JP2006067186A - Dab broadcasting receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DAB receiver capable of determining a receiving-signal level proper to DAB broadcast waves. <P>SOLUTION: When the error-rate value 6-1 of an output from an error-rate detecting means 6 for a Viterbi decoder 4 surpasses a certain specified value; a receiving signal is regarded as disturbance waves, and the absence of the receiving signal is determined. The error-rate value is divided into first specified steps and converted into the receiving-signal level within a first range during a time when the error-rate value is made lower than the certain specified value and reaches 0. The receiving-signal intensity 5-1 of an output from a receiving-signal intensity detecting means 5 for a tuner 2 is divided into a second specified step within the range of 0 of the error-rate value, and converted into the receiving-signal level within a second range continuing to the first range and displayed by a display unit 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a DAB (Digital Audio Broadcasting) broadcast receiver capable of appropriately displaying a received signal level based on a received signal intensity and an error rate value of a broadcast wave.

  In recent years, projects that provide terrestrial digital audio broadcasting, mainly in Europe and the United States, are becoming popular. One of such projects, European DAB (Digital Audio Broadcasting), has almost all Western European service areas and is gradually spreading to Canada and some Asian countries.

  2. Description of the Related Art Conventionally, as a digital broadcast receiving apparatus that appropriately displays a received signal level, a digital broadcast receiving apparatus that displays an input electric field strength and a received signal quality converted from an error rate value at the same time is known ( Patent Document 1).

Further, in the eighth embodiment of Patent Document 1, for the digital satellite broadcast receiver, both data of the input level based on the AGC voltage and the received signal quality based on the error rate are combined and displayed as the digital signal quality. An example is given.
Japanese Patent No. 3272246

  In such a conventional digital broadcast receiver, the problem to be solved is that a satellite broadcast receiver having a small input radio wave DR (dynamic range) uses an AGC voltage generated in a tuner for use in an electric field strength signal. In this case, relatively good linearity can be obtained. However, in DAB using terrestrial transmission media, the DR of the input radio wave is large. Therefore, in order to ensure signal quality, a DAB broadcast receiver using a plurality of AGC circuits is used. Realized. Therefore, when the output of the AGC circuit described above is used, the linearity is poor and it is inappropriate to know the input electric field strength.

  Further, in the above-described embodiment in Patent Document 1, the reception level is displayed using the AGC voltage even when the error rate is extremely high. In such a case, the reception signal is actually desired as an interference wave or the like. It is often not a DAB broadcast wave, and it is not appropriate to display it as a received signal level.

  Further, in the above-described embodiment, even when the error rate value is not 0, the AGC voltage is used to display the reception level. In such a case, even if the reception signal strength is large, the signal quality is an error. Since it is not free, it is not appropriate to display the received signal level larger.

  An object of the present invention is to provide a DAB receiver provided with a received signal level display means more suitable for DAB broadcast waves.

  The DAB broadcast receiver according to the present invention includes a tuner including a received signal strength detecting unit for detecting a received signal strength, and a Viterbi decoding unit including an error rate detecting unit for detecting an error rate value. The DAB reception signal level is displayed by a predetermined means.

  The invention according to claim 1 of the present invention is a DAB broadcast receiver, comprising a tuner provided with a received signal strength detecting means for detecting a received signal strength of a DAB broadcast wave entering the receiver, and the tuner. An OFDM demodulator that demodulates the intermediate frequency band signal, a Viterbi decoder having an error rate detector that detects an error rate value of the signal demodulated by the OFDM demodulator, and a detection by the received signal strength detector A control unit that converts the received signal strength and the error rate value detected by the error rate detection unit into a received signal level using a predetermined unit, and the predetermined unit includes the error rate When the value exceeds a predetermined value, the received signal is regarded as an interference signal and no received signal is detected, and the error rate value is less than the predetermined value and becomes zero. During this period, the error rate value is divided into first predetermined stages and converted to a received signal level in a first range. When the error rate value becomes 0, the received signal strength is set to a second level. Is divided into predetermined stages and converted to a received signal level in a second range following the first range, and whether or not a desired DAB broadcast wave can be received. Can be reliably determined, and the reception signal level suitable for the DAB broadcast wave that is the ground wave can be used to know a wider range of reception signal levels.

  In the DAB broadcast receiver according to the present invention, when the error rate value exceeds a predetermined value, the received signal is regarded as an interference wave and no received signal is present, and the error rate value becomes 0 below the predetermined value. Until the error rate value is divided into a first predetermined stage and converted to a received signal level in a first range, and when the error rate value becomes 0, the received signal strength is Since it can be divided into two predetermined stages, converted into a received signal level in the second range following the first range, and displayed, it can be reliably determined whether or not the desired DAB broadcast wave can be received. In addition, since it is possible to display a wider range of received signal levels using received signal strengths suitable for DAB broadcast waves that are terrestrial waves, the user can appropriately and widely know the signal levels of DAB broadcast waves. That There is a point.

  Hereinafter, the best mode for carrying out the DAB broadcast receiver of the present invention will be described in detail with reference to FIGS. FIG. 1 is a block diagram showing the configuration of a DAB broadcast receiver according to an embodiment of the present invention, FIG. 2 is a diagram showing a conversion method from an error rate to a received signal level in the same operation example, and FIG. It is a figure which shows the conversion method from the received signal strength in FIG.

  In FIG. 1, the DAB broadcast receiver is configured in an antenna 1, a tuner unit 2, an OFDM demodulation unit 3, a Viterbi decoding unit 4, a received signal strength detection means 5 configured in the tuner unit 2, and a Viterbi decoding unit 4. The error rate detecting means 6, the control unit 11, and the display unit 12 are included.

  The operation of the DAB broadcast receiver configured as described above will be described below. In FIG. 1, in the DAB broadcast receiver, the DAB broadcast wave signal received by the antenna 1 is supplied to the tuner unit 2, and a desired broadcast reception frequency signal is frequency-converted into an intermediate frequency signal. Then, this intermediate frequency signal is supplied to the OFDM demodulator 3 and demodulated into a bit stream. The bit stream is error-corrected by the Viterbi decoder 4, and the error-corrected bit stream is sent to a service selector or voice demodulator (not shown). It can be heard through a speaker and an earphone (not shown).

  The tuner unit 2 is provided with reception signal strength detection means 5 for detecting the reception signal strength of the received desired broadcast reception frequency signal, and the control means 11 obtains the reception signal strength (Rssi) 5-1 as the detection result. Have been able to get.

  Here, in many cases, the AGC output is generally used as the received signal strength, but in the present invention, an Rssi (Received Signal Strength Indicator) output is used. This is because, as described in the problem to be solved by the invention, the European DAB broadcast receiver generally has a multi-stage AGC, so that the output linearity is difficult.

  The Viterbi demodulator 4 is provided with an error rate detection means 6 for detecting an error rate value of the input bit stream so that the control means 11 can obtain an error rate value 6-1 as the detection result. Has been. As a method for detecting the error rate value, for example, a method is used in which the input bit stream and the bit rate after error correction obtained as a result of Viterbi decoding are compared and the ratio of the difference is set to the error rate value 6-1.

  The control unit 11 includes predetermined means (described later) for converting the received signal strength 5-1 and the error rate value 6-1 obtained as described above into a received signal level 11-1, and the converted received signal level 11- 1 is output to the display unit 12.

Hereinafter, predetermined means for converting the received signal strength 5-1 and the error rate value 6-1 to the received signal level 11-1 will be described. First, the incoming signal by an error rate value 6-1 (in FIG. 2 denoted by R _n) determines whether the desired wave or interference wave. As shown in FIG. 2, when the error rate value 6-1 exceeds a predetermined value (indicated by R ₀ in FIG. 2), the received signal is not a desired wave such as an interference wave even if the received signal strength is high. It is determined that it is a thing, and “no signal” is set. As a result, when the received signal level 11-1 is not “no signal”, it is possible to indicate to the user that at least the DAB broadcast wave that is the desired wave is being received.

Next, the error rate value 6-1 is divided into first predetermined stages (denoted by n in FIG. 2) until the error rate value 6-1 falls below the predetermined value R ₀ and becomes 0. Then, the received signal level is converted to the first range. In the example of FIG. 2, each of error rate values R0, R1,..., Rn (= 0) is used as a threshold value, and reception in a first range of 0 (= minimum level), 1,. Use signal level.

  As a result, the user can be informed of a certain level of received signal level, but generally the error rate value has a low dynamic range, and the first predetermined stage cannot be made too large. In general, if the error rate value is 0, there is no problem in audio playback, but even if the error rate value is 0, it is possible to receive with sufficient margin, or the error rate immediately due to external effects such as noise. It cannot be distinguished whether the value is not zero.

Therefore, in the range where the error rate value is 0, the received signal strength (Rssi) output is divided into second predetermined stages (denoted by m in FIG. 3) as shown in FIG. To the received signal level in the second range following the above. In the example of FIG. 3, received signal strengths S _{n + 1} , S _{n + 2} ,..., S _{n + m} are used as threshold values, and n + 1, n + 2,. The received signal level is in the range of 2.

Here, in the method of determining the threshold values _{Sn + 1} , _{Sn + 2} ,..., _{Sn + m} , in order to prevent the influence of the tuner variation or the like, for example, a DAB signal having a predetermined strength at the time of shipment from the factory is used. A method is conceivable in which, for example, a received signal strength (Rssi) output value corresponding to a DAB signal having the specified strength is input and stored as each threshold value.

  As a result, the level of the received signal can be made wider, and even in a state where there is no problem in sound reproduction, the user can know whether the signal is received with a sufficient margin, for example, It is possible to adjust the antenna direction so that a higher reception level can be obtained.

  The display unit 12 may use a level meter, display the bar graph by changing the length according to the level, display a number, or change the color according to the received signal level. May be.

  As described above, according to the present embodiment, it is possible to reliably determine whether or not a desired DAB broadcast wave can be received, and a wider range of reception using the received signal intensity suitable for a DAB broadcast wave that is a terrestrial wave. Since the signal level can be displayed, there is an advantage that the user can appropriately and widely know the signal level of the DAB broadcast wave.

  According to the present invention, it is possible to reliably determine whether or not a desired DAB broadcast wave can be received with a simple configuration, and to use a received signal intensity suitable for a DAB broadcast wave that is a terrestrial wave. Since the level display can be performed, the user can appropriately and widely know the signal level of the DAB broadcast wave, and the industrial applicability is high.

The block diagram which shows the structure of the DAB broadcast receiver in one Embodiment of this invention. The figure which similarly shows the conversion method from the error rate in the operation example to the reception signal level The figure which similarly shows the conversion method from the received signal strength to the received signal level in the operation example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 Tuner 3 OFDM demodulation part 4 Viterbi decoding part 5 Received signal strength detection means 5-1 Received signal strength (Rssi)
6 Error rate detection means 6-1 Error rate value 11 Control unit 11-1 Received signal level 12 Display unit

Claims (2)

A tuner provided with a received signal strength detecting means for detecting a received signal strength of a DAB broadcast wave entering the receiver;
An OFDM demodulator for demodulating an intermediate frequency band signal generated by the tuner;
A Viterbi decoding unit comprising error rate detection means for detecting an error rate value of the signal demodulated by the OFDM demodulation unit;
A control unit that converts the received signal strength detected by the received signal strength detecting unit and the error rate value detected by the error rate detecting unit together into a received signal level by a predetermined unit;
With the predetermined means, if the error rate value exceeds a predetermined value, the received signal is regarded as an interference wave and no received signal is present.
Until the error rate value falls below the certain predetermined value to 0, the error rate value is divided into first predetermined stages and converted to a received signal level in a first range,
When the error rate value becomes 0, the received signal strength is divided into a second predetermined stage and converted to a received signal level in a second range following the first range. DAB broadcast receiver. 2. The DAB broadcast receiver according to claim 1, further comprising a display unit for displaying the converted received signal level in the first range and the received signal level in the second range.

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