A report on 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.
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.

Specialized cable or other structure designed to conduct electromagnetic waves in a contained manner.

- 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.

34 related topics with Alpha

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Diagram of the electric fields (blue) and magnetic fields (red) radiated by a dipole antenna (black rods) during transmission.

Radio-frequency engineering

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Diagram of the electric fields (blue) and magnetic fields (red) radiated by a dipole antenna (black rods) during transmission.

Radio-frequency (RF) engineering is a subset of electronic engineering involving the application of transmission line, waveguide, antenna and electromagnetic field principles to the design and application of devices that produce or utilize signals within the radio band, the frequency range of about 20 kHz up to 300 GHz.

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.

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.

Heaviside c. 1900

Oliver Heaviside

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English self-taught mathematician and physicist who brought complex numbers to circuit analysis, invented a new technique for solving differential equations (equivalent to the Laplace transform), independently developed vector calculus, and rewrote Maxwell's equations in the form commonly used today.

English self-taught mathematician and physicist who brought complex numbers to circuit analysis, invented a new technique for solving differential equations (equivalent to the Laplace transform), independently developed vector calculus, and rewrote Maxwell's equations in the form commonly used today.

Heaviside c. 1900
Comparison of before and after the restoration project.

Undertaking research from home, he helped develop transmission line theory (also known as the "telegrapher's equations").

Radio frequency

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Oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around 20 kHz to around 300 GHz.

Oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around 20 kHz to around 300 GHz.

When conducted by an ordinary electric cable, RF current has a tendency to reflect from discontinuities in the cable, such as connectors, and travel back down the cable toward the source, causing a condition called standing waves. RF current may be carried efficiently over transmission lines such as coaxial cables.

A transmission line drawn as two black wires. At a distance x into the line, there is current phasor I(x) traveling through each wire, and there is a voltage difference phasor V(x) between the wires (bottom voltage minus top voltage). If.

Characteristic impedance

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A transmission line drawn as two black wires. At a distance x into the line, there is current phasor I(x) traveling through each wire, and there is a voltage difference phasor V(x) between the wires (bottom voltage minus top voltage). If.
Consider one section of the transmission line for the derivation of the characteristic impedance. The voltage on the left would be V and on the right side would be This figure is to be used for both the derivation methods.

The characteristic impedance or surge impedance (usually written Z0) of a uniform transmission line is the ratio of the amplitudes of voltage and current of a single wave propagating along the line; that is, a wave travelling in one direction in the absence of reflections in the other direction.

Figure 1: Example two-port network with symbol definitions. Notice the port condition is satisfied: the same current flows into each port as leaves that port.

Two-port network

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Electrical network (circuit) or device with two pairs of terminals to connect to external circuits.

Electrical network (circuit) or device with two pairs of terminals to connect to external circuits.

Figure 1: Example two-port network with symbol definitions. Notice the port condition is satisfied: the same current flows into each port as leaves that port.
Figure 2: z-equivalent two port showing independent variables I1 and I2. Although resistors are shown, general impedances can be used instead.
Figure 3: Bipolar current mirror: i1 is the reference current and i2 is the output current; lower case symbols indicate these are total currents that include the DC components
Figure 4: Small-signal bipolar current mirror: I1 is the amplitude of the small-signal reference current and I2 is the amplitude of the small-signal output current
Figure 5: Y-equivalent two port showing independent variables V1 and V2. Although resistors are shown, general admittances can be used instead.
Figure 6: H-equivalent two-port showing independent variables I1 and V2; h22 is reciprocated to make a resistor
Figure 7: Common-base amplifier with AC current source I1 as signal input and unspecified load supporting voltage V2 and a dependent current I2.
Figure 8: G-equivalent two-port showing independent variables V1 and I2; g11 is reciprocated to make a resistor
Figure 9: Common-base amplifier with AC voltage source V1 as signal input and unspecified load delivering current I2 at a dependent voltage V2.
Fig. 17. Terminology of waves used in S-parameter definition.
Fig. 10. Two two-port networks with input ports connected in series and output ports connected in series.
Fig. 13. Two two-port networks with input ports connected in parallel and output ports connected in parallel.
Fig. 14. Two two-port networks with input ports connected in series and output ports connected in parallel.
Fig. 15. Two two-port networks with input ports connected in parallel and output ports connected in series.
Fig. 16. Two two-port networks with the first's output port connected to the second's input port

Examples of circuits analyzed as two-ports are filters, matching networks, transmission lines, transformers, and small-signal models for transistors (such as the hybrid-pi model).

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.

300 ohm twin-lead

Twin-lead

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Two-conductor flat cable used as a balanced transmission line to carry radio frequency signals.

Two-conductor flat cable used as a balanced transmission line to carry radio frequency signals.

300 ohm twin-lead
A 300-to-75-ohm balun, showing twin-lead on the right hand side

Twin-lead is also used in amateur radio stations as a transmission line for balanced transmission of radio frequency signals.

A section of flexible waveguide with a pressurizable flange

Waveguide

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Structure that guides waves, such as electromagnetic waves or sound, with minimal loss of energy by restricting the transmission of energy to one direction.

Structure that guides waves, such as electromagnetic waves or sound, with minimal loss of energy by restricting the transmission of energy to one direction.

A section of flexible waveguide with a pressurizable flange
Electric field Ex component of the TE31 mode inside an x-band hollow metal waveguide.
Waveguide supplying power for the Argonne National Laboratory Advanced Photon Source.
In this military radar, microwave radiation is transmitted between the source and the reflector by a waveguide. The figure suggests that microwaves leave the box in a circularly symmetric mode (allowing the antenna to rotate), then they are converted to a linear mode, and pass through a flexible stage. Their polarisation is then rotated in a twisted stage and finally they irradiate the parabolic antenna.

Transmission lines are a specific type of waveguide, very commonly used.