driven array

Driven Array

Driven Array defined

- an array that has two or more driven elements. In which each elemet receives RF energy and can be arranged in various ways to produce different degrees of directivity and gain.

Three Basic Type of Driven Arrays

1. Collinear Antenna- usually uses two or more half-wave dipoles mounted end to end.

- it has a bidirectional radiation pattern but the two beams are much narrower providing greater directivity and gain.

Collinear Antenna

Collinear Antenna Radiation Pattern

Applications of Collinear Antenna - used only on VHF and UHF bands

- it can be mounted vertically at the high frequencies to provide an omnidirectional antenna with gain.

2. Broadside Array

- is essentially a stacked collinear array.

- it consists of half-wave dipoles spaced form one another by one-half wavelength.

- bidirectional in radiation but with a narrow beam width and high gain.

Typical antenna length: 2 to 10/λ’s

Typical Spacing : λ/2 or λ/4Number of Elements: dozens

Broadside array

Broadside Array Radiation Pattern

Application of Broadside ArrayBroadside arrays are used for a wide range

of radio waves. At decameter (short) wavelengths, they are used chiefly for radio broadcasting over long distances.

3. End-fire Array

- it uses half-wave dipoles spaced one-half wave-length appart. Both are driven by the trans. line.

- it has a bidirectional radiation pattern but with a narrower beam widths and gain.

End-fire Array

End-fire Array Radiation Pattern

Application of End-fire Array

* Used in communication system and in some TV applications.

*High directivity applications* and now proposed to be used in vehicular

mobile application.