Mixer linearisation for software defined radio applications

The inherent non-linearity of mixers is particularly acute in broadband receiver design for software defined radio (SDR) applications. Here, the receiver frontend 'sees' not only the wanted channel, but also a number of nearby signals. A conventional mixer will downconvert all of these received channels to IF, thus adding inband interband interference to the wanted channel. In this paper, known mixer linearisation schemes are explained and a new technique using frequency retranslation within a linearised mixer architecture is presented. Two-tone-test results from a prototype offered 33 dB reduction in the distortion products and 22 dB suppression of adjacent channel interference (ACI) for a /spl pi//4-DQPSK modulated carrier. A theoretical analysis is also carried out to demonstrate the amplitude and phase matching requirements of the technique.

[1]  I. D. Robertson,et al.  Linearised microwave mixer using simplified feedforward technique , 1999 .

[2]  Joseph Mitola,et al.  The software radio architecture , 1995, IEEE Commun. Mag..

[3]  Mark A. Beach,et al.  Software defined radio receiver test-bed , 2001, IEEE 54th Vehicular Technology Conference. VTC Fall 2001. Proceedings (Cat. No.01CH37211).

[4]  T.J. Ellis A modified feed-forward technique for mixer linearization , 1998, 1998 IEEE MTT-S International Microwave Symposium Digest (Cat. No.98CH36192).

[5]  Mark A Beach,et al.  Miniature distributed filters for software re-configurable radio applications , 2002 .

[6]  Pb Kenington,et al.  The Effect of Delay Mismatch on a Feedforward Amplifier , 1994 .

[7]  J. M. Pereira Beyond software radio, towards re-configurability across the whole system and across networks , 1999, Gateway to 21st Century Communications Village. VTC 1999-Fall. IEEE VTS 50th Vehicular Technology Conference (Cat. No.99CH36324).

[8]  Mark A Beach,et al.  Filter considerations in the design of a software-defined radio , 2001 .

[9]  Nick Pothecary,et al.  Feedforward Linear Power Amplifiers , 1999 .

[10]  P. B. Kenington,et al.  The Specification of Error Amplifiers for use in Feedforward Transmitters , 1992 .