1-9
System Description
602-13729-01 Rev B
Expedio Digital Electronic News Gathering Radio
1.5.3 RF Double Upconverter
E xp ed io D o ub le U p -C on verter
M IC R O C O N TL R
EX C IT ER O U T
+ 5 d B m
199 0-211 0 M H z
245 0-250 0 M H z
R E F O S C
I6 M H Z
IN TE R N AL
D C
C O N V E R TE R S
B AC K P L AN E IN TE R FAC E
70 M H z
R F IN
-10 d B m
I2
C
+12
V
+5 Vdc/
200 m A
+10 Vdc/
250 m A
ALC
PA
t
e
le
m
S Y N TH
550 M H Z
48 0 M H Z
C O N V E R T E R
70MHZ/
9MHZ
480MHZ/
25MHZ
AG C 45dB
13dB
14dB
S Y N TH
1.5 1-1.63 G H Z
1.9 7-2.02 G H Z
2-2.5 G H Z
C O N V E R T E R
480MHZ/
25MHZ
0-15dB
0-5dB
19dB
17dB
12dB
Figure 8: RF Upconverter Block Diagram
The IF output carrier of the IF Upconverter daughter card is fed to the transmit portion of the RF
Module via an external (rear panel) semi-rigid SMA cable. This module performs the necessary
upconversion to the RF carrier. There is an on-board CPU for independent control of the critical
RF parameters of the system.
Since this is a linear RF processing chain, an automatic leveling control loop (ALC) is
implemented here to maintain maximum available power output (and therefore maximum system
gain). The ALC monitors the PA forward power (FWD) output sample, and controls the up
converter gain per an algorithm programmed in the CPU. The ALC also controls the power-up
RF conditions of the transmitter output.
1.5.4 Power
Amplifier
(PA)
The Power Amplifier (PA) is a separate module that is mounted to a heat sink and is fan-cooled
for reliable operation. The PA is a design for maximum linearity in an amplitude modulation-based
system.
