Distributed-element circuits are electrical circuits composed of lengths of transmission lines or other distributed components. Circuits built from these components include filters, power dividers, directional couplers, and circulators. They were studied during the 1920s and 1930s but did not become important until World War II.
About Distributed-element circuit in brief
Distributed-element circuits are electrical circuits composed of lengths of transmission lines or other distributed components. 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. They are used mostly at microwave frequencies, where conventional components are difficult to implement. A phenomenon commonly used in distributed-element. circuits is that a length of transmission line can be made to behave as a resonator. Circuits built from these components include filters, power dividers, directional couplers, and circulators. They were studied during the 1920s and 1930s but did not become important until World War II, when they were used in radar. After the war their use was limited to military, space, and broadcasting infrastructure, but improvements in materials science in the field soon led to broader applications. They can now be found in domestic products such as satellite dishes and mobile phones, and are the technology of choice at radio frequencies above 1 GHz. The overwhelming majority of distributed-Element circuits are composed of. lengths of transmitters and receivers. The cross-sectional dimensions of a transmission line are unvarying along its length. This means that only distribution along the length of the line need be considered. Such an element of a distributed circuit is entirely characterised by its length and characteristic impedance. Commensurate line circuits, where all the elements are the same length, are important because a general theory for producing them exists.
Although an arbitrary shape can be analysed with Maxwell’s equations to determine its behaviour, finding a useful shape is a matter of trial and guesswork. An important difference between. trial and error is that all complex forms of distributed circuit forms are an irrational function of complex frequency; all fixed-connected line lengths at fixed frequencies are a result of a complex transfer function. This is the result of the transfer function of lumped circuit forms being a rational function ofcomplex frequency; the equivalent of a fixed line filter at fixed frequency does the same thing at a fixed delay at a higher frequency. The difference between lumped. circuit designs and distributed circuit designs is that the distributed circuit response is periodically periodically repeated as shown in the Chebyshev example; the effect is similar to that of a phased circuit response of fixed frequency filters at fixed delay. The difference is significant for hand-held devices, because lumped-element designs generally result in a smaller product. Printed circuit boards using through-hole technology are larger than equivalent designs using surface-mount technology. Hybrid integrated circuits are smaller than PCB technologies, and monolithic integrated circuits is smaller than both. hybrid integrated circuits can use lumped designs at higher frequencies than printed circuits, and this is done in some radio frequency integrated circuits. Miniaturised circuits can using the lumped model at aHigher frequency. Distributed designs are feasible above 300 MHz, and can be used at microwavefrequency above 1GHz.