Agilent Technologies 8753ET User Manual

2-26
Making Mixer Measurements
Fixed IF Mixer Measurements
Fixed IF Mixer Measurements
A fixed IF can be produced by using both a swept RF and LO that are offset by a certain frequency. With
proper filtering, only this offset frequency will be present at the IF port of the mixer.
This measurement requires two external RF sources as stimuli. Figure 2-22 shows the hardware
configuration for the fixed IF conversion loss measurement. This example measurement procedure uses the
analyzer's test sequence function for automatically controlling the two external synthesizers (with SCPI
commands), and making a conversion loss measurement in tuned receiver mode. The test sequence
function is an instrument automation feature internal to the analyzer. For more information on the test
sequence function, refer to
"Using Test Sequencing to Test a Device" on page 1-115.
Tuned Receiver Mode
The analyzer's tuned receiver mode allows you to tune its receiver to an arbitrary frequency and measure
signal power. This is only possible if the signal you wish to analyze is at an exact known frequency.
Therefore, the RF and LO sources must be synthesized and synchronized with the analyzer's time base.
Since the analyzer is not phaselocking in this configuration, you can use it to measure conversion loss of a
microwave mixer with an RF frequency range output.
Tuned receiver mode also increases dynamic range. Broadband techniques like diode detection have a high
noise floor, while narrow band techniques like tuned receivers are much less susceptible to noise.
Sequence 1 Setup
The following sequence initializes and calibrates the network analyzer. It then initializes the two external
sources prior to measurement. This sequence includes:
• putting the network analyzer into tuned receiver mode
• setting up a frequency list sweep of 26 points
• performing a response calibration
• prompting the user to connect a mixer to the test set up
• initializing a loop counter value to 26
• addressing and configuring the two sources
• calling the next measurement sequence
1. Make the following connections as shown in Figure 2-21. Set the GPIB address of the external RF source
to 19 and the external LO source to 21.
2. Confirm that the external sources are configured to receive commands in the SCPI programming
language and that their output power is switched on.
NOTE You may have to consult the user's guide of the external source being used to determine
how to set the source to receive SCPI commands.
3. Be sure to connect the 10 MHz reference signals of the external sources to the EXT REF connector on

Agilent Technologies 8753ET Specifications

General

Brand	Agilent Technologies
Model	8753ET
Category	Measuring Instruments
Language	English