RF Electronics Chapter 5: Frequency Mixers Page 151
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
Figure. 5.64, Measured spectrum of Branchline coupler balanced mixer of figure 5.63.
(Hor: Centre Frequency 1.5 GHz, 300 MHz/div. Vert: Max -10 dBm, 10 dB/div.)
It is possible to use a multi-loop Branchline hybrid, as shown in figures 4.35 to 4.39, for
the mixer. That extends the operating bandwidth of the mixer. M. Y. Algumaei [11] used
a triple loop Branchline hybrid to produce a mixer for RF inputs bandwidth of 3 GHz to
12 GHz.
Figure 5.65. Branchline coupler balanced mixer for up-conversion.
The mixer of figure 5.56 can also be used for up-conversion. However, since now the
inputs are LO and IF, the circuit of figure 5.56 will no longer result in the correct phase
angles for efficient mixing in the diodes. As a result, line TL12 in figure 5.65, needs to
be added to produce a 180 LO and a 0 IF phase difference across the diodes, to ensure
efficient mixing in the diodes. Figure 5.65 shows the resulting circuit schematic.
RF Electronics: Design and Simulation
151 www.cadence.com/go/awr
