This topic started with a desired to see the difference between driving a DBM LO port with a sine vs a square wave. It is also an opportunity to get familiar with my test equipment.
Test Equipment
The signals will be generated by a two channel Siglent SDG 1032x signal generator. The mixing products will be observed on a Siglent SVA 1015x spectrum analyzer. The signal generator channels had the 50Ω output impedance selected to be compatible with the analyzer.
During initial testing, I noticed that since the timebase of the two instruments was not calibrated. When generating a 7 MHz sine wave, the analyzer displayed the test frequency about 40 Hz low. I connected the 10 MHz sync output of the analyzer to the signal generator and now the displayed values are around +/- 10 Hz. Was this step absolutely necessary – no. Did I have an extra BNC cable laying around and was curious – yes.
Test the Equipment
First step is to know your equipment. I set the signal generator to output a 7 MHz sine wave with an amplitude of -30 dBm. The set an analyzer marker on the input signal and verified the amplitude and frequency. The results below show the expected results and that the signal is pretty clean up to 50 MHz. For these experiments, this is all I care about.
Test Setup
Below is the schematic for the test.
