JP2004080112A - Detection circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a detection circuit for stably detecting a received signal subjected to amplitude shift keying modulation. <P>SOLUTION: An LNA 21 applies low noise amplification to a signal received by an antenna 11 and subjected to ASK (amplitude shift keying) modulation and a mixer 22 converts the amplified signal into a base band signal. Then the detection circuit 23 uses an integrator comprising a resistor R1 and a capacitor C1 to obtain an average voltage of the received signal and gives it to an input A of a comparator H1. The detection circuit 23, on the other hand, adjusts the received signal into a proper voltage corresponding to the average voltage of the received signal by using a voltage division ratio by means of an input resistor R2 and a pull-down resistor R3 and gives the adjusted voltage to an input B of the comparator H1. Thus, the comparator H1 uses, as reference voltage, the average voltage of the received signal received at the input A to extract an amplitude change in the received signal corresponding to digital data superimposed on the received signal received by the input B and an output of a comparison result of the comparator H1 is acquired as a detection output of the received signal by the detection circuit 23. <P>COPYRIGHT: (C)2004,JPO

Description

【００１３】
次に、車載無線機１の構成について説明すると、車載無線機１は、図２に示すように、アンテナ１１に接続されたＲＦモジュール部１２を構成する受信機１３と送信機１４、及び車載無線機１を利用者が操作するためのスイッチ（ＳＷ１〜ＳＷ３）や、利用者が操作内容及び通行料金を確認するための表示部やＬＥＤを備えたインタフェース部１５、更に利用者の個人情報等を記録したＩＣカードを読み書きするためのＩＣカード読み書き器１６を備え、車載無線機１の各部を制御するためのＣＰＵ（中央処理装置）やメモリを含む制御部１７とを備えている。なお、制御部１７は、受信ディジタル信号に施されたマンチェスタ符号を復号したり、マンチェスタ符号を復号した受信データの誤り訂正等を行う機能も備えている。
【００１４】
また、本実施の形態による検波回路を備えた受信機は、上述の受信機１３であって、受信機１３は、マンチェスタ符号化が施されると共にＡＳＫ（振幅偏移変調：Ａｍｐｌｉｔｕｄｅ　Ｓｈｉｆｔ　Ｋｅｙｉｎｇ）によって変調され、路側無線装置２から送信された信号を受信する。
具体的には、図３に示すように、受信機１３は、アンテナ１１に接続されると共に、受信した信号を低雑音増幅するＬＮＡ（Ｌｏｗ　Ｎｏｉｓｅ　Ａｍｐ　）２１と、ＬＮＡ２１の出力を周波数変換し、受信信号をベースバンド信号へ変換するミキサ２２と、ミキサ２２の出力のＡＳＫ変調信号を復調してマンチェスタ符号化が施された検波出力信号を出力する検波回路２３とを備えている。
【００１５】
また、検波回路２３は、抵抗Ｒ１、入力抵抗Ｒ２、プルダウン抵抗Ｒ３、コンデンサＣ１、コンデンサＣ２、及び比較器Ｈ１とを備えている。
ここで、抵抗Ｒ１とコンデンサＣ１は、ＡＳＫ変調された受信信号を平均化して該受信信号の平均電圧を生成する積分器を構成し、該積分器の出力は比較器Ｈ１のＡ入力に接続され、比較器Ｈ１のＡ入力には受信信号の平均電圧が入力される。
【００１６】
一方、比較器Ｈ１のもう一方のＢ入力には、ミキサ２２の出力する受信信号が、入力抵抗Ｒ２を介して入力される。
また、比較器Ｈ１のＢ入力と電源（図示せず）の接地端子（グランド）との間にはプルダウン抵抗Ｒ３が接続されており、入力抵抗Ｒ２とプルダウン抵抗Ｒ３との分圧比により比較器Ｈ１へ入力する受信信号の電圧値を調整できるような調整手段を構成している。
これにより、比較器Ｈ１は、Ａ入力に入力された受信信号の平均電圧を基準電圧として、Ｂ入力に入力された受信信号に重畳されたディジタルデータに対応する受信信号の振幅変化を抽出し、比較器Ｈ１の比較結果出力を検波回路２３における受信信号の検波出力として取得する。
【００１７】
従って、図４に示すように、例えば時刻ｔ１のような変調度の小さい信号を受信した場合においても、比較器Ｈ１の出力Ｐ３に受信信号の振幅変化に対応する安定的な信号が出力されるように、プルダウン抵抗Ｒ３の抵抗値に入力抵抗Ｒ２に応じた適当な値を設定し、受信信号の平均電圧Ｐ１に対して受信信号Ｐ２の電圧値が適正な電圧値になるようにプルダウン抵抗Ｒ３の抵抗値を調整する。
なお、図３において、コンデンサＣ２は、比較器Ｈ１のＡ入力とＢ入力との間に電位差が生じることを防止するために、比較器Ｈ１のＡ入力とＢ入力との間で、入力される受信信号に含まれる周波数成分より高域の周波数成分におけるインピーダンスが小さくなるように挿入する。
【００１８】
以上説明したように、本実施の形態による検波回路によれば、ＡＳＫ変調された受信信号を検波するための比較器Ｈ１のＡ入力に、抵抗Ｒ１とコンデンサＣ１とにより構成された積分器の出力を接続して、受信信号の平均電圧を比較器Ｈ１へ入力すると共に、比較器Ｈ１のＢ入力に、入力抵抗Ｒ２とプルダウン抵抗Ｒ３により分圧されて受信信号の平均電圧に対して適正な電圧値に調整された受信信号を入力することで、比較器Ｈ１における受信信号の平均電圧と受信信号との比較を適正な電圧値により実行し、安定してＡＳＫ変調された信号を検波することができる。
従って、ＡＳＫ変調された信号の変調度に拘わらず、安定して信号を検波することができるようになり、通信性能が向上するという効果が得られる。
【００１９】
また、上述の実施の形態では、比較器Ｈ１のＢ入力と電源（図示せず）の接地端子（グランド）との間にプルダウン抵抗Ｒ３を挿入する例について説明したが、ミキサ２２の出力する受信信号の電圧値や受信信号の正負の変調方向によっては、比較器Ｈ１のＢ入力と電源（図示せず）の正極端子との間にプルアップ抵抗を挿入し、入力抵抗Ｒ２と該プルアップ抵抗との分圧比により比較器Ｈ１へ入力する受信信号の電圧値を調整できるような調整手段を構成しても良い。
【００２０】
更に、比較器Ｈ１の入力に接続するプルダウン抵抗あるいはプルアップ抵抗を、比較器Ｈ１のＡ入力側に接続して、プルダウン抵抗あるいはプルアップ抵抗と抵抗Ｒ１及びコンデンサＣ１とで調整手段を構成し、比較器Ｈ１のＢ入力に入力される受信信号の電圧値を調整するのではなく、比較器Ｈ１の基準電圧とするＡ入力側の受信信号の平均電圧の電圧値を調整するようにしても良い。
これにより、比較器Ｈ１の入力において、受信信号の平均電圧と受信信号の電圧の差を適正かつ自由に調整することができるようになるという効果が得られる。
【００２１】
【発明の効果】
以上の如く、請求項１から請求項５に記載の検波回路によれば、比較器の入力において、受信信号の平均電圧と受信信号の電圧の差を適正かつ自由に調整することができる。
従って、比較器において受信信号の平均電圧を基準電圧として、受信信号に重畳されたディジタルデータに対応する受信信号の振幅変化を安定して抽出し、受信信号に重畳されたディジタルデータの伝送速度が高速で、受信信号の変調度が小さい信号を受信するような場合でも、安定して振幅偏移変調された信号の検波出力を得ることができるようになり、通信性能が向上するという効果が得られる。
【図面の簡単な説明】
【図１】本発明の一実施の形態による検波回路を備えた受信機を用いて実現する自動料金収受システムを示す図である。
【図２】同実施の形態による検波回路を備えた受信機を含む車載無線機の構成を示す図である。
【図３】同実施の形態による検波回路を備えた受信機の構成を示す図である。
【図４】同実施の形態による検波回路における各部の信号を示す図である。
【図５】従来の検波回路における各部の信号を示す図である。
【符号の説明】
１　　車載無線機
２　　路側無線装置
３　　車両
４　　料金ゲート
１１　　アンテナ
１２　　ＲＦモジュール部
１３　　受信機
１４　　送信機
１５　　インタフェース部
１６　　ＩＣカード読み書き器
１７　　制御部
２１　　ＬＮＡ
２２　　ミキサ
２３　　検波回路
Ｃ１、Ｃ２　　コンデンサ
Ｒ１　　抵抗
Ｒ２　　入力抵抗
Ｒ３　　プルダウン抵抗
Ｈ１　　比較器[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a detection circuit of a receiver.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, when a received signal subjected to amplitude shift keying (ASK: Amplitude Shift Keying) is received, the received signal subjected to amplitude shift key modulation by an integrator is averaged to generate an average voltage of the received signal. By comparing the voltage value between the output signal of the integrator and the received signal, the amplitude change of the received signal corresponding to the digital data superimposed on the received signal is extracted using the average voltage of the received signal as a reference voltage, Is obtained as the detection output of the received signal.
[0003]
[Problems to be solved by the invention]
However, when the transmission rate of the digital data superimposed on the received signal is high and a signal having a small modulation factor of the received signal is received, the difference between the average voltage of the received signal and the voltage of the received signal becomes small. In some cases, it may not be possible to extract a change in amplitude of a received signal corresponding to digital data superimposed on the received signal using the average voltage of the received signal as a reference voltage.
Specifically, as shown in FIG. 5, for example, at time t2, when a state occurs in which the average voltage P4 of the received signal and the voltage value of the received signal P5 become substantially the same value, the output of the comparator At P6, there is a problem that an unstable signal is output which makes it difficult to determine whether or not to extract the change as the amplitude of the received signal.
[0004]
The present invention has been made in view of the above problems, and has as its object to provide a detection circuit for stably detecting a received signal subjected to amplitude shift keying modulation.
[0005]
[Means for Solving the Problems]
In order to solve the above problem, a detection circuit according to the first aspect of the present invention includes an integrator (for example, the resistor R1 of the embodiment) that averages an amplitude-shift-modulated received signal to generate an average voltage of the received signal. And a capacitor C1), and a comparator (for example, the comparator H1 of the embodiment) for comparing a voltage value between the output signal of the integrator and the received signal, and detects an output of the comparator to detect the received signal. In a detection circuit of a receiver as an output, an adjusting terminal (for example, an input resistor R2 and a pull-down resistor R3 of the embodiment) for adjusting a voltage value of an input signal to the comparator is provided at an input terminal of the comparator. It is characterized by having.
[0006]
The detection circuit having the above configuration appropriately adjusts the difference between the average voltage of the received signal and the voltage of the received signal at the input of the comparator, and uses the average voltage of the received signal as the reference voltage in the comparator to generate the received signal. A change in the amplitude of the received signal corresponding to the superimposed digital data can be stably extracted.
[0007]
In the detection circuit according to a second aspect of the present invention, in the detection circuit according to the first aspect, the adjustment means is connected between an input terminal for inputting the reception signal to the comparator and a ground terminal of a power supply. The pull-down resistor (for example, the pull-down resistor R3 of the embodiment) is included.
The detection circuit having the above configuration can lower the entire voltage value of the received signal when the received signal is input to the comparator.
[0008]
According to a third aspect of the present invention, in the detection circuit according to the first aspect, the adjustment means is connected between an input terminal for inputting the reception signal to the comparator and a positive terminal of a power supply. And a pull-up resistor.
The detection circuit having the above configuration can increase the entire voltage value of the received signal when the received signal is input to the comparator.
[0009]
In the detection circuit according to a fourth aspect of the present invention, in the detection circuit according to the first aspect, the adjustment unit may include a ground terminal of a power supply and an input terminal for inputting an output signal of the integrator to the comparator. It is characterized by including a pull-down resistor connected between them.
The detection circuit having the above configuration can lower the entire voltage value of the output signal when the output signal of the integrator is input to the comparator.
[0010]
In a detection circuit according to a fifth aspect of the present invention, in the detection circuit according to the first aspect, the adjusting means may include an input terminal for inputting an output signal of the integrator to the comparator and a positive terminal of a power supply. It is characterized by including a pull-up resistor connected therebetween.
The detection circuit having the above configuration can increase the entire voltage value of the output signal when the output signal of the integrator is input to the comparator.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, a receiver including a detection circuit according to an embodiment of the present invention will be briefly described.
As shown in FIG. 1, the receiver is a receiver provided in a vehicle-mounted wireless device 1 used in an intelligent transportation system, particularly in an automatic toll collection system. The vehicle-mounted wireless device 1 is shown in Table 1 below. Two-way wireless communication with such specifications is performed with the roadside apparatus 2. At this time, the roadside apparatus 2 transmits a signal requesting a toll to the vehicle-mounted radio 1 mounted on the vehicle 3 and notifies the signal received from the vehicle-mounted radio 1 to a toll collection server (not shown). I do. When the toll collection server confirms the receipt of the toll by the signal from the in-vehicle wireless device 1 notified, the toll gate 4 is opened to permit the vehicle 3 equipped with the in-vehicle wireless device 1 to pass.
[0012]
[Table 1]

[0013]
Next, the configuration of the in-vehicle wireless device 1 will be described. As shown in FIG. 2, the in-vehicle wireless device 1 includes a receiver 13 and a transmitter 14 that constitute an RF module unit 12 connected to an antenna 11, and an in-vehicle wireless device. A switch (SW1 to SW3) for the user to operate the machine 1, an interface unit 15 including a display unit and an LED for the user to confirm the operation content and the toll, and further, the personal information of the user. An IC card reader / writer 16 for reading and writing the recorded IC card is provided, and a control unit 17 including a CPU (Central Processing Unit) for controlling each unit of the vehicle-mounted wireless device 1 and a memory is provided. The control unit 17 also has a function of decoding the Manchester code applied to the received digital signal, correcting errors in the received data obtained by decoding the Manchester code, and the like.
[0014]
The receiver including the detection circuit according to the present embodiment is the above-described receiver 13. The receiver 13 performs Manchester encoding and performs ASK (Amplitude Shift Keying). The signal that has been modulated and transmitted from the roadside apparatus 2 is received.
Specifically, as shown in FIG. 3, the receiver 13 is connected to the antenna 11 and frequency-converts the output of the LNA 21 with an LNA (Low Noise Amp) 21 that amplifies the received signal with low noise, The mixer 22 includes a mixer 22 that converts a received signal into a baseband signal, and a detection circuit 23 that demodulates an ASK modulation signal output from the mixer 22 and outputs a detection output signal subjected to Manchester encoding.
[0015]
The detection circuit 23 includes a resistor R1, an input resistor R2, a pull-down resistor R3, a capacitor C1, a capacitor C2, and a comparator H1.
Here, the resistor R1 and the capacitor C1 constitute an integrator that averages the ASK-modulated received signal to generate an average voltage of the received signal, and the output of the integrator is connected to the A input of the comparator H1. , The average voltage of the received signal is input to the A input of the comparator H1.
[0016]
On the other hand, the reception signal output from the mixer 22 is input to the other B input of the comparator H1 via the input resistor R2.
Further, a pull-down resistor R3 is connected between the B input of the comparator H1 and a ground terminal (ground) of a power supply (not shown), and the comparator H1 is determined by a voltage dividing ratio between the input resistor R2 and the pull-down resistor R3. And an adjusting unit configured to adjust a voltage value of a received signal input to the control unit.
Thereby, the comparator H1 extracts the amplitude change of the received signal corresponding to the digital data superimposed on the received signal input to the B input, using the average voltage of the received signal input to the A input as a reference voltage, The comparison result output of the comparator H1 is obtained as the detection output of the received signal in the detection circuit 23.
[0017]
Therefore, as shown in FIG. 4, even when a signal having a small modulation factor such as at time t1 is received, a stable signal corresponding to the amplitude change of the received signal is output to the output P3 of the comparator H1. Thus, an appropriate value corresponding to the input resistance R2 is set as the resistance value of the pull-down resistor R3, and the pull-down resistor R3 is set so that the voltage value of the reception signal P2 becomes an appropriate voltage value with respect to the average voltage P1 of the reception signal. Adjust the resistance value of.
In FIG. 3, the capacitor C2 is input between the A and B inputs of the comparator H1 in order to prevent a potential difference between the A and B inputs of the comparator H1. It is inserted so that the impedance in the frequency components higher than the frequency components included in the received signal becomes smaller.
[0018]
As described above, according to the detection circuit of the present embodiment, the output of the integrator constituted by the resistor R1 and the capacitor C1 is input to the A input of the comparator H1 for detecting the ASK-modulated received signal. To input the average voltage of the received signal to the comparator H1, and to the input B of the comparator H1, the voltage is divided by the input resistor R2 and the pull-down resistor R3 so that the voltage is appropriate for the average voltage of the received signal. By inputting the received signal adjusted to the value, the average voltage of the received signal and the received signal in the comparator H1 can be compared with an appropriate voltage value, and the signal ASK-modulated stably can be detected. it can.
Therefore, regardless of the modulation degree of the ASK-modulated signal, the signal can be detected stably, and the effect of improving the communication performance can be obtained.
[0019]
Further, in the above-described embodiment, an example has been described in which the pull-down resistor R3 is inserted between the B input of the comparator H1 and the ground terminal (ground) of the power supply (not shown). Depending on the signal voltage value and the positive / negative modulation direction of the received signal, a pull-up resistor is inserted between the B input of the comparator H1 and the positive terminal of the power supply (not shown), and the input resistor R2 and the pull-up resistor are inserted. May be configured so that the voltage value of the received signal input to the comparator H1 can be adjusted based on the voltage division ratio of.
[0020]
Further, a pull-down resistor or a pull-up resistor connected to the input of the comparator H1 is connected to the A input side of the comparator H1, and an adjusting means is constituted by the pull-down resistor or the pull-up resistor, the resistor R1, and the capacitor C1, Instead of adjusting the voltage value of the received signal input to the B input of the comparator H1, the voltage value of the average voltage of the received signal on the A input side as the reference voltage of the comparator H1 may be adjusted. .
As a result, at the input of the comparator H1, an effect is obtained that the difference between the average voltage of the received signal and the voltage of the received signal can be adjusted properly and freely.
[0021]
【The invention's effect】
As described above, according to the detection circuits of the first to fifth aspects, the difference between the average voltage of the received signal and the voltage of the received signal can be appropriately and freely adjusted at the input of the comparator.
Therefore, the comparator uses the average voltage of the received signal as a reference voltage to stably extract a change in the amplitude of the received signal corresponding to the digital data superimposed on the received signal, and to reduce the transmission speed of the digital data superimposed on the received signal. Even when receiving a signal at a high speed and a small modulation factor of the received signal, it is possible to stably obtain a detection output of the signal subjected to the amplitude shift key modulation, thereby obtaining an effect of improving communication performance. Can be
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an automatic toll collection system realized using a receiver including a detection circuit according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a configuration of an on-vehicle wireless device including a receiver including the detection circuit according to the embodiment;
FIG. 3 is a diagram showing a configuration of a receiver including the detection circuit according to the embodiment.
FIG. 4 is a diagram showing signals of respective units in the detection circuit according to the embodiment.
FIG. 5 is a diagram showing signals of various parts in a conventional detection circuit.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 vehicle-mounted radio 2 roadside radio 3 vehicle 4 toll gate 11 antenna 12 RF module 13 receiver 14 transmitter 15 interface 16 IC card reader / writer 17 controller 21 LNA
22 mixer 23 detection circuit C1, C2 capacitor R1 resistor R2 input resistor R3 pull-down resistor H1 comparator

Claims (5)

An integrator for averaging the amplitude-shift-modulated received signal to generate an average voltage of the received signal; and a comparator for comparing a voltage value between the output signal of the integrator and the received signal. In a detection circuit of a receiver that uses the output of the receiver as a detection output of the reception signal,
An adjusting circuit for adjusting the voltage value of an input signal to the comparator at an input terminal of the comparator. 2. The detection circuit according to claim 1, wherein the adjustment unit includes a pull-down resistor connected between an input terminal for inputting the reception signal to the comparator and a ground terminal of a power supply. 2. The detection circuit according to claim 1, wherein the adjustment unit includes a pull-up resistor connected between an input terminal for inputting the reception signal to the comparator and a positive terminal of a power supply. 2. The detection device according to claim 1, wherein the adjustment unit includes a pull-down resistor connected between an input terminal for inputting an output signal of the integrator to the comparator and a ground terminal of a power supply. circuit. 2. The device according to claim 1, wherein the adjusting unit includes a pull-up resistor connected between an input terminal for inputting an output signal of the integrator to the comparator and a positive terminal of a power supply. Detection circuit.

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