RF Electronics Chapter 5: Frequency Mixers Page 138
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
The basic DBM1 and DBM2 with reflectionless filters have all ports terminated into
50 Ω. As a result, there is not much difference in performance like conversion loss and
IF spectral components below 100 MHz. Figure 5.44 shows the conversion loss of the
different mixer configurations. There is no discernible difference in conversion loss
between the basic DBM1, DBM2 with all ports terminated in a reflectionless filter or
DBM3 only the IF port terminated in a reflectionless filter. DBM4 of figure 5.43(L),
presents a high impedance at the centre point of the transformer and reduces the RF and
LO currents flowing into the IF port. Figure 5.44 shows that this increases the conversion
loss. DBM5 of figure 5.43(R), presents a low impedance at the centre point of the
transformer and increases the RF and LO currents flowing into the IF port. Figure 5.44
shows that this reduces the conversion loss.
Figure 5.44. Down-conversion loss of DBM configurations.
Figure 5.45. IF Spectra of different DBM configurations.
RF Electronics: Design and Simulation
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