Parameters of a multiple-arm spiral antenna from single-arm measurements

Multiple-arm spiral antennas, generally with four or more arms, can be fed in multiple modes that produce different antenna patterns. The patterns and S-parameters of the antenna, operating in different modes, can be found by combining a weighted sum of measurements made on individual arms. The frequency range of good efficiency can be determined from S-parameter measurements before the antenna patterns and gain are measured. Individual arm measurements isolate construction problems that would be masked by a feed network