3-14
Theory of Operation:
Transceiver Board
3.1.2.4 UHF2 Front-End
From the first band select switch, U1122, a UHF2 signal is routed to the first pre-selector filter
followed by a Low Noise Amplifier (LNA) and a second pre-selector filter. Both filters are discrete and
tunable designs and are used to band limit the incoming energy and suppress known spurious
responses such as Image spur. The LNA active device is an NPN transistor (U1932) with active bias
provided by transistor pair Q1922. The output of the second pre-selector filter is applied to a discrete
Low Pass Filter (LPF). The output of the LPF is applied to the RF port of the Mixer IC via a second
band select switch, U501. The Mixer IC, U506, is driven by a Local Oscillator (LO) signal generated
by the Trident synthesizer IC, U702, at the LO port to down-convert the RF signal to a 109.65 MHz
intermediate frequency (IF). It is a passive, high linearity design with balanced inputs at the RF and
IF ports and internal LO buffer. The down converted IF signal is passed through a 3-pole crystal filter,
FL501, and an IF amplifier, Q503, which drives the input of the Analog to Digital Converter IC, U601.
3.1.2.5 Analog To Digital Converter
The ADC used in APX is the AD9864 IC, U601, from Analog Devices. The IC front end down
converts the first IF to a second IF, a 2.25 MHz signal, by mixing a 107.4 MHz LO signal generated
by an integrated synthesizer and external VCO with active device U602 and resonator L604. The
second IF is sampled at 18 MHz, a signal generated by an integrated clock synthesizer and VCO
device with external resonator L605.
The sampled signal is decimated by a factor of 900 to 20 kHz and converted to SSI format at the
ADC's output. The Serial Synchronous Interface (SSI) serial data waveform is composed of a 16 bit
in-phase word (I) followed by a 16 bit Quadrature word (Q). A 20 kHz Frame Synch and 1.2MHz
clock waveform are used to synchronize the SSI IQ data transfer to the Digital Signal Processor IC
(OMAP) for post-processing and demodulation. The clock frequency is adjustable and is selected
automatically by software to prevent self quieting.
3.1.3
Transmitter
The transmitter takes modulated RF from the FGU and amplifies it to the rated output power to
produce the modulated carrier at the antenna.
NOTE:
Refer to
Table 8-1, “Transceiver Schematics and Board Overlays,” on page 8-1
for a listing of
transmitter-related schematics that will aid in the following discussion.
The transmitter (
Figure 3-15 on page 3-15
) consists of two LDMOS high power transistors, one for
the VHF band and one for the 7/800 MHz band. The same topology applied for the UHF1/7/800,
UHF2/7/800, UHF1/VHF, UHF1/UHF2 and UHF2/VHF radio where two LDMOS high power
transistors are used to cover each band. This is depicted by
Figure 3-16 on page 3-15
to
Figure 3-20
on page 3-17
. The high power transistor is driven by an RF driver IC that receives its input signal
from the voltage controlled oscillator. Transmitter power is controlled by a discrete power control
circuit that senses the output of a directional coupler and adjusts PA control voltage to maintain the
correct power level. The TX signals pass through their respective harmonic filters, a TX/RX switch,
and embedded directional coupler, a RF switch and then the antenna.
Содержание ASTRO APX 7000
Страница 1: ......
Страница 4: ...iv Document History Notes ...
Страница 24: ...2 4 Radio Power DC Power Routing VOCON Board Notes ...
Страница 98: ...3 74 Theory of Operation Global Positioning System GPS ...
Страница 104: ...4 6 Troubleshooting Procedures Power Up Self Check Diagnostics and Repair Not for Field Use Notes ...
Страница 163: ...Troubleshooting Charts PA Failure 5 59 ...
Страница 164: ...5 60 Troubleshooting Charts PA Failure ...
Страница 168: ...6 4 Troubleshooting Waveforms Clocks 6 2 2 4 MHz Clock Trace 1 Trace recorded at R6113 Figure 6 2 4 MHz Clock Waveform ...
Страница 174: ...6 10 Troubleshooting Waveforms Audio SSI 6 3 3 Sync Trace 1 Trace recorded at R3005 Figure 6 8 Audio SSI Sync Waveform ...
Страница 175: ...Troubleshooting Waveforms Audio SSI 6 11 6 3 4 BCLK Trace 1 Trace recorded at R3006 Figure 6 9 Audio SSI BCLK Waveform ...
Страница 177: ...Troubleshooting Waveforms RX SSI 6 13 6 4 2 DA Trace 1 Trace recorded at R1005 Figure 6 11 RX SSI DA Waveform ...
Страница 178: ...6 14 Troubleshooting Waveforms RX SSI 6 4 3 FSync Trace 1 Trace recorded at R1004 Figure 6 12 RX SSI FSync Waveform ...
Страница 180: ...6 16 Troubleshooting Waveforms TX SSI 6 5 2 DA Trace 1 Trace recorded at R1017 Figure 6 14 TX SSI DA Waveform ...
Страница 181: ...Troubleshooting Waveforms TX SSI 6 17 6 5 3 FSync Trace 1 Trace recorded at R1007 Figure 6 15 TX SSI FSync Waveform ...
Страница 182: ...6 18 Troubleshooting Waveforms SPI 6 6 SPI 6 6 1 CLK Trace 1 Trace recorded at R6605 Figure 6 16 SPI CLK Waveform ...
Страница 183: ...Troubleshooting Waveforms SPI 6 19 6 6 2 CLK INV Trace 1 Trace recorded at R2325 Figure 6 17 SPI CLK INV Waveform ...
Страница 184: ...6 20 Troubleshooting Waveforms SPI 6 6 3 CS Trace 1 Trace recorded at Pin 34 of J2301 Figure 6 18 SPI CS Waveform ...
Страница 185: ...Troubleshooting Waveforms SPI 6 21 6 6 4 MOSI Trace 1 Trace recorded at R6603 Figure 6 19 SPI MOSI Waveform ...
Страница 187: ...Troubleshooting Waveforms I2C BUS 6 23 6 7 2 SCL 5V Trace 1 Trace recorded at R6204 Figure 6 21 I2C Bus SCA 5V Waveform ...
Страница 188: ...6 24 Troubleshooting Waveforms I2C BUS 6 7 3 SDA Trace 1 Trace recorded at R6209 Figure 6 22 I2C Bus SDA Waveform ...
Страница 194: ...6 30 Troubleshooting Waveforms USB 6 10 2 D Trace 1 Trace recorded at Pin 35 of J3001 Figure 6 28 USB D Waveform ...
Страница 196: ...6 32 Troubleshooting Waveforms UART 6 11 2 TX Trace 1 Trace recorded at F_Boot_Tx Figure 6 30 UART TX Waveform ...
Страница 198: ...6 34 Troubleshooting Waveforms SDRAM 6 12 2 CLKX Trace 1 Trace recorded at TP6308 Figure 6 32 SDRAM CLKX Waveform ...
Страница 276: ...7 58 Troubleshooting Tables List of Board and IC Signals Notes ...
Страница 318: ...8 42 Schematics Boards Overlays and Parts Lists Transceiver RF Boards VHF 700 800 Notes ...
Страница 380: ...8 104 Schematics Boards Overlays and Parts Lists Transceiver RF Boards UHF1 700 800 MHz Notes ...
Страница 432: ...8 156 Schematics Boards Overlays and Parts Lists Transceiver RF Boards UHF1 VHF Notes ...
Страница 458: ...8 182 Schematics Boards Overlays and Parts Lists Transceiver RF Boards UHF1 UHF2 Notes ...
Страница 498: ...8 222 Schematics Boards Overlays and Parts Lists Transceiver RF Boards UHF2 700 800 MHz Notes ...
Страница 546: ...8 270 Schematics Boards Overlays and Parts Lists Transceiver RF Boards UHF2 VHF Notes ...
Страница 606: ...8 330 Schematics Boards Overlays and Parts Lists VOCON Boards Notes ...
Страница 638: ...Glossary 10 Glossary Notes ...
Страница 643: ......