Keysight N9063C Analog Demod Measurement Guide 31
Concepts
FM Stereo/RDS Concepts
RBDS is the United States version of RDS. Both RDS and RBDS are intended
for application to VHF/FM sound broadcasts in the range 87.5 MHz to 108.0
MHz which may carry either stereophonic or monophonic programs.
The main objectives of RDS/RBDS:
— To enhance functionality for FM receivers;
— To make the receivers more user-friendly by using features such as PI
(program identification), PS (program service) name display, and if
applicable, automatic tuning for portable and car radios.
As shown in
, RDS/RBDS uses the 57 kHz subcarrier to carry the
data at 1.1875 kbps bitrate. The 57 kHz is chosen to be the third harmonic of
the pilot tone. The deviation range of the FM carrier due to the unmodulated
RDS/RBDS subcarrier is from ±1.0 kHz to ±7.5 kHz.
Basic Structure of RDS
The basic structure of RDS is shown in
, in which the largest element
is called a group including 4 blocks of 26 bits each. Each block comprises an
information word (16 bits) and a checkword (10 bits).
The information word is used to transmit information to the end user. The
10-bit checkword plus offset word are used to provide error protection and
block and group synchronization information.
Figure 2-6
Basic structure of RDS
BLER
BLER (block error rate) is the ratio of the number of un-correctable blocks to
the total number of blocks received. Normally, BLER should be less than 5%.
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