Optimum Symmetrical Number System Phase Sampled Direction Finding Antenna Architectures

摘要

A new interferometer direction finding array architecture based on the optimum symmetrical number system (OSNS) is presented. OSNS arrays are capable of unambiguous high-resolution direction finding with as few as three elements, with multiple baseline options. The OSNS DF antenna architecture being investigated uses the OSNS to decompose the analog spatial filtering operation into a number of parallel sub-operations (moduli) that are of smaller complexity. One two-element interferometer is used for each sub-operation and only requires a precision in accordance with its modulus. A much higher spatial resolution is achieved after the sub-operations are recombined. By incorporating the OSNS concept, the dynamic range of a specific configuration of antenna element spacings and comparator arrangements can be analyzed exactly. In this thesis, the OSNS DF antenna concept was demonstrated experimentally, by designing, fabricating and measuring the performance of a three-element array at 8.5 GHz. These three elements are grouped into two pairs (channels) according to the set of relatively prime moduli (m1 = 6, m2 = 11). A mixer is used to determine the phase difference between each pair of elements. The output voltage from the mixer in each channel is a symmetrical folding waveform that is DC biased and amplified using a summing amplifier. The output voltage of the amplifier is amplitude analyzed using a small comparator ladder. An EEPROM is used to recombine the results of these low precision channels to yield the high resolution direction of arrival (DOA). Simulated and experimental results are presented and compared.