GE M
EDICAL
S
YSTEMS
D
IRECTION
2300164-100, R
EVISION
7
V
IVID
™ 3 P
RO
/V
IVID
™ 3 S
ERVICE
M
ANUAL
Chapter 5 - Components and Function (Theory)
5-13
5-4-1-6
Received Signal Path
The receive signal is programmed according to the operating mode that was selected by the user. In some
cases the signal is received immediately after it has been transmitted, sometimes after a prescribed delay,
and in other cases at the same time as transmission (transmit/receive simultaneously).
Refer to
Figure 5-8
on page 5-15 or
Figure 5-8
on page 5-15, as appropriate.
The probe elements receive the echo signals from different depths. These signals are amplified and
conditioned at the Analog Time Gain Compensation (ATGC) control. The different operating modes
dictate in which way the signals are translated, as follows:
•
Continuous Mode (CW)
-
echo signals are transmitted and received simultaneously, and
translated per echo point for a specified depth. This provides a
real-time image.
•
2D Mode
-
signals are received from all 64 channels (if a probe has more than
64 elements, the MUX of the probe is used to create the additional
missing channels). The signals are transmitted at a prescribed
delay between the elements, and immediately after this are
received (all the time, aiming at one point at a specific depth). In this
way, echo signals are collected from all points along a certain line,
from which a vector is created. The vector is transmitted to the MUX
board, and from there to the Beamformer where it is amplified and
undergoes analog-to-digital conversion. From here RF signals are
transmitted to the RFT board, where an image is created.
•
Color Flow Mode (CFM)
-
shows the movement of particles (this mode is usually used
together with 2D mode). In CFM mode, the echo signal received
is used to measure the amount of frequency phase change
(degree of shift) - this is referred to as the
Doppler effec
t.
When using CFM and 2D modes together, at the same time that
the signal is received, in parallel it is used to generate a signal
through a circuit that translates the Doppler effect, and from which
it generates a color image.
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