A DC offset-free ultra-wideband direct conversion receiver based on photonics

A demonstrator of DC offset-free direct conversion receiver is presented. The innovative architecture exploits optical domain up-conversion and photonic I/Q demodulation to perform a wideband scanning of the RF input spectrum avoiding bulky multiple crystal oscillators and bandpass filters. Moreover, the scheme provides a total immunity to local oscillator self-mixing and to RF-to-baseband feedthrough. The demonstrator achieves a measured DC offset lower than 50 μν and a second-order input-intercept point of 57 dBm. It also shows an operating and instantaneous bandwidth of 0.5÷10.5 GHz and 1 GHz, respectively, with linear dynamic range of 160 dB/Hz and spurious-free dynamic range of 109 dB/Hz2/3, outperforming current pure electronic direct conversion receivers. Further improvements are proposed to enhance the operating bandwidth and to reduce the size and power consumption, making the proposed direct conversion receiver suitable for practical electronic warfare applications.