| Open source SPM Controller & PLL, Model MK3-PLL |
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The open-source SPM Controller & PLL can be used as:
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Ultrathin Bi(111) film on a Si(111)-7x7 substrate
Images provided by, C.A. Bobisch, M.C. Cottin, J. Schaffert and R. Möller
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- A SPM controller
- A stand alone PLL
- A controller with an embedded PLL
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This MK3-PLL model is fully compatible with the SPM control software developed by the GXSM Group. This model has more computation power and memory than the MK2-A810 model, which allows for further developments and improvements of the next generation of the GXSM control code.
The major addition to this model is the embedded PLL module.
The PLL Module
The PLL module is based on an innovative phase/amplitude measurement technique that controls both the phase and the amplitude of the resonator signal (patent-pending).
Schematic of the PLL algorithm :
Key Features
- The speed/noise trade-off is independent of frequency range, which provides tracking capability on the entire frequency range with lower noise
- Includes a function to automatically measure the resonator frequency response and characteristics: frequency and phase at resonance, Q factor & gain at resonance
- Includes an auto-set feature to automatically set the loop gains to achieve the desired response
- 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 the noise without altering the controller bandwidth
- The PLL module includes a function for long-term analysis of the PLL signals, assessing thermal drift and low frequency noise
SPM Control with Embedded PLL
This digital PLL can be implemented as a module of the SPM controller's firmware. Thus, high resolution input and output signals are directly accessible in digital form. No DAC/ADC conversions take place between the PLL and SPM controllers, as is the case with a stand-alone PLL. This provides greater precision and lower group-delay for a faster loop response.
The new generation of the GXSM control code will include this embedded PLL.
Stand-Alone PLL
This Mk3-PLL unit can also be used as a stand alone PLL unit. This means that a personalized SPM controller can be used with the MK3-PLL unit as an external powerful PLL. (For more information, download the Open Source PLL user guide below).
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