Network Analyzer Maintenance--Network Analyzer Beginner's Guide

The network analyzer can characterize the linear and nonlinear characteristics (amplitude-frequency characteristics, phase-frequency characteristics, time-frequency characteristics, power-frequency characteristics, etc.) of the measured devices (mainly divided into active components and passive components).

So do you really understand network analyzers? Below, Xi'an Antai Maintenance Center uses the E50 series vector network analyzer of Keysight Technologies (formerly Agilent) as an example to introduce the instrument operation precautions, basic structure, common technical parameters, and basic operation steps.

1. Notes on instrument operation:

1. When testing the product, do not directly power on the device for testing.

2. Before testing the power amplifier, it must be checked on a spectrum analyzer to see if there is self-excitation before other indicators can be measured with a network analyzer.

3. Prevent large DC current from being added. The network analyzer can withstand a maximum DC current of 10V.

4. Prevent excessive signal input.

5. The maximum allowable input signal of the network analyzer is 20dBm.

6. When the input signal is greater than 10dBm, a corresponding attenuator should be added.

7. Make sure the instrument is grounded before use.

2. Basic structure of network analyzer

The network analyzer is mainly composed of a signal source, a signal separation device, a receiver and a processing and display unit.

1. Signal source: A synthetic signal source consisting of a 3-6 GHz YIG oscillator, a 3.8 GHz dielectric oscillator, a source module component, a clock reference and a decimal loop, which can provide a variety of signal outputs.

2. Test device: It is generally composed of a directional coupler and a switch. Its function is to separate the reflected signal and the incident signal, thereby performing initial signal separation and preprocessing.

3. Signal receiver: The signal pre-processed by the test device is processed again after being processed. Its function is to down-convert the signal and process the intermediate frequency digital signal for output or display comparison. The receiver is mainly composed of sampling/mixer, intermediate frequency processing and digital signal processing.

4. Display: Its function is to intuitively show the display output or signal comparison, etc. It is used for high-brightness, high-speed display of characters and graphics. It is mainly composed of a graphics processor, a high-brightness LCD display, an inverter and other parts.

3. Common technical performance parameters

1. Test port output frequency: range, resolution, accuracy, etc.;

2. Output characteristics: power range, resolution, level accuracy, level linearity, impedance, second harmonic, third harmonic, non-harmonic spurious signals (typical values), non-harmonic spurious signals related to the mixer, etc.;

3. Test port input characteristics: frequency range, average noise level, maximum input level, damage level, impedance, harmonics, second harmonics, third harmonics, harmonic measurement accuracy and dynamic range, etc.;

4. Group delay characteristics: range, aperture, group delay accuracy, etc.;

5. Structural characteristics: size, weight, etc.

Others should include understanding its directivity, coupling, insertion loss, maximum output, connectors, and other calibrated accessories and parts.

4. Basic Operation of Network Analyzer

1. Preparation

Prepare the network analyzer and DUT; clean, inspect, and measure all connectors; if using SOLT calibration, select a method for handling non-insertable connections; connect the analyzer's cables and adapters to the analyzer;

2. Calibration method

Select the appropriate calibration kit or define input calibration standards; set IF bandwidth and averaging to minimize noise during calibration; calibrate manually or use automatic calibration; verify calibration quality using a known check standard; save instrument state and calibration.

3. Operation steps

①First set the frequency: press the CENTER key (if the center frequency of the filter is set to 506M, just set it to 506M).

② When setting the bandwidth (display bandwidth): press the SPAN key, which is generally set to 100M.

③Press the CAL key again → CALIBRATE MENU (the third key) → RESPONSE (the second key) → THRU

④Press MARKER again to set the first mark point, and then press MARKER again to set the second point, and then push inward in sequence (generally set 5 mark points.

4. Execution method

Connect the DUT; obtain appropriate correction parameters from the calibration procedure; measure and save the DUT parameters.

5. Notes

Cable connectors, impedance converters, standing wave bridges, matching loads and other devices should strictly distinguish between the two characteristic impedances of 75Ω and 50Ω, because their outer diameters and connecting threads are the same and they are easy to confuse. Avoid connecting a 75Ω male plug with a 50Ω female plug, as this will cause the circuit to be discontinuous and unable to be tested; avoid connecting a 50Ω male plug with a 75Ω female plug, as this will completely damage the jack of the 75Ω female plug; impedance converters, matching loads, standing wave bridges and measuring probes should be placed with care and properly stored to prevent them from falling from a height and affecting their performance and final measurement results; when connecting each device, attention should be paid to the method of connecting and rotating, and only the movable nut is allowed to be rotated to ensure that the pin and the jack move in a straight line. Otherwise, the pin and the jack will undergo spiral motion and accelerate wear, and it is likely that the internal pin will be loosened and cannot be used normally; after the cable connector is installed, carefully check whether the pin is in the middle, and try to correct it if necessary to make it centered to avoid damaging the connector jack to be connected.