JPH0918443A - Multi-carrier modulation type receiver - Google Patents

Abstract

PURPOSE: To miniaturize a multi-carrier modulation type receiver of BST system. CONSTITUTION: A receiver 1 supplies a multiple signal divided into (m) blocks to a demodulation means 13 after receiving it with a single band area including (m) blocks and applying orthogonal transformation. The demodulation means 13 samples a received wave, and demodulates (n) pieces of demodulated data. Noise data demodulated from an area other than the (m) blocks in addition to L pieces of data demodulated from the multiple signal is included in the (n) pieces of demodulated data. A data conversion means 15 selects the L pieces of demodulated data demodulated from the multiple signal, and reproduces a broadcasting signal from the L pieces of demodulated data. A reproduced broadcasting signal is decoded b a decoder means 17, and given a sounding processing by a data processing means 23, and demodulated as the sound from a loudspeaker 25. A control means 19 omits a part of calculation performed by the demodulation means 13 based on the data representing the position of the (m) blocks stored in memory 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-carrier modulation type receiver for receiving and demodulating a multiple signal transmitted by modulating a large number of carriers by a digital signal.

[0002]

2. Description of the Related Art In audio broadcasting, video broadcasting, etc., digital broadcasting using a multi-carrier modulation system has been attracting attention in recent years. The multi-carrier modulation system may be referred to as a frequency division multiplex modulation system.

A digital broadcast using the multi-carrier modulation system is a broadcast in which data to be transmitted is divided and assigned to a large number of carriers, and each carrier is modulated by the assigned data and multiplexed and transmitted. Therefore, the symbol signal which is data assigned to each carrier and which modulates the carrier becomes slower than the symbol signal of the original data before division, and the interval between adjacent symbol signals becomes long. As a result, the broadcast wave modulated by the multicarrier modulation method is less likely to be affected by the delay time due to the reflected wave. In addition, the interval between adjacent carriers of a large number of carriers is set to, for example, 1 KHz. That is, the bandwidth per carrier wave is narrower than that of conventional broadcasting. Within this band, it can be considered that fading such as temporal variation of received power is almost flat.

For these reasons, it is unlikely to be affected by multipath interference of the multicarrier modulation system. In this modulation method, as the number of carriers is increased, the interference interference due to multipath can be suppressed. Furthermore, in this digital broadcasting, it is considered that the frequency interleaving and the time interleaving are combined with the multicarrier modulation system to further improve the performance of the transmission system using the multicarrier modulation system.

Regarding the audio broadcasting among the digital broadcasting using the multi-carrier modulation system, a worldwide unified recommendation is being prepared in the wireless communication sector which is a subordinate organization of the International Telecommunication Union, and an international standard is being prepared. In Europe, mobile digital audio broadcasting such as the EUREKA-147 project is being put to practical use. In Japan as well, practical application of digital broadcasting using the FM broadcasting band of 76 to 90 MHz is considered.

[0006] One of the digital broadcastings which is considered to be put into practical use is a BST (Band Split Transition) type digital broadcasting. In BST digital broadcasting, a plurality of narrow bandwidth frequency bands called blocks are used to perform multicarrier modulation digital broadcasting. The block can set its frequency band to an arbitrary narrower bandwidth than the bandwidth required by the multicarrier modulation method. Therefore, the digital broadcasting can be easily carried out in the frequency band in which the occupied frequency band of the existing broadcasting exists, such as the FM broadcasting band.

Further, since the carrier wave is selected from a plurality of dispersed blocks, it is less susceptible to multipath interference as in the multicarrier modulation method in which a signal is transmitted using a single wide band frequency band. Therefore, the receiver mounted on the moving body can satisfactorily receive the broadcast.

Each block can be set, for example, in the occupied frequency band of the existing broadcast wave. Therefore, the frequency utilization efficiency of the frequency band can be improved.
Further, since the position where the block is arranged can be arbitrarily determined, it is easy to deal with the change in the frequency business.

[0009]

As described above, in the BST system digital broadcasting, a plurality of blocks having a bandwidth that can be accommodated in an area where existing broadcast waves do not exist are set, and a plurality of blocks are collectively used. Conduct one digital broadcast.

In a receiver for receiving a digital broadcast of a multi-carrier modulation system, a signal is demodulated by using a mathematical means such as Fast Fourier Transform (hereinafter referred to as "FFT"). FF
The signal demodulated using T is preferably included in a single frequency band with a predetermined interval. Therefore, a receiver that receives this digital broadcast needs to demodulate the received signal individually for each block. Therefore, the receiver requires as many receiving means and demodulating means as the number of blocks used. This increases the size and complexity of the receiver.

Further, when a plurality of receiving means are provided in the receiver, noise is added to the receiving means and demodulating means of another system due to the high frequency output from the local oscillator of the receiving means.

It is an object of the present invention to provide a multi-carrier modulation type receiver capable of receiving and demodulating BST type digital broadcasting and reducing the number of receiving means and demodulating means.

[0013]

SUMMARY OF THE INVENTION The present invention receives a multiplexed signal in which L carrier waves are modulated and multiplexed based on a data string consisting of L (L is an integer) data having a predetermined data length. In a multi-carrier modulation type receiver that
The L carriers are selected from m (<L; m is an integer) discrete occupied frequency bands, receiving means for receiving radio waves in a predetermined frequency band including m occupied frequency bands, and the received radio waves. Based on demodulation means for demodulating n (n ≧ L; n is an integer) data, a memory in which data indicating positions of the m occupied frequency bands is stored, and data indicating positions stored in the memory And a data reproducing means for reproducing L data demodulated from the radio waves in the occupied frequency band of m from the n data and reproducing a data string composed of the L data. It is a carrier modulation type receiver. In the present invention, the demodulation means demodulates only radio waves included in an input frequency band having a narrower bandwidth than the predetermined frequency band, and uses demodulated radio waves included in m occupied frequency bands. It is further characterized by further including frequency conversion means for converting the frequency of the radio wave included in the band other than the input frequency band so as to be included in the band other than the other occupied frequency band within the input frequency band. Further, the present invention is characterized in that the demodulation means performs only an operation for demodulating radio waves included in the m occupied frequency bands of the predetermined frequency band. Further, in the present invention, the data string includes data obtained by dividing one or a plurality of broadcast signals by a predetermined data length, and the demodulation means selects one of the one or a plurality of broadcast signals.
It is characterized in that only calculation for demodulating a carrier wave modulated by data obtained by dividing one broadcast signal is performed.
The present invention further includes broadcast signal selection means for selecting any one of the plurality of broadcast signals, and the demodulation means demodulates all broadcast signals when the broadcast signal selection means is operated. It is characterized by doing.

[0014]

According to the present invention, a multi-carrier modulation type receiver receives a multiplexed signal in which L carrier waves are modulated and multiplexed based on a data string consisting of L data having a predetermined data length. . The carrier is selected from m discrete occupied frequency bands.

The m occupied frequency bands are set by dividing a single frequency band used in the multi-carrier modulation system into m. The bandwidth of each band is narrower than the single frequency band. The sum of the bandwidths of the m occupied frequency bands is about the same as that of the single frequency band. Therefore, this multiplex signal is less likely to be interfered with by multipaths, like a multiplex signal modulated by a single multicarrier modulation method. Therefore, by using the multiplex signal, the signal can be favorably received even in mobile communication or the like which is likely to be interfered by multipath interference. Further, each occupied frequency band can be set, for example, in a blank area in which the occupied frequency band of an existing broadcast wave in the FM broadcast band is not set.

The receiving means of the receiver receives all radio waves in a predetermined frequency band. The predetermined frequency band is a single frequency band including m occupied frequency bands. The radio wave received by the receiving means is given to the demodulating means.
In the demodulation means, first, n
Sampling radio waves in a book. This sampling is m
The modulated L carriers of the multiplexed signal included in the occupied frequency bands are sampled without exception. Then, the sampled n radio waves are collectively demodulated to obtain n data.

The demodulated n data are demodulated from the L data obtained by modulating the carrier sampled from the m occupied frequency bands and the radio waves sampled from the bands other than the m occupied frequency bands. The data that is the (n−L) noises included is included. In the present invention, a predetermined single frequency band including the divided m occupied frequency bands is regarded as a band including a radio wave to be demodulated, and it is assumed that there is a radio wave even in a band where no radio wave originally exists, and demodulation is performed. I do.

As described above, when a single frequency band including the discrete m occupied frequency bands is set and all the radio waves existing at a predetermined interval within this band are demodulated, FFT etc. It is possible to collectively demodulate a large number of radio waves by this method. Therefore, it is possible to demodulate the multiplexed signal transmitted in the discrete m occupied frequency bands by using one system of demodulation means for demodulating using FFT or the like.

The demodulated n pieces of data are given to the data reproducing means. In order to reproduce the transmitted data sequence, only L data demodulated from m occupied frequency bands out of the n demodulated data are required.
The receiver stores data indicating the positions of m discrete frequency bands in a memory. The data reproducing means selects L data from n data based on the data indicating the positions of the m occupied frequency bands stored in the memory. From the selected L data,
The transmitted data string is reproduced. As described above, in the multi-carrier modulation receiver of the present invention, the multiplexed signal divided into m blocks and transmitted is collectively demodulated together with the radio waves in a single frequency band including m blocks. ,
Select the required data and play it back.

As a result, it is possible to receive and demodulate the multiplexed signal divided into m occupied frequency bands by using one system of receiving means and demodulating means. Therefore, by using a plurality of receiving means, it is possible to prevent the receiving means from interfering with each other and generating noise. Moreover, the number of components of the receiver can be reduced.

Further, according to the invention, the demodulating means collectively demodulates only the radio waves included in the input frequency band. The input frequency band is set by the number and intervals of radio waves that can be collectively processed by the demodulation means.

It is conceivable that the receiver receives a multiplexed signal transmitted using m occupied frequency bands distributed over a wide band which is equal to or larger than the bandwidth of the input frequency band. In this case, the receiver performs frequency conversion on each radio wave. That is, of the received radio waves, the radio waves included in the m occupied frequency bands and included in the bands other than the input frequency band are included in the input frequency band and other occupied frequency bands by the frequency conversion means. Convert the frequency so that it is included in a band other than.

In order to reduce the influence of interference interference due to multipath, it is preferable to set the m occupied frequency bands in a frequency band having a wide bandwidth as much as possible. At this time, the frequency bandwidth of the entire m occupied frequency bands used for the transmission of the multiplexed signal is not changed, and the interval between blocks is widened. Further, the bandwidth of the occupied frequency band may be narrowed to increase the number of bands. The demodulation means demodulates the radio wave over the wide input frequency band, but if the m bands are distributed over the input frequency band that can be processed at one time by the demodulation means, a single demodulation is performed. It becomes difficult for the means to demodulate the radio waves at once. In this case, the receiver needs to include a plurality of systems of receiving means and demodulating means.

In such a case, the radio waves in the m occupied frequency bands are frequency-converted and moved so as to be included in the input frequency band. As a result, even if the occupied frequency band is dispersed over the bandwidth of the input frequency band, it is possible to demodulate the multiplexed signal using one system of receiving means and demodulating means.

The data obtained by demodulating the radio waves included in the distributed occupied frequency band is not used for reproducing the transmitted data string. When the occupied frequency bands are distributed over a wider band than the sum of the m occupied frequency bands, the band between the occupied frequency bands is wide, and the processing amount in the demodulation means may increase. In such a case, if frequency conversion is performed and the occupied frequency bands are gathered in a narrower band than the dispersed state, the bandwidth of the band between the occupied frequency bands can be made narrower than in the dispersed state. Therefore, the number of radio waves sampled from the band between the bands can be reduced. Therefore, the processing amount of the demodulation means can be reduced.

Further, according to the present invention, the demodulation means performs only an operation for demodulating radio waves included in the m occupied frequency bands of the predetermined frequency band. For example, in the case of collectively demodulating a large number of radio waves using a mathematical means such as FFT, a calculation for demodulation is performed while associating a large number of values sampled from the predetermined frequency band with each other. At this time, a part of the calculation includes a calculation necessary only for obtaining a certain demodulation result.

As described above, the demodulated n pieces of data include (n−L) pieces of data which are not required for reproducing the data string. In the demodulation means, of the operations for demodulation, only the operations related to the demodulation of L pieces of data are performed.
The operation required only for demodulating (n−L) pieces of data is omitted. As a result, the processing amount of the demodulation means can be reduced. Further, the arithmetic operation is performed while the arithmetic circuit in the demodulating means and the memory successively exchange data. By omitting part of the calculation, the number of times the calculation circuit accesses the memory can be reduced. Therefore, the processing time can be shortened.

According to the invention, the data string includes:
It includes data obtained by dividing one or more broadcast signals by a predetermined data length. The broadcast signal is information used as one unit, such as audio data of a broadcast program of audio broadcasting. When one such multiplex signal is received, a plurality of broadcast signals included in the multiplex signal are simultaneously reproduced.

The user of the receiver selects and uses any one broadcast signal from one or a plurality of broadcast signals. That is, when one broadcast signal is selected, the other broadcast signals are not used. Furthermore,
The multiplex signal includes a null carrier that is not used for transmitting the broadcast signal. The data obtained by dividing the broadcast signal other than the selected broadcast signal and the data demodulated from the null carrier are not used when reproducing the selected broadcast signal. The demodulating means of the receiver of the present invention performs only the operation for demodulating the carrier wave modulated by the data obtained by dividing one selected broadcast signal among one or a plurality of broadcast signals, and other broadcast signals and The calculation for demodulating the null carrier is omitted. As a result, the processing amount of the demodulation means can be reduced and the processing time can be shortened.

Further, according to the invention, the receiver is provided with a broadcast signal selecting means for selecting any one broadcast signal from a plurality of broadcast signals transmitted by the multiplex signal. The user of the receiver 1 demodulates the broadcast signal to be used from the plurality of broadcast signals by using the broadcast signal selection means. The broadcast signal selection means may be automatically operated by, for example, a microcomputer.

When selecting a broadcast program to be used by the user or when presetting a broadcast program that can be selected in the receiver, the broadcast signal receiving means is operated. In such a case, there is a demand to reproduce all broadcast signals once in order to grasp all available broadcast signals. For this reason, when the broadcast signal selection means is operated, the demodulation means performs all calculations for demodulating a plurality of broadcast signals included in the received multiplex signal. As a result, when the broadcast signals to be sequentially output are switched, the broadcast signals to be switched have already been reproduced, so that the switching can be performed quickly.

[0032]

1 is a block diagram showing the electrical configuration of a multicarrier modulation type receiver 1 according to a first embodiment of the present invention.

The multi-carrier modulation method is based on a data string composed of L pieces of data having a predetermined data length,
This is a modulation method in which L carriers are respectively modulated and the modulated carriers are multiplexed to create a modulated wave. In the present embodiment, an orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing;
Hereinafter, the "OFDM system" will be used. OFD
The M method is a multi-carrier modulation method that maximizes frequency utilization efficiency. Carrier waves used in the OFDM method are orthogonal to each other at a predetermined time Ts. The term orthogonal to the time Ts means that the value becomes 0 when any two carriers of the L carriers are multiplied and integrated over a predetermined time Ts.

If all the carriers are arranged so as to be orthogonal to each other, the modulation system of each carrier may be either an analog modulation system or a digital modulation system. In this embodiment, quadrature phase modulation
Shift Keying; hereinafter referred to as "QPSK") modulation method is used. Moreover, in the practical digital audio broadcasting, quadrature amplitude modulation (Quadrature Amplitude M
odulation; hereinafter referred to as "QAM").

In the QPSK modulation method, two carriers having the same frequency and a phase difference of 90 degrees, that is, two carriers orthogonal to each other are used, and the phase of the carrier is changed by a baseband signal which is data for modulating each carrier. 1
This is a modulation method in which modulation is performed by switching 80 degrees, and each modulated carrier wave is multiplexed to generate a modulated wave to be transmitted. The QAM modulation method uses two carriers that are orthogonal to each other, simultaneously performs amplitude modulation in which the amplitude is changed by a baseband signal and phase modulation in which the phase is changed, and multiplexes the modulated carriers for transmission. This is a modulation method that generates a power-modulated wave.

The signal structure of the multiplexed signal received by the receiver 1 will be described below. The occupied frequency band of the multiplexed signal transmitted from the transmitter is divided into m. m is an integer equal to or less than L. The bandwidth of the divided block, which is the occupied frequency band, is narrower than the single frequency band used in the OFDM modulation method. The m blocks are selected so as to have the same bandwidth as a single frequency band used in the OFDM modulation scheme when the bandwidths of the blocks are added. Also, each block is set so as not to overlap with the occupied frequency band of the existing broadcast.

L carriers, for example, 1536 carriers are used. The interval between the center frequency of each carrier and the center frequency of the adjacent carrier is set to 1 KHz. A baseband signal composed of a large number of modulation data that modulates one carrier wave has 76 symbols as one frame. One symbol includes an effective symbol used for transmitting data and a guard interval.

The guard interval is provided in order to prevent the orthogonality between symbols from being disturbed due to the delayed reflected wave interfering with the transmitted wave due to multipath interference or the like. The receiver demodulates only the data contained in the effective symbols of the transmitted symbols when demodulating to the transmitted multiple signals. Thus, by providing the guard interval in the signal, for example, in addition to the direct wave directly transmitted from the multicarrier modulation type transmitter 1, a route different from the direct wave and a route through which the direct wave is transmitted are provided. When the carrier wave is input to the antenna via a long path and the delay time of the carrier wave is equal to or less than the length of the guard interval, the influence of multipath interference can be eliminated. Therefore, the influence of multipath interference can be reduced.

The L modulation data for modulating the carrier wave is created from, for example, data obtained by dividing a broadcast signal of a broadcast program by a predetermined data length. The broadcast program may be audio broadcast, text broadcast, or the like. The broadcast signal may be an analog signal or a digital signal. Furthermore, you may make it transmit the broadcast signal which is the data of several broadcast programs simultaneously. When collectively transmitting a plurality of broadcast signals, a plurality of broadcast signals to be transmitted may be multiplexed in advance using a method such as a time division multiplexing method.

Further, the L modulated data are interleaved so that the transmission order of the data obtained by dividing the broadcast signal is arbitrarily exchanged, and the transmitted signal modulated by the modulated data on the time axis and the frequency axis is obtained. , May be assigned so as not to be regularly lined up with the original broadcast signal.

Furthermore, the L modulation data may include identification data. The identification data is arranged so as to be superimposed on the leading symbol of each frame, for example. The identification data includes data indicating the positions of m blocks, the presence / absence and system of interleaving, the broadcast signal multiplexing system, and the encoding format. The receiver 1 demodulates the multiplexed signal based on this identification data.

The multiplexed signal is formed by multiplexing the transmission signals generated by modulating the L carrier waves selected from the m blocks by the L modulated data described above. In addition, a null carrier is included in the multiplexed signal. A null carrier is a virtual modulated wave that does not include radio waves and does not include data obtained by dividing a broadcast signal. Therefore, when demodulating the multiplexed signal by the receiver 1 and reproducing the broadcast signal, demodulation without the null carrier does not affect the reproduction of the transmitted data. The carrier wave set as the null carrier is, for example, a carrier wave included in a frequency band matching the end of the pass band of the filter or a carrier wave whose frequency that is easily influenced by the direct current component of the carrier wave is near 0 Hz.

The configuration of the multicarrier modulation type receiver 1 will be described with reference to FIG.

The radio wave received by the antenna 4 is amplified by the amplifier circuit 5, filtered by the band pass filter, and then given to the multipliers 7 and 8, respectively.

The spectrum of the radio wave received by the antenna 4 is shown in FIG. The occupied frequency band for transmitting the multiplexed signal in the received radio waves is divided into m blocks, for example, four blocks W1 to W4. The multiplexed signal is divided into blocks W1 to W4 and transmitted, showing rectangular spectra F1 to F4, respectively. Between the blocks W1 and W2 and between the blocks W3 and W4, occupied frequency bands W5 and W6 of another broadcast are set, and the spectrum F of the broadcast wave is set.
5 and F6 are present.

The pass band of the band pass filter is represented by 2 in FIG.
It is shown by a dotted chain line 6. The pass band of the filter is from the lowest frequency f1 of the block W1 to the highest frequency f of the block W4.
The bandwidth is set so that all radio waves in the frequency bands up to 2 can be filtered. The bandwidth of the pass band of the band pass filter is (f2-f1), and its center frequency fo is
It is defined by ((f2-f1) / 2). This bandwidth is wider than the sum of the bandwidths of the blocks W1 to W4. The radio wave filtered by the band pass filter is
The broadcast wave of another broadcast is included in addition to the multiplex signal.

The multiplexed signal contained in the radio wave output from the band pass filter is a signal obtained by multiplexing the transmission signals obtained by modulating L carrier waves. QPS for modulation of each carrier
When the K modulation method or the QAM modulation method is used, each transmission signal is a signal obtained by modulating two carrier waves having the same frequency but different phases by 90 degrees. That is, the multiplex signal of the digital broadcast has a configuration in which L modulated carriers having the same phase are multiplexed to form a first multiplex signal, and two types of first multiplex signals having different phases are further multiplexed. The multipliers 7 and 8 convert the high-frequency multiplexed signal into a low-frequency basic signal, and at the same time, change the phase difference of 2
An orthogonal transform for separating the first multiplex signals of the type is performed.

In the multiplier 7, the output from the band pass filter and the high frequency signal output from the local oscillator 9 are mixed and a low frequency radio wave including the first basic signal is output. In the multiplier 8, the output from the band pass filter and the output from the local oscillator 9 are mixed with the output whose phase is delayed or advanced by 90 degrees in the phase converter 10,
A low frequency radio wave including a second basic signal having a phase difference of 90 degrees from the first basic signal is output. The basic signal is a signal in which L carriers, each of which has a center frequency that is an integral multiple of the frequency of the lowest basic carrier, are modulated with corresponding L pieces of modulation data.

The low frequency radio wave including the first and second basic signals is applied to the demodulation means 13 after being filtered by, for example, a band pass filter. Antenna 4, amplifier circuit 5, multipliers 7 and 8, local oscillator 9, and phase converter 1
0 constitutes a receiving means for receiving the multiplexed signal and giving two kinds of basic signals to the demodulating means 13.

In the demodulation means 13, low frequency radio waves including the given first and second basic signals are respectively calculated using FFT to demodulate n modulation data. In the case of demodulating a large number of data at once using FFT,
The center frequency of each transmission signal included in the basic signal needs to be an integral multiple of the lowest center frequency. In BST digital broadcasting, a basic signal exists by being divided into m blocks. In this embodiment, assuming that a signal to be demodulated also exists between blocks, demodulation using FFT is performed over the entire frequency band from the lowest frequency f1 of the block W1 to the highest frequency f2 of the block W4.

The demodulation means 13 samples the low-frequency signals given by the multipliers 7 and 8. The sampling interval is set to 1 kHz, for example, and n signals to be demodulated including L transmission signals included in the multiplex signal are obtained. The n signals to be demodulated are collectively demodulated using the FFT to obtain n demodulated data. The n demodulated data are
It is given to the data converting means 15 which is a data reproducing means. In the data conversion means 15, from the n demodulated data,
Play the transmitted broadcast signal.

FIG. 3A is a diagram showing a demodulated data string of n pieces of demodulated data output from the demodulating means 13. L pieces of demodulated data are demodulated from the radio waves included in the blocks W1 to W4. The L pieces of demodulated data consist of blocks W1 to W1.
Corresponding to W4, the demodulated data groups s1 to s4 are divided and exist. Between the demodulated data groups s1 and s2, the demodulated data group s
Between s2 and s3 and between demodulation data groups s3 and s4, demodulation data groups s5 to s7 including demodulation data demodulated from signals included in bands other than blocks W1 to W4, respectively.
Is interposed.

The (n−L) pieces of demodulated data included in the demodulated data groups s5 to s7 are noise data obtained by sampling and demodulating radio waves of another broadcast, for example, and use multiple signals. The data is irrelevant to the broadcast signal transmitted. In the data conversion means 15, the block W1
Only the demodulated data demodulated from bands other than W4 are selected and other demodulated data are removed. FIG. 3B is a diagram showing a demodulated data string composed of L pieces of demodulated data obtained by removing noise data. In this demodulated data string,
Only demodulated data groups s1 to s4 are included.

The data conversion means 15 performs serial-parallel conversion on the selected L demodulated data. Furthermore, if the broadcast signal being converted is interleaved,
Cancel interleaving and return the data arrangement to the original state. As a result, the broadcast signal converted into a signal in which the carrier wave can be modulated by a predetermined modulation method is reproduced. For example, when a carrier is modulated by the QPSK modulation method, a signal capable of modulating one carrier is
It is a digital signal composed of two values, "1" and "-1". The digital signal is, for example, “1” is “1” among digital signals composed of binary values of “1” and “0”.
And “−1” corresponds to “0”. The reproduced converted broadcast signal is provided to the decoding means 17.
Further, the converted broadcast signal is also given to the control means 19.

The decoding means 17 converts the broadcast signal reproduced by the data converting means 15 into a digital signal consisting of binary values of "1" and "0" and reproduces the broadcast signal. Further, when the broadcast signal is an analog signal such as an audio broadcast, the digital signal is converted into an analog signal by using a digital / analog conversion circuit. The reproduced broadcast signal is given to the data processing means 23.
Further, when a plurality of broadcast signals are simultaneously transmitted, only one broadcast signal selected by the user is given to the data processing means 23.

The control means 19 reproduces the identification data from the converted broadcast signal. The control means 19 controls the processing in the data conversion means 15 and the decoding means 17 for the signals transmitted after the identification data, based on the reproduced identification data. For example, the data conversion means 15 obtains data regarding the presence or absence of interleaving and the method from the identification data, and deinterleaves based on this data. Further, the demodulated data included in each block is selected from the n demodulated data based on the data indicating the positions of the m blocks, and irrelevant demodulated data is removed. The decoding means 17 decodes the broadcast signal based on the data indicating the encoding format.

The control means 19 is provided with a memory 20 for storing identification data. The user may directly input the data obtained from the identification data, such as the positions of the m blocks and the modulation scheme of the multiplex signal, to the receiver 1. Alternatively, it may be stored in the memory 20 by another means.

Further, the output from the broadcast signal selection means 21 is given to the control means 19. The broadcast signal selection means 21 is provided with operation means such as an input key. The user operates the operation means to select the broadcast signal to be used from the plurality of transmitted broadcast signals. The broadcast signal selection means 21 gives an output indicating the broadcast signal selected by the user to the control means. The control means 19 is the broadcast signal selection means 2
According to the output of 1, the operation of selecting the broadcast signal by the decoding means 17 is controlled.

The data processing means 23 converts the broadcast signal into a form that can be presented to the user of the receiver and outputs it. For example, if the broadcast signal is audio broadcast data, it is converted into sound and output from the speaker 25 as sound. If the transmission data is teletext data, the text output means 26 visually displays the text.

In this way, in the multi-carrier modulation type receiver 1 of the present embodiment, the broadcast signal divided into m blocks and transmitted is bundled together with the radio waves in a single frequency band including m blocks. Then, after demodulating, necessary data is selected and reproduced. With this, it is possible to receive and demodulate the multiplexed signal divided into m blocks using one-system receiving means and demodulating means. Therefore, when a plurality of receiving means are used, it is possible to prevent the receiving means from interfering with each other and generating noise. further,
The number of parts of the receiver can be reduced.

In the BST system digital broadcasting, it is preferable that m blocks are set as dispersed as wide as possible. For this purpose, for example, as shown in FIG. 4, blocks W11 to W13 of the first digital broadcast,
The blocks W14 and W15 of the second digital broadcast are mixed, and the spectrum F11 of the multiplexed signal of the first digital broadcast is obtained.
It is possible that? F13 and the spectra F14 and F15 of the multiplex signal of the second digital broadcast coexist.

In the multi-carrier modulation type receiver 1 of this embodiment, of the n demodulated data demodulated by the demodulation means 13, only L demodulated data demodulated from radio waves contained in m blocks. Are required to reproduce the broadcast signal. That is, in the demodulation means, from the lowest frequency f11 of the block W11 to the highest frequency f12 of the block W13.
Up to the maximum frequency f13 of the block W11, although all the radio waves included in the frequency band up to
The demodulated data demodulated from radio waves in the frequency band up to the lowest frequency f14 of 12 are not used for reproducing the broadcast signal.

In the demodulation means 13 of this embodiment, the block W
Block W, which executes only the operation for demodulating the multiplexed signals of 11 to W13 and is defined by frequencies f13 and f14
The calculation for demodulating radio waves in the frequency band including 14 is omitted. Similarly, when another broadcast interposed between the m blocks is an analog signal or when another broadcast does not exist between the m blocks, the same calculation is omitted.

In digital broadcasting, a plurality of broadcast signals can be simultaneously transmitted by using a single multiplexed signal transmitted using m blocks. The user of the receiver 1 can simultaneously obtain a plurality of broadcast signals from the multiplexed signal of the digital broadcast. When the broadcast signal is an audio broadcast signal, the user selects and listens to any one of the plurality of broadcast signals. Therefore, when one broadcast signal is selected, the other broadcast signals are not used. Furthermore, the multiplexed signal includes a null carrier that is not used for transmitting the broadcast signal. In the demodulation means 13 of this embodiment, only the operation for demodulating the transmission signal which is included in the multiplex signal and which is modulated by the data obtained by dividing one selected broadcast signal is executed, and the other transmission signals are demodulated. The calculation for doing this is omitted.

When the demodulating means 13 is a means for demodulating a radio wave using an FFT, in order to omit the operation for demodulating the signal as described above, the operation at some points of the butterfly operation of the FFT. To stop. FIG. 5 is a flow chart for explaining the butterfly operation of FFT.

FIG. 5 is a flow chart of the FFT when the number of carriers is four. White circles indicate calculation points at which calculations are performed, and arrows indicate destinations to which the values calculated at the calculation points are given. Values such as the levels of radio waves obtained by sampling are given to the calculation points x1 to x4. Calculation point y1
The demodulated data demodulated by the FFT is output from y4. The calculation points z1 to z4 are points at which calculation is performed based on the values output from the calculation points x1 to x4.

For example, the value output from the calculation point y1 is calculated based on the values given from the calculation points z1 and z2. The value output from the calculation point z1 is the calculation point x1,
It is calculated based on the value given by x3. Calculation point z
The value output from 2 is calculated based on the values given from the calculation points x2 and x4. That is, the value output from the calculation point y1 is calculated based on the values of all the calculation points x1 to x4. Similarly, the values output from the calculation points y2 to y4 are calculated based on the values of the calculation points x1 to x4.

Of these calculations, calculation points z1 and z2
The value calculated by is given only to the calculation points y1 and y2. Similarly, the values calculated at the calculation points z3 and z4 are given only to the calculation points y3 and y4. Therefore, the calculation point y
When the calculation results output from 3 and y4 are demodulation data other than the data of the selected broadcast signal and the demodulation data is irrelevant in the reproduction of the broadcast signal, Even if the calculation is stopped, the calculation at other calculation points is not affected. Therefore, the two-dot chain line 3
The calculation at the calculation point within 0 may be stopped. In this way, by omitting a part of the butterfly operation of FFT, the processing time in the demodulation means 13 can be shortened.

The demodulation of the multiple signals uses a DSP (Digital Signal) by using mathematical means such as fast Fourier transform.
Prosessor) and other circuits. DS
P can be used in various processes other than the fast Fourier transform. Therefore, by shortening the time required for demodulation, it is possible to cause the DSP to execute another process in the extra time. This allows the DSP to be used efficiently.

Furthermore, when a plurality of broadcast signals are demodulated by using the receiver 1 of this embodiment, a broadcast program to be listened to is selected, or a broadcast program that can be selected by the receiver is set. May be preset. At this time, there is a desire to listen to all broadcast programs. For this reason, when the broadcast signal selection means 21 is operated, all calculations for demodulating the broadcast signal may be performed. Also at this time, the calculation for demodulating the data included in the band other than the m blocks may be omitted.

FIG. 6 is a block diagram showing the electrical construction of a multi-carrier modulation type receiver 31 according to the second embodiment of the present invention. The receiver 31 has a configuration similar to that of the multicarrier modulation type receiver 1 of FIG. 1, the same components are designated by the same reference numerals, and description thereof will be omitted.

The multiplexed signal is distributed and transmitted in m blocks. As described above, the m blocks are dispersed and set in a wide frequency band. Demodulation means 1
3 demodulates a radio wave over a wide bandwidth including m blocks, but when m blocks are dispersed over a frequency band that can be processed at one time by the demodulating means 13, the receiving means and the demodulating means are provided. It is necessary to prepare two systems of means.

In order to reduce the influence of interference caused by multipath, it is preferable to disperse m blocks in a frequency band having a wide bandwidth. At this time, the frequency bandwidth of the m blocks themselves used for transmission of the multiplexed signal is not changed, and the interval between the blocks is widened.

In this embodiment, the multiplexed signal dispersed in a wide band and transmitted is frequency-converted so that it falls within the input frequency band of the demodulation means 13. The input frequency band refers to a frequency band that can be processed at one time by the demodulation means 13.

In the receiver 31 of FIG. 6, the radio wave received by the antenna 4 is amplified by the amplifier circuit 5, filtered by the bandpass filter, and then given to the multipliers 32 and 33. In the multipliers 32 and 33, the output of the band pass filter and the high frequency signals of different frequencies output from the local oscillators 35 and 36 are mixed and frequency converted.
The outputs from the multipliers 32 and 33 are added by the adder 38, amplified by the amplifier circuit 39, and then given to the multipliers 7 and 8 to be orthogonally transformed.

For example, as shown in FIG. 7, block W
When the spectrums F21 to F24 of the multiplexed signal transmitted using 21 to W24 are dispersed in a wider band than the input frequency band W25, the signals included in the blocks W23 and W24 arranged outside the band W25 are detected. The frequency is converted so that it is included in the band W25. At this time, the blocks W23a and W2 after frequency conversion
The positions of the spectra F23a and F24a of 4a are in the band W
It is set within 25 and at a position where it does not overlap with other spectra F21 and F22.

To perform such frequency conversion, first,
Blocks W23, W24 from the local oscillator before frequency conversion
Of the reference frequency f21 and the block W23 after frequency conversion
The frequency (f21-f22) of the difference value from the reference frequency f22 of a and W24a is output, and the frequency is converted in the multiplier by mixing with the output from the band pass filter. The frequency-converted radio wave and the non-frequency-converted radio wave are added by an adder, and only the radio waves included in the band W25 are filtered by a bandpass filter. A signal including is output.

As a result, it is possible to demodulate a multiplexed signal dispersed in a frequency band having a wider bandwidth than the input frequency band by using one system of receiving means and demodulating means.
Further, although the receiver 31 of FIG. 6 performs the orthogonal transformation after frequency conversion and addition of the radio waves, the orthogonal transformation may be performed simultaneously with the frequency conversion. By simultaneously performing the frequency conversion and the orthogonal transformation, it is possible to eliminate the local oscillator used for the orthogonal transformation, and thus it is possible to further reduce the number of components.

[0079]

As described above, according to the present invention, a multi-carrier modulation system receiver receives a multiple signal generated by the multi-carrier modulation system. The frequency band for transmitting the multiplex signal is divided into m parts, and is distributed in a wider band than the frequency band before being divided. Data indicating the positions of the dispersed m frequency bands are stored in the memory of the receiver.

The receiver regards a predetermined frequency band including the divided m occupied frequency bands as a band including a radio wave to be demodulated, receives all the radio waves in the band, and then demodulates necessary data. To reproduce the transmitted data sequence. This makes it possible to demodulate a multiplexed signal that is divided into m discrete occupied frequency bands and transmitted, using one-system receiving means using FFT or the like and demodulating means. Therefore, it is possible to prevent a plurality of receiving means for receiving the divided multiplexed signal from interfering with each other and generating noise. Further, since the number of parts of the receiver can be reduced, the receiver can be downsized. Therefore, the manufacturing cost of the receiver can be reduced.

Further, according to the present invention, the receiver frequency-converts the received multiplex signal so that the dispersed band falls within a predetermined bandwidth. This makes it possible to demodulate a multiplexed signal that is distributed and transmitted in a wider band than the bandwidth that the demodulating means can process at one time, using only the demodulating means. At the same time, the band containing the radio waves other than the transmitted multiplex signal can be narrowed to reduce the number of radio waves to be demodulated by the demodulation means. Further, comparing the demodulation means and the frequency conversion means, the frequency conversion means has a simpler configuration and a lower manufacturing cost.
Therefore, as compared with the case of using a plurality of demodulation means, the structure of the receiver can be simplified and the manufacturing cost can be reduced.

Further, according to the present invention, the demodulation means performs only an operation for demodulating radio waves included in the m occupied frequency bands of the predetermined frequency band.

Further, according to the present invention, the demodulation means is for demodulating data for reproducing any one selected broadcast signal from a plurality of broadcast signals and a multiplexed signal including null carriers. Do only arithmetic. As described above, only the calculation for demodulating only the multiplex signal or the broadcast signal which the user of the receiver 1 selects and intends to use is performed, so that the processing amount and processing time of the demodulation means can be reduced. Therefore, for example, the arithmetic circuit of the demodulation means can be used for another arithmetic operation, so that the circuit can be efficiently used.

Furthermore, according to the present invention, the demodulation means demodulates all the data of a plurality of broadcast signals included in the multiplex signal when the broadcast signal selection means is operated. Thereby, for example, when the broadcast signal to be used is switched in a short time, the switching can be performed quickly. Therefore, the operability of switching the broadcast signal can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration of a multicarrier modulation type receiver 1 which is a first embodiment of the present invention.

FIG. 2 is a graph showing a spectrum of a radio wave received by an antenna 4.

FIG. 3 is a diagram showing a demodulated data string of n pieces of demodulated data output from a demodulation means 13 and a diagram showing a demodulated data string of L pieces of demodulated data obtained by removing noise data.

FIG. 4 is a block W11 to W1 of the first digital broadcast.
3 and blocks W14, W1 of the second digital broadcast
5 is a graph for explaining the arrangement of No. 5 of FIG.

FIG. 5 is a flowchart of butterfly operation of FFT.

FIG. 6 is a block diagram showing an electrical configuration of a multicarrier modulation receiver 31 according to a second embodiment of the present invention.

FIG. 7: Block W21 of digital broadcasting before frequency conversion
~ W24 and blocks W21, W22 after frequency conversion,
It is a graph which shows the relationship between W23a and W24a and input frequency band W25.

[Explanation of symbols]

 1, 31 Multi-carrier modulation receiver 4 Antenna 5 Amplification circuit 7, 8; 32, 33 Multiplier 9; 35, 36 Local oscillator 10 Phase converter 13 Demodulation means 15 Data conversion means 19 Control means 20 Memory 21 Broadcast signal selection means 38 adder

Claims (5)

[Claims] 1. L having a predetermined data length (L is an integer)
In a multi-carrier modulation type receiver which receives a multiplexed signal in which L carriers are modulated based on a data string composed of L data, L carriers are m (<L; m is an integer) Receiving means selected from discrete occupied frequency bands and receiving radio waves in a predetermined frequency band including m occupied frequency bands, and n (n ≧ L; n) from the received radio waves.
Based on the data indicating the positions stored in the memory, and the demodulation means for demodulating the data of m)
A multi-carrier modulation system, which includes L data demodulated from radio waves in m occupied frequency bands from the data, and data reproducing means for reproducing a data string composed of the L data. Receiving machine. 2. The demodulating means demodulates only radio waves included in an input frequency band having a narrower bandwidth than the predetermined frequency band, and receives the radio waves included in m occupied frequency bands. A frequency conversion means for converting the frequency of a radio wave included in a band other than the input frequency band so as to be included in a band other than another occupied frequency band within the input frequency band is further included. 1. The multi-carrier modulation type receiver according to 1. 3. The demodulation means performs only an operation for demodulating radio waves included in the m occupied frequency bands of the predetermined frequency band.
The described multi-carrier modulation receiver. 4. The data string includes data obtained by dividing one or a plurality of broadcast signals by a predetermined data length, and the demodulation means outputs one of the one or a plurality of broadcast signals. 2. The multi-carrier modulation type receiver according to claim 1, wherein only a calculation for demodulating a carrier wave modulated by the divided data is performed. 5. A broadcast signal selecting means for selecting any one of the plurality of broadcast signals, wherein the demodulating means demodulates all the broadcast signals when the broadcast signal selecting means is operated. The multicarrier modulation type receiver according to claim 4, wherein