Direct Conversion Receiver Gain Switching With DC Transient Suppression

The patent applies dynamics by making the low cutoff frequencies of the high-pass filters variable rather than fixed. The control circuit dynamically adjusts the low cutoff frequencies based on the gain switching state: setting them to a first value (higher) during gain switching to suppress transient responses, and to a second value (lower) during normal operation to allow baseband signals to pass. This dynamic adjustment resolves the contradiction between signal transmission capability and transient response stability.

The patent applies preliminary action by preemptively adjusting the low cutoff frequencies of the high-pass filters to a higher value before gain switching occurs. The control circuit detects when gain switching is about to happen and proactively changes the filter characteristics to suppress transient responses before they can be amplified by the high-gain amplifiers. This prevents the harmful transient responses from occurring in the first place, rather than trying to mitigate them after amplification.

The patent resolves this contradiction by making the high-pass filters dynamic with variable low cutoff frequencies. During normal operation, the low cutoff frequencies are set to a second value that is sufficiently small to allow baseband signals to pass while still providing some DC offset suppression. During gain switching, the low cutoff frequencies are temporarily increased to a first value to block DC offset voltage and suppress transient responses. This dynamic behavior allows the system to achieve both DC offset suppression and baseband signal transmission capability at different times.