RF characteristics of an even harmonic-type direct conversion receiver for mobile communications

Abstract

In this paper, an even harmonic‐type direct conversion receiver using an even harmonic quadrature mixer is proposed in order to suppress the degradation of sensitivity due to second‐order intermodulation distortion and noise in the local oscillator. Based on the requirements for the RF characteristics of the digital mobile communication receiver, the required performance of the noise figure and third‐order intermodulation distortion of the even harmonic‐type direct conversion receiver are presented. In order to satisfy these required characteristics at the same time, the improvement of the noise figure is investigated by increasing the load resistance of the even harmonic mixer. It is made clear that the voltage gain of the even harmonic mixer is increased by making the load resistance higher so that the noise figure is reduced; thus, the noise figure of an even harmonic‐type direct conversion receiver can be improved. A developed L‐band EH‐DCR for Japanese PHS achieves received sensitivity of –101 dBm and intermodulation characteristic of 49 dB. © 1999 Scripta Technica, Electron Comm Jpn Pt 2, 82(3): 11–21, 1999