CIRCUIT DESCRIPTION
5-3
Figure 5-1 VHF RF Board Block Diagram (Version C)
I
L
R
I
R
L
PA
64.455 MHz
15 kHz
15 kHz
LNA
T/ R Switch
Antenna
Harmonic
Filter
BPF 1
BPF
1
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1Kbit
EEPROM
SPI
SPI
MISO
SPI
MOSI
SPI
Clk
SPI
Addr1
SPI
Addr2
RF
Clk
RF
Data
RF
Frame
Sync
Power Control
nTxEna
TxMod1
nTxNap
Temp
Lock
Detect
TxMod2
Lock
Enable
Unswitc
h
Batt
3.3V
5.5V
SPI
Addr3
RF / Logic
Interface
SPI Addr
Receiver
Back End
RFOut
SPI
8 ch
DAC
SPI
BPF 2
LO
BPF
D0-D5
VCO
16.8
MHz
VCXO
DRIVER
200 - 239 MHz
136 - 174 MHz
136 - 174 MHz
SPI
RX PLL
RF
PD
REF
D0-D5
VCO
SPI
TX PLL
RF
PD
REF
374.4 MHz
16.8
MHz
VCXO
SPI
RF Out
Low Frequency
Modulation
Switch
1
C
2
2
1
C
High Frequency Modulation
SPI
Reference
PLL
RF
PD
REF
Mixer and LO Filter
A double-balanced, low-level ADEX-10L mixer
(MX1) with a LO drive level of +4 dBm is used for the
first conversion. This mixer provides a good dynamic
range with a 3 dB lower LO drive than the more tradi-
7 dBm drive mixers. This reduces power
consumption and also the conducted and radiated local
oscillator leakage from the receiver.
High side injection is used to provide optimum
spurious performance. A LO filter prior to the mixer
LO port reduces wideband noise from the LO synthe-
sizer which improves receiver sensitivity.
IF Filter and Amplifier
A two-pole 64.455 MHz crystal filter (U2) is used
to provide the desired level of adjacent channel rejec-
tion while providing minimal amplitude and phase
distortion within a 25 KHz bandwidth. Shields are
installed around the crystal filter to provide sufficient
isolation to meet the second image response specifica-
tions and to minimize noise pickup by the impedance-
matching inductors (L1, L2, L3, L4 and L7.)
A transistor IF amplifier (Q1) and supporting
circuitry is required to boost the signal strength,
thereby reducing the overall noise figure. The noise
figure, signal gain, intercept point, and power
consumption are optimized in this design. An addi-
tional two-pole 64.455 MHz crystal filter (U25) is
used to increase the adjacent channel rejection. An LC
circuit provides the required impedance matching
between the output of the IF filter and the input of the
backend chip (U11.)
Back End IC
An Analog Devices AD9864 IF Digitizing
Subsystem IC (U11) provides a variety of functions
for the receiver as follows:
Second Local Oscillator - A varactor-tuned tran-
sistor (Q2) oscillator is phase-locked to a fixed
frequency of 62.355 MHz for converting the first
VHF RF BOARD (VERSION C)
Summary of Contents for 5100 Series
Page 85: ...8 9 Version C Board see Section 1 13 VHF RF BOARD VER C LAYOUT ...
Page 87: ...8 11 VHF RF BOARD SCHEMATIC VER B PAGE 2 OF 3 ...
Page 88: ...8 12 VHF RF BOARD SCHEMATIC VER B PAGE 3 OF 3 ...
Page 95: ...8 19 BOTTOM VIEW TOP VIEW Version C Board see Section 1 13 UHF RF BOARD VER C LAYOUT ...
Page 105: ...8 29 BOTTOM VIEW TOP VIEW 700 800 MHZ RF BOARD VER C LAYOUT Version C Board see Section 1 13 ...
Page 112: ...8 36 SEM Module 5500 120 LOGIC BOARD VER C SCHEMATIC PAGE 5 OF 11 ...
Page 113: ...8 37 Analog Switch 5500 120 LOGIC BOARD VER C SCHEMATIC PAGE 6 OF 11 ...
Page 118: ...8 42 5500 120 LOGIC BOARD VER C LAYOUT BOTTOM VIEW TOP VIEW Version C Board see Section 1 13 ...
Page 143: ...8 67 5500 420 USER INTERFACE BOARD VER C TOP VIEW Version C Board see Section 1 13 ...
Page 144: ...8 68 5500 420 USER INTERFACE BOARD VER C BOTTOM VIEW ...
Page 148: ...8 72 5100 410 USER INTERFACE BOARD VER A BOTTOM VIEW Version w o encryption module ...
Page 152: ...8 76 5100 450 USER INTERFACE BOARD VER B BOTTOM VIEW Version with EFJ SEM ...
Page 156: ...8 80 5100 460 USER INTERFACE BOARD VER B BOTTOM VIEW Version with Motorola UCM ...
Page 172: ...9 15 OBSOLETE VERSION 5100 410 USER INTERFACE BOARD VER A BOTTOM VIEW Revision 6 Board ...
Page 173: ...Part Number 001 5100 0017CD 12 04hph Printed in U S A ...