IBOC TECHNOLOGY

IBOC TECHNOLOGY

PRESENTED BY,
MARIA JOSEPH

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CONTENTS

 Introduction
 Why Digital Radio?
 What is IBOC
 Eureka 147
 Block diagram
 IBOC modes of operation
 IBOC implementation Techniques
 Benefits of DAB
 Why delay in adoption?
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INTRODUCTION

 Digital radio, also called digital audio broadcasting
(DAB), is transmission and reception of radio signals in
the digital domain, as opposed to the traditional
analogue transmission/reception by AM and FM systems.
 Digital radio is similar to hooking up the digital output
from a CD player directly to a radio transmitter. At the
other end is a digital-to-analogue converter (DAC), which
converts the digital signal back into analogue mode so
that it can be heard on the audio system as it was
recorded.
 In practice, the CD player is hooked up to a control board,
which, in turn, routes the signal as part of the feed to the
radio station’s transmitter.
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 The signal is either impressed onto a signal
carrier and transmitted via uplink to a satellite
or transmitted across the land.
 In both the cases, the signal is received and
converted into analogue by a specialized DAC
within the radio’s tuner circuit.
 Currently, digital radio broadcasts are
available in select countries, including the UK ,
Germany and Canada.

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Why Digital Radio?

 The main advantage of digital radio is that it doesn’t
have the usual distortion associated with analogue radio
such as hissing, popping and phasing.
 It is immune to distortion from multipath, adjacent
stations.
 User get a new array of data-rich services including
traffic information, sports score and weather updates,
stock prices, etc..
 The data is displayed on the LCD in the form of text,
images and video. Thus multimedia radio becomes
reality.
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Contd…

 To explain, in analogue radio, a large number of radio
signals can exist in the atmosphere at any time. However
each of them is being transmitted on a different radio
frequency. Stations that share the same radio frequency
are usually far apart so that they don’t interface with
each other. In order to receive a station within its
transmission range, all we have to do is tune the receiver
to its frequency.
 The drawback of this analogue mode is that the signals in
close proximity in terms of frequency can interfere with
each other to some extent, depending on the modulation
pattern of the radio station and the ability of the radio
receiver to reject interfering adjacent signals.
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What is IBOC?

In-band on -channel (IBOC) is a hybrid
method of transmitting digital radio and
analog radio broadcast signals
simultaneously on the same frequency.

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IBOC: a new system

 The IBOC technology allows digital audio broadcasting
without the need for new spectrum allocations for the
digital signal.
 The IBOC system will be compatible with existing tuners
as it utilizes the existing AM and FM bands by attaching a
digital side band signal to the standard analogue signal.
 For digital compression, the IBOC uses a perceptual
audio coder (PAC) developed by Lucent Technology.
 The USADR AM IBOC DAB system basically comprises
the codec, forward error correction(FEC) coding, and
interleaving section, modem and blender.

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Eureka 147: The digital radio
system in use
 Uses at much higher frequencies than standard 88-
108Mhz FM band and 0.525-1.705MHz AM band.
 UK utilizes Band III (174-240 MHz)
 Canada uses L-Band (1452-1492MHz)
 The eureka system broadcasts multiple stations and
services over a single frequency in something called a
multiplex.
 The bandwidth within the multiplex is allotted to stations
as needed.
 Stereo programming is typically broadcast at 192kilobits.

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Block diagram of the IBOC DAB transmitter

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IBOC modes of operation

Hybrid mode : In
this mode the
digital signal is
inserted within a 69.041 kHz
bandwidth, 129.361 kHz on
either side of the analog
FM signal. Each sideband is
approximately 23 dB below the
total power in the FM signal.

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Extended hybrid mode :This mode
includes the hybrid mode and additional
digital signals are inserted closer to
the analog signal, utilizing a 27.617 kHz
bandwidth, 101.744 kHz on either side of
the analog FM signal. The total power of
the digital
sidebands is 20dB
below the nominal
power of the FM
analog carrier.

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All Digital mode: This mode replaces
the analog signal with additional digital
signals and also includes the digital
signals of the Hybrid and Extended Hybrid
Modes. The total power of the digital
sidebands is 10dB
below the nominal
power of the
replaced FM analog
carrier.

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IBOC implementation Technique

The requirement for FM-to-IBOC isolation is also
somewhat difficult to achieve in practice because of the
power ratio between FM and IBOC(100:1).

In a combiner that has to deal with a 1:1 power
combining ratio, a 26 dB isolation seems to be fine.

There are a few techniques used to combine FM and
IBOC signals.

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Low Level Combining Option

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 Low level combining relies essentially on a common
amplification technique which means that both the
host FM and the IBOC signals are amplified in the
same Power Amplifier(PA).
 This method requires very good linearity from the
PA part.
 Most PA’s cannot handle common mode
amplification at rated output power; they have to be
operated in the most linear portion of their transfer
curve which results in a substantial back-off(around
6-10 dB).
 As IBOC adds about 1% to the total channel power,
its power contribution is negligible so the power
rating of the antenna is normally not an issue.
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High Level Combining Option

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 High level combining is based on the use of
distinct power amplifiers for the Host FM and
the IBOC signals.
 This technique uses an IBOC Power injector
which is basically an inverted directional
coupler
 Its power ratio is selected to minimize the
loss on the host path, typically 0.5 dB.
 Such an injector offers a loss of about 10 dB
on the IBOC path

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Benefits of Digital Audio
Broadcasting
 High quality digital audio
 Reliable delivery to fixed, portable and mobile receivers
for interference-free reception.
 Efficient use of the limited radio frequency spectrum
available.
 Easy to use receivers.
 Flexibility and choice of programmes for listeners.
 Added-value system features such as multimedia.

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Why delay in adoption?

 Low power FM stations are prone to
interference.
 IBOC licensing, and service rules have not
been adopted yet.
 Cost is high.

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REFERENCES

 http://www.fcc.gov/encyclopedia/iboc-digital-radio-
broadcasting-am-and-fm-radio-broadcast-stations
 http://transition.fcc.gov/mb/audio/includes/23-
digital.htm
 http://www.ibiquity.com/
 http://www.fcc.gov/mb/audio/digital.html
 http://www.worlddab.org/introduction_to_digital_broad
casting/dab_plus_digital_radio
 http://www.owdjim.gen.nz/chris/radio/DRM/

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IBOC TECHNOLOGY

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IBOC TECHNOLOGY