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Transmitter Functional Blocks
US Gating
US Driver
US Receiver
Chapter 9 - Theory of Operation
The US Gating circuitry generates the gated 1 MHz bursts for the US driver
and the US receiver necessary in a pulsed doppler system.
The burst repetition rate is 3.2 kHz. The US driver burst has a duration of
µ
96
sec. The burst for the Receiver's demodulator, which also has a duration
µ
of 96
sec, follows the driver bursts with a delay of 32
a sensitive depth range from 2.4cm up to 16.8cm (with a sound velocity in
human tissue of 1500 m/sec.)
The US Driver circuitry drives the ultrasound transducer crystals with the
bursts delivered by the US Gating module. The output amplitude is 4V peak
to peak. The drivers output goes to a high impedance state when the driving
burst is inactive.
The US Receiver consists of three submodules:
•
Preamplifier
•
Demodulator
•
Bandpass filter with amplification
The preamplifier amplifies the small doppler shifted 1MHz signals from the
transducer. These are converted to the low frequency baseband by the
Theory of Operation
µ
sec. This timing gives
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