Motorola Sse 5000 6881094c12 A Manual

6881094C12-ANovember 11, 2004
Theory of Operation: Transceiver Board2-9
2.4.1.5  Power Conditioning Components
DC power-conditioning components include zener diodes, capacitors, ferrite beads, a power 
inductor, and the fuse. Diodes VR1 and VR2 provide over-voltage protection. Ferrite beads 
(designated E1, E4, E101) and capacitors suppress electromagnetic interference from the 
transceiver. The power-line filter consisting of L1, C13, and C14 suppresses digital noise from the 
VOCON board switching...

November 11, 20046881094C12-A
2-10Theory of Operation: Transceiver Board
2.4.2.1.2  LNA (Low-Noise Amplifier)
The SSE 5000 radio uses a discrete transistor for the low-noise amplifier (Q430). A feedback 
network between the collector and base improves stability and gain balance across the frequency 
band. Input and output LC networks match the LNA impedance to 50 ohms.
A diode limiter (D400) protects the amplifier damage by strong input signals.
2.4.2.1.3  Mixer
The mixer (U470) down-converts the...

6881094C12-ANovember 11, 2004
Theory of Operation: Transceiver Board2-11
Figure 2-5.  Abacus III (AD9874) Functional Block Diagram
Input signal RXIF is 73.35 MHz IF from crystal filter FL400 in the receiver front-end. Components 
L547 and C542 match the input impedance to 50 ohms.  Formatted SSI data is output to the VOCON 
board on ports FS, DOUTA, and CLKOUT.
2.4.2.2.2  Second Local Oscillator
The second LO is controlled by the Abacus LO synthesizer, which mixes with IFIN to produce a 2.25 
MHz final...

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2-12Theory of Operation: Transceiver Board
control IC (PCIC) that senses the output of a directional coupler and adjusts PA control voltages to 
maintain a constant power level. The signal passes through a dual antenna switch and harmonic 
filters to the antenna or to the remote RF port.
Figure 2-6.  Transmitter Block Diagram
2.4.3.1  Power Distribution
To minimize voltage drop to the power amplifiers, net RAWB+ connects to power module Q107 and 
the second stage of driver...

6881094C12-ANovember 11, 2004
Theory of Operation: Transceiver Board2-13
2.4.3.4  Directional Coupler
A directional coupler senses the transmitter forward power as a control signal in the transmitter’s 
automatic level control (ALC) loop. Isolated ports are terminated with external resistors.
The directional coupler is U101, a low-loss, bidirectional coupler.
2.4.3.5  Antenna Switch 
The SSE 5000 has two antenna switches: one standard antenna switch and a remote antenna 
switch. 
The standard antenna...

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2-14Theory of Operation: Transceiver Board
The initial design utilizes a cutoff frequency of 750 MHz, even though the actual design cutoff 
frequency is 488 MHz. The reasoning behind using a significantly higher cutoff frequency is due to 
the lower frequency response of realized circuits. The design tables used for the filter synthesis can 
be located in the Handbook of Filter Synthesis (Zverev, pp. 218–219), where θ = 47.0. This design 
was chosen because the attenuation...

6881094C12-ANovember 11, 2004
Theory of Operation: Transceiver Board2-15
2.4.3.8.1  Power and Control
Since U104 is powered from switched B+, it makes its own regulated 4.5 Vdc to power the internal 
logic. The supply input is V5EXT at pin 17, and the output is V45 at pin 16. ANO at pin 32 is the 
control signal to the RX/TX antenna switch control circuit.
2.4.3.8.2  Automatic Level Control (ALC)
In TX mode, the PCIC disables the receiver, turns on the transmitter, and controls the TX power 
level. The...

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2-16Theory of Operation: Transceiver Board
The output is a DC voltage at pin 2 (VOUT) proportional to the temperature at pin 3 (GND). VOUT is 
750 mV at 25°C and increases by 10 mV/°C. The PCIC temperature cut-back threshold is 
programmed to correspond to 85 or 90°C. Above this threshold, the ALC gradually cuts back the 
transmitter until it is fully turned off at 125°C. The slope of cut-back versus temperature is set by 
external resistor R111. Diode D104 clamps TEMP to a...

6881094C12-ANovember 11, 2004
Theory of Operation: VOCON Board2-17
2.4.4.2.3  Modulation
To support many voice, data, and signaling protocols, the SSE 5000 radio must modulate the 
transmitter carrier frequency over a wide audio frequency range, from less than 10 Hz up to more 
than 6 kHz. The FracN supports audio frequencies down to zero Hz by using dual-port modulation. 
The audio signal at pin 10 (MODIN) is internally divided into high- and low-frequency components, 
which modify both the synthesizer...

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2-18Theory of Operation: VOCON Board
• Controller and Memory: The dual-core processor (U401) with the microcontroller unit (MCU) 
and a digital signal processor (DSP) in a single integrated circuit (IC) package, the SRAM 
(U403) and Flash (U402) memory devices.
• Audio and Power: The GCAP II (U501), a 5 Vdc linear regulator (U505), a 1.55 Vdc linear 
regulator, the audio pre-amplifier (U502), the audio power amplifier (U503), and the dual 
EEPOT (U509).
• Interface Support:...