IMPATT Stands for IMP act ionization A valanche T ransitT ime

Pn junction diode is reverse biased
Avalanche multiplication of electrons and holes occur
Negative resistance is based upon avalanche multiplication and transit-time effect of carriers
This exhibits negative resistance characteristics in microwave frequency range.
Device based on this principal is called the
IMPATT DIODE

EQUIVALENT CIRCUIT FOR IMPATT DIODE:
Where,
Where,

OPERATION OF IMPATT DIODE:

Voltage and Current Vs Time:

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IMPATT is designed for high power applications whereas, a diode burns (heat-up) at high power.
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IMPATT is operated at reverse bias whereas a diode is normally operated at forward bias because at reverse bias there is high voltage drop.

1. Operate at frequencies between about 3 and 100 GHz or more.
2. High power capability.
1. Major drawback of using IMPATT diodes is the high level of phase noise they generate.
2. The noise figure for IMPATT is 30dB .
3. Tuning range is not as good as Gunn diodes.

1. MICROWAVE GENERATOR
2. MODULATED OUTPUT OSCILLATOR
3. RECEIVER LOCAL OSCILLATOR
4. PARAMETRIC AMPLIFIER (par amps)
5. INTRUSION ALARM NETWORK
6. FM TELECOMMMUNICATION TRANSMITTERS
7. CW DOPPLER RADAR TRANSMITTER.

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Very high frequency stability
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High output power
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Low phase noise
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Fine spectrum
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Precision frequency adjustment
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Weak temperature dependence
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Compact, low cost

TRApped-Plasma Avalanche Trigged Transit Diode

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It is derived from IMPATT Diode.
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Silicon or Gallium Arsenide is used for fabricating TRAPATT Diode.
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TRAPATT Diode can be constructed either by p+ -n-n+ or n+-p-p+.

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A square pulse is used to excite TRAPATT diode.

AB – Charging of junction capacitance
BC – Electron and hole plasma formation by depressed field
DE – Plasma extraction
EF – Residual extraction
FG – Charging of diode
GA – Constant voltage after full charging

1. The current density is given by, 2. Electric field is given by,
Where,
3. Avalanche zone velocity is given by,
Where,

1. It is a high efficiency diode oscillator .
2. Its oscillations depend on delay in current caused by avalanche process.
3. The diode diameter is about 50 mm for CW operations and is about 750 mm at lower frequency for high peak power application.
4. It can be operated over a range of 400MHz to 12GHz.
5. Its has an efficiency of 20% - 40%.

1. Its efficiency is relatively high.
2. It can be used over a frequency range of a few hundred MHz to several GHz.
1. It has high noise figure.
2. Its use at upper microwave frequencies is limited .
3. It generate strong harmonics due to the short duration of current pulse.

It is used in
• in pulse radar as local oscillator.
• in radio altimeter.
• air borne and marine radars.
• in microwave beacons and landing system.
• in low power Doppler radars.

The Signal Processing and Instrumentation Section (SPIS) provides electrical, electronic, electro-optical, and computer engineering support to clinical and biomedical research projects involving advanced real-time signal transduction, signal processing, and control.
FIG: A JARVIK-7 artificial heart, an example of a biomedical engineering

1. APPLICATION IN STERILIZING MEDICAL EQUIPMENTS
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Sterilization (or sterilisation ) is a term referring to any process that eliminates
(removes) or kills all forms of life, including transmissible agents (such as fungi, bacteria, viruses, spore forms, etc.) present on a surface, contained in a fluid, in medication, or in a compound such as biological culture media.
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Sterilization can be achieved by applying the proper combinations of heat, chemicals, irradiation, high pressure, and filtration.
FIG: Sterilizing surgical instruments

HOW MICROWAVES ARE USED FOR
STERILIZING PROCESS?
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Low-cost technology to kill harmful bacteria has been developed at
Glyndŵr University in Wrexham.
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Researchers found that by attaching a vacuum vessel to a microwave oven, atomic oxygen and ozone - both aggressive gases - can be generated.
• The modified microwave used by the team cost less than £2,000, compared to £70,000 for conventional systems.
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The new method, developed by a team led by senior research scientist Dr
Andy Wright, provides a chemical-free solution to killing harmful bacteria on medical tools used in GP, dentist and veterinary surgeries.

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Refers to the microscopic examination of tissue in order to study the manifestations of disease.
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Specifically, in clinical medicine, histopathology refers to the examination of a biopsy or surgical specimen by a pathologist, after the specimen has been processed and histological sections have been placed onto glass slides.
FIG: Micrograph showing contraction band necrosis, a histopathologic finding of myocardial infarction (heart attack)

HOW MICROWAVES ARE USED IN
HISTOPATHALOGY ?
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Microwave accelerated procedures are useful at every step of sample preparation for microscopy by speeding up reaction process and saving time.
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Even more important , microwave procedures improves the retention of soluble Antigen immuno reactivity better than conventional methods.
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In short, microwave accelerated techniques can be used to improve the efficiency of variety of histopathology laboratory procedures, such as fixation, decalcification , processing of specimens for paraffin wax or resin embedding and staining.

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Two types of microwave devices are being used in histopathology laboratory setting :
1. Microwave instruments specifically designed and certified as medical devices
2. Commercial grade microwave units modified for lab/clinics
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Laboratory microwave devices are designed with exhaust fans and safety features to protect microwave devices.

Presented By:
GROUP 4
Roll No:
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