HP 5988-7827EN free download

File name 5988-7827EN.pdf

Comparison of Mixer Characterization using New Vector Characterization Techniques White Paper Abstract This paper presents a novel method for characterizing RF mixers, yielding magnitude, phase, and group delay response of the conversion loss, as well as the input match and output match. This technique works for mixers which have reciprocal conversion loss and for which the image response can be filtered out. This technique is compared with a new vector corrected power technique, and with traditional power meter measurements. An error analysis on the new technique is presented for the first time. This paper was originally presented at the European Microwave Conference, September 24, 2002 [1]. Introduction Many wireless and RF systems require frequency converters or mixers with specified and well-controlled amplitude and group delay response. The amplitude response measurements of these devices have always had large uncertainties. Further, there have been few techniques that can characterize the phase or group delay response of mixers. A previous method described making group delay measurements by making three measurements on three pairs of mixers [2]. From these measurements, one can calculate the amplitude and phase response by solving the three linear equations for the overall response. This method makes use of up/down conversion but requires an IF filter between the pairs of mixers to avoid re-converting the unwanted side band. A second key aspect of the technique is that it assumes at least one of the mixers is reciprocal in its response, that is, it has the same conversion loss and group delay in the up-conversion mode as in the down-conversion mode. For some mixers, this holds approximately true. A difficulty with the previous method is that it requires three sets of meas- urements, with reconnections between the mixer pairs and the filter. With each connection, there is room for random error (connector repeatability) and systematic error, for example, mis-match effects between the filter and mixer pairs, and between the mixers and test equipment. Mixers typically have poor return loss, so these mis-matches can be quite severe. It has been suggested that adding padding (attenuation) between the mixers and filters can reduce this effect, but it introduces further sources of mismatch between attenuators and the filter, and it reduces the levels of signal measured creating a noisy measurement. 2 Overview of the new method One of the novel methods presented here can characterize the amplitude, phase, and delay response of a mixer, without the need to employ any other mixers. The input and output matches of the mixer are also determined. A second method can characterize the amplitude response of a mixer, correcting for input and output match through proper calibration steps of a vector network a