JP2006025001A - Receiving circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an AGC circuit capable of reducing sensitivity lowering when the AGC circuit works caused by an interference wave and reducing deterioration in the distortion characteristic of a receiving device caused by the interference wave. <P>SOLUTION: A variable attenuator unit 2 and a variable gain amplifier unit 4 are provided on a prestage and a poststage, respectively. When an RF signal input level increases, an AGC control unit 10 firstly controls the unit 4 so that an amplification gain is reduced to keep an attenuation amount of the unit 2 constant. When the RF signal input level increases and exceeds a specific RF signal level, the unit 10 sequentially controls the unit 2 so that an attenuation amount of the unit 2 is increased to keep an amplification gain of the unit 4 constant. At this time, the AGC unit 10 temporarily increases the amplification gain of the unit 4, thereby applying a current not less than a predetermined value to a PIN diode in the unit 2 to reduce the level of mutual modulation distortion. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a receiver capable of reducing sensitivity suppression due to an interference wave in a receiver provided with an AGC circuit in order to suppress the occurrence of intermodulation distortion due to strong input.

  A conventional AGC (Auto Gain Control) circuit of a basic receiver is provided with a variable attenuator in the input stage so that the signal level at a predetermined point in the receiver is below a certain level. The amount of attenuation of the variable attenuation unit is controlled. However, since this AGC circuit is provided with a variable attenuating unit at the input stage, when a large level of interference wave is input such that the AGC circuit operates, the AGC circuit operates to attenuate the desired signal along with the interference wave. However, sensitivity suppression occurs.

  For this reason, in order not to cause sensitivity suppression due to interference waves, a front end unit of a receiving apparatus provided with an AGC circuit as shown in FIG. 8 has been proposed (see, for example, Patent Document 1). In the front end unit 33, first, an RF (Radio Frequency) input signal received by the antenna is input to the RF input terminal 21, and the LPF (Low Pass Filter) 22 receives the reception band frequency or higher. The unnecessary band signal is removed and amplified by the RF amplifying unit 24 through the variable attenuating unit 23. Then, the signal passes through a front-stage BPF (Band Pass Filter) 25, a variable gain amplification unit 26, and a rear-stage BPF 27, and is mixed with the oscillation output of the oscillator 29 by the mixer 28 to be frequency-converted to obtain an IF (Intermediate Frequency). The signal is output from the IF output terminal 30 as a signal.

  The AGC detection unit 31 outputs an AGC control signal determined according to the IF output level extracted from the mixer 28, and the AGC control unit 32 receives the AGC control signal and receives the variable attenuating unit 23 and the variable gain amplifying unit 26. And control. When the level of the RF input signal exceeds the AGC operating level, the AGC control unit 32 first controls the variable gain amplification unit 26 to attenuate the gain. Further, when the level of the RF input signal rises and exceeds the maximum allowable input level determined from the distortion characteristics of the RF amplification unit 24, the distortion characteristics of the pre-stage BPF 25, the distortion characteristics of the variable gain amplification unit 26, and the like, the variable attenuation unit 23 When the attenuation is increased and the level of the RF signal input further increases and exceeds the maximum attenuation of the variable attenuator unit 23, the gain of the variable gain amplifying unit 26 is further attenuated to set the IF output level to a predetermined value. Limit to levels. Even if the RF input signal level exceeds the AGC operation level, the attenuation amount of the variable attenuating unit 26 does not increase until the maximum allowable input level is exceeded, and sensitivity suppression due to interference waves does not occur, so sensitivity suppression can be reduced.

FIG. 9 shows control of the variable gain amplifying unit 26 and the variable attenuating unit 23 by the AGC control unit 32, and the AGC circuit operates so that the IF output level becomes a predetermined level or less as shown in FIG. 9A. When the level of the RF input signal exceeds the AGC operation level, first, as shown in FIG. 9B, the AGC control unit 32 performs control so as to attenuate the gain of the variable gain amplification unit 26. Further, when the level of the RF input signal further rises and exceeds the maximum allowable input level determined from the distortion characteristics of the RF amplification unit 24, the distortion characteristics of the pre-stage BPF 25, the distortion characteristics of the variable gain amplification unit 26, etc., FIG. As shown in c), the attenuation amount of the variable attenuation unit 23 is increased. When the level of the RF input signal further increases and the attenuation amount of the variable attenuating unit 23 is saturated, the gain of the variable gain amplifying unit 26 is further attenuated.
JP 2001-168747 A

  However, in the AGC circuit that reduces the sensitivity suppression by the conventional interference wave, a large level RF input signal is input to the variable attenuating unit with the attenuation amount of the variable attenuating unit being small. When a variable attenuator generally adopted, that is, a PIN diode is provided between the signal line and GND, and the amount of attenuation is adjusted by controlling the current flowing through the PIN diode, the PIN diode is used. When the flowing current is small, a high level RF input signal is applied to the PIN diode, and there is a problem that the level of intermodulation distortion generated in the PIN diode is large.

  The present invention has been made to solve such a conventional problem, and reduces the sensitivity suppression due to the interference wave, thereby reducing the increase in the level of intermodulation distortion generated in the variable attenuation unit. An object of the present invention is to provide a receiving device including an AGC circuit that can be used.

  The receiving apparatus of the present invention is provided with a variable attenuator for attenuating the received RF input signal level in a variable amount of attenuation, and a variable gain amplifier for amplifying the input signal level variably by an amplification gain. And an AGC control unit that controls an attenuation amount of the variable attenuation unit and an amplification gain of the variable gain amplification unit so that a signal level at a predetermined point is equal to or lower than a predetermined level, and the variable attenuation unit, The variable gain amplifying unit is configured to change a gain of the variable attenuating unit by changing an amplification gain of the variable gain amplifying unit, and change an attenuation of the variable attenuating unit to change the attenuation of the variable attenuating unit. Operating in an operation region including a second operation region in which the amplification gain of the variable gain amplification unit is constant, and an RF input signal level in the second operation region is greater than an RF signal level in the first operation region, Above GC controller has a configuration of increasing the amplification gain of the variable gain amplifier unit from said first operation area when the transition to the second operating region.

  With this configuration, even if the level of the RF input signal exceeds the AGC operating level, the variable attenuating unit does not operate until the level of the RF input signal exceeds the level set based on the distortion characteristics and NF characteristics of the variable gain amplifying unit. Attenuation does not increase, and sensitivity suppression due to jamming can be reduced. When the level of the RF input signal further increases, the AGC control unit temporarily increases the gain of the variable gain amplifying unit by a specific level and controls the attenuation amount of the variable attenuation unit to be equal to or greater than the specific attenuation amount. Since a current of a certain level or more flows through the PIN diode in the variable attenuating unit, the intermodulation distortion generated in the PIN diode can be reduced, and the level of the intermodulation distortion generated in the variable attenuating unit can be reduced.

  The receiving apparatus according to the present invention is provided in a preceding stage variable attenuating section for attenuating the received RF input signal level in a variable amount of attenuation, and in a subsequent stage of the preceding stage variable attenuating section, and attenuating the input signal level in a variable amount of attenuation. A rear-stage variable attenuation section, and an AGC control section that controls the attenuation amount of the front-stage variable attenuation section and the attenuation amount of the rear-stage variable attenuation section so that the signal level at a predetermined point is a predetermined level or less, The first-stage variable attenuation section and the second-stage variable attenuation section include a first operation region in which the first-stage variable attenuation section is made constant by changing the attenuation amount of the second-stage variable attenuation section, and the first-stage variable attenuation section. And an operation region including a second operation region in which the attenuation amount of the latter-stage variable attenuation unit is made constant, and an RF input signal level in the second operation region is the first operation. RF signal in the region Greater than the bell, the AGC control unit has a configuration for reducing the attenuation amount of the subsequent attenuator from said first operation area when the transition to the second operating region.

  With this configuration, even if the level of the RF input signal exceeds the AGC operating level, the level of the RF input signal does not exceed the level set based on the distortion characteristics of the RF amplification unit and the distortion characteristics of the subsequent variable attenuation unit. The attenuation amount of the front stage variable attenuation unit does not increase, and the sensitivity suppression due to the interference wave can be reduced. When the level of the RF input signal further increases, the AGC control unit temporarily decreases the attenuation amount of the rear stage variable attenuation unit by a specific level and controls the attenuation amount of the front stage variable attenuation unit to be equal to or higher than the specific attenuation amount. Therefore, a current of a certain level or more flows through the PIN diode in the front-stage variable attenuation section, so that the intermodulation distortion generated in the PIN diode can be reduced, and the level of the inter-modulation distortion generated in the front-stage variable attenuation section can be reduced.

  In the receiving apparatus of the present invention, the RF input signal level when shifting from the second operation region to the first operation region shifts from the first operation region to the second operation region. The RF input signal level is set to be smaller than that.

  With this configuration, when the RF input signal level changes from an increase to a decrease near the RF input signal level where the attenuation amount of the variable attenuation unit or the preceding stage variable attenuation unit begins to increase, the attenuation amount and variable gain amplification of the variable attenuation unit It is possible to reduce the frequency at which the amplification gain of the part or the attenuation amount of the front stage variable attenuation part or the rear stage variable attenuation part changes suddenly.

  According to the present invention, when the level of the RF input signal exceeds the AGC operation level and further increases, the AGC control unit temporarily increases the amplification gain of the variable gain amplification unit by a certain level, and the attenuation amount of the variable attenuation unit is increased. By controlling so that the amount of attenuation is greater than a certain amount of attenuation, a certain amount of current flows through the PIN diode in the variable attenuation unit, and the intermodulation distortion generated by the PIN diode can be reduced. In addition, it is possible to provide a receiving apparatus having an effect that the deterioration of the distortion characteristic in the variable attenuation unit due to this can be reduced.

  Hereinafter, a receiving apparatus according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows the configuration of the front end unit 11 of the receiving apparatus including the AGC circuit according to the first embodiment of the present invention. In FIG. 1, an RF input signal received by an antenna is input to an RF input terminal 1. The RF input signal input to the RF input terminal 1 is amplified by the variable gain amplifying unit 4 through the variable attenuating unit 2 and the pre-stage tuning unit 3. Then, it passes through the subsequent tuning unit 5, is mixed with the oscillation output of the oscillator 7 by the mixer 6, is frequency-converted, and is output from the IF output terminal 8 as an IF signal. The AGC detection unit 9 outputs an AGC control signal determined according to the IF output level taken out from the mixer 6, and the AGC control unit 10 receives the AGC control signal and causes the variable attenuating unit 2 and the variable gain amplifying unit 4 to operate. It is the structure to control.

  The operation of the AGC circuit of the receiving apparatus configured as described above will be described with reference to FIG. As shown in FIG. 2A, the IF output level is controlled by the AGC circuit so as to be a predetermined level or less. When the level of the RF input signal exceeds the AGC operation level, first, as shown in FIG. 2B, the AGC control unit 10 attenuates the amplification gain of the variable gain amplifying unit 4 in the first operation region, thereby performing variable attenuation. Control is performed so that the attenuation amount of the unit 2 becomes a constant level. When the level of the RF input signal rises and exceeds the level set by the distortion characteristics of the pre-stage tuning unit 3, the distortion characteristics of the variable gain amplification unit 4, the NF characteristics, or the distortion characteristics of the post-stage tuning unit 5, In the second operation region B, the AGC control unit 10 once increases the amplification gain of the variable gain amplification unit 4 by a specific level. Further, in the second operation region B, as shown in FIG. 2C, the AGC control unit 10 performs control so that the attenuation amount of the variable attenuation unit 2 is greater than or equal to a specific attenuation amount, and further, RF Even if the level of the input signal rises, control is performed so that the attenuation amount of the variable attenuator 2 is increased so that the IF output level becomes a predetermined level. In the third operation region C in which the level of the RF input signal further increases and the attenuation amount of the variable attenuation unit 2 is saturated, the AGC control unit 10 has a predetermined IF output level as shown in FIG. Control to reduce the gain of the variable gain amplifying unit 4 is performed so that

  Next, a basic circuit configuration of the variable attenuation unit 2 is shown as a variable attenuation unit 17 in FIG. In FIG. 3, the RF signal input to the RF input terminal 12 is output from the RF output terminal 16. The resistor 14 has a sufficiently large impedance with respect to the input / output impedance of the variable attenuation unit 17. The current flowing through the PIN diode 13 is controlled by the control voltage applied to the voltage input terminal 15 and the impedance of the resistor 14, and the attenuation amount of the variable attenuation unit 17 is controlled.

  The operation of the variable attenuation section 17 configured as described above will be described with reference to FIG. As shown in FIG. 4A, when the voltage applied to the voltage input terminal 15 increases, the current flowing through the PIN diode 13 increases. The relationship between voltage and current can be adjusted by the resistor 14. When the current flowing through the PIN diode 13 increases, the impedance of the PIN diode 13 decreases, and the attenuation amount of the variable attenuation unit 17 increases as shown in FIG. 4B. When the current flowing through the PIN diode 13 increases, the influence of the decrease in the impedance of the PIN diode 13 on the attenuation amount of the variable attenuation unit 17 decreases, and the attenuation amount of the variable amplification unit 17 is saturated. FIG. 4C shows the level of intermodulation distortion generated in the variable attenuation unit 17 at this time. When a voltage is applied to the voltage input terminal 15, the level of intermodulation distortion generated at the PIN diode 13 increases, and when the voltage applied to the voltage input terminal 15 further increases, the level of intermodulation distortion generated at the PIN diode 13 decreases. I will do it. Therefore, the level of intermodulation distortion generated in the PIN diode 13 can be lowered by applying a voltage of a certain level or higher to the voltage input terminal 15. This is the reason why the amplification gain of the variable gain amplifying unit 4 is temporarily increased when shifting from the first operation region A to the second operation region B.

  As described above, according to the first embodiment of the present invention, the AGC control unit 10 that controls the variable attenuating unit 2 and the variable gain amplifying unit 4 has the RF input signal level of the variable gain amplifying unit 4. In the first operation region A below the level set based on the distortion characteristics and NF characteristics of the signal, the gain of the variable gain amplifying unit 4 is controlled so that the IF output level is below a predetermined level, and the RF input signal In the second operation region B in which the level exceeds the set level, the amplification gain of the variable gain amplifying unit 4 is once increased by a specific level, and the attenuation amount of the variable attenuation unit 2 is greater than or equal to the specific attenuation amount. In addition, since the IF output level is controlled to be a predetermined level, the level of intermodulation distortion generated in the PIN diode used in the preceding-stage variable attenuation unit 2 can be reduced, and the sensitivity suppression due to the interference wave is reduced. Pre-stage variable by this It is possible to reduce the deterioration in the distortion characteristic in 衰部 2.

(Embodiment 2)
Next, FIG. 5 shows the configuration of the front end unit 20 of the receiving apparatus provided with the AGC circuit according to the second embodiment of the present invention. In FIG. 5, the second embodiment is different from the first embodiment described above in that an RF amplifying unit 18 for amplifying an RF signal is provided at the subsequent stage of the variable attenuating unit (previous variable attenuating unit) 2 provided in the RF input stage. In addition to the provision of the variable gain amplifying unit 4, a variable attenuating unit (rear-stage variable attenuating unit) 19 that can vary the amount of attenuation is provided downstream of the RF amplifying unit 18. Since the other configuration is the same as the configuration shown in FIG. 1, the same components will be described with the same reference numerals. The RF input signal received by the antenna is input to the RF input terminal 1 and is amplified by the RF amplification unit 18 through the front stage variable attenuation unit 2 and the front stage tuning unit 3. Then, the signal passes through the post-stage tuning unit 5 and the post-stage variable attenuating unit 19 and is mixed with the oscillation output of the oscillator 7 by the mixer 6 to be frequency-converted and output from the IF output terminal 8 as an IF signal. The AGC detection unit 9 outputs an AGC control signal determined according to the IF output level taken out from the mixer 6, and the AGC control unit 10 receives the AGC control signal and receives the upstream variable attenuation unit 2 and the downstream variable attenuation unit. 19.

  The operation of the AGC circuit of the receiving apparatus configured as described above will be described with reference to FIG. As shown in FIG. 6A, the IF output level is controlled by the AGC circuit so as to be equal to or lower than a predetermined level. When the level of the RF input signal exceeds the AGC operation level, first, as shown in FIG. 6B, the AGC control unit 10 increases the attenuation amount of the rear stage variable attenuation unit 19 in the first operation region A, Control is performed so that the amount of attenuation of the variable attenuation unit 2 becomes a constant level. Then, the level of the RF input signal rises and exceeds the level set by the distortion characteristics of the pre-stage tuning unit 3, the distortion characteristics of the RF amplification unit 18, the distortion characteristics of the post-stage tuning unit 5, and the distortion characteristics of the post-stage variable attenuation unit 19. In this case, the AGC control unit 10 temporarily decreases the attenuation amount of the rear stage variable attenuation unit 19 by a specific level in the second operation region B. Even if the attenuation amount of the rear stage variable attenuation unit 19 is decreased by a specific level, the rear stage variable attenuation unit 19 is set to have an appropriate level of attenuation amount. In the second operation region B, as shown in FIG. 6C, the AGC control unit 10 performs control so that the attenuation amount of the preceding-stage variable attenuation unit 2 is equal to or greater than a specific attenuation amount, Even if the level of the RF input signal rises, control is performed so as to increase the attenuation amount of the preceding-stage variable attenuation unit 2 so that the IF output level becomes a predetermined level. Then, in the third operation region C in which the level of the RF input signal is further increased and the attenuation amount of the preceding stage variable attenuation unit 2 is saturated, as shown in FIG. 6B, the AGC control unit 10 performs the IF output level. Is controlled to increase the amount of attenuation of the rear-stage variable attenuation unit 19 so that becomes a predetermined level.

  Thus, according to the second embodiment of the present invention, the level of the RF input signal is such that the distortion characteristics of the pre-stage tuning section 3, the distortion characteristics of the RF amplification section 18, the distortion characteristics of the post-stage tuning section 5, and the post-stage variable attenuation. In the first operation region A below the level set by the distortion characteristics of the unit 19, the amount of attenuation of the rear stage variable attenuation unit 19 is controlled so that the IF output level is below a predetermined level, and the level of the RF input signal is In the second operation region B exceeding the set level, the attenuation amount of the rear-stage variable attenuation unit 19 is temporarily decreased by a specific level, and the attenuation amount of the front-stage variable attenuation unit 2 is equal to or greater than the specific attenuation amount. Since the output level is controlled to be a predetermined level, it is possible to reduce the level of intermodulation distortion generated in the PIN diode used in the preceding-stage variable attenuating unit 2, and to reduce the sensitivity suppression due to the interference wave. Previous stage variable reduction It is possible to reduce the deterioration in the distortion characteristic in Part 2.

(Embodiment 3)
Next, an AGC circuit of the receiving apparatus according to the third embodiment of the present invention will be described. Since the configuration of the AGC circuit in the third embodiment is the same as that shown in FIG. 1 or FIG. 5, description of the configuration is omitted, and only the operation thereof is shown here based on the configuration shown in FIG. 7 for explanation. In the third embodiment, in order to suppress a rapid fluctuation in the control level when the RF input signal level changes from an increase to a decrease in the first embodiment or the second embodiment, the second operation region B is changed to the second operation region B. The RF input signal level at the time of transition to one operation region A is set to be smaller than the RF input signal level at the time of transition from the first operation region A to the second operation region B.

  First, as shown in FIG. 7A, the IF output level is controlled by the AGC circuit 10 to be equal to or lower than a predetermined level. When the level of the RF input signal exceeds the AGC operation level, the AGC control unit 10 attenuates the amplification gain of the variable gain amplification unit 4 in the first operation region A, as shown in FIG. Control is performed so that the attenuation amount of the unit 2 becomes a constant level. When the level of the RF input signal rises and exceeds the level set by the distortion characteristic of the pre-stage tuning unit 3, the distortion characteristic of the variable gain amplification unit 4, the NF characteristic, or the distortion characteristic of the post-stage tuning unit 5, the AGC In the second operation region B, the control unit 10 temporarily increases the amplification gain of the variable gain amplification unit 4 by a specific level. Further, in the second operation region B, as shown in FIG. 7C, the AGC control unit 10 performs control so that the attenuation amount of the variable attenuation unit 2 is greater than or equal to a specific attenuation amount, and further the RF Even if the level of the input signal rises, control is performed so that the attenuation amount of the variable attenuator 2 is increased so that the IF output level becomes a predetermined level.

  In the second operation region B, when the level of the RF input signal decreases while the AGC control unit 10 is controlling the attenuation amount of the variable attenuation unit 2, the AGC control unit 10 determines that the variable attenuation unit 2 The control for the attenuation amount of the variable attenuation unit 2 is stopped so that the amount is minimized. Further, when the level of the RF input signal decreases and the control by the AGC control unit 10 returns from the second operation region B to the first operation region A, the RF for starting the control for the amplification gain of the variable gain amplification unit 4 is started. The input signal level is set lower than the RF input signal level set by the distortion characteristics of the pre-stage tuning unit 3, the distortion characteristics of the variable gain amplifying unit 4, the NF characteristic, and the distortion characteristics of the post-stage tuning unit 5. When the RF input signal level rises, the AGC control unit 10 stops controlling the attenuation amount of the variable attenuation unit 2, whereby the attenuation amount of the variable attenuation unit 2 returns to the minimum and the variable gain amplification unit 4. This control is started from a low RF input signal level, and the frequency at which the attenuation amount of the variable attenuation unit 2 and the amplification gain of the variable gain amplification unit 4 change rapidly can be suppressed.

  As described above, according to the AGC circuit of the third embodiment of the present invention, the RF input signal level when shifting from the second operation region B to the first operation region A is set to the first operation region A. Since the RF input signal level is set to be smaller than the RF input signal level at the time of shifting from the first operation region B to the second operation region B, the level of the RF input signal depends on the distortion characteristics of the pre-stage tuning unit 3, the distortion characteristics of the variable gain amplification unit 4, and NF When the frequency fluctuates in the vicinity of the level set by the characteristics and the distortion characteristics of the post-stage tuning unit 5, it is possible to suppress the frequency at which the attenuation amount of the variable attenuation unit 2 and the amplification gain of the variable gain amplification unit 4 rapidly change.

  In the above description, the operation has been described based on the configuration shown in FIG. 1, but the same control can be performed for the configuration shown in FIG.

  In the above description of each embodiment, the configuration in which the AGC detection unit 9 is connected to the output of the mixer 6 and the AGC operation is performed with respect to the IF output level has been described as an example. In order to increase the output level of the tuning unit 5 or the selectivity of the AGC operation, the IF output signal is filtered with a steep filter, and the AGC operation is performed on the signal level of other points in the receiving apparatus such as the signal level of the reception channel The present invention can be similarly applied to a configuration for performing AGC operation and a configuration for performing AGC operation using signal levels at a plurality of points inside the receiving apparatus.

  As described above, the receiving apparatus according to the present invention has the effect of reducing the sensitivity suppression due to the jamming wave and thereby reducing the deterioration of the distortion characteristic in the variable attenuator, and the intermodulation distortion due to the strong input. It is useful as a receiving device provided with an AGC circuit in order to suppress the occurrence of noise.

The block diagram of the front end part provided with the AGC circuit of the receiver in the 1st Embodiment of this invention (A) A characteristic diagram for explaining the operation of the AGC circuit in the first embodiment of the present invention, (b) a variable gain operation control diagram of the variable gain amplifier, and (c) an attenuation operation control of the variable attenuator. Diagram Circuit diagram of a general variable attenuator using a PIN diode (A) Voltage-current characteristic diagram of a general variable attenuator using a PIN diode, (b) Attenuation characteristic diagram of a variable attenuator when the current flowing through the PIN diode is changed, (c) A PIN diode Distortion characteristic diagram of the variable attenuation section when changing the flowing current The block diagram of the front end part provided with the AGC circuit of the receiver in the 2nd Embodiment of this invention (A) Characteristic diagram for explaining the operation of the AGC circuit in the second embodiment of the present invention, (b) Attenuation operation control diagram of the rear stage variable attenuation unit, (c) Attenuation operation control of the front stage variable attenuation unit Diagram (A) A characteristic diagram for explaining the operation of the AGC circuit in the third embodiment of the present invention, (b) a variable gain operation control diagram of the variable gain amplifier, and (c) an attenuation operation control of the variable attenuator. Diagram Block diagram of a front-end unit having an AGC circuit of a receiving apparatus in the prior art (A) Characteristic diagram for explaining operation of AGC circuit in prior art, (b) variable gain operation control diagram of variable gain amplifying unit, (c) attenuation operation control diagram of variable attenuating unit

Explanation of symbols

1 RF input terminal 2 Variable attenuation unit (front variable attenuation unit)
DESCRIPTION OF SYMBOLS 3 Front stage tuning part 4 Variable gain amplification part 5 Rear stage tuning part 6 Mixer 7 Oscillator 8 IF output terminal 9 AGC detection part 10 AGC control part 11 Front end part of receiver 12 RF input terminal 13 PIN diode 14 Resistance 15 Voltage input terminal 16 RF output terminal 17 Basic variable attenuator 18 RF amplifier 19 Subsequent variable attenuator 20 Front end of receiver 21 RF input terminal 22 LPF
23 Variable Attenuator 24 RF Amplifier 25 Pre-stage BPF
26 Variable Gain Amplifying Unit 27 Subsequent BPF
28 Mixer 29 Oscillator 30 IF output terminal 31 AGC detection unit 32 AGC control unit 33 Front-end unit of receiver

Claims (3)

  A variable attenuating unit for attenuating the received RF input signal level in a variable amount of attenuation, a variable gain amplifying unit provided at a subsequent stage of the variable attenuating unit for amplifying the input signal level in a variable amplification gain, and the variable attenuating unit And an AGC control unit that controls an amplification gain of the variable gain amplifying unit so that a signal level at a predetermined point is equal to or lower than a predetermined level, and the variable attenuating unit and the variable gain amplifying unit are A first operating region in which the gain of the variable attenuating unit is made constant by changing the amplification gain of the variable gain amplifying unit; and the gain of the variable gain amplifying unit by changing the attenuation of the variable attenuating unit And the second operation region in which the RF input signal level in the second operation region is larger than the RF signal level in the first operation region, and the AGC controller Receiving apparatus for increasing the amplification gain of the variable gain amplifying section at the transition from one operating area to the second operating region.   A pre-stage variable attenuator for attenuating the received RF input signal level in a variable amount of attenuation; a post-stage variable attenuator for attenuating the input signal level in a variable amount of attenuation; An AGC control unit that controls an attenuation amount of the variable attenuation unit and an attenuation amount of the subsequent stage variable attenuation unit so that a signal level at a predetermined point is equal to or lower than a predetermined level, and the front stage variable attenuation unit and the rear stage variable variable The attenuating unit is a first operation region in which the amount of attenuation of the rear stage variable attenuation unit is made constant by changing the amount of attenuation of the rear stage variable attenuation unit, and the amount of attenuation of the front stage variable attenuation unit is changed. Operating in an operation region including a second operation region in which the attenuation amount of the variable attenuation unit is constant, and an RF input signal level in the second operation region is greater than an RF signal level in the first operation region, AG Control unit, a receiving apparatus wherein reducing the attenuation of the post-stage attenuator in the transition from the first operating region to the second operating region.   The RF input signal level when shifting from the second operating region to the first operating region is lower than the RF input signal level when shifting from the first operating region to the second operating region. The receiving apparatus according to claim 1, wherein:

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