HF2PLL Phase-locked Loop

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The HF2PLL Phased-locked Loop is a bundle consisting of

This powerful instrument integrates two 50 MHz phase-locked loops with two independent 50 MHz lock-in amplifiers. The PLLs offer fully configurable support for accurate frequency tracking, while the lock-in amplifiers provide best-in-class signal recovery based on the exquisite analog front end and high resolution fast signal processing. In combination with the PLL Advisor it was never so easy to achieve ultimate phase locking performance in the high-frequency range.

HF2PLL Key Features

  • Dual 50 MHz phase-locked loop
  • 2 fully configurable lock-in amplifiers
  • 2 high-frequency, high-performance signal generators
  • 50 kHz PLL bandwidth with full parameter control
  • 4 fully configurable PID controllers
  • Application pack (included): automatic gain control, tip protection, peak analyzer
  • Application pack (optional): Kelvin probe force microscopy, Q-Control, dual resonance frequency tracking (DFRT), side band analyzer
  • PLL harmonic mode
  • Frequency deviation and dissipation output (jitter-free)
  • LabOne toolset: spectrum, paramteric sweeper, PID/PLL Advisor, oscilloscope, plotter, software trigger
  • Programming interfaces to LabVIEW, MATLAB, Python, C included

HF2PLL Applications

  • Atomic force microscopy (AFM)
  • Scanning tunnelling microscopy (STM)
  • Near-field scan optical microscopy (SNOM, NSOM)
  • Micro electromechanical systems (MEMS)
  • Resonators / Magnetometers
  • Frequency combs: time reference definition
  • Semiconductor characterization and testing

HF2PLL Available Options

HF2LI-MF Multi-frequency

The HF2LI-MF multi-frequency option impressively extends the capability of the HF2LI lock-in amplifier by adding a wide range of configuration alternatives. This largely improves the flexibility of the instrument and enlarges the research horizon of scientists.

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HF2LI-MOD AM/FM Modulation

The HF2LI-MOD is an option for the HF2LI and allows for the direct analysis of sidebands in dynamic AM (amplitude modulation) and FM (frequency modulation) schemes. This option helps the user to precisely measure periodic variations in the frequency or the amplitude of the application signal. Such schemes are typically applied in oscillator and resonator related setups.

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HF2LI-RT Real-time

The HF2LI-RT option consists of a programming environment that enables the user to implement customized software on a powerful embedded Microblaze® processor inside the HF2LI. Plenty of resources to support complex algorithms are provided. This is for instance required by RT (real-time) applications needing fast reaction based of input signal changes. The processor runs free of interrupts and the timing behavior of the software is inherently robust and reproducible.

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HF2PLL Functional Diagram

High-Precision Inputs

The 2 input paths of the HF2PLL are optimized for very low noise operation. The sampling rate of 210 MSa/s is 4 times the analog bandwidth, ensuring full capture of the signal and reducing aliasing.

Quad PID Controller

Four fully configurable PID controllers with a wide selection of input and output units support the efficient implementation of control loops. The advisor and tuning tools greatly simplify the tedious optimization of control parameters. The maximum bandwidth depends on the chosen configuration, but is at least 5 kHz per PID controller for any application.

Demodulators and Filters

The HF2PLL provides 6 dual-phase demodulators. Each demodulator can be configured with its own filter properties. The advantages of digital versus analog instruments include higher dynamic reserve, zero drift, precise phase shifts, and orthogonality. Excellent Measurement and Configuration Tools Integrated tooling provides a comprehensive set of analysis features making use of external equipment, such as an oscilloscope, obsolete. The internal oscilloscope with memory for 2048 samples provides immediate signal- vs-time plots. A sweeper can function as frequency response analyzer providing high-resolution signal- vs-frequency plots, as well as sweeper over other internally controlled quantities like voltages or time constants. An FFT spectrum analyzer provides very high resolution signal analysis on frequency spans of up to 200 kHz. Finally the HF2PLL Advisor and the PID Advisor ensure efficient closed-loop parameter settings.

Application Pack

A selection of product options enable many additional modes of operation and measurement. In particular the HF2LI-MF and the HF2LI-MOD option provide the multi-harmonic mode (MHM), dual frequency resonance tracking (DFRT), frequency modulated Kelvin probe force microscopy (FM-KPFM) and Q-Control. It is easy to extend the application support at any time as both mentioned options can be upgraded in the field.

HF2PLL Specifications

PLL Operation Modes
constant excitation yes
constant amplitude yes, with automatic gain control
Q-control yes (option)
Kelvin probe feedback yes (option)
frequency range 1 Hz - 50 MHz
center frequency 1 µHz - 50 MHz
PLL bandwidth (1 MHz) 16 Hz - 50 kHz
PLL bandwidth (100 kHz) 16 Hz - 10 kHz
phase noise (100 kHz at 100 Hz distance) -100 dBc/Hz
HF Analog Input  
frequency range 0.8 µHz - 50 MHz
input voltage noise 5 nV/√Hz above 10 kHz
dynamic reserve 120 dB
A/D conversion 14 bit, 210 MSa/s
HF Analog Output  
frequency range DC - 50 MHz
output ranges ±10 mV, ±100 mV, ±1 V, ±10 V
signal adder ±10 V, DC to 50 MHz bandwidth
D/A conversion 16 bit, 210 MSa/s
Demodulator & Reference  
number of demodulators 6 dual-phase
output sample rate on USB: up to 460 kSa/s
on Auxiliary outputs: 1 MSa/s
filter time constant 1 µs - 500 s
filter bandwidth 80 µHz - 200 kHz
filter slope 6, 12, 18, 24, 30, 36, 42, 48 dB/Oct
reference frequency resolution 0.8 µHz
reference phase angle resolution 1.0 µ°
dimensions 45 x 35 x 10 cm (19" rack)
weight 6.2 kg
power supply 110-120 V, 220-240 V, 50/60 Hz
operating temperature +5 °C to +40 °C
PC operating systems 32-bit and 64-bit version of Windows XP, Windows 7, Linux

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