User's Manual

Eclipse2 Technical Manual, 3-Aug-12 Page 15 of 17
4dB. The network (C28, C74, L29, L15, L16 and R20) passes the IF frequency of 45 MHz and
t
e
rm
inates the RF and LO components.
The Local Oscillator (LO)
The LO is a Voltage Controlled Oscillator (Q2) which oscillates at the required transmitter output
frequency. Varactor diodes (D2, D9 - D11) are used by the PLL and bias control circuits to keep the
oscillator on the desired frequency. Transistor Q1 is used as an active filter to reduce the noise on
the oscillator supply voltage. Monolithic amplifiers U1, U2 and transistor Q6 amplify the VCO output
to approximately +16dBm then feed to the mixer via a 3dB pad.
The Phase Locked Loop (PLL)
The frequency reference for the PLL is from the Interface board via a 20pin connector. A
fractional-N PLL synthesiser (U10) is used in the RX module, PLL frequency PLL is set by DSP via
the serial bus. The phase detector output (charge pump) signal of U10 is smoothed and filtered by
the loop filter to form the tuning voltage for the VCO circuit.
The IF Amplifier
The first IF amplifier uses two parallel connected JFET transistors Q3 and Q4 to obtain 8-10 dB
gain. The two transistors provide improved dynamic range and input matching over a single
transistor. A 4-pole 45 MHz crystal filter (FIL1, FIL2) is used between the first and second IF
amplifiers. The second IF amplifier (U3, U5) provides additional 35dB gain to drive the digital IF. A
two pole crystal filter (FIL3) is used as an anti-alias filter of the digital IF.
The Data Storage
Each RX module has an EEPROM for storing the individual module information such as, TX module
serial number, model name, frequency range, calibration data etc. This is allows user to simply
replace the RX module in the transceiver without redo the alignment and calibration. The data is
transferred between EEPROM and RISC processor via the serial bus.
Field alignments
As the TX and RX module is pre-tuned for the whole operational frequency range and level
adju
stment of signal path is done by software (local or remotely), there is no field alignment
required for optimizing the performance.
Specifications
Description
The transceiver is a digitized, software upgradable radio, The exciter and the receiver can be
configured as base station, repeater or the stand-alone unit. For base station use, the exciter
normally drives a high power external RF amplifier. It can also be used alone in lower power
applications. The output power can be preset between 0.3 and its maximum. All necessary control
and 600 ohm line interface circuitry is included.
Channel Capacity
Although most applications are single channel, it can be programmed for up to 256 channels (from
CH0 to CH255). Each channel can have it’s own name, TX/RX frequencies and profiles.
Sub Audio Signaling
Full EIA CTCSS capability as well as nonstandard sub tones are built into the modules. The CTCSS
ton
e can be programmed for each channel in their profiles. This means each channel can represent
a unique TX/RX and tone frequency combination.