JP2638246B2 - Sensor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a DME (Distance) which is a short-distance navigation system.
The present invention relates to a sensor device of a transponder, which is a ground device of a Measuring Equipment (Measuring Equipment) system.

[Prior Art] The DME system is composed of a DME on-board device (interrogator) mounted on an aircraft and a DME ground device (transponder). It provides distance information from the station. That is, the transponder that has received the interrogator-emitted interrogation pulse has a predetermined delay time (50 μs).
The response pulse is transmitted later, and the interrogator obtains the distance information from the DME ground station by calculating the time from emitting the interrogation pulse to receiving the response pulse, and subtracting the delay time of 50 μs It has become.

In this DME system, the coverage and distance accuracy must be maintained at or above the specified values, and the transponder has a reception sensitivity of -95.
Less than dBm, tolerance of response delay time (50μs) ± 1.0μs
It is specified within.

The sensor device of the transponder measures what value the current performance is for various functions of the transponder according to a measurement command input to the sensor device remotely.

Among the transponder performances, the reception sensitivity (-
95dBm or less) and response delay time (50μs ± 1μs), the interrogation pulse is emitted from the sensor device (or monitoring device), and after transponder receives it, it is emitted as a response pulse. ing.
Furthermore, in terms of reception sensitivity, a question was asked at a level of -90 dBm,
The response rate to this is found. Therefore, even if the response rate was measured, it was unclear what value the current receiving sensitivity was.

Such a conventional sensor device and transponder device are configured as shown in FIGS. 4 and 5, for example.

The operation of the conventional apparatus will be described below with reference to FIGS. 4 and 5.

In FIG. 4, a pulse generator 21 generates an interrogated modulated pulse a as an interrogated pulse as shown in FIG. 6 (a).

As shown in FIG. 7, this interrogation modulation pulse (interrogation pulse) a is defined by a 1/2 amplitude point and has a pulse interval of 12 ± 0.2.
It is composed of a pair of pulses having a pulse width of 5 μs and a pulse width of 3.5 ± 0.5 μs, and its repetition frequency is, for example, 25 PPPS (Pulse Pair P).
er Second). Note that the pulse rise time and fall time are specified as predetermined values of 3.0 μs or less.

The interrogation modulation pulse a modulates the carrier signal generated by the signal generator 22 to become a 1 GHz interrogation signal b (FIG. 6 (b)).
The signal is detected at 25 and becomes a detection signal C (FIG. 6 (c)).

This is sent to the conventional sensor circuit 27, and is used as a start reference for measuring a response delay time, and is used for signal processing of reception sensitivity (response rate to an inquiry).
Further, the interrogation signal b (0 dBm) is attenuated by a predetermined value (60 dB) by the variable attenuator 23, and is interrogated from the circulator 24 to the receiver 5 of the transponder 3 through the directional coupler 2 (30 dB). Added in.

The interrogation signal b applied to the receiver 5 is amplified and detected by the intermediate frequency amplifier 8 via the band pass filter 6 and the mixer 7 to become a detection signal d, which is input to the decoder 9.
The decoder 9 detects a half amplitude point of the detection signal d and decodes an interrogation pulse having a spacing of 12 μs. The decoded interrogation pulse is delayed by the delay circuit 10 until a predetermined time and input to the coder 11, whereby the coder 11
11 generates a response pulse having a predetermined spacing (12 μs).

The response pulse is wirelessly transmitted as a response signal from the antenna 1 via the transmitter 12 and the duplexer 4, and part of the response pulse is transmitted from the directional coupler 2 to the circulator of the sensor device 20.
24, and is detected by the detector 26 to become a detected signal e (the sixth signal).
Figure (e). The detection signal e is applied to the conventional sensor circuit 27 as a response pulse. The conventional sensor circuit 27 converts the above-described interrogation pulse detection signal c into a response pulse detection signal e.
The response time is measured as the response delay time, and the number of responses to the number of questions (25 PPPS) is counted. From the following equation (1), (response rate) = (number of responses) / (number of questions) (1) ) I was looking for the response rate.

Specifically, since the response delay time is specified as 50 ± 1 μs, the measurement range is set to a gate width of 47 μs after a half-amplitude point of the interrogation pulse with sufficient margin in consideration of jitter.
μs (50 ± 3 μs) gate pulse f (Fig. 6 (f))
And the half amplitude point g of this gate pulse and response pulse
(AND of FIG. 6 (g)), and the time of the signal obtained at the output of the AND is taken as the response delay time,
The number of obtained signals was calculated from the above equation (1) to determine the response rate.

In other words, the transponder's reception sensitivity is defined as the reception sensitivity where the ratio of the number of responses to the number of questions is 70%. Therefore, in the conventional measurement of the reception sensitivity, the transponder measured by the inspector is used as a spare machine, Question pulse from 10
It was set to 00 pps, and the question level at which a 70% response of 700 pps was obtained was measured.

The transponder has a reception sensitivity of -95 dBm or less (-96 to -98 dBm standard) under normal conditions.

To monitor the reception sensitivity, a signal of -90dBm, which is 5dB stronger than the reception sensitivity (standard value: -95dBm), is asked to the transponder at 110pps or less.
It is stipulated that an alarm is generated when the power level deteriorates by 5 dB or more.

Conventional sensor devices have a -90
Generates a dBm interrogation signal at 42 pps and detects response pulses ±
When the response rate of the pulse entering the gate width of 3 μs becomes 70% or less, an alarm is generated assuming that the receiving sensitivity of the transponder has deteriorated by 5 dB or more.

[Problem to be Solved by the Invention] The conventional sensor device described above has a fixed question level (−
Although the response rate at 90 dBm) can be obtained, there is a drawback in that it is not possible to determine what value the transponder has below the originally specified -95 dBm.

That is, as a result, the conventional sensor device has a drawback that the response rate at a certain interrogation level of -90 dBm is obtained, but the value of the transponder specified at -95 dBm or less is not obtained. there were.

Furthermore, since the total number of pulses interrogating the transponder in operation is specified as 110 PPPS or less (of which 50 to 82 PPS is used by the monitoring device), measurement on the operation side is limited.

The present invention has been made to meet the demand for performance improvement of such a sensor device, and its object is to accurately determine the reception sensitivity of a transponder during operation to -95 dBm or less without affecting the DME system. It is an object of the present invention to provide a sensor device capable of performing the above.

[Means for Solving the Problems] To achieve the above object, a sensor device of the present invention has the following configuration.

That is, in the sensor device of the transponder of the DME system, the sensor device of the present invention is a signal device for detecting a plurality of signals having different gate widths for detecting a jitter of a response signal after a predetermined time after generating an interrogation signal to be transmitted to the transponder. It is configured to include a detection unit, a signal number measurement unit for measuring the number of detected signals, and a calculation processing unit for calculating a signal-to-noise ratio from the measured number using a distribution function.

Preferably, the distribution function used by the calculation processing means is a standard normal distribution function.

[Operation] In the sensor device having the above-described configuration, a probability distribution function is obtained by using a plurality of response pulse detection gates having different gate widths to determine the jitter received by the interrogation pulse due to the receiver noise, and the reception sensitivity is reduced to −95 dBm or less by a statistical method. By using the signal as a query pulse and also as a signal of the monitoring circuit of the transponder, the signal can be measured without interfering with operation.

Examples Hereinafter, examples of the present invention will be described with reference to the drawings.
First, the operation principle of the sensor device according to the present invention will be described.

In an actual transponder receiver, there is receiver noise (which has a Rayleigh distribution but is considered to be Gaussian noise in a broad sense and uses a Gaussian distribution). Therefore, the detection output of the intermediate frequency amplifier is shown in FIG. As shown, the receiver noise is superimposed. Therefore, when detecting a half amplitude point of the detection output, the half amplitude detection point fluctuates by a predetermined jitter width due to noise as shown in FIG. 8 (b).

The jitter width δtr (effective value rms) at this time is given by the following equation (2) in the case of a fixed threshold.

Here, tr is the pulse rise time, S is the signal level, N
Is the level of the receiver noise.

In this case, the distribution of the jitter depends on the receiver noise (approximated by a normal distribution) and the characteristics of the interrogation pulse (pulse rise time).
tr, the S / N ratio of the question level), the normal distribution is determined as shown in FIG. 8 (c), and the response pulse existing in the predetermined response pulse gate (FIG. 8 (d)) is also given by the following equation (3). From the standard normal distribution function Φ (Z).

For example, as shown in FIG.
= 1 .mu.s, interrogation level S / N = 14 dB, and gate width of response pulse. +-. 0.7 .mu.s, the response pulse existing within this gate width is obtained as follows.

From equation (2), Pulse rise time tr = 1 μs Question level S / N = 14 dB (× 5.01 times) When the gate width of the response pulse is ± 0.7 μs, the number of response pulses existing within this gate width is obtained as follows.

From equation (2) Response pulse 0.7μ for standard deviation σ = δtr = 0.45μs
The gate width of s is 0.7 / δtr−σ = 0.7 / 0.45−σ = 1.555σ.

The probability of being within 0.7 μs gate width (1.555σ) is
It is obtained from the standard normal distribution function (3).

Since the calculated table already exists, the standard normal distribution function Φ (z) is Φ (z) = Φ (1.555) = 0.993943 from the table value.
Is obtained.

The significance level α = 1−Φ (1.555) = 0.06057 Therefore, the probability within 0.7 μs is 1-2 (1−Φ (1.555)) = 0.87886 → 87.9%.

Here, the receiving sensitivity of the transponder is known since it is first measured by an inspector using a measuring instrument. Generally, the value is -96 to -98 dBm, and the measured value is -97 dBm here.

Note that the S / N ratio of the interrogation signal -90 dBm
The signal is 14 dBm stronger than 4 dBm, and a standard value of -97 dBm is used as the reception sensitivity at this time.

Therefore, from the initial state (known) of the interrogation pulse, the subsequent change state of the reception sensitivity or S / N can be known by measuring the response rate. That is, the reception sensitivity can be obtained by knowing the response rate from the reverse of the procedure described above. Furthermore, by preparing a plurality of gate widths for detecting response pulses having different values, the distribution function can be grasped more accurately, and the measurement accuracy of the receiving sensitivity can be improved.

FIGS. 1 and 2 show a transponder and a sensor device thereof according to an embodiment of the present invention.

1 and 2, the parts related to the present invention are the control circuit 308 and the timer circuit 30 of the sensor circuit 30.
9, gate circuit 310-311, counting circuit 312-313, function circuit 3
It is 14. Others are the same as the prior art.

In FIG. 2, a timer circuit 30 which is the same as the prior art is shown.
3. The system delay of the response pulse is measured from the gate circuit 304 and the count circuit 305 (the center of the deviation is obtained), and the measured values are used as the gate pulses h and i generated by the timer circuit 309.
The control circuit 308 is located at the center of FIG.
To work. As a result, it is possible to follow the response delay time of the transponder even if it changes.

The gate signal (h, i) from the timer circuit 309 and the output g (FIG. 3 (g)) of the response pulse detector 307 are ANDed by the gate circuit 310 to the transponder 311. It is measured by the counting circuits 312 to 313. Thereby, the distribution of the jitter of the response pulse is obtained.

The function circuit 314 calculates a signal-to-noise ratio using a standard normal distribution function from the values (response rates) obtained by the counting circuits 312 to 313, compares the signal-to-noise ratio with an initial set value (−90 dBm), Outputs the corresponding receiving sensitivity (question level when the response rate becomes 70%). For example, the initial state, the rise time of the interrogation pulse tr = 1 μs, the interrogation level −90 dBm (S / N = 14d
B) If the response rate of the gate of the response pulse at 0.7 μs is 87.9%, then the receiving sensitivity is -97 dBm (point of 70% response rate).
Given by

Then, if the performance of the receiver deteriorates and the response rate becomes 81.3%, it can be understood that the sensitivity has decreased by 3 dB.
The reception sensitivity is output as −97 + 3 = −94 dBm.

Since the interrogation pulse can be used also as a signal of the monitoring circuit of the transponder, it can be measured without any trouble in operation.

[Effects of the Invention] As described above, according to the sensor device of the present invention, the jitter received by the interrogation pulse due to the receiver noise is determined by the probability distribution function using a plurality of response pulse detection gates having different gate widths. It is possible to measure without interfering with the operation by obtaining the reception sensitivity of -95dBm or less by the conventional method and also using the signal of the monitoring circuit of the transponder as the interrogation pulse.

[Brief description of the drawings]

1 and 2 are block diagrams showing the configuration of a transponder and its sensor device according to one embodiment of the present invention. FIG. 3 is an operation time chart. FIGS. 4 and 5 are conventional transponders and their related devices. 6 is an operation time chart, FIG. 7 is an explanatory diagram of an interrogation pulse, and FIG. 8 is an explanatory diagram of jitter distribution characteristics. DESCRIPTION OF SYMBOLS 1 ... Antenna 2 ... Directional coupler 3 ... Transponder 4 ... Duplexer 5 ... Receiver 6 ... Bandpass filter 7 ... Mixer 8 ... Intermediate frequency amplifier 9 ... Decoder 10 ... Delay circuit 11 … Coder 12… transmitter 13… local oscillator 20… sensor device 21… pulse generator 22… signal generator 23… variable attenuator 24… circulator 25… detector 26… detector 28 Display circuit 30 Sensor circuit 310 Gate circuit 312 Count circuit 303 Timer circuit 314 Function circuit 305 Count circuit 304 Gate circuit 307 Response pulse detector 308 … Control circuit 309 …… Timer circuit

Claims (2)

(57) [Claims] 1. A sensor device for a transponder of a DME system, comprising: signal detection means for detecting a plurality of signals having different gate widths for detecting jitter of a response signal a predetermined time after generating an interrogation signal to be transmitted to the transponder; A sensor device comprising: a signal number measuring unit that measures the number of the detected signals; and a calculation processing unit that calculates a signal-to-noise ratio using a distribution function from the measured number. . 2. A distribution function used by said calculation processing means,
The sensor device according to claim 1, wherein the sensor device is a standard normal distribution function.