JP2966837B1 - OFDM receiver - Google Patents

Abstract

An OFDM receiving apparatus reduces the number of FFTs and the like necessary for performing diversity reception or simultaneous reception in multiple frequency bands. SOLUTION: Signals received by antennas 1 and 5 are amplified by reception high frequency units 2 and 6, and then converted into intermediate frequency signals of mutually adjacent frequencies by mixers 3 and 7 and local oscillators 4 and 8, and combined. The signal is digitized by the A / D converter 11 as one signal by frequency division multiplexing by the unit 9, and then the signal on the time axis is converted into a signal on the frequency axis by the FFT 12. The converted signal is subjected to diversity combining by selection or addition by a combining circuit 13, demodulated by a carrier demodulation circuit 14, and then output as a digital signal through an error correction circuit 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving apparatus employing an OFDM (Orthogonal Frequency Division Multiplexing) system in digital broadcasting, for example, and more particularly to a technique for performing diversity reception and selective reception of a plurality of programs.

[0002]

2. Description of the Related Art When receiving broadcast or communication for a mobile unit using a single carrier system, a good reception quality is ensured because the reception environment of the mobile unit is inferior to a fixed reception environment. In order to achieve this, a diversity reception method is employed. As a diversity receiving system in the conventional single carrier system, it is general to combine antenna outputs, and as a combining system, a selection system and an addition system including maximum ratio combining are known. still,
In the case of the addition method, it is necessary to add the phases of the respective received signals.

On the other hand, since the OFDM system is one of the multi-carrier systems, it is difficult to add together the phases of each carrier in the case of the conventional diversity reception system of the addition system. On the other hand, since the OFDM system is a multi-carrier system, diversity reception can be performed for each carrier.

FIG. 8 is a block diagram showing a configuration example of a receiving apparatus for performing diversity reception for each carrier.

In FIG. 8, an OFDM high-frequency signal received by a reception antenna A1 is amplified by a reception high-frequency unit A2 and input to a mixer A3. A local oscillation signal is applied from a local oscillator A4 to the mixer A3, and an intermediate frequency signal is output from the mixer A3. A clock is reproduced from the intermediate frequency signal by the synchronization circuit A5 and is used as a reference in the receiving device. The intermediate frequency signal is A
A / D converter A6 converts an analog signal into a digital signal, and an FFT (Fast Fourier Transformer) A7 converts a signal on the time axis into a signal on the frequency axis. Separated into signals.

[0006] A circuit similar to the above is constituted by a reception antenna B1, a reception high-frequency section B2, a mixer B3, a local oscillator B4, a synchronization circuit B5, an A / D converter B6, and an FFTB7.

The outputs of FFTA7 and B7 are output from a synthesis circuit A8.
, And a larger signal is selected according to, for example, the amplitude. The output of the combining circuit A8 is demodulated for each carrier in the carrier demodulation circuit A9, and digital reception data is obtained. The received data is subjected to error correction processing by an error correction circuit A10, and digital output data is obtained.

[0008]

However, in the conventional OFDM receiving apparatus, when diversity reception is performed as described above, each of a plurality of antenna reception inputs is separated into signals of carrier waves constituting OFDM. Since synthesis is performed later, there is a problem that an FFT and a synchronous circuit that are expensive by the number of systems are required. It is also conceivable to prepare a plurality of receiving systems and receive signals of different contents in different frequency bands from each other so that the program can be switched in a short time.
Also in this case, there is a problem that an expensive FFT or a synchronous circuit is required for the number of systems.

An object of the present invention is to provide an OFDM type receiving apparatus which solves the above-mentioned problems, shares a plurality of receiving systems, simplifies the overall configuration and can reduce the cost. And

[0010]

In order to achieve the above object, a receiving apparatus according to the present invention performs frequency division multiplexing on a high frequency signal having the same content and the same content received by a plurality of antennas, thereby forming one high frequency signal. FFT processing is performed as a signal. Similarly, high-frequency signals having the same contents transmitted at different frequencies are similarly frequency-division multiplexed and subjected to FFT processing as one high-frequency signal.

That is, a signal of the same frequency and the same content received by a plurality of antennas is frequency-division multiplexed by frequency-converting the signal into a signal of a generally different frequency band adjacent thereto, and the FFT processing is performed as one high-frequency signal. Do. Alternatively, FFT processing is performed on signals of the same content received in different frequency bands as one high-frequency signal. After separating into signals of each carrier by FFT processing, diversity combining by selection or addition is performed. Thereby, the number of expensive FFTs can be reduced.

[0012] Alternatively, signals of different contents received in different frequency bands are converted into one high-frequency signal by F
Perform FT processing. In this case, the program can be switched in a short time.

Specifically, the configuration is as follows.

(1) receiving means for receiving, via a plurality of antennas, a high-frequency signal based on the OFDM (Orthogonal Frequency Division Multiplexing) method in which information of the same frequency and of the same content is transmitted;
Of the plurality of high-frequency signals obtained by this means, frequency conversion means for making frequency bands of at least one or more high-frequency signals substantially adjacent to each other by frequency conversion, and a plurality of signals adjacent to each other by this means. Combined into one OF
Combining means for converting the signal into a DM signal and OFD obtained by this means
One fast Fourier transformer that converts the M signal from the time axis to a signal on the frequency axis and separates the signal for each carrier;
Diversity combining means for diversity combining the signals of the respective carrier waves obtained by the fast Fourier transformer for each signal having the same information, and demodulating means for demodulating each frequency signal diversity-combined by this means. I do.

In this configuration, at least one high-frequency signal of the same frequency and the same content of an OFDM high-frequency signal received by a plurality of different antennas is frequency-converted into a composite signal by frequency division multiplexing. A single fast Fourier transformer converts the synthesized signal on the time axis into a signal on the frequency axis to separate information transmitted by carriers of each frequency in the OFDM system, and receives the information through the different antennas. It is characterized in that the separated output of the signal is diversity-combined and demodulated for each carrier of each frequency received at the same frequency.

(2) Receiving means for receiving, by a plurality of antennas, a high-frequency signal by the OFDM system in which information having the same frequency and the same content is transmitted, and at least one of the plurality of high-frequency signals obtained by this means Frequency converting means for converting the above high-frequency signals so that their frequencies are substantially adjacent to each other, combining means for combining a plurality of signals adjacent to each other into one OFDM signal, and combining means for obtaining one OFDM signal; One fast Fourier transformer for converting the obtained OFDM signal from a time axis to a signal on a frequency axis and separating it into signals for each carrier, and demodulation for demodulating the signal of each carrier obtained by the fast Fourier transformer Means,
Diversity combining means for diversity combining the demodulated signal for each carrier obtained by this means for each demodulated signal having the same information.

In this configuration, at least one high-frequency signal of the same content of the same frequency received by a plurality of different antennas and having the same content is converted into a composite signal by frequency division multiplexing. After converting the synthesized signal on the time axis into a signal on the frequency axis by one fast Fourier transformer, separating the information transmitted by the carrier of each frequency of the OFDM system, demodulating for each carrier, A demodulation output of signals received by a plurality of antennas is diversity-combined for each demodulation output obtained by a carrier of each frequency received at the same frequency.

(3) The same information is transmitted in some or all of the carrier waves in different frequency bands.
Receiving means for receiving a plurality of high-frequency signals of the FDM method;
Of the plurality of high-frequency signals obtained by this means, frequency conversion means for making frequency bands of at least one or more high-frequency signals substantially adjacent to each other by frequency conversion, and a plurality of signals adjacent to each other by this means. Combined into one OF
Combining means for converting the signal into a DM signal and OFD obtained by this means
One fast Fourier transformer that converts the M signal from the time axis to a signal on the frequency axis and separates the signal for each carrier;
Diversity combining means for diversity combining the signals of the respective carrier waves obtained by the fast Fourier transformer for each signal having the same information, and demodulating means for demodulating each frequency signal diversity-combined by this means. I do.

This configuration frequency-converts at least one high-frequency signal among the high-frequency signals of the OFDM system in which the same information is transmitted in some or all of the carriers received in different frequency bands, A signal of a frequency band is multiplexed by converting the signal into a signal on a frequency axis by using a single fast Fourier transformer.
Dividing information transmitted by carriers of each frequency of the DM system, and performing diversity synthesis and demodulation of separated outputs of signals received in the plurality of different frequency bands for each carrier on which the same information is transmitted. Features.

(4) Information of the same content is transmitted in some or all of the carriers in different frequency bands.
Receiving means for receiving a plurality of high-frequency signals of the FDM method;
Frequency converting means for converting frequency bands of at least one or more of the high-frequency signals obtained by this means to make frequency bands substantially adjacent to each other, and a plurality of signals which are mutually adjacent by this means; Into one O
Combining means for generating an FDM signal, and OF signal obtained by this means
One fast Fourier transformer for converting a DM signal from a time axis to a signal on a frequency axis and separating it into a signal for each carrier; and a demodulating means for demodulating a signal of each carrier obtained by the fast Fourier transformer. And diversity combining means for diversity combining the demodulated signal for each carrier obtained by this means for each demodulated signal having the same information.

This configuration frequency-converts at least one high-frequency signal among the high-frequency signals of the OFDM system in which the same information is transmitted in a part or all of the carriers received in different frequency bands, A signal of a frequency band is multiplexed by converting the signal into a signal on a frequency axis by using a single fast Fourier transformer.
After separating the information transmitted by the carrier of each frequency of the DM system and demodulating the information for each carrier, the demodulated output of the signal received in the plurality of different frequency bands is obtained by the carrier carrying the same information. Diversity synthesis is performed for each demodulated output.

(5) Different channels arranged near each other
Receiving means for receiving a plurality of high-frequency signals of the OFDM system in which the same information is transmitted in a part or all of the carrier of the frequency band of the channel;
One fast Fourier transformer that converts the DM signal as one OFDM signal from the time axis to a signal on the frequency axis and separates the signal for each carrier, and the signal of each carrier obtained by this fast Fourier transformer And diversity combining means for performing diversity combining for each frequency signal having the same information, and demodulating means for demodulating each frequency signal that has been diversity-combined by this means.

In this configuration, a high-frequency signal of the OFDM system, in which information of the same content is transmitted in a part or all of the carrier of a frequency band of different channels arranged in the vicinity, is converted into a time axis by one fast Fourier transformer. The above signal is converted into a signal on the frequency axis to separate information transmitted by the carrier of each frequency of the OFDM system, and the separated output of the signal received in the different frequency band is used as the carrier for transmitting the same information. It is characterized in that it is synthesized and demodulated every time.

(6) Different channels arranged in the vicinity
Receiving means for receiving a plurality of high-frequency signals of the OFDM system in which the same information is transmitted in a part or all of the carrier of the frequency band of the channel;
One fast Fourier transformer that converts the DM signal as one OFDM signal from the time axis to a signal on the frequency axis and separates the signal for each carrier, and the signal of each carrier obtained by this fast Fourier transformer Demodulation means for demodulating, and diversity combining means for diversity combining the demodulated signal for each carrier obtained by this means for each demodulated signal having the same information.

This configuration is based on different channels located in the vicinity.
OFD in which the same information is transmitted in some or all carriers received in the frequency band of the channel
An MFD high-frequency signal is converted from a signal on the time axis into a signal on the frequency axis by one fast Fourier transformer, and OFD is performed.
The information transmitted by the carrier of each frequency of the M system is separated, and after demodulating for each carrier, the demodulation output of the signal received in the different frequency band is obtained by the demodulation output obtained by the carrier transmitting the same information. It is characterized in that diversity synthesis is performed every time.

(7) In the configurations of (1) to (6), the diversity combining means uses a combining method by selecting each carrier constituting an OFDM signal.

(8) In the configurations of (1) to (6), the diversity combining means uses a combining method by addition including maximum ratio combining for each carrier constituting an OFDM signal.

(9) Receiving means for receiving a plurality of high-frequency signals of the OFDM system in which information having different contents is transmitted in at least a part of carrier waves in different frequency bands, and a plurality of high-frequency signals obtained by this means. Frequency conversion means for converting frequency bands of at least one high-frequency signal to make frequency bands substantially adjacent to each other, and combining means for combining a plurality of signals adjacent to each other into one OFDM signal And the O obtained by this means
One fast Fourier transformer for converting the FDM signal from a time axis to a signal on a frequency axis to separate the signal for each carrier, and one of the signals of each carrier obtained by the fast Fourier transformer. The apparatus includes signal selection means for selecting and outputting a signal having content information, and demodulation means for demodulating the signal selected by this means.

According to this configuration, at least one high-frequency signal among a plurality of high-frequency signals of the OFDM system in which information of different contents is transmitted in at least some of the carriers received in different frequency bands is frequency-converted. ,
By making the signals of the frequency bands substantially adjacent to each other, a synthesized signal by frequency division multiplexing is obtained, and the synthesized signal on the time axis is converted into a signal on the frequency axis by one fast Fourier transformer, and the carrier of each frequency in the OFDM system is used. The information to be transmitted is separated, and a part or all of the separated output of the signal received by the plurality of different frequency bands is selected and demodulated.

(10) Receiving means for receiving a plurality of OFDM high-frequency signals in which information having different contents is transmitted in at least a part of carrier waves of different frequency bands, and a plurality of high-frequency signals obtained by this means. Frequency conversion means for converting frequency bands of at least one high-frequency signal to make frequency bands substantially adjacent to each other, and combining means for combining a plurality of signals adjacent to each other into one OFDM signal And the O obtained by this means
One fast Fourier transformer for converting an FDM signal from a time axis to a signal on a frequency axis and separating the signal into signals for each carrier, and demodulating means for demodulating the signal of each carrier obtained by the fast Fourier transformer. Signal selecting means for selecting and outputting a demodulated signal having information of specified contents from the demodulated signals obtained by this means.

According to this configuration, at least one high-frequency signal among a plurality of high-frequency signals of the OFDM system in which information of different contents is transmitted in at least some of the carriers received in different frequency bands is frequency-converted. ,
By making the signals of the frequency bands substantially adjacent to each other, a synthesized signal by frequency division multiplexing is obtained, and the synthesized signal on the time axis is converted into a signal on the frequency axis by one fast Fourier transformer, and the carrier of each frequency in the OFDM system is used. After separating transmitted information and demodulating the information for each carrier, a part or all of the demodulated outputs of the signals received in the plurality of different frequency bands are selected and output.

(11) The different chips arranged in the vicinity
Receiving means for receiving a plurality of high-frequency signals of the OFDM system in which information having different contents is transmitted on at least a part of a carrier in a frequency band of a channel; and an OFDM signal obtained by this means as one OFDM signal on a time axis. A fast Fourier transformer that converts the signals into signals on the frequency axis and separates them into signals for each carrier, and a signal having information of specified contents among the signals of each carrier obtained by the fast Fourier transformer And a demodulating means for demodulating the signal selected by this means.

This configuration is based on different channels located in the vicinity.
OF with different information transmitted on at least some of the carriers received in the frequency band of the channel
The high-frequency signal of the DM system is converted into a synthesized signal by frequency division multiplexing, and the synthesized signal on the time axis is converted into a signal on the frequency axis by one fast Fourier transformer, and the information transmitted by the carrier wave of each frequency of the OFDM system is converted. And separating and demodulating a part or all of the separated outputs of the signals received by the plurality of different frequency bands.

(12) Different channels arranged in the vicinity
Receiving means for receiving a plurality of high-frequency signals of the OFDM system in which information having different contents is transmitted on at least a part of a carrier in a frequency band of a channel; and an OFDM signal obtained by this means as one OFDM signal on a time axis. A fast Fourier transformer that converts the signals into signals on the frequency axis and separates them into signals for each carrier, demodulating means for demodulating the signals of each carrier obtained by the fast Fourier transformer, and demodulation means obtained by this means. Signal selecting means for selecting and outputting a demodulated signal having information of specified contents from the demodulated signals.

This configuration is based on different channels located in the vicinity.
Information having different contents is transmitted in at least some of the carriers received in the frequency band of the channel.
A high-frequency signal of the FDM system is synthesized as a frequency division multiplexed signal, a synthesized signal on the time axis is converted into a signal on the frequency axis by one fast Fourier transformer, and information transmitted by a carrier of each frequency of the OFDM system is converted. After separating and demodulating for each carrier, a part or all of the demodulated outputs of the signals received in the plurality of different frequency bands are selected and output.

[0036]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 1A shows a configuration of an OFDM receiving apparatus according to a first embodiment of the present invention. In the receiving apparatus shown in FIG. 1A, the same frequency OF received by the receiving antennas 1 and 5 is used.
The high-frequency signals of the DM system are amplified by the reception high-frequency units 2 and 6, respectively, and input to the mixers 3 and 7. The mixers 3 and 7 are supplied with local oscillation signals of different but close frequencies from the local oscillators 4 and 8. For this reason, the mixers 3 and 7 output intermediate frequency signals having different and close frequencies. The intermediate frequency signals output from the mixers 3 and 7 are combined in a combiner 9. From the output of the synthesizer 9, the clock used in the receiving device is reproduced by the synchronizing circuit 10 and the A / D converter 11
Gives a digital signal.

[0038] This digital output is OF
After being converted into a signal corresponding to a carrier of each frequency constituting the DM signal, diversity-combined in the combining circuit 13, demodulated for each carrier in the carrier demodulation circuit 14, and subjected to error correction processing by the error correction circuit 15. , Are output as digital output data.

Next, the operation of this embodiment will be described with reference to FIG.
This will be described in detail with reference to FIG.

In the receiving apparatus shown in FIG. 1A, OFDM signals of the same frequency received by the antennas 1 and 5 are amplified by the receiving high-frequency units 2 and 6, respectively, and input to the mixers 3 and 7. The mixers 3 and 7 are supplied with local oscillation signals of different frequencies and close to each other from the local oscillators 4 and 8. For this reason, intermediate frequency signals having adjacent frequencies are output from the mixers 3 and 7, and are synthesized by the synthesizer 9 by frequency division multiplexing.

FIG. 1B is a diagram showing the relationship between the reception frequencies of the antennas 1 and 5 and the output frequency of the synthesizer 9. FIG.
ANT1, ANT2, and COMB in (B) correspond to the outputs of the antenna 1, the antenna 2, and the combiner 9 in FIG. The received signals 31 and 32 in FIG. 1 (B) are signals of the same frequency and have received the same transmission signal, but have received different phasing due to the different installation locations of the antennas 1 and 2. Signal.
The received signals 31 and 32 are different from each other, and are converted into substantially adjacent intermediate frequency signals 33 and 34 by frequency conversion using local oscillation frequencies that are close to each other.

The output of the synthesizer 9 in FIG. 1A is the intermediate frequency signals 33 and 34 shown in COMB in FIG. The signal indicated by COMB is a signal obtained by frequency division multiplexing of the signals received by the two antennas 1 and 2, and this intermediate frequency signal is collectively converted into a digital signal by the A / D converter 11, and further converted by the FFT 12. , The signals are collectively converted into signals corresponding to the carrier waves of each frequency. As a result,
As the output of the FFT 12, the carrier waves constituting the respective OFDM signals of the intermediate frequency signals 33 and 34 in FIG. 1B are independently obtained.

The output of the FFT 12 is subjected to diversity combining in the combining circuit 13. The diversity combining is performed by, for example, a carrier wave transmitting the same content among the carrier waves of the intermediate frequency signals 33 and 34, that is, the received signal 3
With respect to the carrier waves having the same frequency in 1 and 32, the magnitudes of the carrier waves are compared, and the larger one is selected and output. The combining circuit 13 selects and outputs all carrier waves.

The output of the synthesis circuit 13 is the carrier wave demodulation circuit 1
In 4, demodulation of carrier modulation, for example, demodulation of DQPSK or QPSK is performed for each carrier, and its output is output as digital data through an error correction process by an error correction circuit 15. The output of the synthesizer 9 is also connected to a synchronizing circuit 10 to reproduce a clock used in the receiving device. At this time, in the synchronous circuit 10,
The intermediate frequency signals 33 and 34 synthesized by the synthesizer 9 are handled as one signal.

In the above description, the case where selective combining is performed as a diversity combining method has been described as an example, but additive combining is also possible. In the case of addition synthesis, of the respective carrier waves of the intermediate frequency signals 33 and 34, a carrier wave transmitting the same content, that is, a carrier wave having the same frequency in the reception signals 31 and 32 is added and output. . At the time of addition, maximum ratio combining in which addition and combining are performed after multiplying by a multiplier proportional to the amplitude of each carrier wave is also possible.

Therefore, the receiving device having the above configuration can
Since the same signal received by the two antennas 1 and 2 is converted into a frequency division multiplexed signal at the intermediate frequency stage, a single A / D converter, FFT, and synchronization circuit can perform diversity combining processing. As a result, the overall configuration can be simplified and the cost can be reduced.

(Second Embodiment) FIG. 2 shows the configuration of an OFDM receiver according to a second embodiment of the present invention. In FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will not be repeated.

In the receiving apparatus shown in FIG. 2, the high frequency signal of the OFDM system received by the receiving antenna 1 is amplified by the receiving high frequency section 2 and input to the mixer 16.
The mixer 16 is supplied with a local oscillation signal having a frequency sufficient to slightly shift the high-frequency signal from the local oscillator 17. For this reason, the OFDM high-frequency signal input to the mixer 16 is slightly shifted in frequency, and
8 is input.

On the other hand, a signal having the same frequency as that received by the receiving antenna 1 is also received by the receiving antenna 5. The high-frequency signal obtained here is amplified in the reception high-frequency unit 6 and then input to the synthesizer 18 as it is.
The synthesizer 18 converts the high-frequency signal from the mixer 16 and the high-frequency signal from the reception high-frequency unit 6 into a frequency-division multiplexed signal. After being converted into an intermediate frequency signal by the local oscillation signal, the synchronization circuit 10 and the A / D converter 11
Is input to Thereafter, processing is performed in the same manner as in the first embodiment shown in FIG.

Next, the operation of this embodiment will be described.

In the receiving apparatus shown in FIG. 2, the high-frequency signal of the OFDM system received by the antenna 1 is amplified by the receiving high-frequency unit 2, and is mixed by the mixer 16 and the local oscillator 1.
After a slight frequency shift by 7, it is input to the synthesizer 18. On the other hand, the high-frequency signal received by the reception antenna 5 is amplified by the reception high-frequency unit 6 and then input to the synthesizer 18 as it is.

Although the signals received by the antennas 1 and 5 are the same transmission signal, the signal received from the antenna 1 is slightly shifted in frequency. Frequency division multiplexing is performed in stages. The output of the synthesizer 18 is
After being converted into an intermediate frequency signal by the local oscillator 20, the signal is input to the synchronization circuit 10 and the A / D converter 11.
The subsequent steps are the same as those in the first embodiment shown in FIG.

Therefore, the receiving apparatus having the above-mentioned configuration
Since the same signal received by the two antennas 1 and 2 is converted into a frequency division multiplexed signal at the high frequency stage and then converted into an intermediate frequency, one A is used as in the first embodiment.
The diversity combining process can be performed by the / D converter, the FFT, and the synchronization circuit, so that the overall configuration can be simplified and the cost can be reduced.

(Third Embodiment) FIG. 3A is a diagram showing the configuration of an OFDM receiving apparatus according to a third embodiment of the present invention. Note that, in FIG. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals, and duplicate description will be omitted.

In the receiving apparatus shown in FIG. 3A, the high-frequency signal of the OFDM system received by the receiving antenna 1 is amplified by the receiving high-frequency unit 2, and two frequency bands (channels) different from each other by the selective distributor 21. Are selected, and one is distributed to the mixer 3 and the other is distributed to the mixer 7. The local oscillation signals from the local oscillators 4 and 8 are supplied to the mixers 3 and 7, respectively, and the mixers 3 and 7 output signals converted to the intermediate frequency, respectively.
Here, the local oscillators 4 and 8 set the frequency of the local oscillation signal so that the signals after the frequency conversion of the mixers 3 and 7 are adjacent to each other. Frequency-converted mixers 3, 7
Is input to the synthesizer 9. Thereafter, processing is performed in the same manner as in the example of the first embodiment shown in FIG.

Next, the operation of the embodiment of the present invention will be described in detail with reference to FIG.

In the receiving apparatus shown in FIG. 3A, OFDM signals in two different frequency bands received by the antenna 1 are simultaneously amplified by the receiving high-frequency section 2 and selectively split into two by the selective splitter 16. Is done. The two outputs of the distributor 16 are input to the mixers 3 and 7, respectively. The mixers 3 and 7 are supplied with local oscillation signals of different frequencies from the local oscillators 4 and 8, respectively. 7
Output intermediate frequency signals having different frequencies, and are combined in the combiner 9.

FIG. 3B shows an OFDM signal of two different frequency bands received by the antenna 1 and a combiner 9.
FIG. 4 is a diagram showing a relationship between output frequencies of the first embodiment. FREQ1, FREQ2, and COMB in FIG.
2A corresponds to an OFDM signal of two different frequency bands received by the antenna 1 and an output of the combiner 9. It should be noted that different 2 received by the antenna 1
Received signals 35 and 36 of OFDM signals of two frequency bands
Are the effective symbol length and the guard interval length, respectively.
The intermediate frequency signals 37, 3
8 is converted to a frequency having an orthogonal relationship.

The received signals 35 and 36 in FIG. 3 (B) are signals of different frequency bands received by the same antenna 1, and here the received signals 35 and 36 have different frequencies but have the same transmission contents. Signals shall be included. Since the received signals 35 and 36 are signals transmitted at different frequencies and can be transmitted from different transmitting stations, they are signals that have undergone different phasing. The received signals 35 and 36 are converted into substantially adjacent intermediate frequency signals 37 and 38 by frequency conversion using different local oscillation frequencies.

The output of the synthesizer 9 in FIG. 3A is the intermediate frequency signals 37 and 38 shown in COMB in FIG. The signal shown in COMB is a signal in which two received signals are frequency-division multiplexed to substantially adjacent frequencies in the intermediate frequency signal, and the subsequent processing and effects will be described with reference to the first signal shown in FIG. This is the same as the embodiment.

Incidentally, also in the third embodiment, as a diversity combining method, selective combining and addition combining including maximum ratio addition are possible.

(Fourth Embodiment) FIG. 4 is a diagram showing the configuration of a fourth embodiment of an OFDM receiving apparatus according to the present invention. Note that, in FIG. 4, the same parts as those in FIGS. 2 and 3 are denoted by the same reference numerals, and redundant description is omitted here.

In the receiving apparatus shown in FIG. 4, an OFDM high-frequency signal received by the receiving antenna 1 is amplified by the receiving high-frequency section 2 and is combined with the mixer 16 for each signal of the selected frequency band by the selective distributor 21. Input to the container 18. The mixer 16 is provided with a selective distributor 21 from the local oscillator 17.
And a local oscillation signal required for frequency conversion by the mixer 16 so that the two output signals are substantially adjacent to each other. The output of the synthesizer 18 is converted into an intermediate frequency signal by the mixer 19 and the local oscillator 20, and the synchronizing circuit 10 and the A / D converter 1
1 is input. Thereafter, processing is performed in the same manner as in the third embodiment shown in FIG.

Next, the operation of this embodiment will be described.

In the receiving apparatus shown in FIG. 4, the high-frequency signals of the OFDM system received by the antenna 1 are amplified by the receiving high-frequency section 2 and different from each other by the selective distributor 21.
OFDM signal of the following frequency band is selectively applied to the mixer 16
Input to the synthesizer 18. Input to the mixer 16
The frequency of the signal is determined by the local oscillation signal of the local oscillator 17.
The number is converted and input to the synthesizer 18. At this time, mixing
The output of the combiner 16 and the input from the selective distributor 21 to the combiner 18
The frequency of the signal is approximately adjacent and each carrier
Are orthogonal so that the frequency of the local oscillator 17 is selected.
You. The mixer 16 is selectively arranged by the selective distributor 21.
The OFDM signal input to the synthesizer 18 is an effective symbol.
And the guard interval length are equal.
You.

At this time, the two signals synthesized by the frequency division multiplexing in the synthesizer 9 are signals received at different frequencies in the reception antenna 1 but include signals having the same transmission contents. And The subsequent steps are the same as those in the second embodiment shown in FIG.

In the case of the third and fourth embodiments,
Not all signals received in different frequency bands need to be the same, and even when the same information is transmitted only for some carriers, diversity reception can be performed only for those signals. Is clear.

(Fifth Embodiment) FIG. 5A is a diagram showing the configuration of an OFDM receiver according to a fifth embodiment of the present invention. In FIG. 5A, FIG.
The same parts as those in FIG. 1A are denoted by the same reference numerals, and duplicate description is omitted here.

The difference between the receiving device shown in FIG. 5A and the receiving device shown in FIG. 3A is that the combining circuit 1 shown in FIG.
3 is replaced by the program selection circuit 22.

Next, the operation of the embodiment of the present invention will be described in detail with reference to FIG.

In the receiving apparatus shown in FIG. 5A, OFDM signals of different frequency bands, in which different programs received by the antenna 1 are transmitted, are simultaneously amplified by the receiving high-frequency unit 2, It is selectively divided into two. The two outputs of the selective distributor 16 are input to the mixers 3 and 7, respectively. The mixers 3 and 7 are supplied with local oscillation signals having different frequencies from the local oscillators 4 and 8, respectively. , 7 output intermediate frequency signals having different frequencies, and are synthesized by the synthesizer 9.

FIG. 5B is a diagram showing the relationship between the OFDM signals of different frequency bands received by the antenna 1 and the output frequency of the combiner 9. FREQ in FIG. 5 (B)
1, FREQ2, and COMB correspond to OFDM signals in different frequency bands through which different programs received by the antenna 1 in FIG. 5A are transmitted, and the output of the synthesizer 9, respectively.

The received signals 39 and 40 in FIG. 5B are signals of different frequency bands received by the same antenna 1, and can be transmitted from different transmitting stations. The received signals 39 and 40 are converted into substantially adjacent intermediate frequency signals 4 by frequency conversion using different local oscillation frequencies.
1, 42.

The output of the synthesizer 9 in FIG. 5A is the intermediate frequency signals 41 and 42 shown in COMB in FIG. 5B. The signal shown in COMB is a signal obtained by frequency-division multiplexing two received signals into substantially adjacent frequencies in an intermediate frequency signal, and this intermediate frequency signal is output from the A / D converter 11.
Is converted into a digital signal at once, and then FFT
12, the signal is converted into a signal corresponding to a carrier wave of each frequency. As a result, the output of the FFT 12 is as shown in FIG.
OFDM of the intermediate frequency signals 41 and 42 at
The carriers that make up the signal are obtained independently. The output of the FFT 12 is input to the program selection circuit 22.

In the program selection circuit 22, the intermediate frequency signal 4
One and a plurality of carriers for transmitting a desired program are selected and output from the carriers 1 and 42 respectively. The output of the program selection circuit 22 is supplied to a carrier demodulation circuit 14 for demodulating carrier modulation for each carrier, for example, DQP.
SK or QPSK demodulation is performed, and the output is subjected to error correction processing by the error correction circuit 15 and output as digital data.

The output of the synthesizer 9 is also connected to a synchronizing circuit 10 to reproduce a clock used in the receiving device. At this time, in the synchronizing circuit 10, the synthesizer 9
Are handled as one signal. In the case of a receiving apparatus that receives only one normal band, for example, when switching from receiving the reception signal 39 to reception of the reception signal 40, it is necessary to newly perform synchronization pull-in by the synchronization circuit 10. There is,
In the case of the present embodiment, reception signal 3 shown in FIG.
The different programs received by the programs 9 and 40 need only be selected and switched by the program selection circuit 22, so that the synchronization circuit 10 does not need to perform a new synchronization pull-in operation and switches the programs to be received without waiting time. be able to.

(Sixth Embodiment) FIG. 6 is a diagram showing the configuration of an OFDM receiver according to a sixth embodiment of the present invention. In FIG. 6, the same parts as those in FIG. 4 are denoted by the same reference numerals, and the description thereof will not be repeated.

The receiving apparatus according to the present embodiment is obtained by replacing the synthesizing circuit 13 in the fourth embodiment shown in FIG. That is, the operation up to the FFT 12 is the same as that of the fourth embodiment shown in FIG.
Subsequent to the FFT 12, it is the same as the fifth embodiment shown in FIG. While the fourth embodiment shown in FIG. 4 is an embodiment in the case of diversity reception, this embodiment shows a configuration in which different programs are simultaneously received and selectively received. . The processing operation related to the selective reception is the same as in the fifth embodiment.

(Other Embodiments) In the embodiments shown in FIGS. 3 to 6, the case where signals in different frequency bands are processed by one reception high-frequency unit has been described. Obviously, the processing can be performed by the unit. In this case, it is possible to selectively amplify only the necessary frequency band in the reception high frequency unit.

The third, fourth, fifth and sixth embodiments shown in FIGS. 3 to 6 show the case where the two frequency bands to be received are separated frequencies. Obviously, the present invention can be implemented even when two frequency bands are substantially adjacent to each other. In this case, for example, in the receiving apparatus shown in FIG. 6, the selective distributor 21, the mixer 16, the local oscillator 17, and the synthesizer 18 become unnecessary, and the output of the reception high-frequency unit 2 is directly sent to the mixer 19. FIG. 7A is a diagram showing the frequency relationship in this case.

In FIG. 7A, the received signals 43 and 44 shown in FREQ1 are signals in substantially adjacent frequency bands, and the intermediate frequency signal 4 shown in FREQ2 is obtained by frequency conversion.
5 and 46. The intermediate frequency signals 45 and 46 are converted from a signal on the time axis into a signal on the frequency axis by one FFT circuit.

FIG. 7B shows the details of the carrier waves of the intermediate frequency signals 45 and 46 shown in FIG. 7A. OF
Since the DM system is a multi-carrier system, when transmitting a plurality of programs in one frequency band, for example, the reception signal 43 or the reception signal 44 shown in FIG. 7A, each program and a carrier wave for transmitting the program are transmitted. Can be made to correspond. FIG. 7B shows this state. The intermediate frequency signals 45 and 46 are respectively composed of carrier groups 47 to 51 and 52.
And carrier groups 47 to 51 are a group of carriers for transmitting different programs. Carrier group 5
The same applies to 2 to 56.

When signals having the same contents are transmitted in a part or all of the carrier groups 47 to 51 and a part or all of the carrier groups 52 to 56 shown in FIG. Alternatively, diversity combining by addition is possible. Also, when different programs are transmitted in part or all of the carrier groups 47 to 51 and part or all of the carrier groups 52 to 56, it is possible to switch programs with a short waiting time as described above.

In the above description, the diversity reception of two waves and the simultaneous reception of programs transmitted in two different frequency bands have been described. However, it is apparent that the present invention can be realized with signals of three or more waves.

In the above description, the case where the carrier wave is demodulated after the diversity combining or program selection is described. However, it is apparent that the diversity combining or the program selection can be performed after the carrier wave demodulation. . Specifically, in FIG. 1A, the connection order of the combining circuit 13 and the carrier demodulation circuit 14 may be reversed, and in FIG. 5A, the connection between the program selection circuit 22 and the carrier demodulation circuit 14 may be performed. The order may be reversed.

[0086]

The first effect of the present invention is that when an OFDM signal is received by antenna diversity, the required F
FT processing and clock recovery processing are performed by one F
It is to realize processing by an FT circuit and a synchronous circuit.

The second effect of the present invention is that an FF required when an OFDM signal is received by frequency diversity.
T processing and clock recovery processing, each one FF
It is to realize processing by a T circuit and a synchronous circuit.

A third effect of the present invention is to reduce a switching time when selecting a program in a different frequency band transmitted by an OFDM signal.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a first embodiment of an OFDM receiving apparatus according to the present invention and a diagram illustrating a frequency relationship between signals.

FIG. 2 is a block diagram illustrating a configuration of a second embodiment of an OFDM receiving apparatus according to the present invention.

FIG. 3 is a block diagram showing a configuration of a third embodiment of an OFDM receiving apparatus according to the present invention and a diagram showing a frequency relationship of signals.

FIG. 4 is a block diagram illustrating a configuration of a fourth embodiment of an OFDM receiving apparatus according to the present invention.

FIG. 5 is a block diagram showing a configuration of a fifth embodiment of an OFDM receiving apparatus according to the present invention and a diagram showing a frequency relationship of signals.

FIG. 6 is a block diagram showing a configuration of a sixth embodiment of an OFDM receiving apparatus according to the present invention.

FIG. 7 is a diagram illustrating a signal frequency relationship of another embodiment of the OFDM receiving apparatus according to the present invention.

FIG. 8 is a block diagram illustrating a configuration of a conventional diversity receiving apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 reception antenna 2 reception high frequency unit 3 mixer 4 local oscillator 5 reception antenna 6 reception high frequency unit 7 mixer 8 local oscillator 9 synthesizer 10 synchronization circuit 11 A / D converter 12 ... FFT 13 ... Synthesis circuit 14 ... Carrier wave demodulation circuit 15 ... Error correction circuit 16 ... Mixer 17 ... Local oscillator 18 ... Synthesizer 19 ... Mixer 20 ... Local oscillator 21 ... Selection distributor 22 ... Program selection circuit 31,32 ... Received signals 33, 34 ... Intermediate frequency signal 35, 36 ... Received signal 37, 38 ... Intermediate frequency signal 39, 40 ... Received signal 41, 42 ... Intermediate frequency signal 43, 44 ... Received signal 45, 46 ... Intermediate frequency signal 47 ~ 51: Carrier wave group 52-56: Carrier wave group A1, B1 ... Reception antenna A2, B2 ... Reception high frequency part A3, B3 ... Mixer A4, B4 ... Local oscillator A5, B5 ... Synchronization circuit A6 , B6 A / D converter A7, B7 FFT A8 Synthesis circuit A9 Carrier demodulation circuit A10 Error correction circuit

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-7-283801 (JP, A) JP-A-2-131629 (JP, A) JP-A-64-51838 (JP, A) JP-A-1- 136432 (JP, A) (58) Fields studied (Int. Cl. ⁶ , DB name) H04J 11/00 H04B 7/12

Claims (12)

(57) [Claims] 1. A receiving means for receiving, via a plurality of antennas, a high-frequency signal by an OFDM (Orthogonal Frequency Division Multiplexing) method in which information of the same frequency and the same content is transmitted, and a plurality of high-frequency signals obtained by this means. Frequency conversion means for converting frequency bands of at least one or more high-frequency signals so that frequency bands are approximately adjacent to each other; and combining means for synthesizing a plurality of signals adjacent to each other to form one OFDM signal. And one fast Fourier transformer for converting the OFDM signal obtained by this means from a time axis to a signal on a frequency axis and separating it into signals for each carrier, and each carrier obtained by this fast Fourier transformer. Diversity combining means for diversity combining the signals of each signal having information of the same content. OFDM, characterized by comprising a demodulation means for demodulating the wavenumber signal
System receiver. 2. A receiving means for receiving, via a plurality of antennas, a high-frequency signal by the OFDM system in which information of the same frequency and the same content is transmitted, and at least one of a plurality of high-frequency signals obtained by this means. Frequency conversion means for frequency-converting the high-frequency signals to make the frequencies substantially adjacent to each other; combining means for combining a plurality of signals adjacent to each other into one OFDM signal; A fast Fourier transformer for converting the OFDM signal from a time axis to a signal on a frequency axis and separating the signals into carrier signals, and demodulating means for demodulating the carrier signal obtained by the fast Fourier transformer And diversity combining means for diversity combining the demodulated signal for each carrier obtained by this means for each demodulated signal having the same information. O, characterized in that it comprises a
An FDM receiving device. 3. An OFDM system in which information having the same content is transmitted in a part or all of the carriers in different frequency bands.
Receiving means for receiving a plurality of high-frequency signals of the type, and frequency converting means for converting at least one high-frequency signal of the plurality of high-frequency signals obtained by this means into a frequency band substantially adjacent to each other by frequency-converting at least one high-frequency signal. Combining means for combining a plurality of signals adjacent to each other by this means to form one OFDM signal; and converting the OFDM signal obtained by this means from a time axis to a signal on a frequency axis, and A fast Fourier transformer that separates the signals into two signals, and diversity combining means for diversity combining the signals of the respective carriers obtained by the fast Fourier transformer for each signal having the same information. Diversity combining by this means And demodulating means for demodulating each of the frequency signals thus obtained.
System receiver. 4. An OFDM system in which information having the same content is transmitted in some or all of the carriers in different frequency bands.
Receiving means for receiving a plurality of high-frequency signals of a type, and frequency conversion for making frequency bands substantially adjacent to each other by frequency-converting at least one or more of the high-frequency signals obtained by the means. Means for synthesizing a plurality of signals adjacent to each other by this means to form one OFDM signal; and converting the OFDM signal obtained by this means from a time axis to a signal on a frequency axis to generate a carrier wave. A fast Fourier transformer that separates each carrier signal into demodulated signals, demodulating means for demodulating each carrier wave signal obtained by the fast Fourier transformer, and a demodulated signal for each carrier wave obtained by this means. Diversity combining means for performing diversity combining for each demodulated signal having information.
An FDM receiving device. 5. A mutually different channel disposed in the vicinity.
Receiving means for receiving a plurality of high-frequency signals of the OFDM system in which the same information is transmitted on a part or all of the carrier waves in the frequency band of the above, and the OFDM signal obtained by this means is converted into one OFDM signal on the time axis. A fast Fourier transformer that converts the signal into a signal on the frequency axis and separates it into a signal for each carrier, and a signal for each carrier obtained by this fast Fourier transformer for each frequency signal having the same information An OFDM system comprising: diversity combining means for performing diversity combining; and demodulating means for demodulating each frequency signal subjected to diversity combining by the means.
System receiver. 6. A mutually different channel disposed in the vicinity.
Receiving means for receiving a plurality of high-frequency signals of the OFDM system in which the same information is transmitted on a part or all of the carrier waves in the frequency band of the above, and the OFDM signal obtained by this means is converted into one OFDM signal on the time axis. A fast Fourier transformer that converts the signal into a signal on the frequency axis and separates it into a signal for each carrier; demodulating means for demodulating the signal of each carrier obtained by the fast Fourier transformer; And diversity combining means for diversity combining the demodulated signal for each carrier wave for each demodulated signal having the same information.
An FDM receiving device. 7. The diversity combining means includes an OFDM signal.
5. A method according to claim 1, wherein a combining method is selected by selecting each carrier constituting a signal of the method.
7. The receiving device of the OFDM system according to any one of 6. 8. The diversity combining means includes an OFDM signal.
2. A combination method using addition including maximum ratio combination for each carrier constituting a signal of the method.
7. The receiving device according to any one of 2, 3, 4, 5, and 6. 9. An OFD in which information having different contents is transmitted on at least a part of carriers in different frequency bands.
Receiving means for receiving a plurality of high-frequency signals of the M type; and frequency conversion for making frequency bands substantially adjacent to each other by frequency-converting at least one high-frequency signal among the plurality of high-frequency signals obtained by this means. Means for synthesizing a plurality of signals adjacent to each other by this means to form one OFDM signal; and converting the OFDM signal obtained by this means from a time axis to a signal on a frequency axis to generate a carrier wave. A fast Fourier transformer that separates the signals into individual signals; a signal selecting unit that selects and outputs a signal having information of specified contents among the signals of the respective carrier waves obtained by the fast Fourier transformer; And a demodulating means for demodulating the signal selected in (1). 10. An OF in which information having different contents is transmitted on at least a part of carriers in different frequency bands.
Receiving means for receiving a plurality of high-frequency signals of the DM system; and frequency conversion for making at least one or more high-frequency signals of the plurality of high-frequency signals obtained by this means substantially adjacent to each other by frequency-converting the high-frequency signals. Means for synthesizing a plurality of signals adjacent to each other by this means to form one OFDM signal; and converting the OFDM signal obtained by this means from a time axis to a signal on a frequency axis to generate a carrier wave. A fast Fourier transformer for separating the signals into individual signals, demodulating means for demodulating the signals of the respective carriers obtained by the fast Fourier transformer, and a content designated from among the demodulated signals obtained by the means. Signal receiving means for selecting and outputting a demodulated signal having information. 11. Different channels arranged in the vicinity.
Receiving means for receiving a plurality of OFDM high-frequency signals in which information having different contents is transmitted on at least a part of a carrier in a frequency band of the OFDM system, and using the OFDM signals obtained by the means as one OFDM signal on a time axis. A fast Fourier transformer that converts the signal into a signal on the frequency axis and separates it into a signal for each carrier, and a signal having information of specified contents among the signals of each carrier obtained by the fast Fourier transformer And a demodulation means for demodulating the signal selected by the means. 12. Different channels arranged in the vicinity.
Receiving means for receiving a plurality of OFDM high-frequency signals in which information having different contents is transmitted on at least a part of a carrier in a frequency band of the OFDM system, and using the OFDM signals obtained by the means as one OFDM signal on a time axis. A fast Fourier transformer that converts the signal into a signal on the frequency axis and separates it into a signal for each carrier; demodulating means for demodulating the signal of each carrier obtained by the fast Fourier transformer; Signal receiving means for selecting and outputting a demodulated signal having information of specified contents from the demodulated signals.