A report on Microwave and Transmission line

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.

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

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.

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

Waveguide is used to carry microwaves. Example of waveguides and a diplexer in an air traffic control radar

Variations on the schematic electronic symbol for a transmission line.

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

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.

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.

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.

Small microwave oven on a kitchen counter

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.

Microwaves are widely used for heating in industrial processes. A microwave tunnel oven for softening plastic rods prior to extrusion.

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

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 and above, power losses in transmission lines become excessive, and waveguides are used instead, which function as "pipes" to confine and guide the electromagnetic waves.

- Transmission line

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.

- Microwave

10 related topics with Alpha

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.

Microstrip lines are used to convey microwave-frequency signals.

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.

A 3 dB 2.0–4.2 GHz power divider/combiner.

Figure 1. Two symbols used for directional couplers

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 14. A multi-hole directional coupler

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 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.

This technique is favoured at the microwave frequencies where transmission line designs are commonly used to implement many circuit elements.

A stack of "fishbone" and Yagi–Uda television antennas

Antenna (radio)

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Antenna or aerial is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver.

Animation of a half-wave dipole antenna radiating radio waves, showing the electric field lines. The antenna in the center is two vertical metal rods connected to a radio transmitter (not shown). The transmitter applies an alternating electric current to the rods, which charges them alternately positive (+) and negative (−). Loops of electric field leave the antenna and travel away at the speed of light; these are the radio waves. In this animation the action is shown slowed down enormously.

Antennas of the Atacama Large Millimeter/submillimeter Array.

An automobile's whip antenna, a common example of an omnidirectional antenna.

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

Standing waves on a half wave dipole driven at its resonant frequency. The waves are shown graphically by bars of color ( red for voltage, V and blue for current, I ) whose width is proportional to the amplitude of the quantity at that point on the antenna.

Typical center-loaded mobile CB antenna with loading coil

Polar plots of the horizontal cross sections of a (virtual) Yagi-Uda-antenna. Outline connects points with 3 dB field power compared to an ISO emitter.

The wave reflected by earth can be considered as emitted by the image antenna.

The currents in an antenna appear as an image in opposite phase when reflected at grazing angles. This causes a phase reversal for waves emitted by a horizontally polarized antenna (center) but not for a vertically polarized antenna (left).

A receiving antenna may include not only the passive metal receiving elements, but also an integrated preamplifier or mixer, especially at and above microwave frequencies.

An antenna lead-in is the transmission line, or feed line, which connects the antenna to a transmitter or receiver.

Transmitter

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Electronic device which produces radio waves with an antenna.

A radio transmitter is usually part of a radio communication system which uses electromagnetic waves (radio waves) to transport information (in this case sound) over a distance.

Animation of a half-wave dipole antenna transmitting radio waves, showing the electric field lines. The antenna in the center is two vertical metal rods, with an alternating current applied at its center from a radio transmitter (not shown). The voltage charges the two sides of the antenna alternately positive (+) and negative (−) . Loops of electric field (black lines) leave the antenna and travel away at the speed of light; these are the radio waves. This animation shows the action slowed enormously

Hertz discovering radio waves in 1887 with his first primitive radio transmitter (background).

Guglielmo Marconi's spark gap transmitter, with which he performed the first experiments in practical Morse code radiotelegraphy communication in 1895-1897

High power spark gap radiotelegraphy transmitter in Australia around 1910.

1 MW US Navy Poulsen arc transmitter which generated continuous waves using an electric arc in a magnetic field, a technology used for a brief period from 1903 until vacuum tubes took over in the 20s

An Alexanderson alternator, a huge rotating machine used as a radio transmitter at very low frequency from about 1910 until World War 2

One of the first vacuum tube AM radio transmitters, built by Lee De Forest in 1914. The early Audion (triode) tube is visible at right.

One of the BBC's first broadcast transmitters, early 1920s, London. The 4 triode tubes, connected in parallel to form an oscillator, each produced around 4 kilowatts with 12 thousand volts on their anodes.

Armstrong's first experimental FM broadcast transmitter W2XDG, in the Empire State Building, New York City, used for secret tests 1934–1935. It transmitted on 41 MHz at a power of 2 kW.

Transmitter assembly of a 20 kW, 9.375 GHz air traffic control radar, 1947. The magnetron tube mounted between two magnets (right) produces microwaves which pass from the aperture (left) into a waveguide which conducts them to the dish antenna.

In more powerful transmitters, the antenna may be located on top of a building or on a separate tower, and connected to the transmitter by a feed line, that is a transmission line.

The development of radar during World War II motivated the evolution of high frequency transmitters in the UHF and microwave ranges, using new active devices such as the magnetron, klystron, and traveling wave tube.

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.

Two-port network

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

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).

S-parameters are used primarily at UHF and microwave frequencies where it becomes difficult to measure voltages and currents directly.

Radio-frequency engineering

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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.

At microwave frequencies, the reactance of signal traces becomes a crucial part of the physical layout of the circuit.

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.

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.

The original and most common meaning is a hollow conductive metal pipe used to carry high frequency radio waves, particularly microwaves.

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

A variety of parabolic antennas on a communications tower in Australia for point-to-point microwave communication links. Some have white plastic radomes over their apertures to protect against rain.

Super high frequency

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ITU designation for radio frequencies (RF) in the range between 3 and 30 gigahertz (GHz).

X-band (8 - 12 GHz) marine radar antenna on a ship. The rotating bar sweeps a vertical fan-shaped beam of microwaves around the water surface to the horizon, detecting nearby ships and other obstructions

Microwaves are often carried by waveguide, such as this example from an air traffic control radar, since other types of cable have large power losses at SHF frequencies.

These frequencies fall within the microwave band, so radio waves with these frequencies are called microwaves.

At microwave frequencies, the types of cable (transmission line) used to conduct lower frequency radio waves, such as coaxial cable, have high power losses.

Resonator

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Device or system that exhibits resonance or resonant behavior.

An illustration of the electric and magnetic field of one of the possible modes in a cavity resonator.

RF cavities in the linac of the Australian Synchrotron are used to accelerate and bunch beams of electrons; the linac is the tube passing through the middle of the cavity.

A sport motorcycle, equipped with exhaust resonator, designed for performance

Since the cavity's lowest resonant frequency, the fundamental frequency, is that at which the width of the cavity is equal to a half-wavelength (λ/2), cavity resonators are only used at microwave frequencies and above, where wavelengths are short enough that the cavity is conveniently small in size.

Transmission lines are structures that allow broadband transmission of electromagnetic waves, e.g. at radio or microwave frequencies.