Keysight N9030A Measurement Manual

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Contents

Keysight N9030A Measurement Manual Manual pdf 30 page image

30ConceptsFM Stereo/RDS ConceptsFM Stereo/RDS ConceptsFM stereo is an enhancement of FM by using stereo multiplexing. An FM stereosignal carries stereophonic programmes in which different contents are transmittedfor L (left) and R (right) audio channels.RDS (Radio Data System) is the text information such as traffic, weather, and radiostation information carried in FM signals. This information can be displayed on thescreen of the end-user’s device.Figure 2-5 shows the baseband spectrum of the FM stereo signal including RDSdata.Figure 2-5 Baseband spectrum of the FM Stereo/RDS signalFM StereoThe 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 thebaseband spectrum (50 Hz ~ 15 kHz) to keep backward compatibility with thepreviously monophonic FM systems. The (L-R) signal is amplitude modulated ontoa suppressed subcarrier at 38 kHz. A pilot signal is transmitted at 19 kHz and is usedby the receiver to identify a stereo transmission and reconstruct L and R audiosignals from the multiplexed signal.In the receiver, the (L+R) signal is added to the (L-R) signal to get the L signal, andsubtracts the (L-R) signal to get the R signal.RDS/RBDSThe standard documents for RDS and RBDS are as follows:• IEC 62106: Specification of the radio data system (RDS) for VHF/FM soundbroadcasting in the frequency range from 87.5 to 108.0 MHz.• EIA/NAB NRSC: United States RBDS standard - Specification of the radiobroadcast data system (RBDS).Frequency (kHz)MonosignalL+R15 19Pilot38 57RDS/RBDSStereo signalL-RAmplitude