Wideband Medium Power Amplifier unexpected losses
Hi,
I am building wideband medium power amplifier that will cover 500 MHz -20 GHz+ bandwidth. Linearity is not our priority, just gain and output power. I will be driving this amplifier with CW sine wave or synthesized signal directly from PLL.
My topology utilizes following components:
- AVA-223MP+ ( first stage - preamp) https://www.minicircuits.com/pdfs/AVA-223MP+.pdf
- ADPA9007 (second - output stage) https://www.analog.com/media/en/technical-documentation/data-sheets/adpa9007.pdf
- DC blocking caps ATC 531Z- https://rfs.kyocera-avx.com/userFiles/uploads/pdfs/531z.pdf
- Bias tee - BCR-162 for first stage and BCR-531 for output stage
- RF connectors - Wurth 60312862112552 - https://www.we-online.com/components/products/datasheet/60312862112552.pdf
- attenuator between stages - KAT-0+ https://www.minicircuits.com/pdfs/KAT-0+.pdf
Topology:
RF connector -> DC block -> AVA-223MP+ -> Bias Tee -> DC block -> KAT-0+ attenuator -> DC block -> ADPA9007 -> Bias Tee -> DC block -> Bias Tee ( we need to apply DC offset to the modulator driven by the amplifier) -> RF connector
I am using Rogers 4003C and 0.203 mm thickness.
S21 measurement and simulaiton
I measured S21 using VNA up to 8.5 GHz, however I obtained lower gain than I expected from the simulation. Furthermore this gain degrades with increasing frequency. Looks like overall shape is correct but gain is lower and it decreases with frequency.
Measured S11 stays below -10 dB in range 100MHz- 8.5 GHz
Things I have checked so far:
- amplifiers operating point - both amplifiers have correct Uds and Id
- Stability - I turned on amplifier with no signal and checked spectrum analyzer on full span, no suspicious signals
I am looking for help since I have none to ask and I'm pretty left with AI which does not pinpoint any reasonable explanations. How to pinpoint the problem?
Any suggestions highly appreciated. I have some RF equipment and I can perform more measurements if needed.
Edit:
Uploading S11 and S22 and layout
