JP2007166588A - Automatic gain control apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic gain control apparatus which can make compatible, without using complex processings, both fast tracking ability with respect to input signal variations and target signal quality, when jamming and noise are proper. <P>SOLUTION: When the difference between the absolute value of a differential value of a pre-stage automatic gain control voltage and REF 3 exceeds a predetermined value, that is when the variation of the pre-stage automatic gain control is large, a nonlinear transponder for automatic gain control responses comprising of a1, b1, and c1 is selected. When the difference is the predetermined value or smaller, that is when the variation of the pre-stage automatic gain control is small, a nonlinear transponder for automatic gain control responses comprising a2, b2, and c2 is selected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an automatic gain control apparatus that inputs and processes a signal having a wider bandwidth than an output signal.

  Japanese Patent No. 3086080 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2005-192060 (Patent Document 2) disclose techniques for an automatic gain control apparatus that inputs and processes a signal wider than an output signal. The conventional automatic gain control device disclosed in this document will be outlined with reference to FIGS.

  The automatic gain control device 1 includes a front analog front end 11 and a rear digital front end 34. In the front analog front end 11, a signal in a predetermined frequency band is extracted from the signal input from the RF / IF terminal 12 using the band pass filter 14. The extracted signal includes a non-target signal in addition to the target signal. For this reason, it has a wider band than the latter-stage filter that passes only the target signal. Further, a signal in a predetermined frequency band converted into a signal of a constant level by the AGC amplifier 16 is input to the AD converter 19 via the anti-aliasing filter (low-pass filter for preventing aliasing), and the AD converter 19 is a digital signal quantized.

A signal in a predetermined frequency band converted to a signal of a constant level by the AGC amplifier 16 is also input to the automatic gain control unit 21. The automatic gain control unit 21 is intended to prevent saturation of the signal processing unit by appropriately managing the level of the wideband signal. The automatic gain control unit 21 includes a detector 22, a reference value register (REF 1) 24, a subtracter 26, a non-linear responder (ax ³ + cx) 28, a multiplier 29, and a delay unit 32. The output signal of the automatic gain control unit 21 is input to the AGC amplifier 16 as an AGC control signal.

  On the other hand, the signal converted into a digital signal by the AD converter 19 in the digital front end 34 at the subsequent stage is subjected to quadrature detection by the quadrature converter 50 formed of, for example, a complex coefficient filter, and expressed by the I-axis signal and the Q-axis signal. Converted to a complex signal having a baseband frequency. The signal in the target band converted into a signal of a constant level by the I-side AGC amplifier 52 and the Q-side AGC amplifier 54 is sent to the all complex mixer 60 composed of the multipliers 61 to 64, the subtractor 65, and the adder 66. And output from the automatic gain control device 1 as a baseband frequency complex signal (BB.I, BB.Q).

In addition, the signal in the target band converted into a signal of a certain level by the I-side AGC amplifier 52 and the Q-side AGC amplifier 54 is also input to the automatic gain control unit 70. The automatic gain control unit 70 suppresses an unnecessary band signal so that only a signal in the target band is obtained, and outputs the signal in the target band with a constant value. The automatic gain control unit 70 includes a detector 72, a reference value register (REF 2) 74, a subtractor 76, a non-linear responder (ax ³ + bx ² + cx) 80, a limiter 84, a subtracter 86, and a delay unit 88. The output signal of the automatic gain control unit 70 is input to the I-side AGC amplifier 52 and the Q-side AGC amplifier 54 as an AGC control signal.

  As described above, in the automatic gain control devices of Patent Document 1 and Patent Document 2 shown in FIG. 13, the two automatic gain control units 21 and 70 connected in tandem are configured so that the automatic gain control unit 21 in the preceding stage is a broadband signal. It aims at preventing the saturation of a signal processing part by managing a level appropriately. Further, the automatic gain control unit 70 in the subsequent stage has a two-stage configuration in which an unnecessary band signal is suppressed so that only a signal within the target band is output, and the target band signal is constant and output.

  Here, if the response characteristic of the automatic gain control unit 21 at the previous stage is slow, the tracking at the input signal is not sufficiently followed, so that saturation at the previous stage occurs or a shortage period of gain with respect to the target signal occurs. In order to avoid this, the front-stage automatic gain control unit 21 increases the response speed. However, if the response of the front-stage automatic gain control unit 21 is increased, if the signal level fluctuation other than the target signal is large, a large level with respect to the target signal. Since fluctuations occur, the automatic gain control unit 70 in the subsequent stage is required to have a faster response characteristic to compensate for this.

  That is, when the signal level variation other than the target signal is large, the large level variation with respect to the target signal occurs when the gain of the AGC amplifier 16 varies due to the function of the AGC, This is because the signal level fluctuates without distinction of non-target signals. Therefore, when the signal level of the non-target signal is higher than the target signal, the gain of the AGC amplifier is adjusted according to the non-target signal level so that the AGC keeps the signal level within a predetermined range. Will receive unnecessary level adjustments. For this reason, when the level difference between the level of the non-target signal and the target signal is large, and the level variation of the non-target signal is large, the level variation received by the target signal also increases.

  Automatic gain control is essential when dealing with signals with large level fluctuations because it can avoid distortion due to signal saturation and S / N degradation due to insufficient gain. However, the automatic gain control device having high-speed response characteristics is an amplitude compressor that compresses the amplitude of a signal, and causes a large distortion to the target signal. Here, FIG. 14 shows the BER when π / 4QPSK is added as a target signal to the receiver using the automatic gain control device of Patent Document 1 and Patent Document 2 shown in FIG. FIG. 15 shows the BER when the burst CW is added. 14 and 15 are examples in the case of simulation under the conditions of FIG.

  As described above, since a high-speed response characteristic is required for the subsequent automatic gain control unit, the subsequent automatic gain control unit distorts the target signal, the non-target signal is weak, and deterioration occurs when Eb / N0 is good. Arise. This degradation can be improved by delaying the response of the automatic gain controller at the subsequent stage.To slow down this response, the response characteristic of the previous stage must also be delayed. The followability with respect to fluctuations is reduced.

  Since it is impossible to achieve both the characteristics when the disturbance and noise are good and the tracking ability when the disturbance is strong and the level fluctuation is large, it is necessary to set a response characteristic according to the purpose between the two. Become.

  In order to solve this problem, Japanese Patent Application Laid-Open No. 2004-274210 (Patent Document 3) is based on a method of controlling the gain of an automatic gain control device based on a general output level. The problem is solved by detecting the signal level at the preceding stage only when the signal level detection for automatic gain control at the output of the apparatus cannot cope with the fluctuation of the input signal, such as the external signal level becomes higher than the target signal level.

Japanese Patent No. 3086080 JP-A-2005-192060 JP 2004-274210 A

  As described above, in the background art, in the cited documents 1 and 2, it is impossible to achieve both the characteristic when the disturbance and the noise are good and the followability when the disturbance is strong and the level fluctuation is large. Therefore, it is necessary to set response characteristics according to the purpose. In Cited Document 3, the problem is solved by detecting the signal level in the previous stage only when the signal level detection for automatic gain control at the output of the apparatus cannot cope with the fluctuation of the input signal, but it is very complicated. There is a problem that processing is required.

  The present invention has been made in view of the problems of the background art described above, and an object of the present invention is to use a high-speed follow-up capability with respect to input signal fluctuations, interference, and noise without using complicated processing. To obtain a new and improved automatic gain control apparatus capable of achieving both desired signal quality.

  In order to solve the above-described problems, according to a first aspect of the present invention, there is provided an automatic gain control apparatus that inputs and processes a signal having a wider bandwidth than an output signal. The automatic gain control device (10) of the present invention includes a first signal processing unit (111) including a first automatic gain control unit (111) for controlling a wideband input signal including a target signal band within a certain amplitude range. 100), a second signal processing unit (210) that extracts a target signal from the output of the first signal processing unit, and a second signal that outputs the output of the second signal processing unit with a constant amplitude. A response speed control signal for controlling the response speed of the second automatic gain control section in accordance with the response state of the automatic gain control section (230) and the first automatic gain control section (such as the magnitude of fluctuation). And a response speed control signal generation unit (123) for generating (claim 1).

  In the present invention, a response speed control signal for controlling the response speed of the second automatic gain control section (230) in accordance with the response state (such as the magnitude of fluctuation) of the first automatic gain control section (111). A response speed control signal generation unit (123) for generation is provided. The second automatic gain control unit (230) requires a high-speed response only when a high-speed response is generated in the first automatic gain control unit (previous stage automatic gain control unit) (111). Therefore, the response characteristic of the second automatic gain control unit (the subsequent automatic gain control unit) (230) can be switched according to the response state of the first automatic gain control unit (111). In this way, it is possible to achieve both high-speed followability with respect to input signal fluctuations and simple target signal quality when interference and noise are good by simple processing.

  In the above description, the reference numerals in parentheses attached to the constituent elements are merely shown as examples of the corresponding constituent elements in the following embodiments and drawings for easy understanding. It is not limited to this. The same applies to the following.

  Various application examples of the present invention can be considered, and some application examples are as follows.

  The response speed control signal generator (123) has a predetermined difference between an absolute value of a differential value of the automatic gain control voltage, which is an output of the first automatic gain controller (111), and a predetermined reference value (REF3). When the value is exceeded, it is determined that the fluctuation of the first automatic gain control unit is large, and it is possible to generate a response speed control signal for increasing the response speed of the second automatic gain control unit. (Claim 2).

  Various configurations can be considered for the second automatic gain control unit (230). For example, a first responder for increasing the response speed of the second automatic gain control unit. (238), a second responder (240) for reducing the response speed of the second automatic gain control unit, and the first and second responders according to the response speed control signal. It is possible to adopt a configuration including a switch (242) for switching.

  Alternatively, the second automatic gain control unit (230) holds a response unit (252) for controlling a response speed of the second automatic gain control unit and a high-speed coefficient used in the response unit. A configuration including a high-speed coefficient register (254) and a low-speed coefficient register (256) that holds a low-speed coefficient used in the responder may be employed.

  The second automatic gain control unit (230) continuously changes the response speed according to the response state of the first automatic gain control unit (111) (such as the magnitude of fluctuation) (dynamic Control etc.) (Claim 5). The performance is improved by adopting a configuration in which the response speed of the subsequent stage is changed continuously without switching instantaneously when switching from high speed to low speed. Specifically, for example, in order to avoid the response speed from slowing down even though the response state at the front stage converges rapidly and the response at the rear stage does not converge, the response from the high speed response to the low speed response is performed. It is possible to perform a treatment to smooth the change in response speed when changing to.

  In order to solve the above problems, according to a second aspect of the present invention, there is provided an automatic gain control device including a plurality of second automatic gain control units for one first automatic gain control unit. The That is, in an automatic gain control apparatus that inputs and processes a signal wider than the output signal, a first automatic gain control unit that controls a wideband input signal including a target signal band within a certain amplitude range is provided. A signal processing unit (100 ′), a plurality of second signal processing units (in 200-1, 200-2, 200-3) for extracting a target signal from the output of the first signal processing unit, A second automatic gain control unit (200-1, 200-2, 200-3) provided corresponding to each second signal processing unit and outputting the output of the second signal processing unit with a constant amplitude. And a response speed for generating a response speed control signal for controlling the response speed of each of the second automatic gain control sections in accordance with the response state (such as fluctuation) of the first automatic gain control section. Control signal generator (123) and automatic gain control device provided There is provided (claim 6).

  According to such a configuration, in addition to the effect of the automatic gain control device according to the first aspect of the present invention, it is possible to process signals of different frequencies by including a plurality of second signal processing units. It is. Furthermore, since it can be divided into two stages or multiple stages before and after a large delay element such as a filter, the delay in the automatic gain control loop is small and a high-speed response is possible.

  As for the automatic gain control apparatus according to the second aspect of the present invention, various application examples can be considered in the same manner as the automatic gain control apparatus according to the first aspect of the present invention. -10).

  As described above, according to the present invention, it is possible to achieve both high-speed followability with respect to input signal fluctuation and target signal quality when interference and noise are good by simple processing. Further, other effects of the present invention will be described in the best mode for carrying out the invention described below.

  Hereinafter, preferred embodiments of an automatic gain control device according to the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a receiver using an automatic gain control apparatus according to the first embodiment of the present invention. Also, in the first embodiment, an example of BER characteristics when CW is added as a non-target signal having a frequency close to the target signal frequency is shown in FIG. 2, and an example of BER characteristics when burst CW is added. 3 shows. 2 and 3 are cases in which the simulation conditions shown in FIG. 16 are used.

(Configuration of the first embodiment)
FIG. 1 is a block diagram showing a configuration of an automatic gain control apparatus 10 according to the present embodiment. The configuration of the automatic gain control apparatus 10 according to the present embodiment is roughly divided into an analog front end that processes an analog signal and a digital front end that processes a digital signal. Hereinafter, it demonstrates in order.

(Analog front end 100)
First, the analog front end 100 that processes analog signals will be described.
In FIG. 1, a signal in a predetermined frequency band is extracted from a signal input from the RF / IF terminal 102 using a bandpass filter 104. The extracted signal includes a non-target signal in addition to the target signal. For this reason, it has a wider band than the latter-stage filter that passes only the target signal. The AGC amplifier 106 is a variable gain amplifier for converting the output signal of the bandpass filter 104 into a signal of a certain level. A signal in a predetermined frequency band converted into a signal of a constant level by the AGC amplifier 106 is input to the AD converter 110 via the anti-aliasing filter (low-pass filter for preventing aliasing) 108, and the AD converter 110 It becomes a quantized digital signal.

A signal in a predetermined frequency band that has been converted to a constant level signal by the AGC amplifier 106 is also input to the detector 112 of the AGC control unit 111. The automatic gain control unit 111 is intended to prevent saturation of the signal processing unit by appropriately managing the level of the wideband signal. The automatic gain control unit 111 includes a detector 112, a reference value register (REF 1) 114, a subtracter 116, a non-linear responder (ax ³ + cx) 118, a multiplier 120, and a delay unit 122.

Then, in order to generate a signal for controlling the gain of the AGC amplifier 106, the subtractor 116 subtracts the reference value (REF1) output from the reference value register 114 from the output signal of the detector 112, and the non-linear responder ( ax ³ + cx) 118. The output signal of the non-linear responder 118 is input to the delay unit 122 via the subtracter 120. The subtractor 120 subtracts the output signal of the delay unit 122 from the output signal of the nonlinear responder 118. The output signal of the AGC control unit 111 is input to the AGC amplifier 106 as an AGC control signal that controls the gain of the AGC amplifier 106.

(Response speed control signal generator 123)
The AGC control signal that controls the gain of the AGC amplifier 106 is also input to the differentiation circuit 124 of the response speed control signal generation unit 123 that is a characteristic component of the present embodiment. In the differentiation circuit 124, the absolute value of the differential value of the voltage value of the AGC control signal is calculated. The output signal of the differentiating circuit 124 is compared with a reference value (REF3) output from the reference value register 126 to generate a signal for controlling the gains of an I-side AGC amplifier 212 and a Q-side AGC amplifier 214, which will be described later ( x1-x2 <a?) 128. Specifically, the arithmetic circuit 128 includes a subtracter and a comparator, and an output signal of the differentiation circuit 124 input to the terminal X2 from a reference value (REF3) output from the reference value register 126 input to the terminal X1. (Absolute value of the differential value of the voltage value of the AGC control signal) is subtracted and compared with a predetermined value a.

  The output signal of the arithmetic circuit 128 is input to an AGC control unit 230 in the digital front end 200 described later as a response speed control signal. Then, the AGC control unit 230 comprises a1, b1, and c1 when the difference between the absolute value of the differential value of the automatic gain control voltage at the previous stage and the REF3 exceeds a predetermined value, that is, when the fluctuation of the automatic gain control at the previous stage is large. Select a non-linear transponder with automatic gain control response. Further, when the difference between the absolute value of the differential value of the automatic gain control voltage at the previous stage and the REF3 is equal to or smaller than a predetermined value, that is, when the fluctuation of the automatic gain control at the previous stage is small, the automatic gain control response composed of a2, b2, c2 is nonlinear. Select a transponder. This configuration and operation will be further described later.

(Digital front end 200)
Next, the digital front end 200 for processing digital signals will be described.
The signal converted into a digital signal by the AD converter 110 is subjected to quadrature detection by the quadrature converter 210 including, for example, a complex coefficient filter, and converted into a complex signal having a baseband frequency represented by an I-axis signal and a Q-axis signal. Is done.

  The converted baseband frequency complex signal is band-limited by the I-axis signal in the I-side channel filter (Re) and the Q-axis signal in the Q-side channel filter (Im), thereby being converted into a signal in the target band. The I-axis signal is input to the I-side AGC amplifier 212, and the Q-axis signal is input to the Q-side AGC amplifier 214.

  The I-side AGC amplifier 212 and the Q-side AGC amplifier 214 are variable gain amplifiers for converting the output signals of the I-side channel filter (Re) and the Q-side channel filter (Im) into signals of a certain level. A signal in a target band converted into a signal of a constant level by the I-side AGC amplifier 212 and the Q-side AGC amplifier 214 is transmitted through, for example, the all-complex mixer 220 to a baseband frequency complex signal (BB.I, BB.Q). ) As output from the automatic gain control device 10.

  The full complex mixer 220 is for frequency conversion, and includes multipliers 221, 222, 223, and 224, a subtractor 225, and an adder 226. The real complex local signal (cos) is input from the local signal generator (Local2) to the full complex mixer 220, and the imaginary axial local signal (-sin) is input from the local signal generator. The full complex mixer 220 performs frequency conversion on the complex signal input from the local signal generator so that the frequency becomes zero or near zero, and outputs a complex signal.

The signal in the target band converted into a signal of a constant level by the I-side AGC amplifier 212 and the Q-side AGC amplifier 214 is also input to the detector 232 of the AGC control unit 230.
The automatic gain control unit 230 is for suppressing an unnecessary band signal so that only a signal in the target band is obtained, and outputting the signal in the target band with a constant value. The automatic gain control unit 230 includes a detector 232, a reference value register (REF2) 234, a subtractor 236, a non-linear responder (a1 ³ + b1x ² + c1x) 238, a non-linear responder (a2x ³ + b2x ² + c2x) 240, a switch 242, It comprises a limiter 244, a subtracter 246, and a delayer 248.

  The detector 232 adds the square values of the I-axis signal and the Q-axis signal of the input signal in the target band in order to generate signals for controlling the gains of the I-side AGC amplifier 212 and the Q-side AGC amplifier 214. At the same time, by calculating the square root and integrating the square root, fluctuations in the output signals of the I-side AGC amplifier 212 and the Q-side AGC amplifier 214 are detected.

Then, in order to generate signals for controlling the gains of the I-side AGC amplifier 212 and the Q-side AGC amplifier 214, the output signal of the detector 232 is used as a reference value (REF2) output from the reference value register 234 in the subtractor 236. Is subtracted and input to the non-linear responder (a1x ³ + b1x ² + c1x) 238 and the non-linear responder (a2x ³ + b2x ² + c2x) 240.

  The switch 242 selects either the output signal of the nonlinear responder 238 or the output signal of the nonlinear responder 240 based on the response speed control signal from the arithmetic circuit 128 in the analog front end 100. The switch 242 is an automatic gain control response composed of a1, b1, and c1 when the difference between the absolute value of the differential value of the automatic gain control voltage of the previous stage and the REF3 exceeds a predetermined value, that is, when the fluctuation of the automatic gain control of the previous stage is large. Select a nonlinear transponder. Further, when the difference between the absolute value of the differential value of the automatic gain control voltage at the previous stage and the REF3 is equal to or smaller than a predetermined value, that is, when the fluctuation of the automatic gain control at the previous stage is small, the automatic gain control response composed of a2, b2, c2 is nonlinear. Select a transponder. Here, when a non-linear responder of automatic gain control response consisting of coefficient values of a1, b1, and c1 is selected, the response speed of the subsequent stage is selected as a non-linear responder of automatic gain control response consisting of a2, b2, and c2. It is set faster than the response speed.

  The output signal selected by the switch 242 (either the output signal of the non-linear responder 238 or the output signal of the non-linear responder 240) is a limiter 244 provided to suppress an excessive signal level below a predetermined level. Is input. The output signal of the limiter 244 is input to the delay unit 248 via the subtracter 246. The subtractor 246 subtracts the output signal of the delay unit 248 from the output signal of the limiter 244. The output signal of the AGC control unit 230 is input to the I-side AGC amplifier 212 and the Q-side AGC amplifier 214 as an AGC control signal for controlling the gains of the I-side AGC amplifier 212 and the Q-side AGC amplifier 214.

(Operation of the first embodiment)
In the first embodiment, when the difference between the absolute value of the differential value of the automatic gain control voltage at the previous stage and the REF3 exceeds a predetermined value, that is, when the fluctuation of the automatic gain control unit 111 at the previous stage is large, from a1, b1, and c1 The automatic gain control response non-linear responder 238 is selected. Further, when the difference between the absolute value of the differential value of the automatic gain control voltage at the previous stage and the REF3 is equal to or smaller than a predetermined value, that is, when the fluctuation of the automatic gain control 111 at the previous stage is small, the automatic gain control response composed of a2, b2, c2 The non-linear responder 240 is selected. Here, when a non-linear responder of automatic gain control response consisting of coefficient values of a1, b1, and c1 is selected, the response speed of the subsequent stage is selected as a non-linear responder of automatic gain control response consisting of a2, b2, and c2. It is set faster than the response speed.

  The response corrector may be a simple coefficient unit. However, by making the response characteristic non-linear, it is easy to achieve both high-speed response characteristics and low distortion.

(Effects of the first embodiment)
As described above, according to the present embodiment, when the difference between the absolute value of the differential value of the automatic gain control voltage at the previous stage and the REF3 exceeds a predetermined value, that is, when the fluctuation of the automatic gain control unit 111 at the previous stage is large, a1 , B1, and c1 are selected as a non-linear responder having an automatic gain control response. Further, when the difference between the absolute value of the differential value of the automatic gain control voltage at the previous stage and the REF3 is equal to or smaller than a predetermined value, that is, when the fluctuation of the automatic gain control unit 111 at the previous stage is small, the automatic gain control response composed of a2, b2, and c2. Select a nonlinear transponder. In this way, it is possible to achieve both high-speed followability with respect to input signal fluctuation and target signal quality when interference and noise are good without using complicated processing. Since the change information of the previous stage can be obtained with a digital value of 0 or 1, the increase in the interfaces of the subsequent stage and the previous stage in this embodiment is slight. In this embodiment, an example of BER characteristics when CW is added as a non-target signal having a frequency close to the target signal frequency is shown in FIG. 2, and an example of BER characteristics when burst CW is added is shown in FIG. 2 and 3 are cases in which the simulation conditions shown in FIG. 16 are used.

<Second Embodiment>
FIG. 4 shows a receiver using the automatic gain control apparatus according to the second embodiment of the present invention. Further, in the second embodiment, FIG. 5 shows an example of BER characteristics when CW is added as a non-target signal, and FIG. 6 shows an example of BER characteristics when burst CW is added. 5 and 6 are cases in which the simulation conditions shown in FIG. 16 are used.

(Configuration of Second Embodiment)
FIG. 4 is an explanatory diagram showing the automatic gain control device 20 according to the present embodiment. Since the present embodiment is an application of the first embodiment, in FIG. 4, components having substantially the same functional configuration as those of the first embodiment (FIG. 1) are denoted by the same reference numerals. A duplicate description will be omitted by attaching.

As shown in FIG. 4, the automatic gain control device 20 according to the present embodiment is replaced with nonlinear responders 238 and 240 that are components of the automatic gain control device 10 (FIG. 1) according to the first embodiment. A nonlinear responder (ax ³ + bx ² + cx) 252 is provided, and coefficient registers 254, 256, and 258 are further provided. The coefficient register 254 is a register that holds the coefficients a1, b1, and c1 (hereinafter referred to as C1) described in the first embodiment. The coefficient register 254 is a register that holds the coefficients a2, b2, and c2 (hereinafter referred to as C2) described in the first embodiment. The non-linear responder 252 is a circuit that calculates ax ³ + bx ² + cx using any coefficient held in the coefficient registers 254 and 256. The non-linear responder 252 uses Cdec stored in the coefficient register 258 as a lower limit, and reduces the coefficient.

(Operation of Second Embodiment)
The operation of this embodiment will be described with reference to the state transition diagram shown in FIG.
In the present embodiment, when the difference between the absolute value of the differential value of the automatic gain control voltage in the previous stage and REF3 exceeds a predetermined value, the nonlinear responder for the automatic gain control response uses the coefficient of C1 (S1). When the difference between the absolute value of the differential value of the automatic gain control voltage in the previous stage and the REF3 is less than the predetermined value from the state exceeding the predetermined value, the non-linear responder 252 of the automatic gain control response uses the value of Cdec with C2 as the lower limit. The coefficient is reduced (S1 → S2 → S3). Here, when the difference between the absolute value of the differential value of the automatic gain control voltage in the previous stage and the REF3 exceeds the predetermined value again, the value of C1 is used (S2 or S3 → S1).

(Effect of 2nd Embodiment)
As described above, according to the present embodiment, it is possible to respond faster than the conventional automatic gain control by satisfying both low distortion and followability. In the conventional automatic gain control apparatus, since a distortion occurs when the response speed is increased, the response is set to be slower than the automatic gain control apparatus according to the present embodiment. For this reason, as shown in FIG. 8, the target signal cannot be observed between the interference waves added in bursts at the ADC output, and the predetermined signal level is not reached even at the output of the automatic gain control device. On the other hand, in the present embodiment, which shows the response waveform in FIG. 9, the signal level is not large, but the target signal can be observed at the ADC output although it is not a large level due to the high-speed tracking capability even between the interference waves. The previous stage gain increases to the level. A target signal controlled to a target level can be observed at the output of the automatic gain control device.

  Further, a great improvement can be obtained by making a slight modification to the first embodiment.

<Third Embodiment>
FIG. 10 shows a receiver using an automatic gain control apparatus according to the third embodiment of the present invention. FIG. 11 shows an example of BER characteristics when a burst CW is added as a non-target signal in the third embodiment. FIG. 11 shows a case where the simulation conditions shown in FIG. 16 are used.

(Configuration of Third Embodiment)
FIG. 10 is an explanatory diagram showing an automatic gain control device 30 according to the present embodiment. Since this embodiment is an application of the second embodiment, in FIG. 10, components having substantially the same functional configuration as those of the second embodiment (FIG. 4) are denoted by the same reference numerals. A duplicate description will be omitted by attaching.

  As shown in FIG. 10, the automatic gain control device 30 according to the present embodiment is different from the automatic gain control device 20 (FIG. 4) according to the second embodiment in the analog front end 100 and the digital front end 200. Changes have been made to both. This will be described below.

  The analog front end 100 includes an AD converter 130 instead of the reference value register (REF3) 126 and the arithmetic circuit 128 of the second embodiment. The AD converter 130 receives the output signal from the differentiating circuit 124 and outputs an analog response state signal to the digital front end 200. Since a general receiver is equipped with an AD converter for the control voltage of analog automatic gain control in order to know the received signal level, the digital unit converts the automatic gain control voltage of the analog unit after digital conversion. By differentiating and obtaining the absolute value, an increase in special interface can be avoided.

  On the other hand, the digital front end 200 employs a configuration for dealing with the analog response state signal. In addition to the configuration of the second embodiment, the digital front end 200 of this embodiment includes a multiplier 260, a switch 262, a comparator 264, a subtractor 266, a delay device 268, and an adder 270. Prepare.

  The multiplier 260 receives the analog response state signal that is the output signal of the AD converter 130 in the analog front end 100 and the coefficients a1, b1, and c1 held by the coefficient register (for high speed) 254, and performs multiplication processing. Do. An output signal of the multiplier 260 is input to the switch 262 and the comparator 264. The switch 262 receives an output signal from the multiplier 260 and a signal obtained by subjecting the coefficient Cdec held in the coefficient register 258 to a predetermined delay process, and switches between them according to the output signal from the comparator 264. . The subtractor 266 receives the coefficient Cdec held in the coefficient register 258 and the output signal of the delay unit 268 and performs subtraction processing.

  A signal output by switching by the switch 262 is output to the delay unit 268. The output signal of the delay unit 268 is input to the comparator 264, the subtracter 266, and the adder 270. The comparator 264 receives the output signal (X1) of the multiplier 260 and the output signal (X2) of the delay unit 268 and compares them. An output signal that is a comparison result of the comparator 264 is input to the switch 262.

  The adder 270 receives the output signal of the delay unit 268 and the coefficients a2, b2, and c2 held by the coefficient register (for low speed) 256, and performs addition processing. The output signal of the adder 270 is input to the nonlinear responder 252.

(Operation of Third Embodiment)
The coefficient of the non-linear responder of the automatic gain control response in the subsequent stage is determined by setting the coefficient (a2, b2, c2) at the low speed to the minimum value and the coefficient at the high speed (a1) according to the absolute value of the differential value of the automatic gain control voltage in the previous stage. , B1, and c1) are set to the maximum values and are varied between them. In addition, as in the improvement from the first embodiment to the second embodiment, the response speed of the preceding stage is rapidly converged and the response speed of the latter stage is not converged, but the response speed becomes slow. In order to avoid such a situation, a process of smoothing a change in response speed when changing from a high-speed response to a low-speed response is performed. In this embodiment, the value obtained by multiplying the high-speed coefficient and the response state of the previous stage is compared with the value one sample before, and when the value is smaller than the value one sample before, Cdec is subtracted from the value one sample before. This is realized by updating the value as a control value for controlling the coefficient of the nonlinear responder.

(Effect of the third embodiment)
In the configuration of this embodiment, when the subsequent stage is digital processing as shown in FIG. 10, the AD converter 130 is required to obtain the previous stage information, but a general receiver knows the received signal level. Is equipped with an AD converter for the control voltage of the analog automatic gain control. After the analog gain automatic gain control voltage is digitally converted, it is differentiated by the digital part to obtain an absolute value. An increase in is avoided.

<Fourth Embodiment>
FIG. 12 shows a receiver using an automatic gain control apparatus according to the fourth embodiment of the present invention.

(Configuration of Fourth Embodiment)
FIG. 12 is an explanatory diagram showing an automatic gain control device 40 according to the present embodiment. In addition, since this embodiment is an application of the first to third embodiments, in FIG. 12, components having substantially the same functional configuration as those of the first to third embodiments are the same. The duplicated explanation is omitted by attaching the reference numeral.

  In this embodiment, a plurality of target signals are processed at the same time. A plurality of digital units are connected in parallel to the same analog unit, and each digital unit processes signals of different frequencies.

  In the example shown in FIG. 12, the analog front end 100 ′ is connected to the response speed control signal generator 123 (differential circuit 124, reference value register (REF3) from the analog front end 100 of the configuration of the first embodiment (FIG. 1). ) 126 and the arithmetic circuit 128). And the case where the response speed control signal generation part 123 is shared and used by each digital front end 200-1, 200-2, 200-3 is shown. Here, each digital front end 200-1, 200-2, 200-3 has the same configuration as the digital front end 200 in the first embodiment. That is, in the automatic gain control device 40 according to the present embodiment, when there is one digital front end, the configuration is the same as the configuration of the automatic gain control device 10 according to the first embodiment (FIG. 1).

  Note that the configuration shown in FIG. 12 is merely an example, and based on the configuration of the second embodiment (FIG. 4) or the configuration of the third embodiment (FIG. 10) It is also possible to employ a configuration in which a plurality of digital units are connected in parallel. Also, with respect to the number of digital parts, FIG. 12 shows three cases, but the number of digital parts is not limited to this, and may be two, or may be four or more.

(Effect of the fourth embodiment)
As described above, according to the present embodiment, a high-speed response is required for the subsequent automatic gain control unit only when a high-speed response is generated in the previous automatic gain control unit. In the automatic gain control apparatus described in the first to third embodiments, the response characteristic of the subsequent automatic gain control unit is switched according to the response state of the previous automatic gain control unit. It is possible to achieve both high-speed tracking and target signal quality when interference and noise are good.

  In the automatic gain control device disclosed in Japanese Patent Application Laid-Open No. 2004-274210 (Patent Document 3), if the signal transmission delay between the input and the output is large, the control speed of the gain control of the input side variable gain amplifier is slowed down. However, in the automatic gain control device according to this embodiment, it can be divided into two stages or multiple stages before and after a large delay element such as a filter. The delay in the automatic gain control loop is small, and a high-speed response is possible.

  The preferred embodiment of the automatic gain control device according to the present invention has been described above with reference to the accompanying drawings, but the present invention is not limited to such an example. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the technical idea described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

  For example, in the above embodiment, the non-linear responder has been described as an example of the responder for controlling the response speed of the automatic gain control unit. However, the responder of the present invention is not limited to the non-linear one but is linear. It may be a thing.

  The present invention can be used in an automatic gain control apparatus that inputs and processes a signal having a wider bandwidth than the output signal.

It is explanatory drawing which shows the structure of the automatic gain control apparatus concerning 1st Embodiment. It is explanatory drawing which shows the example of the BER characteristic of the target signal at the time of adding CW as a non-target signal to the receiver provided with the automatic gain control apparatus of 1st Embodiment. It is explanatory drawing which shows the example of the BER characteristic of the target signal at the time of adding the burst CW as a non-target signal to the receiver provided with the automatic gain control apparatus of 1st Embodiment. It is explanatory drawing which shows the structure of the automatic gain control apparatus concerning 2nd Embodiment. It is explanatory drawing which shows the example of the BER characteristic of the target signal at the time of adding CW as a non-target signal to the receiver provided with the automatic gain control apparatus of 2nd Embodiment. It is explanatory drawing which shows the example of the BER characteristic of the target signal at the time of adding the burst CW as a non-target signal to the receiver provided with the automatic gain control apparatus of 2nd Embodiment. It is explanatory drawing which shows the response control transition of the digital part of FIG. It is explanatory drawing which shows the time-axis response characteristic in a graph when burst CW is added as a non-target signal to a prior art example. It is explanatory drawing which shows the time-axis response characteristic with a graph when burst CW is added as a non-target signal to 2nd Embodiment. It is explanatory drawing which shows the structure of the automatic gain control apparatus concerning 3rd Embodiment. It is explanatory drawing which shows the characteristic when burst CW is added as a non-target signal to 3rd Embodiment with a graph. It is explanatory drawing which shows the structure of the receiver concerning 4th Embodiment. It is explanatory drawing which shows the structure of the receiver using the conventional automatic gain control apparatus. It is explanatory drawing which shows the example of the BER characteristic of the target signal at the time of adding CW as a non-target signal of the conventional automatic gain control apparatus. It is explanatory drawing which shows the example of the BER characteristic of the target signal at the time of adding the burst CW as a non-target signal of the conventional automatic gain control apparatus. It is explanatory drawing which shows simulation conditions in a table | surface.

Explanation of symbols

10, 20, 30, 40 Automatic gain control device 100 Analog front end 102 RF / IF terminal 104 Band pass filter 106 AGC amplifier 108 Anti-aliasing filter (AAF)
110 AD converter (ADC)
111 AGC Control Unit 112 Detector 114 Reference Value Register 116 Subtractor 118 Nonlinear Response Device 120 Subtractor 122 Delay Device 123 Response Speed Control Signal Generation Unit 124 Differentiation Circuit 126 Reference Value Register 128 Operation Circuit 130 AD Converter 200 Digital Front End 210 Orthogonal transformer 212 I-side AGC amplifier 214 Q-side AGC amplifier 220 Full complex mixer 230 AGC controller 232 Detector 234 Reference value register 236 Subtractor 238 Non-linear responder 240 Non-linear responder 242 Switch 244 Limiter 246 Subtractor 248 Delay device 252 Nonlinear transponder 254 coefficient register (for high speed)
256 coefficient register (for low speed)
258 Coefficient register 260 Multiplier 262 Switch 264 Comparator 266 Subtractor 268 Delay device 270 Adder

Claims (10)

In an automatic gain control apparatus that inputs and processes a signal having a wider bandwidth than the output signal,
A first signal processing unit including a first automatic gain control unit that controls a wide-band input signal including a target signal band within a certain amplitude range;
A second signal processing unit for extracting a target signal from the output of the first signal processing unit;
A second automatic gain control unit that outputs the second signal processing unit with a constant amplitude, and
A response speed control signal generating unit that generates a response speed control signal for controlling a response speed of the second automatic gain control unit according to a response state of the first automatic gain control unit;
An automatic gain control device comprising: The response speed control signal generator is
When the difference between the absolute value of the differential value of the automatic gain control voltage, which is the output of the first automatic gain control unit, and a predetermined reference value exceeds a predetermined value, the fluctuation of the first automatic gain control unit is large. The automatic gain control apparatus according to claim 1, wherein a response speed control signal for increasing the response speed of the second automatic gain control unit is generated. The second automatic gain controller is
A first responder for increasing the response speed of the second automatic gain control unit;
A second responder for lowering a response speed of the second automatic gain control unit;
A switch for switching the first and second responders in response to the response speed control signal;
The automatic gain control device according to claim 1 or 2, further comprising: The second automatic gain controller is
A responder for controlling a response speed of the second automatic gain control unit;
A high-speed coefficient register for holding a high-speed coefficient used in the responder;
A low-speed coefficient register for holding a low-speed coefficient used in the responder;
The automatic gain control device according to claim 1 or 2, further comprising: The second automatic gain controller is
The automatic gain control device according to claim 1 or 2, wherein a response speed is continuously changed according to a response state of the first automatic gain control unit. In an automatic gain control apparatus that inputs and processes a signal having a wider bandwidth than the output signal,
A first signal processing unit including a first automatic gain control unit that controls a wide-band input signal including a target signal band within a certain amplitude range;
A plurality of second signal processing units for extracting a target signal from the output of the first signal processing unit;
A second automatic gain control unit provided corresponding to each of the second signal processing units and outputting the output of the second signal processing unit with a constant amplitude;
A response speed control signal generator for generating a response speed control signal for controlling the response speed of each of the second automatic gain controllers according to the response state of the first automatic gain controller;
An automatic gain control device comprising: The response speed control signal generator is
When the difference between the absolute value of the differential value of the automatic gain control voltage, which is the output of the first automatic gain control unit, and a predetermined reference value exceeds a predetermined value, the fluctuation of the first automatic gain control unit is large. The automatic gain control apparatus according to claim 6, wherein a response speed control signal for increasing the response speed of the second automatic gain control unit is generated. Each of the second automatic gain controllers is
A first responder for increasing the response speed of the second automatic gain control unit;
A second responder for lowering a response speed of the second automatic gain control unit;
A switch for switching the first and second responders in response to the response speed control signal;
The automatic gain control device according to claim 6 or 7, further comprising: Each of the second automatic gain controllers is
A responder for controlling a response speed of the second automatic gain control unit;
A high-speed coefficient register for holding a high-speed coefficient used in the responder;
A low-speed coefficient register for holding a low-speed coefficient used in the responder;
The automatic gain control device according to claim 6 or 7, further comprising: Each of the second automatic gain controllers is
8. The automatic gain control apparatus according to claim 6, wherein a response speed is continuously changed according to a response state of the first automatic gain control unit.

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