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

In this paper, an even harmonic-type direct conversion receiver using an ev en harmonic quadrature mixer is proposed in order to suppress the degradati on of sensitivity due to second-order intermodulation distortion and noise in the local oscillator. Based on the requirements for the RF characteristi cs of the digital mobile communication receiver, the required performance o f the noise figure and third-order intermodulation distortion of the even h armonic-type direct conversion receiver are presented. In order to satisfy these required characteristics at the same time, the improvement of the noi se figure is investigated by increasing the load resistance of the even har monic mixer. It is made clear that the voltage gain of the even harmonic mi xer is increased by making the load resistance higher so that the noise fig ure is reduced; thus, the noise figure of an even harmonic-type direct conv ersion receiver can be improved. A developed L-band EH-DCR for Japanese PHS achieves received sensitivity of -101 dBm and intermodulation characterist ic of 49 dB. (C) 1999 Scripta Technica.