Image Number 2 for United States Patent #5841400.
A desired signal is received at first and second antennas. Output signals of the first and second antennas are orthogonal-detected by first and second signal conversion circuits and thereby converted into first and second baseband signals. A complex conjugation circuit generates a complex conjugation signal by calculating a complex conjugation of the second baseband signal. The first baseband signal and the complex conjugation signal are multiplied by a multiplier. A direction estimation circuit estimates a direction of the desired signal by effecting an inverse tangent calculation and an inverse cosine calculation on an output signal of the multiplier.