A Heterodyne Low-Level Signal Phase Meter Operating over 1 MHz to 300 MHz

After giving a brief summary of the main devices allowing the measurement of phase shifts between two sine signals in the approximate range 1 Hz-1 GHz, we propose a new apparatus for measuring phase shift. The principle of this apparatus uses a heterodyne technique in association with a phase-locked loop which brings about frequency translation of the measured signals. The intermediate frequency which is obtained is small with respect to the frequencies studied conveying a high degree of selectivity to the apparatus. This allows measurements to be made on signal with noise or low-level signal while also maintaining good accuracy. For a system operating from 1-300 MHz, we have obtained phase linearity of ± 1°, resolution of 0.1°. In obtaining the accuracy of ± 5°, the sensitivity is -86 dBm in the 1-30-MHz frequency range; with 300 MHz the sensitivity reached is -68 dBm.