Simultaneous Reception and Scanning Using Complex IF Radio Architectures

Two different radio architecture are proposed that allow for simultaneous reception on one frequency and scanning on another frequency using only one receiver chain. This can for instance be used to scan for an alternative frequency when a handover is required in a cellular system. The architectures are based on that the signal is down-converted to a complex intermediate frequency (IF) before being down-converted to baseband. The second mixer is made adjustable so that any desired image rejection ratio (IRR) can be obtained. By adjusting the IRR and estimate how the signal quality of the desired signal is affected, the signal power at the image frequency can be accurately estimated. Based on simulations of an OFDM system with LTE-like parameters, it is found that if a degradation of 0.5-1 dB is acceptable for the desired signal, a scanning time of 1-2 ms suffice for accurate power estimation.