Measurement of Harmonic Distortion

• Overview

• Procedure

Other topics about Frequency Offset Measurement

Overview

Using the frequency-offset function and absolute measurement function in combination allows you to measure harmonic distortion of nonlinear devices such as mixers and amplifiers.

Procedure

1. Setting Frequency-Offset Function

The frequency-offset function allows you to make measurements while the frequencies are different at each test port. In this case, measurement is done by using the setting example for measurement frequency in the following figure. For the setting of frequency-offset sweep, see Setting Frequency-Offset.

• When you measure the 3rd harmonics over 8.5 GHz with options 2D5, 4D5, 2K5 and 4K5, it is recommended to suppress the carrier signal using filter etc before executing the measurement for accurate results.

2. Implementing Receiver Calibration

Receiver calibration is required for the absolute measurement. Receiver calibration of the port to be used for the measurement increases the accuracy in the absolute measurement.

For detailed information on receiver calibration, see Receiver Calibration.

3. Setting Absolute Measurement Parameters

The frequency-offset function has an added absolute measurement function.

Procedures for setting absolute measurement parameters

Follow the steps below to set the absolute measurement parameters.

1. Press Channel Next/Channel Prev keys and Trace Next/Trace prev keys to activate the trace for which you want to implement absolute measurement.

2. Press Meas key to display the Measurement Menu.

3. Click Absolute to select measurement parameters.
    

   Softkey	Function
   A (n)	Absolute measurement in Port 1, test receiver
   B (n)	Absolute measurement in Port 2, test receiver
   C (n)	Absolute measurement in Port 3, test receiver
   D (n)	Absolute measurement in Port 4, test receiver
   R1 (n)	Absolute measurement in Port 1, reference receiver
   R2 (n)	Absolute measurement in Port 2, reference receiver
   R3 (n)	Absolute measurement in Port 3, reference receiver
   R4 (n)	Absolute measurement in Port 4, reference receiver

n in the parentheses is the stimulus port number.

4. Harmonic Distortion Measurement

Harmonic distortion is a typical measurement parameter of nonlinear devices such as mixers and amplifiers. As shown in the following figure, the second and third distortions increase by square and cube values of the fundamental signal, respectively. Thus the distortion component increases as a function of the fundamental signal power, and the harmonic distortion can be measured as the proportion of the 2nd and 3rd harmonic power levels to the fundamental signal power level.

Connection of DUT

Connect the DUT as shown below.

Procedures for setting measurement parameters

Follow the steps below to set the measurement parameters. In this case, we measure the harmonic distortion magnitude by using the frequency-offset sweep and the absolute measurement function, based on the E5071C's internal signal source.

1. Receiver calibration is required before starting absolute measurement. For detailed information on receiver calibration, see Receiver Calibration.

2. Press Channel Next/Channel Prev keys and Trace Next/Trace prev keys to activate the trace for which you want to implement absolute measurement.

3. Press Meas key to display the Measurement Menu.

4. Press Absolute to select absolute measurement parameters (B (1)). Accordingly, the stimulus port and test port are set to 1 and 2, respectively.

5. In this case, the segment sweep function is used to perform faster measurement. For detailed information on segment sweep, see Performing a Segment-by-Segment Sweep (segment sweep).

6. Press Sweep Setup, then click Edit Segment Table to display the Edit Segment Table Menu.

7. Set Frequency Mode to Center/Span. Refer to the following table to input numbers in the segment table, and then press Return to return to the Sweep Setup Menu.
    

   Center	Span	Point
   500 MHz	0 Hz	1
   1 GHz	1 MHz	5
   2 GHz	1 MHz	5
   3 GHz	1 MHz	5
   3.5 GHz	0 Hz	1

7. Set Segment Display to Freq Base.

8. Press Sweep Type to select Segment.

9. Press Scale key to use Auto Scale All for trace scale optimization.
   
   
    

10. If you use the network analyzer as a tuning receiver like a spectrum analyzer, the setting must be the same at both the frequency point at which the harmonic is generated and the measurement point. Spectrum analyzers can detect all of the signals residing in the range of sweep frequencies, but network analyzers can only detect the signals residing in the measurement frequency point.

11. For additional information about the absolute measurements, see Keysight application note 1463-6 Accurate Mixer Measurements Using the Frequency-Offset Mode, 5989-1420EN (Internet Connection is required  to open).