Testing ERA-5 MMIC for use as a multiplier

An easy way to generate harmonics is to drive an amplifier into compression. MMIC amps are easy to use and the 1 DB compression point is listed in the datasheet for just about all MMIC amplifiers available today. Normally this would be an undesired operating point. If you need a multiplier this a simple way to do it. Output are typically higher using an MMIC as a multiplier than using a simple diode multiplier. The output circuit of the MMIC can be designed to enhance the desired harmonic. That was not done in this test.

ERA-5 gain below 1GHZ = 20 DB
1 DB compression = +17.5 DBm

Input 738 MHz into MMIC at +6 DBm and +2 DBm drives the amp well into compression. No attempt was made to optimize the output for a particular harmonic or to suppress the fundamental. The output capacitor was 12 pf to favor the upper frequencies. Results varied depending on the input frequency. The data below is for 738 MHz. At 571 MHz the 5th harmonic with +2 DBm input was -20 but had a lot of “grass” around the carrier. Lowering the input to +1 DBm dropped the harmonic to -30 DBm and cleaned up the noise (or it dropped below the noise floor of the spectrum analyzer).

It appears the input should not exceed 5 DB above the 1 DB compression level or excessive noise will result.

+6 DBm input is 8.5 DB above the 1DB compression point
+2 DBm input is 4.5 DB above the 1DB compression point

Output 1 is with a +6 DBm input
Output 2 is with a +2 DBm input

Frequency(MHz) or Harmonic/Output1/Output2
738/+20/+18
X2/-2/-6
X3/+3/-12
X4/-4/-30
X5/-20/-30
X6/-42/-34
X7/-38/-46
X8/-30/-42
X9/-40/-50
X10/(below noise)/(below noise)