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Harmonic-balance simulators and electromagnetic analysis tools are becoming essential to RP mixer design. New balun structures for RFICs are key to matching impedances at high GHz-frequencies. This AWR scientist offers some pointers on mixer-design using contemporary modeling tools.*
The use of modern harmonic-balance simulators and electromagnetic analysis software has been instrumental in the design of modern mixers. Especially, it has allowed the development of new types of balun structures, without which broadband monolithic balanced mixers would be impossible. Design techniques, however, must be adjusted to make most efficient use of these technologies. This paper describes the current state of the art in the design, analysis, and computer modeling of microwave and RF mixers-and offers some pointers improving designs.
We show how modern computer analysis (CAD) tools, especially general-purpose harmonic-balance simulators and planar electromagnetic simulators, have improved both the quality of mixer designs and the efficiency of the design process. Simultaneously, new approaches to the design of baluns and passive structures have resulted in high-performance, broadband designs. Thus results in a new level of sophistication for mixer technology.
Since the invention of the superheterodyne receiver by Edwin Armstrong in 1917, mixers have been essential parts of radio communication systems. Mixer design has traditionally been an approximate process, at best using special-purpose computer programs. The development of general-purpose harmonic-balance simulators and electromagnetic simulators, however, has improved the accuracy of the design process enormously, and it has even made the design of a wide variety of new balun structures possible. These have been particularly valuable in monolithic circuits.
Mixers can be broadly categorized as active or
passive. Passive mixers primarily use Schottkybarrier diodes, although a relatively new type of passive mixer, the FET resistive mixer[1], recently has become popular. FET resistive mixers use the resistive channel of a MESFET to provide low-distortion mixing, with approximately the same conversion loss as a diode mixer. Active mixers use either FET or bipolar devices. FETs (either MESFETs or HEMTs) are used for most microwave and RF applications where active mixers are employed; bipolar junction transistors (BJTs) and occasionally heterogeneous-junction bipolar transistors (HBTs) are used most frequently as Gilbert multipliers[2] for modulation, phase detection, and similar purposes. The theory of both active and passive mixers has been well known...