Receiver

Abstract

To provide a receiver that can prevent damage to devices due to over-input and has good responsiveness.SOLUTION: A receiver includes: an external AGC 3 that attenuates gain of a received signal before digital conversion according to a signal level of a digitally converted received signal; an external AGC correction unit 5 that corrects the gain of the received signal to a value before attenuation by multiplying the attenuated received signal by the inverse of an amount of attenuation by the external AGC 3 at timing of cancelling the attenuation; a channel filter 6 that removes unnecessary frequency components of the corrected received signal; and an internal AGC 7 that adjusts the gain of the received signal that has passed through the channel filter 6 into a predetermined range.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a receiver that extracts a desired audio frequency signal from a received signal to reproduce audio. [Background technology]

[0002] Receivers that play back audio have traditionally been equipped with an automatic gain control circuit (internal AGC) that adjusts the gain and output audio to an appropriate range according to the received signal level. However, if there is an excessive input to the receiver's antenna input, devices such as the power amplifier section may be damaged or become saturated. For this reason, a separate automatic gain control circuit (external AGC) is required to monitor the received power on the input side and attenuate the received signal. In this case, for example, as shown in Figure 2, a configuration is considered in which the received power is monitored in the digital section and the received signal is attenuated in the stage before the digital section.

[0003] However, because it has two automatic gain control circuits and exhibits an operation and behavior in which the subsequent internal AGC converges after the previous external AGC converges, it takes time for convergence, resulting in a decrease and degradation of response performance. Particularly in the above configuration, when the received power increases instantaneously, the signal captured by the RF_ADC (analog / digital converter) saturates and overflows before the external AGC converges, causing the power detection value in the external AGC to be estimated low, resulting in gradual attenuation of the received signal. As a result, the convergence and response of the subsequent internal AGC slows down, and responsiveness deteriorates.

[0004] To solve such problems, a technique is known in which the time constants of the internal AGC and the external AGC are set to different values ​​(see, for example, Patent Document 1). For example, the time constant of the internal AGC is set to be large and the time constant of the external AGC is set to be small, thereby suppressing overshoot and undershoot of the output signal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 53-72441 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technology of Patent Document 1 simply sets the time constants of the internal AGC and the external AGC to different values, which is insufficient to suppress the influence of the external AGC at the upstream stage on the internal AGC at the downstream stage, and may result in reduced responsiveness.

[0007] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a receiver that is capable of preventing damage to a device due to excessive input and has good responsiveness. [Means for solving the problem]

[0008] In order to solve the above problem, the invention of claim 1 includes a first automatic gain control circuit that attenuates a gain of a received signal before digital conversion in accordance with a signal level of the digitally converted received signal, a gain correction unit that corrects the gain of the received signal to a value before attenuation by multiplying the attenuated and digitally converted received signal by the reciprocal of the amount of attenuation by the first automatic gain control circuit at a timing to cancel the attenuation, a channel filter that removes unnecessary frequency components of the corrected received signal, and a second automatic gain control circuit that adjusts the gain of the received signal that has passed through the channel filter within a predetermined range. the gain correction unit cancels the attenuation by adjusting a delay and multiplying the reciprocal so that an influence of the first automatic gain control circuit is suppressed in the second automatic gain control circuit; The receiver is characterized in that Effect of the Invention

[0010] According to the invention of claim 1, since the gain of the received signal is attenuated by the first automatic gain control circuit, it is possible to prevent damage to the device even if there is an excessive input. Also, since the gain of the received signal attenuated by the first automatic gain control circuit in the preceding stage is corrected to the gain before attenuation by the gain correction unit, the influence of the first automatic gain control circuit in the subsequent stage is suppressed and reduced. Moreover, since the correction is performed at a timing that cancels out the attenuation, it is possible to further suppress and reduce the influence of the first automatic gain control circuit. As a result, the convergence time in the second automatic gain control circuit becomes faster independently without depending on the first automatic gain control circuit, and responsiveness is improved.

[0011] In addition, since the gain correction unit multiplies the attenuated received signal by the reciprocal of the attenuation amount by the first automatic gain control circuit, it is possible to correct the attenuation of the received signal. Moreover, since it is only necessary to multiply by the reciprocal of the attenuation amount, it is possible to simplify the configuration.

[0012] According to the invention of claim 2, since the delay is adjusted and the reciprocal is multiplied, it becomes possible to cancel the attenuation more appropriately. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic block diagram showing a receiver according to an embodiment of the present invention; [Diagram 2] FIG. 1 is a schematic block diagram showing a conventional receiver equipped with an internal AGC and an external AGC. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the present invention will be described based on the illustrated embodiment.

[0015] 1 is a schematic block diagram showing a configuration of a receiver 1 according to an embodiment of the present invention. The receiver 1 is a device that extracts a desired audio frequency signal from a received signal to reproduce audio, and mainly includes an A / D conversion unit (RF_ADC) 2, an external AGC (first automatic gain control circuit) 3, a digital down converter (DDC) 4, an external AGC correction unit (gain correction unit) 5, a channel filter 6, an internal AGC (second automatic gain control circuit) 7, and a demodulation unit 8.

[0016] The A / D conversion unit 2 is an analog / digital converter that converts an analog received signal received by an antenna and input into a digital signal.

[0017] The external AGC 3 is an automatic gain control circuit that attenuates the gain of the received signal before digital conversion according to the signal level of the received signal digitally converted by the A / D conversion unit 2, and includes an analog variable attenuator 31 disposed upstream of the A / D conversion unit 2. That is, it detects the signal level and intensity of the received signal output from the A / D conversion unit 2, and outputs an attenuation amount according to this signal level to the variable attenuator 31. The received signal received by the antenna is attenuated by this attenuation amount by the variable attenuator 31 and input to the A / D conversion unit 2, thereby preventing the output signal from being saturated. Here, the attenuation amount output from the external AGC 3 to the variable attenuator 31 is also output to the external AGC correction unit 5 described later.

[0018] The digital down-converter 4 is a converter that reduces the frequency and sampling rate of the received signal output from the A / D conversion unit 2, thereby ensuring processing time in the channel filter 6 and the like.

[0019] The external AGC correction unit 5 is a circuit unit that corrects the gain of the attenuated received signal to the value before attenuation by multiplying the attenuated received signal by the reciprocal of the attenuation by the external AGC 3 at the timing to cancel the attenuation by the external AGC 3. That is, a correction value that is the reciprocal of the attenuation transmitted from the external AGC 3 is referenced from the inverse table 51 in chronological order and transmission order. For example, when the attenuation from the external AGC 3 is -1 dB, an amplitude correction value of 1.122 equivalent to +1 dB is output from the inverse table 51.

[0020] Then, the received signal output from the digital down-converter 4 is sequentially multiplied by the correction value output from the inverse table 51 by the multiplier 53, thereby amplifying the level of the received signal from the digital down-converter 4 and correcting the attenuation. At this time, the correction value is multiplied while delaying by the delay circuit 52 so that the signal is amplified at a timing that cancels out the attenuation caused by the external AGC 3. That is, the correction value is multiplied so that the timing signal portion attenuated by the external AGC 3 is amplified and corrected while delaying and adjusting by the delay circuit 52 only the control delay of the variable attenuator 31 and the signal delay by the A / D conversion unit 2 and the digital down-converter 4. In this way, the reciprocal of the attenuation amount is multiplied at a timing that cancels out the attenuation caused by the external AGC 3, thereby restoring the gain of the received signal to the state before attenuation.

[0021] The channel filter 6 is a filter that removes unnecessary frequency components of the received signal corrected by the external AGC correction unit 5. For example, by configuring it with a filter that has a characteristic in which the gain drops sharply in high and low frequency bands, the unnecessary frequency components are removed from the received signal and only the frequency components necessary for reception remain.

[0022] The internal AGC 7 is an automatic gain control circuit that adjusts the gain of the received signal that has passed through the channel filter 6 within a predetermined range. That is, in order to stabilize the level of the sound reproduced from a speaker (not shown), the output level is increased or decreased according to the signal level from the channel filter 6. Specifically, like a conventional automatic gain control circuit, the signal level and intensity of the received signal output from the channel filter 6 is detected, and the level of the received signal from the channel filter 6 is adjusted by an attenuator (multiplier) according to this signal level.

[0023] The demodulation unit 8 is a demodulator that demodulates the received signal output from the internal AGC 7 into an audio signal, and the audio signal demodulated by this demodulation unit 8 is output and played from a speaker via a digital / analog converter (not shown) or the like.

[0024] In the receiver 1 configured as described above, the gain of the received signal is attenuated by the external AGC 3, so that damage to the device can be prevented even if there is an excessive input. In addition, the level of the received signal attenuated by the external AGC 3 in the previous stage is corrected by the external AGC correction unit 5 to cancel out the attenuation, so that the influence of the external AGC 3 in the subsequent internal AGC 7 is suppressed and reduced. Moreover, by adjusting the timing of the correction, it is possible to further suppress and reduce the influence of the external AGC 3. As a result, the convergence time of the internal AGC 7 becomes faster independently without depending on the external AGC 3, and responsiveness is improved.

[0025] Moreover, in the external AGC correction unit 5, it becomes possible to correct the level of the received signal by multiplying the received signal attenuated by the external AGC 3 by the reciprocal of the attenuation amount. Since it is only necessary to multiply by the reciprocal of the attenuation amount, it is possible to simplify the configuration.

[0026] Although the embodiment of the present invention has been described above, the specific configuration is not limited to the above embodiment, and even if there are design changes and the like within the scope of the gist of the present invention, they are included in the present invention. [Explanation of symbols]

[0027] 1 Receiver 2 A / D conversion section 3 External AGC (first automatic gain control circuit) 4 Digital Down Converter 5 External AGC correction section (gain correction section) 51 Reverse Table 52 Delay Circuit 6 Channel Filter 7 Internal AGC (second automatic gain control circuit) 8 Demodulation section

Claims

[Claim 1] a first automatic gain control circuit for attenuating a gain of a received signal before digital conversion in accordance with a signal level of the digitally converted received signal; a gain correction unit that corrects the gain of the received signal to a value before attenuation by multiplying the attenuated and digitally converted received signal by the reciprocal of the amount of attenuation by the first automatic gain control circuit at a timing to cancel the attenuation; a channel filter for removing unnecessary frequency components of the corrected received signal; a second automatic gain control circuit that adjusts the gain of the received signal that has passed through the channel filter within a predetermined range; Equipped with the gain correction unit cancels the attenuation by adjusting a delay and multiplying the reciprocal so that an effect of the first automatic gain control circuit is suppressed in the second automatic gain control circuit; 23. A receiver comprising:

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