Hello, cadence community,
I've stumbled upon a problem with power amplifier EVM evaluation - EVM is out of adequate bounds. At first I thought that the PA is faulty, but then I decided to create a simple DUT circuit - a resistor. This way the magnitude will decrease while the phase should stay the same.
I've attached the schematic and the EVM output plot.
Everthing is done strictly using MMSIM PA tutorial in IC615 (SpectreRF Workshop Power Amplifier Design Using SpectreRF MMSIM 12.1).
The standart of interest is 802.11a (but the calculations are wrong with 802.11n as well). The PWL files for I and Q channels were generated using 802.11a_signal_generator following the guide in the above mentioned document. The carrier frequency is 5GHz, rolloff factor is 0.23, bandwidth is 1.2288MH... - every setting in the spectre state is the same as in the tutorial.
So the question would be - is this a known bug with EVM estimation or is there something wrong with my configuration? Has anyone done successfull EVM measurements and if so - please share your knowledge. There is one suspicion that the 802.11a_signal_generator creates a faulty signal but I don't know how to check it. I've tried to use the cdma PWL files in Cadence rfLib, but get the same results (EVM value is not the same as in the picture above bus is inadequate).