ANTENNAS

Airborne Blade Antennas


 

DRDO has developed a variety of airborne blade antennas in different sub-bands covering the frequency range of 20-2000 MHz. Airborne blade antennas are basically omni-directional and vertically polarised. These antennas are used for airborne surveillance, monitoring, direction finding, telemetry and jamming purposes. The antennas offer the advantages of reduced size and lightweight, because of innovative matching circuits and loading techniques incorporated in the design. The antennas can withstand severe aerodynamic stress and strains. The raDIATor circuit of antenna is etched on high-grade quality printed circuit Cu-clad material and is enclosed in aerodynamically shaped FRP radome. The material composition and wall thickness are so chosen to guarantee full efficient EM raDIATion and minimum losses. The antennas have qualified for airborne platforms, remotely piloted vehicles, light combat aircraft, etc. The antenna technology has been transferred to the vendors for quantity production.


Compact Ultra Broadband Log Periodic Antenna (20-1000 MHz)


 

A state-of-the-art, compact, ultra broadband log periodic antenna has been developed. The antenna is unique and special, as single antenna covers the entire frequency range 20-1000 MHz. Innovative design concept has been used to make the lower band antenna elements of same size, an unusual feature normally not found in log periodic antennas. State-of-the-art inductive loading technique has been used on the antenna elements to restrict their lengths to 2 m (max.) for easy transportation and packaging. The antenna boom, which is 4.7 m long, has been split into three sections for easy assembly and dis-assembly, and push-fit. The antenna consists of 30 pairs of easily removable raDIATing elements fitted by clamp-type arrangement. Each section of the antenna can be independently used for limited frequency band. The antenna is suitable for jamming and surveillance and has qualified for field-worthy tests.


Broadband Dipole Antennas


A conventional half-wave dipole antenna is narrow band and offers typically about 5 per cent bandwidth. DRDO has designed and developed broadband dipole antennas covering more than octave bandwidth by incorporating specially designed and optimised passive broadband matching networks and broadband baluns. The antennas are small in size, lightweight and can be used for surveillance and monitoring, and direction finding applications for ground-based and semi-mobile platforms. The antennas are comparable/superior to the antennas available in international market.
The broadband dipole antennas have been developed in the following frequency bands:

Electrically Small Broadband Dipole Antenna (20-160 MHz)


20-160 MHz electrically small broadband dipole antenna


Electrically small broadband antenna is 76 per cent less in length compared to a conventional half-wave dipole antenna. The antenna operates at the lowest frequency at 0.12 l and has been matched to 50 Ohm by means of a specially optimised matching network at the base. The miniature Guanella balun comprises a ferrite core transmission line transformer.

Electrically Small Broadband Dipole Antenna (160-500 MHz)

 
160-500 MHz electrically small broadband dipole antenna      
 

Electrically small broadband dipole antenna is 40 per cent less in length compared to a half-wave dipole antenna at 160 MHz. Matching of the antenna has been accomplished with an optimised broadband matching network that matches the antenna to the receiver. The novel balun has been designed by means of a combination of ferrite beads on the coaxial cable as well as the decoupling sleeve on the coaxial cable.


High Gain Dipole Array (0.5-1.0 GHz)


High gain dipole array antenna

High gain dipole array antenna comprises planar array of eight broadband dipoles mounted on a grid planar reflector covering the full one octave bandwidth. This antenna offers excellent gain of 16 dBi as required for generating high effective raDIATed power for effective jamming and also capable of intercepting very weak signals normally encountered in radio relay signals. The design of the antenna involved develop-ment of phase matched, broadband dipoles and arraying them to get consis-tent good impedance and patterns behaviour over the entire frequency band.
The dipoles have been placed in two rows and four columns configuration. The array is excited with uniform current distribution and combined in eight-way corporate power divider. Dipoles element spacing and heights have been optimised for minimum mutual coupling and grating lobes. The antenna is capable of withstanding high RF power.
The high gain dipole array antenna has vital applications in data communications for military role.