Panasonic KX-TG5776S Service Manual page 33

4.9.4. 5.8 GHz PA (Power Amplifier), 5.8 GHz LNA (Low Noise Amplifier) and Antenna
Switch Circuit
PA block amplifies power of 5.8 GHz TX signal.
5.8 GHz TX signal from 5.8 GHz Converter circuit is filtered by 5.8 GHz-BPF FL811, and amplified by Power amplifier (PA) block of
IC851. After that, it is supplied to Antenna Switch block of IC851. V_PA is approximately 4.0 V at Base Unit, and 3.1 V at Handset.
LNA block amplifies receiving 5.8 GHz signal.
5.8 GHz RX signal from Antenna Switch block of IC851 amplified by LNA (Low Noise Amplifier) block of IC851 and filtered by HPF
(FL821), and then supplied to 5.8 GHz Converter circuit.
Antenna Switch block selects the TX 5.8 GHz signal or RX 5.8 G signal, and connect to Antenna terminal.
Note:
The exposed GND_PLATE on the bottom of the IC851 supplies the circuit ground(s) for the entire chip. It is very important that
a good solder connection is made between this GND_PLATE and the ground plane of the PCB underlying the IC851.
<Base Unit>
IC851 includes Switches for High frequency signals, and controlled by ANT0 signal and ANT1 signal from DSP.
DSP is checking RSSI (Received Signal Strength Indicator) signal, and selects better condition Antenna from two antennas.
At the TX mode 5.8 GHz TX signal from 5.8 GHz PA block leads to selected Antenna terminal, at the RX mode 5.8 GHz RX signal
from selected Antenna terminal leads to 5.8 GHz LNA block.
<Handset>
IC851 includes Switch for High frequency signals, and controlled by PA_CONT signal and RX_EN signal from DSP. At the TX mode
5.8 GHz TX signal from 5.8 GHz PA block leads to Antenna terminal, at the RX mode 5.8 GHz RX signal from Antenna terminal
leads to 5.8 GHz LNA block.
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KX-TG5776S/KX-TG5777S/KX-TGA571S