Design and Construction of a Blood Flow Detector Probe for a Continuous Wave Bidireccional Doppler Ultrasound System

The design and construction of a blood flow detector probe for a Continuous Wave (CW) Bidirectional Doppler Ultrasound system is presented. This device is based on two piezoelectric ceramics working in continuous mode and using quadrature phase demodulation for detecting the blood flow Doppler signal. The probe generates the I (In phase) and Q (in Quadrature) Doppler signals as audio. These signals are fed to the line in on the PC sound board for further processing. Oscillator-transmitter and detector-demodulator circuits are integrated into a 1.5 x 9 cm printed circuit board (PCB). Piezoelectric ceramics are placed and connected 1 cm apart the PCB, this achieves noise reduction and increases the probe sensibility. The circuit design allows operation at 4, 5, 8 and 10 MHz depending on the blood flow detection depth in arteries or superficial vessels.