Practical MMIC Design
Filled with real-world design techniques and rules of thumb, this practical resource offers professionals a unique look into the day-to-day practices of MMIC production and the economics associated with it.
TABLE OF CONTENTS Practical MMIC Design
5.10: Millimeter-Wave Circuits
5.10 Millimeter-Wave Circuits
Millimeter-wave circuits are so-called because they operate at frequencies where the free-space wavelength is less than one centimeter and best expressed in millimeters. This means they have frequencies of 30 to 300 GHz, and because the wavelength is reduced by a higher dielectric constant than free space, the wavelength on a GaAs microstrip is as short as ?3 mm. This has a number of consequences for MMIC design because of the higher frequency; for example, the choice of components changes, and simulation techniques become an issue. These areas are discussed in the following sections.
5.10.1 High-Frequency Effects
A number of MMIC design issues can be neglected at RF and microwave frequencies, but they start to become more important at frequencies higher than 30 GHz. This is not only because the frequency is higher and the wavelength is shorter but because the active devices become limited, and parasitics associated with the simulation models and chip-to-system interfaces become more important. In fact, the use of 3D EM analysis tools becomes essential for first-pass design success.
For example, at millimeter-wave frequencies, components like spiral inductors become resonant and no longer look inductive. Figure 5.149 shows that a circuit operating at 40 GHz is only able to use spiral inductors with 2.5 turns or fewer. Also, the thickness of the substrate may allow multiple modes to propagate along a microstrip transmission line, so CPW transmission lines may need to be used instead. Indeed, the transmission lines and other components become...
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