Integrated spiral antennas for aerospace applications

The need for an optimized antenna system design for use as a basic building block in large aerospace phased arrays is discussed. The proposition is made that this optimized antenna system can best be designed with solid state electronics integrated directly into the feed point of a multimode slow wave planar spiral antenna of either the Archimedean or equiangular variety. First, a general review of the state of the art of the integration of antennas and electronics is given for a thorough understanding of the topic. Then, a development of the general characteristics of both Archimedean and equiangular multimode planar spiral antennas is given. The modal excitation characteristics of this type of antenna are investigated to show that the total field of multimode spiral antennas may be written as the weighted summation of the fields excited by the individual modes once the form of these mode fields has been determined. A hybrid model of the mode fields is developed based on a modified combination of the ring radiator model and the anisotropic sheet model. The form of the optimized directivity function for a planar multimode spiral antenna is then developed, and the results of this optimization are discussed. Finally, the gain and phase shift requirements of the solid state integrated circuitry required to give the optimized directivity are given. The development of the important system parameters of integrated spiral antennas is given next. An expression for the input impedance for each arm of the spiral is developed, and the results are given for reception and transmit applications. A general expression for the gain of integrated spiral antennas is presented. The derivation of the noise properties of integrated spiral antennas is also presented. The computerized calculations of the input parameters of multimode planar spiral antennas are then discussed. These data are required in order to determine the requirements to he placed on the integrated solid state circuitry. The general conclusion that is reached from an observation of these data is that very little change in pattern shape occurs for scan angles beyond 60° for any combination of design parameters. Finally, a discussion of the results of experimental measurements on several representative multimode planar spiral antenna designs is given. A comparison is made between the analytical and experimental data for a limited number of antenna configurations. The dissertation is concluded with the use of the analytical data to obtain the general design of an optimized multimode planar spiral antenna for an application being considered on a space shuttle. The general conclusion reached as a result of this research is that the analytical predictions and models may be used to adequately design optimized integrated spiral antenna systems for any application once the general design constraints have been specified.Electrical and Computer Engineering, Department o