Booking open Available Pune Call Girls Koregaon Park 6297143586 Call Hot Ind...
Microwave components
1. TR
MICROWAVE SIGNAL
GENERATION
Date of seminar : 15th
Oct’ 2016 Tech park, SRM university, KTR campus
Subject EC0302 & MICROWAVE AND RF DESIGN
Topic MICROWAVE SIGNAL GENERATION
Audience 5th
semester students of ECE (part time), 2014-2017 batch
Faculty & Guide Ms. P. Malarvizhi, Asst. Professor, ECE dept at SRM university
Prepared &
presented by
K Sridharan, ECE (PT), 2014-2017 batch at SRM university
1
2. Objective
In this seminar, students should able to understand
the use of various microwave tubes & solid state
semiconductor devices which are used to Generate
or Amplify Microwave signals ranging from 300MHz
to 300GHz
2
3. Contents
3
The Electromagnetic Spectrum
Various Frequency ranges
Use of each Frequency range
Microwave Frequency and Band designation
Generation of Microwave signal
Microwave Tubes
Microwave solid state devices
Generation of Microwave signal using Microwave tubes
Generation of Microwave signal using Solid state devices
Comparison of Microwave signal generated using Microwave Tubes and solid
state devices
TRAPATT diode (the seminar topic)
Applications of solid state devices
Measuring of Microwave signal using Spectrum analyzer
4. The Electromagnetic spectrum
Increasing wave length
Increasing energy
• The electromagnetic spectrum is the term used by scientists to describe the entire range of light that
exists. From radio waves to gamma rays, most of the light in the universe is invisible to us!
• “Light is a wave of alternating electric and magnetic fields which is only visible to us!” 4
5. Various Frequency ranges
Radio
Frequency
Microwave
Frequency
Infrared light, ultraviolet light, X-rays and gamma-rays
AudioFrequency
Frequency Wavelength Designation
Abbreviati
on
3–30 Hz 105
–104
km Extremely low frequency ELF
30–300 Hz 104
–103
km Super low frequency SLF
300–3000 Hz 103
–100 km Ultra low frequency ULF
3–20 kHz 100–10 km Very low frequency VLF
20–300 kHz 10–1 km Low frequency LF
300 kHz – 3 MHz 1 km – 100 m Medium frequency MF
3–30 MHz 100–10 m High frequency HF
30–300 MHz 10–1 m Very high frequency VHF
300 MHz – 3 GHz 1 m – 10 cm Ultra high frequency UHF
3–30 GHz 10–1 cm Super high frequency SHF
30–300 GHz 1 cm – 1 mm Extremely high frequency EHF
300 GHz & >3 THz 1 mm – 0.1 mm
Tremendously high frequency
(Tera Herts)
THF
5
6. Use of each Frequency range
Abbreviation Example uses
ELF Communication with submarines
SLF Communication with submarines
ULF Submarine communication, communication within mines
VLF Navigation, time signals, submarine communication, wireless heart rate monitors, geophysics
LF
Navigation, clock time signals, AM longwave broadcasting (Europe and parts of Asia), RFID, amateur
radio
MF AM (medium-wave) broadcasts, amateur radio, avalanche beacons
HF
Shortwave broadcasts, citizens' band radio, amateur radio and over-the-horizon aviation
communications, RFID, over-the-horizon radar, automatic link establishment (ALE) / near-vertical
incidence skywave (NVIS) radio communications, marine and mobile radio telephony
VHF
FM, television broadcasts and line-of-sight ground-to-aircraft and aircraft-to-aircraft communications,
land mobile and maritime mobile communications, amateur radio, weather radio
UHF
(Microwave)
Television broadcasts, microwave oven, microwave devices/communications, radio astronomy, mobile
phones, wireless LAN, Bluetooth, ZigBee, GPS and two-way radios such as land mobile, FRS and
GMRS radios, amateur radio
SHF
(Microwave)
Radio astronomy, microwave devices/communications, wireless LAN, most
modern radars,communications satellites, cable and satellite television broadcasting, DBS, amateur
radio
EHF
(Microwave)
Radio astronomy, high-frequency microwave radio relay, microwave remote sensing, amateur
radio,directed-energy weapon, millimeter wave scanner
THz or THF
Experimental medical imaging to replace X-rays, ultrafast molecular dynamics, condensed-matter
physics, terahertz time-domain spectroscopy, terahertz computing/communications, remote sensing,
amateur radio
6
7. Microwave Frequency Band designation
Band Frequency Range Origin of Name
I up to 200 MHz Unknown
G 200 to 250 MHz Unknown
P 250 to 500 MHz P for "previous", as the British used the band for the earliest
radars, but later switched to higher frequencies.
L 0.5 to 1.5 GHz L for "long" wave.
S 2 to 4 GHz S for "short" wave. Don't confuse this with the short wave radio
band, which is much lower in frequency
C 4 to 8 GHz C for "compromise" between S and X band.
X 8 to 12 GHz Used in WW II for fire control, X for cross (as in crosshair)
Ku 12 to 18 GHz Ku for "kurz-under".
K 18 to 26 GHz German "kurz" means short, yet another reference to short
wavelength.
Ka 26 to 4-0 Ka for "kurz-above".
V 40 to 75 GHz V for "very" high frequency band (not to be confused with VHF)
W 75 to 110 GHz W follows V in the alphabet 7
8. Microwave signal generation
Following devices are mainly used to generate microwave signals ranging
from 300MHz to 300 GHz
Microwave Tubes Microwave solid state devices
Klystron Amplifiers Microwave Transistor & FET
Reflex Klystron Oscillators Gunn oscillator
Magnetron Oscillators IMPATT diode
Helix TWT Amplifiers TRAPATT diode (seminar Topic)
BARITT diode
PIN diode
TUNNEL diode
8
9. Generation of Microwave signal using
Vacuum Tubes
Microwave Tubes
Klystron Amplifiers
Reflex Klystron Oscillators
Magnetron Oscillators
Helix TWT Amplifiers
9
These Microwave Tubes works as per velocity modulation principle
11. Klystron Amplifiers
Klystron is one of the high
power vacuum tubes used in
radar system as amplifier and
oscillator. It is similar to pipe
organ tube where air in the
tube vibrates and produces
sound energy of desired
frequency. In klystron,
instead of air, electrons are
used which vibrate at desired
frequency inside the glass
tube and generates
microwave energy.
Klystron
Frequency
In the range of 100GHz &
above
Bandwidth 2-4%
Power output Up to 50MW
Amplification Up to 60 Db
Function as
Microwave oscillator and
small-band power amplifier
Two-cavity klystron
Invented in 1937 11
12. Reflex Klystron Oscillators
Low power klystron tube
with a single cavity, which
functioned as an oscillator
. It was used as a
local oscillator in some
radar receivers and a
modulator in microwave
transmitters the 1950s
and 60s, but is now
obsolete, replaced by
semiconductor microwave
devices.
Reflex Klystron
Frequency 4GHz – 200GHz
Bandwidth 2-4%
Power output
maximum 3W in X-
band to 10mW at
220GHz.
Amplification Up to 60 Db
Function as
Microwave oscillator &
Amplifier
12
Note: Reflex Klystron is replaced with Gunn diode now
13. Magnetron
Klystron Magnetron
It can be used both as amplifier
and oscillator.
It can only be used as oscillator.
Application: It is used in TV
transmitter, radar and particle
accelerators. Here it is used as
high power, narrowband stable
amplifier.
Application: It is used in
microwave ovens, operating at
2.45 GHz. It is also used for RF
heating when operating at 900MHz
or 2.45GHz.
Magnetron
Frequency Up to 95 GHz
Bandwidth Any mega hertzes
Power
output Up to 10MW
AmplificationNo amplification
Function as
High power oscillator as
one Frequency
Picture of Magnetron used
in Microwave oven
13
14. Helix Travelling wave Tube
<--Electrongun
<--RFoutput
<--RFInput
<--Magnets
<--Attenuator
<--Helixcoil
<--VacuumTube
<--Collector
• A traveling-wave tube (TWT) is a specialized
vacuum tube that is used in electronics to amplify
radio frequency (RF) signals in the microwave
range.
• In TWT, radio waves interact with the electron
beam while traveling down a wire helix which
surrounds the beam
• Radio wave is amplified by absorbing power from
a beam of electrons as it passes down the tube
Helix TWD
Frequency Up to 95 GHz
Bandwidth 10-20%
Power output Up to 1MW
Amplification Up to 50 Bb
Function as wide band, low Noise voltage amplifier
Picture of Helix TWT
Among all methods of microwave generation >50% of
the time, TWT is used for microwave signal
amplification
14
16. Generation of Microwave signal using
semiconductor solid state Devices
16
Since it become impractical to generate low power microwave signal using vacuum
tubes, semiconductor solid state Devices used to generated low power microwave signal
17. 17
Microwave solid state devices
Microwave Transistor & FET
Gunn oscillator
IMPATT diode
TRAPATT diode (seminar Topic)
BARITT diode
PIN diode
TUNNEL diode
Semiconductor solid state Devices
18. Pictures of various Microwave solid state devices
18
GUNN GUNN
GUNN
GUNN (assembled with Horn
antenna)
GUNN
IMPATT diode GUNN PIN diode
19. 19
Specifications Gunn diode Impatt diode Trapatt diode Baritt diode
Bandwidth
2% of RF center
frequency
1/10th of RF center
frequency
- Narrow
Operationg
frequency
1 to 100GHz 0.5 to 100GHz 1 to 10GHz 4 to 8GHz
Efficiency -
3% in CW, 60% in pulsed
mode
20 to 60% pulsed
mode
Low(about 2%)
Output power
few watts (continuous
wave),
100 to
200Watt(pulsed)
1 Watt(CW),
400Watt(Pulsed)
Several
100Watt(pulsed)
Low(mWatt)
Noise figure - High, 30dB High, 60dB
Less noisy than
IMPATT diode(<15dB)
Basic
semiconductors
GaAs, InP Si, Ge, GaAs, InP Si Si, metal
Construction
n+
n n+
GaAs single
crystal
n+
pip+
reverse bias p-n
junction
p+
nn++
or n+
p
p+
reverse bias p-n
junction
p-n-p or p-n-i-p, or p-n
metal or metal-n-metal
forward bias p-n
junction
Harmonics - Less Strong Less
Ruggedness Yes Yes Yes Yes
Size Small Small Small Small
Application Oscillator Amplifier, Oscillator Oscillator Local Oscillator
Comparison of GUNN, IMPATT, TRAPATT,
BARITT
20. 20
Impatt diode Trapatt diode Baritt diode
In the year 1958 WT read discovered concept of avalanche diode. From this, it has been discovered that
diode can produce negative resistance at the microwave frequencies. This is achieved by using carrier
impact ionisation and drift in the high field intensity region of the reverse biased semiconductor region. From
this concept, three diodes impatt diode, trapatt diode and baritt diode have been found.
Full name
Impact ionisation Avalanche Transit
Time
Trapped Plasma Avalanche Triggered
Transit
Barrier Injection Transit
Time
Develoed by RL Johnston in the year 1965 HJ Prager in the year 1967
D J Coleman in the year
1971
Operating Frequency
range 4GHz to 200GHz 1 to 10GHz 4GHz to 8GHz
Principle of operation Avalanche multiplication Plasma avalanche Thermionic emission
Output power 1Watt CW and > 400Watt pulsed 250 Watt at 3GHz , 550Watt at 1GHz just few milliwatts
Efficiency
3% CW and 60% pulsed below 1GHz,
more efficient and more powerful than
gunn diode type 35% at 3GHz and 60% pulsed at 1GHz
5% (low frequency) , 20%
( high frequency)
Noise Figure 30dB (worse than Gunn diode)
Very high NF of the order of about
60dB low NF about 15dB
Advantages
• This microwave diode has high power
capability compare to other diodes.
• Output is reliable compare to other
diodes
• Higher efficiency than impatt
• very low power dissipation
Less noisy than impatt
diodes • NF of 15dB at C
band using baritt amplifier
Disadvantages
• High noise figure
• high operating current
• high spurious AM/FM noise
• Not suitable for CW operation due to
high power densities
• high NF of about 60dB
• upper frequency is limited to below
millimeter band
• Narrow bandwidth
• limited few mWatt of
power output
Applications
• Voltage controlled Impatt oscillators
• low power radar system
• injection locked amplifiers
• cavity stabilized impatt diode
oscillators
• used in microwave beacons
• instrument landing systems
• LO in radar
• Mixer
• oscillator
• small signal amplifier
Comparison of IMPATT, TRAPATT,
BARITT
21. GUNN diode
21
GUNN diode
The Gunn diode is not like a typical PN junction diode. Rather than having both p-type and n-type
semiconductor,itonlyutilisesn-typesemiconductorwhereelectronsarethemajoritycarriers.
Whenavoltageisplacedacrossthedevice,mostofthevoltageappears
across the inner active region. As this is particularly thin this means
thatthevoltagegradientthatexistsinthisregionisexceedinglyhigh.
ThedeviceexhibitsanegativeresistanceregiononitsV/Icurveasseen
below. This negative resistance area enables the Gunn diode to amplify
signals. This can be used both in amplifiers and oscillators. However
Gunndiodeoscillatorsarethemostcommonlyfound.
27. TRAPATT diode (principle of operation)
27
AT the instant of time at point A, the diode
current is turned on.
Since the charge carriers present are those
caused by thermal generation, the diode
initially charge up like a linear capacitor,
driving the magnitude of the electric field
above the breakdown voltage.
When sufficient number of carrier is
generated, the particle current exceeds the
external current and the electric field is
depressed throughout the depletion region,
causing the voltage to decrease. This portion
of the cycle is known by the curve
from point B to point C.
During this time interval the electric field is
sufficiently large for the avalanche to
continue and a dense plasma of electrons
and holes is created. The voltage decrease
to D.
The holes produced in the avalanche rapidly
reach the p+ contact taking no part in
process but the electrons are released into N
region where they do not combine with
either doner or holes.
Principle of operation : Plasma avalanche
28. 28
The electron drift at their maximum velocity
across the N region and current continuous to
flow in the external circuit which they are in
transit.
When this current pulse actually arrives at the
cathode terminal, the ac voltage is at its
negative peak and the second delay of 90. (90
degree) has taken place. This time depends
upon the velocity and the thickness of the
highly doped N+ layer.
A large time is required to remove the plasma
because total plasma charge is large compared
to the charge per unit time in the external
current.
At point E plasma is removed.
As the residual charge is removed, the voltage
increases from point E to point F . At point
F all the charge generated internally has been
removed.
From point F to G the diode charged up again
like a fixed capacitor.
At point G the diode current goes 0 for half
period and the voltage remains constant VA
until the current comes back on and the cycle
repeats.
TRAPATT diode (principle of operation)
Principle of operation : Plasma avalanche
32. Application of TRAPATT diode
32
Instrument landing system
How the localiser and glide path work together to provide vertical and
horizontal guidance to pilots
Shows the different decision heights that apply to different approaches.
• used in microwave beacons
• instrument landing systems
• LO in radar
33. Application of IMPATT
33
• Voltage controlled Impatt oscillators
• low power radar system
• injection locked amplifiers
• cavity stabilized impatt diode oscillators
34. Application of Gunn Diode
34
Radar Gun is used to measure the speed of moving vehicle & cricket ball etc…
