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Design Notes

Amplifier Phase Noise

This project is a test bench that demonstrates how the amplifier device contributes to phase noise at its input.

Overview

The main schematic is the Amp_Test schematic.  The main user settings are center frequency (FC), center frequency power (FC_PWR), the IF filter bandwidth (BW), and the phase noise mask (Phase_Noise_Freq_Offset and Phase_Noise_Amplitude).  These are all variables on the schematic.

The test bench is configured such that the mixer is fully linear for any reasonable power level with a single tone at FC with a power level of FC_PWR (all other tones are at approximately -400 dBm).

The Phase Noise graph calculates the phase noise before and after the amplifier.  Note that the input phase noise matches the mask defined in the FREQUENCY and Phase Noise parameters in the OSC_W_PH_NOISE element.

The Phase Noise Amp Delta graph uses output equations to subtract the input phase noise amplitude from the output phase noise amplitude (i.e. the phase noise contribution from the amplifier).

The Spectrum graph confirms that the input signal is as clean as it can be and is at the desired FC and FC_PWR.gph:Spectrum