Antenna design & consultancy
Antennas are used to transfer energy to and from radiowaves. Any object doing that could be considered to be an antenna. However some structures have desirable properties. Designing antennas is about finding these structures.
Some general important antenna properties are: resonance frequency, input impedance, bandwidth, directivity and efficiency, in practice many other aspects play a role like size, cost, beauty and manufacturing.
There exists may types of antennas some classifications are:
- dipole - monopole
- 3D - planair
- wire - aperture
In many wireless applications antenna size is very important. For this reason monopoles, like the (folded) inverted F types are populair, these types are working with or are referenced to the groundplane of the device. However groundplanes are often so small that they can hardly be considered as an equipotential plane, they are more just another metal object of the device and strongly influence the antenna properties. Therefore modeling the complete RF board or application is essential.
A folded inverted F antenna example
Below is a picture of a folded inverted F antenna for 2.44 GHz applications. An inverted F antenna has a good trade off between size and bandwidth while its input impedance can be designed to be 50 ohm. By folding the long leg of the antenna the antenna size becomes much smaller, trading size against bandwidth. In this example the bandwidth is large enough for the ISM band (80 MHz) so a folded structure is beneficial.
The picture on the right side shows the far field radiation of the antenna (+ RF module). The radiation is mainly in the direction of the folded long leg, which is also the case for non-folded inverted F antennas. Click on the picture to show an animated view.
RF module with the antenna
Farfield radiation @ 2.44 GHz
The next two pictures show the patterns of the electric and magnetic fields. The Electric field is pointing towards the groundplane of the board, the magnetic field is rotating around the leg of the antenna. Move the mouse over the pictures or click on them to see an animation of the fields.
Magnetic (H) field @ 2.44 GHz
Electromagnetic simulations are a proven method to design antennas, for small antennas on RF modules they are essential. If you want help with your antenna problem, send us an email.