Terminology » Microwave VNA vs. Lock-in Amplifier: Understanding the Differences

Microwave VNA vs. Lock-in Amplifier: Understanding the Differences

Microwave VNAs (Vector Network Analyzers) and Lock-in Amplifiers are specialized test and measurement equipments used in RF and microwave engineering. They are specifically designed for desired applications.

Microwave VNA

It is a precision test equipment designed to measure reflection and transmission properties of devices across wide range of frequencies. It analyzes S parameters (S11, S22, S21, S12) to derive amplitude and phase information of signals during test. It helps to characterize microwave components such as amplifiers, filters, antennas, cables etc.

Key Features :

Performs S-parameter measurements
Amplitude and phase analysis of signals essential for complex impedance measurements
Widely used in design and testing of microwave and rf components.

Microwave Lock-in Amplifier

It is an equipment which extracts signals from extremely noisy environments using known reference signal. It is essentially a homodyne detector followed by low pass filter (LPF). Some Lock-in amplifier provides features to adjust cut-off frequency and filter order.

Key Features :

It isolates signal to be measured with the help of reference carrier signal after enhancing SNR.
Capable of detecting signals very smaller in amplitude compared to noise components, making it ideal for low level signal measurements.
Used in physics, optics and material science.

Comparison between VNA and Lock-in amplifier

Feature	Microwave VNA	Microwave Lock-in amplifier
Main Function	Measures S-parameters (reflection,transmission)	Extracts signals from noisy backgrounds using phase sensitive detection
Frequency Range	Broad, Khz to hundreds of Ghz	Narrow, centered around reference frequency
Phase measurement	Supported, provides both amplitude and phase information	Supported, via demodulation with reference signal
Noise handling	Moderate, designed for devices with higher signal levels	Excellent, can detect signals much weaker than noise
Signal type	Continuous wave and pulsed signals	Modulated signals with known reference frequency
Output	S-parameters	Demodulated amplitude and phase of the target signal
Use case (main focus)	Device characterization and network analysis	Signal extraction and measurement in high noise scenarios
Typical applications	Antenna design, filter testing, amplifier characterization	Low level signal detection in noisy environments such as quantum sensing

Summary

In summary, while both instruments operate in the microwave domain and provide phase information, a Microwave VNA is primarily used for characterizing the behavior of RF components by measuring how they transmit and reflect signals. In contrast, a Microwave Lock-in Amplifier excels at detecting and measuring weak signals buried in noise by using phase-sensitive detection techniques. The choice between the two depends on the specific requirements of the measurement task at hand.