A report on Transmission line and Distributed-element filter

Schematic of a wave moving rightward down a lossless two-wire transmission line. Black dots represent electrons, and the arrows show the electric field.

Figure 2. A parallel-coupled lines filter in microstrip construction

One of the most common types of transmission line, coaxial cable.

Variations on the schematic electronic symbol for a transmission line.

A microstrip low pass filter implemented with bowtie stubs inside a 20 GHz Agilent N9344C spectrum analyser

Figure 5. Stepped-impedance low-pass filter formed from alternate high and low impedance sections of line

A transmission line is drawn as two black wires. At a distance x into the line, there is current I(x) travelling through each wire, and there is a voltage difference V(x) between the wires. If the current and voltage come from a single wave (with no reflection), then V(x) / I(x) = Z0, where Z0 is the characteristic impedance of the line.

Figure 6. Another form of stepped-impedance low-pass filter incorporating shunt resonators

Standing waves on a transmission line with an open-circuit load (top), and a short-circuit load (bottom). Black dots represent electrons, and the arrows show the electric field.

Figure 8. Capacitive gap stripline filter

A type of transmission line called a cage line, used for high power, low frequency applications. It functions similarly to a large coaxial cable. This example is the antenna feed line for a longwave radio transmitter in Poland, which operates at a frequency of 225 kHz and a power of 1200 kW.

Figure 9. Stripline parallel-coupled lines filter. This filter is commonly printed at an angle as shown to minimize the board space taken up, although this is not an essential feature of the design. It is also common for the end element or the overlapping halves of the two end elements to be a narrower width for matching purposes (not shown in this diagram, see Figure 1).

A simple example of stepped transmission line consisting of three segments.

A microstrip hairpin filter followed by a low pass stub filter on a PCB in a 20GHz Agilent N9344C spectrum analyser

A microstrip hairpin PCB filter implemented in an Agilent N9344C spectrum analyser

Figure 11. Stripline interdigital filter

Three Interdigital Coupled Line filters from a spectrum analyser PCB

Figure 12. Stripline stub filter composed of λ/4 short-circuit stubs

The distributed-element model applies at all frequencies, and is used in transmission-line theory; many distributed-element components are made of short lengths of transmission line.

- Distributed-element filter

RF engineers commonly use short pieces of transmission line, usually in the form of printed planar transmission lines, arranged in certain patterns to build circuits such as filters.

- Transmission line

4 related topics with Alpha

Planar transmission line

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An RF power amplifier incorporating planar circuit structures. The amplifier on the left feeds its output into a set of planar transmission line filters in the centre. The third circuit block on the right is a circulator to protect the amplifier from accidental reflections of the power back from the antenna

Field patterns for selected modes: A, quasi-TEM in microstrip, B, quasi-TEM in CPW (even mode), C, slotline mode in CPW (odd mode)

Stripline variants: A, standard, B, suspended, C, bilateral suspended, D, two conductor

Microstrip variants: A, standard, B, suspended, C, inverted, D, in box, E, trapped inverted

CPW variants: A, standard, B, CBCPW, C, coplanar strips, D, embedded coplanar strips

Slotline variants: A, standard, B, antipodal, C, bilateral

Finline variants: A, standard (unilateral), B, bilateral, C, antipodal, D, strongly coupled antipodal E, insulated

Imageline variants: A, standard, B, insular, C, trapped; other dielectric lines: D, ribline, E, strip dielectric guide, F, inverted strip dielectric guide

Transitions: A, microstrip to SIW, B, CPW to SIW, C, microstrip to CPW, the dotted line marks the boundary of the microstrip groundplane, D, CPW to slotline

Planar transmission lines are transmission lines with conductors, or in some cases dielectric (insulating) strips, that are flat, ribbon-shaped lines.

The method is often used for filters.

Microstrip

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Microstrip is a type of electrical transmission line which can be fabricated with any technology where a conductor is separated from a ground plane by a dielectric layer known as the substrate.

Microwave components such as antennas, couplers, filters, power dividers etc. can be formed from microstrip, with the entire device existing as the pattern of metallization on the substrate.

PCB of a DVD player. Typically, PCBs are green, but they may also be made in other colors.

Printed circuit board

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Laminated sandwich structure of conductive and insulating layers.

Part of a 1984 Sinclair ZX Spectrum computer board, a PCB, showing the conductive traces, vias (the through-hole paths to the other surface), and some electronic components mounted using through-hole mounting.

Surface mount components, including resistors, transistors and an integrated circuit

A PCB in a computer mouse: the component side (left) and the printed side (right)

A board designed in 1967; the sweeping curves in the traces are evidence of freehand design using adhesive tape

The two processing methods used to produce a double-sided PWB with plated-through holes

Cut through a SDRAM-module, a multi-layer PCB. Note the via, visible as a bright copper-colored band running between the top and bottom layers of the board.

Cordwood construction was used in proximity fuzes.

Proximity fuze Mark 53 production line 1944

An example of hand-drawn etched traces on a PCB

A PCB as a design on a computer (left) and realized as a board assembly populated with components (right). The board is double sided, with through-hole plating, green solder resist and a white legend. Both surface mount and through-hole components have been used.

A breakout board can allow interconnection between two incompatible connectors.

This breakout board allows an SD card's pins to be accessed easily while still allowing the card to be hot-swapped.

A breakout board allows a module (a Bluetooth module in this case) to have larger pins.

For microwave circuits, transmission lines can be laid out in a planar form such as stripline or microstrip with carefully controlled dimensions to assure a consistent impedance.

In radio-frequency and fast switching circuits the inductance and capacitance of the printed circuit board conductors become significant circuit elements, usually undesired; conversely, they can be used as a deliberate part of the circuit design, as in distributed-element filters, antennae, and fuses, obviating the need for additional discrete components.