This presentation describes the Iboc technology that is being used as a method of broadcasting digital radio signals on the same FM channel.

1. IBOC TECHNOLOGY
PRESENTED BY: VISHAL KUMAR
ROLL NO-77
4TH SEMESTER ECE
In Band On Channel Technology
For Digital Radio

2. CONTENTS
Introduction
Working principle of HD Radio
Why Digital Radio?
Benefits of Digital Audio Broadcasting
What is IBOC
Block diagram
IBOC modes of operation
IBOC implementation Techniques
Eureka 147
Why delay in adoption?

3. 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.
 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.

4. WORKING PRINCIPLE OF HD RADIO
• 1- Analog and Digital audio broadcast
simultaneously created.
• 2- Digital audio Compression
• 3- Digital Broadcast Antenna for transmission of
compressed digital signal and analog audio
simultaneously.
• 4- Interference: digital signal is less prone to
signal dropout and reflections unlike analog
signal
• 5- In Car HD Radio System

5. 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.
• Transmission and Reception as digital domain.
• CD quality Audio
• Hooking up the digital output from a CD player directly to a radio transmitter.
• Efficient use of the limited radio frequency spectrum available &Easy-to-use
receivers

6. What is IBOC?
In Band On Channel (IBOC) is a hybrid method of transmitting digital , analog
radio signals broadcast simultaneously on the same frequency.
By utilizing additional digital subcarriers or sidebands, digital information is
“multiplexed” on an AM or FM analog, thus avoiding re-allocation of the
broadcast bands. However, by putting RF energy outside of the normally- defined
channel, interference to adjacent channel stations is increased when using digital
sidebands.
IBOC does allow for multiple program channels, though this can entail
taking some existing subcarriers off the air to make additional bandwidth
available in the modulation baseband. On FM, this could eventually mean
removing stereo. On AM, IBOC is incompatible with analog stereo, and any
additional channels are limited to highly-compressed voice, such as traffic and
weather. Eventually, stations can go from mode(both analog and digital) to all
digital, by eliminating the baseband monophonic audio.

7. Basics of IBOC
• The IBOC technology is used to transmit CD-quality audio signals to radio receivers
along with such data as station, song and artist identification, stock and news
information and local traffic and weather updates.
• The broadcasters can use the existing radio spectrum to transmit AM and FM
analogue simultaneously with higher quality digital signals.
• The system employs multiple digital signaling techniques, such as redundant
sidebands, blend, first adjacent cancellation and code and power combining.
• To compress the audio data and increase transmission without losing sound quality, it
uses the PAC audio-compression technology.

8. 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
LucentTechnology.
 The USADR AM IBOC DAB system basically
comprises the codec, forward error
correction(FEC) coding, and interleaving
section, modem and blender.

9. Block diagram of the IBOC DAB transmitter

10. 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.

11. HYBRID IBOC WAVEFORM
 Low-level digital sidebands are added to
each side of the analogue signal.
 The bandwidth is limited to 200 kHz from
the centre frequency.
 Restricting the digital sub-carriers to 70kHz.
 This minimizes interference
to the analogue host and adjacent channels
without exceeding the existing spectral mask.
 This bandwidth is wide enough to support a
robust, hybrid IBOC service with virtual CD-
quality audio that mirrors the coverage of
existing analogue radio stations.
Fig. 3: FM hybrid IBOC power spectral density

12. 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.

13. 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.

14. Low Level Combining Option

15. • 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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16. HIGH LEVEL COMBINING OPTION
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17. • 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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18.  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.
Eureka 147: The digital radio system in use
A small screen attached to the digital receivers
displays text and pictures. Text, data and images
can be diffused at the scale of a country or a
region.

19. WHY DELAY IN ADOPTION?
• Low power FM stations are prone to interference.
• An HD Station’s broadcasting range is only equal to the range of a terrestrial
broadcasting tower so doesn’t cover a wider area as would satellite radio.
• IBOC licensing, and service rules have not been adopted yet.
• Cost of equipment is quite high.
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20. CONCLUSION
FM transmission is an area of communication that is always moving with
technological advancements. As the new digital radios become more available,
dramatic improvements will be heard by listeners. Careful design of the new
transmissions systems will pay off with reduced costs and improved
performance and reliability. HD Radio FM is both robust and efficient in the
difficult mobile environment, SDR provides flexibility and Cognitive Radio will
definitely define a whole new level of FM transmission.

21. REFERENCES
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[1] Russell Mohn, “A Three Transistor Discrete FM Transmitter,” ELEN 4314
Communications Circuits - Design Project, pp. 1, April 2007.
[2] “FM broadcasting in the United States” Ibiquity /ATTC/ Dynasat FM IBOC Test Data Report, Aug 2001
[3] T.U.M Swarna kumara et al., “A Mini Project on Simple FM-Transmitter”.
[4] E. F. Louis, Principles of Electronic Communication Systems. McGraw-Hill, 2008
[5] “The Future of Radio”. The Swedish Radio and TV Authority, 2008.
[6] Holm, Steve (2007). "Lydkvalitetet i DAB digitalradio". Digitale Utgivelser ved UiO. Retrieved 2009-01-03.
(Norwegian).
[7] C. Renee, “An Industrial White Paper: HD Radio”
[8] C. W. Kelly, “Digital HD Radio AM/FM Implementation Issues”, USA.
[9] C. W. Kelly, “HD-Radio: Real World Results in Asia”, USA.

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