JPH0134130Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to an SWR meter for a wireless transmitter, and particularly to an automatic SWR meter that does not require switching between traveling wave detection output and SWR detection output under CPU control.

[Conventional technology and problems]

The basic circuit of a conventional SWR meter is shown in Figure 1.
Let's explain its operation. The high frequency power passing through the SWR circuit is rectified by a diode into a forward wave output 1A proportional to the forward wave power and a reflected wave output 1B proportional to the reflected wave power by a traveling wave and reflected wave detection circuit 1 and compared as DC outputs. . To do this, connect the SWR indicator 2 to the traveling wave output side through the sensitivity adjuster 3, and adjust the sensitivity adjuster so that the meter indicates full scale. Next, switch the meter to the reflected wave output side and read the SWR value from the scale of the meter at that time.

[Purpose of invention]

This invention uses the CPU (Central
The purpose is to provide a circuit that automatically measures and displays information at all times under the control of the Processing Unit.

[Structure of the idea]

This invention utilizes the remaining power of the CPU that is built into the transmitter and is used to automate the operation of equipment.
This device automatically displays the SWR meter, detects the SWR circuit's traveling wave power and SWR value in parallel, and connects them to transistors with the same output internal resistance through load resistors with the same resistance value. An indicator is provided in parallel to the output transistor for SWR value, and a resistance equal to the internal resistance of the indicator is connected in parallel between the collector and emitter of the output transistor for traveling wave detection. Therefore, the impedances of these transistor circuits are equal. Furthermore, the output of the traveling wave output transistor is applied to one terminal of the comparator, and a reference voltage equal to the full scale of the indicator is applied to the other terminal for comparison and is used as an input to the CPU. The current is converted into analog by a /A converter and applied to the base of each of the transistors mentioned above to control the current of the transistor and display an appropriate value on the indicator.

〔Example〕

An embodiment of the present invention will be described with reference to FIG.
Traveling wave detection output 1 of traveling wave and opposite wave detection circuit 1
The loads for A and reflected wave detection output 1B are load resistors 4A and 4B with the same value, and output internal resistances of transistors 5A and 5B with the same characteristics (for bipolar transistors, this is the collector-to-emitter resistance; for FETs, it is the drain-to-emitter resistance). Connect the SWR indicator 2 in parallel to the transistor 5A on the reflected wave side, and connect the SWR indicator 2 to the transistor 5A on the traveling wave side, which is a resistance 6 equal to the internal resistance of the indicator 2.
Connect in parallel. Since the control inputs of transistors 5A and 5B are connected in parallel and controlled by a common bias, the internal resistance of transistor 5A and the internal resistance of transistor 5B change at the same value, and the indicator 2 The sensitivity of the meter is the same whether it is connected to the 5A side or the transistor 5B side, and the indication is from the traveling wave detection output 1 of the detection circuit 1.
A and the reflected wave detection output 1B. Therefore, the second
As shown in the figure, the indicator 2 indicates the voltage drop of the transistor 5B, and if the control input is set so that the voltage drop of the transistor 5A matches the full scale value of the meter, the indicator 2 will indicate the voltage drop of the transistor 5B as shown in Fig. 1. Without switching connections, indicator 2 always indicates the ratio of the opposite wave to the forward wave, so this can be calculated as SWR.
It is possible to read the scale directly.

Next, to set the voltage drop of transistor 5A,
This voltage drop V _f is added to one input _of the comparator 7, and a reference voltage _{V r} equal to the full scale voltage of the indicator 2 is added to the other input for comparison. Since the output of is reversed, add this to the I/O input port of the CPU 8 and use a simple subroutine as shown in the flowchart in Figure 3 to output, for example, 8-bit binary output from the I/O output port. 1
The work of increasing or decreasing 1 is performed for each calculation, and the output is converted to DC by the D/A converter 9, and becomes a control bias for the transistors 5A and 5B, changing their internal resistance, and V _f and V _r This continues until a match is reached. D/A converter 9 used here
Since a high level of performance is not required, a simple circuit weighted with resistors as shown in FIG. 4 will suffice. Actually, in order to prevent the indicator from swinging out at the start, it is desirable to start from a state where the voltage drop of transistors 5A and 5B is small, so the input bias is set so that the internal resistance starts from the state where it is the minimum. Since the direction of bias may differ between bipolar transistors and FETs, it is necessary to match the characteristics of the element used, but in short, changes in comparator input → CPU
The loop operation of increase/decrease in output→increase/decrease in D/A conversion output→change in transistor internal resistance→comparator input may be configured in a direction that converges to V _f =V _r . Figure 5 shows an example of input/output connections for the CPU section.

[Effect of idea]

The present invention does not require manual operation to adjust the sensitivity of the indicator according to the size of the traveling wave in conventional SWR meters, making it easier to handle, and it also allows continuous monitoring during use. It is also convenient to use by incorporating it into a transmitter.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing the principle of a conventional SWR meter.
Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is a flowchart showing the operation of the CPU, and Fig. 4 is a block diagram showing an embodiment of the present invention.
The figure is the circuit diagram of the D/A converter, and Figure 5 is the CPU.
The input/output circuit diagram is shown. 1...Detection circuit, 2...Indicator, 3...Sensitivity adjuster, 4A, 4B...Load resistance, 5A, 5B...
Transistor, 7... Comparator, 8...
CPU, 9...D/A converter.

Claims (1)

[Scope of utility model registration request] Each output load of the detection circuit is inserted between the output end of the transmitter and the load and outputs a voltage proportional to the forward wave intensity and a voltage proportional to the reflected wave intensity simultaneously and separately. The output internal resistance of the transistor with the characteristic is connected in series, and the transistor on the reflected wave side is connected in parallel with the SWR direct reading scale.
A means for connecting an SWR indicator, connecting a resistance equal to the internal resistance of the SWR indicator to the transistor on the traveling wave side in parallel, and adding the voltage drop of the transistor for the traveling wave to one side of the comparator and applying it to the other input. applies the reference voltage, and the output side of the comparator is
A means to connect to the input port of the CPU and control the increase/decrease of the binary output of the output port, and the corresponding
An automatic SWR meter characterized by comprising means for commonly applying a voltage obtained by converting the output of a CPU into analog by a D/A converter as a control input to each transistor of the traveling wave detection circuit and the reflected wave detection circuit.