The Construction of Missle Guidance Codes Resistant to Random Interference

M a n y types of missiles are guided by commands consisting of a time sequence of RF pulses. The missile receiver is capable of receiving not only the true command pulses, but also any interfering RF pulses emanating from other radars in the vicinity (friendly interference) or deliberately generated by the enemy (enemy interference). The purpose of this paper is to suggest command-encoding methods that minimize the effects of this interference. Greatest emphasis is placed on random interference models, because it is difficult to make realistic general assumptions about the behavior of an enemy who knows something about the code structure. The following sections m a y convey the impression that the construc973 974 T H E B E L L SYSTEM T E C H N I C A L J O U R N A L , JULY 1960 tion of a code invulnerable to random pulse interference is the only factor entering into the choice of a code. This is not meant to be the case; accuracy and reliability of decoding equipment, weight in the missile receiver, power considerations at the transmitter and missile dynamics and maneuverability also play very important roles. However, it will be made clear to the reader that code invulnerability should not be completely ignored, and that reasonable guideposts of cfesign are available. In order to fix ideas, the codes presented in this paper are discussed in terms of missile guidance. However, the reader will note that other applications are possible. In particular, the codes described here can be used in radio communications to provide protection against the mutual interference of many communications transmitters operating in the same area on the same frequency.