RF Electronics Chapter 5: Frequency Mixers Page 145
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
Figure 5.54. Conversion loss of the transmission line balanced mixer.
Figure 5.55. IF Spectrum of the transmission line balanced mixer as a down-converter.
Changing the transformer to a transmission line will thus not change the performance of
the mixer very much apart from a reduction of the bandwidth, since the transmission line
only produces a 180 phase shift at a single frequency. However, in many microwave
applications the resulting bandwidth is sufficient. The mixer can also be used as an up-
converter.
Branchline Coupler Balanced Mixer
A transmission line, used to produce the 180 phase shift in figure 5.53 produces a linear
phase shift with frequency. As shown in figure 4.39, the Branchline coupler has less than
2 variation of phase from a 90 phase shift between ports 2 and 3 over a 20% bandwidth.
RF Electronics: Design and Simulation
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