JP2008154021A - High frequency receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency receiver for improving receiving sensitivity in a weak electric field signal and improving a disturbance characteristic by a large disturbance signal. <P>SOLUTION: The high frequency receiver is provided with an amplifier 12 inserted between an input terminal 10 and an amplifier 13, and a gain control device 21 connected between a gain controllable input provided in the amplifier 12 and an output of a gain control device 20. Thus, the high frequency receiver can achieve a desired purpose. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high-frequency receiving apparatus that enables good reception in accordance with each of reception conditions for a television broadcast signal in an area with a large interference signal or reception conditions for a television broadcast signal in a weak electric field area. It is.

  Hereinafter, the conventional high frequency receiver 1 will be described. FIG. 3 is a block diagram of a conventional high-frequency receiving device 1.

  In FIG. 3, a high frequency receiver 1 includes an input terminal 2 to which a television broadcast signal is input, a high frequency amplifier 3 connected to the input terminal 2, and an output of the high frequency amplifier 3 connected to one input. The other input has a mixer 5 to which the output of the local oscillator 4 is connected, an intermediate frequency filter 6 to which the output of the mixer 5 is connected, and an intermediate frequency amplifier 7 to which the output of the intermediate frequency filter 6 is connected. And an output terminal 8 to which the output of the intermediate frequency amplifier 7 is connected.

  In addition, at least the high-frequency amplifier 3, the local oscillator 4, and the mixer 5 are integrated to constitute an integrated circuit 1a.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2002-367964 A

  However, in the conventional high frequency receiver 1, the high frequency amplifier 3 and the mixer 5 are integrated circuits 1a. Since the integrated circuit 1a is integrated, the characteristics due to the noise figure and the interference signal are inferior. For this reason, the reception performance was insufficient.

  The present invention solves this problem, and aims to improve the reception sensitivity of a weak electric field signal and improve the interference characteristics due to a large interference signal.

  In order to solve the above problems, a second amplifier inserted between the input terminal and the first amplifier, a second input capable of gain control provided in the second amplifier, and the first gain control And a second gain controller connected between the output of the device. As a result, the intended purpose can be achieved.

  As described above, the second amplifier inserted between the input terminal and the first amplifier, the second input capable of gain control provided in the second amplifier, and the output of the first gain controller. And a second gain controller connected to each other.

  As described above, since the second amplifier is provided in the reception condition in the weak electric field area, a high-frequency receiver with a small noise figure can be obtained. For this reason, the receiving sensitivity in a weak electric field signal can be greatly improved.

  The second amplifier uses a semiconductor with good interference characteristics, and the input signal level at which gain control of the second amplifier starts is set smaller than the input signal level at which gain control of the first amplifier starts. For this reason, the influence on the distortion by the first amplifier can be reduced. Therefore, a high-frequency receiving device with good interference characteristics can be obtained even under reception conditions with a large interference signal.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of the high-frequency receiving device 9. In the embodiment of the present invention, a high-frequency receiving device 9 that receives a digital television broadcast signal will be described as an example.

  The high frequency receiving device 9 is provided with an input terminal 10 and an output terminal 11 to which an antenna is connected. In order from the input terminal 10 to the output terminal 11, an amplifier 12 for amplifying an input signal from the input terminal 10, an amplifier 13 connected to the output of the amplifier, and an output of the amplifier 13 are connected to one input. The mixer 14, the local oscillator 15 connected to the other input of the mixer 14, the intermediate frequency filter 17 connected to the output of the mixer 14, and the intermediate connected to the output of the intermediate frequency filter 17. A frequency amplifier 18 and a demodulation circuit 19 connected to the output of the intermediate frequency amplifier 18 are connected.

  Further, a gain controller 20 for making the output level of the mixer 14 constant is connected between the output of the mixer 14 and the gain control input 13 a for gain control of the amplifier 13. Further, a gain controller 21 is connected from the gain control input 13 a to the gain control input 12 a for gain control provided in the amplifier 12.

  The gain controller 21 is provided with an input terminal 21a and an output terminal 21b. A differential amplifier 21c is connected from the input terminal 21a to the output terminal 21b. Furthermore, a resistor 21d is connected between the input terminal 21a and one input of the differential amplifier 21c, and an input terminal 21f to which a reference voltage is input is connected to the other input. A resistor 21e is connected between one input of the differential amplifier 21c and the output terminal 21b.

  The operation of the high-frequency receiving device 9 configured as described above will be described. The received signal at the input terminal 10 is gain-controlled by the amplifiers 12 and 13 and supplied to one input of the mixer 14.

  An oscillation signal from the local oscillator 15 is input to the other input of the mixer 14. Thus, a desired signal having an intermediate frequency of, for example, 570 kHz is output from the output of the mixer 14. The intermediate frequency signal is input to the intermediate frequency filter 17 so that the interference signal can be suppressed.

  The intermediate frequency signal output from the intermediate frequency filter 17 is amplified by the intermediate frequency amplifier 18 and input to the demodulation circuit 19. After being converted into a digital signal by the demodulation circuit 19, a TS (transport stream) signal is output from the output terminal 11.

  Next, the gain controller 20 will be described. The intermediate frequency signal output from the mixer 14 is input to the gain controller 20. The gain controller 20 detects the intermediate frequency signal and outputs a gain control voltage corresponding to the detection level.

  This gain control voltage is supplied to the gain control input 13 a of the amplifier 13 and is also supplied to the gain control input 12 a of the amplifier 12 via the gain controller 21.

  In this manner, the gains of the amplifiers 12 and 13 are controlled by the gain controllers 20 and 21, respectively. Thereby, the output level of the mixer 14 is made constant.

  Next, using the amplifier 12 and the gain controller 21, the improvement of characteristics for a large interference signal and the reception sensitivity in a weak electric field area will be described below.

  As the amplifier 12, a semiconductor element having a noise figure smaller than that of the integrated circuit 16 and having excellent disturbance characteristics can be used. For example, a field effect transistor may be used.

  First, the improvement of characteristics with respect to a large interference signal will be described. The respective input signal levels at the input terminal 10 at which gain control of the amplifiers 12 and 13 is started are assumed to be V12 and V13. Then, using the gain controller 21, this input signal level V12 is set smaller than the input signal level V13.

  Thereby, even if the interference signal level becomes stronger, the gain attenuation amount by the amplifier 12 is set larger, so that the distortion by the amplifier 13 can be reduced.

  The amplifier 12 uses a semiconductor element that is superior to the interference characteristics of the amplifier 13. For this reason, it becomes possible to improve the distortion characteristic as the high frequency receiver 9, and the disturbance characteristic with respect to the adjacent disturbance signal can be improved.

  FIG. 2 is a characteristic diagram of the gain control voltage output from the gain controllers 20 and 21 with respect to the input signal level.

  In FIG. 2, the horizontal axis 25 represents the input signal level at the input terminal 10, and the vertical axis 26 represents the gain control voltage. The characteristic 22 represents the gain control voltage of the gain controller 20 with respect to the input signal level to the input terminal 10.

  The gain control voltage having this characteristic 22 is input to the gain controller 21. The gain control voltage output from the gain controller 21 has a characteristic 23 when the resistance value of the resistor 21e is smaller than or equal to the resistance value of the resistor 21d. When the resistance value of the resistor 21e is larger than the resistance value of the resistor 21d, the characteristic 24 is obtained.

  That is, the gain control voltage output from the gain controller 21 with respect to the input signal level can be changed by changing the distribution of the resistance values of the resistors 21d and 21e. Therefore, if the resistance value of the resistor 21e is smaller than or equal to the resistance value of the resistor 21d, V12 can be made smaller than V13.

  Thereby, the gain attenuation amount in the amplifier 12 can be made larger than the gain attenuation amount in the amplifier 13. Therefore, it is possible to improve the distortion characteristics as the high-frequency receiving device 9. As a result, it is possible to improve the disturbance characteristics with respect to adjacent disturbance signal levels.

  On the other hand, under the reception condition in the weak electric field area, the gains of the amplifier 12 and the amplifier 13 are operated at a value close to the maximum value. For this reason, the noise figure of the high frequency receiver 9 is determined by the amplifier 12 having a small noise figure, and the high frequency receiver 9 can be set to a small noise figure.

  As a result, it is possible to realize the high-frequency receiving device 9 with good reception sensitivity in a weak electric field.

  The high-frequency receiving device according to the present invention can be used for a device that receives a high-frequency signal under severe receiving conditions.

Block diagram of the high-frequency receiving device according to Embodiment 1 of the present invention Gain control voltage characteristics diagram of gain controller Block diagram of a high-frequency receiving device in a conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 9 High frequency receiver 10 Input terminal 12 Amplifier 12a Gain control input 13 Amplifier 13a Gain control input 14 Mixer 15 Local oscillator 20 Gain controller 21 Gain controller

Claims (4)

An input terminal; a first amplifier connected to the input terminal; a mixer with an output of the first amplifier connected to one input; a local oscillator connected to the other input of the mixer; A first gain controller connected between the output of the mixer and a first input capable of gain control provided in the first amplifier, the input terminal and the first amplifier And a second amplifier connected between the second gain controllable second input provided in the second amplifier and the output of the first gain controller. A high-frequency receiving device provided with a gain controller. The high-frequency receiving device according to claim 1, wherein the second amplifier is a field effect transistor. The input signal level at which the gain control operation of the second amplifier starts as a signal input to the input terminal is set to be smaller than the input signal level at which the gain control operation of the first amplifier starts. The high frequency receiver described. The second gain controller is a differential amplifier in which the output of the first gain controller is connected to one input through the first resistor and the other input is a reference voltage. An output is connected to a second input of a second amplifier, a second resistor is connected between the first input and the output of the differential amplifier, and the first and second resistance values are changed. The high-frequency receiving device according to claim 1, wherein the input signal level at which gain control starts can be varied by means of.

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