## UHF-PID Key Features

- 4 independent PID controllers
- PID Advisor with multiple DUT models, transfer function and step function modeling to achieve an adjustable target bandwidth
- Auto Tune PID that automatically minimizes the average PID error signal by adjusting various set of parameters and bandwidth
- High speed operation with up to 300 kHz loop filter bandwidth
- Input parameters: demodulator data, auxiliary inputs, auxiliary outputs and arithmetic unit
- Output parameters: Output Amplitudes, Oscillator frequencies, Demodulator Phase, Auxiliary Outputs and Signal Output Offsets
- Phase unwrap for demodulator Θ data (± 1024 π), e.g. for optical phase locked loops
- Low pass filter for derivative branch

## UHF-PID Upgrade and Compatibility

- Option upgradeable in the field
- Compatible to all other UHF options

## UHF-PID Applications

- Laser frequency stabilization
- Optical Phase locked loop, e.g. carrier envelope offset stabilization (CEO)
- High-speed AFM, e.g. automatic gain control (AGC)
- MEMS measurements, e.g. gyroscopes
- Interferometer stabilization
- Nano-mechanical oscillators

## UHF-PID Functional Diagram

### Phase Locked Loop

One important application of the PID controllers is the phase coherent synchronization of two oscillators - Phase Locked Loop or PLL. The most simple case is whenever a signal is provided to the lock-in amplifier as an external frequency reference and then automatically mapped to one of the internal oscillators by setting either demodulator 4 or 8 to ExtRef. One PID would then take the phase information from one of the demodulators as an input and provide feedback to the frequency of one of the internal oscillators. It is important to know that this principle can also be reversed and the good phase noise properties of the internal oscillators can for example be transferred to an external setup such as a laser system.

### Arithmetic Unit

The Arithmetic Unit can be used in combination with the PID controllers and allows to perform basic mathematical operations for instance on demodulator data before providing the result as input for the PID. A simple example is the stabilization of an interferometer where the calculation of a phase angle based on atan2(Y/X), where the X component is taken from the fundamental frequency and the Y component of the 2nd harmonic multiplied with a normalization factor, can be used for feedback.

### PID Advisor and Auto Tune

## UHF-PID Specifications

Configuration | 4 PID controllers with PLL capability |

PID input parameters | X, Y, R, and Theta from demodulators 1 to 8, auxiliary inputs 1 and 2, auxiliary outputs 1 to 4 |

PID output parameters | Amplitude of signal outputs 1 and 2, signal output offsets, frequency of oscillators 1 to 8, auxiliary outputs 1 to 4 |

PID bandwidth | up to 300 kHz |

PID minimum propagation delay | 1.5 µs (Signal Input to Signal Output) |

PLL frequency range | 10 Hz - 600 MHz |

PLL bandwidth | up to 300 kHz |