A report on Transmission line and Microstrip

Schematic of a wave moving rightward down a lossless two-wire transmission line. Black dots represent electrons, and the arrows show the electric field.
Cross-section of microstrip geometry. Conductor (A) is separated from ground plane (D) by dielectric substrate (C). Upper dielectric (B) is typically air.
One of the most common types of transmission line, coaxial cable.
Variations on the schematic electronic symbol for a transmission 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.
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.
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.
A simple example of stepped transmission line consisting of three segments.

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.

- Microstrip

Types of transmission line include parallel line (ladder line, twisted pair), coaxial cable, and planar transmission lines such as stripline and microstrip.

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

6 related topics with Alpha

Overall
Printed circuit planar transmission lines used to create filters in a 20 GHz spectrum analyser. The structure on the left is called a hairpin filter and is an example of a band-pass filter. The structure on the right is a stub filter and is a low-pass filter. The perforated regions above and below are not transmission lines, but electromagnetic shielding for the circuit.

Planar transmission line

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Printed circuit planar transmission lines used to create filters in a 20 GHz spectrum analyser. The structure on the left is called a hairpin filter and is an example of a band-pass filter. The structure on the right is a stub filter and is a low-pass filter. The perforated regions above and below are not transmission lines, but electromagnetic shielding for the circuit.
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
Suspended stripline
Stripline variants: A, standard, B, suspended, C, bilateral suspended, D, two conductor
Microstrip
Microstrip inverted-F antenna
Microstrip variants: A, standard, B, suspended, C, inverted, D, in box, E, trapped inverted
Coplanar waveguide
CPW variants: A, standard, B, CBCPW, C, coplanar strips, D, embedded coplanar strips
Slotline
Slotline variants: A, standard, B, antipodal, C, bilateral
Substrate-integrated waveguide
Finline
Finline variants: A, standard (unilateral), B, bilateral, C, antipodal, D, strongly coupled antipodal E, insulated
Imageline
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 circuits

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

It is known as stripline, and is one of the four main types in modern use, along with microstrip, suspended stripline, and coplanar waveguide.

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.

Laminated sandwich structure of conductive and insulating layers.

PCB of a DVD player. Typically, PCBs are green, but they may also be made in other colors.
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.
Through-hole (leaded) resistors
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.
Eyelets (hollow)
PCB with test connection pads
A cordwood module
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.

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

Distributed-element filter

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Electronic filter in which capacitance, inductance, and resistance are not localised in discrete capacitors, inductors, and resistors as they are in conventional filters.

Electronic filter in which capacitance, inductance, and resistance are not localised in discrete capacitors, inductors, and resistors as they are in conventional filters.

Figure 2. A parallel-coupled lines filter in microstrip construction
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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
Figure 6. Another form of stepped-impedance low-pass filter incorporating shunt resonators
Figure 8. Capacitive gap stripline filter
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 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 10. Stripline hairpin filter
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
Figure 13. Konishi's 60° butterfly stub

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.

The structures shown can also be implemented using microstrip or buried stripline techniques (with suitable adjustments to dimensions) and can be adapted to coaxial cables, twin leads and waveguides, although some structures are more suitable for some implementations than others.

A telecommunications tower with a variety of dish antennas for microwave relay links on Frazier Peak, Ventura County, California. The apertures of the dishes are covered by plastic sheets (radomes) to keep out moisture.

Microwave

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Form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively.

Form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively.

A telecommunications tower with a variety of dish antennas for microwave relay links on Frazier Peak, Ventura County, California. The apertures of the dishes are covered by plastic sheets (radomes) to keep out moisture.
The atmospheric attenuation of microwaves and far infrared radiation in dry air with a precipitable water vapor level of 0.001 mm. The downward spikes in the graph correspond to frequencies at which microwaves are absorbed more strongly. This graph includes a range of frequencies from 0 to 1 THz; the microwaves are the subset in the range between 0.3 and 300 gigahertz.
Waveguide is used to carry microwaves. Example of waveguides and a diplexer in an air traffic control radar
Disassembled radar speed gun. The grey assembly attached to the end of the copper-colored horn antenna is the Gunn diode which generates the microwaves.
A satellite dish on a residence, which receives satellite television over a Ku band 12–14 GHz microwave beam from a direct broadcast communications satellite in a geostationary orbit 35,700 kilometres (22,000 miles) above the Earth
The parabolic antenna (lower curved surface) of an ASR-9 airport surveillance radar which radiates a narrow vertical fan-shaped beam of 2.7–2.9 GHz (S band) microwaves to locate aircraft in the airspace surrounding an airport.
Small microwave oven on a kitchen counter
Microwaves are widely used for heating in industrial processes. A microwave tunnel oven for softening plastic rods prior to extrusion.
Absorption wavemeter for measuring in the Ku band.
1.2 GHz microwave spark transmitter (left) and coherer receiver (right) used by Guglielmo Marconi during his 1895 experiments had a range of 6.5 km
ku band microstrip circuit used in satellite television dish.
Heinrich Hertz's 450 MHz spark transmitter, 1888, consisting of 23 cm dipole and spark gap at focus of parabolic reflector
Jagadish Chandra Bose in 1894 was the first person to produce millimeter waves; his spark oscillator (in box, right) generated 60 GHz (5 mm) waves using 3 mm metal ball resonators.
Microwave spectroscopy experiment by John Ambrose Fleming in 1897 showing refraction of 1.4 GHz microwaves by paraffin prism, duplicating earlier experiments by Bose and Righi.
Augusto Righi's 12 GHz spark oscillator and receiver, 1895
Antennas of 1931 experimental 1.7 GHz microwave relay link across the English Channel.
Experimental 700 MHz transmitter 1932 at Westinghouse labs transmits voice over a mile.
Southworth (at left) demonstrating waveguide at IRE meeting in 1938, showing 1.5 GHz microwaves passing through the 7.5 m flexible metal hose registering on a diode detector.
The first modern horn antenna in 1938 with inventor Wilmer L. Barrow
thumb|Randall and Boot's prototype cavity magnetron tube at the University of Birmingham, 1940. In use the tube was installed between the poles of an electromagnet
First commercial klystron tube, by General Electric, 1940, sectioned to show internal construction
British Mk. VIII, the first microwave air intercept radar, in nose of British fighter. Microwave radar, powered by the new magnetron tube, significantly shortened World War II.
Mobile US Army microwave relay station 1945 demonstrating relay systems using frequencies from 100 MHz to 4.9 GHz which could transmit up to 8 phone calls on a beam.

At microwave frequencies, the transmission lines which are used to carry lower frequency radio waves to and from antennas, such as coaxial cable and parallel wire lines, have excessive power losses, so when low attenuation is required microwaves are carried by metal pipes called waveguides.

Microstrip, a type of transmission line usable at microwave frequencies, was invented with printed circuits in the 1950s.

Cross-section diagram of stripline geometry. Central conductor (A) is sandwiched between ground planes (B and D). Structure is supported by dielectric (C).

Stripline

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Cross-section diagram of stripline geometry. Central conductor (A) is sandwiched between ground planes (B and D). Structure is supported by dielectric (C).

Stripline is a transverse electromagnetic (TEM) transmission line medium invented by Robert M. Barrett of the Air Force Cambridge Research Centre in the 1950s.

Good isolation between adjacent traces can be achieved more easily than with microstrip.

A 10 dB 1.7–2.2 GHz directional coupler. From left to right: input, coupled, isolated (terminated with a load), and transmitted port.

Power dividers and directional couplers

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Power dividers (also power splitters and, when used in reverse, power combiners) and directional couplers are passive devices used mostly in the field of radio technology.

Power dividers (also power splitters and, when used in reverse, power combiners) and directional couplers are passive devices used mostly in the field of radio technology.

A 10 dB 1.7–2.2 GHz directional coupler. From left to right: input, coupled, isolated (terminated with a load), and transmitted port.
A 3 dB 2.0–4.2 GHz power divider/combiner.
Figure 1. Two symbols used for directional couplers
Figure 2. Symbol for power divider
Figure 3. Graph of insertion loss due to coupling
Figure 4. Single-section λ/4 directional coupler
Figure 7. Lumped-element equivalent circuit of the couplers depicted in figures 5 and 6
Figure 8. A 5-section planar format directional coupler
Figure 9. A 3-section branch-line coupler implemented in planar format
Figure 10. Simple T-junction power division in planar format
Figure 11. Wilkinson divider in coaxial format
Figure 12. Hybrid ring coupler in planar format
Figure 13. Power Divider
Figure 14. A multi-hole directional coupler
Figure 15. Magic tee
Figure 16. 3 dB hybrid transformer for a 50 Ω system
Figure 17. Directional coupler using transformers
Figure 18. Simple resistive tee circuit for a 50 Ω system
Figure 19. 6 dB resistive bridge hybrid for a 600 Ω system
Figure 20. Two-tone receiver test setup
Figure 21. Splitter and combiner networks used with amplifiers to produce a high power 40 dB (voltage gain 100) solid state amplifier
Figure 22. Phase arrangement on a hybrid power combiner.
Figure 23. Phase combination of two antennae

They couple a defined amount of the electromagnetic power in a transmission line to a port enabling the signal to be used in another circuit.

They can be realised in a number of technologies including coaxial and the planar technologies (stripline and microstrip).