By Jim Pomager
At some point in the not-so-distant future, you’ll be able to recharge your smartphone by waving it about in the air for a few moments or (less conspicuously) by simply holding it out in a stiff breeze.What does this have to do with medical device design, you ask? Quite a lot, as it turns out.
A magnetron is a high-power microwave oscillator in which the potential energy of an electron cloud near the cathode is converted into RF energy in a series of cavity resonators. As depicted by the low frequency analog, the rear wall of the structure may be considered the inductive portion, and the vane tip region the capacitor portion of the equivalent resonant circuit. The resonant frequency of a microwave cavity is thereby determined by the physical dimension of the resonator together with the reactive effect of any perturbations to the inductive or capacitive portion of the equivalent circuit.
Differential devices offer advantages like noise immunity, low crosstalk, high integration density, and reduced power consumption. However, they also require special measurement capabilities. There are essentially two different measurement methods available: virtual measurements and true differential measurements. This white paper provides an overview of both the virtual and true differential measurement methods.
The latest mainstream pHEMT cascodes are fabricated in 0.25 micron pHEMT, where the 0.25 micron dimension refers to the gate width of the internal pHEMT transistors. These devices replace the previous generation 0.50 micron pHEMT cascodes, with the smaller gate width devices exhibiting higher gain and NF values that are roughly 0.25 dB lower than their predecessors at a given frequency. What follows is a brief discussion about some of the outstanding properties of these pHEMT cascode amplifiers, some potential applications that go beyond their traditional role as LNAs, and some comparisons with more traditional solutions for those applications.