Fm Stereo/Rds Concepts; Fm Stereo; Rds/Rbds - Keysight X-Series Measurement Manual

Concepts

FM Stereo/RDS Concepts

FM Stereo/RDS Concepts

FM stereo is an enhancement of FM using stereo multiplexing. An FM stereo
signal carries stereophonic programs in which different contents are
transmitted for L (left) and R (right) audio channels.
RDS (Radio Data System) is the text information such as traffic, weather, and
radio station information carried in FM signals. This information can be
displayed on the screen of the end-user's device.
The following figure shows the baseband spectrum of the FM stereo signal
including RDS data.
Figure 2-5 Baseband spectrum of the FM Stereo/RDS signal

FM Stereo

The FM stereo multiplexed signal consists of a mono (L+R) signal, a stereo
(L-R) signal, and a pilot signal.
As shown in Figure 2.5, the mono (L+R) signal occupies the lower part of the
baseband spectrum (50 Hz ~ 15 kHz) to keep backward compatibility with the
previously monophonic FM systems. The (L-R) signal is amplitude modulated
onto a suppressed subcarrier at 38 kHz. A pilot signal is transmitted at 19 kHz
and is used by the receiver to identify a stereo transmission and reconstruct L
and R audio signals from the multiplexed signal.
In the receiver, the (L+R) signal is added to the (L-R) signal to get the L signal,
and subtracts the (L-R) signal to get the R signal.

RDS/RBDS

The standard documents for RDS and RBDS are as follows:
— IEC 62106: Specification of the radio data system (RDS) for VHF/FM sound
— EIA/NAB NRSC: United States RBDS standard - Specification of the radio
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broadcasting in the frequency range from 87.5 to 108.0 MHz.
broadcast data system (RBDS).
Keysight N9063C Analog Demod Measurement Guide