汐崎 陽¹, 千田 彰一², 北畠 顕³, 森田 久樹², 水重 克文², 増山 理³, 松尾 裕英²

Akira SHIOZAKI¹, Shoh-ichi SENDA², Akira KITABATAKE³, Hisaki MORITA², Katsufumi MIZUSHIGE², Tohru MASUYAMA³, Hirohide MATSUO²

¹大阪電気通信大学工学部通信工学科, ²香川医科大学内科学講座第二内科学, ³大阪大学医学部第一内科

¹Faculty of Engineering, Osaka Electro-Communication University, ²The 2nd Department of Internal Medicine, Kagawa Medical School, ³The 1st Department of Internal Medicine, Osaka University Medical School

キーワード : Doppler flowmeter, modulation Doppler system, range resolution, pseudo-random sequence, continuous wave

This paper presents a new modulation Doppler system with a range resolution. Ultrasonic waves modulated by a pseudo-random sequence are transmitted. Waves reflected from targets are passed through a gate or cut off according to the value +1 or -1 of the pseudo-random sequence for which the delay time is adjusted to the travelling time of the ultrasonic wave via the desired range. The wave through the gate is passed through a band-pass filter whose pass-band is near a carrier frequency. Then only the reflected wave from the desired range is obtained and other unfavorable reflected waves are completely eliminated. The reflected wave from each depth range can be picked up by changing the delay time of the pseudo-random sequence. This system has an advantage that it is capable of increasing the power of the Doppler signal from the desired range without increasing peak power because of using a continuous wave and the equipment is simpler because of using a gate instead of a multiplier. Elementary experimental results are also shown for demonstrating the usefulness of this system.