• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    PURPOSE: To set an optimum radio frequency automatic gain control(RF AGC) point to a digital television signal of a terrestrial wave and a digital television signal of a cable television(CATV). CONSTITUTION: A changeover switch 22 is switched depending on whether an input signal is a digital television signal of a terrestrial wave or a digital television signal of a CATV, and the voltage of an RF AGC point is set to a reference voltage V1 of a reference power supply 21a in the case of the digital television signal of a terrestrial wave, and set to a reference voltage V2 of a reference power supply 21b in the case of the digital television signal of a CATV. A comparator 23 outputs an RF AGC signal corresponding to the difference between an IF AGC signal and a reference voltage.
    公开号:KR20010006770A
    申请号:KR1020000011984
    申请日:2000-03-10
    公开日:2001-01-26
    发明作者:오야고이치
    申请人:이데이 노부유끼；소니 가부시끼 가이샤；
    IPC主号:
    专利说明:

    Apparatus and method for receiving a digital signal, and providing medium
    BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for receiving digital television signals, and in particular, sets AGC (Automatic Gain Contro1) points of terrestrial digital television signals and CATV (Cable Te1evision) digital television signals individually, and types of digital television signals to be input. The present invention relates to a digital television signal receiving apparatus which is capable of setting an optimal AGC point by switching AGC points correspondingly.
    In recent years, digital television signal receiving apparatuses have become popular. The tuner of the digital television signal receiving apparatus is provided with an AGC circuit which detects a change in the amplitude of the input signal and keeps the amplitude of the output signal constant.
    The AGC circuit of the digital television signal receiving apparatus includes two types of AGC circuits, one of which is an AGC circuit for RF (Radio Frequency) and the other of which is an AGC circuit for IF (Intermediate Frequency). In the RF AGC circuit, the gain of the RF signal received from the antenna is controlled, and in the IF AGC circuit, the gain of the IF signal converted from the RF signal is controlled.
    Normally, after the AGC for IF is caught in advance, the AGC for RF is applied at the point where the input level of the tuner is constant. This makes it easy to obtain an image with good signal to noise ratio (S / N) or carrier to noise ratio (C / N) at the maximum sensitivity of the tuner for the IF signal, and then adjust the gain of the tuner for the RF signal. This is to suppress and prevent intermodulation distortion or the like.
    1 shows a circuit diagram for controlling a conventional RF AGC point. A reference voltage V0 output by the reference power supply 2 is input to the inverting input terminal of the comparator 1 of FIG. 1, and an IF AGC signal is input to a non-inverting input terminal from a circuit (not shown) of a later stage. .
    The comparator 1 compares the IF AGC signal input to the non-inverting input terminal with the reference voltage V0 input from the reference power supply 2 to the inverting input terminal, and as shown in FIG. When the voltage is larger than the reference voltage V0, the RF AGC signal is output at a constant high level. When the voltage is smaller than the reference voltage V0, the RF AGC signal is gradually outputted.
    The tuner, not shown, is obtained when the output voltage of the RF AGC signal output from the comparator 1 is lowered, so that an IF signal of a sufficient magnitude is obtained in a circuit not shown in the latter stage, and thus the control of the level of the output RF signal is controlled. It starts. That is, when the voltage of this IF AGC signal is the reference voltage V0, it becomes an AGC point (a point which applies RF AGC).
    However, in general, the level of the terrestrial disturbance signal may be higher than the desired signal level, but the noise level is low and is about the thermal noise level. In contrast, the level of the disturbance signal of CATV is not so high, but the noise level is higher than the thermal noise level.
    For example, when the bandwidth is 6 MHz, the thermal noise level is -106 dBm, the tuner's NF (Noise Figure) is 7 dB, and the required C / N at the tuner's output is 25 dB. The AGC (RF AGC) point of the tuner when receiving is calculated as shown in equation (1). On the other hand, S / N and C / N are referred to as ratios of input signal levels and noise from terrestrial waves and CATV, respectively, and are treated equally in the calculation.
    -106 + 7 + 25 = -74 dBm (1)
    Next, when the tuner receives the CATV RF signal at the same AGC point setting, for example, if the input RF signal level is -55 dBm and the C / N at that time is 27 dB, the noise level is-. 82 (= -55-27) dBm. This input RF signal level is lower than the -74 dBm of the AGC point represented by the above equation (1), so that the level of the input signal is lowered, which is a gain of 19 (= -55-(-74). It takes AGC of dB). However, since the same AGC is applied to NF, NF becomes 26 (= 19 + 7) dB. The output C / N (TUNER 0UT) of the tuner at this time is calculated | required by substitution into Formula (2) shown below.
    C / N (TUNER OUT) = 10 Log (Ci / Ni + (NF-1) kTB)) (2)
    Where Ci is the input RF signal level (true) of the tuner, Ni is the tuner input noise level (true), k is the Boltzmann integer (= 1.38E-23), T is the absolute temperature (300K), and B is Bandwidth (6 MHz). Ci, Ni and NF are calculated | required from following Formula.
    Ci = 10 ((-55-30) / 10) ≒ 3.2E-9 (3)
    Ni = 10 ((-82-30) / 10) ≒ 6.3E-12 (4)
    NF = 10 (26/10) ≒ 400 (5)
    Substituting said value and the calculation result of Formula (3)-Formula (5) into Formula (2) becomes like following Formula (6).
    C / N (TUNER OUT) = 10 Log ((3.2E-9)
    /((6.3E-12) + (400-1) × (1.38E-23) × 300 × (6E + 6)))
    = 10 Log (197.5) ≒ 23 (dB) (6)
    The calculation result of Equation (6) shows that 2 dB is insufficient for the output C / N = 25 dB required for the tuner.
    Therefore, as described above, when receiving a terrestrial RF signal, intermodulation distortion is reduced, so that the AGC point is set to high sensitivity (setting to operate the AGC circuit even if the deterioration level of the input RF signal level is small). Although it is necessary, when receiving a CATV RF signal, the noise level is higher than that of the terrestrial wave. Therefore, in order to receive a good C / N RF signal, the AGC point setting for receiving the CATV RF signal has a lower sensitivity than the terrestrial wave ( There is a problem that it is difficult to set the optimum AGC point for these two signals when the drop level of the input RF signal level is large.
    The present invention has been made in view of such a situation, and an optimal AGC point is set for each of the digital television signal by terrestrial wave and the digital television signal by CATV.
    1 is a diagram showing a configuration example of a circuit for setting a conventional RF AGC point.
    FIG. 2 is a diagram illustrating input and output characteristics of the circuit of FIG. 1. FIG.
    3 is a block diagram showing a configuration example of a digital television signal receiving apparatus to which the present invention is applied;
    4 is a diagram showing a configuration example of a circuit for setting an RF AGC point to which the present invention is applied.
    FIG. 5 is a diagram illustrating input and output characteristics of the circuit of FIG. 4. FIG.
    Explanation of symbols on the main parts of the drawings
    1: Comparator 2: Reference Power
    11: antenna 12: tuner
    13: SAWF 14: IF AGC Amplifier
    15 ADC 16 Digital Demodulator
    21a, 21b: reference power 22: changeover switch
    23: comparator
    The digital signal receiving apparatus according to claim 1 further comprises setting means for individually setting AGC points of the first signal and the second signal, and an input signal corresponding to any one of the first signal and the second signal, to the setting means. And switching means for switching the AGC point set by the controller.
    The digital signal receiving method according to claim 3 comprises a setting step of individually setting AGC points of the first signal and the second signal, and a setting step of the input signal corresponding to any one of the first signal and the second signal. It characterized in that it comprises a switching step of switching the AGC point set in.
    The providing medium according to claim 4 has a setting step of individually setting AGC points of the first signal and the second signal, and an AGC set in the setting step in which the input signal corresponds to any one of the first signal and the second signal. And a computer readable program for executing a process including a switching step of switching points.
    In the digital signal receiving apparatus according to claim 1, the digital signal receiving method according to claim 3, and the providing medium according to claim 4, AGC points of the first signal and the second signal are individually set and input. Is switched corresponding to either one of the first signal and the second signal.
    Embodiment of the invention
    3 shows an example of the configuration of a digital television signal receiving apparatus to which the present invention is applied. The antenna 11 receives a terrestrial digital television signal as an RF signal and outputs it to the tuner 12. Further, a digital television signal of CATV is input to the tuner 12 from the terminal 10. The tuner 12 converts the digital television signal of the RF signal received from the antenna 11 into a predetermined constant IF signal and outputs it to the Surface Acoustic Wave Filter (SAWF) 13.
    The SAWF 13 passes only the desired frequency signal from the received IF signal. The IF AGC amplifier (hereinafter referred to as IF AGC amplifier) 14 sets the input IF signal to a predetermined level and outputs it to the ADC (Analog Digital Converter) 15.
    The ADC 15 converts the signal input from the IF AGC amplifier 14 into an digital signal from an analog signal and outputs it to the digital demodulator 16. The digital demodulator 16 demodulates the input digital signal and outputs an image signal to a circuit of a later stage (not shown).
    Next, the operation of the digital television signal receiving device of FIG. 3 will be described. The terrestrial or CATV digital television signal received as an RF signal from the antenna 11 or the terminal 10 is converted in the tuner 12 into an IF signal of a predetermined frequency. At this time, the tuner 12 controls the gain of the IF signal based on the RF AGC signal sent from the IF AGC amplifier 14 and outputs it to the SAWF 13.
    The SAWF 13 extracts only a signal having a desired frequency from the received IF signal and outputs it to the IF AGC amplifier 14. The IF AGC amplifier 14 amplifies the input IF signal to a predetermined level and outputs it to the ADC 15. Control of the gain of the output signal of the IF AGC amplifier 14 is performed based on the AGC signal from the digital demodulator 16.
    The ADC 15 converts the received signal from an analog signal into a digital signal and outputs it to the digital demodulator 16. The digital demodulator 16 demodulates the received digital signal into an image signal, outputs it to a circuit not shown in the following figure, and outputs an IF AGC signal to the IF AGC amplifier 14.
    As described above, in the digital television signal receiving apparatus, the tuner 12 performs the RF AGC based on the RF AGC signal sent from the IF AGC amplifier 14 to the tuner 12, and the IF from the digital demodulator 16. Based on the IF AGC signal sent to the AGC amplifier 14, the IF AGC amplifier 14 performs IF AGC.
    After the IF AGC is caught in advance, at the point where the input level of the tuner 12 becomes constant, the RF AGC is applied. This makes it easy to obtain a good S / N or C / N image with the maximum sensitivity of the tuner 12 for the IF signal, and then suppresses the gain of the tuner 12 for the RF signal, thereby intermodulating distortion. This is to prevent the back from occurring.
    4 shows an example of the configuration of a circuit for controlling the RF AGC point embedded in the IF AGC amplifier 14. The IF AGC signal from the digital demodulator 16 is input to the non-inverting input terminal of the comparator 23. The reference voltage V1 or V2 is input to the inverting input terminal of the comparator 23 from the reference power supply 21a or the reference power supply 21b via the changeover switch 22. The signal output from the output terminal of the comparator 23 is output to the tuner 12 as an RF AGC signal.
    The reference voltages V1 and V2 (V1> V2) of the reference power sources 21a and 21b become the set voltages of the RF AGC point when the digital television signals of terrestrial wave and CATV are respectively received, and the reference voltage V1 is The value is larger than the reference voltage V2.
    The IF AGC amplifier 14 receives a signal from a microcomputer (not shown) indicating whether the input signal is a digital television signal of a terrestrial wave or a digital television signal of a CATV. Is connected to the power supply 21b in the case of CATV. That is, the changeover switch 22 can switch between two set voltages (RF AGC points).
    The operation of the circuit for controlling the RF AGC point when receiving the terrestrial wave of FIG. 4 will be described. The IF AGC amplifier 14 receives a signal indicating the type of the input signal from the microcomputer, and when the input signal is terrestrial wave, connects the changeover switch 22 to the voltage power supply 21a and inverts the input of the comparator 23. Input the reference voltage (V1) to the terminal. The IF AGC signal output from the digital demodulator 16 is input to the non-inverting input terminal 1 of the comparator 23.
    The comparator 23 compares the reference voltage V1 input to the inverting input terminal with the voltage (level) of the IF AGC signal input to the non-inverting input terminal, and shows the IF AGC signal as shown by the solid line of FIG. 5. If the voltage is greater than the reference voltage V1 of the inverting input terminal, the RF AGC signal is output at a constant high level.If the voltage of the IF AGC signal is less than the voltage V1, the level of the RF AGC signal is increased according to the level. Slowly make it smaller.
    The RF AGC signal is output to the tuner 12, and the tuner 12 controls the gain of the output IF signal based on this RF AGC signal.
    On the other hand, when the tuner 12 receives the digital television signal of CATV, the changeover switch 22 is connected to the voltage power supply 21b, and the reference voltage V2 is compared with the IF AGC signal. The following processing is the same.
    Next, reference voltages V1 and V2 of the voltage power supplies 21a and 21b will be described.
    For example, when the bandwidth is 6 MHz, the thermal noise level is -106 dBm, the NF of the tuner 12 is 7 dB, and the required C / N as the output of the tuner 12 is 25 dB. The AGC (RF AGC) point of the tuner 12 in the case of receiving is calculated similarly to Formula (7) similarly to Formula (1) mentioned above.
    -106 + 7 + 25 = -74 dBm (7)
    Therefore, when receiving a terrestrial digital television signal, the reference voltage V1 of the voltage power supply 21a is good if the voltage (AGC point) satisfying the input RF signal level -74 dBm shown in equation (7). .
    On the other hand, when the tuner 12 receives the CATV RF signal, for example, when the input RF signal level is -55 dBm and the C / N at that time is 27 dB, the noise level is -82 (= -55- 27) dBm. The output C / N (TUNER OUT) of the tuner 12 at this time is calculated | required as follows by substituting these values into Formula (2) of C / N (TUNER OUT) mentioned above.
    Ci = 10 ((-55-30) / 10) ≒ 3.2E-9 (8)
    Ni = 10 ((-82-30) / 10) ≒ 6.3E-12 (9)
    NF = 10 (7 / l0) ≒ 5 (10)
    Substituting the said value and the calculation result of Formula (8)-Formula (10) into Formula (2), it becomes like following Formula (11).
    C / N (TUNNER 0UT) = 10 Log ((3.2E-9)
    /((6.3E-12)+(5-1)×(1.38E-23)×300×(6E+6)))
    = 10 Log (500) ≒ 27 (dB) (11)
    As shown in Equation (11), when the voltage V2 of the voltage power supply 21b is a voltage satisfying 55 dBm of the RF AGC point, 25 which is C / N (TUNER OUT) required for the tuner 12 is obtained. Satisfies the condition of dB.
    Therefore, in this example, a voltage (RF AGC point) satisfying each of V1 when receiving a digital television signal of terrestrial wave is -74 dBm and V2 when receiving a digital television signal of CATV is -55 dBm. It is preferable to set as possible.
    As shown in Fig. 5, the reference voltage V2 (dotted dashed line in Fig. 5) in the case of receiving the digital television signal of CATV based on the RF AGC point is the reference voltage in the case of receiving the terrestrial digital television signal ( The voltage is set lower than V1 (solid line in Fig. 5). For this reason, the RF AGC can be set to a position where CATV is less likely to be caught than terrestrial waves.
    As described above, in the digital television signal receiving apparatus, it is possible to set different RF AGC points by using the digital television signal of the terrestrial wave and the digital television signal of the CATV, so that an optimal RF AGC point can be set for each digital television signal. have.
    In the above example, two settings by terrestrial wave and CATV have been described. However, when there are also several digital television signals having different input signal levels and noise levels other than terrestrial wave and CATV, the number of voltage power sources is three. In this way, the use of the changeover switch 22 can be switched to enable the setting of three or more RF AGC points.
    As a providing medium for providing a user with a computer program that performs the above-described processing, a communication medium such as a network or a satellite can be used in addition to a recording medium such as a magnetic disk, a CD-R0M, or a solid state memory.
    According to the digital signal receiving apparatus according to claim 1, the digital signal receiving method according to claim 3, and the providing medium according to claim 4, AGC points of the first signal and the second signal are set individually, and the input signal is Since the first signal and the second signal can be switched in correspondence with any one of the first signal and the second signal, an optimal AGC point can be set.
    权利要求:
    Claims (9)
    [1" claim-type="Currently amended] In the digital signal receiving apparatus capable of receiving both signals of the first signal and the second signal,
    Setting means for individually setting AGC points of the first signal and the second signal;
    And a switching means for switching the AGC point set by the setting means in response to the input signal corresponding to any one of the first signal and the second signal.
    [2" claim-type="Currently amended] The method of claim 1,
    And said first signal and said second signal are digital television signals of terrestrial waves and digital television signals of CATV.
    [3" claim-type="Currently amended] The method of claim 3, wherein
    The AGC point of the digital television signal of the CATV is set lower than the AGC point of the digital television signal of the terrestrial wave.
    [4" claim-type="Currently amended] In the digital signal receiving apparatus for receiving digital terrestrial broadcasting and digital CATV broadcasting,
    A tuner having a first automatic gain controller circuit controlled by the first control signal and converting the supplied digital terrestrial broadcasting RF signal or the digital CATV broadcasting RF signal into an IF signal, and outputting the IF signal;
    A second automatic gain controller circuit for controlling the level of the IF signal supplied from the tuner based on the control signal of the second control signal;
    A processing circuit for processing the output signal of the second automatic gain controller circuit and generating the second control signal;
    A control circuit for controlling the level of the first control signal based on a result of the comparison between the second control signal and a reference signal;
    And a switching circuit for switching the level of the reference signal when receiving the digital terrestrial broadcast and receiving the digital CATV broadcast.
    [5" claim-type="Currently amended] The method of claim 4, wherein
    And the control circuit is provided inside the second automatic gain controller circuit.
    [6" claim-type="Currently amended] The method of claim 4, wherein
    And the switching circuit is configured by a microcomputer.
    [7" claim-type="Currently amended] A digital signal receiving method of a digital signal receiving apparatus capable of receiving both signals of a first signal and a second signal,
    A setting step of individually setting AGC points of the first signal and the second signal;
    And a switching step of switching the AGC point set in the setting step in response to the input signal corresponding to any one of the first signal and the second signal.
    [8" claim-type="Currently amended] The method of claim 7, wherein
    And the first signal and the second signal are terrestrial digital television signals and CATV digital television signals.
    [9" claim-type="Currently amended] The method of claim 8,
    And the AGC point of the digital television signal of the CATV is set lower than the AGC point of the digital television signal of the terrestrial wave.
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    同族专利:
    公开号 | 公开日
    JP4359795B2|2009-11-04|
    US6421098B1|2002-07-16|
    MXPA00002443A|2004-10-28|
    JP2000270279A|2000-09-29|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    1999-03-12|Priority to JP99-066633
    1999-03-12|Priority to JP6663399A
    2000-03-10|Application filed by 이데이 노부유끼, 소니 가부시끼 가이샤
    2001-01-26|Publication of KR20010006770A
    优先权:
    申请号 | 申请日 | 专利标题
    JP99-066633|1999-03-12|
    JP6663399A|JP4359795B2|1999-03-12|1999-03-12|Digital signal receiving apparatus and method, and recording medium|
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