JP3651434B2 - Portable digital broadcast receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a portable digital broadcast receiver, and more particularly to a portable digital broadcast receiver suitable for application to a terrestrial digital television broadcast receiver and a terrestrial digital radio broadcast receiver.
[0002]
[Prior art]
Unlike a fixed digital broadcast receiver, a portable digital broadcast receiver is often used by a user while walking or getting on a transportation vehicle or the like.
This portable digital broadcast receiver normally receives radio waves (broadcast waves) from a broadcast station normally within the service area of the broadcast station.
[0003]
However, the reception state may fluctuate greatly with changes in the surrounding environment such as a building shadow or inside a tunnel.
If the reception state deteriorates due to this variation, the portable digital broadcast receiver not only cannot obtain normal video and audio, but also consumes wasted power.
In particular, in battery-powered portable digital broadcast receivers, it is a problem to reduce power consumption as much as possible.
[0004]
Conventionally, various improvements have been proposed as a technique for solving this problem.
For example, Japanese Patent Application Laid-Open No. 2001-7720 discloses an example of a conventional technique for improving the malfunction of the AM demodulating circuit due to the variation in reception intensity when the reception state deteriorates, that is, when the reception intensity is weak, to save power. It is disclosed as a radio beacon receiver.
[0005]
The radio beacon receiver disclosed in this publication detects the strength of a high-frequency signal input from an antenna by an electric field strength detection means, and the detected electric field strength is below a reference level (a level at which the AM demodulation circuit does not operate normally). In some cases, the power of the AM demodulation circuit is turned off to stop the operation of the AM demodulation circuit.
With such a configuration, the conventional radio beacon receiver can prevent malfunction of the AM demodulating circuit and suppress wasteful power consumption.
[0006]
Another example of a conventional technique for suppressing useless power consumption generated in a digital broadcast receiver is disclosed in Japanese Patent Application Laid-Open No. 11-008601 as a digital broadcast receiver.
The digital broadcast receiver disclosed in this publication is provided with a detection circuit for detecting whether or not the received digital signal is synchronized, and based on the detection signal indicating that the synchronization is lost, the decoder circuit and this The operation by the clock of the circuits after the circuit is stopped. With such a configuration, useless power consumption can be suppressed.
[0007]
[Problems to be solved by the invention]
However, in the conventional radio wave beacon receiver method, the digital signal processing LSI that constitutes the digital demodulation circuit of the digital broadcast receiver requires various internal settings when the power is turned on or the reception channel is set. When the power of the demodulating circuit is turned off and then the power is turned on due to improvement of reception intensity, etc., it is necessary to perform the internal setting again.
Therefore, with the conventional radio wave beacon receiver method, the digital broadcast receiver cannot be promptly restored even if the reception intensity is improved.
[0008]
Further, in the conventional radio beacon receiver method, the circuit is complicated in the digital broadcast receiver, so that it is difficult to reduce the size and weight and to reduce the cost.
In particular, in a CMOS circuit of a digital signal processing LSI, in order to prevent a failure due to a latch-up phenomenon and wasteful power consumption, a current flows between a circuit that is turned on and a circuit that is turned off. Therefore, it is necessary to insert switch means for each of the many input / output signals of the digital signal processing LSI. This complicates the circuit by increasing the number of components and increasing the circuit scale.
[0009]
Further, in the conventional radio wave beacon receiver method, in a digital broadcast receiver, transmission parameters (for example, modulation schemes such as QAM and PSK, encoding, etc., which are set for each broadcast channel or each program by a broadcaster of digital broadcast) Rate value).
This is because the reception intensity necessary for the normal operation of the demodulation circuit differs depending on the transmission parameter, and the reference level switching process is not performed when the transmission parameter is switched.
[0010]
On the other hand, conventional digital broadcast receivers have the effect of suppressing wasteful power consumption by stopping the operation of the circuits subsequent to the decoder means when the synchronization of the received digital signals is out of sync.
However, even if the received digital signal is synchronized, a normal output may not be obtained, and the effect is not sufficient.
[0011]
For example, even if synchronization is achieved when the reception level is low, the error rate when the received digital signal is decoded exceeds the upper limit of the error rate necessary for obtaining a normal output in the circuit after the decoder means. There was a case.
In this case, not only a normal output cannot be obtained, but also power is wasted in the decoder circuit and subsequent circuits, so that the effect of the conventional digital broadcast receiver is not sufficient. there were.
[0012]
The present invention has been made to solve the above-described problem, and suppresses wasteful power consumption in an internal circuit when normal audio / video output cannot be obtained due to deterioration of the reception state due to environmental changes or the like. This is a portable digital device that can maintain the internal state with a simple configuration, shorten the recovery time of audio / video output when the reception strength is restored, and can also switch between multiple transmission parameters. The purpose is to provide a broadcast receiver.
[0013]
[Means for Solving the Problems]
  In order to achieve this object, a portable digital broadcast receiver according to claim 1 of the present invention includes a tuner for selecting a selected broadcast signal from a broadcast wave, and decoding the selected broadcast signal from the tuner to obtain video data. And a portable digital broadcast receiver comprising a decoder means for reproducing audio data, a clock means for supplying a clock signal to the decoder means, and a control means for controlling the supply of the clock signal. When the reception level value from the tuner is smaller than the reference level value, the control means stops supplying the clock to the decoder means.The decoder means has a TMCC decoding unit for detecting the modulation method and coding rate from the broadcast wave, and this TMCC decoding unit is an interrupt indicating that the modulation method and / or coding rate of the broadcast wave has been switched. The signal is sent to the control means, and the control means takes out the reference level corresponding to the combination of the modulation method and coding rate after the switching indicated by the interrupt signal from the storage means, and the reception level is higher than the value of the extracted reference level. When the value of is small, supply of the clock to the decoder means is stopped.As a configuration.
[0014]
When the portable digital broadcast receiver has such a configuration, when the reception level value of the broadcast wave is smaller than the reference level value, the supply of the clock to the circuits after the decoder means is stopped, so that the normal output In the case where the signal cannot be obtained, wasteful power consumption in the circuits after the decoder means can be suppressed.
[0015]
Further, in the conventional radio beacon receiver, the operation of the digital demodulation circuit is stopped by turning off the power of the digital demodulation circuit. Therefore, when the reception strength is improved, the setting process (initial setting) is performed. In the present invention, although it is necessary to correct the delay, the operation in the circuit after the decoder means is stopped by stopping the supply of the clock signal to the circuit. Therefore, the setting process when the reception intensity is improved is performed. There is no need to do it again.
[0016]
That is, in the present invention, in order to stop the operation of the circuit after the decoder means without turning off the power of the circuit, the internal state of the digital signal processing LSI constituting the circuit is the reception intensity of the broadcast wave. It will be maintained without disappearing with the decrease of. For this reason, it is not necessary to perform the setting process again when the reception strength is improved.
Therefore, it is possible to shorten the return time of video output and audio output when the reception intensity of the broadcast wave is recovered.
[0017]
Since the operation of the circuit after the decoder means is stopped by stopping the supply of the clock signal, the conventional technique used for preventing failure due to the latch-up phenomenon of the CMOS circuit and suppressing wasteful power consumption. The switch means becomes unnecessary. For this reason, since the number of circuit components can be reduced, the circuit can be simplified, reduced in size and weight, and the cost can be reduced.
In addition, in order to control the supply of the clock signal to the circuits after the decoder means based on the reception level of the broadcast wave, the reference level is set for each broadcast wave transmission parameter (combination of modulation method, coding rate, etc.). By setting it, it becomes possible to cope with the difference in the modulation method.
[0018]
Furthermore, even when the broadcast wave is synchronized, if the broadcast wave reception level is not at a level that can obtain normal audio / video output, the clock signal to the circuit after the decoder means is obtained. Is stopped, and wasteful power consumption in the circuits after the decoder means can be suppressed.
[0019]
In particular, in the conventional digital broadcast receiver, when the received digital signal is not synchronized, the operation of the circuit after the decoder means is stopped, but the received digital signal is synchronized. However, in practice, a normal output cannot be obtained because the reception level is low, and this causes wasteful power consumption in the circuits after the decoder means.
On the other hand, the portable digital broadcast receiver of the present invention realizes the stop of the operation in the circuit after the decoder means when the reception level is lower than the reference level. Greater power consumption reduction effect can be expected.
[0020]
  Further, when the portable digital broadcast receiver has such a configuration, when the modulation method or coding rate of the broadcast wave is switched based on a change in the broadcast channel or program content, an interrupt indicating that the switch has been made. Since the signal is notified from the decoder means to the control means, the control means can newly set a reference level based on the interrupt signal and execute a comparison process with the reception level.
  That is, the control unit does not need to regularly monitor the modulation scheme and coding rate. Therefore, it is possible to improve the efficiency of the operation in the control unit.
[0028]
  Claims2In the portable digital broadcast receiver described above, when the reception level value becomes larger than the reference level value after the supply of the clock to the decoder unit is stopped, the control unit supplies the clock to the decoder unit. Is configured to resume.
  If the portable digital broadcast receiver has such a configuration, when the reception level of the broadcast wave is restored to a level sufficient to obtain normal audio output and video output, the supply of the clock to the decoder means is controlled. Since the processing is resumed by the means, the control means can stop the supply of the clock signal to the circuits subsequent to the decoder means only when the reception level is lower than the reference level.
[0029]
Furthermore, since the supply control of the clock signal to the decoder means is executed based on the result of comparison between the broadcast wave reception level and the reference level in the control means, normal audio output and video output cannot be obtained. It is possible to suppress wasteful power consumption in the circuits subsequent to the decoder means with a simple configuration.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[First embodiment]
First, a first embodiment of the portable digital broadcast receiver of the present invention will be described with reference to FIG.
FIG. 2 is a block diagram showing the configuration of the portable digital broadcast receiver of this embodiment.
[0031]
As shown in the figure, the portable digital broadcast receiver 10 includes a tuner 11, an antenna 12, an OFDM demodulator 13, an MPEG decoder 14, a VRAM 15, a display unit 16, an A / D converter 17, and a clock. 18, a CPU 19, and a memory 20.
[0032]
Here, when the tuner 11 receives a broadcast wave received by the antenna 12 as a received broadcast wave, the tuner 11 receives a designated broadcast channel signal (a signal designating a broadcast channel) from the CPU 19. Then, the broadcast channel signal designated by the designated broadcast channel signal is selected from the received broadcast wave, and is sent to the OFDM demodulator 13 as a selected broadcast signal.
Further, the tuner 11 detects the reception intensity of the channel selection broadcast signal, and sends a voltage corresponding to the detected reception intensity to the A / D converter 17 as a reception intensity detection signal.
[0033]
An OFDM demodulator 13 (orthogonal frequency division multiplex demodulator, hereinafter referred to as demodulator 13 for short) has a TMCC decoding unit 131, a TS demodulation decoding unit 132, and other processing units not shown.
A TMCC (Transmission Multiplexing Configuration Control) decoding unit 131 receives a channel selection broadcast signal from the tuner 11, decodes TMCC information from the channel selection broadcast signal, and supplies the TMCC information to the TS demodulation decoding unit 132.
[0034]
The TMCC signal is a transmission multiplex control signal and includes information related to hierarchical transmission, transmission parameter information (modulation scheme, coding rate, etc.) of each layer, information related to an OFDM segment, and the like.
The TMCC information of the TMCC decoding unit 131 is also read from the CPU 19 via the control bus 21.
[0035]
A TS (Transport Stream) demodulation / decoding unit 132 receives a channel selection broadcast signal from the tuner 11 and TMCC information from the TMCC decoding unit 131.
Then, the TS demodulation / decoding unit 132 switches the demodulation method based on the modulation method information included in the TMCC information, and decodes the TS signal (transmission stream signal) from the channel selection broadcast signal.
[0036]
As another processing unit, for example, an out-of-synchronization detection unit can be provided.
An out-of-synchronization detection unit (not shown) detects whether or not the channel selection broadcast signal is synchronized. If the synchronization signal is not synchronized, the out-of-synchronization signal is sent to the CPU 19.
By providing this out-of-synchronization detection unit in the portable digital broadcast receiver 10, it is possible to suppress wasteful power consumption as in the case where the reception level of the channel selection broadcast signal is lower than the reference level.
[0037]
That is, in the portable digital broadcast receiver 10, since the normal output (video / audio output) cannot be obtained even when the channel selection broadcast signal is out of synchronization, the CPU 19 detects the out of synchronization signal from the out of synchronization detection unit. By stopping the supply of the clock to the circuits after the decoder means, it is possible to suppress wasteful power consumption as in the case where the reception level of the channel selection broadcast signal is lower than the reference level.
[0038]
The MPEG decoder 14 receives a TS signal from the TS demodulation / decoding unit 132 and reproduces an audio signal and video data (audio output and video output) from the TS signal.
Then, the MPEG decoder 14 sends the reproduced audio data to a speaker (not shown) or the like and externally outputs it, and sends the video data to the VRAM 15 to execute writing.
[0039]
A digital signal processing LSI is used for the TS demodulation / decoding unit 132 and the MPEG decoder 14 of the demodulator 13.
For this reason, when the clock signal from the clock 18 stops, the TS demodulation / decoding unit 132 and the MPEG decoder 14 stop the operation while maintaining the internal state represented by the value of the internal register and the setting of the input / output terminal. It can be constituted as follows.
[0040]
However, it is desirable that the digital signal processing LSI mounted on the portable digital broadcast receiver 10 is composed of a CMOS circuit with low power consumption. Since the power consumption of the CMOS circuit increases and decreases depending on the operating frequency, the power consumption is reduced when the clock signal from the clock 18 is stopped.
In the present invention, the TS demodulation / decoding unit 132 and the MPEG decoder 14 are collectively referred to as decoder means A.
[0041]
Video data from the MPEG decoder 14 is written into the VRAM 15 under the control of the CPU 19.
The display unit 16 includes a display device using an LCD (Liquid Crystal Display), EL (Electroluminescence), or the like, and displays the video data extracted from the VRAM 15 as a video.
[0042]
The A / D converter 17 A / D converts the received intensity detection signal and sends it to the CPU 19 via the control bus 21.
The clock (clock means) 18 outputs a clock signal (output signal) that serves as a timing reference for each digital processing. The output signal from the clock 18 is sent to the TMCC decoding unit 131, the TS demodulation decoding unit 132, the MPEG decoder 14 and the like of the demodulator 13.
[0043]
In particular, the clock signal sent to the TS demodulation / decoding unit 132 and the MPEG decoder 14 is controlled by the ON / OFF operation of the switch 22 based on the control of the CPU 19.
When the output from the clock 18 stops, the TS demodulation / decoding unit 132 and the MPEG decoder 14 of the demodulator 13 stop operating while maintaining the internal state such as the value of the internal register and the input / output terminal setting.
[0044]
The CPU 19 performs reception intensity monitoring processing.
The reception intensity monitoring process is a process in which the CPU 19 periodically monitors the reception intensity of the broadcast wave input by the tuner 11 and stops / restarts the operation of the circuits subsequent to the decoder means A based on the monitoring result. .
The operation procedure of the reception intensity monitoring process will be described later.
[0045]
Further, the CPU 19 executes transmission of the designated broadcast channel signal to the tuner 11 and reading of transmission parameters included in the TMCC information from the TMCC decoding unit 131.
Further, the CPU 19 controls ON / OFF of the switch 22 and sends the video data from the MPEG decoder 14 to the VRAM 15 for storage (writing).
In the present invention, the CPU 19 and the A / D converter 17 are referred to as control means B.
[0046]
The memory 20 (storage means) stores (holds) a reference level used in the reception intensity monitoring process.
The reference level is a threshold value set for each combination (transmission parameter) of a modulation method and a coding rate, and reception of a broadcast wave that is at least necessary for obtaining a normal output in a circuit after the decoder means A. A value indicating the level (normal operation lower limit value).
[0047]
The modulation method refers to a method of converting a signal wave (broadcast wave in the present invention) to be transmitted on the transmission side into a change in any one of the phase, amplitude, and frequency of the carrier wave by the voltage in wireless communication.
This modulation method is used in digital broadcasting, and usually differs depending on the broadcast channel and program content.
[0048]
The coding rate is a value obtained by dividing the length of the information block by the length of the code block. For example, when the coding rate is “1”, it indicates that the length of the information block is equal to the length of the code block. In this case, even if a 1-bit error occurs during transmission, other information is represented.
[0049]
In order to improve the reliability, it is necessary to add redundant bits to lower the coding rate, but under the same decoding error rate, the coding rate is high, and theoretical processing and circuit A code that is easy to implement is an excellent code.
A specific example in which the reference level is set for each combination (transmission parameter) of the modulation scheme and coding rate will be described later.
[0050]
The control bus 21 connects the tuner 11, demodulator 13, MPEG decoder 14, A / D converter 17, and CPU 19.
The control bus 21 is a serial or parallel bi-directional bus for identifying a device using a different address for each device and transmitting / receiving data.
The control bus 21 sends a designated broadcast channel signal from the CPU 19 to the tuner 11.
[0051]
The switch 19 is controlled on / off by the CPU 19.
As the switch 22 is turned on / off by the CPU 19, the supply of the clock signal to the TS demodulation / decoding unit 132 and the MPEG decoder 14 is controlled.
For this reason, in the reception intensity monitoring process of the CPU 19, when it is determined that the reception level of the channel selection broadcast signal is below the reference level, the supply of the clock signal is stopped. Operation stops. Therefore, the portable digital broadcast receiver 10 can suppress wasteful power consumption when a normal output cannot be obtained.
[0052]
Next, operations from the reception of broadcast waves to the output of video / audio in the portable digital broadcast receiver of this embodiment will be described with reference to FIG.
A broadcast wave received by the antenna 12 is sent to the tuner 11 as a received broadcast wave. Based on the input of the received broadcast wave, the tuner 11 receives a designated broadcast channel signal from the CPU 19.
[0053]
In this tuner 11, the signal of the broadcast channel designated by the designated broadcast channel signal is selected from the received broadcast wave and sent to the demodulator 13 as a selected broadcast signal.
Further, the tuner 11 detects the reception intensity of the selected broadcast signal, and a voltage corresponding to the detected reception intensity is sent to the A / D converter 17 as a reception intensity detection signal.
[0054]
In the TMCC decoding unit 131 of the demodulator 13, the channel selection broadcast signal from the tuner 11 is input. Further, TMCC information is decoded from the inputted channel selection broadcast signal and supplied to the TS demodulation / decoding unit 132.
The TS demodulation / decoding unit 132 receives a channel selection broadcast signal from the tuner 11. Then, the demodulation method is switched based on the modulation method information included in the TMCC information from the TMCC decoding unit 131, and the TS signal is decoded from the channel selection broadcast signal.
Note that the TMCC information of the TS demodulation / decoding unit 132 can be read by the CPU 19 via the control bus 21.
[0055]
The TS signal decoded by the TS demodulation / decoding unit 132 is sent to the MPEG decoder 14.
In the MPEG decoder 14, an audio signal and video data are reproduced from the TS signal. Of these, the video data is written into the VRAM 15 and displayed on the display unit 16 as video.
[0056]
Next, the reception intensity monitoring process in the CPU will be described with reference to FIG. This figure is a flowchart showing the operation procedure of the reception intensity monitoring process executed by the control means B.
The memory 20 stores a reference level used in the reception intensity monitoring process. This reference level is a value of reception intensity required for obtaining a normal output in a circuit after the MPEG decoder 14 for a combination (transmission parameter) of a plurality of modulation schemes and coding rates used in digital broadcasting. (Reception level value) is set.
[0057]
In the CPU 19, when TMCC information is sent from the TMCC decoding unit 131 of the demodulator 13 via the control bus 21, from this TMCC information, the modulation scheme and coding rate used in the currently selected broadcast channel are determined. Read (step 10).
A reference level corresponding to the combination (transmission parameter) of the read modulation scheme and coding rate is retrieved from the memory 20 (step 11).
[0058]
Also, the received intensity detection signal (received level of the selected broadcast signal) from the tuner 11 is A / D converted by the A / D converter 17 and sent to the CPU 19 via the control bus 21 and input (step 12). , Step 13).
Then, the CPU 19 determines whether or not the reception level value indicated by the reception intensity detection signal is larger than the reference level value extracted from the memory 20 (step 14).
[0059]
As a result of the determination, if the value of the reception level is smaller than the value of the reference level, the switch 22 is turned off (step 15).
As a result, the supply of the clock signal to the TS demodulation / decoding unit 132 and the MPEG decoder 14 of the demodulator 13 is stopped. For this reason, wasteful power consumption in the circuits after the decoder means A when the reception level is low and sufficient output cannot be obtained can be suppressed.
[0060]
On the other hand, when the value of the reception level is larger than the value of the reference level, the switch 22 is turned on (step 16).
As a result, the supply of the clock signal to the TS demodulation / decoding unit 132 and the MPEG decoder 14 of the demodulator 13 is continued (or resumed when the switch 22 is turned off).
[0061]
A series of these received intensity monitoring processes are executed every certain time, for example, every 0.5 seconds during the broadcast reception.
Note that the power consumption of the CMOS circuit used in the decoder means A increases and decreases based on the operating frequency, so that the power consumption decreases when the supply of the clock signal is stopped.
[0062]
Also, unlike the reception strength monitoring process, if the broadcast at the necessary level is not performed when TMCC information is read, the reception level value is smaller than the reference level value. The power consumption of the decoder means A can be reduced by turning off the switch 22 and stopping the supply of the clock signal to the TS demodulator / decoder 132 and the MPEG decoder 14 of the demodulator 13.
Further, when the broadcast at the required level is not performed, or when the value of the reception level is smaller than the value of the reference level, the content indicating that the broadcast is not performed or the reception level is low from the CPU 19 separately. Display data may be written in the VRAM 15 and displayed on the display unit 16.
[0063]
Next, combinations of modulation schemes and coding rates (transmission parameters) and reference levels set for the respective transmission parameters will be described.
In terrestrial digital broadcasting, a hierarchical transmission system is used, and broadcasting services are provided at different levels for each of the fixed reception, mobile, and mobile reception modes. A plurality of transmission parameters that can be used are defined for each layer.
[0064]
The transmission parameter includes a modulation scheme and a coding rate.
There are four types of modulation methods in digital terrestrial broadcasting, for example, DQPSK, QPSK, 16QAM, and 64QAM.
Of these, DQPSK and QPSK are related to phase modulation, and 16QAM and 64QAM are related to multilevel quadrature amplitude modulation.
[0065]
Further, five coding rates of 1/2, 2/3, 3/4, 5/6, and 7/8 are defined as coding rates of convolutional codes.
These have different transmission capacities and required C / N values (ratio of carrier power (C) and noise power (N)) that can be decoded error-free.
[0066]
The transmission capacity increases in the order of DQPSK <QPSK <16QAM <64QAM in the modulation scheme, and (1/2) <(2/3) <(3/4) <(5/6) in the coding rate. ) <(7/8) in this order.
Similarly, the required C / N value that can be decoded without error increases in this order. However, when the required C / N value is large, a large reception level is required in consideration of a specific device and a reception environment.
[0067]
FIG. 3 shows an example of reference levels set for the combinations (transmission parameters) of these modulation schemes and coding rates.
As shown in the figure, there are 20 combinations of modulation schemes and coding rates, and a reference level is set for each combination.
[0068]
However, the 20 combinations shown in the figure are theoretically possible combinations.
Therefore, when actually using the portable digital broadcast receiver of the present invention, it is not necessary to set a reference level for all of the combinations shown in the figure. For example, the portable digital broadcast receiver Thus, it is possible to set a reference level only for a combination of a modulation method and a coding rate for a broadcast wave that can be actually received.
[0069]
The possibility that such a reference level setting (that is, setting a reference level only for a part of the combinations shown in the figure) is executed in each company or broadcasting station up to now. This is supported by experimental results and publications.
For example, stable broadcasting service in portable reception is possible up to three types of modulation schemes, DQPSK, QPSK, and 16QAM, and the coding rate of the convolutional code is 1/2, 2 / It has been clarified in the experimental results and the like that it is up to about 3/3/4.
[0070]
Therefore, when the portable digital broadcast receiver of the present invention is used in an actual broadcast service, the reference level setting range is a combination range of a modulation scheme and a coding rate used in the broadcast service.
Each type of modulation scheme and coding rate is a type used in terrestrial digital broadcasting. For this reason, when the portable digital broadcast receiver of the present invention is used for other digital broadcasts, the types of modulation schemes and coding rates, combinations of these types, and the reference levels set for each combination are shown in FIG. It is different from what is shown in.
[0071]
[Second Embodiment]
Next, a second embodiment of the portable digital broadcast receiver of the present invention will be described with reference to FIG.
FIG. 2 is a block diagram showing the internal configuration of the portable digital broadcast receiver of this embodiment.
[0072]
This embodiment is different from the first embodiment in that a D / A converter and a voltage comparator are newly provided in the control means instead of the A / D converter. That is, in the first embodiment, the comparison between the reception level and the reference level is performed by the CPU, whereas in the present embodiment, the comparison is performed using a D / A converter and a voltage comparator. Other components are the same as those in the first embodiment.
Therefore, in FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0073]
As shown in FIG. 4, the portable digital broadcast receiver 10 has a D / A converter 23 and a voltage comparator 24 in the control means B.
Here, the D / A converter 23 inputs and sets a reference level from the CPU 19 via the control bus 21.
[0074]
The voltage comparator 24 (voltage comparison unit) receives the reception intensity detection signal from the tuner 11 and the reference level from the D / A converter 23.
Then, the voltage comparator 24 determines whether or not the value of the reception level indicated by the reception intensity detection signal is larger than the value of the reference level that is the output of the D / A converter 23, and based on the result of this determination, Controls ON / OFF of the switch 22.
[0075]
For example, when the reception level value is smaller than the reference level value, the voltage comparator 24 turns off the switch 22. As a result, the supply of the clock signal to the TS demodulation / decoding unit 132 and the MPEG decoder 14 of the demodulator 13 is stopped.
On the other hand, when the value of the reception level is larger than the value of the reference level, the switch 22 is turned on. Thereby, the supply of the clock signal to the TS demodulation / decoding unit 132 and the MPEG decoder 14 of the demodulator 13 is continued (resumed).
In this embodiment, the CPU 19 updates the value of the reference level set by the D / A converter 23 according to a change in the modulation method or the like.
[0076]
Next, the operation of the reception intensity monitoring process in the portable digital broadcast receiver of this embodiment will be described with reference to FIG.
This figure is a flowchart showing the operation procedure of the reception intensity monitoring process executed by the control means B.
[0077]
In the CPU 19, TMCC information is received from the TMCC decoding unit 131 of the demodulator 13 via the control bus 21, and the modulation scheme and coding rate are read from the received TMCC information (step 20) and further stored in the memory 20. Among the plurality of reference level values, a reference level corresponding to the read combination of the modulation scheme and coding rate is extracted (step 21).
[0078]
The extracted reference level is sent from the CPU 19 to the D / A converter 23 via the control bus 21 and set to D / A (step 22).
In the voltage comparator 24, the reference level from the D / A converter 23 is input, and further, a reception intensity detection signal is input from the tuner 11 (step 23). In the voltage comparator 24, it is determined whether or not the value of the reception level indicated by the reception intensity detection signal is larger than the value of the reference level (step 24).
[0079]
If it is determined that the reception level value is smaller than the reference level value, the switch 22 is turned off (step 25).
As a result, the supply of the clock signal to the TS demodulation / decoding unit 132 and the MPEG decoder 14 of the demodulator 13 is stopped. For this reason, wasteful power consumption in the circuits after the decoder means A when the reception level is low and sufficient output cannot be obtained can be suppressed.
[0080]
On the other hand, when the value of the reception level is larger than the value of the reference level, the switch 22 is turned on (step 26).
As a result, the supply of the clock signal to the TS demodulation / decoding unit 132 and the MPEG decoder 14 of the demodulator 13 is continued (or resumed when the switch 22 is turned off).
[0081]
Of the series of reception intensity monitoring processes, the processes from step 23 to step 26 are separately performed in parallel by hardware, and therefore the CPU 19 actually performs the transmission parameter monitoring process (ie, step 20 to step 22). Only processing up to). This transmission parameter monitoring process is executed every certain period, for example, every 0.5 seconds, during broadcast reception, as in the reception intensity monitoring process in the first embodiment.
When the portable digital broadcast receiver has such a configuration, the supply and stop of the clock signal due to the fluctuation of the reception intensity is directly executed only by hardware without using software processing, and therefore compared with the first embodiment. High-speed processing is possible.
[0082]
[Third embodiment]
Next, a third embodiment of the portable digital broadcast receiver of the present invention will be described with reference to FIG.
FIG. 2 is a block diagram showing the internal configuration of the portable digital broadcast receiver of this embodiment.
[0083]
This embodiment is different from the second embodiment in that an interrupt signal is sent from the TMCC decoding unit to the CPU. That is, in the second embodiment, the CPU inputs TMCC information from the demodulator at regular intervals and recognizes the modulation scheme and coding rate indicated by the input TMCC information. In the present embodiment, The CPU is different in that it recognizes the modulation method and coding rate changed during broadcast reception based on the interrupt signal after recognizing the modulation method and coding rate indicated by the TMCC information. Other components are the same as in the second embodiment.
Therefore, in FIG. 6, the same components as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0084]
As shown in FIG. 6, the portable digital broadcast receiver 10 has a connection line connecting the TMCC decoding unit 131 and the CPU 19, and sends an interrupt signal from the TMCC decoding unit 131 to the CPU 19 through this connection line.
This interrupt signal indicates that the modulation method or coding rate has been changed due to a change in broadcast channel or program content.
[0085]
Next, an operation procedure in the portable digital broadcast receiver of this embodiment will be described with reference to FIG.
The broadcast wave received by the antenna 12 is selected by the tuner 11, and this selected broadcast signal is demodulated by the demodulator 13. Then, the MPEG decoder 14 extracts and outputs audio data and video data from the TS signal based on the demodulation.
[0086]
Further, the CPU 19 receives TMCC information from the demodulator 13 and confirms the combination (transmission parameter) of the modulation scheme and coding rate indicated by the TMCC information. Then, the reference level corresponding to this transmission parameter is retrieved from the memory 20 and sent to the D / A converter 23 for D / A setting.
In the voltage comparator 24, the reference level is received from the D / A converter 23, and the received intensity detection signal is received from the tuner 11. Then, it is determined whether or not the reception level value indicated by the reception intensity detection signal is larger than the reference level value.
[0087]
As a result of the determination, when the reception level value is smaller than the reference level value, the switch 22 is turned off under the control of the voltage comparator 24. As a result, the supply of the clock signal to the decoder means A is stopped.
On the other hand, when the value of the reception level is larger than the value of the reference level, the switch 22 is turned on by the control of the voltage comparator 24 (or the ON state of the switch 22 is continued).
[0088]
By the way, when the signal of the broadcast channel selected by the tuner 11 is changed to the signal of another broadcast channel, or when the program in the selected broadcast channel is transferred to another program, etc. Transmission parameters such as modulation scheme or coding rate may be switched.
When the TMCC decoding unit 131 confirms that the modulation scheme or coding rate indicated by the channel selection broadcast signal has been switched, an interrupt signal indicating that the switching has been performed is sent from the TMCC decoding unit 131 to the CPU 19.
[0089]
When the CPU 19 confirms that the modulation scheme or coding rate has been switched based on the received interrupt signal, TMCC information is newly sent from the TMCC decoding unit 131 to the CPU 19.
Then, the CPU 19 reads from the new TMCC information the modulation scheme and coding rate used in the currently selected broadcast channel (new broadcast channel).
[0090]
A reference level corresponding to the combination (transmission parameter) of the read modulation method and coding rate is taken out from the memory 20, sent from the CPU 19 to the D / A converter 23 via the control bus 21, A is set.
Further, the voltage comparator 24 determines whether or not the value of the reception level indicated by the reception intensity detection signal from the tuner 11 is larger than the value of the reference level from the D / A converter 23, and based on the result of this determination. Thus, the switching control of the switch 22 is executed.
[0091]
According to such a configuration, when the modulation system or the coding rate of the channel selection broadcast signal is switched, an interrupt signal indicating the switching is sent from the TMCC decoding unit 131 to the CPU 19. This eliminates the need to monitor the modulation method and the like.
Therefore, it is possible to increase the speed and efficiency of the control process (particularly the reception intensity monitoring process) in the CPU 19.
[0092]
In this embodiment, the reception intensity monitoring process is executed using the D / A converter 23 and the voltage comparator 24. However, the present invention is not limited to the case where the D / A converter 23 and the voltage comparator 24 are used. For example, the reception intensity monitoring process can be executed in the CPU 19 as in the first embodiment.
Moreover, the portable digital broadcast receiver of the present invention may be an arbitrary combination of the portable digital broadcast receivers in the first embodiment, the second embodiment, and the third embodiment.
[0093]
【The invention's effect】
As described above, according to the present invention, the reception level of the received broadcast wave is set to the necessary minimum reception level (reference level) set for each transmission parameter that is a combination of a modulation scheme and a coding rate. As a result of the comparison, when the reception level is lower than the reference level, the supply of the clock to the circuits subsequent to the decoder means is stopped. When video output cannot be obtained, wasteful power consumption in the internal circuit can be suppressed.
[0094]
In addition, since the operation control of the circuits after the decoder means is executed not by turning on / off the power supply but by continuing / stopping the supply of the clock signal, the internal state of the digital signal processing LSI constituting the decoder means is maintained, The operation of the decoder means can be stopped.
Therefore, since the reception level of the broadcast wave is recovered and setting processing is not required when the operation of the circuit after the decoder means is resumed, the recovery time of the audio / video output can be reduced with a simple configuration. Can be shortened.
[0095]
Furthermore, since the reference level is set for each transmission parameter and an interrupt signal indicating that the transmission parameter of the channel selection broadcast signal has been switched is notified to the control means, the control means of the portable digital broadcast receiver Using the reference level corresponding to the new transmission parameter based on the switching, the comparison processing with the reception level of the channel selection broadcast signal can be executed to control the supply of the clock signal to the decoder means.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an internal configuration of a portable digital broadcast receiver according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing the operation of the portable digital broadcast receiver in the first embodiment of the present invention.
FIG. 3 is a chart showing reference levels set for each combination of modulation scheme and coding rate.
FIG. 4 is a block diagram showing an internal configuration of a portable digital broadcast receiver according to the second embodiment of the present invention.
FIG. 5 is a flowchart showing the operation of the portable digital broadcast receiver in the second embodiment of the present invention.
FIG. 6 is a block diagram showing an internal configuration of a portable digital broadcast receiver according to a third embodiment of the present invention.
[Explanation of symbols]
10 Mobile digital broadcast receiver
11 Tuner
12 Antenna
13 OFDM demodulator (demodulator)
131 TMCC decoder
132 TS demodulation and decoding unit
14 MPEG decoder
15 VRAM
16 Display section
17 A / D converter
18 clocks
19 CPU
20 memory
21 Control bus
22 switch
23 D / A Converter
24 Voltage comparator
A Decoder means
B Control means

Claims (2)

A tuner that tunes the selected broadcast signal from the broadcast wave,
Decoder means for decoding the channel selection broadcast signal from the tuner and reproducing video data and audio data;
Clock means for supplying a clock signal to the decoder means;
A portable digital broadcast receiver having control means for controlling the supply of the clock signal,
The tuner detects the reception level of the broadcast wave,
The control means stops the supply of the clock to the decoder means when the value of the reception level from the tuner is smaller than the value of the reference level ,
The decoder means includes a TMCC decoding unit for detecting a modulation scheme and a coding rate from the broadcast wave;
This TMCC decoding unit sends an interrupt signal indicating that the modulation method and / or coding rate of the broadcast wave has been switched to the control means,
The control means takes out a reference level corresponding to the combination of the modulation method and coding rate after switching indicated by the interrupt signal from the storage means, and the value of the reception level is larger than the taken value of the reference level. A portable digital broadcast receiver characterized in that when it is small, the supply of the clock to the decoder means is stopped . After the supply of the clock to the decoder means is stopped, when the value of the reception level becomes larger than the value of the reference level, the control means resumes the supply of the clock to the decoder means. Do
The portable digital broadcast receiver according to claim 1.

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