Voltage Controlled Oscillator (VCO)
2-11
The operation logic is shown in Table 2-2.
Figure 2-8.
VCO Block Diagram
In the receive mode, U241-19 is low or grounded. This activates the receive VCO by enabling the
receive oscillator and the receive buffer of U241. The RF signal at U241- 8 is run through a matching
network. The resulting LO RF INJECTION RF signal is applied to the mixer at T302.
When PTT is pressed during the transmit condition, five volts is applied to U241-19. This activates the
transmit VCO by enabling the U241 transmit oscillator and buffer. The TX RF INJECTION signal at
Table 2-2
Level Shifter Logic
Desired Mode
AUX 4
AUX 3
TRB
Tx
Low
High (@3.2V)
High (@4.8V)
Rx
High
Low
Low
Battery Saver
Low
Low
Hi-Z/Float (@2.5V)
Presc
Rx
Tx
Matching
Network
Low Pass
Filter
Attenuator
Pin8
Pin14
Pin10
Level Shifter
Network
5V
(U201 Pin28)
VCC Buffers
Tx RF Injection
U201 Pin 32
AUX4 (U201 Pin3)
AUX3 (U201 Pin2)
Prescaler Out
Pin 12
Pin 19
Pin 20
Tx/Rx/BS
Switching Network
U241
VCOBIC
Rx
Active Bias
Tx
Active Bias
Pin2
Rx-I adjust
Pin1
Tx-I adjust
Pins 9,11,17
Pin18
Vsens
Circuit
Pin15
Pin16
Rx VCO
Circuit
Tx VCO
Circuit
Rx Tank
Tx Tank
Pin7
Vcc-Superfilter
Collector/RF in
Pin4
Pin5
Pin6
Rx
Tx
(U201 Pin28)
Rx-SW
Tx-SW
Vcc-Logic
(U201 Pin28)
Steer Line
Voltage
(VCTRL)
Pin13
Pin3
TRB_IN
LO RF INJECTION
VSF
VSF
VSF
Содержание PRO3150
Страница 30: ...2 20 Voltage Control Oscillator VCO ...
Страница 56: ...4 6 Speaker Microphone Schematic This page intentionally left blank ...
Страница 100: ...4 50 This page intentionally left blank ...
Страница 101: ......