KR100941823B1 - Drm/am simulcast - Google Patents

Abstract

The AM simultaneous broadcast signal combines a digital transmission signal and an analog transmission signal into one transmission channel. The digital transmission signal is modulated with one side wave of the carrier of the transmission channel, the correction signal C is modulated with the other side wave of the carrier of the transmission channel, and the correction signal such that the envelope demodulation of the transmission channel represents an analog transmission signal. (C) is determined.

Digital Transmission Signals, Analog Transmission Signals, Envelope Demodulation, AM Simultaneous Transmission, Transmission Channel

Description

DRM / AM simultaneous transmission {DRM / AM SIMULCAST}

The present invention relates to an AM simulcast broadcast signal combining a digital transmission signal and an analog transmission signal into one transmission channel, a method for generating such a signal, and an AM simultaneous broadcast signal generator for implementing the method.

Digital Radio Mondeal (DRM) is a digital service in the broadcast band below 30MHz. Since listeners of analog services were not interested during the introduction of DRM, conventional analog simultaneous transmission and new digital services have simplified and facilitated the introduction of DRM systems.

Basically, simultaneous transmission techniques are already known with regard to AM bands. A first known possibility is to use half channel analog double sideband modulation (DSB), and half channel digital DSB. The audio bandwidth for analog signals is reduced by 50%, there is crosstalk noise from the digital half channel to the analog half channel, and distortions occur in conventional analog receivers that do not use the latest technology using standard filters. It's a downside. A second known possibility is an In Band On Channel (IBC) system, where the digital signal is orthogonally modulated with respect to the invariant analog signal. Their disadvantage is the significantly increased dynamic range required in digital receivers, crosstalk from analog signals to digital signals and vice versa, and distortion in digital and analog systems.

Therefore, it is an object of the present invention to define a new method for simultaneous transmission of digital and analog transmission signals on the same channel.

This object is solved by an AM simultaneous broadcast signal which combines a digital transmission signal and an analog transmission signal into one transmission channel, according to claim 1. In addition, a method for generating an AM simultaneous broadcast signal lamp that solves this purpose is defined in the independent claim. In addition, an AM simultaneous broadcast signal generator that solves this object is defined in the independent claim 11. A computer program product for solving this purpose is defined in claim 17. Preferred embodiments for a broadcast signal, a method for generating the broadcast signal, and a suitable broadcast signal generator are each defined in the following dependent claims.

 The digital transmission signal is modulated on one side of the carrier of the transmission channel, and the correcting signal is modulated on the other side of the carrier of the transmission channel, where the correction signal is analog to the envelope demodulation of the transmission channel. In accordance with the present invention, an AM simultaneous broadcast broadcast signal is constructed which combines a digital transmission signal and an analog transmission signal in one transmission channel so as to be determined in a manner representing the transmission signal.

The AM simultaneous broadcast broadcast signal according to the present invention allows the reception of analog signals with invariant audio bandwidth while introducing digital signals into the same frequency slots. The analog signal can be continuously received as a simple envelope detector. In addition, there is no crosstalk from the analog signal to the digital signal and crosstalk distortion from the digital signal to the analog signal exists only in an AM receiver having a low quality, asymmetric, IF (intermediate frequency) filter characteristic. In addition, full compatibility with existing AM systems is given, and a full audio bandwidth of 5 kHz can be guaranteed.

Further preferably, in the AM simultaneous broadcast broadcast signal according to the present invention, the correction signal is generated by the following iterative process.

The digital transmission signal is modulated with the one sideband,

The analog transmission signal is modulated with the other sideband,

Both the sidebands are added and the carrier signal is added in the middle of the two sidebands,

-Envelope demodulation is performed on the generated simultaneous transmission signal,

An error signal is generated by subtracting the envelope demodulation simultaneous transmission signal from the delayed analog transmission signal in accordance with a processing time for generating and demodulating the simultaneous transmission signal,

Error signals are weighted according to time-varying or time-invariant variables,

A new analog transmission signal is generated by adding the weighted error signal to the delayed analog transmission signal,

The digital transmission signal is delayed corresponding to the delay of the analog transmission signal,

Here, the whole procedure is repeated N times according to another time-varying or time-invariant variable and the newly generated analog transmission signal as the analog transmission signal, where N is a positive integer including 0 and after the Nth iteration the newly generated It is determined by the desired accuracy of the correction signal determined by the analog transmission signal.

According to the present invention, a method for generating an AM simultaneous broadcast signal combining a digital transmission signal and an analog transmission signal into one transmission channel includes modulating the digital transmission signal into one side wave of a carrier of the transmission channel, and Modulating the correction signal with the other side of the carrier of the transmission channel, wherein the correction signal is determined such that the envelope demodulation of the transmission channel represents an analog transmission signal.

Further preferably, in the method according to the invention, the step for generating the correction signal is

Modulating the digital transmission signal with the one sideband,

Modulating the analog transmission signal with the other sideband,

Adding the two sidebands and the carrier signal at the center of the two sidebands,

Envelope demodulating the generated simultaneous transmitted signal,

Generating an error signal by subtracting the envelope demodulated simulcast signal from a delayed analog transmission signal according to a processing time for generating and demodulating the simulcast signal;

Weighting the error signal with a time varying or time invariant variable,

Adding the weighted error signal to the delayed analog transmission signal to generate a new analog transmission signal,

-Delaying said digital transmission signal in response to a delay of said analog transmission signal,

The entire procedure is repeated N times according to another time-varying or time-invariant variable and the analog transmission signal newly generated as the analog transmission signal,

N is a positive integer including 0 and is determined according to the desired accuracy of the correction signal C, which is determined according to the newly generated analog transmission signal after the Nth iteration.

Thus, according to the invention, the correction signal is preferably generated by an iterative process, where the final correction signal is compared with the analog transmission signal recalculated based on the simultaneous transmission signal generated according to the estimated or intermediate correction signal. It is determined based on the error signal between the analog transmission signals actually transmitted.

According to the present invention, an AM simultaneous broadcast signal generator for transmitting a digital transmission signal and an analog transmission signal in one transmission channel comprises: a first modulator for modulating the digital transmission signal into one side wave of a carrier wave of the transmission channel; And a second modulator for modulating a correction signal onto another side of the carrier of the transmission channel, wherein the correction signal is determined such that envelope demodulation of the transmission channel represents the analog transmission signal.

Preferably, the broadcast signal generator according to the present invention further comprises a first adder for adding carrier signals at the center of the two sidebands and the two sidebands.

More preferably, the broadcast signal generator according to the present invention,

A third modulator for modulating the digital transmission signal into the one sideband,

A fourth modulator for modulating the analog transmission signal onto the other sideband,

A second adder for adding the two sidebands,

A first envelope demodulator for envelope demodulating the generated simultaneous broadcast signal,

A first delay element for delaying said analog transmission signal in accordance with a processing time for generating and demodulating said respective simultaneous transmitted signal,

A first subtractor for generating an error signal by subtracting the envelope demodulated simultaneous broadcast signal from the delayed analog transmission signal,

A first multiplier for weighting the error signal according to a time varying or time invariant variable,

A third adder for adding the weighted error signal to the delayed analog transmission signal to produce the correction signal or an intermediate correction signal,

And a correction signal generator comprising a second delay element for delaying the digital transmission signal in accordance with processing time for generating and demodulating the respective simultaneous transmitted signal.

More preferably, the correction signal generator in the broadcast signal generator according to the present invention,

A fifth modulator for modulating the intermediate correction signal onto the other sideband,

A fourth adder for adding the two sidebands,

A second envelope demodulator for envelope demodulating the generated simultaneous broadcast signal,

A third delay element for delaying said intermediate correction signal in accordance with a processing time for generating and demodulating said respective outgoing signal,

A second subtractor for generating an error signal by subtracting the envelope demodulated simultaneous transmit signal from the delayed intermediate correction signal,

A second multiplier for weighting the error signal according to a time varying or time invariant variable,

Further comprising N correction signal units each including a fifth adder for adding the weighted error signal to the delayed intermediate correction signal to produce the correction signal or the intermediate correction signal,

Here, N is a positive integer including 0 and is determined according to the desired accuracy of the correction signal determined after the Nth correction signal unit.

More preferably, the N correction signal units in the correction signal generator are:

A fifth modulator for modulating the delayed digital transmission signal into the one side wave,

Each further comprising a fourth delay element for delaying said digital transmission signal in accordance with a processing time for generating and demodulating said respective simultaneous transmitted signal.

Here, alternatively, the N correction signal units in the correction signal generator are:

And further comprising a fourth delay element for delaying said digital transmission signal modulated with said one sideband in accordance with processing time for generating and demodulating said respective simultaneous transmitted signal.

According to the invention, preferably the DRM signal is transmitted in accordance with the digital transmission signal. However, digital transmission signals generated according to other standards can also be transmitted.

According to the invention, preferably, a normal AM signal is transmitted in accordance with said AM analog transmission signal.

Other objects and features of the DRM / AM simultaneous delivery system according to the present invention will become apparent in accordance with the description of the following exemplary embodiments in conjunction with the accompanying drawings.

1 is a diagram showing an AM simultaneous broadcast signal generator according to the present invention;

2 is a diagram showing a spectrum of a simultaneous transmission signal according to the present invention.

According to the invention, the digital and analog signals are combined into one channel. To prevent distortion of the digital system, the digitally modulated signal is transmitted in one sideband of the channel allowing distortion-free demodulation of the digitally modulated signal in the receiver.

Also, since the envelope of the simultaneous broadcast signal ideally represents an analog signal, the simultaneous broadcast signal is backward compatible with existing AM broadcast systems. According to the present invention, backward compatibility of the simultaneous outgoing signal is ensured by modulating the unmodulated sideband of the AM channel with the correction signal. The spectrum of the simultaneous transmission signal according to the invention is shown in FIG. The upper sideband of this channel contains a digitally modulated signal, such as a DRM signal, and the lower sideband contains a correction signal C. At the center of these two sidebands, carriers can be added to obtain an estimate of the simultaneous outgoing signal. Of course, it is also possible for the digitally modulated signal to be transmitted in the lower sideband of the channel and the correction signal to be transmitted in the upper sideband of the channel.

Envelope demodulation of the simultaneous outgoing signal according to the invention results in an undisturbed analog audio signal with a full audio bandwidth. In the case of a 10 kHz AM channel, the audio bandwidth of the analog signal is 5 kHz. Thus, the audio bandwidth does not change with the simultaneous outgoing signal according to the present invention.

The audio signal contains distortion only in the case of channel distortion or distortion in the frequency response of the analog AM / IF filter, ie in the case of low quality, asymmetric, IF (intermediate frequency) filter characteristics.

Digitally modulated DRM signals are not disturbed by analog signals.

The correction signal C is preferably generated by an iterative process. This iterative method modulates the DRM signal into the upper sideband, and the analog signal into the lower sideband or vice versa. Next, a carrier is added at the center of two sidebands to obtain an estimate of the simultaneous transmission signal. The estimation of the complete simultaneous transmitted signal including the upper sideband USB, the lower sideband LSB and the carrier is demodulated by an envelope demodulator. Thus, the envelope demodulated analog signal is subtracted from the analog signal to obtain an error signal. The error signal is weighted to a constant k before the next step, and then the error signal is added to the analog signal to obtain a new estimate of the LSB signal representing the analog audio signal. This iteration is repeated N times until a correction signal C is obtained and a simultaneous transmission signal according to the invention is generated and transmitted.

The constant k may be a variable based on the amplitude of the analog and / or digital and / or error signals.

1 illustrates an exemplary AM simultaneous broadcast signal generator in accordance with a preferred embodiment of the present invention. The simultaneous broadcast broadcast signal according to the present invention includes a first modulator 1 for modulating a digital transmission signal according to one side wave of a carrier of a transmission channel that is an upper sideband USB and a lower side of a carrier of a transmission channel that is a lower sideband LSD. It is generated by the second modulator 2 which modulates the correction signal C as a wave.

Further, in order to generate a simultaneous broadcast signal according to the invention, the first adder 3 adds a carrier signal at the center of the two sidebands and possibly the two sidebands, the carrier signal being a carrier wave. It is generated by the signal generator 4.

The digital transmission signal supplied to the first modulator 1 corresponds to the correction signal C in time, ie it is delayed during the generation of the correction signal C to match with it.

The broadcast signal generator of the present invention shown in Fig. 1 also includes a correction signal generator for delaying the digital signal in this case. The correction signal generator includes a third modulator 5 for modulating the digital transmission signal with one sideband as the upper sideband and a fourth modulator 6 for modulating the analog transmission signal with the other sideband as the lower sideband; And a second adder 7 for adding the carrier signals generated by the second carrier signal generator 8 at the center of the sidebands and the two sidebands. Further, the correction signal generator is further configured to delay the analog transmission signal in accordance with a first envelope demodulator 9 for envelope demodulating the generated simultaneous transmitted signal, and processing time for generating and demodulating the respective simultaneous transmitted signal. A first delay element 10 for subtracting the envelope demodulated simultaneous transmission signal from the delayed analog transmission signal and a first subtractor 11 for generating an error signal according to a time varying or time invariant variable A first multiplier (12) for weighting, a third adder (13) for adding the weighted error signal to the delayed analog transmission signal to produce the correction signal (C) or an intermediate correction signal; And a second delay element for delaying the digital transmission signal in accordance with a processing time for generating and demodulating the respective simultaneous transmitted signal.

As mentioned above, an element of such a correction signal generator, which can be regarded as one correction signal unit, may generate a correction signal or generate an intermediate correction signal. The correction signal produced by one such correction signal unit is typically only rough estimation and does not necessarily lead to proper transmission to the analog transmission signal. However, their quality can be considered sufficient. If this is not sufficient, the resulting signal supplied from the third adder 13 can be processed in the same way as the analog transmission signal was previously processed by the N similar next correction signal unit (s). . In this case, the digital transmission signal may also be delayed accordingly. The repetition of this process may be performed N times, i.e. by N next correction signal unit (s), where N is a positive integer containing 0 and the correction determined after the Nth correction signal unit. It is determined according to the desired accuracy of the signal C.

Claims (17)

delete delete delete delete A method for generating an AM simultaneous broadcast signal combining a digital transmission signal and an analog transmission signal into one transmission channel, Modulating the digital transmission signal into one sideband of a carrier of the transmission channel; And Modulating a correction signal (C) with another sideband of the carrier of the transmission channel, And said correction signal (C) is determined so that envelope demodulation of said transmission channel represents said analog transmission signal. The method of claim 5, The correction signal (C), (a) modulating the digital transmission signal with the one side wave; (b) modulating the analog transmission signal with the other sideband; (c) adding the two sidebands; (d) envelope demodulating the generated simultaneous transmitted signal; (e) generating an error signal by subtracting the envelope demodulated simulcast signal from the delayed analog transmission signal according to a processing time for generating and demodulating the simulcast signal; (f) weighting the error signal according to a time varying or time invariant variable (k _n ; 0 ≦ _n ≦ N); (g) adding the weighted error signal to the delayed analog transmission signal to generate a new analog transmission signal; And (h) generating by an iterative process according to the step of delaying the digital transmission signal corresponding to the delay of the analog transmission signal, (A) to (h) are repeated N times according to another time-varying or time-invariant variable (k _n ; 0 ≦ _n ≦ N) and an analog transmission signal newly generated as the analog transmission signal, N is a positive integer comprising 0 and is determined according to a desired accuracy of the correction signal (C) which is determined according to the newly generated analog transmission signal after the Nth iteration. The method according to claim 5 or 6, The digital transmission signal is a DRM signal. The method according to claim 5 or 6, The analog transmission signal is a conventional AM signal. In the AM simultaneous broadcast signal generator for transmitting a digital transmission signal and an analog transmission signal in one transmission channel, A first modulator (1) for modulating the digital transmission signal into one sideband of a carrier of the transmission channel; And A second modulator (2) for modulating a correction signal (C) onto another sideband of said carrier of said transmission channel, And said correction signal (C) is determined so that envelope demodulation of said transmission channel represents said analog transmission signal. The method of claim 9, And a first adder (3) for adding the two sidebands. The method of claim 10, A third modulator (5) for modulating the digital transmission signal into the one side wave; A fourth modulator (6) for modulating the analog transmission signal into the other sideband; A second adder (7) for adding the two sidebands; A first envelope demodulator (9) for envelope demodulating the generated simultaneous transmitted signal; A first delay element (10) for delaying the analog transmission signal in accordance with processing time for generating and demodulating the respective simultaneous transmitted signal; A first subtractor (11) for generating an error signal by subtracting the envelope demodulated simultaneous transmission signal from the delayed analog transmission signal; A first multiplier (12) for weighting the error signal according to a time varying or time invariant variable (k ₀ ); A third adder (13) for adding the weighted error signal to the delayed analog transmission signal to produce the correction signal (C) or an intermediate correction signal; And AM broadcast signal further comprising a correction signal generator comprising a second delay element 14 for delaying said digital transmission signal in accordance with processing time for generating and demodulating said simultaneous broadcast signal. Generator. The method of claim 11, The correction signal generator, A fifth modulator (15 ₁ ,..., 15 _N ) for modulating the intermediate correction signal into the other sideband; A fourth adder (16 ₁ ,..., 16 _N ) for adding the two sidebands; A second envelope demodulator (17 ₁ ,..., 17 _N ) for envelope demodulating the generated simultaneous transmitted signal; A third delay element (18 ₁ ,..., 18 _N ) for delaying said intermediate correction signal in accordance with processing time for generating and demodulating said respective simultaneous transmitted signal; A second subtractor (19 ₁ ,..., 19 _N ) for generating an error signal by subtracting the envelope demodulated simultaneous transmission signal from the delayed intermediate correction signal; The error signal is time-varying or time-invariant (k _n ; Second multipliers 20 ₁ ,..., 20 _N for weighting according to ₁ ≦ n ≦ _N ; And N correction signals each comprising a fifth adder 21 ₁ ,..., 21 _N for adding the weighted error signal to the delayed intermediate correction signal to generate the correction signal C or the intermediate correction signal. Further includes a unit, N is a positive integer including 0, and is determined according to a desired accuracy of the correction signal (C) determined after the Nth correction signal unit. The method of claim 12, The N correction signal units, A sixth modulator (22 ₁ ,..., 22 _N ) for modulating the delayed digital transmission signal into the one side wave; And AM simultaneously characterized in that it further comprises a fourth delay element (23 ₁ , ..., 23 _N ) for delaying said digital transmission signal in accordance with a processing time for generating and demodulating said simultaneous transmission signal. Broadcast broadcast signal generator. The method of claim 12, The N correction signal units, And an AM simultaneous broadcast signal further comprising a fourth delay element for delaying said digital transmission signal modulated with said one sideband according to processing time for generating and demodulating said respective simultaneous transmitted signal. Generator. The method according to any one of claims 9 to 14, And the digital transmission signal is a DRM signal. The method according to any one of claims 9 to 14, And the analog transmission signal is a normal AM signal. A computer readable recording medium storing a computer program product, wherein the computer program product is computer program means for performing the method steps as defined in claim 5 or 6 when executed in a computer, digital signal processor or the like.

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