JP4698905B2 - Digital broadcast receiver having AGC judgment value update function - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a receiver for digital broadcasting, and more particularly to determination of a reception state based on an AGC voltage.
[0002]
[Prior art]
In general, a digital broadcast receiving apparatus such as DAB (Digital Audio Broadcasting) has a high frequency amplification of an RF signal from an antenna, a conversion from an RF signal to an IF signal of an intermediate frequency, and an antenna input according to the received electric field strength. Main components are a tuner unit that performs AGC (automatic gain control) for controlling the gain, a decoder unit that performs decoding processing based on the IF signal, and a microcontroller that controls the entire decoder unit and other receiving devices. As a major component. The AGC voltage output from the AGC circuit corresponds to the AGC control state, and the microcontroller determines the reception state by comparing this AGC voltage with a preset fixed AGC determination value. Can do. Such determination of the reception state is appropriately performed at the time of frequency seek operation, program follow-up operation, or the like by the microcontroller.
[0003]
Since the AGC voltage is so-called hardware information generated in the tuner unit, it is obtained more quickly than so-called software information such as BER (bit error rate) and AFC (automatic frequency control) information obtained by operating the decoder unit. It is done. Therefore, the microcontroller can use the AGC voltage to determine the reception state more quickly than when software information such as BER and AFC is used, speed up the frequency seek operation, and respond to the program following operation. Speed can be increased.
[0004]
[Problems to be solved by the invention]
However, the AGC voltage as hardware information may vary for each set of receiving apparatuses. If the AGC voltage varies from set to set, the same value is used for each set of AGC determination values used by the microcontroller, so the reception state may not be correctly determined. That is, the determination of the reception state based on the AGC voltage in the conventional digital broadcast receiving apparatus is accompanied by instability / inaccuracy due to variations in the AGC voltage for each set. Although it is possible to inspect and adjust the variation in AGC voltage for each set on the production line, this leads to an increase in production man-hours.
[0005]
The present invention has been made in view of such circumstances. That is, the present invention has a function of adjusting the determination value of the AGC voltage by itself, and eliminates the instability / uncertainty of the determination of the reception state by the AGC voltage caused by the variation of the AGC voltage for each set. An object of the present invention is to provide a digital broadcast receiving apparatus that can be used.
[0006]
[Means for Solving the Problems]
Therefore, the invention according to claim 1 monitors an error rate of a received digital broadcast signal in a digital broadcast receiver having an AGC (auto gain control) circuit that controls the gain of an antenna input according to the electric field strength, When it is detected that the error rate is within a predetermined range, the AGC voltage that is the output of the AGC circuit at that time is stored as an AGC determination value, and the AGC voltage that changes as needed and the stored AGC determination value are stored. Receiving state determining means for comparing and determining the receiving state is provided. The error rate corresponds to the reception state, and if the AGC voltage when the error rate enters the predetermined range is stored and used as the AGC determination value, even if the AGC voltage varies from set to set, The stored AGC determination value correctly corresponds to the reception state in each receiving apparatus. Therefore, by using the stored AGC determination value, the influence on the determination of the reception state due to the variation in the AGC voltage for each apparatus is eliminated.
[0007]
According to a second aspect of the present invention, there is provided a digital broadcast receiving apparatus for receiving a digital broadcast that provides video or audio as a main broadcast, and an AGC (auto gain control) that controls the gain of an antenna input in accordance with the electric field strength. ) Circuit, a decoder for decoding video or audio data from the received digital broadcast signal, and a microcontroller for obtaining error information from the decoder and calculating an error rate. In this case, the microcontroller monitors the error rate when the initial power is turned on, and when detecting that the error rate is within a predetermined range, the AGC voltage that is the output of the AGC circuit at that time is used as the AGC determination value. By storing the flag indicating that the AGC determination value has been stored, the AGC voltage that changes from time to time is not detected without detecting that the error rate falls within the predetermined range, and the stored AGC voltage. The reception state is determined by comparing with the determination value. The error rate corresponds to the reception state, and if the AGC voltage when the error rate enters the predetermined range is stored and used as the AGC determination value, even if the AGC voltage varies from set to set, The stored AGC determination value correctly corresponds to the reception state in each receiving apparatus. The microcontroller monitors the error rate when the device is initially powered on and stores the AGC determination value. Thereafter, the microcontroller uses the AGC determination value that correctly corresponds to the reception state in each receiving device to determine the reception state. Execute.
[0008]
When the digital broadcast receiving apparatus further includes an operation unit connected to the microcontroller, the microcontroller further monitors the error rate when detecting that a predetermined operation is performed via the operation unit. However, when it is detected that the error rate is within a predetermined range, the AGC voltage that is the output of the AGC circuit at that time may be stored as an AGC determination value. In this case, the AGC determination value can be updated by operating the operation unit.
[0009]
The microcontroller also has an initial value set in advance as an AGC determination value, monitors the error rate, and stores the AGC voltage when the error rate is within a predetermined range, replacing the initial value with the initial value. (Claim 4). In other words, the microcontroller has a default value as the AGC determination value, and updates the AGC determination value when the initial power is turned on or when a predetermined operation is performed.
[0010]
Preferably, the predetermined range includes an error rate value corresponding to the reception limit. In this case, by comparing the AGC voltage with the stored AGC determination value, it is possible to determine whether the reception is possible or the reception is impossible.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing a configuration of a broadcast receiving apparatus 10 that receives a DAB broadcast as an embodiment of the present invention. The broadcast receiving apparatus 10 includes a DAB tuner 1, a DAB decoder 3, and a microcomputer 5 as main components. The DAB tuner 1 performs high-frequency amplification of an RF signal input from an antenna, conversion from an RF signal to an intermediate-frequency IF signal, AGC (auto gain control), and the like. The DAB decoder 3 decodes a signal from the DAB tuner 1 under the control of the microcomputer 5 and extracts DAB audio data and the like. The extracted audio data is output from the DAB decoder 3 as an audio signal.
[0012]
The microcomputer 5 is a microcontroller that controls various functions of the broadcast receiving apparatus 10 such as frequency seek operation and program pair tracking operation for a specified channel. The microcomputer 5 always calculates the BER (bit error rate) based on the error information from the DAB decoder 3, and also acquires AFC information regarding the convergence state of AFC (automatic frequency control) executed by the DAB decoder 3. Can do. The AGC voltage that is the output of the AGC circuit in the DAB tuner 1 is also provided to the microcomputer 5, and the microcomputer 5 performs AD conversion on this AGC voltage and uses it to determine the reception state. This determination of the reception state is appropriately performed when performing a frequency seek operation, a program pair following operation, or the like.
[0013]
The microcomputer 5 can store an AGC determination value as a determination value for comparing the AGC voltage input from the DAB tuner 1 and determining the reception state. As will be described later with reference to FIG. 3, the AGC determination value is updated with the AGC voltage when the BER is almost the reception limit value when the microcomputer 5 is initially turned on. The microcomputer 5 is configured to be able to eliminate the influence on the determination of the reception state due to the variation of the AGC voltage for each set of the broadcast receiving apparatus by using the updated AGC determination value.
[0014]
The situation in which the AGC voltage is different for each set is explained by a graph associating the BER and the AGC voltage shown in FIG. FIG. 2 shows a graph representing the relationship between the BER and the AGC voltage for the two broadcast receiving apparatuses A and B. Note that the BER is an index that can accurately determine which value cannot be received at the design stage of the broadcast receiving apparatus, and has a property that the value that cannot be received varies from set to set. It should be noted that there is no. FIG. 2 shows a case where the reception limit BER is 2.0 × E−2 as an example. That is, when the BER is smaller than 2.0 × E−2, the reception is possible, and when the BER is 2.0 × E−2 or more, the reception is impossible.
[0015]
As shown in FIG. 2, in the broadcast receiving apparatus A, the AGC voltage corresponding to the reception limit BER is 3.5V. Therefore, the broadcast receiving apparatus A cannot receive when the AGC voltage is 3.5V or more. When the AGC voltage is smaller than 3.5V, the reception is possible. On the other hand, in the broadcast receiving apparatus B, the AGC voltage corresponding to the reception limit BER is 3.0 V. Therefore, the broadcast receiving apparatus A is in a state incapable of receiving when the AGC voltage is 3.0 V or more, and the AGC voltage When the value is smaller than 3.0V, the reception is possible. Therefore, in order to correctly determine the reception state in each broadcast receiving apparatus, the AGC determination value is set to 3.5 V in the broadcast receiving apparatus A, and the AGC determination value is set to 3.0 V in the broadcast receiving apparatus B. Must be set. The flowchart of FIG. 3 shows an AGC determination value update process for achieving this.
[0016]
In the flowchart of FIG. 3, the reception limit BER (2.0 × E−2 in the case of FIG. 2) is represented as BER_A. In FIG. 3, the AGC determination value set as a provisional value at the time of initial power-on is AGC_A, and the AGC determination value newly set by the processing of FIG. 3 is expressed as AGC_B. The update flag S is a flag indicating whether or not the AGC determination value has already been updated. 3 is executed as a subroutine for the main process when the initial power is turned on under the control of the microcomputer 5.
[0017]
When the update process of FIG. 3 is started during reception of the DAB broadcast, first, in step S1, it is determined whether or not the AGC determination value has already been updated from the provisional value AGC_A by the update process of FIG. When the AGC determination value has already been updated and the update flag S is set to ON (S1: ON), this process ends. If the AGC determination value has not yet been updated and the update flag S is OFF (S1: OFF), the process proceeds to step S2.
[0018]
In step S2, the process waits until the BER (reception BER) of the current reception data falls within a certain range ((BER_A) ± α) from the reception limit BER (BER_A). When the BER of the received data falls within the range of (BER_A) ± α (S2: YES), in step S3, the AGC voltage from the DAB tuner 1 at that time is captured, and the provisional AGC voltage (AGC_B) is provisionally. The AGC determination value (AGC_A) is updated. For example, when the BER changes as shown in FIG. 4A and the AGC voltage at this time changes as shown in FIG. 4B, the BER is between (BER_A) ± α. The AGC voltage (AGC_B) at the time t1 when entering is used as a value for updating. In step S3, the update flag S is set ON. After step S3, this process ends.
[0019]
As described above, by performing the update process shown in FIG. 3, the AGC determination value can be set to the AGC voltage value corresponding to the actual reception limit in each broadcast receiving apparatus. In the example of FIG. 2, by performing the update process shown in FIG. 3, the AGC determination value is set to 3.5 V in the broadcast receiving device A, and the AGC determination value is set to 3.0 V in the broadcast receiving device B. can do. Therefore, according to the update process of the AGC determination value shown in FIG. 3, the AGC determination value is updated to an appropriate value when the broadcast receiver is initially turned on, and thereafter, the updated appropriate AGC determination value is used to determine the reception state. Will be used for this purpose.
[0020]
As a modification of the update process shown in FIG. 3, the AGC determination value update process may be manually started by operating an operation unit (not shown) of the broadcast receiving apparatus 10. In the AGC determination value update process shown in FIG. 3, once the BER enters the range of (BER_A) ± α, the AGC voltage at that time is used as the AGC determination value, but the BER is in the range of (BER_A) ± α. It is also possible to obtain a plurality of AGC voltages for update by performing detection of entering a plurality of times, and use an average value thereof as an AGC determination value.
[0021]
Further, for example, even when it is determined in the update process of FIG. 3 that the BER is near the reception limit and the AGC determination value should be updated, the AFC information obtained from the decoder unit 3 does not fall within the reception limit. In the case where it is determined that the AGC determination value is not updated, the AFC determination value update process shown in FIG.
[0022]
【The invention's effect】
As described above, according to the present invention, even if the AGC voltage varies from set to set, the AGC determination value can be automatically adjusted to the AGC voltage value of the reception limit specific to the apparatus. In order to eliminate the variation in the AGC voltage for each broadcast receiving apparatus as in the prior art, there is no need for production man-hours for managing the variation in the production process and improving the accuracy of the device. Therefore, even if the AGC voltage varies from set to set, the frequency seek operation and the program follow-up operation are quickly executed after the instability / uncertainty in the judgment of the reception state using the AGC voltage is surely eliminated. can do.
[Brief description of the 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 graph showing the relationship between BER and AGC voltage for two broadcast receivers when there is variation in AGC voltage.
FIG. 3 is a flowchart showing an AGC determination value update process executed by the broadcast receiving apparatus of FIG. 1;
FIG. 4 is a graph showing an example of changes in BER and AGC voltage.
[Explanation of symbols]
1 DAB tuner 3 DAB decoder 5 Microcomputer 5
10 Broadcast receiver

Claims (5)

In a digital broadcast receiver having an AGC (automatic gain control) circuit that controls the gain of an antenna input according to the electric field strength,
The error rate of the received digital broadcast signal is monitored, and when the error rate is detected to be within a predetermined range, the AGC voltage that is the output of the AGC circuit at that time is stored as an AGC determination value, A digital broadcast receiving apparatus comprising: a reception state determining means for determining whether or not the digital broadcast signal can be received by comparing the AGC voltage that changes as needed and the stored AGC determination value. 2. The reception state determining unit calculates an average value of a plurality of AGC voltages when the error rate falls within the predetermined range, and stores the average value as the AGC determination value. The digital broadcast receiver described in 1. A digital broadcast receiver for receiving a digital broadcast that provides video or audio as a main broadcast,
An AGC (automatic gain control) circuit that controls the gain of the antenna input according to the electric field strength;
A decoder that decodes the video or audio data from the received digital broadcast signal; and a microcontroller that obtains error information from the decoder and calculates an error rate,
The microcontroller further monitors the error rate when the initial power is turned on, and when detecting that the error rate is within a predetermined range, determines the AGC voltage which is the output of the AGC circuit at that time. By storing a value and setting a flag indicating that the AGC determination value is stored, the AGC voltage that changes at any time is detected without detecting that the error rate falls within the predetermined range. And determining whether the digital broadcast signal can be received by comparing the stored AGC determination value with the stored AGC determination value. 4. The microcontroller according to claim 3, wherein the microcontroller calculates an average value of a plurality of AGC voltages when the error rate falls within the predetermined range, and stores the average value as the AGC determination value. Digital broadcast receiver.   In a digital broadcast receiver having an AGC (automatic gain control) circuit that controls the gain of an antenna input according to the electric field strength and capable of performing a frequency seek operation or a program follow-up operation,
  The error rate of the received digital broadcast signal is monitored, and when the error rate is detected to be within a predetermined range, the AGC voltage that is the output of the AGC circuit at that time is stored as an AGC determination value, Reception state determination means for determining whether or not the digital broadcast signal can be received by comparing the AGC voltage, which changes as needed, during the frequency seek operation or program follow-up operation with the stored AGC determination value. A digital broadcast receiver characterized by the above.

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