Which Harmonic Mixer Should I Use for My Spectrum Analyzer?

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SAGE Millimeter offers harmonic mixers in two product families: SFH and STH. Their purpose is to extend the operation frequency of the spectrum analyzer and/or the frequency counter to millimeter-wave operations. These cover seven waveguide bands spanning across the frequency range of 26.5 to 170 GHz.

SFH SAGE Millimeter
Figure 1. SFH Series Mixer

The SFH series mixers are based on a balanced structure to offer low conversion loss and continuous frequency coverage up to full waveguide band operations. Unlike waveguide harmonic mixers (STH series), these mixers possess an internally integrated frequency diplexer so that the RF, LO, and IF ports are configured separately. This feature allows for a convenient connection when they are used with spectrum analyzer models that do not have built-in diplexers; for example, the models offered by Keysight (Agilent) Technologies. In the meantime, these mixers are intended to be used as the higher order mixers, its local oscillator frequency range is limited to 3.0 to 6.1 GHz.

STH-12SF-S1, Web
Figure 2. STH Series Mixer

On the other hand, the STH series harmonic mixers are single ended mixers, they do not have the built-in frequency diplexer. Therefore, their LO and IF ports are combined into a single coaxial port, so the LO and IF signals are shared. This feature provides a convenient connection when they are used with spectrum analyzers or frequency counters that have a built-in diplexer, such as some spectrum analyzer models offered by Advantest, Anritsu, Rohde & Schwarz, and Tektronix, and the frequency counters by Phase Matrix (EIP, now National Instruments). In addition, these mixers are intended to accept higher local oscillator frequency in the range of 10 to 16 GHz so that the lower order harmonic is used. Because of this feature, the STH harmonic mixers may have higher sensitive or lower conversion loss.

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