HARRIS OWDTR-0006-E Users Manual

OWDTR-0006-E Exhibit 8 Com-Net Ericsson

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INSTRUCTION BOOK (DRAFT)
SPD-2000 800MHz

1. Receiver Circuit
The FM dual-conversion super heterodyne receiver is designed for operation in the 851-870 MHz
frequency range. The Receiver has intermediate frequencies (IF) of 115.65MHz and 450kHz. Adjacent
channel selectivity is obtained by using two band pass filters, a 115.65MHz crystal filter and a 450kHz
ceramic filter. The RX detector is the phase digitizer.

1-1 Receiver Front-end
A RF signal from antenna is coupled though the low pass filter/antenna switch, a nd band pass filter t o
the input of low noise amplifier Q101. The output of Q101 is coupled through band pass filter to input
of 1’st Mixer Z101. Front End selectivity is provided by these band pass filter.

1-2 1’st Mixer
The 1’st Mixer is a Double-Balanced-Mixer Z101, that converts a RF signal the 851-870MHz range to

115.65MHz 1’st IF frequency. The signal on the output of Z101 is provided to the input of 1’st IF
amplifier Q102.

1-3 1’st IF
The 1’st IF signal 115.65MHz from the output of the 1’st Mixer is coupled through 1’st IF amplifier
Q102 to Crystal filter FL103. The highly-selective crystal filter FL103 provide the first portion of the
receiver IF selecti vit y. The output of the f ilter is c ouple d thr o ugh th e i mpeda nce- mat c hing net w or k to
IF Receiver U101.

1-4 2’nd Mixer, 2’nd IF filter and 2’nd IF amplifier
IF Receiver U101 is an one-chip IC for digital communication system. It includes 2’nd Mixer, 2’nd IF
amplifier and Limiter amplifier. With the internal circuits of U101, The 1’st IF signal is amplified an
applied to the input of 2’nd Mixer. The 2’nd local injection frequency 115.2MHz is applied from 2’n
local amplifier Q104 to another input of the 2’nd Mixer. The 2’nd Mixer converts a 1’st IF signal

115.65MHz to 2’nd IF frequency 450KHz. Then the 2’nd IF signal is applied to Ceramic Filter
FL105(Wide Band) or FL106 (Narrow Band), which provides the 450KHz selectivity. Those IF filters
are controlled by IF.NARROW signal from the microcomputer (HILLARY:U700). The o utput of the
2’nd IF filter is applied through 2’nd IF amplifier and Cera mic Filter FL104(Wide Band) to Limiter
ampl ifier. This IF si gnal is a mplifie d an d bala nced out puts, R XIF and R XIF, are se nt to HI LLARY.
These two lines, one positive and the other negative, are used to cancel out any noise that might get on
the line. These ba lance outputs is applied to the phase digitizer on HILLARY and detected.

2, Transmitter Circuit
The Tr ansmitter Circuit consists of Modulator IC (U203), Notch Filter, Variable attenuator (CR201),
Buffer Amplifier (U202), Low Pass Filter, PA Module (U201). Automatic Power Control Circuit
(Q207, Q201 and U301), Antenna Switch Module (Z302).

2-1 Modulator IC and Notch Filter
The main VCO, in the synthesizer circuit, is programmed to generate the TX local Injection
frequencies (806 to 815 MHz and 851 t o 870 MHz). The transmitter carrier frequencies are same o
TX local Injection frequencies.
Notch Filter consists of C212, C233, C244, and L210. The output of U203 is applied to Notch Filter
that is through an attenuator pad R204-R206.

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2-2 Variable attenuator
The output of Notch Filter is applied to Variable a ttenuator circuit. Varia ble attenuator circuit consists
of R202, R203, and CR201. The transmitter carrier power is controlled by applying control voltage
from Power Control Circuit. This control voltage is applied through resistor R203 to the anode o
variable capacitor CR201 and R202.

2-3 Buffer Amplifier and Low Pass Filter
The output of Variable attenuator circuit is applied to the Buffer Amplifier U202 that is a mplified to
+6dBm. The collector voltage for U202 is provided Switch circuit and is controlled by DPTT.
Low Pass Filter consists of C207, C208, C232, and L201. The output of U202 is applied to PA module
input through the Low Pass Filter.

2-4 PA Module
The input of the PA Module is amplified to about 3W. B+ (7.5 V dc) is connected U201 through RF
chokes L211. The PA Module consists of two stages RF amplifier. The first stage power supply
voltage is supplied by power control circuit. The second RF amplifier operates in Class-C. This outpu
can be regulated by power control circuit.

2-5 Automatic Power Control
The Automatic Power Contr ol circuit samples the output power to the antenna to maintain a constan
power level across the band. The Automatic Power Control circuit controls the
Module U201.
Directional coupler is include of Antenna Switch Module. Directional coupler provides a sample
signal of transmit power for diode. Diode produce a positive DC voltage proportional to the
transmitter circuit output power level, that is compared to a comparator (U301) from TX POWER
CONT of control unit. The out put of U301 is applied to DC amplifier Q207, then the output voltage o
Q207 controls to the Vcont of PA Module for constant output power level.

2-6 Antenna Switch Module
The Antenna Switch Module consists of switch circuit and the Low Pass Filter.
During transmit, DPTT line from HILLARY is high level. Tra nsistor Q205 turns on supply +7.2V to
Antenna Switch Module Z302. When transmitting, the Antenna switch diode is low impedance.

3. Frequency Synthesizer Circuit
It consists of the Reference Oscillator, PLL Freq uency Synthesizer chip U305, Loop filter, Rx VCO
Z303, and Tx VCO Z304.
PLL Freq u en cy S y nt hesi z er chi p r ec ei ve s P LL da ta , and c on tr ol i nformat i on fr o m t he microc omp ut er
and from this generates the Tx/Rx RF frequencies. It also provides frequency lock status to the
microcomputer.
Rx VCO and Tx VCO are locked to the Reference Oscillator by a single direct-divide synthesis loop
consisting of the Feedback Buffer, Prescaler, and PLL Frequency Synthesizer chip.
The Tx VCO operates over a frequency range of 806-825MHz, 851-870MHz.
The Rx VCO operates over a frequency range of 735.35-754.35MHz.