Impact of RFIC Spurious Noise on Receiver of Cellular Handset in Communication State

This paper describes a spurious noise measurement arising from radio frequency integrated circuit (RFIC) and an analysis of its impact on receiver of a 4G cellular mobile handset. In mobile radio systems, there are two types of unwanted signals that degrade the receiver sensitivity: phase noise and spurious clock noise arising from an RFIC. The former noise is observed by band power measurement. However, the latter one is not easily observed by the same way because it is a tone signal with varying phase noise. To detect the spurious clock noise, measurement system with combination of an active probe, inter-stage filter with high attenuation (80 dB) and spectrum analyzer with low floor noise (-155 dBm/Hz) is proposed. As a result, the spurious clock noise in a mobile handset in communication state (LTE-Band I) was observed as intended. The measured spurious noise exceeded phase noise about 10dB. To maintain sufficient receiver sensitivity, and high isolation duplexer more than 65 dB is therefore required.