J. Freed,

On Wednesday Nov 20th, the Double Mixer topology for SPI D2400315-x0 was taken, and it works how we intended as a way to gerenrate a 80MHz - 4096Hz signal it to but with alot of noise.

DMPrototype.png Is a diagram of the Double Mixer Design

DM_First_Test.png Is a diagram of the test done on the Double Mixer, this inital test was just to check that the Double Mixer produces the expected output signal frequency, as such, the amplifier was ignored. 

DM_FT_Result.png Shows the output on the scope.  Blue is the double mixer output. White is a reference of SRS SG382 (sync with 80 Mhz OCXO via 10 MHz Timing) with a frequency of 79,995,904 Hz and power of -0.91 dBm. The SRS signal, timed with the OCXO, and the double mixer correctly locks with eachother. This gives credance that this design will work for the goal of the double mixer; a 79,995,904 Hz signal frequency locked to a 80MHz OCXO. However there is a lot of noise in the double mixer signal. An ongoing investigation is currently underway to find and reduce this noise.

ZMSCQ_Wave_Shape.png Shows a possible source of the noise, the Double Mixer requires phase delayer for the Sin path, we used a MiniCircuts ZMSCQ-2-90B for this. I tested the ZMSCQ-2-90B by puggining the input of the signal and the signal from the 2 ports into osciloscope. I split off the input signal with a Minicircuts ZMSC-2-1BR+ (Summer/Splitter) and I had to normalize input power pickoff in postprocessing by a factor of 0.68 due to the power difference. The results show that the output of the ZMSCQ-2-90B has a sligtly different shape than what was plugged in. With the delay port (orange) having a slight "hump" on the rise. Will retake with a faster osciloscope, as the signal is very noisy.

The investigation is continuing with the next step of checking the double mixer output signal with a network anaylizer to check the frequencies around 79,995,904 Hz. A Phase noise measurement would also work with the caviot that the phase adjust to destructivly interfere the double mixer signal with the reference signal would have to be adjusted manually.