VHF1 (136
‐
174 MHz)
Circuit Description
23
PreDriver
Attenuator
RD01
RD07
Finalstage
PD85035S
Microstrip
Matcher
Driver
Firststage
Tx/Rx
Switch
Harmonic
Filter
Microstrip Dual
Directional Coupler
ANT
Rx_PORT
Tx_PORT
V
A_TX
B+
B+
Forward
Detector
Reflect
Detector
Alarm to ADC
VSWR Protection
TV_APC
Temperature
compensation
High
Temperature
Protection
OMAP
Match
Match
Match
TXC
RX
Voltage
Detec
ADC
TX_LO
Power Amplifier
The 4-stage power amplifier amplifies the signal output from VCO to the required output power level.
The first stage is a buffer amplifier circuit with fixed gain; the second stage is a pre-driver power amplifier
circuit with variable gain (formed by Q7012); the third stage is a driver power amplifier circuit with
variable gain (formed by Q7010); and the final stage is the final power amplifier circuit with fixed gain
(formed by Q7013). In addition, TX power amplifier circuit contains a TX/RX switch and a low-pass filter.
TX Buffer Amplifier
The first stage (Q7014) provides about 16 dB power gain, and adjusts its bias circuit to get a quiescent
bias current of 28 mA (for Q7014). Power supply for the switching transistor Q7007 is controlled by TX
signal (enabled by antenna switch), so as to further control the power supply for Q7014.
Pre-driver Power Amplifier
The pre-driver power amplifier is formed by Q7012, with variable gain controlled by voltage VGG. The
input matching circuit is composed of C7045, L7022, L7017, C7052 and R7071.
Driver Power Amplifier
The driver power amplifier is formed by Q7010, with variable gain controlled by voltage VGG. The
maximum output power is +38.5 dBm, and the maximum adjustable gain is 15 dB.
Final Power Amplifier
The final power amplifier consists of Q7013, with the maximum output power of +45.4 dBm, and the
maximum adjustable gain of 14 dB. The PA input matching circuit is composed of C7115, C7112, R7107,
R7103, R7104, R7105, R7106 and R7108, while the power combination matching circuit is composed of
C7150, C7100, C7099, C7085, C7103, C7086 and C7087.
Antenna Switch
The antenna switch is used to switch between the transmitter circuit and the receiver circuit. In TX mode,
TX signal controls the switching transistor Q7007, to further control the power supply 8 V 5 A for the PIN
Summary of Contents for MD652
Page 1: ...DIGITAL MOBILE RADIO...
Page 5: ...UHF1 400 470 MHz...
Page 15: ...Exploded View and Packaging Guide UHF1 400 470 MHz 8 3 2 Packaging Guide...
Page 53: ...43 9 PCB View Front Panel PCB View Top Layer X...
Page 54: ...44 Front Panel PCB View Bottom Layer...
Page 55: ...45 Main Board PCB View Top Layer...
Page 56: ...46 Main Board PCB View Bottom Layer...
Page 106: ...VHF1 136 174 MHz...
Page 116: ...Exploded View and Packaging Guide VHF1 136 174 MHz 8 3 2 Packaging Guide...
Page 154: ...43 9 PCB View Front Panel PCB View Top Layer...
Page 155: ...44 Front Panel PCB View Bottom Layer...
Page 156: ...45 Main Board PCB View Top Layer...
