Vector Network Analyzers

What is a Vector Network Analyzer?

A vector network analyzer (VNA) is a high-precision measurement instrument used in the RF/microwave field. Simply put, it measures the signal transmission and reflection characteristics in high-frequency circuits. Its core function is to transmit a signal to the device under test and accurately measure the amplitude and phase changes of the reflected and transmitted signals.

By measuring this vector data, which includes phase information, the VNA can comprehensively characterize device performance, such as filter bandwidth, amplifier gain, and antenna matching. It acts like an "X-ray machine" in the electronics world, revealing the frequency characteristics of a circuit. The VNA vector generates a swept frequency signal using an internal signal source. A directional coupler separates the incident, reflected, and transmitted signals. A quadrature demodulator then detects the signal vector information. The data is ultimately converted into S-parameters and displayed in formats such as Smith charts and frequency curves.

The VNA is an indispensable tool in modern electronic engineering, particularly crucial for the design and optimization of high-frequency systems such as 5G, radar, and aerospace.

How Does a Vector Network Analyzer Work?

The VNA's operating principle is based on transmitting a known signal and comparing it to the received signal. Its internal signal source generates a clean, frequency-swept RF sine wave signal. This signal is split into two paths via a directional coupler: one serving as a reference signal and the other as a test signal, which are then applied to the device under test.

The VNA's highly sensitive receiver then simultaneously measures the signal reflected from the device under test and the signal transmitted through it. By precisely comparing these two signals in amplitude and phase with the original reference signal, the VNA calculates S-parameters (such as return loss S11 and insertion loss S21) that reveal the device's essential characteristics, thereby fully characterizing the device's frequency response.

What are the main advantages of a vector network analyzer?

The vector analyzer network provides comprehensive measurements, eliminating critical information. While conventional instruments can only measure signal strength, a vector network analyzer can also measure signal deviation. Just like buying clothes, one should consider not only the size (amplitude) but also the fit (phase), allowing for a more accurate assessment of the quality of the equipment.

The VNA analyzer provides exceptionally accurate measurements, capturing even the slightest differences. Whether the signal is extremely weak or strong, it accurately captures it with minimal error. It's like using a precision scale to measure even the weight of a hair, making it ideal for rigorous equipment quality inspections.

The VNA network analyzer offers a wide range of functions, allowing one device to be used in conjunction with multiple others: It not only measures basic data but also detects line breakpoints, analyzes signal noise, and more. It's like buying a single device that combines the functions of a scale, ruler, and magnifying glass, eliminating the need for additional equipment, saving both time and money.