Product specifications

Ku-Band Satellite Transceiver Revision 9

Operation MN/KST2000AB.IOM

3–22

3.7 Reference Oscillator

The reference oscillator assembly (Figure 3-12) consists of a high stability, 10 MHz,

Oven Controlled, Voltage Controlled, Crystal Oscillator (OCVCXO), a 72 MHz oscilla-

tor, and a micro-controller.

Figure 3-8. Reference Oscillator

The reference oscillator assembly can accept an external 5 or 10 MHz input signal ≤ +6

dBm. The reference oscillator has an onboard phase detector which is used to frequency

lock the 10 MHz oscillator to the external reference. A bias voltage output from the phase

detector is read into the microcontroller via an A to D converter. The

microcontroller interprets this bias voltage and generates a tuning voltage output propor-

tional to the phase/frequency difference between the onboard oscillator and the external

reference input. This output is applied to the tuning voltage input on the OCVCXO to

shift its operating frequency to maintain frequency lock with the external input.

The 10 MHz OCVCXO is a high stability, low phase noise, crystal oscillator. It has a tun-

ing voltage input which can be used to fine tune the oscillator frequency. When the

KST-2000A/B is operating without an external 5 or 10 MHz input, the M&C generates a

bias voltage which can be changed remotely. That sets the oscillator frequency.

When an external reference is applied, the KST-2000A/B will generate a bias voltage of

sufficient level to keep the 10 MHz reference frequency locked to the external input. The

10 MHz output is amplified and distributed to the down converter, where it is the refer-

ence for the DROs. It also serves as the reference frequency for the 72 MHz oscillator.

The 72 MHz VCXO is phase locked to the 10 MHz reference. The 72 MHz output of the

VCXO is amplified and distributed throughout the KST-2000A/B to provide a reference

frequency for the up converter and portions of the down converter.

PHASE

DETECTOR

MICRO

CONTROLLER

FAULT /

STATUS

10 MHz OCVCXO

72 MHz

GENERATOR

I2C

EXTERNAL

REFERENCE