RF Electronics Chapter 5: Frequency Mixers Page 141
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
The TBM requires 8 diodes, and extra baluns results in additional costs for the mixer.
With the 8 diodes, additional LO power is required to achieve the same currents in the
diodes. The transformers used can be achieved as floating coaxial line baluns of figure
4.70 and using LTTC technology [5] as shown in figures 5.98 and 11.11.
As indicated in figure 5.6, mixer performance can be improved by putting two diodes in
series to produce a high-level double balanced mixer (HL-DBM), as shown in figure 5.49.
The HL-DBM circuit has 8 diodes identical to those used in the simulation for the DBM
and the TBM. When operating that at a 10 dBm LO and performing the same simulations
as for the TBM, results in a near identical performance for the HL-DBM to the TBM
shown in figure 5.50 to 5.52.
Figure 5.49. Circuit diagram of a high-level double balanced mixer as an up-converter.
Figure 5.50. Conversion loss of a TBM and DBM.
Figure 5.50 shows a comparison of the down conversion loss of a HBM, TBM and a HL
DBM. The DBM has a lower conversion loss. The TBM and HL DBM have the same
conversion loss and an actual mixer will have a slightly worse conversion loss than
simulated. For example a Mini Circuits ADE-201FMH+ covering the same RF/LO
frequencies as the mixers in this section, has a typical 6.4 dB conversion loss at an LO
level of 13 dBm. That is 1 dB worse than the results shown in figure 5.50.
RF Electronics: Design and Simulation
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