees at 10 GHz, while measured results show non-reciprocal coupling phases of +172.7 degrees and -168.6 degrees at 9.920 GHz.