RTfino/RT3200 Advantage–II/RT–x200 SERVICE MANUAL
GE MEDICAL SYSTEMS
P9030GX
THEORY
5–6
REV 0
5–2–5 Echo Signal Processing (continued)
1.
Typically, a dynamic range of more than 100 dB exists between the strongest near field echoes and the weakest
far field echoes just above the threshold of noise. The strong near field echo returns are logarithmically com-
pressed prior to signal detection to compensate for increased signal attenuation at greater body depths. This
permits a uniform display of the echo source, regardless of the body depth.
5–2–6 Time Gain Compensation (TGC)/Time Frequency Compensation (TFC)
These signals are applied to the echo signal returns at the RFL pc Board.
1.
TGC varies echo gain to compensate for the greater attenuation occurring to echoes from greater body depths.
The amount of TGC applied depends on transducer type, echo center frequency and the acoustic impedance
characteristics of the patient.
2.
In operation, TGC on this system, can be adjusted by the slide Potentiometer provided on the front panel. System
gain and Dynamic range are selected on power up to the default settings.
3.
TFC varies the bandpass frequency of the detector in the RFL pc Board to compensate for shifts in the bandpass
center frequency spectrum of echoes returning from greater body depths.
5–3 RTfino/RT3200 Advantage–II/RT–x200 SYSTEM
See Illustration 5–2, the RTfino/RT3200 Advantage–II/RT–x200 system can be divided into an analog signal
processing section, a digital signal processing section, and the microprocessor driven system control section, which
controls the system based on operator commands and system status information.
5–3–1 Echo Signal Flow
The image information signal is used in three forms as shown in Illustration 5–2. The white arrow shows the analog
image signal path; the gray arrows show the digital image signal path. The black arrows show the standard TV
composite video signal path. Control signals are shown in the block diagram as thin black lines. Most control lines
emanate from the control section’s microprocessor.