Shulou(Shulou.com)06/01 Report--

This article introduces how to use the VNA function of Rigol RSA real-time spectrum analyzer, the content is very detailed, interested friends can refer to, hope to be helpful to you.

If engineers want to test the S parameters of some microwave devices, they will give priority to network analyzers. There are many brands and types of vector networks that the author has come into contact with, mainly such as Keysight, Anritsu, renders, CLP 41 and some other emerging domestic brands. What I mainly share with you today is the instrument of vector network analysis mode realized by Rigol, a domestic instrument manufacturer, through the spectrum analyzer.

Usually, the spectrum analyzer realizes the function of the network analyzer through the built-in TG tracking source of the spectrum analyzer itself, and then connects the VSWR bridge to realize the function of the SNA, the title network analyzer. Rigol's RSA N series real-time spectrum realizes the single-port vector mode through the built-in directional coupler, which provides convenience for the testing of some single-port devices.

Rigol provides RSA5000 and RSA3000 two types of instruments with five standard VNA functions. RSA5000 and 3000 series real-time spectrum analyzer family, through the addition of options can be provided including: GPSA, RTSA, VSA (option), EMI (option), VNA mode is widely used in enterprise research and development, factory production, education and teaching and many other fields. Among them, the product series with N suffix is standard with VNA option mode.

Users can choose from the [Mode] menu of the entity button. Note: the front panel keystroke operation may be different in different working modes.

1. GPSA GPSA mode adopts two analysis methods of frequency sweep and FFT. GPSA can complete both frequency domain analysis and time domain (zero sweep width) analysis. Select the spectrum analyzer mode for frequency sweep measurement.

2. RTSA RTSA mode provides the function of real-time signal analysis, which can capture complex signals seamlessly. Select the spectrum analyzer mode for real-time measurement.

3. VSA VSA mode provides standard function of vector signal analysis and measurement.

4. EMI EMI mode provides EMI pre-compatible measurement function.

5. VNA VNA mode provides the function of vector network analysis, which can measure S11, S21 and DTF. In VNA mode, you can choose the measurement method through the Meas menu.

VNA mode can realize the measurement of components, S11, S21 and fault location of the circuit network, and characterize the network characteristics of the tested parts more accurately through Smith circle chart, polar coordinates and other displays. Enter the network division mode by pressing [Mode]-- > [VNA].

In VNA mode, the [TG] button light of the key panel is always red, indicating that the tracking source is open by default, and the [Gen Output 50 Ω] port connector of the front panel will output a signal of the same frequency as the current scan signal, and the power of the signal can be set through the menu.

Up to 4 traces can be displayed at the same time in VNA mode, each marked with a different color:

Footprint 1: yellow

Footprint 2: blue

Footprint 3: green

Footprint 4: purple

The format of each footprint can be changed with the [Trace] button.

1. Logarithmic amplitude Log Mag

The trace represents the logarithmic amplitude of the measurement, in dB.

two。 Phase

The trace represents the phase of the measurement result, and the display range is from-180 °to + 180 °in degrees (°).

The vector network analyzer is called "vector" because it can test the phase. More importantly, the vector correction can be calibrated, so the phase testing ability of the vector network analyzer is very important. After calibration, shake the cable to see if the phase jitter of S21 is too large, greater than 5 °@ 40GHz.

3. Group delay

The trace represents the signal transmission delay in DUT, in seconds.

4. Smith circle chart

The Smith chart format is used to display the impedance of the measured data based on DUT reflection. In this format, the location of the footprint is the same as the polar format. Smith chart format allows users to select any of the following data sets as the Marker display results:-linear / phase: linear amplitude and phase. Logarithmic / phase: logarithmic amplitude and phase. Real part / imaginary part: real part and imaginary part. -R + jX: impedance diagram. R: Resistance resistance; X: Reactance reactance. All units are omega. -G + jB: admittance diagram. G: Conductance conductance; B: Susceptance admittance. All units are S.

5. The distance from the polar trace to the polar origin represents the amplitude (linear) of the measurement result, the amplitude (linear) with the displacement from the origin, and the phase by the angle deviating from the positive X axis counterclockwise. Polar coordinate form allows the user to select any of the following data sets as the display result of the Marker:-linear / phase: linear amplitude and phase. Logarithmic / phase: logarithmic amplitude and phase. Real part / imaginary part: real part and imaginary part.

6. Linear amplitude

The trace represents the linear amplitude of the measurement.

7. Standing wave ratio

The trace represents the standing wave ratio, SWR= 1 represents the standing wave ratio, 1 −, where ρ represents the reflection coefficient, unit: none

8. Real part

The trace represents the real part of the measured complex parameters.

9. Imaginary part

The trace represents the imaginary part of the measured complex parameters.

10. Extended phase

The trace represents the phase of the measured result and can display phases above + 180 °and below-180 °in degrees (°).

11. Positive phase

The trace represents the phase of the measurement result, and the display range is from 0 °to + 360 °in degrees (°).

twelve。 The logarithmic amplitude (DTF) trace represents the logarithmic amplitude in time domain measured by DTF, in dB.

13. The linear amplitude (DTF) trace represents the time domain linear amplitude measured by DTF.

14. The echo loss (DTF) trace represents the echo loss measured by DTF, in dB.

The setting of S parameter can be modified by the [Meas] button. S11 is displayed as four windows by default when measuring, and the window layout function is available. The upper and lower windows are displayed by default when S21 is measured, and the window layout function is available. The upper and lower windows are displayed during DTF measurement, and the window layout function is disabled.

Calibration function

Open circuit, short circuit and load calibration are provided through the Calibration item under the [Meas Setup] menu. This calibration method can effectively eliminate the reflection tracking error, directivity error and source matching error of the testing device in the reflection measurement using this port.

At the same time, custom calibrators are supported in the calibration application, because each type of calibrator has its own calibration parameters.

Including open circuit, short circuit, load, through.

The parameters of the OPEN calibrator are:

C0PercentC1C2C3offset length or time (time = length / speed of light in the air)

The parameters of the SHORT calibrator are:

L0 and L1, L2, L3 + offset length or time

The parameters of the LOAD calibrator are: 50 or 75 ohm

For the definition of through, Rigol uses the unit of length, which is the same as the instrument of Anritsu. The instruments of Keysight and 41 are defined in time ps unit.

After the completion of the calibration, the state of the load, the Smith chart is the central origin, indicating that the 50 ohms impedance match, which is basically normal.

Caliber step

The aperture step size (Aperture Step width) k determines the group delay? What is the caliber used? VNA measures S parameters by discrete frequency, the frequency step is ∆, and the aperture step is defined as k = / ∆.

Group delay? The differential is calculated from the phase of the scattering coefficient 11 or 21, and is calculated by the factor − 1max 360 °weighted (take S21 as an example):

Among them? Indicates the caliber of the measurement. The measurement accuracy of group delay depends on the caliber used. Too much value will lose details, and too small will increase the impact of noise. At present, there is no unified rule for caliber selection, so we can only choose the appropriate caliber through experience.

DTF measurement

The upper window shows the relationship between transmission loss and distance, and the trace format can be selected as linear amplitude (DTF) and logarithmic amplitude (DTF).

The lower window shows the relationship between transmission loss and frequency. The trace format can choose three formats: linear amplitude, standing wave ratio and echo loss (DTF).

At present, the VNA mode of Rigol spectrum analyzer has some basic functions, but the overall function is still relatively simple. For example, waveguide calibration, microstrip calibration, unknown straight-through calibration and connector removal calibration are not available yet, and there is still a long way to go, but I believe all these functions will be available in the near future.

Summary of various calibration methods

About the Rigol RSA real-time spectrum analyzer VNA function how to share here, I hope the above content can be of some help to you, can learn more knowledge. If you think the article is good, you can share it for more people to see.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.