The triple-balanced mixer topology further improves upon the linearity of double-balanced designs, but also requires yet higher LO power level for operation. The triple-balanced mixer uses eight diodes and several baluns, and is sometimes called “doubly double balanced” because it consists of two double balanced mixers in push-pull configuration.

A block diagram for a triple balanced mixer is shown in Figure 8 and a more detailed schematic is shown in Figure 9. Two hybrids are required for both the RF and LO ports, as well as a single hybrid coupler for the IF port:

Figure 8: Block diagram of a triple balanced diode mixer.

Figure 9: Detailed schematic of a triple balanced diode mixer.

This architecture provides better isolation and suppression of spurious and intermodulation products than the double balanced mixer topology. Triple balanced mixers also have a wide IF bandwidth. Triple-balanced mixers are ideal for applications where wideband signals need to be translated from one frequency range to another with minimal intermodulation products.

Advantages and Disadvantages of the Triple Balanced Mixer Topology

Advantages

• Best linearity

• Ideal for wide band applications

• Ideal for RF/IF overlap situations

Disadvantages

• Requires the most LO power