RF Electronics Chapter 5: Frequency Mixers Page 153
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
180 Hybrid Microwave DBM
A 180hybrid consisting of the Parallel Coaxial Balun of figure 4.55 or the Marchand
Balun of figure 4.58 can also be used to produce microwave double balanced mixers, as
shown in figure 5.68.
Figure 5.68. 180Hybrid DBM used for down-conversion.
Figure 5.69. Marchand Balun for use in figure 5.68.
The baluns need to be modified to enable the replace the ground with port 2 as shown in
figures 5.69 and 5.70. For the Balun at the LO port in figure 5.68, port 2 is grounded and
at the RF port, port 2 of the Balun is connected to the IF port. In figure 5.68 a low pass
filter is included at the IF port, to slightly reduce the conversion loss and remove most of
the RF and LO signals from the IF port. These baluns can be used as subcircuits for the
mixer of figure 5.68. A transformer balun, like the centre-tapped transformer, XFMRTAP
shown in figure 5.31 can also be used as subcircuits for the mixer of figure 5.68.
Figure 5.70. Parallel line Balun for use in figure 5.68.
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