A Four-Phase Modulation System for Use with an Adaptive Array.

: This report discusses the use of four-phase modulation in a communication system with an adaptive array. A system is described that provides protection against both conventional (i.e., noise and cw) and smart (in particular, repeat) jamming with rapid acquisition of the signal at the receiver. This report first discusses four-phase modulation techniques and how they can be used with an adaptive array. Reference signal generation for the LMS adaptive array is discussed for these modulation techniques. A communication system is then described that uses one of these modulation techniques. The four-phase signal consists of two orthogonal biphase signals. One signal contains a short code for rapid acquisition. The other contains a long code for protection against smart jammers. A several step signal acquisition technique is also described for the system. The short code timing is first acquired by a sliding correlation method. With the short code used in reference signal generation, the long code timing is rapidly acquired by the Rapid Acquisition by Sequential Estimation method. The long code is then used in reference signal generation.