I/Q imbalance of two-path ladder filters

The frequency-(in)dependent I/Q imbalance of analog filters is significant contributor to the tight noise budget of high-performance wireless applications, such as 802.11a wireless LANs. This paper proposes a "frequency-dependent" statistical I/Q-imbalance analysis method for two-path filters, which can be configured for both low-IF and zero-IF architectures. A 7-pole complex band-pass ladder filter is analyzed, and it shows large image rejection ratio (rms IMR > 43.7dB for 3σ). The same filter, but reconfigured as a pair of real-low-pass filters, achieved about 13dB less IMR. These results suggest a low-IF architectural choice to combat the I/Q imbalance of two-path filters.