Power Supply - Motorola Cleartone CM5000 Basic Service Manual

OVERVIEW
Linearizer and Power Control Circuit
This circuit consists of coupler, carrier phase shifter, quadrate demodulator, DC offset buffer and
comparator. To meet TETRA ACP specification requirements, Cartesian loop type linearizer is used.
The transmit signal that is picked up by the coupler is attenuated by the variable attenuator (CD303)
and fed to the quadrature demodulator (IC308). The output of the quadrate demodulator is fed to the
ADC of the control circuit and comparator. The control circuit calculates the phase and amplitude dif-
ference between the modulate signal and demodulate signal. Amplitude balance is adjusted at the
factory.
Phase difference is adjusted dynamically by phase shifter (IC319) to adjust the phase of quadrate
demodulator.
The DAC (IC702) output voltage is controlled and this voltage controls phase of the carried via buffer
amplifier (IC318).
The DC offset of the demodulated I and Q signal is corrected by adding the DC voltage from DAC
(IC702) at adder IC (IC318). Each I and Q signal is fed to the comparator and compared with refer-
ence modulation signal.
Transmit signal level is controlled by operating the forward attenuator (CD301) and reverse attenua-
tor (CD303) complementary.
Those attenuator should be controlled depend on the transmit power level. Output voltage of the
DAC (IC702) is changed and this voltage is fed to the buffer amplifier (IC307) and attenuator
(CD301). Then the output level of attenuator (CD301) is changed and input level of the Power ampli-
fier is changed.
Due to transmit level change, the picked up signal by the coupler for quadrature demodulator is
changed. To maintain the input level of the demodulator, attenuation of the reverse attenuator
(CD303) should be change. DAC (IC702) generates the control voltage for the reverse attenuator to
maintain the input level of the quadrature demodulator.

Power Supply

The voltage regulator of the RF circuit is series drop type. DC power via the power switch is fed to
the 9 V regulator IC (IC206). This voltage is used for transmit circuit.
9 V power is fed to the 5 V and 3.3 V regulator.
5 V voltage regulator (IC207) provides 5 V power for PLL circuit. Also this voltage is switched by
transistor (TR204) and fed to PLL circuit.
3.3 V voltage regulator (IC210) provides 3.3 V power for PLL circuit.
5 V regulator (IC208) provides 5 V power for the transmitter and receiver circuit. Also this voltage is
switched by transistor (TR206) and fed to receiver circuit.
5 V regulator (IC209) provides 5 V power for the transmitter circuit. Also this voltage is switched by
transistor (TR208) and fed to transmitter circuit.
CM5000 Mobile Repeater/Gateway - Basic Service Manual 21