THE RADIO OF THE FUTURE Natarajan.P No. 17 S7 Electronics & Comm. PTDC College of Engineering,...
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Transcript of THE RADIO OF THE FUTURE Natarajan.P No. 17 S7 Electronics & Comm. PTDC College of Engineering,...
THE RADIO OF THE FUTURE
Natarajan.P
No. 17
S7 Electronics & Comm. PTDC
College of Engineering, Thiruvananthapuram
DEFINE DRM DRM is the world’s only
non-proprietary Digital AM Radio Systems for SW,MW, and LW with
ability to use existing frequencies and bandwidth.
DRM covers the broadcasting band below 30 MHz. College of Engineering,
Thiruvananthapuram
TRANSITION FROM ANALOGUE
• Fairly easy to start digital broadcasting• Difficult to stop analogue broadcasting
(because of the many millions of analogue radio and TV sets owned by consumers)
• The real benefits of spectrum efficiency can be achieved only when the analogue services stop
• As many countries have introduced digital TV, plans are being made for analogue TV switch-off
• Analogue radio switch-off will take a long time– starting DIGITAL services early is the best
mechanism for stopping ANALOGUECollege of Engineering, Thiruvananthapuram
– it uses the spectrum much more efficiently than analogue broadcasting
– digital transmitters operate at lower power– the number of radio & TV services can
increase– it offers improved quality, especially on
mobile and portable receivers– it offers new features, such as interactivity
DIGITAL BROADCASTING
is important because:
College of Engineering, Thiruvananthapuram
DRM & DAB• Two digital radio systems:
– DRM for use in the AM bands (LF, MF & HF)– Eureka 147 DAB for use in VHF & UHF bands
• The EBU has endorsed both systems because they are complementary– DRM is designed for use in the narrow channels
currently used for AM radio– DAB is a broadband system carrying multiple radio
services (and video services)
• Some broadcasters will use DAB or DRM– others will use both DAB and DRM
College of Engineering, Thiruvananthapuram
ADVANTAGES OF DRM
• DRM signals fit within the 9 kHz or 10 kHz channels used by traditional AM signals – simplifying frequency planning– permitting existing AM transmitters to be
reused for digital radio services with relatively minor modifications
• Broadcasters are attracted by the re-use of expensive hardware, such as high power transmitters and transmitting antennas College of Engineering,
Thiruvananthapuram
DRM .. advantagesDRM .. advantages
• Large coverage areas • Four operating modes for reliability:- Ground
wave mode, Sky wave mode, Highly robust modes 1 and 2
• Superior sound quality with AM reach • No change in listening conditions• Easy receiver tuning : by frequency, station
name or program
College of Engineering, Thiruvananthapuram
DRM FeaturesDRM Features
• Non proprietary standards
• Compatibility with existing AM channels
• Workable migration from analog to fully digital
• Multi mode operation depending propagation
• Provision for Data broadcasting
• SFN capabilityCollege of Engineering, Thiruvananthapuram
College of Engineering, Thiruvananthapuram
College of Engineering, Thiruvananthapuram
DRM System ArchitectureDRM System Architecture
Audio data
stream
Source
Encoder(s)
Data
stream
Source
Encoder(s)M
ultip
lexe
r
Energy
dispersal
Channel
encoder
Cell inter-
leaver
OF
DM
cel
l map
per
OFDM
Modulator
Pilot
generator
Coder,interleaver Energy dispersal
Coder,interleaver Energy dispersal
FAC
information
SDC
information
MSC
Signal Out
College of Engineering, Thiruvananthapuram
DRM MultiplexDRM Multiplex
Up to 4 Audio +Data
Channel parameters, Spectrum,modulation
interleaving….
Multiplex,CA,freq, schedule,time/date, region, coding,SBR,
PAD,Mod etc
MSC
FAC
SDC
MULTIPLEX
To OFDM
College of Engineering, Thiruvananthapuram
Source CodingSource Coding
AACStereo
HigherBit-rates-48 kbps
Audiosignal
SBR
AudioSuper
framing
Mux
& c
hann
el c
odin
g
AACStereo
NarrowbandCELP
NarrowbandCELP
StandardMode -20 kbps
Ultra robustMode-10 kbps
Low bitrateMode 8 kbps
College of Engineering, Thiruvananthapuram
Frame structureFrame structure
Frequency
Kernel carriers4.5kHz for FACin every frame
SDC2 OFDM symbols
Time
Core partOf SDC
Additional partsOf SDC
Frame400ms
Super-frame 1200ms
Frame 400ms
Frame 400ms
1 2 3
College of Engineering, Thiruvananthapuram
For this, there are the following properties:Frame length: 40 msAAC sampling rate: 24 kHzSBR sampling rate: 48 kHzAAC frequency range: 0 – 6.0 kHzSBR frequency range: 6.0 – 15.2 kHzSBR average bit rate: 2 kb/s per channelCollege of Engineering,
Thiruvananthapuram
DRM-Modes
Mode A B C DExpectedModulation
64QAM 64/16QAM 16QAM 64/16QAM
TypicalApplication
Groundwave
(MW,LW)
Sky-wave(MW, SW)
Difficultsky-wave
(SW)
Verticalincidence
(SW)Interleave Short Long Long Longest
Bit rate High Medium Med/Low Low
AudioQuality
High Medium Med/Low Low
Robustness Medium High High/V.High Very High
College of Engineering, Thiruvananthapuram
Guard Interval for different ServicesGuard Interval for different Services• System immunity against Fading, Doppler effect• For SFN Operation
Parameter MW SW
Duration Tu 24ms 21.33ms
Carrier spacing1/Tu
41 2/3 46 7/8Hz
Guard interval Tg 2.66ms 26.66ms
Tg/Tu 1/9 ¼
Symbols/frame 15 15
College of Engineering, Thiruvananthapuram
ImplementationImplementation
• Need a DRM exciter to generate QAM-COFDM symbols, in I and Q Channel
• Need a Digital Frequency Synthesizer to phase and amplitude modulate the carrier
• Linear amplifiers can take these signals directly • Non Linear older transmitters need to be linearised
or are to be modulated separately in amplitude and phase
• New MW transmitters using digital modulation techniques can easily take DRM.
College of Engineering, Thiruvananthapuram
Implementing DRM in Linear Implementing DRM in Linear TransmittersTransmitters
DRM Digital
Modulator
Digital RF
Synthesizer
Output
RF Circuits
Linear RF AmplifierTo
Antenna
RF Amplifier
Pre-amplifier
I
Ph
ase
an
d A
mp
litu
de
Mo
du
late
d R
F
Q
Audio + Data
College of Engineering, Thiruvananthapuram
Implementing DRM in Non-Linear Implementing DRM in Non-Linear TransmittersTransmitters
Digital
Pre-correction
Digital RF
Synthesizer
Digital
Demodulator
High Level
Modulator
Output
RF Circuits
Modulated HV
To Antenna
RF Amplifier
Corrected
I
Corrected
Q
I
Q
I DemodulatedQ Demodulated
Modulated
RF Sample
Corrected Amplitude
DRM Digital
Modulator
Digital RF
Synthesizer
I Q
Audio + Data
College of Engineering, Thiruvananthapuram
Other implementation issuesOther implementation issues
• Flat Spectrum response of the output circuit of transmitters
• Non uniform Phase change in amplifiers
• Antenna Tuning unit band width
• Band width of antenna( wide-band/dual band)
• Matching system / VSWR
College of Engineering, Thiruvananthapuram
College of Engineering, Thiruvananthapuram
College of Engineering, Thiruvananthapuram
College of Engineering, Thiruvananthapuram
College of Engineering, Thiruvananthapuram
College of Engineering, Thiruvananthapuram
College of Engineering, Thiruvananthapuram
College of Engineering, Thiruvananthapuram
ADVANCEMENT
The DRM consortium voted in March 2005 to begin
the process of extending the system to the
Broadcasting Bands up to 120 MHz
The design development and testing phase are
expected to be completed by 2007 – 2009
College of Engineering, Thiruvananthapuram
CONCLUSIONS
• Digital Radio Mondiale has achieved great technical success in developing the DRM system
• Synergy between DAB and DRM must be exploited
• The big challenge is now to achieve successful implementation– persuading broadcasters– persuading regulators– persuading receiver manufacturers– persuading consumers
College of Engineering, Thiruvananthapuram