The thermal noise and phase noise effect on
attenuation measurement is studied. For frequencies higher than 1 GHz, the receiver
employs a lock-in amplifier with a coherent frequency reference to minimize the phase
noise effect and achieve very wide dynamic range of attenuation measurement. The equivalent
noise floor at the receiver mixer output port is found to be around 172 dBm. The
dynamic range of the receiver is 181–175 dB from 50 MHz to 26.5 GHz. Measurement
results of a 0–170 dB synthesized step attenuator at 26 GHz is given to verify the performance
of the proposed receiver.