Question 8-22C2

Radar systems operate at very high radio frequencies (RF) in the microwave range (GHz) and use very short pulses for high range resolution. To process these signals, a superheterodyne receiver converts the high RF to a fixed, lower intermediate frequency (IF). Radar systems require a relatively high IF for two main reasons: 1. **Bandwidth:** Short radar pulses contain a wide range of frequencies (wide bandwidth). A higher IF is better suited to accommodate these wide bandwidths without distortion, ensuring good range resolution. 2. **Image Rejection:** With RF in the GHz range, a higher IF makes it easier to design filters that effectively reject the image frequency, which is a spurious signal that can interfere with the desired reception. Options A (455 kHz) and B (10.7 MHz) are common IFs for AM and FM broadcast receivers, respectively. These frequencies are too low to provide the necessary wide bandwidth and good image rejection required for modern GHz radar systems. Option D (120 MHz) is a high frequency but 30 or 60 MHz (Option C) represents the typical and widely adopted IF for shipboard radar units, balancing performance requirements with practical design considerations.