saulbit
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Now I am dealing with a mixer and it is cascaded with a MMIC amplifier, Gali-5+,from the mini-circuits, to amplify the IF signals. The LO frequency is 2855MHz, +13dBm,while the RF input is 985MHz.-28dBm; When I tested after the mixer, the result is as follows ( all refers to dBm ):
985MHz：-55.93；1.97GHz：-106.4；
885MHz：-99.12；4825MHz：-102.1；
2855MHz：-30.92；5.71GHz：-27.35；8565MHz：-30.82；11.42G：-53.42；
1.87GHz：-34.82；3.84GHz：-35.12.
They were RF input and its harmonic, the third order distortion, the LO remains and its harmonics, the IF frequency ( upper and downside).
However, when I tested after the amplifier, the results came:
985MHz：-39.97；1.97GHz：-74.32；
885MHz：-83.13；4825MHz：-92.7；
2855MHz：-17.99；5.71G：-22.21；8565MHz：-39.71；11.42G：-64.41；
1.87GHz：-19.92；3.84GHz：-24.85.
As we can see, the amplifier works normally from 885MHz to 4825MHz with a gain varying from 14dB to 10dB. Everything is OK, except that 1.97GHz got a gain of about 32dB. That is amazing. I couldn't imagine a small MMIC amplifier have a gain of 30dB. So I made another experiment, in which I chose the 1.97GHz as an individual input for the amplifier, then to my disappointment, the gain is just 15dB as normal. I have added a 3dB π attenuator for a good match in the input stage of the amplifier.
So would anyone have met such problems or would bring me some suggestions?
I doubt that the 985MHz LO remains causes some harmonic for 1970MHz after the amplifying and this harmonic plays a dominant role, comparing the 1970MHz's liner amplifying results .
Any reply is welcome.
985MHz：-55.93；1.97GHz：-106.4；
885MHz：-99.12；4825MHz：-102.1；
2855MHz：-30.92；5.71GHz：-27.35；8565MHz：-30.82；11.42G：-53.42；
1.87GHz：-34.82；3.84GHz：-35.12.
They were RF input and its harmonic, the third order distortion, the LO remains and its harmonics, the IF frequency ( upper and downside).
However, when I tested after the amplifier, the results came:
985MHz：-39.97；1.97GHz：-74.32；
885MHz：-83.13；4825MHz：-92.7；
2855MHz：-17.99；5.71G：-22.21；8565MHz：-39.71；11.42G：-64.41；
1.87GHz：-19.92；3.84GHz：-24.85.
As we can see, the amplifier works normally from 885MHz to 4825MHz with a gain varying from 14dB to 10dB. Everything is OK, except that 1.97GHz got a gain of about 32dB. That is amazing. I couldn't imagine a small MMIC amplifier have a gain of 30dB. So I made another experiment, in which I chose the 1.97GHz as an individual input for the amplifier, then to my disappointment, the gain is just 15dB as normal. I have added a 3dB π attenuator for a good match in the input stage of the amplifier.
So would anyone have met such problems or would bring me some suggestions?
I doubt that the 985MHz LO remains causes some harmonic for 1970MHz after the amplifying and this harmonic plays a dominant role, comparing the 1970MHz's liner amplifying results .
Any reply is welcome.