What is the effect of increasing front-end filter sharpness on SNR and group delay, and what is the typical trade-off?

• A. Increases SNR but reduces group delay; no trade-off.
• B. Increases out-of-band rejection (SNR) but increases group delay, potential distortion; trade-off between selectivity and real-time performance.
• C. Increases SNR and reduces group delay; no trade-off.
• D. Improves linearity; increases cost.

Answer: (B)

Sharper front-end filtering increases selectivity, which reduces out-of-band noise and interference entering the system. By better rejecting signals and noise outside the passband, the energy that stays in the band is clearer, so the in-band SNR improves.

At the same time, making the filter sharper typically means a higher-order filter. A higher-order filter introduces more group delay, meaning the different frequency components are delayed by more as they pass through the filter. In practice this also raises the risk of time-domain distortion if the phase response isn’t well controlled, and it adds latency to the processing, which can hurt real-time performance.

So the typical trade-off is better selectivity (and improved SNR in-band) at the cost of increased group delay and potential distortion, affecting real-time responsiveness.