This is the power compression test for IQ mixer 0255M and IF amplifer for both one tone and comb signal.


Power compression or P1dB is important parameter for components like mixer and amplifer. When devices are running close to its compression point, its output going to see unusual intermodulation, harmonic and other spurs (IMD/IP3) etc.

In the IF system design, we have been very careful about the P1dB for mixer and ampliers and try to keep away from it as far as we can. For all the amplifer we plan to use, we have very clear data and plot for its power compression.

However for the mixer:IQ 0255M from Marki, after a phone call with Marki, we found out that they didn’t study the performance of IQ mixer with different input power (they just have input 1dB compression label for IQ0255L is 4 dBm, for IQ0255M is 6 dBm). For the IF design right now, the max input power for IQ0255 is -2.8 dBm: 8.8 dB away from 1dB compression of IQ0255M(We think it should be ok). So we need some test to make it very sure.

In this page, we tested the IQ0255 (connectorized pkg)power compression performance in lab. This test also include both comb signal(126 tones) and one tone case. From the test results, we also get the power compression results for the IF amplifer we are using right now in lab.


Test A: Test IQ0255M used as down converter for one tone

Method of test A: Directly use two synthesizers for LO and R port of mixer, and measure the power level at I/Q output use spectrum analyzer. 3 difference baseband (I/Q) frequency were used: 10MHz, 100MHz and 200MHz. LO frequency is fixed 3.22GHz with LO power level 15 dBm.

Results of test A: IQ_0255M_Measured_compression.pdf

Test B and C: Test IQ0255L used as down converter for comb signal (126 tones)

Method of test B and C: Use ROACH to generate comb signal (126 tones, with average power -19.2 dBm for each tone), up converted with IQ0255M, signal then go through IF system (for test B: only go through digital attenuator; for test C: go through digital attenuaotr + IF amplifer), then down converted by IQ0255L. LO frequency is fixed 3.22GHz; Baseband output freuqency(I/Q of down converter mixer) is set to be 32 MHz. LO power is 15 dBm for IQ0255M; 12 dBm for IQ0255L.

Setup of test B: ROACH_DAC + IQ_up + digital attenuator + (monitor_point_A)+IQ_down+(monitor_point_B) monitor point A: is the R port of IQ_down; monitor point B: is the I or Q port of IQ_down.

Results of test B: IQ_0255M_Measured_compression_comb_without_amplifier.pdf

Setup of test C: ROACH_DAC + IQ_up + digital attenuator + IF amplifier + (monitor_point_A)+IQ_down+(monitor_point_B)

Results of test B for mixer: IQ_0255M_Measured_compression_comb_with_amplifier.pdf
Results of test B for IF amp: IF_amp_compression_test_1.pdf , IF_amp_compression_test_2.pdf

Original data for test A, B and C : Data_Compression_Test_for_one_tone.pdf , Data_Compression_test_for_comb_signal.pdf
•    Compression_Test_for_one_tone.xlsx , Compression_test_for_comb_signal.xlsx

Summary of Results

One thing don't understand: for the one tone test, why the power roll off in both high power and low power. and we don't see this in the 126 tone test.

1. Input P1dB for IQ mixer is 6dBm for IQ0255M and +4dBm for IQ0255L.
2. This P1dB is good for both one tone and 126 tones cases(use summed power).
3. For the max power we planed to use in the IF system, we are running at the linear region of the IQ mixer. That means the current design of IF board should work fine.
4. To Be Added later on