RU2345372C1 - Device for measuring of shf power - Google Patents

Abstract

FIELD: physics, measuring.

SUBSTANCE: invention concerns the measuring technics and can be used in systems of the automated control of the radar-tracking equipment. Device contains thermistor key 1, to one of which diagonals the filter 2, the amplifier 3 direct currents, the switch 4, the integrator 5, the generator 6 currents and a key 7, and also an ADC 8 and the generator of 9 impulses with controllable duration are consistently connected. The ADC input 8 is connected to the second inlet of the switch 4. The ADC output 8 is an exit of the device and is connected to an inlet of guidance of the generator 9. The inlet of guidance of a key 7 is connected to an exit of the generator 9, and an exit - to other diagonal of the bridge 1. ADC 8 and the generator 9 provide to the device the raised reliability and speed.

EFFECT: reliability and speed increase.

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Description

The invention relates to techniques for radio measurements and can be used in systems for automated control of radar equipment.

A device for measuring microwave power according to the copyright certificate of the USSR No. 464839, class G01R 21/00, 1973, containing a thermistor bridge, to one diagonal of which a filter, a DC amplifier, a pulse generator with a controlled frequency and a pulse shaper, a controlled key, the signal input and output of which are connected to another diagonal of the bridge, and the control input are connected in series to the output of the pulse shaper, a reference voltage source connected to the diagonal of the bridge parallel to the controlled key, a pulse counter, the input of which is connected to the output of the pulse generator with a controlled frequency, and a tibrator connected through a resistor to the filter inputs.

The signs of this device, which coincide with the essential features of the claimed device, is a thermistor bridge, to one diagonal of which a filter and a DC amplifier are connected in series, a controlled key whose output is connected to another diagonal of the bridge.

The disadvantage of this device is the low accuracy of measuring small microwave power levels, due to the temperature imbalance of the thermistor bridge.

A device for measuring microwave power according to the USSR copyright certificate No. 1134917, class. G01R 21/04, 1981, containing a thermistor bridge, to one diagonal of which a filter, a DC amplifier and a pulse generator with a controlled frequency are connected in series, a pulse shaper, a controlled key, the control input of which is connected to the output of the pulse shaper, and the output to another diagonal a thermistor bridge, a switch in series, the input of which is connected to the output of a pulse generator with a controlled frequency, and the second output to the input of a pulse shaper, an integrator and a first generator current, the output of which is connected to the output of the controlled key, an adder connected in series, the first input of which is connected to the output of the first current generator, a multiplier and a shaper of time intervals, a pulse counter, the counting input of which is connected to the second output of the switch, and the control input is connected to the output of the shaper intervals, and a second current generator, the output of which is connected to the signal input of the controlled key and to the second inputs of the adder and multiplier.

The signs of this analogue, which coincide with the essential features of the claimed device, are a thermistor bridge, to one diagonal of which are connected a series-connected filter and a DC amplifier, a current generator and a controlled key, the signal input of which is connected to the output of the current generator, and the output to another diagonal of the bridge .

The disadvantages of this device are the complexity and low reliability due to the presence of two current generators, a multiplier and an adder in the device.

The closest in technical essence to the claimed (prototype) is a device for measuring microwave power according to the copyright certificate of the USSR No. 1305606, class. G01R 21/04, 1985, containing a thermistor bridge, to one diagonal of which a filter, a DC amplifier, a switch, an integrator, a current generator and a controlled key are connected in series, the output of which is connected to another diagonal of a thermistor bridge, a pulse shaper, a pulse generator connected in series with controlled frequency and pulse counter, sequentially connected quadrator and shaper of time intervals, the input of the pulse generator with a controlled frequency is connected to the second output of the switch ator, and an output - to a pulse shaper whose output is connected to an input controls key input squarer connected to the output of the current generator, and an output driver slots - to the control input of the pulse counter.

Signs of the prototype that coincide with the essential features of the claimed device are a thermistor bridge, to one diagonal of which a filter, a DC amplifier, a switch, an integrator, a current generator and a controlled key are connected, the output of which is connected to another diagonal of the bridge.

This device is somewhat simpler than the device according to AS No. 1134917, since the adder and one of the current generators are excluded in it, and the multiplier is replaced by a simpler quadrator. However, it still remains a rather complex and relatively low-reliable device. Another disadvantage of this device, which is inherent in devices with a.c.№№464839 and 1134917, is the relatively low speed. The fact is that the measurement of power in these devices essentially reduces to measuring the low pulse repetition rate, carried out by counting the number of these pulses in a predetermined fixed time interval. To reduce the measurement error, this number should be large enough (hundreds - thousands). Therefore, the given time interval, and therefore the measurement time, should be sufficiently large.

The technical problem, the solution of which the creation of the invention is directed, is to simplify the device and increase its reliability and speed.

The technical result is achieved by the fact that in the known device for measuring microwave power, containing a thermistor bridge, to one diagonal of which are connected a filter, a DC amplifier, a switch, an integrator, a current generator and a controlled key, the output of which is connected to another diagonal of the thermistor bridge, analog-to-digital converter (ADC) and a pulse generator with a controlled duration, the output of which is connected to the control input of the managed key, the ADC input is connected to the second output in the switch, and the output is the output device and connected to the control input of the pulse generator with a controlled duration.

The set of newly introduced ADC and a pulse generator with a controlled duration is not an independent device and does not follow explicitly from the prior art, therefore, the proposed device should be considered new and having an inventive step.

The invention is illustrated by drawings, which show:

figure 1 is a structural diagram of the proposed device;

figure 2 is one of the structural diagrams of a pulse generator with a controlled duration.

The proposed device for measuring microwave power contains a thermistor bridge 1, one of the diagonals of which is connected in series to a filter 2, a DC amplifier 3, a switch 4, an integrator 5, a current generator 6 and a controlled key 7, as well as an ADC 8 and a pulse generator 9 with a controlled duration (figure 1). The input of the ADC 8 is connected to the second output of the switch 4, and the output is the output of the device and connected to the control input of the generator 9. The control input of the key 7 is connected to the output of the generator 9, and the output to the other diagonal of the bridge 1.

The device operates as follows.

In the initial state, switch 4 connects the output of amplifier 3 to the input of integrator 5, and key 7 connects the output of generator 6 to bridge 1.

After applying the supply voltage, the unbalance voltage from the output of the bridge 1 through the filter 2 is fed to the input of the amplifier 3, where it is amplified. Through switch 4, the amplified unbalance voltage is supplied to the input of the integrator 5, in which it is converted to direct voltage, which controls the current I of the generator 6, which passes through the key 7 to the bridge 1. As the transition process ends, the unbalance signal of the bridge decreases and becomes zero in the steady state .

At the command for applying to the bridge 1 of the measured _microwave power P (the command issuing device is not shown in the drawing), switch 4 is set to the position where the output of amplifier 3 is connected to the input of ADC 8 and a new circuit of the tracking system is formed: bridge 1 - filter 2 - amplifier 3 - ADC 8 - generator 9 - key 7 - bridge 1. In this case, generator 9 generates rectangular pulses of a fixed frequency fc of duration τ proportional to the numerical value of the ADC code 8 (proportional to the unbalance voltage of bridge 1). The current I of the generator 6 through the switch 7 stops for a time τ of the pulse duration of the generator 9 supplied to the control input of the key 7. The system is maintained in equilibrium by opening the switch 7 for the time τ of the pulses of the generator 9. Opening the switch 7 reduces the average power supplied to bridge 1 thermistor by the value of I ² · R ₀ · f · τ · 4 ^-1 , where R ₀ is the resistance of the thermistor at the operating point.

The power P ₁ dissipated by the thermistor before applying the measured _microwave power P is determined:

The power P ₂ dissipated by the thermistor after applying the measured _microwave power P is determined:

Since the powers dissipated by the thermistor before and after applying the measured _microwave power P are the same, you can write:

P ₁ = P ₂ .

Given equations (1) and (2) we get:

or

Using the ADC 8, a code of the numerical value N _U of the unbalance voltage from the output of the bridge 1 is generated.

The generator 9 converts it into a proportional duration τ of pulses of a fixed frequency. The transmission coefficient K ₉ of the generator 9 (the proportionality coefficient between the pulse duration τ and the unbalance voltage) is connected with the numerical value N _{U of the} code at the output of the ADC 8 by the ratio:

The coefficient K _{9 is} selected from the condition:

Therefore, equation (4) can be written as:

Given equation (3) we get:

Thus, in the steady state, the numerical value N _{U of the} code at the output of the ADC 8 corresponds to the measured microwave power.

In the proposed device in the steady state, to determine the final result, it is enough to measure the duration of one pulse of the generator 9, in contrast to the prototype device, in which to determine the final result, it is necessary to spend time counting hundreds of pulses of the same or lower frequency. This significantly improves the performance of the proposed device in comparison with the prototype.

It is easy to see that the proposed device, unlike the prototype, does not contain a quadrator, a time shaper, a pulse counter, a pulse shaper and a pulse generator with a controlled frequency, and the newly introduced ADC 8 and generator 9 are not more complex than a pulse generator with controlled frequency of the prototype device. Therefore, the proposed device is simpler than the prototype. The greater simplicity of the proposed device provides it with higher reliability. The calculation shows that the MTBF of the proposed device is approximately 10% higher than that of the prototype.

The inventive device is quite easy to implement.

The bridge can be made on a thermistor type TV-2-250A. Amplifier 2, filter 3, integrator 5 and current source 6 can be made on the basis of operational amplifiers on analog integrated circuits. Switch 4 and key 7 can be implemented on field-effect transistors. As the ADC 8 can serve as an ADC type AD9200 company Analog Devises. One of the structure options of the generator 9 of rectangular pulses with a controlled duration is shown in figure 2. It contains a generator 10 of a stable reference clock high frequency, a frequency divider 11 with a constant division coefficient, an OR element 12, a pulse counter 13, a code comparator 14 and an RS trigger 15. The input of the divider 11 is connected to the output of the generator 10 and the counter input of the counter 13, and the output is with the first input of the element 12 and the S-input of the trigger 15, the R-input of which is connected to the output of the comparator 14 and the second input of the element 12, and the output is the output of the generator 9. The zeroing input of the counter 13 is connected to the output of the element 12, and the output to the first input of the comparator 14, the second the input of which is the control input of the generator 9. The pulses of the generator 9 are formed by the trigger 15. Their frequency f is set by the division coefficient of the divider 11, and the leading edges are formed by short pulses of the generator 10, passing through the divider 11 to the S-input of the trigger 15, under which the trigger 15 is transferred . At the same time, the counter 13 is reset to zero by the same pulses passing through element 12, and the counting of the clock pulses of the generator 10 begins, arriving at the counting input of the counter 13. Upon reaching the contents of the counter 13, the number corresponding to the code at the control input of the generator 9 and the second input of the comparator 14, the latter forms a short pulse, under the influence of which the trigger 15 returns to its original state. As a result, a rectangular pulse is generated with a duration proportional to the numerical value of the code at the control input. Next, the process is repeated with a frequency f. All elements of the generator 9 can be performed on digital integrated circuits.

Claims (1)

A device for measuring microwave power, containing a thermistor bridge, to one diagonal of which a filter, a DC amplifier, a switch, an integrator, a current generator and a controlled key are connected in series, the output of which is connected to another diagonal of a thermistor bridge, characterized in that an analog- a digital converter (ADC) and a pulse generator with a controlled duration, the output of which is connected to the control input of the managed key, the ADC input is connected to the second output of the switch, and the output is It is output by the device and connected to the control input of the pulse generator with a controlled duration.

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