JP2005006065A - Digital broadcasting receiver and method for displaying reception level - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To display an accurate receiving state by displaying a reception level on the basis of a BER when the bit error rate (BER) can be measured, and otherwise by displaying the reception level on the basis of C/N. <P>SOLUTION: The digital broadcasting receiver 10 has a tuner 12, a demodulator 13, a display unit 15, a CPU 17, and a memory 16 storing a conversion formula for converting a BER value and the C/N value of a received signal from the tuner 12. The digital broadcasting receiver 10 selects a signal with a desired frequency from a digital broadcasting signal inputted from an antenna 11, and demodulates the received signal. It measures the BER value and the C/N value of the demodulated received signal, and displays the receiving level of the received signal by obtaining the conversion formula corresponding to the measured BER value or the C/N value from the memory 16, and by calculating the receiving level of the received signal. The digital broadcasting receiver 10 displays the receiving level by converting the BER value or the C/N value to the receiving level in a measurable range of the BER value, and by converting the C/N value to the receiving level in a range other than that. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital broadcast receiving apparatus and a reception level display method. More specifically, the level of a received signal is displayed as a level to adjust an antenna installation angle or confirm whether a digital broadcast can be received. It is something that can be done.
[0002]
[Prior art]
Conventionally, as a method of displaying the reception level, there is a method of displaying using the reception intensity based on the input voltage of the input signal. The level of input power can be detected by converting from the AGC voltage of the tuner unit. There is a method in which the AGC voltage is converted into a reception level and displayed.
[0003]
However, although it is possible to determine whether or not the signal strength of the received signal is within the reception range with only the input voltage, there are cases where the received quality does not match whether or not the received signal is actually receivable. This is because, when the C / N (Carrier to Noise) of the received signal has deteriorated, even if the reception power level is good, the reception quality is poor, an error occurs, the video is disturbed, the audio May be interrupted and may not be received normally.
[0004]
As means for solving the above-described point, there is a method in which a demodulation unit is provided with a BER (bit error rate) measurement function and the reception level is displayed using BER (for example, refer to Patent Document 1 and Patent Document 2). This is because the C / N level of the received signal is obtained by measuring the BER characteristic with respect to the C / N in advance and converting the data from the BER measured at the time of signal reception into the corresponding C / N value. And the reception level is displayed based on this. By using the BER, the reception state can be accurately measured and the reception level can be displayed with high accuracy. As a result, the reception power level is high, but when C / N deteriorates and a reception error occurs, the BER also becomes an unreceivable level, so the reception level is also displayed low and a display corresponding to the reception state is displayed. It becomes possible.
[0005]
[Patent Document 1]
JP-A-4-180313
[Patent Document 2]
JP 10-28065 A
[0006]
[Problems to be solved by the invention]
However, the method for measuring BER has a problem that the measurement range for C / N is limited. When C / N is better than a certain value, BER becomes 0 and cannot be measured. Further, even when C / N is worse than a certain value, there is a problem that measurement is not possible because the BER is fixed near the level value.
[0007]
The present invention has been made in view of the above circumstances. When the BER is measurable, the reception level is displayed based on the BER. In other cases, the reception level is displayed based on the C / N. The present invention has been made for the purpose of providing a digital broadcast receiving apparatus and a reception level display method capable of displaying an accurate reception state by displaying.
[0008]
[Means for Solving the Problems]
The first technical means includes a tuner unit that selects a signal having a desired frequency from a digital broadcast signal input from an antenna, a demodulation unit that demodulates the selected reception signal, and a transmission error in the demodulated reception signal. A BER measuring unit that measures a bit error rate (BER value) indicating whether or not a problem has occurred, a C / N measuring unit that measures a C / N value of the demodulated received signal, and a BER value and a C / N value received A memory that stores a conversion equation for converting into a level, a calculation unit that calculates a conversion equation corresponding to the measured BER value or C / N value from the memory, and calculates the reception level of the received signal, and the calculation And a display unit for displaying the received level.
[0009]
In the first technical means, when the reception level is displayed in the first technical means, the measurement range by the C / N measurement unit, the BER value measurable range by the BER measurement unit, and other ranges In the measurable range of the BER value, the BER value or C / N value is converted into a reception level and displayed, and in other ranges, the C / N value is converted into a reception level and displayed. It is characterized by that.
[0010]
According to the third technical means, when the reception level is displayed based on the BER value in the first or second technical means, the BER value is received during the period in which the BER measurement unit can measure the BER value. In the period when the BER value cannot be measured, the C / N value is converted into a reception level and displayed.
[0011]
The fourth technical means detects the modulation scheme and coding rate of the received signal when displaying the reception level based on the BER value in any one of the first to third technical means, and the modulation scheme In addition, a conversion formula corresponding to a coding rate is selected from the memory, a reception level of the reception signal is calculated, and the calculated reception level is displayed as an absolute reception level.
[0012]
The fifth technical means detects the modulation method and the coding rate of the received signal when displaying the reception level based on the C / N value in any one of the first to third technical means, A conversion formula corresponding to a modulation method and a coding rate is selected from the memory, a reception level of the reception signal is calculated, and the calculated reception level is displayed as a relative reception level.
[0013]
A sixth technical means includes a data table storing information on the frequency characteristics of the BER value with respect to the C / N value for each frequency in any one of the first to fifth technical means, and displays a reception level. In this case, the data table corresponding to the frequency selected by the tuner unit is referred to, and the received level is displayed by correcting the change amount of the frequency with respect to the frequency characteristic based on the data table. Is.
[0014]
A seventh technical means is the first technical means, wherein the demodulation unit has a reflection amount measurement unit for measuring a reflection amount of the received signal, and stored in the memory according to the measured reflection amount. The conversion formula for converting the C / N value into the reception level is corrected.
[0015]
According to an eighth technical means, in the first technical means, the demodulating unit has a disturbance level detecting unit for detecting a disturbance level due to an analog signal in a band of the received digital signal, and the detected analog signal is used. According to the interference level, the conversion formula stored in the memory for converting the C / N value into the reception level is corrected.
[0016]
The ninth technical means detects the modulation system and coding rate according to the hierarchy of the received signal being viewed when displaying the reception level in any one of the first to eighth technical means. The conversion formula corresponding to the modulation scheme and coding rate is selected from the memory, the reception level of the received signal is calculated, and the calculated reception level is displayed.
[0017]
In the tenth technical means, in any one of the first to eighth technical means, when the reception level is displayed, the modulation method and the coding rate are detected for each layer included in the received signal, and the modulation is performed. The conversion formula corresponding to the method and coding rate is selected from the memory, the reception level of the received signal is calculated for each layer, and the calculated reception level can be displayed for each layer. is there.
[0018]
In an eleventh technical means according to any one of the first to eighth technical means, the display unit has a hierarchy selection unit for selecting a hierarchy for displaying a reception level on the screen, and the selected hierarchy The modulation method and coding rate corresponding to the signal are detected, the conversion method corresponding to the modulation method and coding rate is selected from the memory, the reception level of the received signal is calculated, and the calculated reception level is displayed. It is characterized by that.
[0019]
A twelfth technical means according to any one of the fourth, fifth, and ninth technical means, wherein the display section selects a display method for selecting either the absolute reception level or the relative reception level on the screen. A modulation scheme and a coding rate according to the hierarchy of the received signal being viewed, and a conversion formula corresponding to the display method selected by the reception level selection unit is selected from the memory The reception level of the reception signal is calculated, and the calculated reception level is displayed.
[0020]
In a thirteenth technical means according to any one of the first to twelfth technical means, the display unit displays the reception level calculated by the calculation unit on a screen using numerical values and / or graphical elements. It is characterized by that.
[0021]
A fourteenth technical means includes a video display unit for displaying a video in any one of the first to thirteenth technical means, and the display unit is different from the video display unit on the same plane. It is provided at a position.
[0022]
According to a fifteenth technical means, in the fourteenth technical means, the display section is constituted by an LED.
[0023]
The sixteenth technical means is a digital broadcast reception having a memory storing in advance a bit error rate (BER value) indicating how much transmission error has occurred in a received signal and a conversion formula for converting a C / N value into a reception level. In a reception level display method for displaying a reception level using an apparatus, a frequency selection step of selecting a signal of a desired frequency from a digital broadcast signal input from an antenna, and a demodulation step of demodulating the selected reception signal BER measurement step for measuring the BER value of the demodulated reception signal, C / N measurement step for measuring the C / N value of the demodulated reception signal, and corresponding to the measured BER value or C / N value A calculation step for obtaining a conversion formula from the memory and calculating a reception level of the reception signal; and a display step for displaying the calculated reception level. It is obtained by said.
[0024]
In a seventeenth technical means, in the sixteenth technical means, when the reception level is displayed, the measurement range measured in the C / N measurement step can be measured and the BER value measured in the BER measurement step can be measured. It is divided into a range and a range other than that. In the measurable range of the BER value, the BER value or the C / N value is converted into a reception level and displayed, and in the other range, the C / N value is set as the reception level. It is characterized in that it is converted and displayed.
[0025]
In the eighteenth technical means, in the sixteenth or seventeenth technical means, when the reception level is displayed based on the BER value, the BER value is received during the period in which the BER value can be measured in the BER measurement step. In the period when the BER value cannot be measured, the C / N value is converted into a reception level and displayed.
[0026]
In a nineteenth technical means, in any one of the sixteenth to eighteenth technical means, when the reception level is displayed based on the BER value, the modulation system and coding rate of the received signal are detected, and the modulation system is detected. In addition, a conversion formula corresponding to a coding rate is selected from the memory, a reception level of the reception signal is calculated, and the calculated reception level is displayed as an absolute reception level.
[0027]
The twentieth technical means detects the modulation method and the coding rate of the received signal when displaying the reception level based on the C / N value in any one of the sixteenth to eighteenth technical means, A conversion formula corresponding to a modulation method and a coding rate is selected from the memory, a reception level of the reception signal is calculated, and the calculated reception level is displayed as a relative reception level.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram for explaining an internal configuration example of a digital broadcast receiving apparatus according to an embodiment of the present invention. In the figure, 10 is a digital broadcast receiving apparatus, and the digital broadcast receiving apparatus 10 is an antenna 11, A tuner 12, a demodulator 13, a reception state display generator 14, a display 15, a memory 16, a CPU 17, a system bus 18, an input device controller 19, and a remote controller 20 are included. The antenna 11 and the remote controller 20 are connected from the outside of the digital broadcast receiving apparatus 10 via wired or wireless.
[0029]
In FIG. 1, an RF signal of a broadcast wave received by an antenna 11 is input to a tuner 12. The tuner 12 selects a desired reception frequency band based on the received RF signal and outputs it as an intermediate frequency signal (IF signal). The tuner 12 amplifies the received signal with a built-in amplifier and outputs the amplified signal. Next, the IF signal output of the tuner 12 is input to the demodulator 13. The demodulator 13 performs demodulation and error correction in accordance with the modulation scheme modulated on the broadcast distribution side. A CPU (Central Processing Unit) 17 controls the entire system. The memory 16 stores information such as a program or data (conversion formula) for converting a BER value and a C / N value into a reception level. The reception state display generation unit 14 displays the reception state (reception level) on the display unit 15. The display unit 15 displays video, reception level, and the like. Each part can be accessed via the system bus 18. The input device control unit 19 controls input devices such as the remote controller 20. The remote controller 20 selects a channel or selects a menu screen.
[0030]
FIG. 2 is a block diagram showing an example of the internal configuration of the demodulator 13 shown in FIG. 1. When the demodulator 13 is roughly classified, the demodulator 13a and TMCC (Transmission and Multiplexing Configuration Control) that perform demodulation are decoded. A TMCC decoding unit 13b, a waveform equalizing unit 13c, an error correcting unit 13d that performs error correction, a BER measuring unit 13e that measures BER, and a C / N measuring unit 13f that calculates a C / N value from constellation dispersion and the like Is done. Note that the reflection amount measurement unit 13g and the analog signal interference level detection unit 13h indicated by dotted lines in the drawing are described in detail in other embodiments described later, and are not included in the configuration of this embodiment.
[0031]
The present embodiment will be described based on the following flowchart with a case of receiving terrestrial digital broadcasting as a representative example.
FIG. 3 is a flowchart for explaining an example of a reception level display method by the digital broadcast receiving apparatus 10 shown in FIGS. 1 and 2.
In order to display the reception level, it is necessary to perform a channel selection operation on the digital broadcast receiving apparatus 10. First, a frequency to be received is set for the tuner 12 (step S1). By setting the frequency to the PLL of the tuner 12 from the CPU 17, the tuner 12 performs a channel selection operation to the designated frequency. When the tuning operation is completed, the tuner 12 converts the selected RF frequency into an IF signal and inputs the IF signal to the demodulation unit 13. Next, the CPU 17 transmits a command for starting a demodulating operation to the demodulator 13 and starts the demodulating operation of the digital signal (step S2). The CPU 17 repeatedly confirms completion of TMCC decoding by the demodulator 13 (step S3).
[0032]
That is, in step S3, it is determined whether TMCC is acquired. If TMCC is not acquired (NO in step S3), TMCC acquisition confirmation is repeatedly performed, and completion of TMCC decoding is confirmed (in step S3). In the case of YES), the modulation method is read from the demodulator 13 (step S4). The TMCC decoding unit 13b of the demodulating unit 13 decodes TMCC information including information on the modulation scheme and coding rate of the received signal. The TMCC information can acquire the modulation scheme and coding rate of the received signal. .
[0033]
After confirming the completion of the TMCC decoding, the demodulator 13 stores the decoded TMCC information in a register, and the CPU 17 can confirm the TMCC information by accessing the register. Next, it is confirmed whether the modulation method is, for example, 64QAM (step S5). When the modulation method is not 64QAM (in the case of NO), the reception level is calculated using C / N (step S10). In this embodiment, a method of displaying the reception level using BER only in the case of 64QAM is shown. However, in other modulation systems, a conversion formula for the modulation system is provided in the memory 16. The reception level can be displayed using BER.
[0034]
In addition, as a method of calculating the reception level using C / N, for example, the C / N measurement unit 13f receives the normal coordinates and the received signal in the pilot signal (SP) whose constellation coordinates are known in advance. There is a method of obtaining by dispersion with the coordinates of. According to this method, since the pilot signal is transmitted by a fixed modulation method, the C / N value for the received signal can be obtained regardless of the modulation method of the data part signal. The conversion formula for converting the C / N value to the reception level is obtained by measuring the C / N measurement value of the demodulator 13 for C / N in advance and converting the C / N value into the reception level in the memory 16. In the case of conversion, calculation is performed based on the conversion formula.
[0035]
If the modulation method is 64QAM in step S5 (YES), the BER value is read from the demodulator 13 (step S6). Here, the method for measuring the BER value includes, for example, a method of calculating the number of errors by re-encoding the data signal after Viterbi decoding and comparing the data, and a method of counting the number of errors after Reed-Solomon. is there.
[0036]
In the present embodiment, the former method described above, that is, the case of the demodulation unit 13 having a BER measurement function after Viterbi decoding will be described as a representative example.
It is compared whether the BER value after Viterbi read in step S6 is smaller than 1.0 × E-6 (step S7). If the BER value is smaller than 1.0 × E-6 (YES) ), The reception level is calculated using the C / N value (step S10). Further, when the BER value is 1.0 × E-6 or more in the above step S7 (in the case of NO), the process proceeds to step S8 to compare whether the BER value is 1.0 × E-2 or more. (Step S8). When the BER value is 1.0 × E−2 or more (in the case of YES), the reception level is similarly calculated using the C / N value (step S10). Further, when the BER value is 1.0 × E−2 or less in the above step S8 (in the case of NO), the reception level is calculated using the BER value (step S9). Finally, the calculated reception level is displayed on the display unit 15 (step S11).
[0037]
FIG. 4 is a diagram illustrating the relationship of the reception level with respect to the reception C / N when converting C / N and BER into the reception level. As described above, in the C / N value, at the reception level in the center range, the result measured with the BER value is converted into the reception level, and in the other ranges, the reception level is displayed using the C / N value. I am doing so.
[0038]
A method for calculating the reception level from the BER will be described below.
FIG. 5 is a diagram showing an example of the BER characteristic with respect to C / N, in which 31 is a characteristic graph of 64QAM3 / 4, and 32 is a characteristic graph of 64QAM7 / 8. As described above, in the digital broadcast receiving apparatus 10, the BER for C / N is measured in advance, and the result is stored in the memory 16. As a specific example, when the BER is, for example, 1.0 × E-6, a reception level 60 is displayed, and when the BER is 1.0 × E-2, a conversion formula is created so that the reception level is 20. The conversion formula is stored in the memory 16. In this way, a conversion formula for converting the BER to the reception level is created, and when the reception level is displayed, the conversion formula is used to convert the BER to the reception level for display. In FIG. 5, when the BER is 1.0 × E-6, the C / N is 25. When the C / N is 25, the reception level 60 is displayed and the BER is 1.0 × E−. Since the C / N at 20 is 20, when the C / N is 20, the reception level 20 is displayed.
[0039]
A method for calculating the reception level from C / N will be described below.
In this case, the relationship of the C / N measurement value with respect to the C / N of the digital broadcast receiving apparatus 10 is measured in advance. Based on the value, a conversion formula is created so as to be a graph shown in the portion calculated by the C / N value as shown in FIG. In this case, for example, when the actual C / N is 20 dB and the C / N measurement value is 19 dB, the calculation is performed with correction such as adding 1 to the C / N measurement value. When the reception C / N is 0, the reception level 0 is displayed. When the reception C / N 20 is received, the reception level 20 is displayed. When the reception C / N 25 is reception, the reception level 60 is displayed. When the reception C / N 40 is reception, the reception level 20 is displayed. A conversion formula that displays level 100 is created.
[0040]
According to the present invention, when the BER can be measured, the reception level can be displayed using the BER. Therefore, the reception state can be displayed more accurately than the display method using only C / N or AGC. it can.
In the BER measurable range, the display can be switched to the BER and the reception state can be displayed using C / N even outside the BER measurement range.
[0041]
FIG. 6 is a diagram illustrating an example of a display form of the reception level. As shown in FIG. 6 (A), the reception level is displayed in a form using numerical values and bar graphs of the reception level, and as shown in FIG. 6 (B), the horizontal axis represents frequency and the vertical axis represents reception level. As shown in Fig. 6 (C), various graphs are assumed, such as a line graph with time on the horizontal axis and reception level on the vertical axis. Any display form may be used.
[0042]
In the above example, the modulation scheme is 64QAM and the coding rate is 7/8. A reception level display method in the case of different modulation schemes and coding rates will be described below. In this example, the case where the modulation scheme is 64QAM and the coding rate is 3/4 will be described as a representative example.
In this case, the BER characteristic with respect to C / N is measured in advance as shown in FIG. 5 as in the case of the above-described 64QAM7 / 8. In the case of 64QAM3 / 4, reception is possible even if the C / N value is small compared to 64QAM7 / 8. In the case of 64QAM3 / 4, the same conversion formula as in the case of 64QAM7 / 8 is used. When BER is 1.0 × E-6, reception level 60 is displayed and BER is 1.0 × E-2. Sometimes, the reception level 20 is displayed.
[0043]
FIG. 7 is a diagram illustrating an example of the relationship of the reception level with respect to the reception C / N depending on the difference in modulation scheme and coding rate, in which 33 is a characteristic graph of 64QAM3 / 4, and 34 is a characteristic graph of 64QAM7 / 8. is there. As shown in FIG. 5 described above, when the BER of the characteristic graph 31 (64QAM3 / 4) is 1.0 × E-6, the C / N is 23. Therefore, when the C / N is 23, The reception level 60 is displayed. Since the C / N is 18 when the BER is 1.0 × E-2, the reception level 20 is displayed when the C / N is 18. In this method, as shown in FIG. 7, the characteristic graph to be displayed changes between 64QAM7 / 8 and 64QAM3 / 4. In this case, for example, when the received C / N is 23 dB, the reception level is 55 when the coding rate is 7/8, but the reception level 60 is displayed when the coding rate is 3/4. Is done.
[0044]
FIG. 8 is a diagram showing an example of the relationship of the reception level with respect to the reception C / N when correction is made to the BER conversion equation due to the difference in modulation scheme and coding rate, in which 35 is a characteristic graph of 64QAM3 / 4 , 36 is a characteristic graph of 64QAM7 / 8. In this way, by correcting and displaying the reception level of the characteristic graph 33 (64QAM3 / 4) shown in FIG. 7, the same reception level as that of 64QAM7 / 8 can be displayed.
As the correction method, for example, there is a method of displaying by subtracting a certain numerical value. Referring to FIG. 8, the reception level 60 calculated by the characteristic graph 35 (64QAM3 / 4) is set to a reception level 55 that is a value corresponding to C / N23 of the characteristic graph 36 (64QAM7 / 8). Subtract 5 to display the reception level. As in the case of 64QAM7 / 8, locations outside the measurement range of 64QAM3 / 4 BER are displayed as C / N values.
[0045]
In the above correction method, the conversion formula for BER is corrected according to the modulation method and coding rate, but there is a method in which correction is not performed. That is, even if the modulation method is changed, the reception level 60 is displayed when the BER is 1.0 × E-6, and the reception level 20 is displayed when the BER is 1.0 × E-2. It is a method. According to such a display method, it is possible to display a reception state corresponding to the modulation method. In the case of this display method, when the same conversion formula is used for the part displayed in C / N as in 64QAM7 / 8, the part displayed in BER and the part displayed in C / N as shown in FIG. It becomes discontinuous between the parts. Therefore, the conversion formula for converting C / N into a reception level is changed according to the modulation scheme and coding rate.
[0046]
FIG. 9 is a diagram showing an example of the relationship of the reception level to the reception C / N when the C / N conversion formula is corrected due to the difference in modulation scheme and coding rate. In the figure, 37 is the 64QAM3 / 4. A characteristic graph 38 is a characteristic graph of 64QAM7 / 8. Thus, when the coding rate is the characteristic graph 38 (64QAM7 / 8), 20 is displayed as the reception level when the C / N is 20, but when the C / N is 18, Create a conversion formula that displays and use it. The result is a characteristic graph 37 (64QAM3 / 4). Similarly, when the coding rate is the characteristic graph 38 (64QAM7 / 8), the location where the reception level is 60 is displayed as 60 when the C / N is 25. A conversion formula for displaying 60 when C / N is 23 is created and used. The result is a characteristic graph 37 (64QAM3 / 4).
[0047]
According to the present invention, when the reception level is displayed using the BER, the conversion formula is automatically changed according to the modulation scheme and coding rate, so that the reception level does not differ for each modulation scheme in the same received signal.
Further, since the switching point between the BER measurement and the C / N is continuously displayed, the reception level can be smoothly displayed even at the switching point between the BER and the C / N display. Further, since the BER conversion formula is not changed depending on the modulation method, it is possible to display a level corresponding to the error tolerance of the modulation method.
[0048]
Here, when the time until the demodulator 13 can measure the BER and the C / N after the channel selection operation is compared, the time until the BER becomes measurable compared to the C / N. Cost. In the case of BER, it is necessary to wait until the frame synchronization of TMCC is completed, and a certain measurement period is required to measure the number of errors of a certain number of bits. In the case of C / N, even if the frame synchronization of TMCC is not completed, the calculation can be performed based on the pilot signal carrier included in the signal, so that measurement can be performed earlier than the BER.
[0049]
FIG. 10 is a flowchart for explaining another example of the reception level display method by the digital broadcast receiver 10 shown in FIGS. 1 and 2. First, a frequency is set in the tuner 12 (step S21). Next, the demodulating unit 13 starts demodulating operation (step S22). Next, the demodulator 13 determines whether or not C / N measurement is possible (step S23), and when C / N measurement is impossible (in the case of NO), “0” is returned as the reception level. (Step S24). If C / N measurement is possible in step S23 (YES), it is determined whether BER measurement is possible (step S25). If BER measurement is impossible (NO). The reception level is calculated using only C / N (step S26). If the BER can be measured in step S25 (YES), the reception level is calculated using C / N and BER (step S27).
[0050]
As for the conversion formula when calculating the reception level using only C / N, the display range using BER is also displayed in C / N (that is, all C / N). In FIG. 4 described above, according to the above display method, BER was used when C / N was in the range of 20 to 25, but this range is also displayed with C / N. That is, a conversion formula is created and used to display reception level 20 when C / N is 20, and reception level 60 when C / N is 25.
[0051]
According to the present invention, until the BER can be measured, it is displayed in C / N. Therefore, when the reception level is displayed immediately after channel selection or the like, rather than simply using the BER. The reception level can be displayed quickly.
[0052]
When the reception level is displayed using C / N and BER, if the tuner 12 and the demodulator 13 have variations due to frequency characteristics, the reception level display also varies depending on the frequency.
FIG. 11 is a diagram illustrating an example of BER characteristics with respect to C / N for each frequency. Assuming that the average value of the C / N vs. BER characteristics is a reference value, the frequency is better for the A channel frequency than the reference value, but the B channel is worse than the reference value. In such a case, if the BER is converted to the reception level without correction, the reception level to be displayed varies depending on the frequency. Therefore, when the reception level is displayed, the reception level is corrected and displayed. In this example, the correction amount A is corrected for the A channel, and the correction amount B is corrected for the BER value for the B channel. Here, the digital broadcast receiving apparatus 10 holds data for each frequency of the C / N vs. BER characteristics in advance as a data table.
[0053]
Similarly, when the reception level is displayed using C / N, the C / N value for C / N is measured in advance at each frequency, and when the display is displayed, the difference is corrected. A method is also possible. Here, the digital broadcast receiving apparatus 10 holds data for each frequency of C / N vs. C / N value characteristics in advance as a data table.
[0054]
According to the present invention, since the reception level can be displayed by correcting the frequency characteristics of the tuner, the level of the input signal can be displayed accurately.
[0055]
FIG. 12 is a diagram illustrating an example of a waveform when the received signal has reflection. FIG. 12A shows a signal waveform when there is no reflection, and FIG. 12B shows a signal waveform when there is reflection. FIG. The digital broadcast receiving apparatus 10 of the present embodiment will be described below as a configuration in which the reflection amount measuring unit 13g shown in FIG.
When the reception signal is reflected by a cable or the like, the reception signal is distorted. As shown in FIG. 12A, the waveform has no distortion when there is no reflection, but when there is reflection, the received signal is distorted as shown in FIG. .
[0056]
Here, a specific reflection amount detection method will be described.
The reflection amount measurement unit 13g in the demodulation unit 13 can detect the reflection amount by measuring the signal level at each frequency in the band of the received signal. In the transmission signal, the pilot signal is preliminarily arranged in the signal frequency band, and the transmission path estimation unit (not shown) in the waveform equalization unit 13c of the demodulation unit 13 measures the level of the received pilot signal. By doing so, the reception level of each frequency can be estimated. As shown in FIG. 12, the transmission path estimation unit can detect the amount of reflection by detecting the amplitude of the signal and measuring the variation by the reflection amount measurement unit 13g. When this variation is large, it indicates that the reflected signal is large. The magnitude of this variation is corrected and displayed when displaying the reception level. For example, if the amount of reflection is subtracted from the C / N value, or if reception is impossible when estimated from the amount of reflection even if C / N is good, the reception level is displayed as an unreceivable level. .
[0057]
According to the present invention, since the reflection amount of the signal is detected and the reflection amount is corrected and displayed, it is possible to display the reception level more accurately than the display using only C / N.
[0058]
FIG. 13 is a diagram illustrating an example of a waveform when an interference such as an analog signal is present in the received signal, FIG. 13A illustrates a signal waveform when there is no analog signal interference, and FIG. 13B illustrates an analog signal. It is the figure shown about the signal waveform in the case of interference. The digital broadcast receiving apparatus 10 of the present embodiment will be described below as a configuration in which the analog signal interference level detection unit 13h illustrated in FIG.
If an analog signal is present in the same frequency band as the received signal, this is an interference signal for the digital signal. As shown in FIG. 13A, when there is no interference, the waveform has no distortion. However, when there is interference, an interference signal is added to the received signal as shown in FIG. Waveform.
[0059]
Here, a specific method of detecting the interference level due to analog signal interference will be described.
It can be detected by measuring the signal level of each frequency within the band of the received signal using the propagation characteristic estimated by the transmission path estimation unit (not shown) in the waveform equalization unit 13c. For example, if an OFDM signal is degraded by an analog signal video carrier, interference will appear in the propagation characteristics of the transmission path estimation unit. The analog signal interference level detector 13h can detect the interference signal based on this information. When the reception level is displayed, the magnitude of the interference signal is corrected and displayed. For example, if the amount of interference is subtracted from the C / N value, or if reception is impossible when estimated from the interference amount of an analog signal even if C / N is good, the reception level is displayed as an unreceivable level. To do.
[0060]
According to the present invention, since an interference signal such as an analog signal is detected and the amount of the interference is corrected and displayed, it is possible to display the reception level more accurately than the display using only C / N. Further, since the level of the interference wave such as an analog signal is corrected and displayed, it is possible to display the reception level more accurately than the display using only C / N.
[0061]
When the received signal is a signal that has been subjected to hierarchical modulation including a plurality of modulation schemes, the digital broadcast receiving apparatus 10 selects video and audio of a certain hierarchy. A method for displaying the reception level using the conversion formula corresponding to each selected hierarchy when displaying the reception level will be described below.
For example, the received signal has two modulation levels of 16QAM for the A layer (strong layer) and a coding rate of 1/2, and a modulation method of 64QAM for the B layer (weak layer) and a coding rate of 3/4. Assume that the hierarchy is mixed. The weak layer generally contains high-quality video, but the resistance to C / N is weak, and the strong layer is inferior in image quality, but has high resistance to C / N and can be received even at low C / N. . The demodulator 13 has a function of measuring the BER for each modulation scheme and coding rate. When the digital broadcast receiving apparatus 10 is displaying a video of a weak hierarchy, the digital broadcast receiving apparatus 10 uses a conversion formula using BER when a signal with a modulation method of 64QAM and a coding rate of 3/4 is decoded, and is strong. When a hierarchical video is displayed, the reception level is displayed using a conversion formula using BER when a signal with a modulation method of 16QAM and a coding rate of 1/2 is decoded.
[0062]
It is determined by the CPU 17 whether a high-level video or a low-level video is selected. Since the service ID number of the strong hierarchy is determined in advance, the CPU 17 can specify the hierarchy by determining which service ID included in the transport stream output from the demodulator 13 is selected. is there. In a certain signal state, there is a state where reception is not possible in the weak layer but reception is possible in the strong layer. In this case, when the weak layer is selected, the reception level is displayed low, and when the strong layer is selected, the reception level is displayed as a receivable level.
[0063]
For example, when viewing the strong layer, if the reception level deteriorates and the weak layer cannot be viewed, the reception level is an unreceivable value if the reception level of the weak layer is displayed. However, it is displayed as a receivable level by switching to the reception level of the strong hierarchy being viewed.
[0064]
According to the present invention, since the BER of the modulation method corresponding to the selected hierarchy is used for display, the reception level corresponding to the modulation method of the program being viewed can be displayed.
[0065]
In the above example, the level of reception to be displayed is displayed for the level selected by the CPU 17, but may be selected by the user.
FIG. 14 is a diagram illustrating an example of a menu screen for selecting a hierarchy for displaying the reception level. A screen as shown in FIG. 14 is displayed, and a hierarchy can be selected by an input device such as the remote controller 20. When “automatic selection” is selected, the hierarchy is selected and displayed by the CPU 17 by the method described above. When “weak layer” is selected, the BER of the weak layer is always read and the reception level is displayed. In this case, the reception level of the weak hierarchy is displayed even if the strong hierarchy is selected as the video. When “strong hierarchy” is selected, contrary to the above, the BER of the strong hierarchy is always read and the reception level is displayed. Similarly, even if the weak layer is selected as the video, the reception level of the strong layer is displayed.
[0066]
According to the present invention, the user can freely select and view the reception level of the weak layer and the reception level of the strong layer. For example, even when a strong layer video is being viewed, whether or not the weak layer can be received can be confirmed without switching to the weak layer program. Thereby, after the weak hierarchy becomes receivable, it is possible to use such as switching the program to the weak hierarchy.
[0067]
When the reception level is displayed, for example, as shown in FIG. 6A, the numerical value and the reception level are displayed by a bar graph. The numerical value and bar graph display are updated at regular intervals.
[0068]
For the display method, calculate the average of the measured level several times and update the value at regular intervals, or select the worst value among the measured levels at regular intervals. There are ways to update it. The average method has an advantage that the display becomes easy to see when the update interval is short. In the method of displaying the worst value, when the reception level fluctuates greatly, the worst value is displayed, so that it is easy to detect a level that deteriorates instantaneously.
[0069]
Further, the state of signal reflection and the state of interference by analog signals may be displayed. As shown in FIG. 6A, when the reflection amount measurement unit 13g detects a large reflection amount, “strong” indicating that the reflection amount level (multipath level) is large is displayed. When the analog signal interference level detection unit 13h detects that the interference signal level is low due to an analog signal or the like, “weak” indicating that the interference signal level is low is displayed.
[0070]
Further, as shown in FIG. 6B, it is also possible to use a graph format in which the horizontal axis represents frequency and the vertical axis represents reception level. When displaying the reception level, it is also possible to start searching for each frequency and display the reception level of each frequency channel. It is also possible to store the reception level of each frequency in the memory 16 and simultaneously display the reception level of the current frequency and the stored reception level of other frequencies when displaying the reception level. It is.
[0071]
Further, as shown in FIG. 6C, the graph can be displayed in a format in which the horizontal axis indicates the time and the vertical axis indicates the reception level, and the time course of the reception level can be understood. is there. As a display method, after switching to a screen that displays the reception level, the reception level is measured at regular intervals and displayed sequentially, or the reception level is stored in the memory 16 at regular intervals. When displaying the reception level, it is also possible to display the reception level of the channel including the past reception level.
[0072]
According to the present invention, the strength of the reflection amount and the strength of the analog signal interference can be displayed simultaneously with the reception level, so the reception state is poor due to the large multipath, or the analog signal It is possible to know the cause of deterioration such as bad reception due to large interference. In addition, since a change in reception level can be displayed, it is possible to determine how much the reception signal is changing, whether the reception state tends to deteriorate, or whether the reception state tends to be good. In addition, since a list of reception levels at each frequency can be displayed, the reception status of each channel can be confirmed at a glance.
[0073]
FIG. 15 is a diagram illustrating a display example of the reception level of each layer. When displaying the reception level, the reception level of the weak layer and the reception level of the strong layer can be displayed at the same time. The demodulator 13 measures the BER for each of the weak layer and the strong layer at the same time. When displaying the reception level, the BER of the weak layer and the BER of the strong layer are read out. Display the reception level on the screen.
[0074]
According to the present invention, since the reception status of each layer can be displayed at the same time, the reception status of each layer can be confirmed at a glance.
[0075]
For the reception level display mode, an absolute reception level display mode that changes the conversion formula for converting from BER to the reception level according to the modulation method and coding rate, and conversion from C / N to the reception level according to the modulation method and coding rate. There is a relative reception level display mode in which the conversion formula to be changed is changed, but this mode may be switched and displayed.
FIG. 16 is a diagram illustrating an example of a menu screen for selecting a reception level display mode. A screen as shown in FIG. 16 is displayed so that each display mode can be selected by an input device such as the remote controller 20. When “Absolute reception level mode” is selected, the reception level is displayed in the absolute reception level display mode. When “Relative reception level mode” is selected, the reception level is displayed in the relative reception level display mode. Display the reception level.
[0076]
According to the present invention, since the user can freely switch between the absolute reception level display mode and the relative reception level display mode, it is possible to display according to the use conditions and preferences of the user. For example, when it is desired to display the reception level proportional to the reception C / N, the absolute reception level display mode is set. When it is desired to determine whether or not the currently received modulation method is receivable, the relative reception level display is performed. Can be used to switch to a mode.
[0077]
FIG. 17 is a diagram showing an example of a display state in which a reception level is displayed on a video display device incorporating a digital broadcast receiving device. In FIG. 17, reference numeral 40 denotes a video display device, and the video display device 40 includes a video display unit. 41. A display 42 for receiving level and the like is provided. FIG. 18 is a diagram showing another example of the state in which the reception level is displayed on the video display device incorporating the digital broadcast receiving device. In the figure, 50 is the video display device, and the video display device 50 is A video display unit 51 and an LED display unit 52 are provided. The video display device shown in FIGS. 17 and 18 has the digital broadcast receiving device 10 of the present invention built in or outside, and can receive the digital broadcast and display the video on the video display unit.
[0078]
In FIG. 17, when the position where the reception level is displayed is displayed on the video display unit 41 that displays the video, the video becomes difficult to see. Therefore, the display unit 42 that displays information other than the video, separately from the screen that displays the video. The reception level is displayed in this part. As a display method, for example, there are a display method such as a numeric display, a bar graph display, a level meter using an analog needle, or the like.
[0079]
Moreover, as shown in FIG. 18, it is good also as a display form which displays a reception level on the LED display part 52. FIG. Further, it is possible to display by changing the color of the LED according to the reception level. For example, if the reception status is not possible to receive at all, it will not be lit. If it is near the reception level where reception is not possible, red will be displayed. If reception is possible, green will be displayed. There is a method of displaying the blue color and gradually changing the color at the reception level in the meantime.
[0080]
According to the present invention, since the reception level is displayed on a screen other than the screen for displaying the video, the reception level can be displayed without disturbing the video being viewed. Further, by displaying using the LED, it is possible to grasp the approximate reception level without taking up a display area.
[0081]
【The invention's effect】
According to the present invention, when the BER can be measured, the reception level is displayed based on the BER, and in other cases, the reception level is displayed based on the C / N, thereby displaying the accurate reception state. Can do.
[Brief description of the drawings]
FIG. 1 is a block diagram for explaining an internal configuration example of a digital broadcast receiving apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram showing an example of an internal configuration of a demodulator shown in FIG.
FIG. 3 is a flowchart for explaining an example of a reception level display method by the digital broadcast receiving apparatus shown in FIGS. 1 and 2;
FIG. 4 is a diagram illustrating a relationship of reception level with respect to reception C / N when C / N and BER are converted into reception levels.
FIG. 5 is a diagram illustrating an example of BER characteristics with respect to C / N.
FIG. 6 is a diagram illustrating an example of a display form of a reception level.
FIG. 7 is a diagram illustrating an example of a relationship between a reception level and a reception C / N depending on a difference in modulation scheme and coding rate.
FIG. 8 is a diagram illustrating an example of a relationship of a reception level with respect to a reception C / N when a BER conversion equation is corrected depending on a difference in modulation scheme and coding rate.
FIG. 9 is a diagram illustrating an example of a relationship of a reception level with respect to a reception C / N when correction is made to a C / N conversion formula due to a difference in modulation scheme and coding rate.
FIG. 10 is a flowchart for explaining another example of the reception level display method by the digital broadcast receiver shown in FIGS. 1 and 2;
FIG. 11 is a diagram illustrating an example of a BER characteristic with respect to C / N for each frequency.
FIG. 12 is a diagram illustrating an example of a waveform when a reception signal has reflection.
FIG. 13 is a diagram illustrating an example of a waveform in a case where an interference such as an analog signal is present in a received signal.
FIG. 14 is a diagram showing an example of a menu screen for selecting a hierarchy for displaying a reception level.
FIG. 15 is a diagram illustrating a display example of a reception level of each layer.
FIG. 16 is a diagram illustrating an example of a menu screen for selecting a reception level display mode;
FIG. 17 is a diagram illustrating an example of a display state in which a reception level is displayed on a video display device incorporating a digital broadcast receiving device.
FIG. 18 is a diagram illustrating another example of a state in which a reception level is displayed on a video display device incorporating a digital broadcast receiving device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Digital broadcast receiver, 11 ... Antenna, 12 ... Tuner, 13 ... Demodulation part, 14 ... Reception status display generation part, 15 ... Display part, 16 ... Memory, 17 ... CPU, 18 ... System bus, 19 ... Input equipment Control unit, 20 ... remote control, 13a ... demodulation circuit, 13b ... TMCC decoding unit, 13c ... waveform equalization unit, 13d ... error correction unit, 13e ... BER measurement unit, 13f ... C / N measurement unit, 13g ... reflection amount measurement 13h: Analog signal interference level detection unit 31, 32, 33, 34, 35, 36, 37, 38 ... Characteristic graph, 40, 50 ... Video display device, 41, 51 ... Video display unit, 42 ... Reception level Etc., 52 ... LED display part.

Claims (20)

A tuner unit that selects a signal of a desired frequency from a digital broadcast signal input from an antenna, a demodulator unit that demodulates the selected received signal, and a bit that indicates how much transmission error has occurred in the demodulated received signal A BER measuring unit for measuring an error rate (BER value), a C / N measuring unit for measuring a C / N value of the demodulated reception signal, and a conversion for converting the BER value and the C / N value into a reception level. A memory that stores an equation, a calculation unit that calculates a conversion equation corresponding to the measured BER value or C / N value from the memory and calculates the reception level of the received signal, and a display that displays the calculated reception level And a digital broadcast receiving apparatus. 2. The digital broadcast receiver according to claim 1, wherein when the reception level is displayed, the measurement range by the C / N measurement unit is changed to a measurable range of the BER value by the BER measurement unit and other ranges. Dividing and displaying the BER value or C / N value converted to the reception level in the measurable range of the BER value, and converting the C / N value to the reception level for display in other ranges. A digital broadcast receiver characterized by the above. 3. The digital broadcast receiver according to claim 1, wherein when the reception level is displayed based on the BER value, the BER value is converted into the reception level in a period in which the BER measurement unit can measure the BER value. A digital broadcast receiving apparatus, wherein the C / N value is converted into a reception level and displayed during a period in which the BER value cannot be measured. 4. The digital broadcast receiver according to claim 1, wherein when the reception level is displayed based on the BER value, the modulation method and coding rate of the received signal are detected, and the modulation method and coding are detected. A digital broadcast receiving apparatus, wherein a conversion formula corresponding to a rate is selected from the memory, a reception level of the reception signal is calculated, and the calculated reception level is displayed as an absolute reception level. 4. The digital broadcast receiver according to claim 1, wherein when a reception level is displayed based on a C / N value, a modulation scheme and a coding rate of a received signal are detected, and the modulation scheme and A digital broadcast receiving apparatus, wherein a conversion formula corresponding to a coding rate is selected from the memory, a reception level of the received signal is calculated, and the calculated reception level is displayed as a relative reception level. In the digital broadcast receiving apparatus according to any one of claims 1 to 5, the digital broadcast receiving apparatus has a data table storing information on a frequency characteristic of a BER value with respect to a C / N value for each frequency, and when displaying a reception level, Digital broadcast reception characterized in that a reception level is displayed by referring to a data table corresponding to the frequency selected by the tuner and correcting a change amount of the frequency with respect to the frequency characteristic based on the data table. apparatus. 2. The digital broadcast receiving apparatus according to claim 1, wherein the demodulation unit includes a reflection amount measurement unit that measures a reflection amount of a received signal, and stores a C / C stored in the memory in accordance with the measured reflection amount. A digital broadcast receiving apparatus which corrects a conversion formula for converting an N value into a reception level. 2. The digital broadcast receiving apparatus according to claim 1, wherein the demodulating unit includes a disturbance level detecting unit that detects a disturbance level due to an analog signal within a band of the received digital signal, and the interference level due to the detected analog signal. According to the digital broadcast receiving apparatus, the conversion formula stored in the memory for converting the C / N value into the reception level is corrected. 9. The digital broadcast receiver according to claim 1, wherein when a reception level is displayed, a modulation method and a coding rate according to a hierarchy of a received signal being viewed are detected and the modulation is performed. A digital broadcast receiving apparatus, wherein a conversion formula corresponding to a system and a coding rate is selected from the memory, a reception level of the reception signal is calculated, and the calculated reception level is displayed. 9. The digital broadcast receiving apparatus according to claim 1, wherein when the reception level is displayed, the modulation scheme and the coding rate are detected for each layer included in the received signal, and the modulation scheme and code are detected. A digital broadcast receiving apparatus, wherein a conversion formula corresponding to a conversion rate is selected from the memory, a reception level of a received signal is calculated for each layer, and the calculated reception level can be displayed for each layer. The digital broadcast receiver according to any one of claims 1 to 8, wherein the display unit includes a layer selection unit that selects a layer on which a reception level is displayed on a screen, and corresponds to the selected layer. Detecting a modulation method and a coding rate, selecting a conversion equation corresponding to the modulation method and a coding rate from the memory, calculating a reception level of the received signal, and displaying the calculated reception level A digital broadcast receiver. 10. The digital broadcast receiving apparatus according to claim 4, wherein the display unit includes a reception level selection unit that selects a display method of either the absolute reception level or the relative reception level on a screen. And detecting a modulation method and a coding rate according to the hierarchy of the received signal being viewed, and selecting a conversion formula according to the display method selected by the reception level selection unit from the memory A digital broadcast receiving apparatus that calculates a reception level of a signal and displays the calculated reception level. 13. The digital broadcast receiving apparatus according to claim 1, wherein the display unit displays the reception level calculated by the calculation unit on a screen using numerical values and / or graphical elements. A digital broadcast receiver characterized by the above. 14. The digital broadcast receiver according to claim 1, further comprising a video display unit for displaying video, wherein the display unit is provided at a position different from the video display unit on the same plane. A digital broadcast receiver characterized by the above. 15. The digital broadcast receiving apparatus according to claim 14, wherein the display unit is configured by an LED. The reception level is set using a digital broadcast receiver having a memory that stores in advance a bit error rate (BER value) indicating how much transmission error has occurred in the received signal and a conversion formula for converting the C / N value into the reception level. In the reception level display method for display, a frequency selection step of selecting a signal of a desired frequency from a digital broadcast signal input from an antenna, a demodulation step of demodulating the selected reception signal, and a demodulated reception signal A BER measurement step for measuring a BER value, a C / N measurement step for measuring a C / N value of the demodulated received signal, and a conversion formula corresponding to the measured BER value or C / N value are obtained from the memory. And a display step for displaying the calculated reception level. Level display method. 17. The reception level display method according to claim 16, wherein when the reception level is displayed, a measurement range measured in the C / N measurement step is a measurable range of a BER value measured in the BER measurement step. The BER value or the C / N value is converted into a reception level for display in the measurable range of the BER value, and the C / N value is converted into a reception level in the other range. A reception level display method characterized by being displayed. The reception level display method according to claim 16 or 17, wherein when the reception level is displayed based on the BER value, the BER value is converted into the reception level in a period during which the BER value can be measured in the BER measurement step. The reception level display method characterized in that the C / N value is converted into a reception level and displayed during a period in which the BER value cannot be measured. 19. The reception level display method according to claim 16, wherein when a reception level is displayed based on a BER value, a modulation scheme and a coding rate of a received signal are detected, and the modulation scheme and encoding are detected. A reception level display method, comprising: selecting a conversion formula corresponding to a rate from the memory to calculate a reception level of the reception signal, and displaying the calculated reception level as an absolute reception level. The reception level display method according to any one of claims 16 to 18, wherein when the reception level is displayed based on the C / N value, a modulation method and a coding rate of the received signal are detected, and the modulation method and A reception level display method comprising: selecting a conversion formula corresponding to a coding rate from the memory, calculating a reception level of the reception signal, and displaying the calculated reception level as a relative reception level.

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