Microwave Lock-in Amplifier from Zurich Instruments : Benefits and Other Vendors

Microwave Lock-in Amplifier

A lock-in amplifier is a precision equipment designed to extract specific signal component from noisy background. It achieves this by utilizing a reference signal and a LPF (Low Pass Filter) in a process known as phase sensitive detection. The figure depicts the process of extracting signal signal. Let us understand how it works.

Image Courtesy : Zurich Instruments, Switzerland

• Step-1 : The input signal which includes both desired signal and noise is multiplied by reference signal of the same frequency. This multiplication yields two outputs, one at sum of inputs and another at difference between them. If both input and reference frequencies are same, the difference component provides DC signal while sum component is available at twice of original frequency.
• Step-2 : The resulting signal from step 1 is passed through a LPF (Low Pass Filter) which is designed to allow only low frequency components including DC. This filter blocks or attenuates high frequency components such as twice of original frequency. The passed DC component corresponds to original signal’s amplitude and phase relative to the reference.
• Step-3 : To determine both amplitude and phase accurately, lock-in amplifier often employ two parallel detection channels. This include in-phase (‘X’) and the other quadrature phase (‘Y’). By analyzing these two components, and using following equations, magnitude (R) and phase angle (θ) of input signal can be calculated.

Advantages of Lock-in amplifier

Following are some of the benefits of microwave lock-in amplifier.

1. Can detect signals that are up to million times smaller than surrounding noise levels. Ideally used for applications where signal clarity is desired.
2. It enhances measurement accuracy by measuring both the amplitude and phase of the desired signal.
3. Modern lock-in amplifiers offer improved dynamic range and frequency selectivity which allows precise measurements across broad spectrum.
4. Due to their ability to measure weak signals accurately, they are utilized in various fields such as materials science, spectroscopy, quantum computing etc.
5. Digital lock-in amplifiers use advanced DSP algorithms and provide features such as multiple demodulators and enhanced filtering capabilities.

Zurich Instruments SHFLI 8.5GHz Lock-in Amplifier (Application Note)

Following are the features of SHFLI.

• Frequency range : DC to 8.5 GHz
• Two independent lock-in units with signal generators
• Four independent demodulators per lock-in unit
• Applications : Sensors (MEMS, NEMS, SAW, quantum sensing), optical PLLs, nano-optomechanics, RF-reflectometry
• Offers GUI
• supports programming languages such as Labview, C, Python, .NET, MATLAB

Other vendors

Each of these vendors offers unique features tailored to specific applications in microwave and RF signal analysis. The choice among them depends on factors such as required frequency range, sensitivity and integration capabilities with existing systems.