The SK633 Low-Noise Phase-Lock Controller was designed to transfer the phase of an RF reference signal to the controlled signal. The latter may be the output of a VCO in a classical PLL or a laser beat note in an OPLL. To achieve low-noise operation, the SK633 circuitry relies on a high-performance phase/frequency detector (PFD) and a low-noise analog loop filter. In addition, no prescalers are used on the RF inputs, keeping the intrinsic closed-loop phase noise limited by the PFD noise floor. Contact us if frequency dividers are required for your application.

The SK633 also provides monitoring signals and access for an external compensator when specific loop-gain shaping is required, e.g. in composite servo loops where two paths are combined to achieve low phase noise over a wide bandwidth. To reduce external hardware, two optional loop filter stages are provided for advanced users. Using these optional stages, the loop gain response can be high-order to match specific loop-gain shapes (circuit diagrams available on request).

The SK633 can be associated with the SK657 Ultra-Low Noise Current Source for phase-locking low-power laser diodes when in-band phase noise is a primary concern. Like all modular instruments of the SK-Series, the SK633 Low-Noise Phase-Lock Controller can be operated stand-alone or within a platform, where several modules can be assembled to configure a specific control or measurement system.

Remote operation uses a simple four-letter command language with straightforward set/query syntax, allowing the SK633 to be controlled directly from any standard serial terminal or from user software. The SK633 also includes a built-in streaming facility for periodic transmission of selected measurements and status values, simplifying real-time monitoring and data acquisition. A Python control library is provided for direct access to instrument commands, streaming functions and register decoding, together with a pySerial quick-start example.

• Ultra-low noise phase detection
  • no input prescalers (N=1)
  • FOM = -233dBc @ f ≥ 10kHz
  • high-frequency operation: 10MHz to 1GHz 
• Low-noise,  Proportional-Integral loop filter
  • en < 10nV/√Hz @ f ≥ 1kHz, RTI
  • 8 programmable corner frequencies
  • 2 additional filter stages for advanced loop shaping
• Remote interface
• Powerful built-in signal streaming
• Python control library included
• Stand-alone or platform operation

• Functional block diagram (pdf)
• Programming guide (pdf)
• Python control library (zip)

• Adapters for SK-Series modules
• Platforms for SK-Series modules
• Time/Frequency products
• SK-Series modular instruments