Motorola Gm1200e Detailled 68p64115b15 Manual

							Frequency Synthesis
Introduction/Theory of Operation3.1-31
In TX mode AUX3 is about 5V DC and Q3742 is switched off. Q3752 is switched on and enables a 
current flow from the source of FET Q3741 while Q3751 is switched off. When switched on the FETs 
draw a drain current of 8 mA from the FRAC-N IC super filter output. The frequency of the receive 
oscillator is mainly determined by L3752, C3752, C3754 - C3756 and varactor diodes D3751 / 
D3752. Diode D3754 controls the amplitude of the oscillator. The frequency of the transmit oscillator 
is mainly determined by L3734, C3736 - C3740 and varactor diodes D3732 / D3733. Diode D3739 
controls the amplitude of the oscillator. With a steering voltage from 3V to 10V at the varactor diodes 
the RX frequency range from 181.1MHz to 219.1MHz and the TX frequency range from 136MHz to 
174MHz are covered. In TX mode the modulation signal coming from the FRAC-N synthesizer IC 
(U3701 pin 28) modulates the TX VCO via varactor diode D3731.
Both oscillator outputs are combined and buffered by the VCO Buffer Q3760. Q3760 draws a 
collector current of 13 mA from the stabilized 5V (U3801) and drives the Mixer Buffer Q3770. Q3770 
draws a collector current of 17 mA from the 9V3 voltage and drives the PA Buffer Q3780 (Pout = 
13dBm) and the Pre-scaler Buffer Q3790. Q3790 draws a collector current of 8 mA from the 
stabilized 5V (U3801) and drives the pre-scaler internal to the FRAC-N IC. In transmit mode Q3780 
is switched on by the K9V1 signal and draws a collector current of 19 mA from the K9V1 voltage. 
The injection signal VCO MIXER with a level of 10dBm feeds the mixer through R3774. The buffer 
stages Q3760, Q3770, Q3780 and the feedback amplifier Q3790 provide the necessary gain and 
isolation for the synthesizer loop.
13.4 Synthesizer Operation
The complete synthesizer subsystem works as follows. The combined output signal of the RX VCO 
(Q3751) and TX VCO (Q3741) is buffered by VCO Buffer Q3760, Mixer Buffer Q3770 and Pre-scaler 
Buffer Q3790. To close the synthesizer loop, the collector of Q3790 is connected to the PREIN port 
of synthesizer U3701 (pin 20). The output of the VCO Buffer (Q3770) also provides signals for the 
mixer (via VCO MIXER) and the PA Buffer (Q3780).
The pre-scaler in the synthesizer (U3701) is basically a dual modulus pre-scaler with selectable 
divider ratios. This divider ratio of the pre-scaler is controlled by the loop divider, which in turn 
receives its inputs via the SRL. The output of the pre-scaler is applied to the loop divider. The output 
of the loop divider is connected to the phase detector, which compares the loop divider´s output 
signal with the reference signal.The reference signal is generated by dividing down the signal of the 
reference oscillator (Y3701 or Y3702).
The output signal of the phase detector is a pulsed DC signal which is routed to the charge pump. 
The charge pump outputs a current at pin 29 (I OUT of U3701). The loop filter (which consists of 
R3715 - R3718, C3723 - C3725, C3727, C3735) transforms this current into a voltage that is applied 
to the varactor diodes D3732, D3733 (TX), D3751, D3752 (RX) and alters the output frequency of 
the TX VCO (Q3741) and RX VCO (Q3751). The current can be set to a value fixed in the FRAC-N 
IC or to a value determined by the current flowing into CPBIAS 1 (U3701-27). The current is set by 
the value of R3723 and R3724. The selection of the two different bias sources is done by software 
programming.
To reduce synthesizer lock time when new frequency data has been loaded into the synthesizer the 
magnitude of the loop current is increased by enabling the IADAPT line (U3701-31) for a certain 
software programmable time (Adapt Mode). The adapt mode timer is started by a low to high 
transient of the FRACN CE line. When the synthesizer is within the lock range the current is 
determined only by the resistors connected to CPBIAS 1 or the internal current source.
A settled synthesizer loop is indicated by a high level of signal LOCK DET (U3701-2). 
						

							Frequency Synthesis
3.1-32Introduction/Theory of Operation
LOCK DET adds up with signal SQ DET, weighted by resistors R0113, R0114, and is routed to one 
of the mP´s ADCs input U0101-43. From the voltage weighted by the resistors the mP determines 
whether SQ DET, LOCK DET or both are active.
In order to modulate the PLL the two spot modulation method is utilized. Via pin 8 (MODIN) on 
U3701 the audio signal is applied to both the A/D converter (low freq path) as well as the balance 
attenuator (high freq path). The A/D converter converts the low frequency analogue modulating 
signal into a digital code that is applied to the loop divider, thereby causing the carrier to deviate. The 
balance attenuator is used to adjust the VCO’s deviation sensitivity to high frequency modulating 
signals. The output of the balance attenuator is present at the MODOUT port (U3701-28) and 
connected to the VCO modulation diode D3731 via L3731, C3733. 
						

							PCB/Schematic Diagrams and Parts Lists 3.2-i
Chapter 3.2
PCB/Schematic Diagrams and Parts Lists
Table of Contents
Table of Contents
Description Page
PCB Overlays
UHF (403-430MHz)PCB 8486072B01_T1
Layout Top Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Layout Bottom Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
VHF (136-174MHz) PCB 8486069B01_T1
Layout Top Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Layout Bottom Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Controller Schematic Diagrams
Open Controller Schematic Diagram   1 of 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Open Controller_AUDIO Schematic Diagram   
2 of 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Open Controller_IO Schematic Diagram   
3 of 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6/8/10
Supply Voltage Schematic Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Parts List  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
UHF (403-470MHz) Schematic Diagrams and Parts Lists
Power Control Schematic Diagram  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Power Amplifier 5-25W Schematic Diagram  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Synthesizer Schematic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Voltage Controlled Oscillator Schematic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 
						

							Table of Contents
3.2-ii PCB/Schematic Diagrams and Parts Lists
Description Page
RX-FE Schematic Diagram  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  21
Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  22
RX-IF  Schematic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  23
Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  24
VHF (136-174MHz) Schematic Diagrams and Parts Lists
Power Control Schematic Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  25
Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  26
Power Amplifier 5-25W Schematic Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  27
Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  28
Synthesizer Schematic Diagram  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  29
Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  30
Voltage Controlled Oscillator Schematic Diagram  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  31
Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  32
RX-FE Schematic Diagram  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  33
Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  34
RX-IF  Schematic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  35
Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  36