JP3609320B2 - Angle demodulator, demodulation characteristic correction apparatus, and recording medium - Google Patents

Description

【００４６】
あるいは、波形が既知のテスト用変調波を生成する外部の装置が、このテスト用変調波を、信号処理部２２の制御に従って、図示しない伝送路を経由してＦＭ復調部１の入力端に供給し、信号処理部２２が、この結果Ａ／Ｄ変換部２１より供給されたディジタル信号が表す値を複数記憶した上、記憶した値を用い、最小二乗法等の手法を用いて、当該近似用関数を求めるようにしてもよい。
【００４７】
Ｄ／Ａ変換部２３は、上述のサンプリング用発振器が生成するサンプリング信号に従って、自己の出力端に、自己の入力端にもっとも新しく供給されたディジタル信号が示す値を有するアナログ信号を、アナログ形式で表された補正後の復調信号として、このＦＭ復調器の出力端へと出力する。
【００４８】
また、図２の構成の補正部２は、図３に示すように、テーブル記憶部２４を備えていてもよい。
テーブル記憶部２４は、ＲＯＭ（Ｒｅａｄ Ｏｎｌｙ Ｍｅｍｏｒｙ）等より構成されており、Ａ／Ｄ変換部２１より供給されるディジタル信号が表す値の候補と、この値をＦＭ復調部１の復調特性を表す関数の逆関数（又は当該逆関数を近似する任意の関数）に代入した値とを、互いに対応付けて記憶する。そして、自己が記憶する値を、信号処理部２２の指示に従って出力する。
【００４９】
補正部２が図３に示す構成を有しているとき、信号処理部２２が補正後の復調信号の値を求めるために実行する処理は、例えば、信号処理部２２が、Ａ／Ｄ変換部２１より供給されたディジタル信号が表す値をキーとして、テーブル記憶部２４が記憶する値を検索し、キーとした値に対応付けられた値を索出する処理であればよい。この場合、索出された値が、補正後の復調信号の値となる。
【００５０】
更に、ＦＭ復調部１も、ＤＳＰ及び／又はＣＰＵから構成されていてもよい。ＦＭ復調部１がＤＳＰ及び／又はＣＰＵから構成されている場合、このＦＭ復調器は、例えば図４に示す構成を有していればよい。
【００５１】
図４の構成のＦＭ復調器は、図示するように、Ａ／Ｄ変換部３１と、Ｄ／Ａ変換部３４と、ＦＭ復調部３２及び信号処理部３３の機能を行うＤＳＰ及び／又はＣＰＵとより構成される。
このうちＡ／Ｄ変換部３１及びＤ／Ａ変換部３４は、図２あるいは図３におけるＡ／Ｄ変換部２１及びＤ／Ａ変換部２３と実質的に同一のものである。
【００５２】
Ａ／Ｄ変換部３１は、復調する対象のＦＭ変調波を、図示しないサンプリング用発振器が発生するサンプリング信号に従ってサンプリングしてディジタル信号に変換し、ＦＭ復調部３２へと供給する。
【００５３】
ＦＭ復調部３２は、Ａ／Ｄ変換部３１より供給されたディジタル形式のＦＭ変調波を復調し、復調により得られるディジタル形式の未補正の復調信号を、信号処理部３３に供給する。
【００５４】
信号処理部３３は、図２の信号処理部２２と実質的に同一の処理を行うことにより、ＦＭ復調部３２より供給されたディジタル形式の未補正の復調信号が表す値を、ＦＭ復調部３２の復調特性を表す関数の逆関数に代入した値を求める。そして、求められた補正後の復調信号の値を表すディジタル信号を生成し、ディジタル形式で表された補正後の復調信号として、Ｄ／Ａ変換部３４に供給する。
【００５５】
Ｄ／Ａ変換部３４は、Ａ／Ｄ変換部３１のサンプリングのタイミングを決定している上述のサンプリング信号に従って、信号処理部３３からもっとも新しく供給されたディジタル信号が示す値を有するアナログ信号を、アナログ形式で表された補正後の復調信号として出力する。
【００５６】
また、図４の構成のＦＭ復調器は、例えば図５に示すように、図３のテーブル記憶部２４と実質的に同一のテーブル記憶部３５を備えていてもよい。
ただし、テーブル記憶部３５は、ＦＭ復調部３２より供給されるディジタル信号が表す値の候補と、この値をＦＭ復調部３２の復調特性を表す関数の逆関数（又は当該逆関数を近似する任意の関数）に代入した値とを、互いに対応付けて記憶するものとする。
【００５７】
図５の構成のＦＭ復調器においては、信号処理部３３が補正後の復調信号の値を求めるために実行する処理は、例えば、信号処理部３３が、ＦＭ復調部３２より供給されたディジタル信号が表す値をキーとして、テーブル記憶部３５が記憶する値を検索し、キーとした値に対応付けられた値を補正後の復調信号の値として索出する処理であればよい。
【００５８】
なお、このＦＭ復調器がディジタル形式のＦＭ変調波を外部から取得するものである場合、Ａ／Ｄ変換部３１は不要であり、また、ディジタル形式の補正後の復調信号を出力するものとする場合、Ｄ／Ａ変換部３４は不要である。
【００５９】
以上、この発明の実施の形態にかかるＦＭ復調器を説明したが、この発明にかかる角度復調器及び復調特性補正装置は、専用のシステムによらず、通常のコンピュータシステムを用いて実現可能である。例えば、Ａ／Ｄ変換器及びＤ／Ａ変換器を備えるパーソナルコンピュータに、上述の動作を実行するためのプログラムを格納した媒体（フロッピーディスク、ＣＤ−ＲＯＭ等）から該プログラムをインストールすることにより、上述の処理を実行するＦＭ復調器を構成することができる。
【００６０】
また、例えば、通信ネットワークの掲示板（ＢＢＳ）に該プログラムを掲示し、これをネットワークを介して配信してもよく、また、該プログラムを表す信号により搬送波を変調し、得られた変調波を伝送し、この変調波を受信した装置が変調波を復調して該プログラムを復元するようにしてもよい。
そして、このプログラムを起動し、ＯＳの制御下に、他のアプリケーションプログラムと同様に実行することにより、上述の処理を実行することができる。
【００６１】
なお、ＯＳが処理の一部を分担する場合、あるいは、ＯＳが本願発明の１つの構成要素の一部を構成するような場合には、記録媒体には、その部分を除いたプログラムを格納してもよい。この場合も、その記録媒体には、コンピュータが実行する各機能又はステップを実行するためのプログラムが格納されているものとする。
【００６２】
【発明の効果】
以上説明したように、この発明によれば、復調出力の歪みが軽減される角度復調器及び復調特性補正装置が実現される。
また、この発明によれば、復調器に変更を加えることなく当該復調器の復調出力の歪みを軽減する復調特性補正装置が実現される。
【図面の簡単な説明】
【図１】この発明の実施の形態にかかるＦＭ復調器の基本構成を示すブロック図である。
【図２】図１のＦＭ復調器の変形例の基本構成を示すブロック図である。
【図３】図２のＦＭ復調器の変形例の基本構成を示すブロック図である。
【図４】図１のＦＭ復調器の変形例の基本構成を示すブロック図である。
【図５】図４のＦＭ復調器の変形例の基本構成を示すブロック図である。
【図６】クワドラチャ復調器の基本構成を示すブロック図である。
【符号の説明】
１、３２ ＦＭ復調部
２ 補正部
２１、３１ Ａ／Ｄ変換部
２２、３３ 信号処理部
２３、３４ Ｄ／Ａ変換部
２４、３５ テーブル記憶部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an angle demodulator, and more particularly to an angle demodulator with little distortion in demodulated output.
[0002]
[Prior art]
A quadrature demodulator is used as a demodulator for demodulating an FM (Frequency Modulation) modulated wave. As shown in FIG. 6, the quadrature demodulator includes, for example, a multiplier 101, a phase shifter 102, and a low-pass filter 103.
[0003]
Assume that the value v ₁ (t) at the time t of the FM modulated wave to be demodulated by the quadrature demodulator of FIG. At this time, the phase shifter 102 of the quadrature demodulator in FIG. 6 generates, for example, a phase shift signal in which the value v ₂ (t) at time t takes the value shown on the right side of Equation 2.
Where A ₀ is the amplitude of the FM modulated wave, ω ₀ is the frequency of the carrier wave, S (t) is the value of the original signal at time t, M is the maximum frequency shift, and Δt is the amount of time delay by the phase shifter 102 It is.
[0004]
[Expression 1]
v ₁ (t) = A ₀ · cos [(ω ₀ · t) + {M · Φ (t)}]
(Where Φ (t) is a value obtained by definite integration of S (t) from 0 to t)
[0005]
[Expression 2]
v ₂ (t) = A ₀ · sin [(ω ₀ · t) + {M · Φ (t−Δt)}]
[0006]
Then, the phase shifter 102 supplies the phase shift signal to the multiplier 101, and the multiplier 101 determines that the value at time t is {v ₁ (t) · v from the FM modulated wave to be demodulated and the phase shift signal. ₂ (t)} is generated that is substantially proportional to the product signal. The low-pass filter 103 removes a component having a frequency corresponding to the sum of the frequency of the FM modulated wave to be demodulated and the frequency of the phase-shifted signal from the product signal generated by the multiplier 101, and generates a demodulated signal.
[0007]
The value R (t) of the demodulated signal at time t is substantially proportional to the value indicated by the right side of Equation 3.
[0008]
[Equation 3]
^{_{R (t) = - (A}} 0 2/2) · [sin {M · S (t)}]
[0009]
[Problems to be solved by the invention]
The quadrature demodulator can be realized with a simple configuration regardless of whether the FM modulated wave to be demodulated is an analog signal or a digital signal.
However, the demodulated signal output from the quadrature demodulator is theoretically a signal proportional to the original FM-modulated signal (that is, obtained by ideally demodulating the FM modulated wave), as is apparent from Equation 3. The range that can be regarded as linear operation (linear operation range) is limited. Therefore, when the frequency shift of the FM modulated wave to be demodulated is large and wider than the linear operation range of the quadrature demodulator, the distortion rate of the demodulated signal increases.
[0010]
As a technique for solving this problem, a technique using an FM demodulator having a linear demodulation characteristic in place of the quadrature demodulator can be considered. However, such an FM demodulator has a complicated configuration.
[0011]
As another method for solving this problem, for example, there is a method disclosed in JP-A-5-175733.
The method disclosed in Japanese Patent Laid-Open No. 5-175733 is a value obtained by dividing the value of the demodulated signal generated by the quadrature demodulator by a predetermined constant or a value obtained by squaring the input signal level of the FM modulated wave. This is a technique for correcting the demodulation characteristics by obtaining a value obtained by substituting a signal having λ into the arc sine function.
[0012]
However, if the quadrature demodulator is not operating ideally, the demodulated signal will not be a signal proportional to the sine of the FM-modulated original signal, so the value of the demodulated signal at time t is not necessarily the above-mentioned value. It is not proportional to the value of R (t). For this reason, when the technique of Japanese Patent Laid-Open No. 5-175733 is performed using a quadrature demodulator that is not operating ideally, the value of the demodulated signal after correction is proportional to the original signal that has been FM-modulated. The problem of not becoming.
[0013]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an angle demodulator and a demodulation characteristic correction apparatus in which distortion of demodulation output is reduced.
Another object of the present invention is to provide a demodulation characteristic correction apparatus that reduces distortion of the demodulation output of the demodulator without changing the demodulator.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, an angle demodulator according to a first aspect of the present invention includes:
Demodulation means for generating an uncorrected demodulated signal by demodulating the angle-modulated wave supplied to the self;
Output correcting means for acquiring the uncorrected demodulated signal from the demodulating means, generating a signal having a predetermined value associated with the acquired value of the uncorrected demodulated signal, and outputting the signal as a corrected demodulated signal And comprising
The value of the corrected demodulated signal state, and are not to approximate the value of the ideal demodulated signal obtained by ideally demodulating the angle modulated wave,
The demodulator obtains a test signal having a known waveform, and generates a test demodulated signal by demodulating the test signal,
The output correction means includes
Obtaining the test demodulated signal and using the value of the test demodulated signal, a correction function that associates the value of the uncorrected demodulated signal with the value of the ideal demodulated signal is approximated by a polynomial of a predetermined order Means for determining an approximation function;
Means for calculating a result obtained by substituting the value of the uncorrected demodulated signal into the approximation function, and generating and outputting a signal indicating the calculation result as the corrected demodulated signal,
It is characterized by that.
[0015]
According to such an angle demodulator, even when the uncorrected demodulated signal does not become the original signal or a signal proportional to the sine thereof, the value of the corrected demodulated signal approximates the value of the ideal demodulated signal. . That is, distortion of the uncorrected demodulated signal is reduced.
[0016]
By approximating the correction function with a polynomial, the output correction means calculates the value of the corrected demodulated signal without the need for complicated calculations, so the configuration of the angle demodulator becomes simple, The process of calculating the corrected demodulated signal value also becomes faster.
[0017]
The angle modulator may further include means for generating the test signal.
[0018]
The demodulating means may be a quadrature demodulating circuit. Since the quadrature demodulator circuit has a simple configuration, the configuration of the angle demodulator is simplified if the demodulating means is configured by a quadrature demodulator circuit.
[0019]
A demodulation characteristic correction apparatus according to the second aspect of the present invention is
Input means for acquiring the uncorrected demodulated signal from an external demodulator that generates an uncorrected demodulated signal by demodulating the angle-modulated wave supplied thereto;
Correction output means for generating a signal having a predetermined value associated with the value of the uncorrected demodulated signal acquired by the input means, and outputting the signal as a corrected demodulated signal,
The value of the corrected demodulated signal state, and are not to approximate the value of the ideal demodulated signal obtained by ideally demodulating the angle modulated wave,
The correction output means includes
The demodulator obtains a test demodulated signal generated by demodulating the test signal having a known waveform, and uses the value of the test demodulated signal to determine the value of the uncorrected demodulated signal. Means for determining an approximation function for approximating a correction function associated with an ideal demodulated signal value by a polynomial of a predetermined order;
Means for calculating a result obtained by substituting the value of the uncorrected demodulated signal into the approximation function, and generating and outputting a signal indicating the calculation result as the corrected demodulated signal,
It is characterized by that.
[0020]
According to such a demodulation characteristic correction apparatus, even when the uncorrected demodulated signal does not become the original signal or a signal proportional to the sine thereof, the value of the corrected demodulated signal approximates the value of the ideal demodulated signal. Become. That is, distortion of the uncorrected demodulated signal is reduced.
Further, such a demodulation characteristic correction apparatus reduces distortion of an uncorrected demodulated signal without changing an external demodulator.
[0021]
By approximating the correction function with a polynomial, the correction output means calculates the value of the corrected demodulated signal without the need for complicated calculations, so that the configuration of the demodulation characteristic correction device is simplified. The process of calculating the corrected demodulated signal value also becomes faster.
[0023]
A computer-readable recording medium according to the third aspect of the present invention is
Computer
Demodulation means for generating an uncorrected demodulated signal by demodulating the angle-modulated wave supplied to the self;
Output correcting means for acquiring the uncorrected demodulated signal from the demodulating means, generating a signal having a predetermined value associated with the acquired value of the uncorrected demodulated signal, and outputting the signal as a corrected demodulated signal When,
A computer-readable recording medium storing a program for causing the program to function,
The value of the corrected demodulated signal state, and are not to approximate the value of the ideal demodulated signal obtained by ideally demodulating the angle modulated wave,
The demodulator obtains a test signal having a known waveform, and generates a test demodulated signal by demodulating the test signal,
The output correction means includes
Obtaining the test demodulated signal and using the value of the test demodulated signal, a correction function that associates the value of the uncorrected demodulated signal with the value of the ideal demodulated signal is approximated by a polynomial of a predetermined order Means for determining an approximation function;
Means for calculating a result obtained by substituting the value of the uncorrected demodulated signal into the approximation function, and generating and outputting a signal indicating the calculation result as the corrected demodulated signal,
It is characterized by that.
[0024]
A computer that executes a program recorded on such a recording medium uses the value of the corrected demodulated signal as the value of the ideal demodulated signal even when the uncorrected demodulated signal does not become the original signal or a signal proportional to the sine thereof. Is corrected to an approximation. That is, distortion of the uncorrected demodulated signal is reduced.
[0025]
A computer-readable recording medium according to the fourth aspect of the present invention provides
Computer
Input means for acquiring the uncorrected demodulated signal from an external demodulator that generates an uncorrected demodulated signal by demodulating the angle-modulated wave supplied thereto;
Correction output means for generating a signal having a predetermined value associated with the value of the uncorrected demodulated signal acquired by the input means, and outputting the signal as a corrected demodulated signal;
A computer-readable recording medium storing a program for causing the program to function,
The value of the corrected demodulated signal state, and are not to approximate the value of the ideal demodulated signal obtained by ideally demodulating the angle modulated wave,
The correction output means includes
The demodulator obtains a test demodulated signal generated by demodulating the test signal having a known waveform, and uses the value of the test demodulated signal to determine the value of the uncorrected demodulated signal. Means for determining an approximation function for approximating a correction function associated with an ideal demodulated signal value by a polynomial of a predetermined order;
Means for calculating a result obtained by substituting the value of the uncorrected demodulated signal into the approximation function, and generating and outputting a signal indicating the calculation result as the corrected demodulated signal,
It is characterized by that.
[0026]
A computer that executes a program recorded on such a recording medium uses the value of the corrected demodulated signal as the value of the ideal demodulated signal even when the uncorrected demodulated signal does not become the original signal or a signal proportional to the sine thereof. Is corrected to an approximation. That is, distortion of the uncorrected demodulated signal is reduced.
In addition, a computer that executes a program recorded in such a recording medium reduces distortion of an uncorrected demodulated signal without changing an external demodulator.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an angle demodulator according to an embodiment of the present invention will be described by taking an FM (Frequency Modulation) demodulator as an example.
FIG. 1 shows an example of the configuration of an FM demodulator according to an embodiment of the present invention.
As shown in the figure, this FM demodulator includes an FM demodulator 1 and a corrector 2.
[0028]
The FM demodulator 1 is composed of, for example, a quadrature demodulator having substantially the same configuration as that shown in FIG. 6, and includes an input end and an output end. The FM demodulator 1 demodulates the FM modulated wave supplied to its input terminal, and outputs a demodulated signal obtained by demodulation (hereinafter referred to as an uncorrected demodulated signal) from its own output terminal.
[0029]
The value of the uncorrected demodulated signal output from the FM demodulator 1 at time t is theoretically proportional to the value R (t) indicated by the right side of Equation 3. However, the value of the uncorrected demodulated signal output from the FM demodulator 1 does not necessarily take a value proportional to the value of R (t), and has a predetermined distortion according to the characteristics of the quadrature demodulator constituting the FM demodulator 1. Receive.
[0030]
Hereinafter, the time t of the uncorrected demodulated signal output by the FM demodulator 1 when the value of the FM modulated wave supplied to the input terminal of the FM demodulator 1 at the time t is v ₁ (t) described above. Let the actual value of be represented as Q {S (t)}. (Hereinafter, the function Q {S (t)} will be referred to as a function representing the demodulation characteristics of the FM demodulator 1).
[0031]
The correction unit 2 includes a function calculation circuit and the like, and includes an input end and an output end. The correction unit 2 corrects an uncorrected demodulated signal supplied to its input end, and generates a signal (after correction) Demodulated signal) is output from its own output terminal.
Assuming that the value supplied to the input terminal of the correction unit 2 at time t is f (t), the corrected demodulated signal output from the output terminal of the correction unit 2 is the value g (t) expressed at time t. Is the value shown on the right side of Equation 4. However, Q ⁻¹ (β) is an inverse function of the function Q (α) (where α and β are variables), and is specified in advance based on previously measured demodulation characteristics of the FM demodulator 1. Yes.
[0032]
[Expression 4]
g (t) = Q ⁻¹ {f (t)}
[0033]
When an FM modulated wave is supplied from the outside to the input end of the FM demodulator (that is, the input end of the FM demodulator 1), the FM demodulator 1 demodulates the FM modulated wave supplied to its own input end. An uncorrected demodulated signal is generated and output.
If the value of the FM modulated wave supplied to the input end of this FM demodulator is substantially equal to the above-mentioned v ₁ (t), the value of the uncorrected demodulated signal at time t is Q {S ( t)}.
[0034]
The correction unit 2 generates and outputs a corrected demodulated signal by correcting the uncorrected demodulated signal supplied to its input terminal. If the value of the uncorrected demodulated signal at time t is substantially equal to Q {S (t)}, the value of the demodulated signal after correction output from the output terminal of the correction unit 2 at time t is S (t ) Substantially equal.
[0035]
By performing the above-described operation, the FM demodulator can generate a time when the value at the time t of the FM modulated wave supplied to the input terminal of the FM demodulator is substantially equal to the above-described v ₁ (t). A demodulated signal whose value at t is substantially equal to S (t) is output.
[0036]
The configuration of the FM demodulator is not limited to the above.
For example, the FM demodulator includes a device that performs an arbitrary process on an input signal to be supplied to the FM demodulator 1 and supplies the processed input signal to the input end of the FM demodulator 1. Also good.
[0037]
Further, the configuration of the correction unit 2 is arbitrary, and does not necessarily need to be configured from a function arithmetic circuit. Therefore, for example, as shown in FIG. 2, the correction unit 2 includes an A / D (Analog-to-Digital) conversion unit 21, a signal processing unit 22, a D / A (Digital-to-Analog) conversion unit 23, and It may be configured.
[0038]
The A / D converter 21 of the corrector 2 shown in FIG. 2 samples the uncorrected demodulated signal supplied from the FM demodulator 1 according to a sampling signal generated by a sampling oscillator (not shown) and converts it into a digital signal. To the signal processing unit 22.
[0039]
The signal processing unit 22 includes a CPU (Central Processing Unit) and / or a DSP (Digital Signal Processor). The signal processing unit 22 substitutes the value represented by the digital signal supplied from the A / D conversion unit 21 into the inverse function of the function representing the demodulation characteristic of the FM demodulation unit 1 (that is, the value of the demodulated signal after correction). ) Is executed. Then, a digital signal representing the value of the demodulated signal after correction obtained as a result of this processing is generated and supplied to the D / A converter 23 as a demodulated signal after correction expressed in digital format.
[0040]
The processing executed by the signal processing unit 22 to obtain the value of the demodulated signal after correction is, for example, a digital function supplied from the A / D conversion unit 21 to an arbitrary approximation function that approximates the inverse function by a polynomial. Any processing that substitutes the value represented by the signal may be used. The approximation function may be specified by, for example, the FM demodulator manufacturer or the like measuring the demodulation characteristics of the FM demodulator 1 in advance.
[0041]
In addition, when the range of numerical values that can be handled is limited because the signal processing unit 22 is composed of a fixed-point type DSP or the like, if a numerical value that exceeds this range is handled, an overflow or underflow occurs, and an arithmetic operation is performed. The result cannot be obtained correctly.
In this case, it is necessary not to handle numerical values exceeding the range during the process of obtaining the polynomial value.
[0042]
Specifically, for example, the value represented by the digital signal supplied from the A / D conversion unit 21 is x, and the approximation function representing the corrected demodulated signal value is y (x). Is the value shown on the right side of Equation 5.
[0043]
[Equation 5]
y (x) = (5.42 · x ³ ) − (0.0024 · x ² ) + (1.8269 · x) −0.0001
[0044]
It is assumed that the range of values that can be handled by the signal processing unit 22 is from −1 to 1, and the range of values that x can take is from −0.4 to 0.4. In this case, the signal processing unit 22 may first calculate the right side of Expression 6 and substitute the obtained value u into the rightmost side of Expression 7 to obtain the value of y (x).
[0045]
[Formula 6]
u = 2 · x
[Expression 7]

[0046]
Alternatively, an external device that generates a test modulated wave with a known waveform supplies this test modulated wave to the input end of the FM demodulator 1 via a transmission path (not shown) under the control of the signal processor 22. Then, the signal processing unit 22 stores a plurality of values represented by the digital signal supplied from the A / D conversion unit 21 as a result, and uses the stored values, using a method such as a least square method, for the approximation. A function may be obtained.
[0047]
In accordance with the sampling signal generated by the sampling oscillator described above, the D / A conversion unit 23 converts an analog signal having a value indicated by the digital signal most recently supplied to its own input terminal to its own output terminal in an analog format. The corrected demodulated signal is output to the output end of the FM demodulator.
[0048]
Further, the correction unit 2 configured as shown in FIG. 2 may include a table storage unit 24 as shown in FIG.
The table storage unit 24 is composed of a ROM (Read Only Memory) or the like, and represents a value candidate represented by the digital signal supplied from the A / D conversion unit 21 and this value represents the demodulation characteristic of the FM demodulation unit 1. The values assigned to the inverse function of the function (or any function that approximates the inverse function) are stored in association with each other. Then, the value stored by itself is output in accordance with an instruction from the signal processing unit 22.
[0049]
When the correction unit 2 has the configuration shown in FIG. 3, for example, the signal processing unit 22 performs processing for obtaining the corrected demodulated signal value by the signal processing unit 22. The value stored in the table storage unit 24 may be searched using the value represented by the digital signal supplied from the key 21 as a key, and the value associated with the value used as the key may be searched. In this case, the retrieved value becomes the value of the demodulated signal after correction.
[0050]
Further, the FM demodulator 1 may also be constituted by a DSP and / or a CPU. When the FM demodulator 1 is composed of a DSP and / or a CPU, this FM demodulator may have the configuration shown in FIG. 4, for example.
[0051]
4 includes an A / D converter 31, a D / A converter 34, a DSP and / or a CPU that performs the functions of the FM demodulator 32 and the signal processor 33, as shown. Consists of.
Among these, the A / D converter 31 and the D / A converter 34 are substantially the same as the A / D converter 21 and the D / A converter 23 in FIG. 2 or FIG.
[0052]
The A / D converter 31 samples the FM modulated wave to be demodulated in accordance with a sampling signal generated by a sampling oscillator (not shown), converts it into a digital signal, and supplies the digital signal to the FM demodulator 32.
[0053]
The FM demodulator 32 demodulates the digital FM modulated wave supplied from the A / D converter 31 and supplies an uncorrected demodulated signal in digital format obtained by demodulation to the signal processor 33.
[0054]
The signal processing unit 33 performs substantially the same processing as that of the signal processing unit 22 in FIG. 2, thereby representing the value represented by the uncorrected demodulated signal in digital format supplied from the FM demodulation unit 32. The value substituted for the inverse function of the function representing the demodulation characteristic of is obtained. Then, a digital signal representing the value of the demodulated signal after correction is generated and supplied to the D / A converter 34 as a demodulated signal after correction expressed in a digital format.
[0055]
The D / A conversion unit 34, in accordance with the sampling signal that determines the sampling timing of the A / D conversion unit 31, outputs an analog signal having a value indicated by the digital signal most recently supplied from the signal processing unit 33. Output as a demodulated signal after correction expressed in analog form.
[0056]
Further, the FM demodulator having the configuration of FIG. 4 may include a table storage unit 35 that is substantially the same as the table storage unit 24 of FIG. 3, for example, as shown in FIG. 5.
However, the table storage unit 35 is a candidate for a value represented by the digital signal supplied from the FM demodulator 32 and an inverse function of the function representing the demodulation characteristic of the FM demodulator 32 (or an arbitrary function that approximates the inverse function). The values assigned to the function) are stored in association with each other.
[0057]
In the FM demodulator configured as shown in FIG. 5, the processing executed by the signal processing unit 33 to obtain the corrected demodulated signal value is, for example, a digital signal supplied from the FM demodulating unit 32 by the signal processing unit 33. It is only necessary to search for a value stored in the table storage unit 35 using the value represented by as a key, and to find a value associated with the value used as the key as the value of the demodulated signal after correction.
[0058]
When the FM demodulator acquires a digital FM modulated wave from the outside, the A / D converter 31 is not necessary and outputs a digital demodulated corrected signal. In this case, the D / A converter 34 is not necessary.
[0059]
Although the FM demodulator according to the embodiment of the present invention has been described above, the angle demodulator and the demodulation characteristic correction apparatus according to the present invention can be realized using a normal computer system, not a dedicated system. . For example, by installing the program from a medium (floppy disk, CD-ROM, etc.) storing a program for executing the above-described operation in a personal computer including an A / D converter and a D / A converter, An FM demodulator that performs the above-described processing can be configured.
[0060]
Further, for example, the program may be posted on a bulletin board (BBS) of a communication network and distributed through the network, or a carrier wave is modulated by a signal representing the program and the obtained modulated wave is transmitted. The apparatus that receives the modulated wave may demodulate the modulated wave to restore the program.
The above-described processing can be executed by starting this program and executing it under the control of the OS in the same manner as other application programs.
[0061]
When the OS shares a part of the processing, or when the OS constitutes a part of one component of the present invention, a program excluding the part is stored in the recording medium. May be. Also in this case, it is assumed that the recording medium stores a program for executing each function or step executed by the computer.
[0062]
【The invention's effect】
As described above, according to the present invention, an angle demodulator and a demodulation characteristic correction apparatus that can reduce the distortion of the demodulation output are realized.
In addition, according to the present invention, a demodulation characteristic correction apparatus that reduces distortion of the demodulation output of the demodulator without changing the demodulator is realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a basic configuration of an FM demodulator according to an embodiment of the present invention.
2 is a block diagram showing a basic configuration of a modification of the FM demodulator of FIG. 1; FIG.
FIG. 3 is a block diagram showing a basic configuration of a modification of the FM demodulator of FIG. 2;
4 is a block diagram showing a basic configuration of a modified example of the FM demodulator of FIG. 1; FIG.
FIG. 5 is a block diagram showing a basic configuration of a modification of the FM demodulator of FIG. 4;
FIG. 6 is a block diagram showing a basic configuration of a quadrature demodulator.
[Explanation of symbols]
1, 32 FM demodulation unit 2 Correction unit 21, 31 A / D conversion unit 22, 33 Signal processing unit 23, 34 D / A conversion unit 24, 35 Table storage unit

Claims (6)

Demodulation means for generating an uncorrected demodulated signal by demodulating the angle-modulated wave supplied to the self;
Output correcting means for acquiring the uncorrected demodulated signal from the demodulating means, generating a signal having a predetermined value associated with the acquired value of the uncorrected demodulated signal, and outputting the signal as a corrected demodulated signal And comprising
The value of the corrected demodulated signal state, and are not to approximate the value of the ideal demodulated signal obtained by ideally demodulating the angle modulated wave,
The demodulator obtains a test signal having a known waveform, and generates a test demodulated signal by demodulating the test signal,
The output correction means includes
Obtaining the test demodulated signal and using the value of the test demodulated signal, a correction function that associates the value of the uncorrected demodulated signal with the value of the ideal demodulated signal is approximated by a polynomial of a predetermined order Means for determining an approximation function;
Means for calculating a result obtained by substituting the value of the uncorrected demodulated signal into the approximation function, and generating and outputting a signal indicating the calculation result as the corrected demodulated signal,
An angle demodulator characterized by that. Means for generating the test signal;
The angle demodulator according to claim 1. The demodulating means includes a quadrature demodulating circuit.
The angle demodulator according to claim 1 or 2 , characterized in that Input means for acquiring the uncorrected demodulated signal from an external demodulator that generates an uncorrected demodulated signal by demodulating the angle-modulated wave supplied thereto;
Correction output means for generating a signal having a predetermined value associated with the value of the uncorrected demodulated signal acquired by the input means, and outputting the signal as a corrected demodulated signal,
The value of the corrected demodulated signal state, and are not to approximate the value of the ideal demodulated signal obtained by ideally demodulating the angle modulated wave,
The correction output means includes
A test demodulated signal generated by the demodulator demodulating a test signal having a known waveform is obtained, and the value of the uncorrected demodulated signal is obtained using the value of the demodulated test signal. Means for determining an approximation function for approximating a correction function associated with an ideal demodulated signal value by a polynomial of a predetermined order;
Means for calculating a result obtained by substituting the value of the uncorrected demodulated signal into the approximation function, and generating and outputting a signal indicating the calculation result as the corrected demodulated signal,
A demodulation characteristic correction apparatus characterized by the above. Computer
Demodulating means for generating an uncorrected demodulated signal by demodulating the angle-modulated wave supplied to the self;
Output correcting means for acquiring the uncorrected demodulated signal from the demodulating means, generating a signal having a predetermined value associated with the acquired value of the uncorrected demodulated signal, and outputting the signal as a corrected demodulated signal When,
A computer-readable recording medium having recorded thereon a program for causing it to function,
The value of the corrected demodulated signal state, and are not to approximate the value of the ideal demodulated signal obtained by ideally demodulating the angle modulated wave,
The demodulator obtains a test signal having a known waveform, and generates a test demodulated signal by demodulating the test signal,
The output correction means includes
Obtain the demodulated signal for test, and use the value of the demodulated signal for test to approximate a correction function that associates the value of the uncorrected demodulated signal with the value of the ideal demodulated signal with a polynomial of a predetermined order Means for determining an approximation function;
Means for calculating a result obtained by substituting the value of the uncorrected demodulated signal into the approximation function, and generating and outputting a signal indicating the calculation result as the corrected demodulated signal,
A recording medium characterized by the above. Computer
Input means for acquiring the uncorrected demodulated signal from an external demodulator that generates an uncorrected demodulated signal by demodulating the angle-modulated wave supplied thereto;
Correction output means for generating a signal having a predetermined value associated with the value of the uncorrected demodulated signal acquired by the input means, and outputting the signal as a corrected demodulated signal;
A computer-readable recording medium storing a program for causing the program to function,
The value of the corrected demodulated signal state, and are not to approximate the value of the ideal demodulated signal obtained by ideally demodulating the angle modulated wave,
The correction output means includes
The demodulator obtains a test demodulated signal generated by demodulating the test signal having a known waveform, and uses the value of the test demodulated signal to determine the value of the uncorrected demodulated signal. Means for determining an approximation function for approximating a correction function associated with an ideal demodulated signal value by a polynomial of a predetermined order;
Means for calculating a result obtained by substituting the value of the uncorrected demodulated signal into the approximation function, and generating and outputting a signal indicating the calculation result as the corrected demodulated signal,
A recording medium characterized by the above.

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