10.4. Signal Flowchart in the Whole System
Reception
CN101 of the base unit is connected to the TEL line, and the signal is input through the bridge
diode D101. While talking the relay (Q121) is turned ON and amplified at the amplifiers Q461, then
led to DSP (IC501). DSP generates ADPCM signal. The ADPCM signal is input to RFIC (IC101) of
RF UNIT, and is mixed with pseudo random noise code (PN code) to spread the spectrum. RFIC
outputs FSK modulated RF signal. The RF signal is passed through the balun (T101) and filter
(L107) to the T/R switch (IC109). And the RF signal amplifies by the power amplifier (IC105) and
fed into T/R switch (IC110) and passes through filter (L106) to Diversity ANTENNA. As for the
handset, RF signal from the antenna passes through filter (L106) and switch by T/R switch
(IC110) to LNA (IC106). The RF signal is amplified by LNA (IC106) and switched by T/R switch
(IC109) and input to RFIC passing through filter (L107) and the balun (T101) to perform the de-
spread, then input to DSP (IC201). DSP performs ADPCM decoding to convert the signal into the
voice signal, then it is output to the speaker.
Transmission
The voice signal input from the microphone is led to DSP (IC201). The DSP generates ADPCM
signal. As well as the reception, it is converted into the RF signal by RFIC (IC101). Passing
through the balun (T101) and filter (L107), to the T/R switch (IC109). And the RF signal amplifies
by the power amprifier (IC105) and fed into T/R switch (IC110) and passes through filter (L106) to
ANTENNA. As for the base unit, RF signal from the Diversity antenna passes through filter (L106)
and switch by T/R switch (IC110) to LNA (IC106). The RF signal is amplified by LNA (IC106) and
switched by T/R switch (IC109) and is input to RFIC (IC101) passing through filter (L107) and the
balum (T101) to perform the de-spread, then input to DSP (IC201). DSP performs ADPCM
decoding to convert the signal into the voice signal. The voice signal is amplified at the TX
amplifier (Q131), then output to the TEL line (CN101) through the relay (Q121) and bridge (D101).
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