JPH11186879A - Ofdm broadcast receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To tune an orthogonal frequency division modulation system OFDM broadcast program automatically by identifying the program from a television broadcast program. SOLUTION: The OFDM broadcast receiver that receives an OFDM broadcast wave where lots of orthogonal subcarriers are phase-modulated is provided with an amplifier/intermediate frequency conversion section 2 that tunes to a broadcast frequency, a 1st band pass filter 3 that passes tuned subcarriers, a demodulation section 4 that takes synchronization with the subcarriers via the 1st band pass filter after tuning, applies fast Fourier transform FFT processing to the synchronized subcarriers to adjust a frequency deviation, a control section 6 that stops frequency shift in the amplifier/intermediate frequency conversion section 2 to allow the demodulation section to conduct FFT processing, a 2nd narrow band pass filter 7 that passes only part of subcarriers passing through the 1st pass band, and a level detection section 8 that shifts and integrates the level of the subcarriers passing through the 2nd narrow band pass filter and identifies reception of an OFDM broadcast or a TV broadcast based on the result of shift and integration. In the case of identifying the TV broadcast, the FFT processing is inhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an orthogonal frequency division modulation system (OF) used for digital audio broadcasting (DAB).
More specifically, the present invention relates to a receiver for performing automatic tuning (auto search) on a broadcast frequency.

[0002]

2. Description of the Related Art FIG. 13 is a diagram for explaining an automatic search of a conventional OFDM receiver. As shown in this figure, OFD
The M receiver is mounted on a mobile body, and includes an antenna 1 for receiving a broadcast signal, and an amplification / intermediate converter (RF / I) for amplifying a received signal of the antenna 1 and performing down-conversion.
F) Amplification / 2 having a bandwidth of, for example, 1.5 MHz
First bandpass filter 3 connected to intermediate conversion unit 2
And a demodulation unit 4 connected to the first band-pass filter 3 and demodulating a large number of phase-modulated subcarriers.

[0003] The demodulation unit 4 includes an A / D converter 41 for converting a signal from the band-pass filter 3 from analog to digital.
And a result obtained by a fast Fourier transformer (FFT) 42 for performing frequency analysis (FFT processing) of a large number of subcarriers by Fourier transform to obtain an amplitude, a phase, and the like of each subcarrier, and a result obtained by the fast Fourier transformer 42 A decoding unit 43 for encoding and performing processing such as error detection of a code, and a frequency for detecting a frequency shift (allowable frequency shift is 2%) based on a processing result of the fast Fourier transformer 42 and performing frequency adjustment. And a shift detection unit 44.

Further, a comparator 5 for comparing an S level indicating an AGC (automatic gain control) voltage or the like generated by the amplification / intermediate converter 2 with a threshold value _Vr1 , and an S level and an output signal of the comparator 5 are inputted and amplified. A microcomputer (control unit) 6 for setting a reception frequency for down-conversion is provided in the / intermediate conversion unit 2. When the mobile device travels in a place where a normal activity is performed, the microcomputer automatically tunes a down-converted broadcast station to a known broadcast station based on the S level in the preset mode. When the moving object moves from a place where normal activities are performed to a new place, a frequency is set in a certain frequency step (frequency shift) for down-conversion, and the broadcasting station is automatically set based on the S level. Search (tune).

FIG. 14 is a diagram for explaining signals received by an OFDM receiver. As shown in this figure, there is a null signal having a signal level of zero between frame signals, a synchronization symbol is provided at the head of the frame signal, and thereafter a number of symbols for providing a service are provided. One symbol is composed of a card interval for removing the effect of multipath and an effective symbol. The effective symbol is composed of a number of subcarriers having orthogonality, for example, 1 in a frequency band of about 1.5 MHz in mode I. 536 subcarriers are provided at 1 KHz intervals. The transmission length of one symbol is 1.25 ms, and the transmission length of one frame is 96 ms.

In the fast Fourier transformer 42, it is necessary to synchronize in order to perform Fourier processing on the effective symbols. This synchronization is determined based on a null signal and a synchronization symbol at the head of the frame. Therefore, to achieve this synchronization, approximately 96 ms is required because the transmission length of one frame is 96 ms. If the FFT processing is performed without synchronization, the FFT processing is performed between symbols.
This is because processing is performed, and interference between symbols occurs.

[0007] At the center of the effective symbol, the amplitude of the subcarrier is zero in order to detect a small frequency shift described later. The frequency shift detection unit 44 makes fine adjustment of the frequency set based on the S level by utilizing the fact that the amplitude of the subcarrier is zero at the center of the effective symbol. That is, if the setting of the reception frequency from the microcomputer 6 is shifted, the amplitude of the subcarriers on both sides of the center is biased. The reason why the frequency is finely adjusted is that the frequency shift is required to be 2% or less in order to ensure the orthogonality of the subcarriers.

FIG. 15 shows the microcomputer 6 shown in FIG.
4 is a flowchart for explaining a series of operations of FIG. In step S1, it is determined whether the moving object is located at a new location. This determination may be made by an external input, or may be made by detecting a search failure in the preset mode. If the mobile unit is located in the normal activity place in step S2, the search in the professional mode is performed, and the end processing is performed.

If the mobile unit is located at a new activity place in step S3, the frequency at which down-conversion is performed is shifted by 16 KHz (search). In step S4, it is determined whether the S level is _{equal to} or greater than the threshold value _Vr1 . If the S level is less than the threshold value _Vr1 , the process returns to step S3. Step S
If the S level is _equal to the threshold value _{Vr1 in} 5, the search is stopped.

In step S6, the search is stopped, so that the fast Fourier transform (FFT) 42 performs the fast Fourier transform (FFT) based on the null signal and the synchronization symbol. In step S7, the frequency shift detector 44 detects a frequency shift based on the center carrier.
In step S8, when the frequency shift signal is input, the frequency of the down-conversion is finely adjusted, and the process returns to step S6 in order to synchronize and perform the FFT processing again.

In step S9, if there is no deviation in the frequency deviation signal, it is determined that the frequency has been determined. In step S10, the degree of error occurrence is determined based on the error detection signal from the decoding unit 43. If the occurrence of the error is large, the process returns to step S3, and if the occurrence of the error is small, an end process is performed.

The error detection signal generated in step S10 may be caused by fading due to multipath, but may include the reception of a television broadcast. This is because the broadcast frequency band of the OFDM broadcast is provided between the broadcast frequency bands of the television broadcast.

[0013]

By the way, the processing from step S6 to step S9 in FIG. 14 is usually repeated several times, and synchronization processing, FFT processing and frequency adjustment are performed, and the frequency is determined. This determination takes several hundred ms. For this reason, when a television broadcast is received, a wasteful time is required for this processing, and there is a problem that the original OFDM search speed is reduced.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an OFDM receiver which can quickly and automatically tune an OFDM broadcast even when the frequency bands of the television broadcast signal are adjacent to each other in view of the above problems. .

[0015]

SUMMARY OF THE INVENTION The present invention is directed to a television broadcast, an FM broadcast and an AM broadcast.
An OFD broadcast M having a broadcast frequency band adjacent to at least one broadcast frequency band of a broadcast and receiving an OFDM broadcast in which each of a plurality of orthogonal subcarriers is phase-modulated and broadcast.
In a receiver, an amplification / intermediate conversion unit for amplifying a received signal and tuning to a reception broadcast frequency, and a first unit for passing only a subcarrier obtained by tuning the amplification / intermediate conversion unit
After tuning to the received broadcast frequency,
The Fourier transform processing is performed by synchronizing the subcarriers that have passed through the first band-pass filter, and the Fourier transform is performed again to adjust the tuning frequency shift obtained based on the subcarriers after the Fourier transform processing. The demodulation unit to be performed and the received broadcast frequency to be set in the amplification / intermediate conversion unit are step-controlled by frequency shift, and the frequency shift is stopped by receiving the S level indicating that the tuning has been obtained from the amplification / intermediate conversion unit. A control unit for causing the demodulation unit to perform a Fourier transform; and a second unit for branching the output of the first bandpass and passing only a part of the subcarriers passing through the first bandpass. Moving and integrating the level of the amplitude of the sub-carrier passing through the narrow band-pass filter and the second narrow band-pass filter for each of the frequency shifts Receiving or television broadcast OFDM broadcast based on the partial results, a level detecting unit for performing at least one of the reception of the identification of the FM broadcast and AM broadcast,
When the control unit determines that at least one of the television broadcast, the FM broadcast, and the AM broadcast is received based on the identification result of the level detection unit, the control unit stops the frequency shift by receiving the S level and performs a Fourier transform on the demodulation unit. In this case, the frequency shift is restarted to tune the frequency of the amplification / intermediate conversion unit.

An OFD broadcast having a broadcast frequency band adjacent to at least one broadcast frequency band of a television broadcast, an FM broadcast, and an AM broadcast, and receiving an OFDM broadcast in which each of a plurality of orthogonal subcarriers is phase-modulated and broadcast. An M / A receiver, an amplifying / intermediate converter for amplifying a received signal and tuning to a received broadcast frequency; a demodulator for performing a Fourier transform process on a subcarrier obtained by tuning the amplifying / intermediate converter; / A control unit for step-controlling the reception broadcast frequency to be set in the intermediate conversion unit by a frequency shift, and averaging the amplitudes of the subcarriers obtained by the Fourier transform processing of the demodulation unit, based on the result of the amplitude average value. Reception of OFDM broadcast or television broadcast,
An amplitude averaging unit for identifying at least one reception of FM broadcast and AM broadcast; and the control unit stops frequency shift and synchronizes by receiving an S level indicating that tuning has been obtained from the amplification / intermediate conversion unit. Without causing the demodulation unit to perform a Fourier transform process. If it is determined that at least one of the television broadcast, the FM broadcast, and the AM broadcast is received based on the identification result of the amplitude averaging unit, the frequency shift is resumed and the amplification / intermediation is performed. When the frequency of the conversion unit is tuned, and when it is determined that the broadcast is OFDM broadcast, the Fourier transform process is performed in synchronization with the Fourier transform process. Is performed.

By this means, television broadcasting, FM
Since at least one of the broadcast and the AM broadcast is not subjected to the synchronized FFT processing and the frequency adjustment, the frequency band arrangement of at least one signal of the television broadcast, the FM broadcast and the AM broadcast is adjacent. Even OFDM
Since the FFT processing and the frequency adjustment are performed only in synchronization with respect to the broadcast, the OFDM broadcast can be quickly and automatically tuned.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an OFDM according to the present invention.
It is a figure explaining an auto search of a receiver. 13 is different from FIG. 13 in that the output branch signal of the first band-pass filter 3 is further input and the first band-pass filter 3
And a second analog narrow-band analog filter 7 that has a frequency band narrower than that of the second narrow-band analog filter and allows a part of the subcarriers to pass through. An output signal of the second narrow-band analog filter 7 is rectified, envelope-detected, and integrated. A level detector 8 for detecting an integrated level of a subcarrier in a lever frequency band; a comparator 9 for comparing an output level of the level detector 8 with a threshold V _r2 and outputting the result to a microcomputer 6
Is provided. In this way, the moving integral of the level of the subcarrier is obtained along with the frequency shift, and it becomes possible for the comparator 9 to keep outputting the high level from the homogenous tendency of the amplitude of the subcarrier and to identify the OFDM broadcast. . Microcomputer 6 receives O from comparator 9
The receiving frequency is set and controlled using the FDM identification signal.

FIG. 2 is a diagram for explaining an example of an OFDM channel arrangement. As shown in this figure, 170 to 200 MH
In the frequency range of z, for example, one television broadcast wave is divided into four blocks having a bandwidth of 1.5 MHz between television broadcast channels having a bandwidth of 7 MHz. There is a card band. The number of stereo audio channels in the 1.5 MHz band is four to six.
FM broadcasting and AM broadcasting may be present in addition to television broadcasting.

As shown in FIG. 2, in the OFDM spectrum, subcarriers are arranged at a constant frequency interval and a constant amplitude. In addition, television broadcasting includes video signals, audio signals,
Synchronous signals are compounded, and the amplitude of the frequency spectrum fluctuates due to the luminance component of the video signal, as shown in FIG. In particular, the carrier is amplitude-modulated by the video signal.

FIG. 3 is a diagram for explaining the movement integration of the amplitude of the subcarrier by the narrow band analog filter 7 and the level detector 8. As shown in the figure, the subcarrier gradually approaches the band of the second narrow band analog filter 7 due to the frequency shift of 16 KHz by the microcomputer 6. The second narrow band analog filter 7 is set at an end in the filter 3 and closer to the head of the subcarrier. The bandwidth of the second narrow band filter 7 is 100 to 200.
KHz, preferably 160 KHz. In addition,
Tuning is established by a frequency shift of 1500 kHz / 16 kHzＫ94 times after the head of the subcarrier reaches the end of the second narrow band filter 7. Note that, as described above, the frequency shift is determined in consideration of setting the frequency shift to 2% or less in order to ensure the orthogonality of the subcarriers.

Specifically, the second narrowband analog filter 7 includes 160 subcarriers out of 1536 subcarriers, and the level detector 8 calculates the integral of the amplitude of the 160 subcarriers. Done. With one frequency shift, 16 of the 160 subcarriers included in the second narrowband analog filter 7 are sequentially switched. Each time the switching is performed, the level detector 8 performs the moving integration of the amplitudes of the 160 subcarriers.

FIG. 4 is a diagram for explaining the difference in the moving integral between the subcarrier of OFDM and the carrier of television broadcasting. As shown in the figure, since the amplitude of the subcarrier of the OFDM broadcast is constant, the movement integral is constant. As described above, the carrier of the television broadcast is amplitude-modulated by the video signal, and the amplitude of the carrier of the television broadcast varies, so that the moving integral also varies. Therefore, by monitoring the moving integral, it becomes possible to distinguish between the OFDM broadcast and the television broadcast.

FIG. 5 is a flowchart for explaining a series of operations of the microcomputer 6 of FIG. Steps S11 to S13 and S19 to S25 are the same as steps S1 to S10 in FIG.
Description is omitted. In step S14, it is determined whether the identification signal of the comparator 9 is at a high level. Step S15
If the level is high, the number I of high levels is counted.
If it is low in step S16, the number J of low levels is counted.

In step S17, the ratio P at which the identification signal becomes high with respect to the frequency shift is obtained as follows. P = {I / (I + J)} × 100 (%) In step S18, it is determined whether P ≧ 70%. However, for example, it is assumed that I ≧ 10 times. If this condition is met,
This means that the level of the output signal of the level detector 8 is uniform and not fluctuating. If this condition is not satisfied, the process returns to step S13. When this condition is satisfied, the process proceeds to step S19.

That is, if it is not possible to identify an OFDM broadcast by the identification signal, it can be determined that a television broadcast is being received in this case, so that the frequency shift is steadily advanced. That is, even if the S level in step S19 satisfies the threshold value V _r1 , the search is not stopped, the FFT processing is performed in synchronization, and the frequency is not finely adjusted. Therefore, useless delay of tuning by television broadcasting is eliminated.

FIG. 6 is a diagram showing a modification of the filter 7. As shown in the figure, the second narrow band analog filter 7
Instead, a second narrow-band digital filter 71 for inputting the branch signal of the A / D converter 41 of the demodulation unit 4 may be provided. This simplifies the configuration. FIG. 7 is a diagram illustrating another example of the auto search of the OFDM receiver according to the present invention. 13 is different from FIG. 13 in that
A subcarrier averaging unit 10 for averaging the amplitude of the subcarrier as an output result of the fast Fourier transformer 42, and comparing the output signal level of the subcarrier amplitude averaging unit 10 with a threshold V _r3 and outputting the output of the subcarrier amplitude averaging unit 10 When the level of the signal is large, the comparator 11 outputs a high level to the microcomputer 6, and outputs an identification signal indicating that the signal is OFDM to the microcomputer 6.

FIG. 8 shows the subcarrier amplitude averaging unit 10 shown in FIG.
It is a figure explaining operation of. As shown in the figure, the subcarrier amplitude averaging unit 10 averages some amplitudes of the subcarriers, which are output results of the fast Fourier transformer 42. The subcarrier amplitude averaging unit 10 averages the amplitude of the subcarrier when the fast Fourier transformer 42 performs the FFT processing without synchronization. In an unsynchronized state, there is inter-symbol interference, and the amplitudes of the subcarriers vary individually, but become substantially constant by taking some averages.
For example, the average of the amplitude of 16 subcarriers (16 KHz width) is taken.

FIG. 9 is a flowchart for explaining a series of operations of the microcomputer 6 of FIG. Steps S31 to S35 and S38 to S42 are the same as steps S1 to S10 in FIG.
Description is omitted. In step S36, the fast Fourier transform unit 42 performs the FFT processing without synchronization after stopping the frequency shift.

In step S37, the subcarrier amplitude averaging unit 10 averages several amplitudes of the subcarriers, compares this average value with the threshold value _Vr3 , and compares the average value with the threshold value _Vr3.
If it is less, the process returns to step S33. If the average value is less than the threshold value V _r3, the reception of the television broadcast is not the reception of the OFDM broadcast, and thus the frequency shift that has been suspended is started and the frequency shift is advanced. Therefore, the synchronized FFT processing is not performed at the time of receiving a television broadcast, so that the search speed is increased. If the average value is equal to or _larger than the threshold value Vr3, the process proceeds to step S28, where the fast Fourier transform unit 42 is synchronized with the fast Fourier transform unit 42 to perform full-scale FFT processing.

FIG. 10 shows the subcarrier amplitude averaging unit 1 shown in FIG.
It is a figure showing another example of 0. Subcarrier amplitude averaging unit 1
M consisting of several sub-carriers with 0 as 0
And a plurality of subcarrier amplitude averaging sections 10-1 for averaging subcarrier amplitudes in each group
Is provided. Next, each of the average values and the threshold value V
If outputs the average value is less than the threshold V _r3 to "1" if the average value is the threshold value V _r3 or compare the _r3 and a plurality of comparators 11-1 outputs "0", the comparators 11-1
And a comparator 13 for comparing the result of the summing unit 12 with a threshold value m ₀ (m ₀ (integer) <m). In this way, if the amplitude average of the m subcarriers is greater than or equal to the threshold value V _{r3, the} OFDM broadcast is determined to be received if m ₀ or greater, and if less than m ₀ , the television broadcast is determined to be received. Identification information is provided to the microcomputer 6.

FIG. 11 is a diagram for explaining another example of the auto search of the OFDM receiver according to the present invention, and FIG.
4 is a flowchart illustrating a series of operations of one microcomputer 6. 11 is a combination of the configurations of FIGS. 1 and 7, and FIG. 12 is a combination of the flowcharts of FIGS. That is,
The microcomputer 6 inputs a signal passing through the second narrowband analog filter 7, the level detector 8, and the comparator 9 as an identification signal A, and a signal passing through the subcarrier amplitude averaging unit 10 and the comparator 11 as an identification signal B. . According to the embodiment of the present invention, two identification signals A, B
Thus, since the OFDM broadcast and the television broadcast are discriminated twice, only the auto search of the OFDM broadcast can be performed more accurately.

[0033]

As described above, according to the present invention, the synchronized FFT processing and the frequency adjustment are not performed on the television broadcast, so that the arrangement of the frequency band of the television broadcast signal can be improved. Even when adjacent to each other, FFT processing and frequency adjustment are performed in synchronization only for OFDM broadcasting, so that OFDM broadcasting can be quickly and automatically tuned.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an auto search of an OFDM receiver according to the present invention.

FIG. 2 is a diagram illustrating an example of an OFDM channel arrangement.

FIG. 3 shows a narrow band analog filter 7 and a level detector 8
FIG. 9 is a diagram for explaining the integration of the movement of the amplitude of the subcarrier due to the following.

FIG. 4 is a diagram for explaining a difference in a moving integral between an OFDM subcarrier and a television broadcast carrier.

FIG. 5 is a flowchart illustrating a series of operations of the microcomputer 6 of FIG.

FIG. 6 is a diagram showing a modification of the filter 7;

FIG. 7 is a diagram illustrating another example of the auto search of the OFDM receiver according to the present invention.

FIG. 8 is a diagram illustrating the operation of the subcarrier amplitude averaging unit 10 of FIG.

FIG. 9 is a flowchart illustrating a series of operations of the microcomputer 6 of FIG. 7;

FIG. 10 is a diagram illustrating another example of the subcarrier amplitude averaging unit 10 of FIG. 7;

FIG. 11 is a diagram illustrating another example of the auto search of the OFDM receiver according to the present invention.

FIG. 12 is a flowchart illustrating a series of operations of the microcomputer 6 of FIG.

FIG. 13 is a diagram illustrating an auto search of a conventional OFDM receiver.

FIG. 14 is a diagram illustrating a signal received by an OFDM receiver.

FIG. 15 is a flowchart illustrating a series of operations of the microcomputer 6 of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Antenna 2 ... Amplification / intermediate conversion 3 ... 1st band-pass filter 4 ... Demodulation part 5, 9, 11 ... Comparator 6 ... Microcomputer 7 ... 2nd narrow band analog filter 8 ... Level detector 10 ... Sub Carrier amplitude averaging unit 41 A / D conversion unit 42 Fast Fourier transformation unit 43 Decoded part 44 Frequency shift detector 71 Narrow band digital filter

Claims (11)

[Claims] 1. An OFDM broadcast having a broadcast frequency band adjacent to at least one broadcast frequency band of a television broadcast, an FM broadcast, and an AM broadcast, wherein each of a plurality of orthogonal subcarriers is phase-modulated and broadcast. In an OFD broadcast M receiver, an amplifying / intermediate converter for amplifying a received signal and tuning to a received broadcast frequency, and a first band-pass filter for passing only subcarriers obtained by tuning the amplifying / intermediate converter And after performing tuning to the reception broadcast frequency, performing a Fourier transform process in synchronization with the subcarriers passing through the first band-pass filter, and obtaining a tuning frequency shift obtained based on the subcarriers after the Fourier transform process. A demodulation unit that performs a Fourier transform again in order to perform the adjustment of the reception broadcast frequency to be set in the amplification / intermediate conversion unit. A control unit for performing step control by shifting, stopping a frequency shift by receiving an S level indicating that tuning has been obtained from the amplification / intermediate conversion unit, and causing the demodulation unit to perform Fourier transform; A second narrow band-pass filter that branches the output of the pass and passes only some of the sub-carriers that pass through the first band-pass, and a sub-carrier that has passed through the second narrow-band filter. A level detection unit that performs movement integration of the amplitude level for each of the frequency shifts and performs identification of reception of an OFDM broadcast or at least one of a television broadcast, an FM broadcast, and an AM broadcast based on a result of the movement integration; When the control unit determines that at least one of the television broadcast, the FM broadcast, and the AM broadcast is received based on the identification result of the level detection unit, An OFD characterized in that the frequency shift is stopped by reception and the demodulation unit is inhibited from performing the Fourier transform, and the frequency shift is restarted to tune to the amplification / intermediate conversion unit frequency.
M broadcast receiving device. 2. The frequency bandwidth of the second narrow band-pass filter is obtained by taking a moving average of the amplitude of a subcarrier moving by a frequency shift, and obtaining at least one of a television broadcast, an FM broadcast and an AM broadcast and an OFDM broadcast. 2. The OFDM broadcast receiving apparatus according to claim 1, wherein the width is suitable for identifying the OFDM broadcast. 3. The frequency band of the second narrow band-pass filter is gradually shifted within the frequency band of the first band-pass filter by the frequency shift so that the head of the subcarrier is gradually shifted to the first band-pass filter. The OFDM broadcast receiving apparatus according to claim 1, wherein the OFDM broadcast receiving apparatus is set on a side closer to an end. 4. The OFDM broadcast receiving apparatus according to claim 1, wherein the second narrow band pass filter is formed in an analog form. 5. The OFDM broadcast receiving apparatus according to claim 1, wherein the second narrow band pass filter is formed in a digital form. 6. An OFDM broadcast having a broadcast frequency band adjacent to at least one broadcast frequency band of a television broadcast, an FM broadcast and an AM broadcast, wherein each of a plurality of orthogonal subcarriers is phase-modulated and broadcast. In an OFD broadcast M receiver, an amplifying / intermediate converter for amplifying a received signal and tuning to a received broadcast frequency; a demodulator for performing Fourier transform processing on subcarriers obtained by tuning the amplifying / intermediate converter; A control unit for step-controlling the reception broadcast frequency to be set in the amplification / intermediate conversion unit by frequency shift; and averaging the amplitudes of the subcarriers obtained by the Fourier transform processing of the demodulation unit, to obtain an average amplitude value. O based
An amplitude averaging unit for discriminating whether to receive an FDM broadcast or at least one of a television broadcast, an FM broadcast, and an AM broadcast; and the control unit indicates that tuning has been obtained from the amplification / intermediate conversion unit. If the frequency shift is stopped by receiving the level and the demodulation unit performs Fourier transform processing without synchronization, and if it is determined that at least one of the television broadcast, the FM broadcast, and the AM broadcast is received based on the identification result of the amplitude averaging unit, The frequency shift is restarted to tune to the frequency of the amplifying / intermediate conversion unit. If it is determined that the broadcast is OFDM broadcasting, a synchronization is performed and a Fourier transform process is performed, and a tuning frequency obtained based on the subcarrier after the Fourier transform process An OFDM broadcast receiving apparatus for performing a Fourier transform again to adjust a shift. 7. The OFDM broadcast receiving apparatus according to claim 6, wherein the amplitude averaging unit averages a partial amplitude of the subcarrier. 8. The amplitude averaging unit divides subcarriers into groups, averages the amplitudes of the subcarriers in the group, and performs an OF based on the average amplitude of the subcarriers in each group.
The OFDM broadcast receiving apparatus according to claim 6, wherein whether the reception is a DM broadcast or at least one of a television broadcast, an FM broadcast, and an AM broadcast is identified. 9. The OFDM broadcast receiving apparatus according to claim 1, wherein the amount of the frequency shift is determined based on an allowable frequency deviation of tuning. 10. The control unit determines that OFDM broadcast is received, stops frequency shift, causes the demodulation unit to perform Fourier transform processing, and then decodes the code. 7. The reception of an OFDM broadcast according to claim 1, wherein a current reception state is maintained, and if an error occurrence is large, a frequency shift is performed to tune the frequency of the amplification / intermediate conversion unit. apparatus. 11. Television broadcasting, FM broadcasting and AM
An OFD broadcast receiver having a broadcast frequency band adjacent to at least one broadcast frequency band of a broadcast and receiving an OFDM broadcast in which each of a number of orthogonal sub-carriers is phase-modulated and broadcast, amplifies and receives a received signal. An amplifying / intermediate converter for tuning to a desired broadcast frequency; a first band-pass filter for passing only subcarriers obtained by tuning of the amplifying / intermediate converter; and a signal for passing through the first band-pass filter A demodulation unit for performing a Fourier transform process on the subcarrier; a control unit for step-controlling a reception broadcast frequency to be set in the amplification / intermediate conversion unit by frequency shift; a branch for dividing the first band-pass output; A second narrow band-pass filter that passes only some of the sub-carriers that pass through the first band pass; The level of the amplitude of the subcarrier that has passed through the filter is moved and integrated for each frequency shift, and based on the result of the moving integration, identification of reception of OFDM broadcast or reception of at least one of television broadcast, FM broadcast and AM broadcast is performed. A level detection unit to perform, and average the amplitudes of the subcarriers obtained by the Fourier transform processing of the demodulation unit.
An amplitude averaging unit for discriminating whether to receive an FDM broadcast or at least one of a television broadcast, an FM broadcast, and an AM broadcast; and the control unit controls an OFD based on an identification result of the level detection unit.
After determining that the reception of the M broadcast has been received, the reception of the S level indicating that the tuning has been obtained from the amplification / intermediate conversion unit stops the frequency shift and causes the demodulation unit to perform Fourier transform processing without synchronization. If it is determined that the broadcast is OFDM based on the identification result of the amplitude averaging unit, a Fourier transform process is performed in synchronization with the OFDM broadcast, and a Fourier transform is performed again to adjust a tuning frequency shift obtained based on the subcarriers after the Fourier transform process. OF characterized by performing conversion
DM broadcast receiving device.