Apparatus for measuring physical quantity related to relative movement between two objects

An apparatus for measuring physical quantities related to a relative movement between two objects, the apparatus being provided in one of the two objects and comprising:

• an oscillator for generating a carrier signal for transmission;
• a code generator for generating first and second coded two-phase random signals for modulation, each of said first and second kinds of coded two-phase random signals having different phases;
• a modulation circuit for effecting a direct spread modulation with respect to the transmission carrier signal using the generated coded two-phase random signal;
• antenna means comprising first and second antennas having antenna patterns with different beam angles for transmitting the modulated transmission carrier signal as a radio wave toward the other of the two objects and for receiving a reflection wave from the other of the two objects, each of said first and second antennas transmitting and receiving a signal modulated by a corresponding one of the first and second kinds of coded two-phase random signals;
• a demodulation circuit for demodulating a signal corresponding to the received reflection wave using the transmission carrier signal, to thereby generate an intermediate freguency signal;
• a correlation circuit for making correlation between the intermediate frequency signal generated by the demodulation circuit and a signal having the same code as that of the coded two-phase random signal for modulation and having a phase delayed by a predetermined time compared with the coded two-phase random signal for modulation;
• filtering means for extracting from an output signal of the correlation circuit a Doppler frequency component contained in a signal which has been propagated through a propagation path existing in a specified distance range;
• and
• a detection circuit for properly processing a signal of the extracted Doppler frequency component, said detection circuit extracting only a Doppler frequency component contained in the reflection wave from an overlapped area of each antenna pattern of the first and second antennas and, based on the extracted Doppler frequency component, detecting physical quantities related to the relative movement between the two objects.