JP2007235518A - Attenuator circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct the frequency characteristic of a high frequency circuit connected to the prestage or post stage of an attenuator circuit and to improve the input/output impedance of the high frequency circuit by preventing the high frequency circuit from being influenced by a change in the impedance of a frequency characteristic correction circuit. <P>SOLUTION: In the attenuator circuit, the high frequency amplifier is connected to the prestage of an input terminal 10. A first route 12 and a second route 13 are formed in parallel between the input terminal 10 and an output terminal 11. In the first route 12, a resistor element 14 and a correction circuit which is a serial LC circuit composed of a capacitor 16 and an inductor 15 and corrects the frequency characteristic of the high frequency amplifier are connected in series, and in addition the resistor element 14 is arranged between the high frequency amplifier and the correction circuit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an attenuator circuit in which a high frequency circuit is connected to an input stage or an output stage.

  Conventionally, an attenuator circuit is used in various high-frequency devices. For example, it is used to input the output signal of the high-frequency circuit provided in the previous stage and attenuate it to an appropriate signal level and output it to the subsequent stage, or attenuate it to an appropriate level for the subsequent high-frequency circuit and output it. ing. Also, an attenuator circuit has been proposed that can switch the attenuation ratio of a high-frequency signal using a diode (see, for example, Patent Document 1).

  FIG. 4 is a configuration diagram of an attenuator circuit described in Patent Document 1. In FIG. Two paths having different attenuation ratios are provided in parallel between one input / output terminal 120 and the other input / output terminal 130, the attenuator 100 is disposed on one path, and the switch unit 121 is disposed on the other path. It is arranged. Switch units 108 and 109 are connected before and after the attenuator 100. The anode side of the switch unit 121 is connected to the cathode side of the switch unit 108 and one end side of the resistor R1, and is also connected to the input / output terminal 120 via the capacitor C1. The other end of the resistor R1 is grounded. The cathode side of the switch unit 121 is connected to the anode side of the switch unit 109 and is connected to the input / output terminal 130 via the capacitor C3. Further, a positive or negative voltage can be applied to the cathode side of the switch unit 121 and the anode side of the switch unit 109 via the switch 106 and the resistor R3. The anode side of the switch unit 108 is connected to the cathode side of the switch unit 109 via the attenuator 100.

  The attenuator 100 includes a capacitor 101, a resistor 102, a capacitor 103 connected in series between one input / output terminal 110a and the other input / output terminal 110b, and a resistor 104 that grounds both ends of the resistor 102. , 105 and a DC bypass coil 106 connected between the input / output terminals 110a and 110b.

  According to the attenuator circuit configured as described above, for example, when the contact piece 106a of the switch 106 is connected to the second contact 106c in a state where a high frequency signal is input to the input / output terminal 120, the high frequency signal is connected to the input / output terminal 130. The signal is output without attenuation. Further, when the contact piece 106 a of the switch 106 is connected to the first contact 106 b, a high frequency signal attenuated by the attenuation ratio of the attenuator 100 is output to the input / output terminal 130.

That is, when the contact piece 106a of the switch 106 is connected to the second contact 106c, the diode D of the switch units 108 and 109 is reverse-biased and turned off, and the diode D of the switch unit 121 is forward-biased and turned on. become. Therefore, the high frequency signal input to the input / output terminal 120 is output to the input / output terminal 130 via the switch unit 121. When the contact piece 106a of the switch 106 is connected to the first contact 106b, the diode D of the switch unit 121 is reverse-biased and turned off, and the diode D of the switch units 108 and 109 is forward-biased and turned on. become. Therefore, the high frequency signal input to the input / output terminal 130 is output to the input / output terminal 130 via the switch units 108 and 109 and the attenuator 110.
Japanese Patent Laid-Open No. 4-140915

  However, when a high-frequency circuit having a predetermined frequency characteristic is connected to the input / output terminal of the attenuator circuit, it is necessary to attenuate the input signal depending on the selected frequency band, and the frequency characteristic of the high-frequency circuit is affected. However, there is a problem that the input / output impedance of the high-frequency circuit is deteriorated by adding a correction circuit for correcting the frequency characteristics.

  The present invention has been made in view of the above points, and can correct the frequency characteristics of the high-frequency circuit connected to the preceding stage or the subsequent stage, and can prevent the influence of the input / output impedance to the high-frequency circuit. An object is to provide an attenuator circuit.

  An attenuator circuit according to the present invention is an attenuator circuit in which a high frequency circuit is connected to a front stage of an input end or a rear stage of an output end, and includes at least one resistor provided between the input end and the output end, and a capacitor And a correction circuit that is connected in series with the resistor so that the resistor is interposed between the resistor and the high-frequency circuit, and corrects the frequency characteristic of the high-frequency circuit. To do.

  According to this configuration, the frequency characteristic of the high frequency circuit can be corrected by the correction circuit provided in the attenuator circuit, and the correction circuit from the high frequency circuit side is provided by the signal attenuation resistor interposed between the high frequency circuit and the correction circuit. Therefore, even if a correction circuit is added, stable operation can be realized without changing the input / output impedance of the high-frequency circuit.

  In the attenuator circuit according to the present invention, the resistor includes a first resistor provided before the correction circuit and a second resistor provided after the correction circuit. .

  With this configuration, a resistor is provided before and after the correction circuit, so even if a high frequency circuit is connected to the front stage of the input end and the rear stage of the output end of the attenuator circuit, both of the correction circuits can be added by adding the correction circuit. Impedance fluctuations of the high frequency circuit can be suppressed, and stable operation can be realized.

  According to the present invention, in the attenuator circuit, a first path formed by the resistor and the correction circuit connected in series between the input end and the output end, the input end and the output end And a second path having a first switching element provided in parallel with the first path, and applied to the input terminal when the first switching element is in a non-conductive state. When the first high frequency signal is attenuated in the first path and output from the output end, and the first switching element is turned on, the high frequency signal applied to the input end is The signal is output from the output end without being attenuated in the path.

  With this configuration, when the first switching element is turned off, a high-frequency signal attenuated by a resistor in the first path can be output from the output end, and the first switching element is turned on. In the state, the high-frequency signal can be output from the output end without being attenuated in the second path.

  In the attenuator circuit, it is preferable that a second switching element is provided in each of a first stage and a rear stage of the correction circuit in the first path.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to correct | amend the frequency characteristic of the high frequency circuit connected to the front | former stage or back | latter stage of an attenuator circuit, it can prevent the influence of the impedance change of a frequency characteristic correction circuit reaching a high frequency circuit, and input / output of a high frequency circuit Impedance can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The present embodiment relates to an attenuator circuit provided in an analog tuner device capable of switching, for example, high band / low band of UHF band and VHF band. The attenuator circuit of the present invention can also be applied to high frequency circuits other than analog tuner devices.

  FIG. 1 is a configuration diagram of an attenuator circuit according to an embodiment of the present invention. The attenuator circuit according to the present embodiment allows the high-frequency signal to pass between the input terminal 10 and the output terminal 11 without attenuation and the first path 12 that exhibits the high-frequency signal attenuation action and the frequency characteristic correction action. The second path 13 is provided in parallel. The input terminal 10 shown in FIG. 1 is connected to the output terminal of a high-frequency amplifier (not shown). This high-frequency amplifier is a high-frequency circuit connected in front of the input end of the attenuator circuit.

  A series circuit including a resistance element 14, an inductor 15, and a capacitor 16 is formed in the first path 12. The resistance element 14 is a resistance for attenuating a high-frequency signal propagating through the path, and has one end connected to the input terminal 10 and the other end connected to one end of the inductor 15. The inductor 15 is formed in a pattern having a length corresponding to a required frequency characteristic. The other end of the inductor 15 is connected to one electrode of the capacitor 16, and the other electrode of the capacitor 16 is connected to the output terminal 11. The inductor 15 and the capacitor 16 constitute an LC circuit, which acts as a correction circuit that corrects the frequency characteristics of a high-frequency amplifier circuit (not shown). That is, the frequency characteristic of the LC circuit including the inductor 15 and the capacitor 16 is determined so that the high-frequency amplifier circuit connected to the input terminal 11 has a desired frequency characteristic in a frequency band that requires correction according to the frequency characteristic. ing.

  The second path 13 is provided with a diode 17 that acts as a first switching element. The diode 17 has a cathode side connected to the input terminal 10 and an anode side connected to the output terminal 11. The high frequency signal passes through the second path 13 in the ON state where the diode 17 is forward biased, and the high frequency signal passes through the first path 12 in the OFF state where the diode 17 is reverse biased.

  A band select signal is applied to the control terminal 18 connected to one end of the input terminal 10 and the resistance element 14. The band select signal is a signal for selecting the high band / low band of the UHF band or the VHF band. In the present embodiment, the band select signal is a predetermined positive voltage when a band that requires signal attenuation is selected from the high band / low band of the UHF band or VHF band, and the band is selected when a band that does not require signal attenuation is selected. The select signal becomes the ground voltage. The output terminal 11 is connected to a voltage application terminal 19 to which a power supply voltage is applied. The voltage application terminal 19 is connected to the output terminal 11 via a resistance element 21. A connection point between the output terminal 11 and the resistance element 21 is grounded via the resistance element 22.

Next, the operation of the attenuator circuit configured as described above will be described.
When a high frequency signal is applied to the input terminal 10 and the band select signal applied to the control terminal 18 is a predetermined positive voltage that requires signal attenuation, the diode 17 is reverse-biased and turned off. As a result, the high frequency signal applied to the input terminal 10 is output from the output terminal 11 via the first path 12. When the high-frequency signal passes through the first path 12, the signal level is attenuated by a predetermined amount by the resistance element 14.

  The high-frequency amplifier disposed immediately before the input terminal 10 is connected to an LC circuit including an inductor 15 and a capacitor 16 via a resistance element 14. For this reason, when the high-frequency signal output from the high-frequency amplifier is output from the input terminal 10 through the first path 12 and output from the output terminal 11, the inductor 15 and the capacitor 16 are connected in series to the first path 12. The frequency characteristic is corrected by the LC circuit.

  In addition, in the present embodiment, the inductor 15 and the high frequency amplifier are connected with the signal attenuating resistance element 14 interposed therebetween, so that an LC circuit including the inductor 15 and the capacitor 16 is connected to the subsequent stage of the high frequency amplifier. The change in impedance due to this is mitigated by the resistance element 14, and the problem that the output impedance of the high-frequency amplifier changes can be prevented.

  Also, when a high frequency signal is applied to the input terminal 10 and the band select signal applied to the control terminal 18 is a ground voltage that does not require signal attenuation, a forward bias is applied to the diode 17 to turn it on. The high frequency signal applied to the input terminal 10 passes through the second path 13 and is output from the output terminal 11 without being attenuated.

  As described above, in the present embodiment, the LC circuit including the inductor 15 and the capacitor 16 that corrects the frequency characteristics of the high-frequency amplifier is provided in series with the resistance element 14 that attenuates the signal level of the input high-frequency signal. The frequency characteristic of the high-frequency amplifier provided in the previous stage of the attenuator circuit can be corrected, and the resistance element 14 makes it difficult to see the impedance of the LC circuit composed of the inductor 15 and the capacitor 16 from the output terminal of the high-frequency amplifier, and to the output terminal of the high-frequency amplifier. A change in output impedance due to the connection of the LC circuit can be prevented, and the operation stability of the high-frequency amplifier can be improved.

  The above description is about an embodiment in which a high-frequency amplifier is disposed in the previous stage of the attenuator circuit. Next, an embodiment in which a high-frequency amplifier or other high-frequency circuit is disposed in the subsequent stage of the attenuator circuit will be described.

  FIG. 2 is a configuration diagram of the attenuator circuit when a high-frequency circuit is connected to the front stage and the rear stage of the attenuator circuit. The same components as those of the attenuator circuit shown in FIG.

  In the attenuator circuit shown in the figure, a resistance element 23 is inserted in series between the other electrode of the capacitor 16 and the output terminal 11 in the first path 12. The output terminal 11 is connected to an input terminal of a high frequency circuit (not shown). The LC circuit composed of the inductor 15 and the capacitor 16 is designed so as to be able to correct the frequency characteristic of the subsequent high-frequency circuit.

  In the attenuator circuit configured as described above, when the high-frequency signal applied to the input terminal 10 is output from the output terminal 11 via the first path 12, the resistance element 14 and the other resistance element 23 are connected. Each attenuates the signal level. A high-frequency signal attenuated according to the combined resistance value of the resistance elements 14 and 23 is output from the output terminal 11 to the subsequent high-frequency circuit.

  The LC circuit composed of the inductor 15 and the capacitor 16 is connected to the input terminal of the subsequent high-frequency circuit. However, the resistance element 23 makes it difficult to see the impedance of the LC circuit composed of the inductor 15 and the capacitor 16 from the subsequent high-frequency circuit. The input impedance change due to the LC circuit being connected to the input terminal of the high-frequency circuit can be prevented, and the operation stability of the subsequent high-frequency circuit can be improved.

  Note that if the high-frequency circuit is not connected to the previous stage of the attenuator circuit, one resistance element 14 may not be provided.

  In FIG. 3, resistance elements 14 and 23 are provided before and after the LC circuit including the inductor 15 and the capacitor 16 in the first path 12 of the attenuator circuit, and a diode 31 serving as a second switching element is provided on both sides of the first path 12. , 32 are connected in the forward direction. A DC bypass coil 106 is provided between the cathode of the diode 31 provided on the input side and the anode of the diode 32 provided on the output side.

  In the attenuator circuit configured as described above, when a predetermined positive voltage is applied to the control terminal 18, the diode 17 of the second path 13 is turned off with a reverse bias, while the input of the first path 12 is turned off. The diode 31 on the side is turned on by applying a forward bias, and the diode 31 on the output side is turned on by applying a forward bias to the diode 32 on the output side via the DC bypass coil 33. As a result, the high frequency signal applied to the input terminal 10 is attenuated through the first path 12 and output from the output terminal 11.

  On the other hand, when a ground voltage is applied to the control terminal 18, the diode 17 in the second path 13 is turned on with a forward bias applied, while the diode 31 on the input side and the output side in the first path 12 are turned on. The diode 32 is turned off by applying a reverse bias. As a result, the high frequency signal applied to the input terminal 10 passes through the second path 13 and is output from the output terminal 11 without being attenuated.

  The resistance elements 14 and 23 provided in the first path 12 make it difficult to see the impedance of the LC circuit including the inductor 15 and the capacitor 16 from the input terminal 10 side and the output terminal 11 side of the attenuator circuit. Is the same as above.

  The present invention is not limited to the above-described embodiment (FIGS. 1, 2, and 3). For example, in the above description, the inductor 15 and the capacitor 16 for correcting the frequency characteristics of the high-frequency circuit connected to the front stage or the rear stage of the attenuator circuit are connected in series. However, the inductor 15 and the capacitor 16 are connected in parallel. Even if a parallel circuit is configured, the same effect can be obtained.

  In the above description, in addition to the first path 12 that attenuates the signal to the attenuator circuit, the second path 13 that passes without attenuating the signal is provided in parallel, but a bypass function that does not attenuate the signal is unnecessary. If present, the second path 13 is not necessary. That is, it is possible to configure an attenuator circuit with only the first path 12.

  The present invention can be applied to an attenuator circuit in which a high-frequency circuit having frequency characteristics is connected to the front stage or the rear stage of the circuit.

Configuration diagram of an attenuator circuit according to an embodiment of the present invention Configuration diagram of a modification in which a part of the embodiment shown in FIG. 1 is modified The block diagram of the modification which deform | transformed other one part of embodiment shown in FIG. Configuration of conventional attenuator circuit

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Input terminal 11 Output terminal 12 1st path | route 13 2nd path | route 14, 23 Resistance element 15 Inductor (pattern)
16 Capacitor 17 Diode (first switching element)
19 Power supply voltage terminal 31, 32 Diode (second switching element)
18 Control terminal 33 DC bypass coil

Claims (4)

An attenuator circuit in which a high-frequency circuit is connected to the front stage of the input terminal or the rear stage of the output terminal,
A series circuit or a parallel circuit of at least one resistor provided between the input end and the output end and a capacitor and an inductor, and the resistor interposed in series with the high frequency circuit. An attenuator circuit comprising: a correction circuit connected to correct a frequency characteristic of the high frequency circuit.   2. The attenuator circuit according to claim 1, wherein the resistor includes a first resistor provided before the correction circuit and a second resistor provided after the correction circuit. A first path formed by the resistor and the correction circuit connected in series between the input end and the output end, and the first path between the input end and the output end And a second path having a first switching element provided in parallel,
When the first switching element is in a non-conductive state, a high frequency signal applied to the input end is attenuated in the first path and output from the output end,
The high-frequency signal applied to the input terminal is output from the output terminal without being attenuated in the second path when the first switching element is in a conductive state. The attenuator circuit according to claim 2. 4. The attenuator circuit according to claim 3, wherein a second switching element is provided in each of a front stage and a rear stage of the correction circuit in the first path.

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