Radio direction finder with array element signal processing

Claim 1

Radio direction finding equipment for deriving information respecting the angular position of a mobile craft with respect to said equipment from radio frequency pulses signals emanting from said craft, comprising: antenna means having n elements responsive to said emanating pulses to produce a series of n contemporaneons pulse signals of equal frequency and with phase difference ψ between successive signals of said series determined by the angle of arrival of said pulses from said mobile craft; a first mixing network including n first mixers each responsive to a corresponding one of said antenna elements and to a first phase of a local oscillaton providing a local oscillaton signal at substantially the same frequency as that of said emanating pulse signals; a second mixing network including n second mixers each responsive to a corresponding one of said antenna elements and to a second phase of said local oscillaton, said second phase being substantially at π/2 radians with respect to said first local oscillaton phase; zero response means providing n pairs outputs and being responsive to the outputs of said first and second mixing networks to provide predetermined output corresponding to the occurrance of zero frequency output from each mixer of said first and second mixer networks, said predetermined output being characterized by I j and Q j , where I j is proportional to cos jψ and Q j is proportional to sin jψ, j representing the position of said zero frequency output; sampling means responsive to said n pairs of outputs of said zero response means to derive from each of said pairs outputs in the form I j Q j -I j -Q j ; and signal processing means for processing the n output pairs of said sampling means to determine therefrom the value of said ψ which is the phase difference of said emanating signal between successive elements of said antenna means and characterizes said angle of arrival of said pulses from said mobile craft.