R&D (FilterCavity)
YaoChinHuang - 22:23, Wednesday 30 October 2019 (1786)
Measure demodulator performance

[Yao-Chin, Yuhang]

Frequency from DDS with -6.5dBm sent to input LO & RF ports of demodulator (ZFMIQ-70D). The demodulator output I & Q ports connected low pass filter of DC-2.5MHz. We measured the Vpp and phase difference of I & Q ports from oscilloscope. 

Note: Unbalance Amplitude (dB)= 20* log (Vpp of I port/ Vpp of Q port)

(I) Fixed LO port frequency of 78 MHz

LO 
(MHz)
RF
(MHz)
Vpp of I
(mV)
Vpp of Q
(mV)
Unbalance Amplitude
(dB)
Phase Difference btw I&Q
(degree)
78
78.0001
286
254
1.03
90.4
78
78.001
284
254
0.97
90.8
78
78.01
282
250
1.05
90.2
78
78.05
255
222
1.20
90.5
78
78.1
210
182
1.82
91.7

 
(II) Fixed difference frequency of 100 Hz between LO and RF ports tune range from 66 to 80 MHz.

LO
(MHz)
RF
(MHz)
Vpp of I
(mV)
Vpp of Q
(mV)
Unbalance Amplitude
(dB)
Phase Difference btw I&Q
(degree)
66.0001
66
260
260
0
91.2
67.0001
67
262
260
0.07
90.1
68.0001
68
266
260
0.20
90.9
69.0001
69
266
260
0.20
90.6
70.0001
70
270
260
0.33
90.7
71.0001
71
272
260
0.39
90.9
72.0001
72
274
260
0.46
90.9
73.0001
73
276
259
0.55
90.6
74.0001
74
278
258
0.65
89.8
75.0001
75
281
258
0.74
90.2
76.0001
76
282
258
0.77
90.2
77.0001
77
282
255
0.87
90.6
78.0001
78
286
254
1.03
90.4
79.0001
79
286
254
1.03
90.1
80.0001
80
286
251
1.13
90.9

* Phase: Q=I+90o for LO>RF, Q=I-90o for LO<RF