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M2540-92000-01 A M2540 Ultrasound System Field Service Manual Page 41
Theory of Operation: TR Boards
plugs into the distribution board. The two boards form electronic beams of the transmit and
receive signals. Each TR board contains 64 transmitters and 32 preamps multiplexed into 64
receive channels. This allows multiplexing the system’s 64 active channels into 128 element
arrays. Each receive channel consists of time gain compensation (TGC) amplifiers, low pass
filters, 10-bit A/D converters, and one eighth of a digital beam-forming circuit. Each TR board
sends on its output bus a value that is the sum of the data from its 32 channels plus its 18-bit
input bus. The last TR board in this chain outputs the final summed radio-frequency (RF) data to
the demodulator board.
The transmit and receive beam-forming coefficients for acoustic lines are downloaded on the
coefficient bus from the BPAP board.
The BPAP board generates the timing to start and stop each firing line, and sends the transmit
signal to the TR board, through the distribution board and the connector modules to the
transducer. Analog drivers generate the transmitted RF data. A digital timing generator delays
and times each of the analog drivers. The delay generators receive the appropriate delay values
from the BPAP for each channel. The system power supply controls the amplitude of the
transmitted waveform.
The received signal is preamplified, TGC amplified, low-pass filtered, and digitized (in all modes
except CW). The BPAP board generates TGC control signals through the demodulator board.
After being digitized, the signal on each line is delayed appropriately. The outputs of all channels
are daisy-chained together to sum the outputs. The RF data output of one TR board is the input
to the next TR board, and the outputs of the TR boards are summed to form the received beam.
The summed output signal (RF DATA) goes to the demodulator board.
The CW Doppler signal is mixed to an analog intermediate frequency (IF) signal. The CW
Doppler output is a single differential signal routed to the demodulator board.