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49

TXVCO
1200MHz

PN code
    IC920

2.4GHz
SS signal

18

The signal of 1200MHz is input from pin 42

 

of IC750. At first, TX Doubler (internal) makes this signal to 2400 MHz, then this

signal goes to Spreader (internal).
PN code* from pin 18

  

of IC920 is input to pin 37

  

of IC750, causing the input signal coming from TX Doubler (internal).

The spread signal is output from pin 33

 

of IC750.

The spread signal output from pin 33

 

of IC750 is input to pin 4

  

of Driver Amp. Q720 through FL750 (2400 MHz BPF). Q720

      increases the level approximately 15dB, then it is output from pin 2 . This signal is input from pin 5  of IC701 (Power Amp.).

IC701 increases the level approximately 25 dB, then it radiated from TX ANT.

PN code* (Pseud Noise):
A  digital data that is multiplied to
extend a spectrum for a signal
modulated by base band signal
(FM).

50

51.76MHz
SS signal

51.76MHz
FM signal

PN code
    IC920

19

RXVCO
850MHz

  The receiving signal (spread signal) input from antenna (RXANT1) is passed through FL730 and amplified at Q730,
  then led to pin 26

  

of IC750.The signals from pin 26

  

is mixed internally with RXVCO signal (pin19 of IC750),and

  generate the 1st IF signal of 51.76MHz, then it is output from pin 23. The 1st IF signal is limited at Q830 and led to IC800.

The 1st IF signal (spread signal) of 51.76MHz is input to pin 28

  

of IC800. PN code output from pin 19

  

of IC920 is input to pin 1

of IC800.
This PN code despreads, and the 1st IF signal (FM signal) is output from pin 26

  

of IC800.

51

2nd Local
40.96MHz

51.76
FM signal

2nd IF
10.8MHz

Voice signal

VR800

RSSI-IN
IC920

4

IC800 detects the 2nd IF signal (10.8MHz), and converts the receiving signal level to DC voltage, then outputs from pin 12.
This level modulation of RSSI indicates a level modulation of reception signal. In this system, this modulation takes a periodic
of SS (PN), and returns extended signal by PN to original signal that is not extended. Output  (pin 12) of RSSI is connected to
IC920 and Q731.
IC920 takes the periodic of SS (PN) that is referred above. Q731 controls Gain of Reception Amp between handset and base
unit.

The receiving signal, FM signal which is despread at despreader (IC800 internal), is input to pin 23

  

of IC800.The  2nd local

signal of 40.96MHz coming from pin 1  of IC750 is input to pin 3

  

of IC800.

IC800 makes the 2nd local signal of 10.8MHz from the input signals of pin 3

  

and pin 23

  

, and outputs it from pin 20.

Then the FM demodulated signal, voice signal is output from pin 16.

52

The noise filter IC800 (internal) detects the noise level when the level of receiving signal is low (weak electric field),
and compares with the reference level of IC800, then informs CPU the result.
• Pin 5 of IC800 becomes "H" in the weak electric field, and "L" when a signal is received.