The engineers at Randtron Antenna Systems have direct hardware experience with ESM interferometer antenna systems, designed for precision direction finding onboard military aircraft. We are fully aware of the tradeoffs between antenna phase tracking, gain tracking, RCS, and the implementation problem of antennas in significant stress areas on high performance aircraft. Our interferometer expertise has been achieved from fully developed systems such as ESM antenna arrays for the B-2, A-12 leading edge, and other programs using both spiral and sinuous elements. Our forte with interferometer antennas is designing complex arrays, which produce high accuracy Angle-of-Arrival (AOA) direction, covering multi-octave bandwidths, with limited RCS over large regions of space. A highly specialized group of analytic tools has been developed to predict the RF and RCS performance of various antenna systems. These tools can synthesize the various baselegs required for AOA accuracy with complete ambiguity resolution. The length of the interferometer array is determined by the accuracy of the AOA requirement and the phase resolution measurement receiver. In order to realize high precision AOA accuracy in DF systems, the interferometer must be populated with enough elements to resolve ambiguities in the AOA measurement. If a long baseleg is used, the interferometer must be broken into subarray pairs with varying prime number ratios. This prevents a high gross AOA error rate from occurring in the ambiguity resolving process. The elevation AOA must also be measured for targets off the principal plane to prevent coning errors in the azimuth AOA. We have specialized test facilities for digital acquisition of and statistical analysis for the massive amount of data required to completely validate interferometer arrays. Physical test hardware is specifically designed to conform to the particular installation configuration and contains specialized features to isolate the array from local surfaces effects. Treatments are used to provide environmental resistance and to reduce the RCS, when needed. Interferometer elements are single polarization spiral antennas, or simultaneously dual polarized sinuous antennas. The phase tracking of the antenna elements is key to achieving a precision DF array. For maximum precision, all radiating elements are etched on a single sheet by a photo-lithographic process using a standard negative. As a result, spacing tolerances between elements can be held to ±.001 inch. Delay line trimmers are provided on critical cables to produce phase matching of the entire array. The ultimate AOA accuracy is achieved when a precision calibration network is included with the switch matrix that selects the baseleg pairs. This network contains closely matched components to cancel the errors in the balance of the system. This calibration network inherently serves as a BITE function (not including antenna elements) without the need for added components.Phase interferometers built at Randtron Antenna Systems have shown excellent AOA accuracy. For example, a multiple baseleg unit measured less than 6 degrees RMS phase tracking over the entire 2 to 18 GHz band and a ±60 degrees cone. Our most sophisticated design was an 8 element conformal array operating over a 9:1 band, ±60 degrees in space and included a switch matrix and precision calibration network. Other precision designs have been developed to cover out to near-grazing angles. Our years of experience have proven that we can meet your requirement in building a sophisticated and reliable interferometer antenna system.