JP3955977B2 - OFDM receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an OFDM (Orthogonal Frequency Division Multiplex) receiver.
[0002]
[Prior art]
ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) has two types of broadcasting, TV broadcasting and audio broadcasting. The ISDB-T receiver has 13 segments for TV broadcasting and 3 segments for audio broadcasting. Alternatively, one segment of an OFDM modulated wave is received. Therefore, in an ISDB-T receiver that can select 13, 3 and 1 segment reception and select the bandwidth of the band limiting filter of the tuner, it is for band limiting according to the number of segments (band) of the received OFDM modulated wave. It is necessary to select the bandwidth of the filter, and if it is attempted to receive a TV broadcast with a 3-segment or 1-segment bandwidth limiting filter, or conversely, an audio broadcast with a 13-segment bandwidth limiting filter. There is a possibility that the receiving operation does not work properly.
[0003]
[Problems to be solved by the invention]
The bandwidth of the band limiting filter is selected by a user operation. However, since the bandwidth of the band limiting filter can only be switched at the time of receiving an audio broadcast, it is easy to forget to change it, and the correct band limiting filter corresponding to the broadcasting form is not selected. The broadcast may not be received normally.
[0004]
The present invention has been made in view of the above points, and an OFDM receiver that can prevent a broadcast from being normally received due to a difference in the bandwidth of a selected band limiting filter and the number of segments of a received signal ( An object of the ISDB-T receiver is to provide one specific example thereof.
[0005]
[Means for Solving the Problems]
The present invention includes a band width of the filter for band limitation is selected, by comparing the number of segments received signal, if they are different is the also broadcast informs the user by such display or warning sound.
[0006]
Therefore, the OFDM receiver according to the present invention includes a selection means for manually selecting a bandwidth of a band limiting filter used in the tuner, and a currently received signal that is received and demodulated by the tuner and the demodulator. The detection means for detecting the number of segments, and the number of segments detected by the detection means are compared with the bandwidth of the band limiting filter selected by the selection means, and output when the bandwidth does not match the number of segments. And a notifying unit for notifying when an output is generated from the comparing unit.
[0007]
OFDM receiver of the present invention as described above, the number of segments detected by the detection means is supplied to the tuner, band corresponding to the band width of the filter for the band-limited to be used in the tuner of the number of said segments A setting means for automatically setting the width; a switching means for switching whether to operate the setting means or the selection means; a means for setting whether the operation of the notification unit is turned on or off; Can further be provided.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of an OFDM receiver according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of an OFDM receiver according to the present invention (used as an ISDB-T receiver). In this figure, the tuner 12 has a band limiting filter, extracts a desired signal (desired OFDM modulation wave) from the RF signal captured by the antenna 11, converts it to an IF signal, and outputs it. The demodulator 13 demodulates the IF signal output from the tuner 12 and outputs a TS (transport stream). The demodulator 13 receives the IF signal output from the tuner 12 and detects the number of segments of the currently received signal (OFDM modulated wave currently being received). That is, control information called TMCC is included in the modulated wave of OFDM, and at least one is inserted in the band of one segment depending on the transmission mode and the modulation method. Therefore, for example, TMCC can be obtained even when a 13-segment broadcast is received with a 1-segment band limiting filter selected. This TMCC includes a parameter “number of segments”, which is the number of segments (bandwidth) of the actually transmitted OFDM modulated wave. The demodulator 13 detects the number of segments in the TMCC and outputs the “number of received segments” that is the number of segments of the signal currently being received.
[0010]
The band limiting filter selection input unit 14 is where the user selects and inputs the bandwidth of the band limiting filter used in the tuner 12. When the user selects a band limiting filter corresponding to any one of the 13, 3 and 1 segments at the band limiting filter selection input unit 14, the tuner 12 has the number of segments corresponding to the selected filter. The receiving operation is performed on the signal.
[0011]
The bandwidth information of the band limiting filter output from the band limiting filter selection input unit 14 to select the bandwidth of the band limiting filter of the tuner 12 and the number of received segments output from the demodulating unit 13 are It is switched at 15 and supplied to the tuner 12. The switch 15 is switched by a signal from the automatic switching on / off input unit 16. The automatic switching on / off input unit 16 is where the user sets whether to turn on or off the automatic switching of the band limiting filter.
[0012]
Further, the bandwidth information of the band limiting filter output from the band limiting filter selection input unit 14 and the number of received segments output from the demodulation unit 13 are supplied to the segment comparison unit 17. The segment comparing unit 17 compares the bandwidth information of the band limiting filter output from the band limiting filter selection input unit 14 with the number of received segments output from the demodulating unit 13. Deriving the output. The output derived from the segment comparison unit 17 is supplied to the notification unit 19 via the switch 18. When the output from the segment comparison unit 17 is supplied to the notification unit 19 (that is, the bandwidth limitation filter bandwidth information output from the band limitation filter selection input unit 14 and the demodulation unit 13). The fact that the number of received segments is different) is notified to the user by an indicator, display display, warning sound, or vibration (in the case of a portable receiver). The switch 18 is turned on and off by a signal from the notification on / off input unit 20. The notification on / off input unit 20 is where the user sets whether the notification operation by the notification unit 19 is turned on or off.
[0013]
In the OFDM receiver as described above, now, the switch 15 is operated by the signal from the automatic switching on / off input unit 16 under the operation of the user by the band limiting filter selection input unit 14 side (that is, the band limiting filter Since the bandwidth information from the band limiting filter selection input unit 14 is supplied to the tuner 12 when connected to the automatic switching off), the bandwidth of the band limiting filter used in the tuner 12 is the bandwidth information and the bandwidth information. The same thing is selected and set. The tuner 12 and the demodulator 13 receive and demodulate the signal, and the demodulator 13 outputs a TS. At the same time, the demodulator 13 determines the number of received segments representing the number of segments of the currently received signal. Is output.
[0014]
The number of received segments is compared with the bandwidth information output from the band limiting filter selection input unit 14 (that is, the bandwidth of the band limiting filter selected and set in the tuner 12) by the segment comparison unit 17. . If the number of received segments is different from the bandwidth information (that is, the bandwidth of the bandwidth limiting filter selected and set in the tuner 12), an output is derived from the segment comparison unit 17, and this output is switched to 18 to the notification unit 19.
[0015]
Therefore, the notification unit 19 uses that the number of segments of the signal currently being received and the bandwidth of the band limiting filter selected and set in the tuner 12 differ depending on the indicator, display display, warning sound, or vibration. Inform the person. The user notices the above difference by this notification and operates the band limiting filter selection input unit 14 to change the bandwidth information, thereby changing the bandwidth of the band limiting filter selected and set in the tuner 12. Match the number of segments of the signal currently being received. As a result, it is possible to prevent an erroneous reception operation due to a difference between the bandwidth of the band limiting filter selected and set in the tuner 12 and the number of segments of the currently received signal, and normal normal reception is possible. . At this time, of course, the switch 18 is turned on by a signal from the notification on / off input unit 20. The notification operation can be turned off by turning off the switch 18 by a signal from the notification on / off input unit 20 under the operation of the user.
[0016]
On the other hand, when the switch 15 is connected to the demodulation unit 13 side (that is, automatic switching on of the band limiting filter on) by a signal from the automatic switching on / off input unit 16 under the operation of the user, the tuner 12 Instead of the bandwidth information from the limiting filter selection input unit 14, the number of received segments from the demodulation unit 13 is supplied. Then, the tuner 12 sets the bandwidth of the band limiting filter selected and set in the tuner 12 to a bandwidth that matches the supplied reception segment by the automatic setting means provided therein. Therefore, in this case as well, the bandwidth of the band limiting filter selected and set in the tuner 12 can be matched with the number of segments of the signal currently being received, thereby preventing an erroneous reception operation due to the mismatch and Good reception is possible. At this time, although the above-described notification operation can be turned on, in order to prevent erroneous notification, it is desirable to turn off the switch 18 to turn off the above-described notification operation.
[0017]
In the above description, the OFDM receiver capable of receiving all of the 13, 3 and 1 segments has been described as an example. However, two or more types of bandwidths for the band limiting filter such as a 3 and 1 segment receiver can be selected. The same can be applied to the OFDM receiver.
[0018]
【The invention's effect】
As described above in detail, according to the OFDM receiver of the present invention, an erroneous reception operation caused by a difference between the bandwidth of the band limiting filter selected and set in the tuner and the number of segments of the currently received signal. Thus, normal good reception is possible.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of an OFDM receiver according to the present invention.
[Explanation of symbols]
12 Tuner 13 Demodulation Unit 14 Band Limit Filter Selection Input Units 15 and 18 Switch 16 Automatic Switching On / Off Input Unit 17 Segment Comparison Unit 19 Notification Unit 20 Notification On / Off Input Unit

Claims (2)

A selection means for manually selecting the bandwidth of the band limiting filter used in the tuner;
Detecting means for detecting the number of segments of the currently received signal received and demodulated by the tuner and demodulator;
A comparison unit that compares the number of segments detected by the detection unit with the bandwidth of the band limiting filter selected by the selection unit, and generates an output when the bandwidth and the number of segments do not match;
An OFDM receiver comprising: a notification unit that performs notification when an output is generated from the comparison unit. Setting means for supplying a number of segments detected by the detection means to the tuner automatically sets the bandwidth of the filter for the band-limited to be used in the tuner bandwidth corresponding to the number of said segments,
Switching means for switching between operating this setting means or operating the selection means;
Means for setting whether to turn on or off the operation of the notification unit;
The OFDM receiver according to claim 1, further comprising:

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