Direction finding

摘要

An interferometer type DF system uses an array of five antennas (A,B,C,D,E) arranged at the apices of a regular pentagon to define five wide apertures along the sides of the pentagon and a further five apertures along the diagonals. The phases of the signals received by each antenna, are measured modulo 2 pi and processed to give a unique bearing of the radio source to the accuracy of the widest aperture defined by the array. One method of processing the phases is to calculate from them the Fourier coefficients of the Fourier series representing the spatial phase distribution. By comparing the difference between each calculated coefficient and a corresponding order coefficient of a set of imaginary antenna phases expressed as integral multiples of 2 pi , the complete 2 pi phase differences between the measured phases modulo 2 pi can be found. The bearing angle of the received signal is then the phase of the vector resulting from subtracting the first order Fourier coefficient of the integral phases from the calculated first order coefficient.