Is this an isotropic Antenna?

[electroRF]

Hi,
Is the following antenna isotropic, i.e. receives signals in all directions?
DMM-7-27

It is said here in the Operating Frequency Table 'isotropic gain = 2.5dBi' which means it is not isotropic, but in datasheet it says that its radiation pattern is omnidirectional,
View attachment 68354


Thank you very much.

 

[JimB]

An "Isotropic Antenna" is a theoretical concept which is useful when performing link budget calculations, and gives a reference point for expressing the gain of "real world" antennas.

So, no that antenna is not isotropic.

The expression "isotropic gain = 2.5dBi" would be more correctly stated as "gain = 2.5dBi".
In other words the gain is 2.5dB compared with a theoretical isotropic radiator.

Several forms of antenna are considered to be omni-directional, but only in one plane.
A vertically mounted dipole is omni-directional in the horizontal plane, but it is not omni-directional in the vertical plane.
I suggest that the antenna in question is omni-directional in the horizontal plane.

JimB

 

[dr pepper]

there is or has been some argument amount isotropic ratings, ie they make an aerial look better than it really is, a tru isotropic as far as I know would only be true in outer space!
some better specs quote dbd, ie compared to a diplole.
An aerial that has gain refered to dbi can often show no gain compared to dbd ie a dipole.

 

[RCinFLA]

Antennas are all about losses and directivity. An antenna only has gain over isotropic by directing more energy in a given direction to the detriment of other directions. In almost all radio communications directivity is a good thing as there is almost always an advantage to focus the available power in a productive direction and accentuate reception from a particular direction. Radio communications is all about desired signal to noise + interference ratio which directivity can help improve.

A star (sun) is close to an isotropic radiator and even they are not perfect with regard to radiation in their polar axis versus equatorial plane.

All real antennas have inherent losses that eat up some of the relative directivity gain.

 

[dproc]

A single narrow-band antenna must have at least one null direction in which there is no coupling with the other antenna. The link in the OP's post is to ~two~ UWB antennas driven separately. If they are driven/received correctly (notable time difference between pulses, etc.), then there will be no null direction. There will still be some variation in gain per direction. You'd need a lot of separately driven (with UWB) antennas to make an "antenna" that has close to the same gain in all directions. Technically, two separately-driven antennas is not an "antenna" though, in the context of isotropy. Also, you can take advantage of knowledge of the current link to drive/receive the two antennas separately. For example, you could put all your energy into the antenna with the best coupling.