5.11 Broadband Impedance Matching

Chapter 5.11 Broadband Impedance Matching

Radio Frequency Integrated Circuit Design Second Edition Book
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Radio Frequency Integrated Circuit Design Second Edition Book

  • 122 Impedance MatchingA comparison of frequency response (Figure 5.28) clearly shows the bandwidth broadening effect of matching in two steps. To quantify the effect, the magnitude of the input impedance is shown in Figure  Broadband Impedance Matching In many cases it may be necessary to match a circuit over a band of frequencies, which cannot be considered narrow with respect to the center frequency. In this case, more than two matching elements are usually required. One technique for matching makes use of a bandpass ladder filter [6, 7] in which a matching network is constructed as shown in Figure 5.30. Using this technique, the device that is being matched is designed to have an input impedance where the real part is designed to be equal to the source impedance. While this may seem very restrictive, a technique for making devices have a desired resistive component will be studied in Chapter 7. In general, the device will still have a reactive component that will make its imped-ance frequency dependent. A ladder of series and parallel LC networks is added to the input port of the device so thatFigure 5.27  Circuit for two-step matching.Figure 5.26  Smith chart illustration of one-step versus two-step matching.