A reconfigurable antenna is an antenna capable of modifying its frequency and

radiation pattern In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the ''directional'' (angular) dependence of the strength of the radio waves from the antenna or other source.Constantine A. Balanis: " ...

dynamically, in a controlled and reversible manner. In order to provide a dynamic response, reconfigurable antennas integrate an inner mechanism (such as

RF switch An RF switch or microwave switch is a device to route high frequency signals through transmission paths. RF (radio frequency) and microwave switches are used extensively in microwave test systems for signal routing between instruments and Device und ...

es, varactors, mechanical actuators or tunable materials) that enable the intentional redistribution of the RF currents over the antenna surface and produce reversible modifications of its properties. Reconfigurable antennas differ from

smart antenna Smart antennas (also known as adaptive array antennas, digital antenna arrays, multiple antennas and, recently, Multiple-input multiple-output communications, MIMO) are antenna arrays with smart signal processing algorithms used to identify spatial ...

s because the reconfiguration mechanism lies inside the antenna, rather than in an external

beamforming Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in an antenna array in such a way that signals at particular angles ...

network. The reconfiguration capability of reconfigurable antennas is used to maximize the antenna performance in a changing scenario or to satisfy changing operating requirements.

Types of antenna reconfiguration

Reconfigurable antennas can be classified according to the antenna parameter that is dynamically adjusted, typically the frequency of operation,

polarization Polarization or polarisation may refer to: Mathematics *Polarization of an Abelian variety, in the mathematics of complex manifolds *Polarization of an algebraic form, a technique for expressing a homogeneous polynomial in a simpler fashion by ...

Frequency reconfiguration

Frequency reconfigurable antennas can adjust their frequency of operation dynamically. They are particularly useful in situations where several communications systems converge because the multiple antennas required can be replaced by a single reconfigurable antenna. Frequency reconfiguration is generally achieved by physical or electrical modifications to the antenna dimensions using RF-switches, impedance loading or tunable materials.

Radiation pattern reconfiguration

Radiation pattern reconfigurability is based on the intentional modification of the spherical distribution of the

Beam steering Beam steering is a technique for changing the direction of the main lobe of a radiation pattern. In radio and radar systems, beam steering may be accomplished by switching the antenna elements or by changing the relative phases of the RF si ...

is the most extended application and consists of steering the direction of maximum radiation to maximize the antenna gain in a link with mobile devices. Pattern reconfigurable antennas are usually designed using movable/rotatable structures or switchable and reactively-loaded

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...

elements. In the last 10 years, metamaterial-based reconfigurable antennas have gained attention due their small form factor, wide beam steering range and wireless applications.

Plasma antenna A plasma antenna is a type of radio antenna currently in development in which plasma is used instead of the metal elements of a traditional antenna.polarization Polarization or polarisation may refer to: Mathematics *Polarization of an Abelian variety, in the mathematics of complex manifolds *Polarization of an algebraic form, a technique for expressing a homogeneous polynomial in a simpler fashion by ...

modes. The capability of switching between horizontal, vertical and circular polarizations can be used to reduce polarization mismatch losses in portable devices. Polarization reconfigurability can be provided by changing the balance between the different modes of a multimode structure.

Compound reconfiguration

Compound reconfiguration is the capability of simultaneously tuning several antenna parameters, for instance frequency and radiation pattern. The most common application of compound reconfiguration is the combination of frequency agility and beam-scanning to provide improved spectral efficiencies. Compound reconfigurability is achieved by combining in the same structure different single-parameter reconfiguration techniques or by reshaping dynamically a pixel surface.

Reconfiguration techniques

There are different types of reconfiguration techniques for antennas. Mainly they are electrical (for example using RF-MEMS,

PIN diode A PIN diode is a diode with a wide, undoped intrinsic semiconductor region between a p-type semiconductor and an n-type semiconductor region. The p-type and n-type regions are typically heavily doping (semiconductor), doped because they are used ...

s, or varactors), optical, physical (mainly mechanical), and using materials. For the reconfiguration techniques using materials, the materials could be solid, liquid crystal, liquids (dielectric liquid or liquid metal).

References