RF Electronics Chapter 5: Frequency Mixers Page 128
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
The RF signal appearing at the IF port is -30.847 dBm. Since the RF signal is -5 dBm,
the RF to IF is isolation is 25.847 dB. This can only be improved by using a higher order
diplexer as part of the mixer, or by using another mixer configuration like the double
balanced mixer.
Figure 5.28 shows the IF voltage for the balanced mixer and it can be seen that the
waveforms are much more like a pure sine wave than the corresponding waveforms for
the single diode mixer. With the second order filters used in the diplexer, there are still
some RF signals present at the IF output but they are small enough not to cause any
problems. As expected from equations 5.11 and 5.12, the balanced diodes mixer has no
DC signal at the IF port, in contrast to the single diode mixer.
Figure 5.28. IF voltage for a balanced diode mixer as a down-converter.
Figure 5.29. RF spectrum of a balanced diode mixer as an up-converter.
RF Electronics: Design and Simulation
128 www.cadence.com/go/awr
