RESEARCH DEPARTMENT
ALL INDIA RADIO & DOORDARSHAN

Customized Radios by R&D

All India Radio (AIR) as the public broadcaster has served as a powerful means of information, entertainment and education across the globe. Research Department has devised models to enhance radio listening capabilities for radio channels available on Direct to Home service and in digital terrestrial relays.

Customized FM Radio:

Since Radio is affordable and speaks in a local language and customs to a very common man, it has definitely an edge over other formats of communication when it comes to the question of guarding the strategic interests of a nation. Radio can be used as a medium to promote communal harmony and national integration in the Border States. In the event of any crisis radio can disseminate the correct and accurate information.

Therefore a need was felt to develop a radio set which is confined to play the FM AIR channels only especially in areas where other communication channels and sources for authenticating information are limited.

These radio sets can be useful in border and LWE areas to counter anti national propaganda.

DTH Radio:

The DTH Radio developed by R&D is a very useful medium to spread the multicultural exchange within the country. Presently it has about 40 Indian language radio channels which are expected to be increased to about 50 channels in future. All regional radio channels are incorporated and relayed through DD Freedish platform. To enable listeners to access these radio channels within the house, without using TV set, a compact and low power consuming DTH Radio has been developed by R&D. This would enable listeners to enjoy all Radio channels without using a setup box and TV set, directly using the Ku band dish signal fed directly to DTH radio. In case Freedish DTH setup with TV is already available, using a splitter the signal can be extended to DTH radio. This radio can be paired with a Bluetooth Speaker.

DVB-T2 RADIO:

Doordarshan India has started its DVB-T2 transmission in metro cities. Presently, three numbers of audio channels are radiated and it can further be increased to 8-10 channels. As there is still a significant number of radio listeners in rural and suburban cities, need was felt to make DVB-T2 radio set which can cater to this population. For reception of DVBT-2 signal, one set top box is required along with antenna (indoor/outdoor) to view TV Channels and listening to radio channels. Experimentation has been done by R&D to receive various radio channels transmitted though DVB-T2 transmitter, by a radio set without using a TV set. We have used one active indoor antenna for receiving this signal. Limited mobility is also provided through battery as this radio set is battery operated also. Presently, it is using 12V, 1.2 ah battery. This radio set will enable listeners to choose from different radio channels transmitted in digital format.

Low Cost DRM Receiver

AIR has migrated from analog to digital transmission in MW band.With the advent of DRM in MW band, significant improvement in the reception and coverage of AIR program has been observed. Commercial DRM receivers are required to receive the DRM signal and people can listen to FM like quality without fading in AIR MW Band through these receivers.
Presently, the cost of commercial DRM receiver available in Indian market is above Rs 12000/- which is not affordable for a common man in India. Research Department took initiative for development of low cost DRM receiver. The prototype of DRM receiver is under development.

DRM CHAIN OF TRANSMISSION AND RECEIVER

BASIC OVERVIEW OF DRM RECEIVER

The prototype model of DRM receiver has been designed on the basic principle of super heterodyne in which we tune to the desired frequency using a sensitive and high gain front end receiver. The IF signal of RF front end is mixed with the local oscillator for down conversion of DRM signal to an IF of 12 KHz and fed to SDR. Its output supplies a mix of modulated carriers that together convey the audio signal in the form of a digital stream through sound card in the platform which is processed in SDR. The DRM signal is a mix of various frequencies having spectral occupancy within a bandwidth of 9/18 KHz. The IF signal is fed to the line in of the soundcard through USB input of SDR.This signal is digitalized by the sound card, while a special SDR program looks after the demodulation of the DRM signal as well as the decoding of the MPEG-4 data stream. The demodulation and decoding is done by the software resulting in stereo audio signal, which is available at the output of SDR board. The decoded signal at the output of the soundcard is fed to the headphones or loudspeaker for sound reproduction.

Requirement/constraints for DRM receiver:

  • The RF front endcrucial part of DRM receiver which is under development.Presently, MW radio transmissionin is in AM-DRM simulcast mode. The transmission in pure DRM mode is limited to one hour duration only.
  • For a good DRM receiver, It is essentially required that sensitivity of RF front end be high enough to detect the DRM signal, as well as it should be having enough bandwidth i.e 20 kHz, so that it can receive signal in Pure DRM as well as in AM-DRM Simulcast Mode.
  • The crystal oscillator used for DRM receiver provides signal of 467 KHz.
  • Mixer to generate IF of 12 KHz signal should have low-power consumption, sufficient gain, improved noise figure and low spurious signal levels.
  • The sound card for the digitalization should have high quality performance, high SNR and very low THD+N .
  • The development board based on ARM processor is compatible with use in SDR supported board for decoding and demodulation of the DRM Signal.
  • Display is used to tune frequency and to show the other details of the SDR.
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    Last Updated on 23/04/2019