Ideally, if we wanted both long detection range and fine range resolution, we would transmit extremely narrow pulses of exceptionally high peak power. But there are practical limits on the level of peak power one can use. To obtain long detection ranges at PRFs low enough for pulse delay ranging, fairly wide pulses must be transmitted. One solution to this dilemma is pulse compression. That is, transmit internally modulated pulses of sufficient width to provide the necessary average power at a reasonable level of peak power; then, 'compress' the received echoes by decoding their modulation. This chapter explains the two most common methods of coding - linear frequency modulation and binary phase modulation. It also briefly describes a third method, polyphase modulation.

Chapter Contents:

• Linear Frequency Modulation (Chirp)
• Binary Phase Modulation

Inspec keywords: linear codes; phase modulation; radar resolution; pulse compression; modulation coding; binary codes; echo; FM radar; decoding

Other keywords: binary phase modulation; linear frequency modulation; range resolution; modulation decoding; polyphase modulation; echo; pulse delay ranging; PRF; detection range; pulse compression; chirp; modulated pulse transmission

Subjects: Electromagnetic compatibility and interference; Radar equipment, systems and applications; Modulation and coding methods; Signal processing and detection