Practical comparisons between various high resolution spectral estimation algorithms for radio direction finding

Systems consisting of an antenna array utilising conventional beam forming techniques, like sum-and-delay beam forming, may be able to resolve interference if the incoming waves are well separated in their direction of arrival (DOA). Another approach to multiple source direction finding is utilising high resolution spectral estimation techniques. Analogous to sampling a time domain signal and transforming it to the frequency domain, the interference field can be sampled spatially by means of the antenna array, and then the sampled information is transformed to the wave vector or angle domain. The peaks in the resulting angle spectrum correspond to the DOA. Compared with conventional beam forming, the high resolution methods have a better resolution and allows one to estimate not only the DOA, but other field parameters like signal power, signal correlation, polarisation and signal-to-noise ratio. We present experimental results for a radio direction finding (DF) system in the HF band and compare various high resolution algorithms and a Fourier based method. The measurements were made with a nine channel DF-system, which allows the hardware independent application of any algorithm only by manipulating the signal processing software