JPS58133004A - Amplitude detector - Google Patents

Abstract

PURPOSE:To obtain a detector which can work regardless of the DC level of a signal which received an amplitude modulation and is also converted easily into an IC, by using no resistance but using a capacitor of small capacity and a switch. CONSTITUTION:A signal input terminal 1 is connected to an end of a switch 2, and the other end of the switch 2 is connected to an earth via a capacitor 3 as well as to an end of a switch 4. The other end of the switch 4 is connected to an output terminal 5. Then an amplitude modulating signal shown in a figure (a) is applied as an input V1, and at the same time double phase clocks phi1 and phi2 shown in a figure (b) are applied as the signals to switch the switches 2 and 4. Thus the terminal voltage VC of the capacitor 3 shows the envelope curve of an amplitude modulating signal, and a wave detecting signal is extracted through the switch 4. It is also possible to form an amplitude wave detecting circuit without using any resistance but using a capacitor of small capacity and switches. As a result, the capacitor can be stored into an IC. Thus an IC can be formed easily.

Description

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to provide a detection device that can detect amplitude-modulated signals regardless of their DC level and can be easily integrated into an integrated circuit.

Conventionally known amplitude detection devices have a detection output that changes depending on the DC level of the input signal, which is an amplitude-modulated signal, so it is necessary to fix the DC level before detection, and it is also necessary to use resistors and capacitors. The disadvantage is that it is difficult to integrate into an integrated circuit.

The present invention aims to eliminate the above-mentioned drawbacks, and one embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the signal input terminal 1 is connected to one end of a first switch 2, and the other end of this switch 2 is connected to a capacitor 3.
It is connected to ground (reference potential point) via the switch 4, and also connected to one end of the second switch 4. The other end of this switch 4 is connected to the output terminal 6VC. Now, input terminal 1
The voltage at the output terminal 6 is vl, and the voltage at the output terminal 6 is v2. capacitor 3
Let C be the capacity of This capacitance C may be as small as several 1oPF, and can be created within an IC. When the switch 2 is closed, the charge Q1 of the capacitor 2 becomes Q,=Cv. When the switch 2 is opened and the switch 4 is closed, the charge Q2 of the capacitor 3 becomes Q2=Cv2. Therefore, one charge ΔQ that has moved becomes ΔQ=Q, -Q2=(Vl-V2)C. If switches 2 and 4 are switched by f8 every second, the movement of charge per second is defined by the current, so I = △Q
X fm = (Vl-v2) C-f s.

Since the potential difference divided by the flowing current I becomes resistance according to Ohm's law, if this is R, then R becomes the following equation.

R: (Vl-V2)/I = 1/Cf.

In this way, a resistance can be formed isometrically by switching the capacitor 3.

Next, an amplitude modulated wave signal as shown in FIG. 2a is applied as an input V, and a two-phase clock φ as shown in FIG. 2 is used as a signal for switching the switches 2 and 4.

If φ2 is given, the terminal voltage vc of the capacitor 3 represents the envelope of the amplitude modulated wave signal, and the switch 4
The detection signal can be detected through.

Furthermore, when a capacitor 6 is connected as a load to the switch 4 as shown in Fig. 3, R:= 1/C1 according to the principle described earlier.
- A low-pass filter can be configured with the resistor represented by fs and the capacitor 6.

Here, the cutoff frequency fc of the filter is determined by the transfer function H(8) = 5 m and ``CH@) = 1 /
Since it is expressed as (1+802-R), fc=1/2πC2・R=C1f, /2πc2,
It is uniquely determined by the ratio of capacitors C4 and C2 and the clock f8. Note that C4 is the capacitance of the capacitor 3 shown in FIG. 3, and C2 is the capacitance of the same capacitor 6.

Such a detection circuit is suitable for integration because it can perform detection completely independent of the DC level of the input signal and can be constructed using a capacitor with a small capacitance without using a resistive element.

φ1 and φ2 can be easily created by extracting the input signal carrier wave component using a suitable limiter amplifier and delay circuit and shaping the waveform.

The switch can also be easily made using a MOS transmission gate. The load 6 may be an operational amplifier with feedback applied to it by a capacitor, as shown in FIG. At this time, the transfer function H of the filter is a(s)=c, .fs/5-C2. The switch 2.4 is shown using a MOS switch.

As described above, according to the present invention, it is possible to configure an amplitude detection circuit using a small capacitor and a switch without using a resistor, and the capacitor can also be housed in an integrated circuit, making it suitable for integrated circuits. Furthermore, since detection can be performed regardless of the DC level of the input signal, it can be easily configured.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of the amplitude detection device of the present invention, Fig. 2 is a waveform diagram for explaining the same device, Fig. 3 is a circuit diagram of the amplitude detection device in the embodiment of the same place, and Fig. 4 is a concrete diagram of the same. FIG. 2 is a circuit diagram showing a circuit. 1... Signal input terminal, 2... First switch, 4... Second switch, 3...
・Capacitor, 6...Output terminal. Figure 1 Figure 12

Claims (2)

[Claims] (1) Apply the amplitude-modulated signal to one end of the first switch, connect the other end of the first switch to one end of the second switch, and connect it to the reference potential point via a capacitor, so that the phase is Generate signals φ, and φ2, turn on the first switch with the signal φ1, charge the capacitor with the peak voltage of the amplitude-modulated signal, and generate the signal φ1.
2. An amplitude detection device patented in which the second switch is turned on and off by a signal of 1 and the detection output is output from the other end of the second switch. (2) The amplitude detection device according to claim 1, 6, characterized in that a capacitor is connected to the other end of the second switch to suppress a carrier component contained in the detected output.