JPS6347292B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power detection circuit with a wide operating range to prevent erroneous transmission.

A conventional circuit of this type is shown in FIG. In Figure 1, 1 is the terminal to which the transmission output is applied, 2 is the transmission output terminal, 3 is the coupling capacitor, 4 and 5 are the detection diodes, 6 is the smoothing capacitor, 7 is the detection output terminal, and 8 is the detection circuit. It is load resistance.

In this circuit, in order to detect the high frequency power passing from terminal 1 to terminal 2, a voltage doubler detection circuit consisting of detection diodes 4 and 5 and capacitors 3 and 6 is used.
It is coupled to a transmission output circuit via a coupling capacitor 3 with a minute capacitance. Conventionally, the degree of coupling by the coupling capacitor 3 has been required to be sufficiently loose to protect the detection diode and to prevent harmonic distortion components generated by the detector from being mixed into the transmission output. On the other hand, erroneous transmission may be transmitted at a level that is 20 to 60 decibels lower than the normal output level, and in order to detect such a low level output, it is necessary to make the coupling degree dense. Therefore, it is very difficult to set the degree of coupling, and there are drawbacks such as the inability to detect low-level erroneous transmissions.

The present invention eliminates these drawbacks, makes it possible to detect an erroneous transmission output level that is sufficiently lower than the normal transmission output level, and protects the detection diode from being destroyed. The purpose is to FIG. 2 is a diagram showing the configuration of a basic detection circuit for preventing erroneous transmission according to an embodiment of the present invention. In Fig. 2, 1A is a terminal for applying a transmission output, 2A is a transmission output terminal, 9 is a coupling circuit means, 10 is a voltage or current variable resistance element, 11 is a detection circuit, and 12 is a terminal when the detection voltage exceeds a certain value. A voltage detection circuit to detect this. 13 is a drive circuit for driving the variable resistance element 10.

In this embodiment, a variable resistance element is interposed between the transmission output circuit section and the detection circuit section, and the degree of coupling is varied in accordance with the transmission output.

FIG. 3 shows a more specific circuit configuration of the above-described embodiment. In FIG. 3, the same functional parts as in FIG. 1 are indicated by the same reference numerals. 14 is a coupling capacitor, and 15 is a current controlled variable resistance element (PIN diode). 17 and 21 are bypass capacitors, and 18 and 19 are voltage dividing resistors for dividing the DC voltage applied from the terminal 20 and applying a reverse bias to the PIN diode 15. 16 is
This is a chiyoke coil for applying forward bias to the PIN diode 15, and the inductance value is
It is selected so that signal leakage due to residual capacitance when the PIN diode 15 is cut off is canceled by parallel resonance. This is a constant voltage diode (Zener diode), which becomes conductive when the output voltage of the detection output voltage terminal 7 exceeds a certain value, and the
Through the PIN diode 15 and voltage dividing resistor 19,
A forward current is supplied to the PIN diode 15.

Next, the operation of this embodiment will be explained. Naturally, when the transmission voltage passing between terminals 1A and 2A is a very small value, the detected output voltage appearing at terminal 7 is small. Therefore, the Zener diode 22 is not conductive, and the potential on the anode side of the PIN diode 15 is
The resistor 23 provides a ground potential. On the other hand, since a positive voltage applied from the terminal 20 and divided by the resistors 18 and 19 is always applied to the cathode side of the PIN diode 15, the PIN diode 15 becomes in a reverse bias state and becomes non-conductive. Also, at this time, due to the residual capacitance of the PIN diode 15 when it is non-conducting, high frequency signals are prevented from leaking to the ground side via the PIN diode 15, reducing the high frequency input signal to the detection section and reducing the detection sensitivity. Therefore, a coil 16 and a capacitor 17 are inserted in parallel with the PIN diode 15 so as to resonate in parallel with the residual capacitance in the usage band.

Further, when the transmission power reaches a certain value or more, the voltage at the detection output terminal 7 increases and the Zener diode 22 becomes conductive. Therefore, the detection output voltage is
The voltage is supplied to the anode side of the PIN diode 15, and when the voltage exceeds a voltage value determined by the Zener voltage value of the Zener diode 22, the reverse bias voltage value determined by the resistors 18 and 19, etc., the PIN diode 15 becomes conductive. Since the high frequency resistance value of the PIN diode 15 decreases as the forward current value increases, high frequency power exceeding a certain value is not applied to the detection diodes 4 and 5, thereby preventing deterioration and damage of the detection diodes.

FIG. 4 shows the input/output characteristics of the circuit of the present invention, where the horizontal axis is the input voltage and the vertical axis is the detection output terminal voltage. In the figure, the dotted line indicates the input/output characteristic of the conventional circuit as shown in FIG. 1, and the solid line indicates the input/output characteristic of the above embodiment. It is clear from the figure that in this embodiment, only high frequency power above a certain value is applied to the detection section.

FIG. 5 shows another specific embodiment. In FIG. 5, the same functional parts as in FIG. 3 are indicated by the same reference numerals. In Figure 5, the third point is that the PIN diode 29 is placed in series in front of the detection section.
It is different from the illustration. Reference numeral 23 in FIG. 5 is a DC blocking capacitor, and the chiyoke coil 24 functions as a parallel resonant coil that cancels out the residual capacitance of the PIN diode 29 when it is non-conducting. 25 and 30 are high frequency choke coils, 26 is a forward bias application terminal to the PIN diode, and 27 and 28 are voltage dividing resistors.

This embodiment is different from the case shown in FIG. 3 in that the PIN diode 29 is conductive when the high-frequency output power is a very small value, and when it exceeds a certain value, it is gradually reverse biased and becomes non-conductive.

As explained above, according to the present invention, conventionally,
Since the operating range of the erroneous transmission detection circuit, which has a narrow operating range, can be expanded, it becomes possible to detect a case where a small amount of power is erroneously sent out when a high-output transmitter stops transmitting. Further, since the present invention can be realized by adding only a small number of passive elements to a conventional circuit without adding any performance elements, it is inexpensive, highly reliable, and has great industrial utility value.

[Brief explanation of drawings]

Figure 1 is a wiring diagram of a conventional erroneous transmission detection circuit;
The figure is a block diagram of an erroneous transmission detection circuit according to an embodiment of the present invention, FIG. 3 is a wiring diagram showing its specific circuit configuration, FIG. 4 is a characteristic diagram of the same, and FIG. 5 is another specific circuit. FIG. 3 is a wiring diagram showing the configuration. 10... Variable resistance element, 11... Detection circuit, 1
2... Voltage detection circuit.

Claims (1)

[Claims] 1. A variable current resistance element, a detection circuit means loosely coupled to a transmission output circuit via the variable current resistance element, and a detection circuit means for detecting when the output voltage of the detection circuit means exceeds a certain value. What is claimed is: 1. An erroneous transmission detection circuit, comprising: voltage detection circuit means for detecting a false transmission, wherein said current variable resistance element is controlled by said voltage detection circuit means. 2. Erroneous transmission detection according to claim 1, characterized in that a PIN diode is used as the current variable resistance element, a Schottky diode is used as the detection circuit means, and a Zener diode is used as the voltage detection circuit means. circuit.