Motorola Astro Digital Mobile Radio Xtl5000 Detailled 6881096c74 B Manual

6881096C74-BMay 25, 2005
Product Overview: Transmitter Section2-9
The back-end is primarily the ABACUS III digital IC. The ABACUS III IC uses a variable-bandwidth 
bandpass sigma-delta architecture. It is capable of down-converting analog as well as digital RF 
protocols into a baseband signal, which is then transmitted over the Synchronous Serial Interface 
(SSI) bus to the DSP and microprocessor.
2.4.3 700–800 MHz Band Radios
The 700–800 MHz receiver consists of a front-end section and a back-end...

May 25, 20056881096C74-B
2-10Product Overview: Frequency Generation Unit
2.5.3 700–800 MHz Radios
The 700–800 MHz transmitter consists of an RF power amplifier (RFPA), output network (ON), and 
power control.
2.5.3.1  RFPA
The RFPA is a three-stage, discrete-LDMOS transistor amplifier consisting of the following stages: 
first, driver, and final.
The first stage acts as a variable-gain amplifier and feeds the driver stage, which, in turn, feeds the 
final stage. All of the stages are matched using...

6881096C74-BMay 25, 2005
Product Overview: Frequency Generation Unit 2-11
• Associated circuitry
The reference oscillator IC provides a frequency standard to the Fractional-N synthesizer IC, the 
ABACUS III digital back-end IC, and the controller section. The synthesizer turns on one of the four 
VCOs (determined by mode and band of operation) and tunes it to the receiver (RX) local oscillator 
(LO) or transmitter (TX) carrier frequency.
All four voltage-controlled oscillators (VCOs) employ a discrete...

May 25, 20056881096C74-B
2-12Product Overview: Controller Section
The voltage-controlled oscillator (VCO) module employs a Colpitts configuration with two bipolar 
stages in a common-base, common-collector configuration. The LC tank circuits capacitive portion 
consists of a varactor diode, coupling capacitor, and a laser-trimmed capacitor for frequency 
adjustment. The inductive portion consists of microstrip transmission line resonators for TX VCO and 
coaxial resonators for RX VCO. Tuning is performed...

6881096C74-BMay 25, 2005
Product Overview: Controller Section2-13
2.7.2 Digital (ASTRO) Mode of Operation
In the ASTRO mode (digital mode) of operation, the transmitted or received signal is limited to a 
discrete set of deviation levels, instead of continuously varying. The receiver handles an ASTRO-
mode signal identically to an analog-mode signal up to the point where the DSP decodes the 
received data. In the ASTRO receive mode, the DSP uses a specifically defined algorithm to recover 
information....

May 25, 20056881096C74-B
2-14Product Overview: Controller Section
The DSP section of microprocessor performs signaling, voice encoding/decoding, audio filtering, 
microphone gain and tuning, Private-Line/Digital Private Line (PL/DPL) encode, and alert-tone 
generation. It processes all baseband audio signals, providing pre-emphasis and signaling/filtering of 
the digital microphone audio data, as well as other transmitted signals. It also performs de-emphasis 
and decoding of received digital speaker...

Chapter 3 Theory of Operation
3.1 Main Board
This section provides a detailed circuit description of the XTL 5000 radio main board for VHF/UHF 
Range 1/UHF Range 2/700–800 MHz models. The main board contains the following major 
sections:
• Radio Power (page 3-12)
• Receiver Front-End (page 3-13)
• Receiver Back-End (page 3-20)
• Transmitter (page 3-26)
• Frequency Generation Unit (page 3-45)
• Controller (page 3-62)
When reading the theory of operation, refer to your appropriate schematic and component...

May 25, 20056881096C74-B
3-2Theory of Operation: Main Board Major Sections
Figure 3-1.  XTL 5000 Main Board Sections (VHF Mid Power)—Side 1
Table 3-1.  XTL 5000 Main Board Sections (VHF Mid Power)—Side 1
1 Secure Connector (J0501) 8 Controller Section
2 Front Connector (J0401) 9 Audio Power Amplifier (PA)
3 RX Back-End (ABACUS III) 10 RX VCO
4 16.8 MHz Reference Oscillator 11 TX VCO
5 IF Filter 12 TX PA
6 RX Front-End 13 TX Power Control
7 Daughtercard
12
3 4
5
6 7 8
910
11
1312 

6881096C74-BMay 25, 2005
Theory of Operation: Main Board Major Sections 3-3
Figure 3-2.  XTL 5000 Main Board Sections (VHF Mid Power)—Side 2
Table 3-2.  XTL 5000 Main Board Sections (VHF Mid Power)—Side 2
3 RX Back-End 16 Antenna Switch
5 IF Filter 17 Rear Connector (J0402)
6 Controller Section 18 RX Front-End Biasing
12 TX PA 19 RX VCO Injection Stage
13 TX Power Control 20 TX VCO Injection Stage
14 Power Detector 21 FGU (Synthesizer)
15 Harmonic Filter
5
3
21
19
18
20
6
141516
1217
13 

May 25, 20056881096C74-B
3-4Theory of Operation: Main Board Major Sections
Figure 3-3.  XTL 5000 Main Board Sections (VHF High Power)—Side 1
Table 3-3.  XTL 5000 Main Board Sections (VHF High Power)—Side 1
1 Secure Connector (J0501) 8 Controller Section
2 Front Connector (J0401) 9 Audio Power Amplifier (PA)
3 RX Back-End (ABACUS III) 10 RX VCO
4 16.8 MHz Reference Oscillator 11 TX VCO
5 IF Filter 12 TX PA
6 RX Front-End 13 TX Power Control
7 Daughtercard
2
1
35
10
6 11
12 9
13 4
7 8