A radar system employing a continuous wave (CW) pulse exhibits a range resolution and signal-to-noise ratio (SNR) that are both proportional to pulse width. SNR drives detection performance and measurement accuracy and is a function of the energy in the pulse. Energy and SNR are increased by lengthening the pulse. Range resolution defines a radar's ability to separate returns in range and is improved by decreasing the pulse width. An undesired relationship, coupled through the pulse width, exists between the energy in a CW pulse and the pulse's range resolution. Near the end of World War II, radar engineers applied intrapulse modulation to decouple the two quantities. Range resolution was shown to be inversely proportional to bandwidth. A waveform's bandwidth could be increased via modulation, achieving finer range resolution without shortening the pulse. Waveforms that decouple resolution and energy via intrapulse or interpulse modulation are termed pulse compression waveforms.

Chapter Contents:

• 20.1 Introduction
• 20.2 Matched Filters
• 20.3 Range Resolution
• 20.4 Straddle Loss
• 20.5 Pulse Compression Waveforms
• 20.6 Pulse Compression Gain
• 20.7 Linear Frequency Modulated Waveforms
• 20.8 Matched Filter Implementations
• 20.9 Sidelobe Reduction in an LFM Waveform
• 20.10 Ambiguity Functions
• 20.11 LFM Summary
• 20.12 Phase-Coded Waveforms
• 20.13 Biphase Codes
• 20.14 Polyphase Codes
• 20.15 Phase-Code Summary
• 20.16 Further Reading
• 20.17 References
• 20.18 Problems

Inspec keywords: radar resolution; CW radar; modulation; pulse compression; radar detection

Other keywords: radar measurement accuracy; pulse compression waveform; radar detection performance; SNR; continuous wave pulse radar system; interpulse modulation; radar engineer; pulse range resolution; signal-to-noise ratio; CW; intrapulse modulation

Subjects: Radar equipment, systems and applications; Signal detection; Modulation and coding methods