Aloka Co.,Ltd., Research Laboratory, Ohme-Shi, Japan.
IEEE Trans Ultrason Ferroelectr Freq Control. 2010 May;57(5):1064-76. doi: 10.1109/TUFFC.2010.1518.
The low peak power of frequency-modulated continuous wave (FMCW) radar makes it attractive for various applications, including vehicle collision warning systems and airborne radio altimeters. This paper describes a new ultrasound Doppler measurement system that measures blood flow velocity based on principles similar to those of FMCW radar. We propose a sinusoidal wave for FM modulation and introduce a new demodulation technique for obtaining Doppler information with high SNR and range resolution. Doppler signals are demodulated with a reference FMCW signal to adjust delay times so that they are equal to propagation times between the transmitter and the receiver. Analytical results suggest that Doppler signals can be obtained from a selected position, as with a sample volume in pulse wave Doppler systems, and that the resulting SNR is nearly identical to that obtained with continuous wave (CW) Doppler systems. Additionally, clutter power is less than that of CW Doppler systems. The analytical results were verified by experiments involving electronic circuits and Doppler ultrasound phantoms.
调频连续波（FMCW）雷达的低峰值功率使其在各种应用中具有吸引力，包括车辆碰撞警告系统和机载无线电高度计。本文描述了一种新的超声多普勒测量系统，该系统基于与 FMCW 雷达类似的原理来测量血流速度。我们提出了一种用于 FM 调制的正弦波，并引入了一种新的解调技术，以获得具有高 SNR 和距离分辨率的多普勒信息。多普勒信号通过参考 FMCW 信号进行解调，以调整延迟时间，使其等于发射器和接收器之间的传播时间。分析结果表明，可以从选定位置（如脉冲波多普勒系统中的采样体积）获得多普勒信号，并且所得到的 SNR 几乎与连续波（CW）多普勒系统相同。此外，杂波功率小于 CW 多普勒系统。通过涉及电子电路和多普勒超声模拟体的实验验证了分析结果。
