Microwave engineering
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Transcript of Microwave engineering
EC402 Microwave Engineering
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Electromagnetic Spectrum
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Electromagnetic Spectrum
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Electromagnetic Spectrum
Microwave frequency range 1-30GHz wave length 30cm-1cm
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Microwave Frequency Range
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Electromagnetic Spectrum
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Electromagnetic Spectrum
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Electromagnetic Spectrum
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1. Small size wavelength f=1GHzλ=c/f=3x1010/1x109=30cm f=30GHzλ=c/f=3x1010/30x109=1cm
Wave lengths are same as dimensions of components, so distributed circuit elements or transmission theory is applied.
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Characteristics of Microwaves
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Characteristics-Large Bandwidth
Large BandwidthHigh transmission rates used for communication World’s data, TV and telephone communications are
transmitted long distances by microwaves between ground stations and communications satellite
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Characteristics-Line of sight propagation
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Characteristics-Line of sight propagation
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Characteristics-Line of sight propagation
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Characteristics-Transmission Through Ionosphere
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Characteristics-Transmission Through Ionosphere
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Characteristics-Transmission Through Ionosphere
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Characteristics- Reflection From Metallic Surfaces
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Characteristics
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Characteristics- Heating
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Characteristics- Heating
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Characteristics- Heating
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Characteristics- Microwave Resonance
Microwave Resonance: Molecular, atomic and nuclear systems exhibit resonance when Present electromagneticFields Several resonance absorption lines are in microwave range
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Application- Communications
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Point to point communications
GSM 1.8 and 1.9 GHzDVB-SH, 1.452, 1.492 GHz
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Wi-Fi
Wireless LAN networks 2.4GHz ISM band
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Wimax
Wimax(Worldwide Interoperability for Microwave Access) 2 to 11 GHzPMP-Point to multipoint links
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Wimax, WiFi
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Satellite Communications
L band (1-2 GHz )Global Positioning System (GPS) carriers and also satellite mobile phones, such as Iridium; Inmarsat providing communications at sea, land and air; WorldSpace satellite radio.
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Satellite Communications
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RADAR
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RADAR
Radar is an object-detection system that uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain.AviationMarineMeteorologists
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Heating
Domestic Application: Heating, Microwave oven
Industrial Application: Food, Rubber, leather, chemical and textile , pharmaceutical industries
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Remote Sensing
Remote sensing: Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object and thus in contrast to on site observation.
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Remote Sensing
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Radio Astronomy
Radio Astronomy: Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies.
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Radio Astronomy
Arecibo 305 m ( about 20 acres) radio telescope, located in a natural valley in Puerto Rico.
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Radio Interferometery
The Very Large Array, an interferometric array formed from many smaller telescopes
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Medical Application
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Microwave Imaging
Microwave imaging is a science which has been evolved from older detecting/locating techniques (e.g., radar) in order to evaluate hidden or embedded objects in a structure (or media)using electromagnetic (EM) waves in microwave regime (i.e., ~300 MHz-300 GHz)
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Microwave Imaging
•concealed weapon detection at security check points, structural health monitoring•through-the-wall imaging. •Disbond detection in strengthened concrete bridge• Corrosion and precursor pitting detection in painted aluminum and steel substrates •Flaw detection in spray-on foam insulation
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Industry Applications
Microwave oven Drying machines – textile, food and paper industry for drying
clothes, potato chips, printed matters etc. Food process industry – Precooling / cooking, pasteurization /
sterility, hat frozen / refrigerated precooled meats, roasting of food grains / beans.
Rubber industry / plastics / chemical / forest product industries Mining / public works, breaking rocks, tunnel boring, drying /
breaking up concrete, breaking up coal seams, curing of cement.
Drying inks / drying textiles, drying / sterilizing grains, drying / sterilizing pharmaceuticals, leather, tobacco, power transmission.
Biomedical Applications ( diagnostic / therapeutic ) – diathermy for localized superficial heating, deep electromagnetic heating for treatment of cancer, hyperthermia ( local, regional or whole body for cancer therapy).
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Advantages
Large Bandwidth: It is very good advantage, because of this, Microwaves are used for Point to Point Communications.
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Advantages
Better Directivity
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Advantages
Better Directivity: At Microwave Frequencies, there are better directive properties. This is due to the relation that as Frequency Increases, Wavelength decreases and as Wavelength decreases Directivity Increases and Beam width decreases. So it is easier to design and fabricate high gain antenna in Microwaves.
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Advantages
Small Size Antenna
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Advantages
Low Power Consumption
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Advantages
Low Power Consumption:The power required to transmit a high frequency signal is lesser than the power required in transmission of low frequency signals. As Microwaves have high frequency thus requires very less power.
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Advantages
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Effect Of Fading
Space wave Sky wave
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Advantages
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Effect Of Fading: The effect of fading is minimized by using Line Of Sight propagation technique at Microwave Frequencies. While at low frequency signals, the layers around the earth causes fading of the signal.
Space wave Sky wave
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Fresnel Zone
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Fresnel Zone
there should be no reflective objects in the 1st Fresnel zoneeven Fresnel zone are out of phase with the direct-path wave and reduce the power of the received signalodd Fresnel zone are in phase with the direct-path wave and can enhance the power
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Limitations of Tubes at High Frequencies
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Vacuum tubes- Triode
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Triode Amplifier Circuit
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Limitations at Higher Frequencies
Inter electrode Capacitance
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Inter electrode Capacitance
Limitations at Higher Frequencies
At frequencies greater than 1 GHz
Limitations at Higher Frequencies
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Leads:Leads are used for physical support, to transfer power and sometimes as a Heatsink.
Limitations at Higher Frequencies Limitations at Higher Frequencies
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Leads:Leads are used for physical support, to transfer power and sometimes as a Heatsink.
Limitations at Higher Frequencies
In fact, any wires or component leads that have current flowing through them create magnetic fields. When these magnetic fields are created, they can produce an inductive effect. Thus, wires or components leads can act as inductors if they are long enough
Limitations at Higher Frequencies
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Parasitic Inductance and capacitance becomes very large At Microwave frequencies
Limitations at Higher Frequencies Limitations at Higher Frequencies
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Limitations at Higher Frequencies
Reduce length of and area of leads, in turn reduces Power handled.
Limitations at Higher Frequencies
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Limitations at Higher Frequencies
Input conductance loads the circuitry, efficiency reduces.
Limitations at Higher Frequencies
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Lead Inductance
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Inter electrode Capacitance
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Input Impedance
Input Voltage
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Input Impedance
Input Current
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Input Impedance
Input Admittance
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Input Impedance
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Input Impedance
Input Impedance
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Input Impedance
Input Impedance
Input conductance loads the circuitry, efficiency reduces.
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Gain Bandwidth
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Gain Bandwidth
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Gain Bandwidth
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Gain Bandwidth
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Gain Bandwidth
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Gain Bandwidth
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Gain Bandwidth
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Gain Bandwidth
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Gain Bandwidth
Gain bandwidth product is independent of frequency, hence is constant. Hence resonant circuits are reentrant or slow wave structures
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Transit Time
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Transit Time
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Transit Time
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Transit Time
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Transit Time
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Transit Time
•In the positive half-cycle, grid potential attracts the electron beam and supplies energy to it
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Transit Time
•In the negative half-cycle, it repels the electron beam and extracts energy from it.
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Transit Time
As a result, the electron beam oscillates back and forth in the region between the cathode and the grid, and may even return to the cathode.
The overall result is a reduction of the operating frequency of the vacuum tube.
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Transit Time
Reduce Transit Time•Increasing the anode voltage •Decreasing the inter-electrode spacing
However, the increase in anode voltage will increase the power dissipation,
whereas the decrease in inter-electrode spacing will increase the inter-electrode capacitance.
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Transit Time
The increase in inter-electrode capacitance can be reduced by reducing the area of the electrodes, but this will reduce anode dissipation and hence the output power.
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RF Loss- Skin Effect Loss
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RF Loss- Skin Effect Loss
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RF Loss- Skin Effect Loss Skin effect loss At a high frequency, current has a tendency to concentrate around the surface rather than being distributed throughout the cross section. This is known as skin effect. It reduces the effective surface area, which in turn increases the resistance and hence the loss of the device. Resistance loss is also proportional to the square of the frequency. Losses due to skin effect can be reduced by increasing the current-carrying area, which, in turn, increases the inter-electrode capacitance and thus limits high frequency operations.
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RF Loss- Dielectric Loss
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RF Loss- Dielectric Loss
Dielectric loss Dielectric loss in a material is proportional to frequency, and hence plays an important role in the operations of high-frequency tubes. This loss can be avoided by eliminating the tube base and reducing the surface area of the dielectric materials, and can be reduced by placing insulating materials at the point of minimum electric field.
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Radiation Loss
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Radiation Loss
Radiation loss At higher frequencies, the length of the leads approaches the operating wavelength, and as a result these start radiating. Radiation loss increases with the increase in frequency and hence is very severe at microwave frequencies. Proper shielding is required to avoid this loss. Radiation loss can be minimized by enclosing the tubes or using a concentric line construction
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Resonator
A resonator is a device or system that exhibits resonance or resonant behavior, that is, it naturally oscillates at some frequencies, called its resonant frequencies, with greater amplitude than at others.
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Resonant Circuit
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Resonant Circuit
An electrical circuit composed of discrete components can act as a resonator when both an inductor and capacitor are included. Such resonant circuits are also called RLC circuits after the circuit symbols for the components.
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Cavity Resonator
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Cavity Resonator
A cavity resonator, usually used in reference to electromagnetic resonators, is one in which waves exist in a hollow space inside the device
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Cavity Resonator Due to the low resistance of their conductive walls, cavity resonators have very high Q factors; that is their bandwidth, the range of frequencies around the resonant frequency at which they will resonate, is very narrow.
Thus they can act as narrow bandpass filters. Cavity resonators are widely used as the frequency determining element in microwave oscillators.
Their resonant frequency can be tuned by moving one of the walls of the cavity in or out, changing its size.
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Rectangular Cavity Resonator
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Rectangular Cavity Resonator
For a > b < d, the dominant mode is the TE101 mode.
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Rectangular Cavity Resonator
The electric field lines start from top and bottom, positive and negative charges are induced, hence forms capacitor
The current flows via side walls and hence serve as inductor, hence the enclosed volume behaves as tank circuit.
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Circular Cavity Resonator
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Circular Cavity Resonator
TE111 mode is the dominant mode.
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Quality Factor
The Q factor (quality factor) of a resonator is a measure of the strength of the damping of its oscillations, or for the relative linewidth.
the Q factor is 2π times the ratio of the stored energy to the energy dissipated per oscillation cycle
the Q factor is the ratio of the resonance frequency ν0 and the full width at half-maximum (FWHM)bandwidth δν of the resonance:
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Quality Factor
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Reentrant Cavity Resonator
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Reentrant Cavity Resonator
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Reentrant Cavity Resonator
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Reentrant Cavity Resonator
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Excitation Wave Modes
Loop coupling Probe coupling
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Excitation Wave Modes
Probe coupling
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Excitation Wave Modes
Loop coupling
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Aperture Coupling
Aperture coupling
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Coupling Between Waveguides
Directional Coupler
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Linear Beam Tubes-Otype Tubes
Electric Field is applied to the accelerate or decelerate the Electron beam
Magnetic Field is applied along the axis toFocus the electron beam.
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Klystron
an electron tube that generates or amplifies microwaves by velocity modulation.
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Klystron
an electron tube that generates or amplifies microwaves by velocity modulation.
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Klystron- Velocity Modulation
Velocity of electrons accelerated by high DC Voltage
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Klystron- Velocity Modulation
Gap Voltage applied at Buncher grids
Where
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Klystron- Velocity Modulation
Gap Voltage applied at Buncher grids
Where
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Klystron- Velocity Modulation
Average transit time through buncher gap
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Klystron- Velocity Modulation
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Klystron- Velocity Modulation
Average Voltage across the buncher gap
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Klystron- Velocity Modulation
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Klystron- Velocity Modulation
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Klystron- Velocity Modulation
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Klystron- Velocity Modulation
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Klystron- Velocity Modulation
Equation for Velocity Modulation
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Klystron- Bunching Process
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Klystron- Bunching Process
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Klystron- Bunching Process
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Klystron- Bunching Process
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Klystron- Bunching Process
Distance travelled by the electrons in drift space.
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Klystron- Current Modulation
Beam Current varies with the applied RF voltage –current modulation.
Fundamental component of current
Current becomes maximum at
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Klystron- Current Modulation
Optimum distance for bunching
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Klystron
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Applegate Diagram
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Output Power
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Output Power
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Efficiency
Theoretical efficiency is 58%Where as practical efficiency is 15% to 30%
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Voltage Gain
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Typical Values
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Applications
As power output tubes1. in UHF TV transmitters2. in troposphere scatter
transmitters3. satellite communication
ground station4. radar transmitters
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Klystron
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Multi cavity Klystron
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Reflex Klystron
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Reflex Klystron
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Velocity Modulation
Velocity of the electrons in entering the cavity gap
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Velocity Modulation
Exit Velocity of the electrons in leaving the cavity gap
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Velocity Modulation
Retarding Electric Field
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Velocity Modulation
Force equation of one electron assuming V1<<(Vr+Vo)
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Reflex Klystron
Integrating
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Reflex Klystron
Integrating
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Reflex Klystron
Integrating
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Reflex Klystron
Integrating
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Reflex Klystron
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Reflex Klystron
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Reflex Klystron
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Transit Time
Round trip transit time in the repeller region
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Transit Time
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Applegate Diagram
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Applegate Diagram
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Efficiency
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Efficiency of Reflex Klystron
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Characteristics of Reflex Klystron
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Electronic Admittance
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Electronic Admittance
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Electronic Admittance
Bunched electrons return to the cavity gap a little before the transit time, current leads the behind the field-capacitance appears in the circuit
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Electronic Admittance
Bunched electrons return to the cavity gap a little after toThe ac current lags the field –inductance reactance appears in the circuit
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Electronic Admittance
Condition for oscillation Ge is negative and total conductance in the circuit is negative –Ge>Gc+Gl
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Applications
Low power oscillator- 10mw to 500mwFrequency 1-25GHz
Local Oscillator in commercial , Military, Air borne Doppler radar and missiles.
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Tuning Klystron
Electronic Tuning
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Tuning Klystron
Mechanical Tuning: By changing capacitance or inductance
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Klystron
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Klystron
Output is via a co-axial pin, and the device can be mechanically tuned with the screw on the left, which applies vertical compression to the metal envelope.
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Amplitude Modulation -Klystron
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Frequency Modulation Klystron
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Slow Wave Structures
Non Resonant periodic circuitsProduce large gain over wide bandwidth
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Slow Wave Structures
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Slow Wave Structure
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Phase Velocity
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Group Velocity
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Travelling wave tube
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Travelling wave tube
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Travelling wave tube
Amplifiers in satellite transponders, where the input signal is very weak and the output needs to be high power.
TWTA transmitters are used extensively in radar, particularly in airborne fire-control radar systems, and in electronic warfare and self-protection systems
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Linear Beam tubes –O type
Klystron – Resonant , standing waveReflex Klystron- Resonant, standing waveTravelling wave tube- Non resonant, travelling wave
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Travelling wave tube
Amplifies a wide range of frequencies, a wide bandwidth and low noise.
Bandwidth two octaves, while the cavity versions have bandwidths of 10–20%.
Operating frequencies range from 300 MHz to 50 GHz.
The power gain of the tube is on the order of 40 to 70 decibels
Output power ranges from a few watts to megawatts
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Octave
A frequency is said to be an octave in width when the upper band frequency is twice the lower band frequency
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Crossed Field tubes –M type
Crossed-field tubes derive their name from the fact that the dc electric field and the dC magnetic field are perpendicular to each other.
They are also called M –type tubes
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Cylindrical Magnetron
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Travelling wave Magnetron
Depend upon the interaction of electrons with a rotating electromagnetic field of same angular velocity.
Provide oscillations of very high peak power and hence are useful in radar applications
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Cavity Magnetron
Fig (i) Major elements in the Magnetron oscillator
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Anode Assembly
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Construction
Each cavity in the anode acts as an inductor having only one turn and the slot connecting the cavity and the interaction space acts as a capacitor.
These two form a parallel resonant circuit and its resonant frequency depends on the value of L of the cavity and the C of the slot.
The frequency of the microwaves generated by the magnetron oscillator depends on the frequency of the RF oscillations existing in the resonant cavities.
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Crossed Field tubes –M type
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Reentrant Cavity
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Reentrant Cavity
E
B
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Crossed Field tubes –M type
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Description
Magnetron is a cross field device as the electric field between the anode and the cathode is radial whereas the magnetic field produced by a permanent magnet is axial.
A high DC potential can be applied between the cathode and anode which produces the radial electric field.
Depending on the relative strengths of the electric and magnetic fields, the electrons emitted from the cathode and moving towards the anode will traverse through the interaction space as shown in Fig. (iii).
In the absence of magnetic field (B = 0), the electron travel straight from the cathode to the anode due to the radial electric field force acting on it, Fig (iii) a.
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Cavity Magnetron
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Cavity Magnetron
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Cavity Magnetron
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Cavity Magnetron
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Crossed Field tubes –M type
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Description
If the magnetic field strength is increased slightly, the lateral force bending the path of the electron as given by the path ‘b’ in Fig. (iii).
The radius of the path is given by, If the strength of the magnetic field is made sufficiently high then the electrons can be prevented from reaching the anode as indicated path ‘c’ in Fig. (iii)),
The magnetic field required to return electrons back to the cathode just grazing the surface of the anode is called the critical magnetic field (Bc) or the cut off magnetic field.
If the magnetic field is larger than the critical field (B > Bc), the electron experiences a greater rotational force and may return back to the cathode quite faster.
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Crossed Field tubes –M type
Fig (iii) Electron trajectories in the presence of crossed electric
and magnetic fields (a) no magnetic field
(b) small magnetic field(c) Magnetic field = Bc
(d) Excessive magnetic field
e-
B
Fm
e-
B
Effect of electric field Effect of magnetic field
E
e-
Effect of Crossed-Fields
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Hull Cut off Condition
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Crossed Field tubes –M type
Force due to magnetic field on charge Q moving with velocity v
Force on electron moving with velocity v
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Crossed Field tubes –M type
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Crossed Field tubes –M type
Force due to electric field on electron
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Crossed Field tubes –M type
Magnetic Field Bz az
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Equations of electrons in motion
Acceleration due to electric field
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Equations of Electrons in motion
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Hull Cut off Condition
Rearranging the equation (2)
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Hull Cut off Condition
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Angular Velocity
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Kinetic Energy of Electrons
Velocity of electrons
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Crossed Field tubes –M type
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Crossed Field tubes –M type
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Crossed Field tubes –M type
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Crossed Field tubes –M type
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Hull Cutoff Magnetic Equation
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Hull Cutoff Voltage Equation
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Cyclotron Angular Frequency
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Cyclotron Angular Frequency
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Time Period
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Phase shift between adjacent cavities
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Crossed Field tubes –M type
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Phase constant
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π Mode
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RF Field
PH0101 Unit 2 Lecture 5 235
WorkingFig (iv) Possible trajectory of electrons from cathode to anode in an eight cavity
magnetron operating in mode
PH0101 Unit 2 Lecture 5 236
Working The RF Oscillations of transient nature produced when
the HT is switched on, are sufficient to produce the oscillations in the cavities, these oscillations are maintained in the cavities reentrant feedback which results in the production of microwaves.
Reentrant feedback takes place as a result of interaction of the electrons with the electric field of the RF oscillations existing in the cavities.
The cavity oscillations produce electric fields which fringe out into the interaction space from the slots in the anode structure, as shown in Fig (iv).
Energy is transferred from the radial dc field to the RF field by the interaction of the electrons with the fringing RF field.
PH0101 Unit 2 Lecture 5 237
Working Due to the oscillations in the cavities, the either sides of
the slots (which acts as a capacitor) becomes alternatively positive and negative and hence the directions of the electric field across the slot also reverse its sign alternatively.
At any instant the anode close to the spiraling electron goes positive, the electrons gets retarded and this is because; the electron has to move in the RF field, existing close to the slot, from positive side to the negative side of the slot.
In this process, the electron loses energy and transfer an equal amount of energy to the RF field which retard the spiraling electron.
On return to the previous orbit the electron may reach the adjacent section or a section farther away and transfer energy to the RF field if that part of the anode goes positive at that instant.
PH0101 Unit 2 Lecture 5 238
Working This electron travels in a longest path from cathode to the
anode as indicated by ‘a’ in Fig (iv), transferring the energy to the RF field are called as favoured electrons and are responsible for bunching effect and give up most of its energy before it finally terminates on the anode surface.
An electron ‘b’ is accelerated by the RF field and instead of imparting energy to the oscillations, takes energy from oscillations resulting in increased velocity, such electrons are called unfavoured electrons which do not participate in the bunching process and cause back heating.
Every time an electron approaches the anode “in phase” with the RF signal, it completes a cycle. This corresponds to a phase shift 2.
For a dominant mode, the adjacent poles have a phase difference of radians, this called the - mode.
PH0101 Unit 2 Lecture 5 239
Fig (v) Bunching of electrons in multicavity magnetron
PH0101 Unit 2 Lecture 5 240
Working
At any particular instant, one set of alternate poles goes positive and the remaining set of alternate poles goes negative due to the RF oscillations in the cavities.
AS the electron approaches the anode, one set of alternate poles accelerates the electrons and turns back the electrons quickly to the cathode and the other set alternate poles retard the electrons, thereby transferring the energy from electrons to the RF signal.
This process results in the bunching of electrons, the mechanism by which electron bunches are formed and by which electrons are kept in synchronism with the RF field is called phase focussing effect. electrons with the fringing RF field.
PH0101 Unit 2 Lecture 5 241
Working
The number of bunches depends on the number of cavities in the magnetron and the mode of oscillations, in an eight cavity magnetron oscillating with - mode, the electrons are bunched in four groups as shown in Fig (v).
Two identical resonant cavities will resonate at two frequencies when they are coupled together; this is due to the effect of mutual coupling.
Commonly separating the pi mode from adjacent modes is by a method called strapping. The straps consist of either circular or rectangular cross section connected to alternate segments of the anode block.
PH0101 Unit 2 Lecture 5 242
Performance Characteristics
1. Power output: In excess of 250 kW ( Pulsed Mode), 10 mW (UHF band), 2 mW (X band), 8 kW (at 95 GHz)
2. Frequency: 500 MHz – 12 GHz
3. Duty cycle: 0.1 %
4. Efficiency: 40 % - 70 %
PH0101 Unit 2 Lecture 5 243
Applications of Magnetron
1. Pulsed radar is the single most important application with large pulse powers.
2. Voltage tunable magnetrons are used in sweep oscillators in telemetry and in missile applications.
3. Fixed frequency, CW magnetrons are used for industrial heating and microwave ovens.
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Mode Jumping
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Mode Jumping
Strapping Rising sun structure
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Disadvantages
•They are costly and hence limited in use.
•Although cavity magnetron are used because they generate a wide range of frequencies , the frequency is not precisely controllable.
•The use in radar itself has reduced to some extent, as more accurate signals have generally been needed and developers have moved to klystron and systems for accurate frequencies.
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Cross Field Amplifier
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Cross Field AmplifierThe Crossed-Field Amplifier (CFA), is a broadband microwave amplifier that can also be used as an oscillator (Stabilotron).
It is a so called Velocity-modulated Tube . The CFA is similar in operation to themagnetron and is capable of providing relatively large amounts of power with high efficiency.
In contrast to the magnetron, the CFA have an odd number of resonant cavities coupled with each other. These resonant cavities work to as a slow-wave structure: an oscillating resonant cavity excites the next cavity.
The actual oscillation will be lead from the input waveguide to the output waveguide.
The electric and magnetic fields in a CFA are perpendicular to each other (“crossed fields”). Without an input signal and the influence of both the electric field (anode voltage) and the magnetic field (a strong permanent magnet) all electrons will move uniformly from the cathode to the anode on a cycloidal path as shown in figure
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Cross Field AmplifierIf the input-waveguide introduces an oscillation into the first resonator, the vanes of the resonator gets a voltage difference synchronously to the oscillation.
Under the influence of this additionally field flying past electrons get acceleration (at the positively charged vane) or they are decelerated (at the negatively charged vane). This causes a difference in speed of the electrons. The faster electrons catch the slower electrons and the forms electron bunches in the interaction space between the cathode and the anode.
These bunches of electrons rotates as like as the “Space-Charge Wheel” known from the magnetron operation. But they cannot rotate in full circle, the “Space-Charge Wheel” will be interrupted because the odd number of cavities causes an opposite phase in the last odd cavity (this bottom one between the waveguides).
To avoid a negative feedback, into this resonant cavity may exist a bloc containing graphite to decouple input and output.
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Cross Field Amplifier
The bandwidth of the CFA, at any given instant, is approximately plus or minus 5 percent of the rated center frequency.
Any incoming signals within this bandwidth are amplified. Peak power levels of many megawatts and average power levels of tens of kilowatts average are, with efficiency ratings in excess of 70 percent, possible with crossed-field amplifiers.
To avoid ineffective modes of operation the construction of CFA contains strapping wires like to as used in magnetrons.
Because of the desirable characteristics of wide bandwidth, high efficiency, and the ability to handle large amounts of power, the CFA is used in many applications in microwave electronic systems.
When used as the intermediate or final stage in high-power radar systems, all of the advantages of the CFA are used.