Micro chip patch antenna

MICRO STRIP PATCH ANTENNA

AND ITS APPLICATIONS

What is an antenna???

• Antenna is an electrical device which converts electrical power into radio waves and vice versa

• It is usually used with a radio transmitter .

• Different types of antennas are

1)Microstrip antenna

2)Conventional micro wave antennas

Microstrip Antenna

• Microstrip antennas consists of a radiating patch on one side of dielectric substrate (Єr≤10), which has a ground plane on other side.

• The micro strip antennas are the present day antenna designer’s choice.

• A micro strip antenna is characterized by its Length, Width, Input impedance, and Gain and radiation patterns

Common shapes of micro strip patch elements

TYPES OF MICRO STRIP ANTENNA

Micro strip patch antenna

• Micro strip antennas consists of aradiating patch on one side of dielectricsubstrate (Єr≤10), which has a groundplane on other side.

• The patch is generally made ofconducting material such as copper orgold and can take any possible shape.

• The radiating patch and the feed linesare usually photo etched on thedielectric substrate.

Disadvantages

• Lightweight construction

• Versatility of possible geometries

• Low cost manufacturing

• Simplicity of structure

Advantages

• Narrow bandwidth, typically 3%

• Have low directivity /

broad beam width

• Low radiating power

efficiency

.

Radiation Patterns MICROSTRIP PATCH ANTENNA

RADIATION PATTERNS

Rectangular Patch Antenna

• For a rectangular patch, the length L of the patch is usually 0.3333λo< L < 0.5 λo, where λo is the free-space wavelength. The patch is selected to be very thin such that t << λo(where t is the patch thickness).

• The height h of the dielectric substrate is usually 0.003λo≤h≤0.05 λo.

• The dielectric constant of the substrate (εr) is typically in the range 2.2 ≤εr≤ 12.

Feed line techniques

• A feed line is radiate by direct or indirect contact.

• There are many different techniques of feeding and four most popular techniques are

1. coaxial probe feed

2. micro strip line

3. aperture coupling and

4. proximity coupling

coaxial probe feed

• Coaxial probe feeding is feeding method inwhich that the inner conductor of thecoaxial is attached to the radiation patch ofthe antenna while the outer conductor isconnected to the ground plane

• Advantages of coaxial feeding is easy offabrication, easy to impedance match, lowspurious radiation

• disadvantages is narrow bandwidth,Difficult to model specially for thicksubstrate.

Proximity Coupled Feed

• This type of feed technique is also called as the electromagnetic coupling scheme.

• two dielectric substrates are used such that the feed line is between the two substrates and the radiating patch is on top of the upper substrate.

• The main advantage of this feed technique is that it provides very high bandwidth

• the disadvantage of this method is that as substrate thickness increases

Microstrip Line Feed

• In this type of feed technique, a conductingstrip is connected directly to the edge of theMicrostrip patch

• The conducting strip is smaller in width ascompared to the patch and this kind of feedarrangement has the advantage that the feedcan be etched on the same substrate toprovide a planar structure

• The purpose of the inset cut in the patch isto match the impedance of the feed line tothe patch without the need for anyadditional matching element.

Real World Examples_______________

• GPS Antennas

• Wireless LAN

• Missiles

• Rockets

Mobile and satellite communication

• Mobile communication requiressmall low cost ,low profile antennas

• Rectangular micro strip patchantenna meets all requirementsand various types of micro stripantennas have been designed touse in mobile communication

• In case of satellite communicationCircularly polarized patterns arerequired and can be realized usingeither circular or square patch

Internal Integrated Microstrip Antenna

External Retractable Antenna

Internal Integrated Antenna

Real World Examples cont…_________

• Used at Johnson Space Center to measure pre-launch ice buildup on orbiter

• Measure thickness of ice on roadway

• Measure thickness of uncut coal in a mine

Microstrip Antenna as a sensor

conclusion

• A microstrip patch GPS antenna thinner and cheaper than the thick ceramic patch antenna usually employed for automotive applications was proposed and analyzed.

• This configuration allows to easily integrate a low noise amplifier on the substrate used for the feeding circuitry.

Return loss

• Return Loss:

• Return loss is the difference, in dB, between forward and reflected power measured at any given point in an RF system and, like SWR, does not vary with the power level at which it is measured. A return loss of -30dB is obtained at the desired frequency.

Input Impedance

• An antenna's impedance relates the voltage to the current at the input to the antenna. The magnitude of 0.82 is obtained from the input impedance smith chart.

REFERENCES

• [1] 4nec. http://home.ict.nl/ arivoors/.

• [2] The antenna tutorial website. http://www.antenna-theory.com/

• antennas.

• [3] Supernec. http://www.supernec.com/.

ANY QUIRES?