GE LOGIQ E9 Service Manual page 306

GE
D 5535208-100, R
IRECTION
7-5-8-9 Analog CW (cont'd)
The 3-term Blackman-Harris window function is used for the analog CW tests. The input frequency is
2.521 MHz for a number of the tests and with the Mixer clock at 2.5 MHz; a Doppler frequency at 21 kHz
should result. To be able to find such low frequencies a vector is acquired that enables the Fast Fourier
Transform (FFT) of 16K samples (I-data) or 8K (I- & Q-data). This will give bin spacing of approximately
3 kHz (8K samples) and 1.5 kHz (16K samples).
The following tests will run with probes connected to the scanner, but it is recommended to disconnect
all probes before running diagnostics. Only connect a probe or test connector if instructed for a specific
test.
Name: Service Diagnostics / Analog CW / GRX aCW Dual Channel
For each channel pair, a signal is set up with f0=2.521 MHz, the Band Pass (BP) filter at 3.1 MHz and
a mixer frequency of 2.5 MHz. The dither and Pedof probe inputs are disabled. The Doppler channel
pairs are measured for the parameters: fdop, spectrum peak, RMS, SNR and THD. This is calculated
for I & Q data separately.
Disconnect all probes before running diagnostics.
Run Time: 00:05
If this test fails:
1.) Verify the following tests pass:
-
-
If these tests pass, and the GRX aCW Dual Channel test fails:
2.) Replace the CW GRX board.
Name: Service Diagnostics / Analog CW / GRX aCW Beam Forming
A sum of sine waves with the same frequency, but different phase, gives a sine wave output where the
amplitude is a function of the different phase settings.
The test uses small overlapping groups (4 channels) where the channel pairs have different phase
settings. Any amplitude deviation detected in this test, should indicate that there is something wrong
with phase setup. For each subtest, a signal is set up with f0=2.521 MHz, the BP filter at 3.1 MHz and
a mixer frequency of 2.5 MHz. The dither and Pedof probe inputs are disabled. The parameters tested
are: fdop, spectrum peak, RMS and SNR on the I-data.
Are the probes connected? The test will run with probes connected to the scanner, but it is
recommended to disconnect all probes before running diagnostics.
Run Time: 00:05
1.) Verify the following tests pass:
-
-
If these tests pass, and the GRX aCW Beam Forming test fails:
2.) Replace the CW GRX board.
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EV
GFI Tests
Analog Receive Tests
GFI Tests
Analog Receive Tests
Section 7-5 - Common Service Desktop
LOGIQ E9 S M
ERVICE ANUAL