In a recent blog post, Marki Microwave demonstrated that, the MM1-2567 Mixer (their highest frequency mixer) actually operates even above 67 GHz, which is the value specified in the datasheet. This mixer was actually designed to operate up to a frequency of 80 GHz on the RF and LO sides, however their test equipment could only measure conversion losses up to 67 GHz. To test above this frequency, Marki Microwave set up an experiment to if this mixer could operate up to 80 GHz. Here is what they did:
First they generated a 50 GHz LO signal using their A-2050 amplifier - this was the highest frequency LO that they could provide. They used this to upconvert a 5-30 GHz input signal up to two sidebands: 45-20 GHz and 55-80 GHz. They then filtered out the LO feedthrough and the lower sideband using an FH-5500 High Pass Filter. Next they downconverted the resultant single sideband signal using a second MM1-2567 Mixer. The result is a high conversion loss, and an ugly signal:
This is because the result above includes two conversions, as well as the loss of the filter. If they divide this by two and make some assumptions about the loss of the filter (remember they can’t measure that directly above 67 GHz either), they get this:
The graph above shows that the mixer can operate up to 80 GHz. The conversion loss appears pretty high (close to 20 dB) at these frequencies, however the exact insertion loss of the mixer can no be determined at that frequency. The connectors in this set-up were all only rated to 67 GHz, and this is in a connectorized microstrip package that has its own losses. With all that, the performance of the chip doesn’t look too bad. The predicted CL is actually the measured loss of the MM1-2567LS from the datasheet, so it is there to confirm that their experimental method makes some sense. This is an innovative way to test performance of mixers at higher frequencies. Read the complete blog post about this on the Marki Microwave Website.
