How is the directivity of an antenna calculated?

Article by: Ing. Naia Otero Jr. | Last update: April 10, 2022
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The Directivity of an antenna is defined as the ratio between the power density radiated in one direction, at a distance, and the power density that an isotropic antenna would radiate at the same distance, with equal total radiated power.

What is directivity index?

The directivity factor expressed in decibels is called the directivity index: Positive values ​​of the directivity index, if they exist, denote a source intensity gain with respect to the isotropic intensity, while negative values ​​indicate losses.

What is meant by gain and directivity of an antenna?

In the definition of Directivity we speak of the power radiated by the antenna, while in the definition of gain we speak of the power delivered to the antenna. The difference between both powers is the power dissipated by the antenna, due to ohmic losses.

How is the gain of an antenna calculated?

To measure the gain, we fix a point and calculate the intensity of the signal of a transmitter, for example of 100 watts connected to an ideal theoretical antenna, called isotropic1, which gives us the optimal values. Then we switch and set the directional antenna to the same 100 watts and compare.

What is the directivity of a dipole antenna?

The theoretical value of Directivity for dipole antennas is 1.64 <1>. Since the shapes of the radiation patterns obtained for the dipoles turned out to be similar to the theoretical ones, it is possible to assume and use this value (1.64) as the directivity value.

31 related questions found

How is the wave radiation of a dipole?


An important characteristic of this type of radiation is that the intensity of the electromagnetic wave radiated by a dipole antenna is zero along the axis of the antenna and maximum in directions perpendicular to the axis of the antenna.

What is the performance of an antenna?

antenna performance.

The performance of a transmitting antenna is the ratio between the radiation power and the total power applied to the antenna, in which, in addition to the radiation power, the loss power is taken into account.

How to calculate the gain of a satellite dish?

Calculation of gain of a satellite dish

Calculation of gain in satellite dishes To calculate gains in satellite dishes, the following concepts must be clear: Wavelength = C/f = 300*10exp6 m/s/ 5.8*10exp9 Hz = 5.17 cm.

What is the gain of a signal?

Gain, referring to electrical signals, is a magnitude that expresses the relationship between the amplitude of an output signal with respect to the input signal and is measured in bels (B) or in submultiples of it as decibels (dB). When the gain is negative (less than 0), it is called attenuation.

When directivity and gain are equal?

The efficiency factor K, is the ratio of the power radiated by the antenna to the total power at the input, it is a number between zero and one. If the antenna has no OHMIC losses and therefore K=1, then G=D, that is, the power gain and directivity are equal.

What is the gain of a Wi-Fi antenna?

Gain is the sum of the increase in energy that an antenna adds to the radio frequency (RF) signal. As the gain of a directional antenna increases, the angle of radiation generally decreases. This provides a greater coverage distance, but reduces the angle of coverage.

What is the product of the power radiated by an antenna times the directivity or the power delivered times the gain called?

The equivalent isotropically radiated power (EIRP) of a transmitting station is the product of the power supplied to the antenna times its gain.

What is directivity and types?

The Directivity of an antenna is defined as the ratio between the power density radiated in one direction, at a distance, and the power density that an isotropic antenna would radiate at the same distance, with equal total radiated power. is defined as the equivalent solid angle.

What is the directivity of a loudspeaker?

Directivity. It is the variation of the sound pressure level at a fixed distance, depending on the angle of rotation of the loudspeaker. The directivity is specified by graphs for third-octave bands of pink noise, with different center frequencies and for turns from 10º to 15º.

What is the directivity of a microphone?

Referring to microphones, it is the ability to pick up a signal depending on its orientation with respect to the sound source. That is, many microphones require the microphone to “look” at the source to best pick up the signal.

How to measure the diameter of a satellite dish?

To determine the diameter of the parabolic reflector, it is necessary to specify the satellite to which it is going to be pointed, so that, by consulting its coverage diagrams, we can know the reception power and thus select the size of the antenna.

Which type of reflector has more gain? A center focus or an offset type?

By eliminating the “shading” of the outdoor unit, offset parabolic antennas have better performance than those with centered focus, an offset reflector of 75 cm in diameter is equivalent to one of 90 cm with centered focus.

How is a logarithmic periodic antenna formed?

The most common form of log-periodic antenna is the log-periodic dipole array or LPDA. The LPDA consists of several dipole-driven elements of gradually increasing length half-wave, each consisting of a pair of metal rods.

What is an antenna and how does it work?

An antenna is a metallic conductor capable of emitting or capturing electromagnetic waves. There are, therefore, two types of antennas: those that emit and those that capture the signal. The function of a transmitter antenna is to convert variable electrical signals into electromagnetic waves and emit them, that is, radiate them.

What is the power of an antenna?

The total radiated power can be obtained as the integral of the power density in a sphere that encloses the antenna. Radiation intensity is the power radiated per unit solid angle in a given direction. Units are watts per steradian.

What is an antenna and what is it for?

An antenna is a device made to transmit (radiate) and receive radio (electromagnetic) waves. There are several important characteristics of an antenna that must be considered when choosing a specific one for your application: Radiation pattern. Gain.

What is oscillating dipole radiation?

The oscillating dipole is a model involved in electromagnetism that describes the effects of oscillatory motion of a charged particle around a fixed point. It explains phenomena such as Rayleigh scattering, the operation of dipole antennas, or thermal radiation.

How does a half wave dipole work?

The half-wave dipole is made up of a conductive element that is a half-wavelength electrical wire or metal tube. The half wave dipole is normally fed into the middle where the impedance drops to its lowest level.

How does an electric dipole work?

An electric dipole is a system of two charges of opposite sign and equal magnitude close to each other. Dipoles appear in dielectric insulating bodies. Unlike what happens in conducting materials, in insulators the electrons are not free.

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