chips has been programmed and
customized to perform all of the
needed DSP functions for HD Radio.
The most recent version is called the
TI TMS320DRI250. The DSP chip
handles all of the filtering, error
detection and correction, demodulation, de-interleaving, and other stuff.
The demodulation process uses the
fast Fourier transform (FFT).
The final decoding and decompression produces the original serial
digital audio at the standard 44.1
kHz CD rate. This signal then goes
back to the converter chip, where it
is translated back to analog into two
DACs and sent to the external stereo
audio power amplifiers.
As of the first of the year, over
300 stations have signed up for HD
Radio licenses. Only about 70 are
currently on the air. The majority of
major cities have at least one station
in operation; most of these are FM
stations. Also, HD Radio receivers —
primarily car radios — are available.
Kenwood was the first on the market,
but Panasonic, JVC, and Harmon
Figure 3. A general block diagram of an HD Radio receiver.
Cardon will also have units available
soon. You can get these receivers at
Best Buy, Circuit City, and a few
other electronic stores.
As for the impact of HD Radio
on standard analog AM and FM, as
well as the newer digital satellite
services, that remains to be seen.
The plan is for HD Radio to eventually
evolve into the all digital mode.
Progress will, no doubt, be made, but
the evolution will take time. Look how
long it is taking for HDTV — which
has been around for years — to come
online. Will it ever replace regular TV?
HD Radio will certainly be a
source of concern for the newer
satellite radio services, like Sirius and
XM. Because it is free (excluding the
cost of a new receiver), it will get lots
of attention. Yet, it will take years
before many stations are available.
Of course, both Sirius and XM offer
100 channels of music, talk, news,
sports, and more right now, but for a
subscription price. Both of those
services are available continuously
across the US, where AM and FM
stations are strictly local, fading in
and out as you travel. It looks to me
like we will have lots of options over the
coming years, as all of these services
continue to serve their niches. NV
NUTS & VOLTS
If you are looking for more
in-depth information on HD Radio,
check into these sites:
Ibiquity Digital Corporation
National Association of Broadcasters
National Radio Systems Committee
(Eureka 147 DAB DSP software)
Texas Instruments, Inc.