Manabu SATO,¹ Masakazu ENDO¹ and Naohiro TANNO^1,2

¹Graduate Program of Human Sensing and Functional Sensor Engineering, Graduate School of Science and Engineering, Yamagata University, 4-3-16, Johnan, Yonezawa, Yamagata, 992-8510 Japan, ²Regional Joint Research Project of Yamagata Prefecture, Yamagata Technopolis Foundation, 2-2-1, Matsuei, Yamagata, 990-2473 Japan

(Received March 27, 2000; Accepted May 26, 2000)

The theory of phase-drift-suppression method and simulated results using sinusoidal and triangular phase modulation have been described. The computed signal intensity is defined as the square root of the sum of squares of each harmonic intensity in the heterodyne beat signal. The relations between the computed signal intensity, its relative standard deviation, and the modulation indexes are shown through simulations. Modulation indexes that suppress the phase drifts were obtained, including up to the eighth harmonic. The stability of the beat signal in sinusoidal and triangular phase modulation was confirmed to increase 245 times using harmonics from the fundamental to the fourth order and a modulation index of 2.8 rad, and to increase 490 times using harmonics from the fundamental to the second order and 2.9 rad.

Key words : heterodyne beat signal, stabilization, harmonics, phase drift

msato@dip.yz.yamagata-u.ac.jp