Circuit designers must often select a circuit technology, such as microstrip or grounded coplanar waveguide (GCPW) circuitry, with a particular design and circuit material to achieve optimum performance. Circuit technologies, such as microstrip and GCPW, each have their strengths and weaknesses, and it may help to take a closer look at these two circuit technologies in particular to see how they stack up.
Circuit performance may start with the choice of printed-circuit-board (PCB) material, but achieving a desired level of circuit performance can also have a great deal to do with how circuits are fabricated on a chosen PCB material.
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High-frequency circuit designers must often consider the performance limits, physical dimensions, and even the power levels of a particular design when deciding upon an optimum printed-circuit-board (PCB) material for that design. But the choice of transmission-line technology, such as microstrip or grounded coplanar waveguide (GCPW) circuitry, can also influence the final performance expected from a design. Many designers may be familiar with the stark differences between high-frequency microstrip and stripline circuitry.
Power amplifier design at RF/microwave frequencies can be aided by a wise choice of active devices, such as discrete transistors or monolithic microwave integrated circuits (MMICs). But don’t overlook the importance of the printed-circuit-board (PCB) material when planning for a solid-state power amplifier (PA) circuit. The circuit material can help or hurt a PA design, and knowing what is important in a PCB material intended for a PA is the first step in selecting a circuit material that enhances the PA’s performance.
Phase noise has long been a key parameter in high-frequency components, such as oscillators and frequency synthesizers, and high-frequency systems, such as radar and communications receivers. The choice of PCB material can contribute a great deal to the ultimate single-sideband (SSB) phase-noise performance possible from a circuit design. Understanding the key PCB material parameters that relate to phase noise can help when specifying a circuit laminate for the “quietest” phase noise possible for a given frequency.
Circuit design engineers have long relied upon the basic physics of printed-circuit boards (PCBs) and how capacitors and inductors can be formed from simple patterns and structures on a PCB. A number of PCB material traits, in particular the consistency of the dielectric constant, can go a long way towards achieving consistent and reliable PCB capacitors and inductors especially at RF and microwave frequencies.
Digital circuits continue to conquer higher speeds, with components such as microprocessors and signal converters routinely performing billions of operations per second. True, high-speed digital circuits can be flawed by such things as impedance discontinuities in transmission lines and poor plated-through-hole (PTH) interconnections between layers on multilayer circuit boards. But they can also be hurt by less-than-ideal choices of printed-circuit-board (PCB) materials for those high-speed-digital circuits. Which leads to the question: “What are the key parameters to consider when selecting a PCB material for a high-speed-digital circuit application?”
Ferromagnetic materials come in many forms and can serve RF/microwave applications in many ways. These materials are often recruited for high-frequency circuits for their resonant qualities as building blocks for such components as filters and oscillators. These materials are typically used with printed-circuit-board (PCB) materials to add inductance and resonance and enable the fabrication of resonant circuits at specific frequencies.
High-frequency circuit designers have a number of different circuit types from which to provide solutions from radio frequency (RF) through millimeter-wave frequencies and coplanar waveguide (CPW) might be an approach to consider as an option to popular microstrip techniques. Traditional CPW circuitry consists of a conductor separated by a pair of ground planes, on the same plane on top of a dielectric material. A variation on that circuit approach is grounded coplanar waveguide (GCPW), also known as conductor-backed coplanar waveguide (CBCPW). It adds a ground plane to the bottom of the basic CPW circuit structure, with plated through holes (PTHs) connecting the top and bottom ground planes.