Lesson plan
Active circulator
In electrical engineering, an active circulator is an active non-reciprocal three-port device that couples a microwave or radio-frequency signal only to an adjacent port in the direction of circulation. Other (external) circuitry connects to the circulator ports via transmission lines. An ideal three-port active circulator has the following scattering matrix: : S = \begin{pmatrix} 0 & 0 & 1\\ 1 & 0 & 0 \\ 0 & 1 & 0 \end{pmatrix} An active circulator can be constructed using one of several different technologies. One early technology is the use of transistors as the active devices to perform the non-reciprocal function. Varactor circuits are another technology, relying on a time-varying transmission line structure, driven by a separate pump signal. A third technology utilizes spatiotemporally-modulated rings of coupled resonators. Another design approach relies on staggered commutation and integrated circuit techniques. Compared to passive (ferrite) circulators, active circulators have the advantages of small size, low mass, and simple integration with other circuitry. System designers must weigh these factors with the disadvantages of active circulators: they require DC power and sometimes a separate pump or clock signal, they can be nonlinear, and can introduce significant noise into the signal path.
Article summary
In electrical engineering, an active circulator is an active non-reciprocal three-port device that couples a microwave or radio-frequency signal only to an adjacent port in the direction of circulation. Other (external) circuitry connects to the circulator ports via transmission lines. An ideal three-port active circulator has the following scattering matrix: : S = \begin{pmatrix} 0 & 0 & 1\\ 1 & 0 & 0 \\ 0 & 1 & 0 \end{pmatrix} An active circulator can be constructed using one of several different technologies. One early technology is the use of transistors as the active devices to perform the non-reciprocal function. Varactor circuits are another technology, relying on a time-varying transmission line structure, driven by a separate pump signal. A third technology utilizes spatiotemporally-modulated rings of coupled resonators. Another design approach relies on staggered commutation and integrated circuit techniques. Compared to passive (ferrite) circulators, active circulators have the advantages of small size, low mass, and simple integration with other circuitry. System designers must weigh these factors with the disadvantages of active circulators: they require DC power and sometimes a separate pump or clock signal, they can be nonlinear, and can introduce significant noise into the signal path.
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
Bibliography
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Key claims and bibliography are generated from the same tracked claims and sources as the article page.