Mainlobe Width Reduction Using Linear and Nonlinear Frequency Modulation

High range resolution can be achieved by various methods in a radar system. Simple pulse systems are narrow band, easiest and least expensive to maintain, but one can achieve only limited resolution. To achieve good range resolution pulse compression technique giving low range sidelobes is employed in radar and sonar. Pulse compression is accomplished by employing phase modulation and frequency modulation. Bi-phase coded waveform employs phase modulation techniques. The Barker codes are the only known bi-phase codes with minimum sidelobes. In this paper, linear frequency modulation (LFM) and nonlinear frequency modulation (NLFM) are introduced in the bi-phase coded waveforms and their effect on the sidelobe levels, mainlobe width, Doppler tolerance are studied.