JP2003101426A - Broadcasting receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a broadcasting receiver with which a receiving state can be shifted into a satisfactory state by preventing the receiving state from being made adverse by simply amplifying a signal from an antenna. SOLUTION: A microcomputer finds an error rate from the output of a decoder for decoding a digital broadcasting signal as occasion demands, and controls the presence/absence of the amplification of an antenna amplifier. The presence/absence of the amplification of the antenna amplifier is determined by using a threshold e1 and a threshold e2 which is greater than the threshold e1 of two thresholds related to the error rate and comparing the current error rate with these thresholds. In such determination, the state of the presence/ absence of the amplification of the antenna amplifier just before the determination is considered as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadcast receiving apparatus for digital broadcasting, and more particularly to control of an antenna amplifier based on an error rate.

[0002]

2. Description of the Related Art An antenna amplifier used in a conventional broadcast receiving apparatus, for example, a broadcast receiving apparatus for terrestrial analog TV broadcasting, which amplifies a signal from an antenna, is used when the broadcast receiving apparatus itself is powered on. , The power is always supplied to the antenna amplifier. That is, when the power of the broadcast receiving apparatus is turned on, the antenna amplifier is always in the state of amplifying the signal from the antenna.

[0003]

However, when a system in which an antenna amplifier constantly amplifies a signal from an antenna, such as a conventional broadcast receiving apparatus, is also adopted in a broadcast receiving apparatus for terrestrial digital broadcasting, the When receiving digital broadcasting, especially in a mobile environment, the following problems may occur because the electric field strength fluctuates. That is, although the reception sensitivity can be increased by performing amplification by the antenna amplifier in a weak electric field, the reception level becomes a high input state in a strong electric field, which may cause saturation in the broadcast receiving apparatus or an interference wave component. This is a problem that the reproduced image or the like may be disturbed due to amplification or the like.

The present invention has been made in view of the above circumstances, and prevents deterioration of the reception state caused by simply amplifying the signal from the antenna and shifts the reception state to a good state. It is an object of the present invention to provide a broadcast receiving device capable of performing.

[0005]

Therefore, according to the invention as set forth in claim 1, an amplifying means for amplifying a received signal and a digital broadcast signal obtained by A / D converting an output signal from the amplifying means are decoded. In the broadcast receiving apparatus, the control means controls the gain of the amplification means based on the error rate obtained from the output of the decoding means at any time. It is characterized in that a comparison is made with different thresholds and the gain of the amplification means is controlled based on the comparison result. Since there are at least two thresholds to be compared with the error rate, the reception state indicated by the error rate can be divided into at least three states, and therefore, the gain control of the amplifying means based on the reception state can be more effectively performed. It is possible to do it in detail.

The control means may switch the presence / absence of amplification of the amplification means based on the comparison result by the comparison (claim 2).

In the invention described in claim 3, the control means comprises:
The first threshold and the first
And a second threshold larger than the threshold of. Furthermore, the control means considers the following four conditions as the conditions for determining the presence / absence of amplification of the amplification means. Condition 1: The error rate is less than a first threshold Condition 2: The error rate is greater than or equal to a first threshold and less than a second threshold Condition 3: The error rate is greater than or equal to a second threshold Certain condition 4: Whether the amplifying means immediately before making the determination is presence or absence of amplification In this case, when making the determination as to whether or not there is amplification, the state of presence or absence of amplification immediately before the determination is also taken into consideration. Not only that the reception condition is deteriorated due to the weak electric field (condition 4 is no amplification and condition 3 is satisfied), but also that the reception condition is deteriorated due to the strong electric field (condition 4 Is amplified and the condition 3 is satisfied) can also be detected.

In the invention according to claim 4, the control means comprises:
As a result of the condition 4, when the amplification means is not amplified immediately before the determination, the presence or absence of amplification of the amplification means is determined to be one of the following two operations. Operation 1: When the condition 1 is satisfied, the amplification of the amplifying means is left as it is. Operation 2: When the condition 2 or the condition 3 is satisfied,
When the condition 4 for switching the amplification of the amplifying means to the presence is not amplification and the condition 1 is satisfied, it is considered that the reception state is good without performing the amplification and the amplification can be left as it is ( Action 1). On the other hand, when the condition 4 is no amplification and the condition 2 or the condition 3 is satisfied, the possibility of the weak electric field is high, and therefore the reception state can be recovered by switching to the presence of amplification (operation 2 ).

The control means determines again whether or not amplification is performed by the amplification means in consideration of the conditions 1 to 3 on the basis of the error rate obtained after performing the operation 2, whereby the operation 2 is performed. The effect of switching the amplification to ON can be evaluated, and further, it can be determined what to do with or without amplification (Claim 5).

In a sixth aspect of the invention, the control means comprises:
As a result of the condition 4, when the amplifying means is in the presence of amplification immediately before the determination, the presence or absence of amplification of the amplifying means is determined to be one of the following two operations. Operation 3: When the above condition 1 or condition 2 is satisfied,
Operation 4 in which the amplification of the amplifying means is left as it is: When the condition 3 is satisfied, the condition 4 for switching the amplification of the amplifying means to no is present, and the condition 1 or the condition 2 is satisfied. In this case, it can be considered that the reception state is good by performing the amplification, and thus the amplification can be left (operation 3). On the other hand, when the condition 4 is amplification and the condition 3 is satisfied, it is highly possible that the reception state is deteriorated by performing the amplification, that is, the reception state is deteriorated by the strong electric field. Therefore, it is possible to recover the reception state by switching the mode without amplification (operation 4).

Based on the error rate obtained after performing the operation 4, the control means again considers the conditions 1 to 3 and again determines the presence or absence of amplification of the amplification means. It is possible to evaluate the effect of switching with or without amplification and further determine what to do with or without amplification (claim 7). For example, the operation 4
Thus, if the reception state changes from Condition 3 to Condition 2 or Condition 1, it means that the reception state is restored from the bad state to the good state by switching the amplification from presence to absence. This case corresponds to the poor reception due to the strong electric field. Therefore, in this case, by maintaining the presence / absence of the amplification without the amplification which is switched to the non-amplification by the operation 4, the good reception state is maintained.

[0012]

1 is a block diagram showing a configuration of a broadcast receiving apparatus 50 for receiving a terrestrial digital broadcast as an embodiment of the present invention. The operation of each unit of the broadcast receiving apparatus 50 will be described with reference to FIG.

The RF signal from the antenna 1 is input to the antenna amplifier 2. The antenna amplifier 2 is turned on / off from the microcomputer 8 that controls the operation of each unit of the broadcast receiving apparatus 50.
Depending on the F signal 21, the amplified RF signal or the non-amplified RF signal is sent to the tuner 3. Tuner 3
Tuning with respect to the signal from the antenna amplifier 2 is performed.
Then, the second IF unit 4 converts the signal from the tuner 3 into an intermediate frequency signal.

The signal converted by the second IF unit 4 is synchronized with the synchronization reproducing unit 5 for reproducing the synchronization signal necessary for the operation of each unit, and O
It is input to the FDM decoder 6. OFDM decoder 6
Of the signals input from the second IF unit 4
Demodulation processing based on the M transmission method is performed. The received data extracted by the OFDM decoder 6 is the MPEG decoder 7
Then, it is MPEG-decoded and sent to the display unit 9 as a video signal and an audio signal.

Error information 1 (reference numeral 11) obtained in the process of error correction in the OFDM decoder 6 or MPEG
Based on the error information 2 (reference numeral 12) obtained when the decoder 7 decodes / separates the video / audio signal, the microcomputer 8
Calculates BER (bit error rate), and
Turn on / off the antenna amplifier 2 based on the calculated BER
F control. FIG. 2 shows an example of a detailed circuit of the antenna amplifier 2. The circuit shown in FIG. 2 is an ON / OF from the microcomputer 8.
RF_IN (reference numeral 22) according to the level of the F signal 21
The RF signal input from the amplifier is amplified and output from RF_OUT (reference numeral 23), or RF_IN (reference numeral 22)
RF_O without amplifying the RF signal input from
An operation for switching whether to output from the UT (reference numeral 23) is performed.

FIG. 3 shows the relationship between electric field strength and BER. As shown in FIG. 3, BER is in a high state when the electric field strength is weak, and gradually decreases as the electric field strength increases, but rises again when the electric field strength increases to a certain level (part P in FIG. 3). ). In the portion P, the electric field strength (input level) becomes too strong and distortion occurs,
It corresponds to the state where the BER is deteriorated.

The microcomputer 8 has two thresholds for the BER, that is, a threshold e corresponding to a sufficiently good reception state.
1 and a threshold value e2 corresponding to a limit value at which an image cannot be reproduced, the reception state is shifted to a good state by ON / OFF control of the antenna amplifier 2 described later with reference to the flowchart of FIG. . In FIG. 3, B
The positions of the threshold values e1 and e2 are shown on the ER axis. Here, as shown in FIG. 3, the state in which the BER is lower than the threshold value e1 (good reception state) is the state A, and the threshold value e1 and the threshold value e.
The state between 2 (the range where reception is possible but close to the reception limit) is state B, and the state larger than the threshold value e2 (bad reception state) is state C.

FIG. 4 shows that when the state of the antenna amplifier 2 is OFF immediately before the microcomputer 8 performs ON / OFF control of the antenna amplifier 2 shown in FIG. Turn on / off antenna amplifier 2
It is a figure which shows which state of FF it changes. On the other hand, in FIG. 5, the microcomputer 8 has the antenna amplifier 2 shown in FIG.
When the state of the antenna amplifier 2 is ON immediately before the ON / OFF control of (the initial state), the microcomputer 8 causes the BE
FIG. 8 is a diagram showing which of ON and OFF states the antenna amplifier 2 is to be moved to, based on R.

As shown in FIG. 4, if the error rate is state A when the antenna amplifier 2 is OFF in the initial state, the antenna amplifier 2 is already in a good reception state in the OFF state. Is not required, and the current state is maintained (that is, the antenna amplifier 2 remains off) (T1).

The antenna amplifier 2 is OFF in the initial state
When the error rate is in the state B, the antenna amplifier 2 is once turned on (T2), and when the next state is further recovered to the state A or remains in the state B. Turns on the antenna amplifier 2
Since it can be considered that there is an improvement effect by turning on N, the antenna amplifier 2 is maintained at ON (T
3). On the other hand, when the state is deteriorated to the state C after the antenna amplifier 2 is turned on once, it means that the antenna amplifier 2 is turned on and deteriorated. Therefore, the antenna amplifier 2 is turned off. It is returned (T4).

The antenna amplifier 2 is OFF in the initial state
When the error rate is the state C in the case of, the antenna amplifier 2 is once turned on (T5), and the improvement effect is confirmed. As a result, if the state is improved to the state A or the state B, it means that the reception state has been improved by turning on, so that the state is kept on (T6). On the other hand, if the antenna amplifier 2 remains in the state C even after being turned on once, the improvement effect is unknown, but when the reception state is restored later, the normal image is quickly reproduced on the display unit 9. Aiming at that, antenna amplifier 2 is ON
It is maintained as it is (T6).

Next, referring to FIG. 5, when the antenna amplifier 2 is ON in the initial state, the antenna amplifier 2 is turned ON / OFF.
The OFF control will be described. If the error rate is the state A or the state B when the antenna amplifier 2 is ON as the initial state, it can be considered that the antenna amplifier 2 is ON and the reception state is good at least in the state B or higher. Because it can, antenna amplifier 2
Is kept ON (T10). On the other hand, when the antenna amplifier 2 is ON in the initial state and the error rate is state C, the antenna amplifier 2 is turned ON.
Since there is a possibility that the reception state is deteriorated (that is, in a strong electric field) due to the above, the antenna amplifier 2 is once turned off (T11), and the improvement effect due to the turning off is confirmed.

When the state is restored to the state A or the state B by turning off the antenna amplifier 2, that is, when the improvement effect is obtained, the antenna amplifier 2 is kept off (T12). When the antenna amplifier 2 is turned off and the state C is still maintained, the improvement effect is unknown, but when the reception state is restored later, the normal image is reproduced on the display unit 9 immediately. Aiming, the antenna amplifier 2 is turned back on (T13).

FIG. 6 is a flowchart for realizing the ON / OFF control of the antenna amplifier 2 described with reference to FIGS. 4 and 5. Note that the processing of FIG. 6 is executed as a subroutine in the microcomputer 8 separately from the main processing (which demodulates / decodes a received signal and reproduces sound), for example, at regular time intervals. Further, when the broadcasting receiver 50 is initially powered on, the antenna amplifier 2 is turned off.
It is assumed to be FF.

In step S1 of FIG. 6, the initial state of the antenna amplifier 2 is confirmed. If the initial state of the antenna amplifier 2 is OFF, the process proceeds to step S2, and if the initial state of the antenna amplifier 2 is ON, the process proceeds to step S10. That is, the ON / OFF control (initial state OFF) of FIG. 4 is performed by the flowcharts S2 to S of FIG.
The ON / OFF control (initial state ON) of FIG. 5 corresponds to the processing of step S9, and corresponds to the processing of steps S10 to S15.

In step S2, the BER is calculated and whether this BER is smaller than the threshold value e1 (ie,
It is determined whether or not it is in the state A (S3). If the BER is smaller than the threshold value e1 (S3: YES), the process ends (corresponding to T1 in FIG. 4). That is, the antenna amplifier 2 is kept off. When the BER is equal to or greater than the threshold value e1 (S3: NO), it is determined in step S4 whether or not the BER calculated in step S2 is smaller than the threshold value e2 (that is, whether or not it is in the state B). It

In step S4, the BER is the threshold value e2.
When it is determined that it is smaller (in the state B) (S4:
YES), once in step S6 the antenna amplifier 2
Is turned on, and then the BER is calculated again in step S7. In step S8, it is determined whether or not the BER calculated in step S7 is smaller than the threshold value e2, that is, the state A
Alternatively, it is determined whether or not the state B is entered. When BER is smaller than the threshold value e2 (S8: YES), that is,
When in state A or state B, antenna amplifier 2 is ON
The process ends as it is (corresponding to T3 in FIG. 4). BER
Is greater than or equal to the threshold value e2 (S8: NO), that is,
In the state C, the antenna amplifier 2 is turned off (S9), and the process ends (corresponding to T4 in FIG. 4).

On the other hand, in step S4, step S
When it is determined that the BER calculated in 2 is equal to or greater than the threshold value e2 (in the state C) (S4: NO), the antenna amplifier 2 is turned on in step S5, and the processing ends (in T6 of FIG. 4). Correspondence).

If the initial state of the antenna amplifier 2 is ON in step S1, the process proceeds to step S10 and BER is calculated. Then, in step S11,
It is determined whether or not the BER calculated in step S10 is smaller than the threshold value e2, that is, whether or not the state is the state A or the state B. BER is smaller than the threshold value e2, that is,
When it is determined that the state is the state A or the state B (S11: Y
ES), the processing ends with the antenna amplifier 2 kept ON (corresponding to T10 in FIG. 5).

In step S10, the BER is the threshold value e.
If it is 2 or more, that is, if it is determined to be in the state C (S11: NO), the antenna amplifier 2 is once turned off in step S12, and then BE in step S13.
R is calculated. In step S14, step S13
It is determined whether or not the BER calculated in step 1 is smaller than the threshold value e2, that is, whether or not the state is in the state A or the state B.

The BER calculated in step S13 is the threshold value e.
If it is smaller than 2, that is, if it is in the state A or the state B (S14: YES), the process ends with the antenna amplifier 2 kept OFF (corresponding to T12 in FIG. 5). When the BER calculated in step S13 is equal to or greater than the threshold value e2, that is, in the state C (S14: NO), the antenna amplifier S15 is turned on (S15), and the process ends (corresponding to T13 in FIG. 5).

ON / O of the antenna amplifier 2 described above
The FF control always leads to the direction in which the reception state becomes good. Since it is usually impossible for a rapid change in the reception status to occur repeatedly,
By executing the ON / OFF control process shown in (1) at a time interval of, for example, about 1 second, the effect on the reproduced video or audio by applying the ON / OFF control of the antenna amplifier as shown in FIG. It will be avoided in practice.
Further, in addition to executing the ON / OFF control shown in FIG. 6 at time intervals of about 1 second, the antenna amplifier 2 is turned ON →
When switching from OFF or OFF to ON, the switching is not performed suddenly, but for example, by gradually providing the switching by giving a time constant to the circuit for ON / OFF,
It is also possible to more surely avoid the influence on the reproduced video or audio by applying the ON / OFF control of the antenna amplifier as shown in FIG.

Further, under the bad condition that the reception state becomes the state C regardless of the ON / OFF state of the antenna amplifier 2, the ON / OFF control shown in FIG. May be repeatedly turned on and off, but under such conditions, by performing processing such as muting the audio that is played back, there is no possibility that a user who views the playback video or audio may feel uncomfortable. It can be avoided.

The broadcast receiving apparatus shown in FIG. 1 is an example of a broadcast receiving apparatus having a structure corresponding to terrestrial digital broadcasting which adopts the OFDM system as a broadcasting system. However, it goes without saying that the present invention can be applied to broadcast receiving devices for digital broadcasting according to various broadcasting systems.

[0035]

As described above, according to the broadcast receiving apparatus of the present invention, it is possible to always bring the reception state to a good state in the reception of the digital broadcast whose reception state fluctuates every moment. In particular, in a situation where a vehicle equipped with the broadcast receiving apparatus of the present invention travels in a place of a strong electric field, the antenna amplifier can be turned off, the reception level becomes excessively high, and cross modulation or intermodulation occurs. As a result, it is possible to avoid a situation in which the reception state is deteriorated or a situation in which the interfering wave is amplified too much. At the same time, in a weak electric field, it is possible to turn on the antenna amplifier to increase the reception sensitivity and improve the reception state.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a broadcast receiving apparatus as an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of an antenna amplifier in the broadcast receiving device of FIG.

FIG. 3 is a graph showing the relationship between BER and electric field strength.

FIG. 4 is a diagram showing a transition of the ON / OFF state of the antenna amplifier by the ON / OFF control of the antenna amplifier shown in FIG. 6 when the initial state is the antenna amplifier OFF.

FIG. 5 shows the case where the antenna amplifier is ON in the initial state,
By the ON / OFF control of the antenna amplifier shown in FIG.
It is a figure showing the transition of the ON / OFF state of an antenna amplifier.

6 is a flowchart showing ON / OFF control of an antenna amplifier, which is executed by a microcomputer of the broadcast receiving apparatus shown in FIG.

[Explanation of symbols]

1 antenna 2 antenna amplifier 3 tuners 4 Second IF section 5 Synchronous playback section 6 OFDM decoder 7 MPEG decoder 8 microcomputer 9 Display

Claims (7)

[Claims] 1. An amplifying means for amplifying a received signal, a decoding means for decoding a digital broadcast signal obtained by A / D converting an output signal from the amplifying means, and an error obtained from the output of the decoding means at any time. In the broadcast receiving device, comprising: a control unit that controls the gain of the amplification unit based on a rate, the control unit compares the error rate with at least two different thresholds related to the error rate, and A broadcast receiving device, characterized in that the gain of the amplifying means is controlled based on a comparison result. 2. The broadcast receiving apparatus according to claim 1, wherein the control unit switches presence / absence of amplification of the amplification unit based on a comparison result of the comparison. 3. The control means uses the first threshold value and a second threshold value larger than the first threshold value as the threshold value relating to the error rate, and determines whether or not amplification by the amplification means is performed. Consider the following four conditions as
The broadcast receiving device according to claim 2, wherein: Condition 1: The error rate is less than the first threshold Condition 2: The error rate is greater than or equal to the first threshold and less than the second threshold Condition 3: The error rate is the second Condition 4 which is equal to or more than the threshold value of: whether the amplification means immediately before the determination is performed or not. 4. The control means, as a result of the condition 4, when the amplification means is not amplified immediately before the determination, the presence or absence of amplification of the amplification means is controlled by the following two operations. The broadcast receiving apparatus according to claim 3, wherein the broadcast receiving apparatus determines one of them. Operation 1: When the condition 1 is satisfied, the amplification of the amplifying means is left as it is. Operation 2: When the condition 2 or the condition 3 is satisfied,
Switching the amplification of the amplification means to ON 5. The control means again determines the presence / absence of amplification of the amplification means in consideration of the conditions 1 to 3 based on the error rate obtained after performing the operation 2. The broadcast receiving device according to claim 4, wherein 6. The control means, as a result of the condition 4, when the amplification means has amplification immediately before the determination, the presence or absence of amplification of the amplification means is controlled by the following two operations. The broadcast receiving apparatus according to any one of claims 3 to 5, characterized in that the broadcast receiving apparatus is determined. Operation 3: When the above condition 1 or condition 2 is satisfied,
Operation 4 in which the amplification of the amplification means is left as it is 4: When the condition 3 is satisfied, the amplification of the amplification means is switched to no operation 7. The control means, based on the error rate obtained after performing the operation 4, determines again the presence or absence of amplification of the amplification means in consideration of the conditions 1 to 3. The broadcast receiving device according to claim 6.