Tracking Generator Measurement Guide : E-Series Tracking Generator : Measurement Example
Measurement Example
This example demonstrates how to connect a Device Under Test (DUT) and make a measurement. This example will characterize the frequency response of a filter in the GSM frequency band.
1. Set the frequency range to cover the range of the DUT being tested. In this example, the center frequency is set to 1.8 GHz with a 1 GHz span.
2. Set the Generator to Tracking Mode with an Output Power of 0.0 dBm. Refer to the previous Tracking Generator Overview section for additional information.
3. Connect the DUT as shown in Figure: Connection of Device Under Test. For connector torque and connector care information, refer to the User Guide for your instrument.
4. Toggle the Generator Output to On.
Connection of Device Under Test
5. Observe the measurement to confirm that the pass band frequency range covers the required span.
6. If the spectrum analyzer noise floor is too high for the necessary measurements, then reduce the input attenuation and RBW to maximize the dynamic range. Figure: Increasing Measurement Dynamic Range, Trace Averaging On, Displaying Power Statistics shows the sample setup with the input attenuation lowered from 30 dB to 10 dB and with the RBW reduced from 3 MHz to 300 kHz.
7. When measuring a filter with a very high insertion loss in the stop band, press the Shift key, then the Trace (5) key. Press the Trace A Operations submenu key, then the Average  A submenu key to turn on averaging and clean up the stop band area. An averaging value of 10 will probably be adequate for most filters.
8. Under the Setting submenu turn Power Statistics On (Figure: Increasing Measurement Dynamic Range, Trace Averaging On, Displaying Power Statistics) to display the spectrum analyzer received Maximum, Average, and Minimum power of each frequency range sweep.
If the noise floor drops below the visible display, then set the Scale dB/division setting to a value larger than 10. This will increase the displayed amplitude range.
Increasing Measurement Dynamic Range, Trace Averaging On, Displaying Power Statistics
Many of displayed settings on the left side of the screen are used as menu shortcuts. Select a parameter by touching the appropriate setting on the touch screen to display the menu and set the parameter for editing.
Enhancing Accuracy
For detailed power level measurements, the output flatness of the tracking generator can be calibrated in the field.
1. After the frequency range and other settings are determined, disconnect the DUT and make a through connection between the GENERATOR/RF OUT connector and the ANALYZER/RF IN connector. For the most accurate results, use the same cables and adapters for this connection as were used to connect the DUT.
2. From the Generator > Setting submenu, press Enhanced Generator Power Accuracy.
3. Select the number of external Matching Pad (3 dB) pads to use for calibration and measurements. Press Enhanced Accuracy Calibration. External attenuators will need to be inserted for the 3 dB and 6 dB pad options.
Matching 3 dB external attenuators are not required. Attenuators do provide a more accurate 50 ohm match to the generator output and analyzer input. This may help in cases where transmission ripple needs to be minimized.
For the most accurate results, use the same 3 dB pad setup (0, 1, or 2 pads) in measurements as were used for calibration.
4. Follow the onscreen instructions shown in Figure: Enhanced Generator Accuracy.
During the Enhanced Accuracy Calibration process, the instrument calibrates across the frequency range, reducing any output ripple. After the successful completion, the (+Accy) label will be displayed after the Generator output power (Figure: After Enhanced Accuracy Calibration).
5. Figure: Before Enhanced Accuracy Calibration is a detail of the top of the filter trace shown in Figure: Increasing Measurement Dynamic Range, Trace Averaging On, Displaying Power Statistics before calibration. Figure: After Enhanced Accuracy Calibration shows the same trace section after enhanced calibration using two 3 dB pads.
The 7.5 dB loss from the 0 dBm generator power is from the two 3 dB pads, the filter, and cables connected between the Generator port and Spectrum Analyzer receiver.
The Enhanced Accuracy calibrations are eliminated at Preset, Power‑on, or when the generator output level is changed. The calibrations are not saved nor recalled with Save/Recall.
Enhanced Generator Accuracy
Before Enhanced Accuracy Calibration
After Enhanced Accuracy Calibration