Hi Gurus,
Can anyone explain a little bit about the receiver response to a CW input in the non-ratio measurement?
For example if we apply a -60 dBm 1.8 GHz CW at the port 2, and use receiver B to do the non ratio power measurement. It will give us two tones at the display. One is at 1.8 GHz and other is at the somewhere lower frequency end with offset (2nd LO+2nd IF+41.66...kHz).
From the block diagram, there is a a filter in front of the ADC. If we do the peak power reading of the two displayed tones, it power level is almost the same. When it seems there is no effect on the image tone from the 2nd mixer?
Thanks in advance!
Sincerely yours,
lzw
Can anyone explain a little bit about the receiver response to a CW input in the non-ratio measurement?
For example if we apply a -60 dBm 1.8 GHz CW at the port 2, and use receiver B to do the non ratio power measurement. It will give us two tones at the display. One is at 1.8 GHz and other is at the somewhere lower frequency end with offset (2nd LO+2nd IF+41.66...kHz).
From the block diagram, there is a a filter in front of the ADC. If we do the peak power reading of the two displayed tones, it power level is almost the same. When it seems there is no effect on the image tone from the 2nd mixer?
Thanks in advance!
Sincerely yours,
lzw
I'm assuming that you have the PNA source turned off. If so, then there are a number of tones that you might see for a CW input from an external source. The external source will have harmonics, sidebands, and subharmonics. The PNA receiver will also have subharmonics at (1.8 GHz - (N-1)*IF)/N and the respective images at (1.8 GHz - (N+1)*IF)/N, where N is the positive integer subharmonic. Odd subharmonics are dominant. You usually won't see these because they will be outside the IF bandwidth of the points you measure. If you use an IF bandwidth greater than the point spacing, you will see them for sure. At frequencies below 50 MHz, the IF jumps around quite a bit, so the above equations usually won't work.
For high power levels that put the receiver into compression, you will also see tones at M *1.8 GHz, where M is an integer.
Of course, you shouldn't see any of this if you use the internal source and sweep it with the measurement.