IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 53, NO. 5, SEPTEMBER 2004 1441 Wide-Band RF Receiver Using the “Five-Port” Technology Guillaume Neveux, Bernard Huyart, Member, IEEE, and Georges. J. Rodriguez-Guisantes Abstract—Many experiments have been proposed in order to demonstrate that the “five-port” system performs a homodyne de- modulation [1]–[3]. The large bandwith of a five-port circuit [4] is its main advantage. However, this kind of system must be cal- ibrated for each frequency in order to carry out the inphase and quadrature demodulation. The subject of this paper is to show a new calibration method. This technique uses the training sequence received at each received burst of data to calibrate the five-port system. A method to synchronize the receiver with the training se- quence of each burst is presented. We also study the effect of adja- cent channels and cochannel interferer on the calibration. Results on quaternary phase-shift keying demodulation are presented. Index Terms—Adjacent channel rejection, calibration, direct conversion receiver, five-port technology. I. INTRODUCTION I NITIALLY, the six-port technology was applied for metrology purposes because it is a very accurate method to measure complex ratios of two electromagnetic waves [5]. Many papers present network analyzers with six-port tech- nology [6]. Over the last ten years, many new applications using this technology have been proposed, such as direct conversion in a receiver [7], phase and frequency discrimination in a radar system [8], and direction finding of multiple radio-frequency (RF) signals [9]. Following the initial work of Li [7], many papers dealing with direct digital receiver based on six- or five-port technology have been published [10]–[12]. The prin- cipal advantage of the five-port is the extremely large frequency bandwith of this RF circuit. Hesselbart [4] proves that reflection coefficient measurement of loads using a six-port reflectometer is operating over three decades in the frequency band of 2–2200 MHz. Another advantage of the five-port homodyne system is similar to that of the zero-intermediate frequency (IF) mixer based receiver, i.e., one local oscillator and no image-rejection filter. The purpose of an RF receiver is to demodulate a signal with carrier frequency , complex envelope env , and the amplitude using a signal generated by a local oscillator with frequency Manuscript received October 18, 2003; revised March 7, 2004. This work was supported by the COMELEC Department, Ecole Nationale Supérieure des Télécommnunications, Paris, France, under Laboratoire Traitement et Commu- nication de l’Information (LTCI) UMR5141 Centre National de la Recherche Scientifique (CNRS). The authors are with the Ecole Nationale Supérieure des Telecommuni- cations, COMELEC Department, Laboratoire Traitement et Communication de l’Information (LTCI) Unité Mixte de Recherche UMR 5141, Centre National de la Recherche Scientifique (CNRS), Paris 75013, France (e-mail: neveux@enst.fr; huyart@enst.fr; rodriguez@enst.fr). Digital Object Identifier 10.1109/TVT.2004.832392 Fig. 1. Classical homodyne receiver. and amplitude . The two signals can be represented by the two complex waves (1) (2) The voltages and are obtained by taking the real part of (1) and (2) (3) (4) and represent the inphase and quadrature (I/Q) sig- nals. Fig. 1 represents the classical homodyne receiver using quadrature down conversion, which performs the demodulation of . However, the baseband signals and at the output of this architecture can be corrupted by direct current (dc) offset, inphase and quadrature (I/Q) mismatch, local oscillator (LO) leakage, and even-order distorsion [13]. The three baseband terms produced by the five-port system have similar problems, but we will show that they can be reduced by using the ho- modyne receiver with a five-port circuit and the appropriate calibration method. This paper is organized into six sections. The principle of operation of five-port system is presented in Section II. A method of calibration is detailed in Section III. The effects of an adjacent channel are studied in Section IV and a method of self-calibration to reject this interference is presented in Section V. This self-calibration method uses the training sequence received in each burst of data that corre- sponds to a known I/Q sequence to self calibrate the five-port system. In this way, the adaptive calibration coefficients can effectively reject the spurious terms and distorsions. Results on quaternary phase-shift keying (QPSK) demodulation at 2 GHz with data rate of 200 kb/s are presented in Section VI. Finally, we will show that a multimode and multiband direct digital receiver is obtained using the five-port circuit together with the self-calibration. 0018-9545/04$20.00 © 2004 IEEE