Senstar Corporation B76060 사용자 설명서
PPD Maintenance & Technical Manual
4.4.2 Voltage
Controlled Oscillator (VCO)
The VCO was implemented using a Motorola MRF917 BJT in a Colpitts oscillator configuration. The
design provides a tuning frequency range of 420 – 475 MHz. For interference and EMI reasons, the
VCO and VCO buffer circuits are enclosed in a shield that clips to the PCB.
design provides a tuning frequency range of 420 – 475 MHz. For interference and EMI reasons, the
VCO and VCO buffer circuits are enclosed in a shield that clips to the PCB.
The VCO varactor diode input is driven by the output of the PLL loop filter, setting the instantaneous
transmitter frequency. The varactor is capacitive coupled into the VCO’s L-C tank circuit.
transmitter frequency. The varactor is capacitive coupled into the VCO’s L-C tank circuit.
4.4.3 VCO
Buffer
Amplifier
The VCO buffer amplifier was implemented using an NEC/CEL NE85639 bipolar RF transistor. The
VCO buffer amp provides isolation and gain for the VCO output. The buffer amp provides
approximately 13-15 dB of gain at its output.
VCO buffer amp provides isolation and gain for the VCO output. The buffer amp provides
approximately 13-15 dB of gain at its output.
The VCO buffer amplifier uses an RF-bypassed emitter-degeneration bias arrangement for good
temperature stability. The buffer’s input impedance is high so that loading effects on the VCO are
minimized.
temperature stability. The buffer’s input impedance is high so that loading effects on the VCO are
minimized.
4.4.4 Reference Oscillator (VCTCXO)
The reference oscillator is a 10MHz voltage-controlled temperature compensated crystal oscillator
(VCTXCO). It is manufactured by TEMEX, part number TTF 95V AAO 10.000. The voltage-
controlled input of the reference oscillator has two functions, 1) frequency adjust via the dc offset on
the voltage-controlled pin and 2) transmit modulation via an ac signal superimposed on the dc offset.
(VCTXCO). It is manufactured by TEMEX, part number TTF 95V AAO 10.000. The voltage-
controlled input of the reference oscillator has two functions, 1) frequency adjust via the dc offset on
the voltage-controlled pin and 2) transmit modulation via an ac signal superimposed on the dc offset.
The VCTCXO voltage-control port is driven by the base band modulation waveform at an associated
dc-offset, thus driving both the PPD’s carrier frequency and deviation. Carrier frequency and average
deviation are set by measuring the PPD in Test Mode with a modulation analyzer, then adjusting the
base band modulation waveform’s mid, low, and high voltages. These values are saved in the
controller’s EEPROM.
dc-offset, thus driving both the PPD’s carrier frequency and deviation. Carrier frequency and average
deviation are set by measuring the PPD in Test Mode with a modulation analyzer, then adjusting the
base band modulation waveform’s mid, low, and high voltages. These values are saved in the
controller’s EEPROM.
The reference oscillator is a 5 volt nominal part, rather than 3.3 volts, and gets its supply voltage from
the same +5V regulator as the charge pump of the synthesizer. This was done to maximize the
voltage-tuning range of the VCTCXO function to encompass a) modulation, b) carrier frequency trim,
c) unit-unit variations, and d) crystal aging.
the same +5V regulator as the charge pump of the synthesizer. This was done to maximize the
voltage-tuning range of the VCTCXO function to encompass a) modulation, b) carrier frequency trim,
c) unit-unit variations, and d) crystal aging.
T1DA0502-001, Rev A
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