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An Introduction to Ferrite Rod Antenna

Ferrite Rod Antenna

Ferrite rod antenna is a small magnetic loop antenna used in AM broadcast transistor radios for medium & long waveband reception and RFID applications. It is designed with a rod or bar made of ferrites and includes a coil wound around the ferrite rod with the help of a variable tuning capacitor in the radio circuitry.

When made with a suitable ferrite core, the antenna gives excellent results over shortwave frequencies. The core helps to concentrate the magnetic field of the radio waves and gives out a stronger signal than a similar-sized air core antenna. Other names for these antennas are ferrod, ferrite rod aerial, or loopstick antenna.

In this blog, we’re going to look at the basic aspects of a ferrite rod antenna and its parameters that you must consider before using it for your RF applications.

How does Ferrite Rod Antenna work?

Ferrite Rod Antenna is ideal for portable applications as it is lightweight & smaller. The antenna is effective for medium & long wave bands, but it is also used in shortwave bands for lower frequencies.

In terms of performance & frequency response, it is compromised because of the losses in the ferrite core. Therefore, the antenna operates at frequencies of 2 to 3 MHz.

Primarily, a ferrite rod antenna is used to receive lower frequency signals between 50hz to 50khz. It operates as transmitting antennas for applications that are suitable with low levels of power & low efficiency. If the power levels are high, then the ferrite rod may incur heat dissipation issues.

However, the compact size & convenience add to its advantages and increase its demand for RFID applications.

How is it designed?

The antenna can also be designed using different combinations of parameters. As a result, a shorter & wider coil with more turns can produce the same output voltage as a longer & thinner coil with lesser turns & a higher magnetic permeability.

Each configuration will use different materials, so the costing may vary. The primary aim is to provide a target output voltage & power while satisfying constraints, such as physical dimensions and Q factor. This can help you find the best configuration that has the lowest cost & fulfils all design constraints.

Ferrite Rod Antenna Parameters

The ‘Q’ of the tuned circuit and the radiation resistance are the two most important parameters of a ferrite rod antenna. These parameters regulate the locations in which the antennas may be employed as well as the design of the circuits that use them.

Importance of The ‘Q’ Parameter

The ‘Q’ or Quality parameter of the circuit design in which the ferrite rod antenna coil is placed is an important consideration. To work efficiently, the circuit must have a high Q at frequencies over which the antenna is going to operate.

If the frequency is at a few hundred kHz, a medium permeability material will be placed in the ferrite rod antenna that would help to maintain a Q value of 1000 approximately. Now, at this value, the antenna needs tuning to operate over a higher frequency.

The Q value of the ferrite core in the rod will also be greater than the material value, since the magnetic circuit is open. This value has a direct relation to the maximum operating distance.

If you select a frequency, then the inductance of the antenna should have a low tolerance of the resonant frequency. The lower the tolerance, the higher frequencies will fit in the interval. If the permeability is not very low, the inductance will be determined by mechanical dimensions and number of turns.

How is it useful for Radiation Resistance?

The antenna includes a tiny loop which is less than a wavelength & has a low radiation resistance, if it is without ferrite. Hence, the losses that occur because of the resistance of the wire would be extremely high.

To overcome this, a ferrite core is placed in the coil to increase the radiation resistance of the ferrite rod antenna. This brings the radiation resistance to an acceptable level & reduces the resistive losses that occur because of the wire.

While the ferrite rod is important to raise the radiation resistance in the antennas, it brings up other losses. The ferrite absorbs the energy, which is required to influence the magnetic alignment in the granular structure of the ferrite core.

If the frequency is higher, the number of changes is greater, and hence, the losses are higher. Owing to this, ferrite rod antennas are not used in higher frequencies, but to a low MHz only.

Conclusion

Ferrite rod antenna is a good choice in terms of efficiency, frequency & tuning. Their popularity & demand as RF antennas for portable radios is growing all over the world.

At Alisha Coils & Transformers, we design Ferrite Rod Antennas through quality & innovative technologies to provide customised solutions to our customers. Our strength lies in the in-house manufacturing of ferrite cores, which helps us to ensure product quality & fast delivery.

Contact our team for any queries & concerns & let us find you the right product for your applications!