page_title: Distributed-element circuit
section_title: Cascaded lines
hierarchical_section_title: Distributed-element circuit / Circuit components / Cascaded lines
caption_attribution_description: Deutsch: Orthomode Transducer als Hohlleiterabschnitt
context_page_description: Distributed-element circuits are electrical circuits composed of lengths of transmission lines or other distributed components. These circuits perform the same functions as conventional circuits composed of passive components, such as capacitors, inductors, and transformers. They are used mostly at microwave frequencies, where conventional components are difficult to implement.
  Conventional circuits consist of individual components manufactured separately then connected together with a conducting medium. Distributed-element circuits are built by forming the medium itself into specific patterns. A major advantage of distributed-element circuits is that they can be produced cheaply as a printed circuit board for consumer products, such as satellite television. They are also made in coaxial and waveguide formats for applications such as radar, satellite communication, and microwave links.
  A phenomenon commonly used in distributed-element circuits is that a length of transmission line can be made to behave as a resonator. Distributed-element components which do this include stubs, coupled lines, and cascaded lines.
context_section_description: Cascaded lines are lengths of transmission line where the output of one line is connected to the input of the next. Multiple cascaded lines of different characteristic impedances can be used to construct a filter or a wide-band impedance matching network. This is called a stepped impedance structure. A single, cascaded line one-quarter wavelength long forms a quarter-wave impedance transformer. This has the useful property of transforming any impedance network into its dual; in this role, it is called an impedance inverter. This structure can be used in filters to implement a lumped-element prototype in ladder topology as a distributed-element circuit. The quarter-wave transformers are alternated with a distributed-element resonator to achieve this. However, this is now a dated design; more compact inverters, such as the impedance step, are used instead. An impedance step is the discontinuity formed at the junction of two cascaded transmission lines with different characteristic impedances.
caption: An orthomode transducer (a variety of duplexer) with stepped impedance matching
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