Impact of transceiver IQ imbalances on cooperative jamming suppression in confidential communications

A CJ (cooperative jamming) masked secure communication architecture was proposed for confidential communications when malicious interference and illegal eavesdropping coexist. Thereinto, the FH (frequency-hopping) technology was adopted in the transceiver to avoid malicious interference, and the CJ technology was employed to block illegal eavesdropping. Nevertheless, the proposed architecture employs a wide frequency bandwidth, which will raise nonnegligible IQ (in-phase and quadrature) imbalances at the transceiver oscillators. In view of this, the mathematical modeling was conducted on the signal distortion caused by the imbalance of the receiving and transmitting IQ channels, a mathematical expression for SDNR (the signal to distortion-plus-noise ratio) at the receiver was provided, and a closed-form expression for the system CJSR (CJ suppression ratio) was derived. Simulation results show that the power of the signal distortion raised by transceiver IQ imbalance is much greater than that of the thermal noise. Besides, both the SDNR and CJSR will decline sharply as the transceiver IQ imbalance deteriorates, and when the magnitude and phase imbalance are 0.95 and π/50 respectively, both the SDNR and CJSR performance will deteriorate 47 dB.