JPS57127870A - System of measuring delay time difference - Google Patents

Abstract

PURPOSE:To measure the difference in delay time without cutting off base band signals by synthesizing and transmitting signals from oscillators having a fixed differential frequency provided on the transmission side between systems with a different path from each other. CONSTITUTION:Oscillators 41 and 42 output signals having a fixed difference in the frequency therebetween. These outputs are synthesized with a hybrid circuit 43 and made to overlap base band signals with a hybrid circuit 32. The synthesized signals are transmitted from an FM modulators 2 and 3, transmitters 4 and 5 and an antenna 6 composing the existing circuit and a extra circuit. The signals passing through an antenna 9, receivers 10 and 11 and FM demodulators 12 and 13 are branched off with hybrid circuit 33 and 34 and after switched over to each other with a switching circuit 16, branched off into two parts with a hybrid 44. One part of the signals are introduced to a filter 45 for extracting the frequency component of the oscillator 41 on the transmission side while the other part thereof are introduced to a filter 46 for extracting synthesized frequency components of oscillators 41 and 42. Then, they are mixed 47 to measure absolute difference in the delay time.