User guide

KEY FEATURES OF THE PLL MODULE
• The PLL module is based on an innovative (patent-pending) phase/amplitude measurement technique. This technique does
not rely on narrow-band filtering like traditional demodulation techniques. The result is signal capture and tracking capabilities
that encompass the whole frequency range, with better noise and precision/time-constant trade-offs that are independent
of frequency range.
• Allows the control of both the phase and amplitude of the resonator signal.
• Implemented as a module of the SPM controller’s firmware. This way, high resolution input and output signals are directly
accessible in digital form. No DAC/ADC conversions take place between the PLL and SPM controller, as is the case with
a stand-alone PLL. This provides greater precision and lower group-delay for a faster loop response.
• Includes a function to automatically measure the resonator-frequency response and characteristics:
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Frequency and phase at resonance
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Q factor
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Gain at resonance
• Includes a special auto-set feature to simplify the loop-gain set-up. With the auto-set feature, the user only needs to specify
the desired closed-loop response for both controllers. The module automatically sets the loop gains to achieve the desired
response.
• Includes a unique step-response function that allows the in-circuit measurement of the closed-loop response for both the
phase and amplitude loops.
• The PLL module generates the excitation frequency, the excitation amplitude, the resonator phase and amplitude signals.
• Both phase and amplitude loops have an additional output low-pass filter to reduce the noise on all PLL signals.
This filter is automatically adjusted to reduce noise without altering controller bandwidth.
• The PLL module includes a function for long-term analysis of PLL signals. This can be used to assess thermal drift
and low frequency noise.
STAND-ALONE PLL
The SPM controller Mk3 unit can also be used as a stand-alone PLL. Soft dB provides an open source
Windows/LabVIEW-based interface to run the SPM controller Mk3 unit as a stand-alone PLL with four output signals:
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Excitation frequency
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Excitation amplitude
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Resonator phase
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Resonator amplitude
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