In designing of wide-band RF power amplifier, if the input and output return loss (S11 & S22) are -5dB over the whole bandwidth ( 2GHz to 4GHz). Is it acceptable? and how much will affect the output power?and what is the ideal value of input and output return loss of designing wide-band power amplifier?
5dB seems pretty high. From a return loss chart, that's a 3.5:1 mismatch with 1/3 of the input power being reflected. Back in my RF days, 12dB was what we went with but that was at 900 MHz.
-5dB for especially S11 is low, ti should be at least -10dB.
S22 can be around because load will probably different than 50 Ohm, so complex conjugate matching is not expected.
-5dB for especially S11 is low, ti should be at least -10dB.
S22 can be around because load will probably different than 50 Ohm, so complex conjugate matching is not expected.
Wideband matching is really difficult.There are few approximation about it and series connected Low Pass/High Pass forms or PI or T forms are frequently used.So, every section maintains a degree of matching at adjacent frequencies/bands and at the final the whole circuit brings the desired matching over a band.But this technique is pretty lossy and space consuming.
Real Frequency Technique is another option but it needs a bit computer support.I heard there are some Matlab routines but I don't know how they work.