Antenna in wireless communication system Essay Example

Minor Lobe

Any lobe other than the main lobe is considered a minor lobe.

Side Lobe

A side lobe refers to a lobe that has less radiation compared to the main lobe.

Back Lobe

The back lobe represents a l obe that occurs at an angle of 180° relative to the main l obe.

Radiation Beamwidth

Beamwidth indicates the angular separation between two points on opposite sides of the pattern maximum that cannot be distinguished from each other. The half power beamwidth (HPBW) denotes when the field strength reduces to 0.707 times its maximum value. The beam width between the first nulls is known as First-Null Beamwidth (FNBW).

Polarization:
Polarization refers to directionality in which electromagnetic waves oscillate. It specifies whether electric fields are vertically or horizontally oriented or linearly polarized or circularly polarized.
Directivity and Polarization
Directivity is the ratio of maximum power density to average power density. Mathematically, it can be calculated as D = P(soap) / P(avg), where P represents power. To assess directivity, we compare the maximum power density of a tested aerial (AUT) with that of a known directivity reference antenna, like a short dipole. The calculation for determining directivity (G) is G = Pmax(AUT) / Pmax(Ref.antenna) x G(Ref.antenna).
Polarization refers to the orientation of electromagnetic waves in free space and denotes the direction and relative magnitude of the electric field vector. Vertically polarized antennas operate on lower frequencies, while horizontally polarized antennas operate on higher frequencies. Polarization can be classified into three types: linear polarization, circular polarization, and elliptical polarization.
Linear polarization occurs when the E-field (or H-field) vector aligns along a straight line. It can further be subdivided into horizontal polarization or vertical polarization

based on whether the wave propagates along the x-axis or not. A wave with E1 directed along the x-axis can be represented as a vertically polarized wave propagating along the y-axis. This vertically polarized wave is described by E2, which is oriented along the y-axis.Circular polarization occurs when both components (E1 and E2) have equal magnitudes, resulting in a wave that propagates perpendicularly and horizontally with a 90-degree phase difference. Mathematically, circular polarization can be expressed as such. The E-field of a traveling wave in the z-direction is known as elliptical polarization, consisting of x and y-components with a phase difference "?". This causes the wave to be elliptically polarized. Beam efficiency can be determined by combining the main lobe and minor lobe to find the total beam area of an antenna. The ratio between the main lobe's beam area and the entire beam area represents its beam efficiency, which also applies to the minor lobe's beam area. This ratio is referred to as the stray factor as well. Input Impedance refers to either the resistance at an antenna's terminals or the ratio of electric and magnetic field components at a specific point. It is mathematically represented by ZA = RA +? XA, where RA may vary depending on the antenna being used. Bandwidth refers to the range of frequencies surrounding an antenna's center frequency on which it operates. Having a high bandwidth is advantageous, especially for broadband antennas where bandwidth is expressed as the ratio between upper cutoff and lower cutoff frequenciesMicrostrip patch antennas are widely used in military applications, such as spaceships, aircrafts, missiles, due to their performance, cost-effectiveness, streamlined design and ease

of installation. Nowadays, these antennas are also utilized in wireless communication systems that have similar requirements. These compact antennas can conform to both planar and non-planar surfaces, making them versatile. Through printed circuit technology, microstrip patch antennas can be constructed at a low cost. They possess flexible characteristics including polarization, resonant frequency, resistance and radiation pattern. By attaching a substrate onto a land plane and placing a radiating spot on it, bandwidth enhancement can be achieved. The shape and size of the radiating spot can vary from rectangular to square or triangular forms with rectangular spots typically measuring between ?0/3 and ?0/2 in length.
Different materials can serve as substrates for these antennas; however they must have an insulator constant within the range of 2.2 ??r to 12. Thick substrates with lower insulator constants are preferred for achieving high performance levels resulting in larger bandwidths, improved efficiency and loosely bounded fields; although this comes at the expense of larger component sizes.The text discusses the need for a balance between antenna and circuit design in microwave circuitry. It explains that thin substrates with higher insulator constants are required, but they have lower bandwidths and increased losses. The expressions for acquiring the length (L) and width (W) of a rectangular spot on a Microstrip aerial are provided. Various feeding techniques for Microstrip aerials are mentioned, including coaxial probe feed, Microstrip transmission line feed, aperture coupled feed, and proximity coupled feed. The Microstrip line feeding technique involves placing a strip smaller than the radiating spot at one border according to aerial design. This technique requires specific dimensions to achieve an input impedance of 50?. However, increasing substrate thickness leads

to increased feed radiations, which limits bandwidth and is undesirable. An image depicting the Microstrip line feed is shown below.

The second technique described is called Aperture Coupled Feed, which uses two substrates with a land plane sandwiched in between.The first technique is the Microstrip provender line, where a slot over the land plane couples it to the radiating spot. The top substrate has a lower dielectric constant while the bottom substrate has a higher dielectric constant.

The second technique is Coaxial Probe Feed which uses two coaxial conductors. The inner conductor connects to the radiating spot through the dielectric substrate, and the outer conductor connects to the land plane. However, antennas with thick insulator substrates may face challenges in achieving electric resistance matching due to limitations on the size of the coaxial probe. Increasing its size can lead to undesired inductance. To address this issue, a series of capacitances can be used and different feeding places can be explored until desired results are achieved.

The figure below depicts how coaxial probe feed works:

The equivalent circuit for coaxial probe feed is shown in another figure below:

Another technique discussed here is Proximity Coupled Feed, which provides the highest bandwidth among all four techniques mentioned – up to 13%. This technique offers easy design by placing a microstrip line feed between two substrates at a specific spot on the upper substrate.However, the implementation of this method may be difficult as adjustments to the width-to-line ratio are necessary in order to achieve electric resistance matching. The figure below shows the propinquity yoke technique and the equivalent circuit for Proximity coupled provender.

Microstrip spot aerials have several advantages, including

their lightweight, compact and low-profile design. They also have the ability to support different types of polarization and can operate at various frequencies. When mounted on a rigid surface, they have potential durability and do not require pit backup. Additionally, they can be integrated on a microwave integrated circuit.

There are multiple feeding techniques available for microstrip spot aerials, and they can operate within a frequency range from 100 MHz to 100 GHz. However, there are also disadvantages such as low efficiency, limited bandwidth, and power handling capacity. Surface wave excitement can lead to large ohmic losses, and high-performance arrays require complex feed constructions. Achieving polarization purity can also be challenging.

WiMAX Technology Introduction: The demand for broadband services is rapidly increasing. Traditional wired technologies like cable modems, DSL (digital subscriber line), Ethernet, and fiber optic have been used for high-speed broadband access.The construction and maintenance of wired networks in rural and remote areas pose challenges and are expensive. However, broadband wireless access (BWA) technology, such as WiMAX, provides a flexible and cost-effective solution to overcome these obstacles. WiMAX is a popular BWA technology that offers high-speed broadband radio access for wireless metropolitan area networks (WMANs). Also known as the IEEE 802.16 air interface standard, WiMAX is designed for WMANs and supports fixed, portable, and mobile broadband access. It promotes interoperability and coexistence of BWA systems from different manufacturers in a cost-effective manner. Unlike complex wired networks, a WiMAX system comprises only two parts: the WiMAX base station (BS) and the WiMAX subscriber station (SS), making it easy to build at a low cost. Additionally, WiMAX is considered the next step in mobile technology development.

WiMAX

Worldwide Interoperability for

Microwave Access (WiMAX) is a telecommunication technology that enables wireless data transmission using various modes ranging from point-to-multipoint links to portable and fully mobile internet access. The advancements in radio communication offered by WiMAX (802.16e) technology allow for high throughput broadband connections over long distances.The WiMAX Forum created the name "WiMAX" to promote interoperability and describe it as an alternative for last mile broadband access, competing with cable and DSL. The WiMAX standards ensure compatibility and interoperability for broadband systems, with two variations currently available: IEEE 802.16-2004 for fixed radio applications and IEEE 802.16e for mobile radio applications. The 802.16-2004 standard is optimized for both fixed and mobile access, offering support for multiple services and improvements over previous versions (IEEE 802.16, 802.16a, and 802.16c). It operates on frequency sets ranging from 10-66GHz to 2-11GHz, with a channel bandwidth between 1.25 and 28 MHz, providing speeds of up to75 Mbps within a distance of up to30 miles.The goal is to globally deploy affordable multivendor BWA products that are compatible with wired systems while increasing competitiveness. The IEEE 802.16e Standard aims to provide portability and mobility to wireless devices in mobile radio applications by accommodating channel bandwidths ranging from 1.25 to 20 MHz. It supports a maximum data rate of 15 Mbps within a distance of 1-3 miles. The specific details can be found in the table below:

Spectrum For WiMAX Network

To deploy WiMAX services, spectrum allocation is crucial as it determines parameters such as usable bandwidths, transmission power, and coverage characteristics based on frequency bands like 2.4 GHz, 3.5 GHz or 5 GHz. The WiMAX Forum has released three accredited spectrum profiles (2.3 GHz, 2.5

GHz, and 3.5 GHz) to reduce costs. The unaccredited profile includes the use of 5 GHz but is unlikely to be utilized by telecommunication companies.

In the USA, the largest available section for WiMAX operates at around 2.5 GHz while Asian countries like India and Indonesia utilize different frequencies such as 2.5 GHz and 3.

WiMAX Antenna: Compact, Broadband, and Efficient

With advancements in radio communication technology, WiMAX (Worldwide Interoperability for Microwave Access) (802.16e) has successfully enhanced the world of wireless communication. This technology allows for high-speed broadband connections over long distances, reaching up to 50 kilometers with impressive data rates of up to 72 Mbps. WiMAX operates at different frequency ranges depending on its variant; WMAN portable (WiMAX 802.11e) operates within a range of 2-6 GHz, while WMAN fixed (WiMAX 802:11d) functions at an operating frequency range of eleven gigahertz.

However, current WiMAX systems typically operate at frequencies around approximately 2:4GHz ,3:5GHz,and five point two gigahertz. To effectively work with these frequencies, it is recommended to utilize various types of antennas that can ensure efficient operation in wireless communication systems. The demand for compact and lightweight designs has led to the popularity of microstrip antennas which possess the ability to conform easily to mounting hosts.

Microstrip antennas offer versatile design options such as meandering land configurations or spot configurations, both capable of incorporating embedded slots that provide different slot forms for enhancing microstrip aerial design functionality. By combining two slots together, dual-frequency spot operations become achievable.The aerial's radiating component is a rectangular spot with a V-slot that resonates at a lower frequency, effectively increasing its electrical length compared to a conventional rectangular spot. This design has been previously used

for WLAN aerials with proximity coupled and coaxial probe feeding methods. Figure 5.2 shows the geometry and configuration of an altered antenna design compatible with multiple standards like WiMAX, Wi-Fi, BLUETOOTH, and CDMA 2000. This is achieved by using a single transmission line.

The proposed antenna has a rectangular shape and is placed on a substrate with a thickness of 1.6mm and dielectric constant (?r) of 4.7 to operate within multiple bands in the WLAN frequency range. The antenna includes two truncated corners and a V-shaped slot whose dimensions are shown in Figure 5.3.

Instead of using the proximity coupled feeding method, the antenna is fed through a 50? transmission line (3mm wide) connected at one end of the feeding line.

Simulations were conducted on the antenna design using Ansoft HFSS, which is user-friendly software for high-frequency design. These simulations provided accurate results regarding the radiation pattern and other related parameters of the antenna.

Initially, we designed and simulated a microstrip patch antenna to demonstrate how changes in its dimensions affect its performance.The length of the radiating patch affected its power, while changes in width influenced the frequency of radiation. The resulting return loss plot showed resonant points at 0.4GHz, 2.4GHz, 3.4GHz, 3.9GHz, 4.4GHz, and 5.1GHz with corresponding return loss values of -21.65dB,-24 .68dB,-27 .69dB,-19 .42dB,-21 .37dB,and-39 .96 dB respectively.

Below is a table with details of these frequencies along with their corresponding return losses and percentage bandwidths:

Frequency (GHz) | Return Loss (dB) | Percentage Bandwidth
---|---|---
0 .4 | -21 .65 | TBD
2 .4 | -24 .68 | TBD
3 .4 |-27 .69|TBD
3 .9 |-19 .42|TBD
4 .4|-21 ,37|TBD
5 ,1|-39 ,96|TBD

From this table, it can be observed that the minimum return loss is

-39 dB.

The figures below depict the radiation patterns of a simple patch antenna. Simulations were then performed on a V-shaped slotted patch antenna to obtain return loss and percentage bandwidth data.

Another figure shows the truncation of corners in the V-shaped slotted antennas.

Using HFSS, we obtained seven sets of data for the corner truncated V-slotted patch antenna at different frequencies: 0.3GHz, 2.4GHz, 3.4GHz, 3.9GHz, 4.3GHz, 4.6GHz, and 5.2GHz.

These sets are applicable to CDMA2000/1x EV-DO (3G), Bluetooth (802.15.x), Wi-Fi (802.xx b/g), and WIMAX (802.16e) standards.

For the first set at a frequency of 0.3GHz, we achieved a return loss of -21.38dB with a percentage bandwidth of 136.84%.At a frequency of 2.GHz, the second set had a return loss of -27.39 dB with a percentage bandwidth of 4.I7%. The third set had a return loss of -30.99 dubnium at J.A GHz with a percentage bandwidth of 7.Jl%. At a frequency o?J.g GHz, the fourth set had a return loss or-20.60 dubnium witha percentage bandwidthof7.a5%. Forthe fifth setat afrequencyof A.jg Hz, weobtainedareturnlossof- j.iZdubniumwithapercentag eb andswidthoffi.TS %. The sixth set hasa return lossof -13 .43 dubnium at 4 .6 GHz , witha percentage bandwidthof3 .57 % .The seventh set hasa return lossof-17.86 dubniumat5.2 GH z ,w itha per centag e ban dwid thof10.33%.
Below is the graph displaying the S11 parameters for the proposed antenna.The minimum return loss according to the table i s -30.99 dubnium at 3.4GHz.The figures below illustrate the radiation patterns of the proposed antenna.
The fabrication process involves using various materials such as a 1.6mm FR4 sheet coated with Cu on both sides, FeCl3 powder, substrate sheet, cutter,and boiled water.The procedure is as follows:
1.Cut a rectangular piece of

substrate to desired dimensions and antenna design using acutter.
2.Transferthe antennaspotprintsontothe protruding sheet and cut alongthespotdimensions.
3.Pastethelodgingspotdesignontoonesideofthesubstratepiece.
4.Excessively covertheothersideofthesubstratepiecewithaprotrudingsheet.
5.Boil atleastonecupofwaterandmixferrouschlorideinit.Place the substrate piece covered by lodging spot design into the solution. After some time, Cu will disappear from all areas of the substrate sheet except for those covered by the protruding sheet. Remove the sheet from the solution and rub it. Take offthe lodging sheet fromthe substratesheet. Solderthe SMA connection attheterminalofthetransmission line image ontothesubstratesheet.
The fabricated aerial operates on WiMAX, CDMA 2000/1x EV-DO (3G), Bluetooth (802.15.), and Wi-Fi (80211 b/g) frequency setsWiMAX supports various applications including low-cost cellular data communication and different types of data transfer.It also facilitates audio, picture on demand, television, videoconferencing, and nomadic information exchange.WiMAX plays a crucial role in military operations, enhancing preparation and war games by facilitating efficient information exchange between different locations.This is achieved through the use of mobile aerials attached to vehicles, which provide real-time data for tactical defense operations.Furthermore, WiMAX allows commanding officers to deliver orders and directions regardless of distance.Additionally, WiMAX supports voice over IP (VoIP) services and meets the requirements of wireless IP networks,making it a strong competitor among other radio broadband access technologies.In medical applications,WiMAX enables e-health services such as remote patient monitoring in emergency situations.Doctors can use WiMAX to connect their computer equipment with patients' devices for seamless communication. Toll plaza roadway equipment technicians can utilize IEEE 802.11b wireless technology, which is suitable for meeting distance and operational requirements. Bluetooth offers an application called Automatic Message Delivery that enables users to compose emails on a portable personal computer while on an aircraft. These messages are queued and sent instantly once the aircraft lands and the mobile phone

is turned on.

Nokia utilizes CDMA 2000 web for IP Multimedia Applications. Various feeding methods can be employed to enhance or modify the efficiency of microstrip spot aerials, ensuring compatibility with multiple bands such as WiMAX, Wi-Fi, BLUETOOTH, and CDMA 2000 standards. Adding slots in a spot causes it to resonate at a lower frequency compared to a rectangular spot of the same size and increases its effective electrical length.

Future work aims to enhance the aerial's bandwidth through techniques like increasing substrate thickness, using meandered land plane or slotted land plane, incorporating suitable slots in the radiating spot, utilizing chip-resistor burden, or employing stacked shorted spots.

Appendix A
How To Use Ansoft HFSS
The following tutorial will guide students on creating, simulating, and measuring the response of standard stripline construction.
The HFSS Interface consists of several windows and tabs. The main interface is depicted in the figure below. The 3D Modeler Window allows users to create construction geometry for the model. It includes Grid and history tree components, as shown in the above figure. The history tree keeps track of actions performed within the model spectator area and offers alternative object selection methods. An expanded view of the history tree is shown in a separate figure.

The Project Manager and Project Tree window contain all opened HFSS projects. Each project displays details about geometric models, material assignments, boundary conditions, post-processing information, and field solutions. Another expanded view is provided for the Project Manager window.

The Properties Window has two sub-tabs: attribute tab and bid check tab. The attribute tab provides information about display properties and materials of objects, while the bid check tab contains information about selected actions in the history tree

for creating new objects or making alterations to existing ones.

During simulation advancement, the Advancement Window is used to display simulation position and running processes. The Message Director window displays any messages associated with tasks such as error messages and warnings.

To ensure efficient and accurate operations when using HFSS for the first time, follow these steps:
1.Go to tools menu > options > general optionsIn this window, choose the default units and set the default length to mm. Click "Okay". Next, go to the tools menu, then options, and HFSS options. This will open a new window where you can select the "include ferrite materials" option. Finally, press the convergence button.