Side-looking sonar or radar using phase difference monopulse techniques. Coherent and noncoherent applications

Although coherent synthetic apertures are common in radar, coherent apertures in sonar are difficult to synthesise with a single moving element owing to positional uncertainty and the very imperfect nature of the sonar propagation medium. The two techniques described in the paper show how a pair of receivers coupled in a phase-difference or phase-comparison monopulse configuration can reduce the effect of random fluctuations on the image produced by a side-looking terrain mapping system. To test this technique experimentally, a two-channel air sonar was built, coupled in a phase-difference monopulse configuration, and used as a side-looking terrain-mapping sonar. Encouraging experimental results are reported.