Basic Theory of Operation
: Analog Mode of Operation
3-3
3.2
Analog Mode of Operation
This section provides an overview of the analog mode receive and transmit theory of operation.
3.2.1
Receiving
The RF signal is received at the antenna and is routed through the Harmonic Filter, followed by the Antenna
Switch and finally the 15dB Step Attenuator IC. The latter contains a switchable attenuator that is enabled at
predetermined RF power thresholds present at the antenna port.
Figure 3-2. Receiver Block Diagram (900 MHz)
3.2.1.1 GPS
The GPS signal is tapped at the antenna port via a series resonant network (diplexer) which provides
a very low capacitive load to the transceiver. The diplexer circuitry provides rejection to radio band
signals up to ~1GHz which serves as isolation between the radio RF and GPS signal paths. The
GPS signal is filtered though a GPS SAW filter - LNA – Saw filter chain before going into the TI GPS
IC for processing.
Figure 3-3. GPS Diagram
3.2.1.2 900 MHz Front-End
From the 15 dB Step Attenuator, the 900 MHz band signal is routed to the pre-selector filter. The
output of the prefilter is applied to the first LNA followed by a similar filter as the pre-selector filter.
The signal is then routed to a second LNA whose output is applied to a discrete image filter. Both pre
and post selector filters are Surface Acoustic Wave designs used to band limit the received energy
and suppress known spurious responses such as Image and the ½ IF spur. The output of the
discrete image filter is applied to the RF port of the Mixer IC. The Mixer IC is also excited by a Local
Oscillator (LO) signal at the LO port to down-convert the RF signal to a 109.65 MHz intermediate
frequency (IF). The down converted IF signal is passed through a crystal filter which drives the input
of the Abacus 3 Analog to Digital Converter IC (AD9864).
Antenna
Switch
15 dB Step
Attenuator
900
900
DIG_CTRL_ATTH
To GPS
Diplexer
IF Filter
Rx LO
SSI
18Mhz
CLK
Abacus III
ABACUS III
Dec.
Filter
ΣΔ
ADC
2nd
LO
LO
CLK
To Radio transceiver path
GPS IC
GPS Receiver Circuit
Antenna
OMAP
Processor
Diplexer
Содержание APX 4000
Страница 1: ...APXTM TWO WAY RADIOS APX 1000 APX 2000 APX 4000 APX 4000Li BASIC SERVICE MANUAL ...
Страница 6: ...Notes iv Commercial Warranty ...
Страница 8: ...ii Notes ...
Страница 16: ...x Portable Radio Model Numbering System Notes ...
Страница 46: ...3 12 Basic Theory of Operation Controller Section Notes ...
Страница 60: ...5 12 Performance Checks Transmitter Performance Checks Notes ...
Страница 90: ...6 30 Radio Alignment Procedures Performance Testing Figure 6 41 Transmitter Test Pattern Screen 900 MHz ...
Страница 128: ...8 34 Disassembly Reassembly Procedures Ensuring Radio Submergibility Notes ...
Страница 138: ...10 6 Exploded Views and Parts Lists APX 2000 APX 4000 APX 4000Li Back Kit Exploded View Parts List Notes ...
Страница 142: ...Index 4 Index Notes ...
Страница 143: ...Title Page ASTRO APX 1000 Digital Portable Radios Section 2 VHF UHF1 UHF2 700 800 MHz APX 1000 ...
Страница 144: ...ii Notes ...
Страница 150: ...viii List of Figures Notes ...
Страница 152: ...x Portable Radio Model Numbering System Notes ...
Страница 208: ...6 24 Radio Alignment Procedures Performance Testing Figure 6 30 Transmitter Test Pattern Screen 700 800 MHz ...
Страница 240: ...7 32 Disassembly Reassembly Procedures Ensuring Reliable Splash Protection Notes ...
Страница 250: ...9 6 Exploded Views and Parts Lists APX 1000 Back Kit Exploded View Parts List Notes ...
Страница 254: ...Index 4 Index Notes ...
Страница 255: ...Title Page ASTRO APX 1000 Digital Portable Radios Section 3 900 MHz APX 1000 ...
Страница 256: ......
Страница 262: ...viii List of Figures Notes ...
Страница 264: ...x Portable Radio Model Numbering System Notes ...
Страница 278: ...3 8 Basic Theory of Operation Controller Section Notes ...
Страница 336: ...7 32 Disassembly Reassembly Procedures Ensuring Reliable Splash Protection Notes ...
Страница 346: ...9 6 Exploded Views and Parts Lists APX 1000 Back Kit Exploded View Parts List Notes ...
Страница 350: ...Index 4 Index Notes ...
Страница 351: ...Title Page ASTRO APX APX 2000 APX 4000 Digital Portable Radios Section 4 APX 2000 APX 4000 Two Knobs ...
Страница 352: ...ii Notes ...
Страница 360: ...x Portable Radio Model Numbering System Notes ...
Страница 400: ...5 12 Performance Checks Transmitter Performance Checks Notes ...
Страница 427: ...Radio Alignment Procedures Performance Testing 6 27 Figure 6 34 Transmitter Test Pattern Screen 700 800 MHz ...
Страница 428: ...6 28 Radio Alignment Procedures Performance Testing Notes ...
Страница 434: ...7 6 Encryption Erase an Encryption Key Notes ...
Страница 478: ...8 44 Disassembly Reassembly Procedures Ensuring Radio Submergibility Notes ...
Страница 488: ...10 6 Exploded Views and Parts Lists APX 2000 APX 4000 Two Knobs Back Kit Exploded View Parts List Notes ...
Страница 489: ...Title Page ASTRO APX 1000 APX 2000 APX 4000 APX 4000 Li Digital Portable Radios Section 5 Appendices ...
Страница 490: ...ii Notes ...
Страница 492: ...A 2 Accessories Notes ...
Страница 496: ...Notes B 4 EMEA Warranty Service and Technical Support Further Assistance From Motorola ...
Страница 500: ...C 4 LACR Replacement Parts Ordering and Motorola Service Centers Motorola Service Centers Notes ...
Страница 520: ...Glossary 12 Glossary Notes ...
Страница 524: ...Index 4 Index Notes ...
Страница 525: ......