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NHM-2/5nx,ny/6/9
Troubleshooting
The signal-path is through Z501 (In-band insertion-loss 3,5dB), through the matching circuit (C517 )
and to the GSM1800 LNA (V500, RFin).
The LNA has about 18dB gain when it is "on" (LNAB_G = 2.8V and LNA_P = 0V). If the signal applied
to the antenna-connector is more than –45dBm the AGC will gain-step the LNA (LNAB_G = 2.8V and
LNA_P = 0V) which means the LNA Gain will now have negative gain (loss) of –12dB.
From the LNA (V500 RF out) the signal is lead through the LNA-output-matching-circuit (C519, L502),
nd
through the 2
Dual RX SAW Z500 (In-band insertion-loss 3,5dB) to the GSM1800 balun T500. From
the balun the signal is balanced and is lead to Hagar (N500 IMP_P_RX and INM_P_RX).
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The balanced RX signal is mixed with a signal from the local oscillator at the same frequency as the
wanted RX signal. After mixing the signal is converted to a single-ended signal in the DtoS (Differential
to Single-ended) amplifier. The signal is now filtered in a BIQUAD filter to provide channel separation,
amplified in the BB_Gain amplifier and DC compensated in DCN2.
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PAMS Technical Documentation
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