Design of an Ultra-Wideband Zero-IF Excitation Source for Multi-Functional Integration

For the multi-functional integration system of radar, electronic warfare, and communication, a 0.3-18 GHz ultra-wideband (UWB) zero-intermediate frequency (zero-IF) excitation source is proposed in this paper. The proposed Zero-IF architecture incorporates a wideband direct digital synthesizer, an ultra-wideband I/Q modulator, and a multi-band phase-locked frequency synthesizer, which could be utilized for the generation of digital waveform from 0.3-2GHz and analog I/Q demodulation for signal from 2-18 GHz. A FPGA-based signal processing architecture is then presented for the carrier leakage cancellation with a closed-loop square-law detection and the calibration of I/Q mismatch with a minimum mean-square error compensator using matrix inversion. Results show that the maximum instantaneous bandwidth of the excitation source is up to 3GHz, and the calibrated image rejection ratio and carrier rejection ratio respectively exceed 40dBc and 35dBc, which is feasible for the UWB transmit system in multi-functional integrated applications.