Honored Contributor
Honored Contributorlet me try to explain what i can right out of my head, will have to ask the rf guys on monday for deeper informations.
the transmitter modulates f0 or f1 as a single sideband signal SSB, that could be the lower sideband LSB or the upper sideband USB the microwave analog receiver part delivers the ADC signals I and Q as I = RFinput x sin wt Q = RFinput x cos wt currently I feeds FIR1 (0,33 0,33 0,33) and Q FIR2 (-1,55 0 1,55) that is LSB and if I and Q are swap this is USB selection (or vice versa, i am not shure right now that doesn't matter for explanation) The outputs of FIR1 and FIR2 are added to form the value of IQ what is then processed as explained before with sin and cos of f0 and f1 The binary information is not within the phase of the received signal. the absolute amplitude is also not required we only need to know whether f0 or f1 is transmitted we need the SSB to gain the 3dB in RX as the transmitter is a passiv transmitter (Backscatter) we need to add I and Q to get the vector to prevent what we call microwave holes in RX path the complete receiver works very good. but the values we get if we receive in LSB mode and the ones we receive in USB mode are now as expected. LSB/USB is 3dB better than Dual side band DSB but we loose 10dB or more between correct and wrong side band than we should from theory this is due to a mismatch of one of these FIR filters that has good phase matching but f0 and f1 have different gain in amplitude. so i want to know if there is a clever way to add I and Q so that phase and amplitidue for f0 and f1 a matched. could i make it clear ?
