Antenna – Page 2

February 15, 2012August 9, 2013Antennas

Some Commonly Used Antenna Terminology

Antenna Pattern Antenna Pattern or Radiation Pattern is a three dimensional description of how the antenna radiates energy in to the space around it. All practical antennas are directional i.e. they radiate more energy in certain directions and lesser energy in other directions. Although the Radiation Pattern is a three dimensional quantity it can be described in two perpendicular planes known as the principal planes. Usually one of these planes is horizontal (azimuth plane) and the other is vertical (elevation plane). Gain As discussed previously antennas do not radiate uniformly in all directions. Antenna Gain is the ratio of the […]

February 11, 2012March 31, 2012Antennas

Some Common Antenna Radiation Patterns

A Radiation Pattern is a 3 dimensional description of how an antenna radiates power in the surrounding space. This pattern is usually measured at a sufficient distance from the antenna known as the far-field. In simple words it is the power radiated in a certain direction with reference to an omni-directional antenna (a theoretical antenna that radiates equally in all the directions). Given below are the radiation patterns for some common antenna types. Dipole Antenna 3D Radiation Pattern Although the Radiation Pattern is a 3 dimensional quantity it is usually sufficient to describe it in two orthogonal planes (one […]

February 8, 2012February 8, 2012Antennas

Antenna Gain and Directivity

Antenna Gain and Directivity are two terms that are sometimes not that well understood. The Antenna Gain and Directivity are related through the following equation. G(θ,φ)=E*D(θ,φ) That is, the Antenna Gain in a particular direction is equal to the Directivity in that direction multiplied by the Antenna Efficiency. Antenna Directivity is the ratio of energy transmitted (or received) by the antenna in a particular direction to the energy transmitted (or received) in that direction by an isotropic source. This is also known as the Directive Gain. The Antenna Gain (also known as the Power Gain) seems to be a better […]

February 1, 2012February 1, 2012Antennas

E-field of a Dipole Antenna

In the previous post we plotted the E-field of a half wave dipole. We now turn our attention to higher antenna lengths such 1,1.5 and 2.0 times the wavelength. The E-field pattern is a three dimensional pattern, however, we only plot the E-field in a 2D plane along the axis of the dipole. It is observed that as the antenna length is increased from 0.5*wavelength to 1.0*wavelength the antenna becomes more directional. However, as the length is further increased from 1.0*wavelength to 1.5*wavelength and 2.0*wavelength sidelobes begun to appear. These sidelobes are an unwanted phenomenon in a typical telecommunications application. […]

January 26, 2012February 1, 2012Antennas, Random Thoughts

Half Wave Dipole Antenna

A dipole antenna is a simple antenna that can be built out of electrical wire. The most common dipole antenna is a half wave dipole which is constructed from a piece of wire half wavelength long. The wire is split in the center to connect the feeding wires. The E-field of the antenna has a circular pattern along a plane which cuts the axis of the antenna perpendicularly and is similar to a figure of 8 in a plane along the axis of the antenna [3D pattern]. The exact E-field can be calculated as: The MATLAB code for generating the […]

October 21, 2011June 7, 2012Channel Modeling, LTE, WiMAX

A Rayleigh Fading Simulator with Temporal and Spatial Correlation

Just to recap, building an LTE fading simulator with the desired temporal and spatial correlation is a three step procedure. 1. Generate Rayleigh fading sequences using Smith’s method which is based on Clarke and Gan’s fading model. 2. Introduce spatial correlation based upon the spatial correlation matrices defined in 3GPP 36.101. 3. Use these spatially and temporally correlated sequences as the filter taps for the LTE channel models. We have already discussed step 1 and 3 in our previous posts. We now focus on step 2, generating spatially correlated channels coefficients. 3GPP has defined spatial correlation matrices for the Node-B […]

October 3, 2011November 15, 2011Antennas, LTE, Network Planning, WiMAX

Antenna Radiation Pattern and Antenna Tilt

An introductory text in Communication Theory would tell you that antennas radiate uniformly in all directions and the power received at a given distance ‘d’ is proportional to 1/(d)^2. Such an antenna is called an isotropic radiator. However, real world antennas are not isotropic radiators. They transmit energy in only those directions where it is needed. The Gain of a antenna is defined as the ratio of the power transmitted (or received) in a given direction to the power transmitted in that direction by an isotropic source and is expressed in dBi. Although antenna Gain is a three dimensional quantity, […]

September 27, 2011November 15, 2011Antennas, LTE, Network Planning, WiMAX

Base Station Antenna Tilt and Path Loss

Path loss is basically the difference in transmit and receive powers of a wireless communication link. In a Free Space Line of Sight (LOS) channel the path loss is defined as: L=20*log10(4*pi*d/lambda) where ‘d’ is the transmit receive separation and ‘lambda’ is the wavelength. It is also possible to include the antenna gains in the link budget calculation to find the end to end path loss (cable and connector losses may also be factored in). Antenna gains are usually defined along a horizontal plane and vertical plane passing through the center of the antenna. The antenna gain can then be […]

September 24, 2011November 15, 2011Network Planning, WiMAX

WiMAX Path Loss and Antenna Height

As discussed previously the SUI (Stanford University Interim) model can be used to calculate the path loss of a WiMAX link. The SUI model is given as: SUI Path Loss Equation It has five components: 1. The free space path loss (A) up to the reference distance of ‘do’. 2. Additional path loss for distance ‘d’ with path loss exponent ‘n’. 3. Additional path loss (Xf) for frequencies above 2000 MHz. 4. Path gain (Xh) for receive antenna heights greater than 2 m. 5. Shadowing factor (s). The most important factor in this equation is the distance dependent path loss. […]