GE FC091194, Руководство по обслуживанию

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GE M
EDICAL
S
YSTEMS
D
IRECTION
FC091194, R
EVISION
02 V
IVID
7 / V
IVID
7 PRO S
ERVICE
M
ANUAL
Chapter 5 - Components and Functions (Theory) 5 - 7
5-3-5-2 RF and Tissue Processor (RFT) (cont’d)
Control
The RFT board has a local Digital Signal Processor (DSP) with an external EPROM.
The DSP performs multiple control tasks:
1.) It handles communication with the BEP over the VME bus.
2.) It updates filter coefficients and other parameters in the data path.
3.) When output events from the Front End Controller is received, it sets up the Pipelink output control
for data tagging and transfer.
4.) During transfer of time motion data, it sets up a time-slot data transfer (which replaced the output
event based transfer).
5-3-5-3 Spectrum Doppler Processor
The Spectrum Doppler Processor board (SDP) receives its data from the RFT board. In Pulsed Wave
(PW) Doppler several sets of data from the same range (depth) originating from different transmit pulses
are transferred from RFT data buffer. In Continuous Wave (CW) Doppler the data samples are
transferred consecutively.
Spectrum Analysis
The data sets are written into a sliding ring buffer with different ranges along the vertical axis and
different transmit pulses along the horizontal (time) axis, thus achieving a two-dimensional matrix. By
reading the data out of the buffer in a certain way (re. Principles of Operation) and performing Discrete
Fourier Transform on the data, velocities up to seven times the pulse repetition frequency (in PW) can
be displayed. Parts of the spectral analysis is done by a digital signal processor (DSP1).
During Duplex modes (e.g. 2D and Doppler) the gaps in the spectrum (when doing 2D) is filled by
stretching the “real” spectrum out to fill the missing time.
Audio
The Doppler audio channels (I and Q, or DOPLA and DOPLB) are generated based upon the digital
data stored in the ring buffer. The data is transferred from the buffer into DSP2 (Digital Signal Processor
no. 2) which controls the D/A conversion as well as the Missing Signal Estimation of audio in Duplex
modes.
Trace Interface
A serial link from the Internal I/O board, feeds several A/D converted traces (like ECG, phono, pressure)
into the Spectrum Doppler Processor board.
These traces as well as spectral data, are tagged and transported over the pipelink to the Image Port
under control of DSP1.
Control
The DSP1 controls the data flow and updating of all parameters, including control of read/write address
generation. It communicates with the BEP over the VME bus and provides the pipelink output with
spectrum and trace data.