SUMMER TRAINING WORK ON ANTENNA DESIGN & VHDL

Submitted By

Vipin Yadav

2K13-MRCE-MT-ECE-015

INDEX

• Antenna Introduction• HFSS Software• Patch shapes and substrate • Design Specifications & Feeding techniques• Simulation results• VHDL & Its Coding Styles• Types of Modelling • Hierarchy & statements in VHDL

INTRODUCTION• An antenna is an electrical device which converts

electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver.

• In transmission, a radio transmitter applies an oscillating radio frequency electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves).

WHY ANTENNAS ?

• Need of antenna arisen when two person wanted to communicate between them when separated by some distance and wired communication is not possible.

• Antennas are required by any radio receiver or transmitter to couple its electrical connection to the electromagnetic field.

• Radio waves are electromagnetic waves which carry signals through the air (or through space) at the speed of light with almost no transmission loss.

HFSS SOFTWARE• HFSS (high frequency structural simulator) is a high-

performance full-wave electromagnetic(EM) field simulator for arbitrary 3D volumetric passive device modelling that takes advantage of the familiar Microsoft Windows graphical user interface.

• It integrates simulation, visualization, solid modelling, and automation in an easy-to-learn environment where solutions to 3D EM problem are quickly and accurately obtained.

• Ansoft HFSS employs the Finite Element Method(FEM), adaptive meshing, and brilliant graphics to give unparalleled performance and insight to all of your 3D EM problems.

Microstrip AntennaIn its most basic form, a Microstrip patch antenna consists of a radiating patch on oneside of a dielectric substrate which has a ground plane on the other side

Structure of a Microstrip Patch Antenna

For good antenna performance, a thick dielectric substrate having a low dielectric constant is desirable since this provides better efficiency, larger bandwidth and better radiation .

In genaral Micro strip antennas are also known as

“ PRINTED ANTENNAS ”. These are mostly used at microwave

frequencies. Because the size of the antenna is directly

tied the wavelength at the resonant frequency.

Micro strip patch antenna or patch antenna is a narrowband wide-beam antenna.

Patch Shapes Are:

(a) Single radiating patches

(b) Single slot radiator

Substrates are:The most commonly used substrates are,

1) Honey comb(dielectric constant=1.07)

2)Duroid(dielectric constant=2.32)

3)Quartz(dielectric constant=3.8)

4)Alumina(dielectric constant=10) A thicker substrate will increase the radiation

power , reduce conductor loss and improve Band width.

Feeding Techniques: Coaxial feed Microstrip feed Proximity coupled microstrip feed Aperture coupled microstrip feed Coplanar wave guide Line Feed

1-Microstrip Line Feed :

In this type of feed technique, a conducting strip is connected directly to the edge of themicrostrip patch.

This kind of feed arrangement has the advantage that the feed can be etched on thesame substrate to provide a planar structure.

2-Coaxial Feed :-

The Coaxial feed or probe feed is a very common technique used for feeding Microstrippatch antennas.

Probe fed Rectangular Microstrip Patch Antenna from top

Probe fed Rectangular Microstrip Patch Antenna from side view

The main advantage of this type of feeding scheme is that the feed can be placed at anydesired location inside the patch in order to match with its input impedance.

This feed method is easy to fabricate and has low spurious radiation.However, its major disadvantage is that itCoaxial Ground Plane Connector SubstratePatch provides narrow bandwidth and is difficult to model since a hole has to be drilled in the substrate . and the connector protrudes outside the ground plane, thus not making it completely planar for thick substrates .

3-Aperture Coupled Feed

In this type of feed technique, the radiating patch and the microstrip feed line are separated by the ground plane .

Coupling between the patch and the feedline is made through a slot or an aperture in the ground plane.

Aperture-coupled feedThe coupling aperture is usually centered under the patch, leading to lower cross polarization due to symmetry of the configuration.

The amount of coupling from the feed line to the patch is determined by the shape, size and location of the aperture.

3.2 Project specifications Project Specs Operating Frequency : 1.575 GHz Input Impedance: 50 Ohm VSWR: 2:1 @ 1.575 GHz Polarization: RHCP Bandwidth: 3.8% (~60 MHz) Substrate RT/Duroid (Rogers Corp.) e= 2.22 h= 125 mils tan d = 0.001

Simulation Results of a 1.575 GHz GPS Receiver Antenna Design

Return Loss

VSWR PLOT

2 D PATTERN

What does HDL stand for?

HDL is short for Hardware Description Language

(VHDL – VHSIC Hardware Description Language) (Very High Speed Integrated Circuit)

VHDL

Basic Form of VHDL Code

• Every VHDL design description consists of at least one entity / architecture pair, or one entity with multiple architectures.• The entity section is used to declare I/O ports of the circuit. The architecture portion describes the circuit’s behavior.• A behavioral model is similar to a “black box”. • Standardized design libraries are included before entity declaration.

Standard Libraries• Include library ieee; before entity declaration.• ieee.std_logic_1164 defines a standard for designers

to use in describing interconnection data types used in VHDL modeling.

• ieee.std_logic_arith provides a set of arithmetic, conversion, comparison functions for signed, unsigned, std_ulogic, std_logic, std_logic_vector.

• Ieee.std_logic_unsigned provides a set of unsigned arithmetic, conversion, and comparison functions for std_logic_vector.

Entity Declaration

• An entity declaration describes the interface of the component.• PORT clause indicates input and output ports.• An entity can be thought of as a symbol for a component.

Port Declaration

• PORT declaration establishes the interface of the object to the outside world.

• Three parts of the PORT declaration• Name

• Any identifier that is not a reserved word.

• Mode• In, Out, Inout, Buffer

• Data type• Any declared or predefined datatype.

• Sample PORT declaration syntax:

Architecture Declaration

• Architecture declarations describe the operation of the component.

• Many architectures may exist for one entity, but only one may be active at a time.

• An architecture is similar to a schematic of the component.

Modeling Styles

• There are three modeling styles:

• Behavioral (Sequential)

• Data flow

• Structural

VHDL Hierarchy

Sequential vs Concurrent Statements

• VHDL provides two different types of execution: sequential and concurrent.

• Different types of execution are useful for modeling of real hardware.• Supports various levels of abstraction.

• Sequential statements view hardware from a “programmer” approach.

• Concurrent statements are order-independent and asynchronous.

Behavioural Style

Data flow Style

Structural Style