JP2005109912A - Digital broadcasting receiver - Google Patents

Abstract

To reduce power consumption of a television receiver.
When an error rate S in an error correction unit 103 is detected by an error detection unit 121 and the error rate S is equal to or less than a reference value Sth that can be regarded as a good reception state, power limitation is performed. The circuit 123 reduces power supplied to the high-frequency unit 101 and reduces power consumption. At this time, even if the reception sensitivity is reduced by reducing the power supplied to the high-frequency unit 101, a good reception state can be maintained while the error rate S is below the reference value Sth. On the other hand, when the error rate S exceeds the reference value Sth, it is determined that the reception state is bad, the reduction of the power supplied to the high frequency unit 101 by the power limiting circuit 123 is canceled, and the reception sensitivity of the high frequency unit 101 is reduced. Improve and ensure good reception.
[Selection] Figure 2

Description

  The present invention relates to a digital broadcast receiver, and more particularly to a digital broadcast receiver designed to reduce power consumption.

2. Description of the Related Art Conventionally, in mobile reception type receivers, power consumption is reduced. In particular, a battery is often used as a power source, and power consumption is directly related to battery life, so reduction of power consumption is an important issue.
As a method for reducing power consumption, for example, in a system in which communication is performed using an OFDM system (orthogonal frequency division multiplexing signal), a receiving apparatus does not receive all subcarriers but requires a plurality of necessary subcarriers. There has been proposed a technique in which only the carrier is selectively received to lower the sampling frequency of the A / D converter to reduce power consumption (for example, Patent Document 1).
JP-A-8-331093

However, as described in Patent Document 1 described above, when only the necessary subcarriers are selectively received, it is necessary to switch the filter in accordance with the required subcarriers, which complicates the circuit. This hinders downsizing of the apparatus and increases the cost. Further, when all subcarriers are required, it is not possible to reduce power consumption.
Therefore, the present invention has been made paying attention to the above-mentioned conventional unsolved problems, and is intended to apply a digital broadcast receiver capable of reducing power consumption without increasing the number of devices. It is aimed.

  To achieve the above object, a digital broadcast receiver according to a first aspect of the present invention includes a high-frequency unit that receives a digital broadcast signal and amplifies a broadcast signal corresponding to a designated station, and a broadcast signal processed by the high-frequency unit. In the digital broadcast receiver comprising: an error correction unit that performs error correction processing on the signal; and a reproduction processing unit that performs reproduction processing based on the broadcast signal that has been subjected to error correction processing by the error correction unit. An error rate detecting means for detecting an error rate in the above, and a supply power reducing means for reducing the supply power to the high-frequency unit when the error rate detected by the error rate detecting means exceeds a preset reference value, It is characterized by providing.

In the first invention, the digital broadcast signal is input to the high frequency unit, the broadcast signal corresponding to the station designated here is amplified, and after the error correction processing is performed in the error correction unit, the reproduction processing unit Playback processing is performed.
At this time, the error rate detection means detects the error rate in the error correction unit, and when the error rate is equal to or less than a preset reference value, the power supplied to the high frequency unit is reduced. Do. Therefore, when the error rate is less than or equal to the reference value and it is predicted that the reception state is good, power consumption can be reduced by reducing the power supplied to the high-frequency unit.

When the error rate exceeds the reference value and the reception state is predicted to be poor, the reduction of the power supplied to the high frequency unit is canceled, so that the specified power is supplied to the high frequency unit to improve reception sensitivity. Thus, the reception state can be recovered.
According to a second aspect of the present invention, the supply power reduction means increases the supply power reduction amount as the deviation between the error rate detected by the error rate detection means and the reference value increases. It is characterized by that.

In the second aspect of the invention, the supply power reduction means detects a deviation between the error rate detected by the error rate detection means and the reference value, and the deviation is larger, that is, the error rate is more marginal. Since the amount is increased, the supplied power can be efficiently reduced and the power consumption can be effectively reduced.
According to a third aspect of the present invention, the supply power reduction means includes comparison means for comparing the error rate detected by the error rate detection means with the reference value, and based on the comparison result of the comparison means, the error When the state where the rate is less than or equal to the reference value continues for the first duration or longer, the reduction of the supplied power is started, and the state where the error rate exceeds the reference value is shorter than the first duration. It is characterized in that the reduction of the supplied power is canceled when the duration of 2 or more is continued.

  In the third aspect of the invention, the supply power reduction means compares the error rate detected by the error rate detection means with the reference value by the comparison means, and the error rate is below the reference value based on the comparison result. However, when the duration continues for the first duration or longer, it is determined that the reception state is good and the reduction of the supplied power is started, and the state where the error rate exceeds the reference value continues for the second duration or longer. In addition, it is determined that the reception state is defective, and the reduction of the supplied power is cancelled.

  At this time, since the second duration is set to be shorter than the first duration, the state in which the error rate is equal to or lower than the reference value continues for the first duration or more, and the error rate is the reference on average. By reducing the supply power only when it can be regarded as being less than or equal to the value, it is possible to avoid reducing the supply power in a state where the reception state is not stable. When the error rate exceeds the reference value, it is possible to avoid missing the broadcast signal by promptly canceling the reduction of the supplied power.

  According to a fourth aspect of the present invention, there is provided a digital broadcast receiver which receives a digital broadcast signal and amplifies a broadcast signal corresponding to a designated station, and an error correction process for the broadcast signal processed by the high frequency unit. An error rate in the error correction process is detected in a digital broadcast receiver comprising an error correction unit that performs an error correction and a reproduction processing unit that performs a reproduction process based on a broadcast signal that has been subjected to an error correction process by the error correction unit It is characterized by comprising an error rate detecting means and an attenuating means for attenuating the input signal level to the high frequency section when the error rate detected by the error rate detecting means is not more than a preset reference value.

In the fourth aspect of the invention, the digital broadcast signal is input to the high frequency unit, where the broadcast signal corresponding to the designated station is amplified, and the error correction process is performed on the broadcast signal by the error correction unit. Thereafter, reproduction processing is performed in the reproduction processing unit.
At this time, the error rate detection means detects the error rate in the error correction unit, and when the error rate is equal to or less than a preset reference value, the input signal level to the high frequency unit is attenuated. As a result, when the reception sensitivity is lowered, a state equivalent to that when the reception sensitivity is lowered is conversely. When the error rate exceeds the reference value and the reception state is predicted to be bad, the input signal to the high-frequency unit is The level attenuation is canceled, and as a result, the reception sensitivity is improved to a state equivalent to that.

In this way, it is possible to ensure a good reception state by canceling the attenuation of the input signal level against the deterioration of the error rate.
Therefore, the reception sensitivity can be adjusted without controlling the power supplied to the high-frequency unit, so that it is possible to obtain a good strong input characteristic with the input signal level attenuated for the power supplied to the high-frequency unit. Even if the value is reduced to a possible level, a good reception state can be maintained. Therefore, good strong input characteristics can be obtained, and power supply can be reduced.

Further, the fifth invention is characterized in that the attenuation means increases the attenuation as the deviation between the error rate detected by the error rate detection means and the reference value increases. .
In the fifth aspect of the invention, the attenuation means detects the deviation between the error rate detected by the error rate detection means and the reference value, and increases the attenuation as the deviation is larger. In other words, since the attenuation is increased as the error rate has a margin, good strong input characteristics can be maintained.

  According to a sixth aspect of the present invention, the attenuation means includes a comparison means for comparing the error rate detected by the error rate detection means with the reference value, and the error rate is calculated based on a comparison result of the comparison means. Attenuation of the input signal level is started when the state equal to or less than the reference value continues for a first duration or longer, and a state where the error rate exceeds the reference value is shorter than the first duration. In this case, the attenuation of the input signal level is canceled when the signal continues for more than a predetermined time.

  In the sixth aspect of the invention, the attenuation means compares the error rate detected by the error rate detection means with the reference value by the comparison means, and based on the comparison result, the error rate is lower than the reference value. When it continues for more than 1 duration, it determines that the reception state is good and starts attenuation of the input signal level, and when the error rate exceeds the reference value for more than the second duration, It is determined that the reception state is defective, and the attenuation of the input signal level is cancelled.

  At this time, since the second duration is set to be shorter than the first duration, the state in which the error rate is equal to or lower than the reference value continues for the first duration or more, and the error rate is the reference on average. By starting the attenuation of the input signal level only when it can be considered to be less than or equal to the value, it is possible to avoid starting the attenuation of the input signal level when the reception state is not stable. On the contrary, when the error rate exceeds the reference value, it is possible to avoid missing the broadcast signal by quickly canceling the attenuation of the input signal level.

In the seventh invention, the error correction unit performs Reed-Solomon decoding on the broadcast signal as the error correction processing, and the error rate detection means detects an error rate after the Reed-Solomon decoding, The error rate reference value is set based on 1 × 10 ⁻¹¹ .
In the seventh invention, the error correction unit performs Reed-Solomon decoding as error correction processing, and the error rate detection means detects the error rate after Reed-Solomon decoding.

Here, when the error rate after Reed-Solomon decoding is 1 × 10 ⁻¹¹ or less, it is known that there is substantially no error, so-called pseudo error free. The reference value is set based on the error rate after Reed-Solomon decoding and the judgment is made based on the error rate after Reed-Solomon decoding, thereby reducing supply power or starting attenuation of the input signal level. Alternatively, it is possible to accurately determine the cancellation.

In an eighth aspect of the invention, the error correction unit performs Viterbi decoding and Reed-Solomon decoding on the broadcast signal in this order as the error correction processing, and the error rate detection means calculates the error rate after Viterbi decoding. And the reference value of the error rate is set based on 2 × 10 ⁻⁴ .
In the eighth invention, the error correction unit performs Viterbi decoding and then Reed-Solomon decoding as error correction processing, and the error rate detection means detects the error rate after Viterbi decoding.

Here, it is known that when the error rate after Reed-Solomon decoding is 1 × 10 ⁻¹¹ or less, there is substantially no error, so-called pseudo error free, and errors after Viterbi decoding If the rate is 2 × 10 ⁻⁴ or less, it is known that the error rate after Reed-Solomon decoding is 1 × 10 ⁻¹¹ or less. By setting a reference value based on the error rate and making a determination based on the error rate after Viterbi decoding, it is possible to accurately determine whether to reduce the supply power or start or cancel the attenuation of the input signal level.

Embodiments of the present invention will be described below.
First, a first embodiment will be described.
FIG. 1 is an external view showing an example of a portable television receiver for receiving digital terrestrial broadcasting to which the present invention is applied, in which (a) is a plan view, (b) is a left side view, and (c) ) Is a right side view.
In FIG. 1, a television receiver 1 includes a vertically long receiving device main body 2 and a rod antenna 3.
When the rod antenna 3 is carried, the rod antenna 3 is housed in the left side surface portion 21 of the apparatus main body 2, and by rotating the rod antenna 3 180 degrees at the base end portion, as shown by a dotted line in FIG. It can be pulled out from the apparatus main body 2 upward.

The display unit 41 of the liquid crystal device 4 is disposed on the upper surface portion 22 of the apparatus main body 2 so that the received television image can be viewed. A channel selection channel button 12 or the like is disposed below the display unit 41, and a speaker 13 is disposed below the channel button 12.
Further, a brightness adjustment switch 14, an AV input unit 15, a power switch 16, and a backlight lighting switch 17 for the liquid crystal device 4 are disposed on the right side surface portion 23 of the apparatus main body 2.

FIG. 2 is a configuration diagram illustrating a schematic configuration of the television receiver 1.
The received broadcast signal received by the rod antenna 3 is input to the high frequency unit 101, and the high frequency unit 101 selects a signal corresponding to a desired channel. The selected broadcast signal is converted into a digital signal of “0” or “1” by the OFDM demodulator 102.

The digital signal converted by the OFDM demodulator 102 is subjected to error correction processing by a known procedure in the error correction unit 103, and then restored to a TS packet transmitted from a broadcasting station. In the error correction process, for example, if a TS packet from a broadcasting station is transmitted after being subjected to Reed-Solomon encoding and convolutional encoding, Viterbi decoding and RS (Reed-Solomon) decoding are performed, and the TS packet is converted. Restore.
The TS packet is input to the MPEG demodulator 104, where it is decoded into a video signal and an audio signal, and output to the speaker 13 and the liquid crystal device 4 to reproduce the audio and image.

Further, the television receiver 1 includes a supply power control unit 120 that controls the supply power from the power supply 110 to the high frequency unit 101 based on the error correction result in the error correction unit 103.
The power supply control unit 120 includes an error rate detection unit 121 that detects an error rate (BER) in the error correction unit 103, an error rate S detected by the error rate detection unit 121, and a preset error rate reference It comprises a comparator 122 that compares the value Sth, and a power limiting circuit 123 that is inserted in the power supply line from the power supply 110 to the high-frequency unit 101.

The comparator 122 indicates whether or not the error rate S detected by the error detector 121 is equal to or less than a reference value Sth of the error rate, and a comparison signal indicating a difference ΔS between the error rate S and the reference value Sth. Output to the power limiting circuit 123.
When the comparison signal from the comparator 122 is a signal indicating that the error rate S is less than or equal to a reference value Sth, the power limiting circuit 123 limits the power supplied from the power source 110 to the high frequency unit 101 by a predetermined amount. . On the other hand, when the error rate S exceeds the reference value Sth, this is canceled if the power supply is limited at this time.

Note that the limitation of the supplied power in the power limiting circuit 123 is determined according to, for example, the difference ΔS between the error rate S and the reference value Sth. For example, when the difference ΔS is large, that is, when the error rate has a relatively large margin, a relatively large first limiting amount is set. When the difference ΔS is small, that is, when the error rate does not have a large margin, the first limit is set. The second limit amount having a value smaller than the limit amount is set.
The first limit amount and the second limit amount are set such that the error rate S after the supply power is limited by these limit amounts does not exceed the reference value Sth. Is done.

Here, the reference value Sth of the error rate is set to a value at which it can be determined that a good reception state can be obtained. Specifically, for example, the error rate reference value Sth is set to 1 × 10 ⁻¹¹ that can be regarded as pseudo error free as an error rate after RS decoding in the error correction unit 103. Set to a value that takes into account.
That is, the error rate S detected by the error rate detection unit 121 is equal to or less than the error rate reference value Sth, the error rate of the received digital broadcast signal is small, and the reception sensitivity of the high frequency unit 101 is reduced. When it can be assumed that a simple image and sound can be reproduced, the power supplied to the high-frequency unit 101 is limited.

On the other hand, it is predicted that the error rate S detected by the error rate detection unit 121 exceeds the error rate reference value Sth, the error rate of the received digital broadcast signal is large, and good images and sound cannot be reproduced. When the power is limited, the power limitation in the power limiting circuit 123 is released, the reception sensitivity of the high-frequency unit 101 is improved, and recovery to a good reception state is achieved.
In the initial state, that is, when the power switch 16 is turned on, the power limiting circuit 123 supplies a specified amount of power to the high-frequency unit 101 without limiting the power.

Next, the operation of the first embodiment will be described.
When the power switch 16 is switched to the on state, power is supplied from the power source 110 to each unit, and each unit is in an operable state.
Then, the broadcast signal transmitted from the broadcast station is input to the high frequency unit 101, and a broadcast signal corresponding to the channel selected here is extracted, and this is converted into a digital broadcast signal by the OFDM demodulator 102. The digital broadcast signal is subjected to error correction processing in the error correction unit 103, Viterbi decoding and RS decoding are performed to restore the TS packet, and then the MPEG demodulation unit 104 decodes the video signal and the audio signal. These signals are output to the speaker 13 and the liquid crystal device 4 to reproduce sound and images.

  If the reception state is good, the error rate S detected by the error correction unit 103 is lower than the reference value Sth. At this time, if the reception state is good and the difference ΔS between the error rate S and the reference value Sth is large, that is, the reception state is quite good from the viewpoint of the error rate S, and there is a sufficient margin in reception sensitivity. When predicted, a relatively large first limiting amount is set as the limiting amount, and the power limiting circuit 123 reduces the power supplied to the high-frequency unit 101 relatively large.

  As a result, the reception sensitivity of the high-frequency unit 101 is relatively lowered. At this time, the error rate S detected by the error correction unit 103 is equal to or less than the reference value Sth, and the first limit amount is set. Even if the sensitivity is reduced by a corresponding amount, the first limit amount is set so that the error rate S does not exceed the reference value Sth, so that the supply to the high-frequency unit 101 is performed. Even if the power is relatively reduced, the error rate S does not exceed the reference value Sth, and reception can be continued satisfactorily.

  On the other hand, when the error rate S is equal to or smaller than the reference value Sth and the difference ΔS is small, a relatively small second limiting amount is set as the limiting amount in the current limiting circuit 123. Accordingly, when the error rate S is less than or equal to the reference value Sth but the difference ΔS is relatively small and the sensitivity cannot be lowered so much, the power supply to the high-frequency unit 101 is reduced by a relatively small second limit amount. By doing so, it is avoided that the sensitivity is excessively lowered and the subsequent error rate S exceeds the reference value Sth.

In this way, in a state where the power supplied to the high frequency unit 101 is limited, when the reception state deteriorates and the error rate S exceeds the reference value Sth, the power supply limiting circuit 123 supplies the high frequency unit 101 to the high frequency unit 101. Remove the power supply restriction.
As a result, when the error rate S exceeds the reference value Sth, the power supplied to the high-frequency unit 101 is restored to the specified amount, which improves the reception sensitivity. As a result, the reception sensitivity of the unit 101 is improved, so that a good reception state can be recovered.

Thus, by reducing the power supply to the high-frequency unit 101 while the error rate S is less than or equal to the reference value Sth, that is, when the reception state can be considered to be good. Accordingly, power consumption can be reduced.
In particular, in the case of digital broadcasting, as shown in FIG. 3, a good received image quality can be obtained while the electric field strength is high to some extent, but when the electric field strength exceeds a certain threshold, the received image quality decreases rapidly. The so-called cliff effect phenomenon occurs. In the case of analog broadcasting, the electric field strength and the received image quality are almost proportional. In FIG. 3, the horizontal axis represents the electric field intensity, and the electric field intensity is weaker toward the right side in FIG. The vertical axis represents the received image quality, and the higher the image is in the upward direction in FIG. 3, the better the received image quality is.

  Therefore, by monitoring the error rate S representing the received image quality and reducing the power supplied to the high-frequency unit 101 until the error rate S exceeds the reference value Sth, the electric field strength near the threshold value in FIG. Thus, the supplied power can be reduced until the minimum electric field strength required for ensuring the received image quality is reached, and the supplied power can be efficiently reduced.

Next, a second embodiment of the present invention will be described.
Since the second embodiment is the same as the first embodiment except that the configuration of the supply power control unit is different, the same parts are denoted by the same reference numerals, and detailed description thereof is omitted. To do.
As shown in FIG. 4, the supply power control unit 120 a in the second embodiment has the power between the comparator 122 and the power limiting circuit 123 based on the comparison result in the comparator 122. A limiting operation control unit 125 for controlling the power limiting operation by the limiting circuit 123 is inserted.

  The limiting operation control unit 125 monitors the comparison result in the comparator 122, and when the comparator 122 continues a relatively long good determination time when the detection value S is equal to or less than the reference value Sth. Assuming that the reception state is good, the power limiting circuit 123 is notified of a start command for the power limiting operation. Further, the state in which the error rate S exceeds the reference value Sth is shorter than the good determination time, and the failure determination time that can quickly detect the deterioration in response to the rapid deterioration of the reception state is continued. Then, it is determined that the reception state is bad, and the power limiting circuit 123 is notified of a command to cancel the power limiting operation.

Therefore, now, the reception state is not very good, and the state in which the error rate S exceeds the reference value Sth continues for the failure determination time or more, the reception state is bad. A predetermined power is supplied to the high-frequency unit 101 to improve the reception sensitivity of the high-frequency unit 101 and to maintain a good reception state.
When the reception state is temporarily recovered from this state and the error rate S becomes equal to or less than the reference value Sth, the limit operation control unit 125 detects this, but there is a state where the error rate S is equal to or less than the reference value Sth. In the state where it does not continue for the good judgment time or longer, the supply power is not limited.

  Here, when the reception state is temporarily recovered, a supply power limiting operation is performed, and when the reception state deteriorates again in a state where the reception sensitivity is reduced accordingly, the reception state deteriorates. Accordingly, there is a possibility that the broadcast signal may be missed after the detection operation of the power supply to the high-frequency unit 101 is canceled until the reception sensitivity of the high-frequency unit 101 is restored.

However, as described above, when the reception state continues for a predetermined good determination time, it is determined that the reception state is good and the supply power limiting operation is started to reduce the reception sensitivity of the high-frequency unit 101. Therefore, it is possible to appropriately cope with a temporary change in reception state.
From this state, when the reception state continues for a good determination time, the limiting operation control unit 125 determines that the reception state is good and starts the supply power limiting operation. At this time, the error rate S and the reference value Sth The limit amount is set according to the difference ΔS. At this time, if the difference ΔS between the error rate S and the reference value Sth is large, a relatively large first limiting amount is set, and if the difference ΔS is small, a relatively small second limiting amount is set.

  As a result, the power limiting circuit 123 reduces the power supplied to the high-frequency unit 101 and limits the amount of power set according to the difference ΔS. For this reason, the reception sensitivity of the high-frequency unit 101 is lowered. At this time, the limit amount is set based on the error rate S at this time, and even if the supplied power is reduced, the error rate is reduced. Since the supply power is limited by a limited amount that does not exceed the reference value Sth, a good reception state can be continued even if the supply power to the high-frequency unit 101 is reduced.

  From this state, if the reception state deteriorates, for example, when an automobile passes near the television receiver 1 or a user of the television receiver 1 enters a valley of a building, the error rate S Will drop. In response to this, in the limited operation control unit 125, when the error rate S exceeds the reference value Sth, when the relatively short failure determination time during which the reception state can be regarded as defective continues, the supply power Remove the restrictions.

That is, when the failure determination time has elapsed when the error rate S exceeds the reference value Sth, the restriction operation is canceled. At this time, the failure determination time is set to a time shorter than the good determination time, Since it is set to a period in which the reception sensitivity is promptly recovered in response to a sudden change in the reception state, it is possible to reduce the escape of broadcast signals.
Next, a third embodiment of the present invention will be described.

In the third embodiment, a sensitivity control unit 130 is provided in place of the supply power control unit 120 in the first embodiment. In addition, the same code | symbol is provided to the same part as the said 1st Embodiment, and the detailed description is abbreviate | omitted.
As shown in FIG. 5, the sensitivity control unit 130 compares the error rate S detected by the error rate detection unit 121 with the error rate S detected by the error rate detection unit 121 and the reference value Sth. A comparator 122, a variable attenuator 132 inserted between the rod antenna 3 and the high frequency unit 101, an attenuation control unit 134 for adjusting the attenuation of the variable attenuator 132, and the comparator 122. Based on the comparison result, it comprises an attenuation operation control unit 136 that controls the attenuation operation by the attenuation amount control unit 134.

  The variable attenuator 132 has, for example, a PIN diode 132a inserted between the rod antenna 3 and the high-frequency unit 101, and a current determination in which one end is connected to the cathode side of the PIN diode 132a and the other end is grounded. And a current determining variable resistor 132c having one end connected to the anode side of the PIN diode 132a and the other end grounded. The other end of the current determining resistor 132c is connected to the attenuation control unit 134, and the amount of current flowing through the diode 132a is adjusted by adjusting the voltage applied to the other end of the 132c by the attenuation control unit 134. To be adjusted.

  That is, as shown in FIG. 6, the operating resistance of the diode 132a decreases as the forward current increases. Accordingly, the attenuation control unit 134 decreases the forward current flowing through the diode 132a and increases its operating resistance, thereby increasing the attenuation, and conversely, increasing the forward current. Decrease in attenuation. In FIG. 6, the horizontal axis represents the forward current, and in FIG. 6, the forward current increases as it goes to the right. The vertical axis represents the operating resistance, and the higher the operating resistance in FIG. 6, the higher the operating resistance.

  Further, the attenuation operation control unit 136 monitors the comparison result in the comparator 122, and when the comparator 122 continues the state in which the error rate S is equal to or less than the reference value Sth for the good determination time. The attenuation amount control unit 134 is instructed to start the attenuation operation, assuming that the reception state is good. Further, when the error rate S exceeds the reference value Sth continues for the failure determination time shorter than the good determination time, it is determined that the reception state is defective and the attenuation control unit 134 is determined. An instruction to release the restriction operation is given.

The attenuation amount control unit 134 determines an attenuation amount according to, for example, a difference ΔS between the error rate S and the reference value Sth, and sets the first attenuation amount to be relatively large when the difference ΔS is large. When the difference ΔS is small, the second attenuation is set to a value smaller than the first attenuation.
The first attenuation amount and the second attenuation amount indicate that the error rate S after the signal level of the received broadcast signal is attenuated by the first and second attenuation amounts is the reference value Sth. It is set to a value that does not exceed, and is set in advance, for example, by an experiment.
Then, the reference value Sth of the error rate is set to a value that can be determined that a good reception state can be obtained. Specifically, for example, after the RS decoding in the error correction unit 103, As the error rate, 1 × 10 ⁻¹¹ that can be regarded as pseudo error free is set to a value that considers the margin.

  That is, the error rate S detected by the error rate detection unit 121 is equal to or less than the reference value Sth of the error rate, the error rate of the digital broadcast signal is small, and even if the reception sensitivity of the high frequency unit 101 is reduced, a good image is obtained. When it can be considered that sound can be obtained, the attenuation level is increased to suppress the signal level input to the high-frequency unit 101. At this time, the power supplied to the high-frequency unit 101 is set to a low amount of power that can ensure a good strong input characteristic with respect to the signal level after the suppression. As a result, when the signal is in a good reception state, the signal level is lowered, and by supplying power capable of ensuring good strong input characteristics with respect to the lowered signal level, reception is consequently performed. Compared with the case where power is supplied in accordance with the signal level, the power supplied to the high-frequency unit 101 can be reduced, that is, the power consumption can be reduced.

  On the other hand, when it is determined that the error rate S detected by the error rate detection unit 121 exceeds the error rate reference value Sth, the error rate of the digital broadcast signal is large, and good images and sound cannot be obtained. The amount of attenuation in the variable attenuator 132 is reduced, and the signal level input to the high frequency unit 101 is ensured. As a result, the signal level input to the high frequency unit 101 increases, and as a result, the reception sensitivity at the high frequency unit 101 is recovered.

Next, the operation of the third embodiment will be described.
If the current reception state is good and the error rate S is below the reference value Sth, and this state continues for a good judgment time, the attenuation operation control unit 136 has a good reception state. And the attenuation operation by the variable attenuator 132 is started. That is, as shown in FIG. 6, the PIN diode 132a has a smaller operating resistance as the forward current increases. Therefore, the value of the forward current flowing through the PIN diode 132a is reduced, and the resistance of the PIN diode 132a is reduced. By increasing the value, the amount of attenuation in the variable attenuator 132 is increased.

Thereby, the signal level of the broadcast signal input to the high frequency unit 101 is reduced, and this is input to the high frequency unit 101 to restore the video signal and the audio signal.
At this time, even if the attenuation amount is increased, the error rate S is set to a value that does not exceed the reference value Sth. Therefore, even if the attenuation amount is increased, the error rate S is increased. Does not exceed the reference value Sth, and a good reception state can be continued.

  From this state, if the reception state deteriorates, for example, when an automobile passes near the television receiver 1 or a user of the television receiver 1 enters a valley of a building, the error rate S Will drop. In response to this, the attenuation operation control unit 136 releases the attenuation operation when the error rate S exceeds the reference value Sth when a failure determination time during which the reception state can be regarded as defective continues. .

At this time, the defect determination time is set to a time shorter than the good determination time, and the reception sensitivity can be promptly recovered against a sudden change in the reception state, and the attenuation operation is performed. Therefore, it is possible to avoid missing the broadcast signal.
By canceling the attenuation operation, the amount of attenuation in the variable attenuator 132 is reduced, and the signal level of the broadcast signal input to the high frequency unit 101 is increased. As a result, the reception sensitivity of the high frequency unit 101 is increased. Recover. For this reason, the error rate S is recovered and a good reception state is secured.

  From this state, the radio wave state of the broadcast signal received by the antenna 3 is recovered, the state where the error rate S is again below the reference value Sth continues, and when this state continues for the good determination time, A damping operation is started. At this time, the amount of attenuation is set according to the error rate S and the reference value Sth and the difference ΔS at this point, and the larger the margin of the error rate S with respect to the reference value Sth, the larger the amount of attenuation is set. Is further attenuated and input to the high-frequency unit 101. Therefore, a broadcast signal having a high signal level can be avoided from being input to the high frequency unit 101, that is, good strong input characteristics can be ensured.

  In this way, the power supplied to the high frequency unit 101 is set so that the strong input characteristics are good with respect to the signal level to the high frequency unit 101 when the attenuation level with respect to the signal level of the broadcast signal is large. When the error rate S deteriorates, the amount of attenuation is reduced accordingly and the signal level is restored. As a result, the power supplied to the high-frequency unit 101 can be reduced. .

  In addition, when the power supplied to the high frequency unit 101 is reduced, if the signal level input with respect to the current flowing through the high frequency unit 101 is high, the strong input characteristics deteriorate and adverse effects such as intermodulation interference occur. May occur. However, in the third embodiment, the signal level of the input signal is adjusted so as to have a good strong input characteristic with respect to the power supplied to the high-frequency unit 101. The strong input characteristics can be improved regardless of the electric field strength of the broadcast signal. That is, it is effective to reduce power consumption and improve strong input characteristics at the same time.

Therefore, the strong input characteristic can be improved in this way, and the intermodulation interference can be further reduced. As a result, the error rate S can be further reduced.
In the third embodiment, a case has been described in which the attenuation operation is started and canceled when a predetermined good determination time or defective determination time continues for a change in the error rate S. However, it is not limited to this. As described above, there is a possibility that a broadcast signal may be missed due to a delay in recovery of the reception sensitivity. However, depending on whether the error rate S is equal to or less than the reference value Sth, the start of attenuation operation and You may make it cancel.

In each of the above embodiments, as described above, low power consumption can be achieved. Therefore, the present invention is particularly effective when applied to a portable or mobile television receiver. However, the present invention is not limited to this, and needless to say, the present invention can also be applied to a fixed television receiver.
In each of the above embodiments, as the error rate reference value Sth, the error rate after RS decoding in the error correction unit 103 is 1 × 10 ⁻¹¹ that can be regarded as pseudo error free, or The case of setting based on this has been described, but the present invention is not limited to this, and the error rate after Viterbi decoding may be set to 2 × 10 ⁻⁴ or based on this. . In addition, the value is not limited to a value that can be regarded as pseudo error free, and can be set arbitrarily. However, as described above, if the reference value Sth is set to a value that can be regarded as pseudo-error free, whether or not it is in a pseudo-error free state, that is, a good reception state. Therefore, by setting a value that is pseudo error free as the reference value Sth, it is possible to accurately detect whether the reception state is good.

  Moreover, although the case where the RS decoding and the Viterbi decoding are performed as the error processing in the error correction unit 103 has been described, only one of them may be performed, and the present invention is not limited to this. The present invention can be applied even when error correction processing is performed. In this case, as the reference value Sth of the error rate, a value that can be regarded as a good reception state may be set based on the error rate at the time of each error correction process.

  In each of the above embodiments, the case where the present invention is applied to the television receiver 1 that receives a terrestrial digital broadcast signal has been described. However, the present invention is not limited to this. For example, an image together with a digital radio broadcast or a digital radio broadcast signal is displayed. A receiver that can receive a signal or the like as a digital signal can also be applied. In short, a receiver that receives a digital signal and performs an error correction process on the digital signal. If so, it can be applied.

  In the above embodiment, the high frequency unit 101 corresponds to the high frequency unit, the OFDM demodulation unit 102 and the error correction unit 103 correspond to the error correction unit, and the MPEG demodulation unit 104, the speaker 13 and the liquid crystal device 4 are the reproduction processing unit. The error rate detection unit 121 corresponds to the error rate detection unit, the comparator 122, the power limiting circuit 123, and the limiting operation control unit 125 correspond to the supply power reduction unit, and the comparator 122 corresponds to the comparison unit. The good determination time corresponds to the first duration, and the failure determination time corresponds to the second duration. In FIG. 5, the variable attenuator 132, the attenuation amount control unit 134, and the attenuation operation control unit 136 correspond to the attenuation means.

It is an external view which shows an example of the television receiver to which this invention is applied. It is a block diagram which shows an example of the television receiver in 1st Embodiment. It is a characteristic view showing the correspondence between electric field strength and received image quality in digital television broadcasting and analog television broadcasting. It is a block diagram which shows an example of the television receiver in 2nd Embodiment. It is a block diagram which shows an example of the television receiver in 3rd Embodiment. FIG. 6 is a characteristic diagram illustrating characteristics of the PIN diode in FIG. 5.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 High frequency part 103 Error correction part 121 Error rate detection part 123 Power limit circuit

Claims (8)

A high-frequency unit that receives the digital broadcast signal and amplifies the broadcast signal corresponding to the designated station;
An error correction unit that performs error correction processing on the broadcast signal processed by the high-frequency unit;
In a digital broadcast receiver including a reproduction processing unit that performs reproduction processing based on a broadcast signal that has been subjected to error correction processing by the error correction unit,
Error rate detection means for detecting an error rate in the error correction processing;
A digital broadcast receiver comprising: power supply reduction means for reducing power supplied to the high-frequency unit when the error rate detected by the error rate detection means is equal to or less than a preset reference value.   2. The supply power reduction means increases the supply power reduction as the deviation between the error rate detected by the error rate detection means and the reference value increases. The digital broadcast receiver described. The supply power reduction means includes a comparison means for comparing the error rate detected by the error rate detection means and the reference value,
Based on the comparison result in the comparison means, when the state in which the error rate is equal to or less than the reference value continues for a first duration or longer, the reduction of the supplied power is started,
The reduction of the supplied power is canceled when the state in which the error rate exceeds the reference value continues for a second duration shorter than the first duration. The digital broadcast receiver according to 1 or 2. A high-frequency unit that receives the digital broadcast signal and amplifies the broadcast signal corresponding to the designated station;
An error correction unit that performs error correction processing on the broadcast signal processed by the high-frequency unit;
In a digital broadcast receiver including a reproduction processing unit that performs reproduction processing based on a broadcast signal that has been subjected to error correction processing by the error correction unit,
Error rate detection means for detecting an error rate in the error correction processing;
A digital broadcast receiver comprising: attenuation means for attenuating an input signal level to the high-frequency unit when an error rate detected by the error rate detection means is equal to or less than a preset reference value.   5. The digital broadcast reception according to claim 4, wherein the attenuation means increases the attenuation as the deviation between the error rate detected by the error rate detection means and the reference value increases. Machine. The attenuation means includes a comparison means for comparing the error rate detected by the error rate detection means and the reference value,
Based on the comparison result of the comparison means, when the state where the error rate is less than or equal to the reference value continues for a first duration or longer, the attenuation of the input signal level is started,
The attenuation of the input signal level is canceled when the state in which the error rate exceeds the reference value continues for a second duration shorter than the first duration. The digital broadcast receiver according to claim 4 or 5. The error correction unit performs Reed-Solomon decoding on the broadcast signal as the error correction processing,
The error rate detection means detects an error rate after the Reed-Solomon decoding,
The digital broadcast receiver according to claim 1, wherein the reference value of the error rate is set based on 1 × 10 ⁻¹¹ . The error correction unit performs Viterbi decoding and Reed-Solomon decoding in this order on the broadcast signal as the error correction processing,
The error rate detection means detects an error rate after the Viterbi decoding,
The digital broadcast receiver according to claim 1, wherein the reference value of the error rate is set based on 2 × 10 ⁻⁴ .

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