Agilent Technologies ESA-E Series, User Manual

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24 Chapter 3
Making Measurements
Making Return Loss Measurements
5. Make the measurement.
a. Reconnect the device to be measured to the signal separation device.
b. Read the measurement and save it if required.
Example
The following example measures the return loss of a bandpass filter (BPF).
1. Adjust the spectrum analyzer control settings.
With the BPF in the measurement path, adjust the spectrum analyzer control
settings for the correct frequency coverage, resolution bandwidth, input
attenuation and source power.
Having adjusted the control settings, do not alter them during the course of the
measurement.
To obtain a faster sweep, change the coupling from normal spectrum analyzer
mode to stimulus response mode by pressing the
Sweep front panel key and
Swp Coupling SR SA
menu key until
SR
is underlined.
2. Establish a 0 dB reference trace for normalizing the measured data.
Normalization removes any frequency-response errors introduced by the
components of the test setup before making the measurement. It is performed
by removing the device to be tested and measuring a short or open. As neither
can dissipate the energy of the incident signal—100% reflection takes place,
and the wave is reflected back from the short or open—to the spectrum
analyzer where its value is displayed:
a. Remove the BPF and connect a short in its place as shown in the figure.
b. Press the View/Trace front panel key.
c. Press the More menu key.
d. Press the Normalize menu key, Store Ref (1 - 3) and normalize On.
This procedure establishes a 0 dB reference trace which is stored in the ESA
spectrum analyzer. It is then used to normalize the measured data automatically
by subtracting the short circuit calibration from the measurement obtained with
the device.