Design and Implementation of RSLA Antennafor Mobile DBS Application

in Ku-Band Downlink Direction

By :

1) Dr.Ir.Joko Suryana

2)Dimas Budiarto Kusuma, ST

Radio Telecommunication and Microwave LaboratorySchool of Electrical Engineering and Informatics,ITB

Jl Ganesa 10 Bandung 40132, Indonesia

Overview

• In this research, a satellite on the move DBS receiver has beendesigned and implemented based on Radial Line Slot Array (RLSA)antenna which operates at Ku band.• This antenna is implemented with brass as conductor and air (er ≈ 1) as

dielectric material and has eight concentric array slot pairs to achieve conicalbeam, better gain and wider frequency bandwith compared to Makoto Andomodel.

• From the simulation and measurement results we can see that ourRLSA prototype has passed the technical specifications .• This antenna has conical beam, with 14.22 dBi at 12.0 GHz, operational

frequency bandwidth about 1.7 GHz and axial ratio about 3.79 dB.

Background

SOTM DBS

• The provision of DBS reception (pay TV) inmoving vehicles is now increasing. The needfor satellite-based pay TV services on mobilevehicles such as ships, aircraft, trains andbuses is perceived to be popular.

• In 2014, the number of Pay TV subscribersreached about 3 million as fixed DBSsubscribers

Background

• Previously, mobile satellite communicationsantenna uses a parabolic dish mounted on astabilized platform driven by two motors.Despite giving a pretty good gain, the use ofparabolic dishes on land, sea, and air vehicles isconstrained by air resistance on the parabolicdish and its heavy mass. A very good qualitymotor control system is required to support theantenna mechanism, which is obviously veryexpensive.

• Another solution is thin and flat microstripphased-array antenna system which will allowthe vehicle to keep moving aerodynamically,and the continuity of communication links is stillmaintained even when the vehicle is moving ordoing some maneuvers, but we still need tohave mechanical steering on azimuth direction.

Objectives

• The objective of this research is to designand implement a low-cost DBS receptionantenna at Ku-band which has goodstability to receive satellite signal whileon the move.

• This DBS receiver antenna requires tohave conical beam which its main beamdirection always point to the satelliteposition during on move.• No more mechanical beam steering systems• No need electronical beam steering systems

Methods

Technical Specs

• In this research, the target design andprototype is used for SOTM (satellite on themove) DBS receiver which operates at Ku-band for Indonesia area.

• The DBS receiver should has capability toreceive satellite signals at 17 – 22° forIndonesian Ku-band satellites reception(such as Palapa D). The minimal gain at 12GHz is more than 9 dBi and has small formfactor.

• The antenna should also has conical beampattern with bandwidth > 1 GHz.

• The detail of technical specifications can beseen as Table I

Methods

Structure

• The RLSA antenna is based on Makoto Andomodel

• RLSA antenna consists of two conductor plateswhich parallel to each other.• The bottom plate conductor is the ground plane

and the upper plate is the radiator.• The upper and bottom plate is short circuited in

this design.

• This RLSA antenna has some concentric slotpairs of antenna on its upper plate.• The slot is designed perpendicular to each other to

get the elliptical polarization.• Concentric array design is combined with coaxial

mode excitation to get the conical beam radiation .

Results : • Single element RLSA antenna design

Results : • The implemented single element RLSA antenna

• This RLSA antenna has -25.335 dB as the lowest return loss value at 11.8 GHz. At 12.0 GHz, the measured return loss was -21.377 dB. Bandwidth for < -10 dB return loss was measured around 1.7 GHz or 14.17% in the frequency region 10.8 GHz – 12.5 GHz.The implemented RLSA has conical radiation pattern as expected and its main lobe direction is at 18°. The measured gain was 14.22 dBi at 12.0 GHz.

Measured S11 Radiation Pattern on Polar

Results :

Further Developments

• For enhancing the performanceof satellite on the move DBSreceiver antenna, we havedeveloped our 4 array of RLSA.The RLSA array stucture iscomposed of 2 x 2 planar RLSA toget 6 dB gain better, so the overalantenna gain will 19 dB.

• This further development needs apower combiner which hasimplemented using low cost PCBFR-4 material. This 2x2 RLSA arraywill give better signal receptionfor Ku-band transponders ofIndonesian Satellites such asPalapa-D and the new Telkom-3.

Conclusions

• A SOTM (satellite on the move) DBS receiver has been designed andimplemented successfully based on Radial Line Slot Array (RLSA) antenna whichoperates at Ku band.

• This RLSA antenna has eight concentric array slot pairs to achieve conical beam,better gain and wider frequency bandwith compared to Makoto Ando model.

• This prototype antenna has conical beam and elliptical polarization, with 14.22dBi at 12.0 GHz, operational frequency bandwidth about 1.7 GHz and axial ratioabout 3.79 dB.

• Therefore our prototype has passed the technical specifications and appropriatefor satellite on the move DBS receiver.

• For enhancing the RLSA prototype, we also have developed the 2 x 2 planar RLSAantena which has about 6 dB additional gain.

• Moreover, this low cost implementation of RLSA antenna will decrese the CAPEXof DBS deployment at public trains, ships and buses in Indonesia.