How does pulse compression improve the range resolution and sensitivity of a radar?

Pulse compression allows a radar to achieve the range resolution of a short pulse while transmitting the energy of a long pulse. The transmitted pulse is modulated (in frequency or phase) across a wide bandwidth B during a long pulse duration T. The matched filter in the receiver compresses the long pulse to a width of 1/B, providing: range resolution ΔR = c/(2B), and processing gain = T×B (the time-bandwidth product). A 10 μs chirp with 10 MHz bandwidth: ΔR = 15 m, processing gain = 100 (20 dB). Without pulse compression: achieving 15 m resolution requires a 0.1 μs pulse, which has 100× less energy. Common waveforms: linear FM (chirp): frequency sweeps linearly across bandwidth B during pulse time T. Simple to generate, robust, and widely used. Phase-coded (Barker, polyphase): the pulse is divided into sub-pulses, each with a specific phase. Provides low range sidelobes.