Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04H—BROADCAST COMMUNICATION
  • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
  • H04H20/28—Arrangements for simultaneous broadcast of plural pieces of information
  • H04H20/33—Arrangements for simultaneous broadcast of plural pieces of information by plural channels
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04H—BROADCAST COMMUNICATION
  • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
  • H04H20/20—Arrangements for broadcast or distribution of identical information via plural systems
  • H04H20/22—Arrangements for broadcast of identical information via plural broadcast systems
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04H—BROADCAST COMMUNICATION
  • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
  • H04H20/28—Arrangements for simultaneous broadcast of plural pieces of information
  • H04H20/36—Arrangements for simultaneous broadcast of plural pieces of information for AM broadcasts
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04H—BROADCAST COMMUNICATION
  • H04H2201/00—Aspects of broadcast communication
  • H04H2201/10—Aspects of broadcast communication characterised by the type of broadcast system
  • H04H2201/18—Aspects of broadcast communication characterised by the type of broadcast system in band on channel [IBOC]
  • H04H2201/186—AM digital or hybrid
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04H—BROADCAST COMMUNICATION
  • H04H2201/00—Aspects of broadcast communication
  • H04H2201/10—Aspects of broadcast communication characterised by the type of broadcast system
  • H04H2201/20—Aspects of broadcast communication characterised by the type of broadcast system digital audio broadcasting [DAB]

Definitions

• the present invention is related to an AM simulcast broadcast signal combining a digital transmission signal and an analogue transmission signal in one transmission channel, a method to generate such a signal, and an AM simulcast broadcast signal generator embodying said method.
• DRM Digital Radio Mondeal
• a simultaneous transmission of the conventional analogue and the new digital service will simplify and accelerate the introduction of the DRM system, since listeners of the analogue service are not lost during the introduction of DRM.
• a simulcast technology is already known for AM bands.
• the first known possibility is to use a half channel analogue DSB (Double Sideband Modulation), and a half channel digital DSB.
• the disadvantage is that audio bandwidth for the analogue signal is reduced by 50 %, a crosstalk from the digital half channel to the analogue half channel exists, and existing analogue receivers which do not use modern technology, i. e. which use standard filters, get distorted.
• the second known possibility is the IBOC (In Band On Channel) system, wherein the digital signal is modulated orthogonal to the unchanged analogue signal.
• the disadvantage is a significantly increased dynamic range which is required in the digital receiver, that crosstalk from the analogue signal to the digital signal and vice versa exists, and that the digital and the analogue systems get distorted.
• an AM simulcast broadcast signal combining a digital transmission signal and an analogue transmission signal in one transmission channel according to independent claim 1. Further, a method to generate such an AM simulcast broadcast signal which solves this object is defined in independent claim 6. Furthermore, an AM simulcast broadcast signal generator which solves said object is defined in independent claim 11. computer program product solving said object is defined in claim 19. Prefer- red embodiments of the broadcast signal, the method to generate said broadcast signal, and the appropriate broadcast generator are respectively defined in the respective following dependent claims.
• the AM simulcast broadcast signal combining a digital transmission signal and an analogue transmission signal in one transmission channel is built so that the digital transmission signal is modulated to one sideband of a carrier of the transmission channel and a correcting signal is modulated to the other sideband of the carrier of the transmission channel, which correcting signal is determined in a way that the envelope demodulation of the transmission channel represents the analogue transmission signal.
• This AM simulcast broadcast signal allows the reception of the analogue signal with unchanged audio bandwidth while introducing a digital signal into the same frequency slot.
• the analogue signal continues to be receivable with a simple envelope detector. Further, no crosstalk from the analogue signal to the digital signal exists and crosstalk distortions from the digital signal to the analogue signal exists only in AM receivers with low-quality, asymetrical, IF (Intermediate Frequency) filter characteristics. Furthermore, a full compatibility to the existing AM system is given and a full audio bandwidth of 5 kHz can be assured.
• said correcting signal is generated in an iterative process according to which
• an error signal is generated by subtracting the envelope demodulated simulcast signal from the analogue transmission signal which is delayed according to the processing time to generate and demodulate the simulcast signal
• the error signal is weighted with a time-variant or time-invariant variable
• a new analogue transmission signal is generated by adding the weighted error signal to the delayed analogue transmission signal
• the digital transmission signal is delayed corresponding to the delay of the analogue transmission signal, wherein the whole procedure is repeated N times with another time-variant or time-invariant variable and with the newly generated analogue transmission signal as said analogue transmission signal, wherein N is a positive integer including zero and is determined according to the wanted accuracy of the correcting signal which is determined as the newly generated analogue transmission signal after the N iteration.
• the method to generate an AM simulcast broadcast signal combining a digital transmission signal and an analogue transmission signal in one transmission channel comprises the steps of modulating the digital transmission signal to one sideband of a carrier of the transmission channel, and modulating a correcting signal to the other sideband of the carrier of the transmission channel, which correcting signal is determined so that the envelope demodulation of the transmission channel represents the analogue transmission signal.
• the step of generating said correcting signal is perfoprmed in an iterative process with the steps of:
• N is a positive integer including zero and is determined according to the wanted accuracy of the correcting signal which is determined as the newly generated analogue transmission signal after the N iteration.
• the correcting signal is preferrably generated in an iterative process wherein the final correcting signal is determined on basis of an error signal between an analogue transmission signal which is recalculated based on a simulcast signal generated with an assumed or intermediate correcting signal and the analogue transmission signal which should actually be transmitted.
• An AM simulcast broadcast signal generator for a transmission of a digital transmission signal and an analogue transmission signal in one transmission channel comprises a first modulator to modulate the digital transmission signal to one sideband of a carrier of the transmission channel, and a second modulator to modulate a correcting signal to the other sideband of the carrier of the transmission channel, which correcting signal is determined so that the envelope demodulation of the transmission channel represents the analogue transmission signal.
• the broadcast signal generator according to the present invention further comprises a first adder to add said both sidebands and a carrier signal at the centre of both sidebands.
• the broadcast signal generator according to the present invention further comprises a correcting signal generator comprising:
• said correcting signal generator within the broadcast signal generator according to the present invention further comprises N correcting signal units respectively comprising:
• N is a positive integer including zero and is determined according to the wanted accuracy of the correcting signal which is determined after the N th correcting signal unit.
• said N correcting signal units within said correcting signal generator respectively further comprise:
• said N correcting signal units within said correcting - signal generator respectively further comprise:
• a DRM signal is transmitted as said digital transmission signal.
• digital transmission signals generated according to other standards might be transmitted.
• a conventional AM signal is transmitted as said AM analogue transmission signal.
• Fig. 1 shows an AM simulcast broadcast signal generator according to the present invention
• Fig. 2 shows the spectrum of the simulcast signal according to the present invention.
• the digital and the analogue signal are combined in one channel.
• the digi- tally modulated signal is transmitted in one sideband of the channel which allows a distortion-free demodulation of the digital modulated signal in the receiver.
• the simulcast signal is backward compatible with the existing AM broadcast system, since the envelope of the simulcast signal ideally represents the analogue signal.
• the backward compatibility of the simulcast signal is assured by a modulation of the unmodulated sideband of the AM channel with a correcting signal C.
• the spectrum of the simulcast signal according to the present invention is shown in Fig. 2.
• the upper sideband of the channel comprises the digitally modulated signal, e. g. the DRM signal
• the lower sideband comprises the correcting signal C.
• a carrier is added so that an estimation of the simulcast signal can be obtained.
• the digitally modulated signal is transmitted in the lower sideband of the channel and the correcting signal is transmitted in the upper sideband thereof.
• the envelope demodulation of the simulcast signal according to the present invention results in the undisturbed analogue audio signal with the full audio bandwidth.
• the audio bandwidth of the analogue signal is 5 kHz. Therefore, the audio bandwidth is not changed by the simulcast signal according to the present invention.
• the audio signal contains distortions only in case of channel distortions or distortions of the frequency response of the analogue AM/IF filter, i. e. in case of a AM receiver with low-quality, asymetrical, IF (Intermediate Frequency) filter characteristics.
• the digital modulated DRM signal is not disturbed by the analogue signal.
• the generation of the correcting signal C is preferably an iterative process.
• Such an iterative method might modulate the DRM signal to the upper sideband and the analogue signal to the lower sideband or vice versa.
• the carrier is added at the center of both sidebands to get an estimation of the simulcast signal.
• the estimation of the full simulcast signal comprising upper sideband USB, lower sideband LSB and carrier, is demodulated by an envelope demodulator. Thereafter, the envelope demodulated analogue signal is subtracted from the analogue signal to get an error signal.
• the error signal is followingly weighted with a constant k before, at the next stage, the error signal is added to the analogue signal to get a new estimation of the LSB signal representing the analogue audio signal. This iteration is repeated N times, until the correcting signal C is obtained and the simulcast signal according to the present invention is generated and transmitted.
• the constant k might also be variable depending on the amplitude of the analogue signal and/or digital signal and/or the error signal.
• Fig. 1 shows an exemplary AM simulcast broadcast generator according to a preferred embodiment of the present invention.
• the simulcast broadcast signal according to the present invention is generated by a first modulator 1 which modulates the digital transmission signal to one sideband of a carrier of the transmission channel, here the upper sideband USB, and a second modulator 2 which modulates the correcting signal C to the upper sideband of the carrier of the transmission channel, here to the lower sideband LSD.
• a first adder 3 adds said both sidebands and possibly the carrier signal at the center of both sidebands, which carrier signal is generated by a carrier signal generator 4.
• the digital transmission signal supplied to the first modulator 1 corresponds to the correcting signal C in time, i. e. is delayed during the generation of the correcting signal C to match therewith.
• the broadcast signal generator according to the present invention shown in Fig. 1 comprises a correcting signal generator which - in this case - also delays the digital signal.
• the correcting signal generator comprises a third modulator 5 to modulate said digital transmission signal to said one sideband, i. e. here to the upper sideband, a fourth modulator 6 to modulate the analogue transmission signal to the other sideband, here the lower sideband, a second adder 7 to add said both sidebands and the carrier signal which is generated by a second carrier signal generator 8 at the center of said both sidebands.
• the correcting signal generator comprises a first envelope demodulator 9 to envelope demodulate the so generated simulcast signal, a first delay element 10 to delay the analogue transmission signal according to the processing time to generate a demodulated respective simulcast signal, a first subtractor 1 1 to generate an error signal by subtracting the envelope demodulated simulcast signal from the delayed analogue transmisson signal, a first multiplier 12 to weight the error signal with a time- variant or time-invariant variable, a third adder 13 to generate the correcting signal C or an intermediate correcting signal by adding the weighted error signal to the delayed analogue transmission signal, and a second delay element to delay the digital transmission signal according to the processing time needed to generate and demodulate the respective simulcast signal.
• these elements of the correcting signal generator which can be regarded as one correcting signal unit either generate the correcting signal or an intermediate correcting signal.
• the correcting signal generated by this one correcting signal unit is normally only a rough, estimation and would not necessarily lead to a proper transmission to the analogue transmission signal. However, the quality thereof might also be regarded as sufficient. In case this should not be sufficient, the resulting signal supplied from the third adder 13 might be processed in the same way as the analogue transmission signal was processed before by N similar following correcting signal unit(s). In this case also the digital transmission signal will get accordingly delayed. Such a repetition of the processing might be performed N times, i. e. by N similar following correcting signal unit(s), wherein N is a positive integer including zero and is determined according to the wanted accuracy of the correcting signal which is determined after the N th correcting signal unit.

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• Engineering & Computer Science (AREA)
• Signal Processing (AREA)
• Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
• Transmitters (AREA)
• Circuits Of Receivers In General (AREA)

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Citations (3)

• 2003
  • 2003-01-10 WO PCT/EP2003/000188 patent/WO2004064275A1/en active Search and Examination
  • 2003-01-10 BR BR0317969-9A patent/BR0317969A/pt not_active IP Right Cessation
  • 2003-01-10 KR KR1020057012814A patent/KR100941823B1/ko not_active IP Right Cessation
  • 2003-01-10 AU AU2003201960A patent/AU2003201960A1/en not_active Abandoned
  • 2003-01-10 CN CNB038257769A patent/CN100502263C/zh not_active Expired - Fee Related

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