JP4112808B2 - Receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a receiving apparatus, and more particularly to means for removing distortion of a reproduction signal caused by the response speed of an AGC circuit when improving signal distortion when a plurality of channel signals are simultaneously input to an AGC circuit.
[0002]
[Prior art]
In recent years, with the development of digital circuit technology, there are an increasing number of examples in which functions realized by analog circuits are realized using digital circuits. When a programmable device such as a DSP (digital signal processor) is used as a digital circuit, the function is realized by software, so the characteristics can be easily corrected and changed, and there is no characteristic variation or deterioration over time, or Advantages such as no adjustment are obtained.
[0003]
In the field of mobile communications such as digital mobile phones, the transition to the digital circuit is progressing, and as an ultimate example, a software defined radio that realizes most of the communication functions by software has been proposed. Details are described in the following documents, so the explanation is omitted (Joe Mitola, The software radio architecture, IEEE Communication magazine, May 1995 vol.33, No.5). However, in reality, wideband amplifiers, mixers, local oscillators, or high-speed A / D (analog / digital) converters as required in the above documents are difficult to realize at present, so the high-frequency part and IF part The following configuration for analog processing has been proposed.
[0004]
FIG. 5 is a functional block diagram showing a configuration example of a conventional receiving apparatus. The receiving apparatus shown in this example guides the output signal of the amplifier 103 connected to the antenna 102 via the RF bandpass filter 101 to the mixer 104 and converts it to a predetermined frequency by the output signal of the local signal oscillator 105. After that, the A / D converter 108 is configured to be supplied via an IF band pass filter 106 and an AGC (Automatic Gain Control) circuit 107.
[0005]
The receiving apparatus shown in this example functions as follows. That is, a high-frequency analog signal including a plurality of channel signals received via the antenna 102 is subjected to removal of unnecessary components by the RF bandpass filter 101 having a required bandwidth, and after being amplified by the amplifier 103, the local signal The frequency is converted to a predetermined IF frequency by the oscillator 105 and the mixer 104 and supplied to the IF pass filter 106.
[0006]
The IF pass filter 106 has a wideband characteristic that allows a plurality of channel signals related to various modulation schemes, which are realized by changing the software of the DSP in the demodulation processing unit in the subsequent stage, not shown, to pass through. After the unnecessary components are removed again here, the amplification level g of the AGC circuit is controlled based on the control signal 107a so that the maximum level is constant within the dynamic range of the A / D converter 108. At the same time, it is converted into a digital signal by the A / D converter 108 and supplied to the channel separation / demodulation processing unit, where it is digitally processed by the DSP.
[0007]
FIG. 6 is a conceptual diagram for explaining a composite waveform related to a plurality of channel signals at the input of the AGC circuit 107. This drawing shows an example in which two channel signals having the same amplitude level are input for the sake of simplicity. Has frequencies f1, f2 respectively the two signals s1, s2 (FIG. 6 (a) ~ (c) ), but these signals amplitude becomes addition is increased at the timing to be superimposed in phase, reverse since the amplitude becomes subtraction is reduced at the timing to be superimposed in phase, the superimposed signal of the two signals s1, s2 has a waveform amplitude maximum value varies temporally, as shown in FIG. 6 (d).
[0008]
Therefore, such a receiving apparatus has the following problems. In other words, when the superimposed signal as shown in Fig. 6 (d) is input to the AGC circuit, the AGC circuit functions to keep the maximum signal level constant within the dynamic range of operation of the A / D converter in the subsequent stage. To do. However, in order to improve frequency utilization efficiency, for example, when the number of channel signals increases to about 100 channels, the superimposed signal level becomes equal to or higher than the saturation level (operation dynamic range) of the AGC circuit, and the waveform is clipped (the tip of the waveform is The phenomenon that is cut). FIG. 7 is a diagram showing a waveform example of the superimposed signal in the AGC circuit output in such a case. As shown in this figure, the superimposed signal has a waveform distortion, and as a result, there is a problem that frequency information (signal information) is lost.
[0009]
In order to solve such a problem, the following receiver has been proposed by the present applicant. FIG. 8 is a functional block diagram showing a configuration example of a receiving apparatus proposed for improving the waveform distortion. The receiving apparatus shown in this example guides the output signal of the amplifier 13 connected to the antenna 12 through the RF bandpass filter 11 to the mixer 14 and converts it to a predetermined frequency by the output signal of the local signal oscillator 15. Then, the signal is supplied to a multiplier 19 via an IF bandpass filter 16 having an after-mentioned bandwidth, an AGC circuit 17, and a first A / D converter 18. Further, the control signal 17a in the AGC circuit 17 is calculated through the second A / D converter 20 to calculate the reciprocal of the amplification of the AGC circuit, and is supplied to the amplification reciprocal calculation unit 21 connected to the multiplier 19. Configured as follows.
[0010]
The receiving apparatus shown in this example functions as follows. That is, after the high frequency analog signal including a plurality of channel signals received via the antenna 12 is removed by the RF band pass filter 11 having a required bandwidth and amplified by the amplifier 13, the local signal oscillator 15 and The frequency is converted to a predetermined IF frequency by the mixer 14 and supplied to the IF pass filter 16.
[0011]
The band characteristics of the IF pass filter 16 are set so that all of a plurality of channel signals related to various modulation schemes realized by changing the DSP software in the demodulation processing unit in the subsequent stage (not shown) can be passed. After removing unnecessary signal components again here, the amplification level g of the AGC circuit 17 is controlled based on the control signal 17a so that the maximum level is constant within the dynamic range of the A / D converter, The digital signal is converted by the A / D converter 18 and supplied to the multiplier 19.
[0012]
As described above, the control signal 17a of the AGC circuit 17 controls the amplification degree g of the AGC circuit, and thus has information related to the amplification degree g. The control signal 17a is used as the second A / C. After conversion to a digital signal through the D converter 20, the amplification degree reciprocal calculation unit 21 calculates the reciprocal 1 / g related to the amplification degree g of the AGC circuit 17 based on the information of the amplification degree g, and the multiplier 19 Supply.
The signal Sin at the input of the AGC circuit 17 is g · Sin at the output of the AGC circuit, and when the number of reception channel signals is large, the distortion waveform is as shown in FIG. Since multiplication is performed, undistorted Sin is reproduced at the output of the multiplier 19, and therefore, loss of signal information can be prevented.
[0013]
[Problems to be solved by the invention]
However, the conventional receiving apparatus as described above has the following problems. In other words, the gain g of the AGC circuit always changes according to the level of the input signal Sin, but since it is an analog circuit, the gain g is changed after the control signal 17a is input to the amplification part of the AGC circuit, and the output is constant. It takes a predetermined time to reach the value due to the response speed of the AGC circuit. Therefore, the amplification degree g of the AGC circuit recognized by the amplification degree reciprocal calculation unit 21 based on digital processing and the actual amplification degree g of the AGC circuit are different in the value within a predetermined time related to the response speed, For this reason, the component related to the amplification degree g of the AGC circuit cannot be completely canceled in the output of the multiplier 19, so that there is a problem that the input signal Sin cannot be completely reproduced and signal distortion remains.
The present invention has been made to solve the above-described problems related to the conventional receiver, and the amplification factor g of the AGC circuit and the amplification factor g recognized by the inverse amplification factor calculation unit due to the response speed of the AGC circuit. An object of the present invention is to provide a receiving apparatus capable of removing signal distortion caused by the difference between the two.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 of the receiving apparatus according to the present invention provides:
A filter through which a plurality of channel signals received via an antenna can pass;
An AGC circuit to which a signal from the filter is input;
A first A / D converter for converting an output signal from the AGC circuit into a digital signal and outputting the digital signal;
A second A / D converter for converting a control signal for controlling the amplification degree of the AGC circuit into a digital signal and outputting the digital signal;
An amplification degree reciprocal calculation unit that receives a digital signal from the second A / D converter and calculates and outputs a reciprocal related to the amplification degree of the AGC circuit;
A multiplier that reproduces a plurality of channel signals by multiplying an output signal from the first A / D converter and an inverse of the amplification degree output from the amplification degree inverse number calculation unit;
In a receiving device comprising:
The AGC circuit obtains an average value for every predetermined time from the output signal of the AGC circuit, and outputs a control signal averaging means for outputting the average value for the previous period from the current time as the control signal for the predetermined time by Yes,
Holding the amplification degree of the AGC circuit at a constant value every predetermined time;
Holding a reciprocal related to the amplification degree at a constant value every predetermined time;
It is characterized by.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on the illustrated embodiment. FIG. 1 is a functional block diagram showing a configuration example of a receiving apparatus according to the present invention. The receiving apparatus shown in this example guides the output signal of the amplifier 13 connected to the antenna 12 through the RF bandpass filter 11 to the mixer 14 and converts it to a predetermined frequency by the output signal of the local signal oscillator 15. Then, the signal is supplied to a multiplier 19 via an IF bandpass filter 16 having an after-mentioned bandwidth, an AGC circuit 17, and a first A / D converter 18. Further, the AGC circuit 17 generates a control signal 17a for controlling the amplification degree g by the control signal averaging unit 17b, and supplies the control signal 17a to the amplification unit 17c and the AGC circuit through the second A / D converter 20 The reciprocal of the amplification degree is calculated and supplied to the amplification degree reciprocal calculation unit 21 connected to the multiplier 19.
[0016]
The receiving apparatus shown in this example functions as follows. That is, after the high frequency analog signal including a plurality of channel signals received via the antenna 12 is removed by the RF band pass filter 11 having a required bandwidth and amplified by the amplifier 13, the local signal oscillator 15 and The frequency is converted to a predetermined IF frequency by the mixer 14 and supplied to the IF pass filter 16.
[0017]
The band characteristics of the IF pass filter 16 are set so that all of a plurality of channel signals related to various modulation schemes realized by changing the DSP software in the demodulation processing unit in the subsequent stage (not shown) can be passed. After removing unnecessary signal components again here, the amplification level g of the AGC circuit 17 is controlled based on the control signal 17a so that the maximum level is constant within the dynamic range of the A / D converter, The digital signal is converted by the A / D converter 18 and supplied to the multiplier 19.
[0018]
As described above, the control signal 17a of the AGC circuit 17 controls the amplification degree g of the AGC circuit, and thus has information related to the amplification degree g. The control signal 17a is used as the second A / C. After conversion to a digital signal through the D converter 20, the amplification degree reciprocal calculation unit 21 calculates the reciprocal 1 / g related to the amplification degree g of the AGC circuit 17 based on the information of the amplification degree g, and the multiplier 19 Supply.
The signal Sin at the input of the AGC circuit 17 is g · Sin at the output of the AGC circuit, and when the number of reception channel signals is large, the distortion waveform is as shown in FIG. Since multiplication is performed, a signal Sin having no distortion is reproduced at the output of the multiplier 19, and therefore, loss of signal information can be prevented.
[0019]
At that time, in the control signal averaging unit 17b, the output signal of the AGC circuit 17 is averaged every predetermined time to be a constant value as will be described later, and this is used as the control signal 17a. After the time, the amplification g of the AGC circuit 17 and the amplification g recognized by the amplification degree reciprocal calculation unit 21 coincide with each other, and the signal distortion that occurs when the values do not coincide with each other can be removed. .
[0020]
Hereinafter, the operation of the control signal averaging unit 17b will be described in detail. First, FIG. 2 is a diagram for explaining an average value of signals. The average value of the signal f (t) is defined as a value obtained by integrating the signal f (t) with respect to time T and dividing the value with respect to time T as shown in the lower part of the figure. This physical meaning is that the area S of the signal f (t) is obtained by integration of the time T, and the height (average value) is determined from a rectangle having the same area as the length T. Therefore, the average value of the signal can be obtained by using an integration circuit.
[0021]
FIG. 3 is a diagram illustrating a configuration example of an integration circuit using an operational amplifier. The integrating circuit is a low-pass filter in principle, and operates to extract a DC component (average value) of the signal f (t). In the integrating circuit shown in this example, the integrated value of the input signal Vin is output as Vout. Details are described in, for example, the Electrical Engineering Pocketbook, p240, edited by the Institute of Electrical Engineers of Japan, Ohmsha (issued on Dec. 10, 1995), and will not be described here.
[0022]
The control signal averaging unit 17b is configured by using the integration circuit, integrates the output signal of the AGC circuit 17 every predetermined time T, and outputs the average value thereof as the control signal 17a. FIG. 4 is a timing chart illustrating the operation of the control signal averaging unit 17b. FIGS. 9A and 9B show an input signal (AGC circuit output signal g · Sin) and an output signal (control signal 17a) to the control signal averaging unit 17b, respectively. The control signal averaging unit 17b integrates the input signal every predetermined time T, and outputs the average value for a predetermined period. As the control signal 17a, the integration of the previous period determined at the present time is performed. The value is used as a control signal. This is because, for example, if the current time is in the period of T to 2T, the integrated value in this period has not yet been determined, so the average value already determined in the period of 0 to T is used.
[0023]
As described above, since the receiving apparatus according to the present invention operates, the AGC circuit input signal generated by the difference between the amplification degree of the AGC circuit due to the response speed of the AGC circuit and the amplification degree recognized by the inverse amplification degree calculation unit. Signal distortion related to incomplete reproduction of Sin can be removed.
【The invention's effect】
In the present invention, as described above, the inverse 1 / g of the amplification degree of the AGC circuit is separately calculated from the control signal of the AGC circuit, and this is multiplied by the output signal of the A / D converter disposed in the subsequent stage of the AGC circuit. Thus, since the input signal (Sin) of the AGC circuit is reproduced at the output of the A / D converter, there is no waveform distortion related to the signal level control of the AGC circuit regardless of the number of reception channels, and therefore the signal information (frequency information) This is very effective in realizing a receiving apparatus that can reproduce a plurality of channel signals that are not missing.
In addition, since a signal held at a constant value every predetermined time is used as the control signal, the AGC circuit input signal (Sin) in the A / D converter output generated due to the response speed of the AGC circuit is not detected. This is very effective in realizing a receiving apparatus that can remove signal distortion related to complete reproduction.
[Brief description of the drawings]
FIG. 1 is a functional block diagram showing an embodiment of a receiving apparatus according to the present invention. FIG. 2 is a diagram for explaining an average value of signals. FIG. 3 is a control signal averaging unit of the receiving apparatus according to the present invention. FIG. 4 is a timing chart for explaining the operation of the control signal averaging unit of the receiving apparatus according to the present invention. FIG. 5 is a configuration example of a conventional receiving apparatus. Functional block diagram [FIG. 6] A diagram for explaining the concept of the signal waveform at the input of the AGC circuit. [FIG. 7] A diagram for explaining the concept of the signal waveform at the output of the AGC circuit. [FIG. Functional block diagram showing a configuration example of a receiving device [Explanation of symbols]
11. RF band pass filter 12 Antenna 13 RF amplifier 14 Mixer 15 Local signal oscillator 16 IF band pass filter 17 AGC circuit 17a Control signal 17b Control signal averaging ... Amplification unit 18... First A / D converter 19.. Multiplier 20.. Second A / D converter 21.

Claims (1)

A filter through which a plurality of channel signals received via an antenna can pass;
An AGC circuit to which a signal from the filter is input;
A first A / D converter for converting an output signal from the AGC circuit into a digital signal and outputting the digital signal;
A second A / D converter for converting a control signal for controlling the amplification degree of the AGC circuit into a digital signal and outputting the digital signal;
An amplification degree reciprocal calculation unit that receives a digital signal from the second A / D converter and calculates and outputs a reciprocal related to the amplification degree of the AGC circuit;
A multiplier that reproduces a plurality of channel signals by multiplying an output signal from the first A / D converter and an inverse of the amplification degree output from the amplification degree inverse number calculation unit;
In a receiving device comprising:
The AGC circuit obtains an average value for every predetermined time from the output signal of the AGC circuit, and outputs a control signal averaging means for outputting the average value for the previous period from the current time as the control signal for the predetermined time by Yes,
Holding the amplification degree of the AGC circuit at a constant value every predetermined time;
Holding a reciprocal related to the amplification degree at a constant value every predetermined time;
A receiving device.

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