ANTENNA SYSTEMS

     Antenna technology has gone through several changes commensurate with the evolution of the complex systems for various applications. DRDO has developed the capability in designing antennas for various ground-based and airborne radar systems, communication systems, electronic warfare, and underwater scenarios.

 
Squareax Planar Microstrip Patch Antenna

GPS Antenna
     Increased application of Global Positioning Systems (GPS) for navigational aids, necessitated the development of low profile antennas. Two types of low profile antennas, viz., Wraparound Microstrip Antenna for Pinaka Rocket and Quadrifilar Helix Antenna for manpack GPS have been developed by DRDO. The development of GPS antenna for Pinaka, along with its feed network, is a challenging task as it requires antenna to be conformal with the cylindrical body of the rocket. Quadrifilar Helix Antenna is one of the preferred antennas for GPS application owing to its smaller size and cardioid pattern.


Quadrifilar Helix Antenna

Specifications
Centre frequency : 1575.4 MHz
Bandwidth : 3 MHz
Polarisation : RHCP
Gain : Better than 0 dB
VSWR : < 2:1
RaDIATion pattern : Hemispherical
Axial ratio : < 6 dB
The antennas have been fabricated, tested and are undergoing field trials.


Squareax Planar Microstrip Patch Antenna Array
    
A planar microstrip patch antenna array of dimension 4.2 m x 1.1 m with a rectangular coaxial line (RCL) corporate feed network and a capacitively coupled microstrip patch has been designed and developed for Airborne Surveillance Platform programme.
It comprises very low side lobes, broadband width, high gain and high power handling capability.


Wraparound Microstrip Antenna

Specifications
Frequency of operation : S Band
Bandwidth : 12 per cent
Polarisation : Vertical
Power Handling : 140 kW (peak), 7 kW (avg)
Gain : 34 dB
VSWR : < 1.8:1
Side lobes : < - 35 dB (azimuth)
< -30 dB (elevation)

Salient Features

  • RCL corporate feed network and probe fed capacitively coupled microstrip patch raDIATing element

  • Broad bandwidth, ultra low side lobes, high gain, high power handling capability, lightweight

  • Airborne Surveillance Radar application

  • Design can be extended to other frequency bands

The antenna has been fabricated, tested and found to meet all the required specifications. It has been designed so that the technology can be tailor made for any other similar application.


Quadraloop UHF Airborne Antenna
    
A quadraloop antenna with distinct airborne characteristics that makes it suitable for high-speed aircraft has been developed. It has been shaped for very low drag. The antenna can be used in a stand-alone mode or in an array environment depending upon the pattern requirement.

Specifications
Centre Frequency : 461 MHz
Bandwidth : 5 MHz
Polarisation : Vertical
Gain : Better than 0 dB
VSWR : < 2:1
RaDIATion Pattern : Hemispherical
Weight : 85 gm
Dimension : 180 mm (L) x 18 mm (W) x 30 mm (H)

Salient Features

  • Airborne telemetry link application

  • Low drag, low profile, lightweight airborne antenna suitable for high speed aircraft

  • Fitted in various airborne platforms such as MiG 29, AVRO, HANSA aircraft for telemetry link

  • Design can be extended to other frequency bands

The antenna has been fabricated, tested and being used in the fighter aircraft of Indian Air Force.

Ku Band Antenna for High Resolution Radar
    
A lightweight, broadband planar antenna with an aperture size of 0.7 m x 0.4 m and a gain of 35 dB has been developed for UAV. To meet the gain requirement, dimension and weight, operating frequency of the antenna is in Ku band. Two approaches have been followed, viz., parabolic reflector and planar microstrip patch antenna.

Salient Features

  • Lightweight, Broadband

  • Fabricated with very high machining accuracy with surface finish of + 30 microns

  • Design can be extended to other frequency bands


Parabolic Reflector Antenna

Specifications
Frequency of operation : Ku band
Bandwidth : 6 per cent
Beamwidth
Azimuth : 1.8o 0.2 o
Elevation : 3.2 o 0.2 o
Side lobe level
Azimuth : < -25 dB
Elevation : < -20 dB
Gain : 35 dB
VSWR : 1.8 : 1
Power handling : 300 W (peak)
Weight : < 5 kg

     Antennas along with its back-up structure and feed mounting mechanism have been fabricated. The return loss measurement and its pattern test has been carried out and found to be meeting the requirement specified above.