UHF Analog Driver/Transmitter/
Chapter 4, Circuit Descriptions
Translator
LX Series, Rev. 3
4-21
V 805
V 804
3 dB Coupler
Z 801
RF
Output
RF
Input
R 814
R 802, ..4, ..5
C 800
C 819
Detector
Output
X 801
+32V
+
R 838
V 810
V 811
V 812
3 dB Coupler
Z 802
3 dB Coupler
Z 803
Figure 4-1: 40 Watt UHF Amplifier Module
V 1
3 dB Coupler
Z 2
RF
Output
RF
Input
3 dB Coupler
Z 1
R 2
R 1
Matching
Network
Matching
Network
V 2
Matching
Network
Matching
Network
Z 3
Z 5
Z 4
Z 6
+Uop
N 1
R 11
R 12
R 9
R 10
Dynamic
Equalization
Figure 4-2. UHF Amplifier Module, 250 Watts
4.6.4 (A3) UHF Module Assembly, RF
Module Pallet, Philips (1300116;
Appendix B)
The UHF Module Assembly, 250-watt
module (Figure 4-2) is a broadband
amplifier for the frequency range 470 to
860 MHz. The amplifier is capable of
delivering an output power of 70 W
rms
.
The amplification is approximately 13
dB.
The amplification circuit consists of the
parallel connected push-pull amplifier
blocks V1 and V2 operating in class AB.
In order to match the transistor
impedance to the characteristic
impedance of the input and output
sides, matching networks are placed
ahead and behind the amplifier blocks.
Transformers Z3 to Z6 serve to balance
the input and output signals. The
paralleling circuit is achieved with the
aid of 3-dB couplers Z1 and Z2.
The working point setting is factory
implemented by means of potentiometers
R9, R11, and R12 and should not be
altered.
4.6.5 (A4) Coupler Board Assembly
(1301949; Appendix B)
The UHF coupler board assembly provides
forward and reflected power samples of the
output to (A5) the amplifier control board
where it connects to the input of the
overdrive-protection circuit.
The RF input to the UHF coupler assembly,
from the 250 Watt UHF amplifier module,
connects to SMA jack J1. The RF is
connected by a stripline track to the SMA
type connector RF Output jack J2. A
hybrid-coupler circuit picks off a power
sample that is connected to SMA type
connector jack J3 as the forward power
sample. Another power sample is taken
from the coupler circuit that is connected
to the SMA type connector jack J6 as the
reflected power sample. Two 50O
