JPH0654880B2 - Jammer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interfering radio wave removing device, and more particularly, to an improvement of an interfering radio wave removing device that receives a signal other than a measurement signal in a Loran receiver or the like.

<Prior Art> In a Loran receiver or the like, if there is an interfering radio wave within the reception band, the S / N ratio is deteriorated, and therefore these interfering radio waves must be removed as much as possible.

Conventionally, as this interference radio wave removing means, a narrow band pass filter with a variable tuning frequency is swept within the fixed bandwidth of the received signal, and the presence or absence of the interference radio wave is confirmed by the signal level at this time. On the other hand, a notch filter is set to remove the interfering radio waves.

However, since the above-mentioned means mainly sweeps the frequency with a manual device, it is against the purpose of fully automatic measurement, and the signal level obtained during the frequency sweep contains not only the interference wave but also the reception target signal and white noise. Therefore, it was not easy to confirm the interference wave.

In addition, even if the interference wave can be confirmed and the frequency of the notch filter is set, the setting frequency may change depending on the ambient temperature condition of the notch filter, or the above setting may be invalid due to the change of the frequency of the interference wave itself. Therefore, there is a problem in that the notch filter must be reset every fixed time.

Therefore, a notch filter device for Loran C receiver (Japanese Patent Laid-Open No. 58-17734) has been proposed in which the frequencies of a plurality of notch filters are automatically set. This notch filter device for Loran C receiver includes a plurality of variable frequency notch filters, a tuning circuit that selects an interfering wave included in the outputs of these notch filters, and a detection circuit that detects the output of the tuning circuit. Sweep the frequency band in or near the band of Loran C by the tuning circuit,
An interference wave is detected from the check output, and a control voltage for removing the detected interference wave is sequentially assigned to the notch filter.

<Problems to be Solved by the Invention> However, the above-mentioned application (JP-A-58-17734)
In a conventional jammer removal device that automatically sets the frequencies of multiple notch filters as shown in Figure 5, the signals captured by the sweep of the tuning circuit are sequentially assigned to a limited number of notch filters. In some cases, the maximum level of jamming radio waves (usually the signal with the largest jamming effect) was not found and removed.

In view of the above problems, the present invention provides a jamming radio wave removing device that can check jamming radio waves fully automatically and efficiently set a frequency of a notch filter for jamming jamming removal without waste. It was made for the purpose.

<Means for Solving the Problems> An interference radio wave removing device according to the present invention includes a variable frequency tuning circuit for sweeping a signal input through a plurality of variable frequency notch filters within a constant bandwidth, and the variable frequency tuning circuit. A storage circuit for storing the obtained spectrum within the bandwidth, and a determination means for determining the signal component with the maximum interference effect from the content stored in the storage circuit based on predetermined signal level conditions and frequency conditions. Of the plurality of variable frequency notch filters, command means for tuning and operating the blocking frequency of an unused variable frequency notch filter to the frequency of the signal component determined by the determination means.

<Operation> In the interference radio wave removing device of the present invention, the variable frequency tuning circuit sweeps the signal input through the plurality of variable frequency notch filters within a constant bandwidth, and the storage circuit obtains the band obtained by the variable frequency tuning circuit. Memorize the spectrum within the width,
Based on the predetermined signal level condition and frequency condition, the judging means judges the signal component with the maximum interference influence from the contents stored in the memory circuit, and the command means further uses the variable frequency notch filter among the plurality of unused variable frequency notch filters. The stop frequency of the variable frequency notch filter is tuned to the frequency of the signal component determined by the determination circuit.

As a result, jamming radio waves are checked automatically,
In addition, the limited number of notch filters can efficiently remove interference waves having a high degree of influence.

<Embodiment> FIG. 1 is a block diagram of an interfering radio wave removing device in a Loran C receiver according to an embodiment of the present invention, FIG. 2 is a spectrum of a signal received in a constant bandwidth, and FIG. 4 is a waveform diagram of the output signal A of the D / A converter 10 and the input voltage signal B of the notch filters 2 to 5 in the figure,
FIG. 5 is a timing chart of the multiplexer 11 in FIG. 1, and FIG. 5 is a flowchart showing the processing procedure of the CPU 13 in FIG.

In FIG. 1, an input signal from an antenna 1 is amplified by an amplifier 6 through a plurality of variable frequency notch filters 2, 3, 4 and 5, and a variable frequency tuning circuit 7 selects only a specific frequency within a certain bandwidth. , Is logarithmically amplified by the logarithmic amplifier 8 and converted into a DC voltage by the detection circuit 9. In the figure, B1, B2, ... B7 are buffer circuits.

The variable frequency notch filters 2 to 5 are voltage control type narrow band stop filters, and the variable frequency tuning circuit 7 is a voltage control type narrow band pass filter. By using variable capacitance diodes having relatively uniform characteristics, If the control voltage is constant, the blocking frequency or the passing frequency is substantially the same. The frequency control of the variable frequency notch filters 2 to 5 and the variable frequency tuning circuit 7 is performed by data output to the D / A converter 10 and selection of the multiplexer 11.

That is, the selection of the multiplexer 11 is time-division controlled as shown in FIG. 4, and accordingly, the output voltage of the D / A converter 10 has a time-division waveform as shown in FIG. Fourth
In the figure, the shaded area is a high impedance section, which means that the corresponding notch filter is not selected during this period, and the corresponding notch filters 2 to 5 or the tuning circuit 7 is selected in other high level sections. It means that. Therefore, the notch filters 2 to 5 are sequentially selected at timings to to t3, the tuning circuit 7 is selected at t4, and any notch filter or tuning circuit is not selected at t5. As is apparent from the correspondence between FIG. 3 and FIG. 4, the control voltage is applied to the notch filters 2 to 5 and the tuning circuit 7 in a time division manner in each section from to to t4. In the section of t5, the output voltage of the D / A converter 10 sequentially increases from 0 to the maximum value. This signal is not given to the notch filters 2 to 5 or the tuning circuit 7, but is given to the comparator 12 shown in FIG. 1 as the comparison voltage Vc.

The output signal of the tuning circuit 7 is logarithmically amplified by the logarithmic amplifier 8, converted into a voltage signal representing the signal level thereof by the detection circuit 9, and given to the comparator 12. Comparator 12 is D /
The signal levels of the comparison voltage Vc output from the A converter 10 and the output voltage VL from the detection circuit 9 are compared. For example, when VL is larger than Vc, a high level is output, and in the opposite case, a low level is output. The output Vc of the D / A converter 10 gradually increases from 0 as shown in FIG. 3 in the section of t5, so the output of the comparator 12 is
At the time of VL≤Vc, the high level changes to the low level. When the output of the comparator 12 falls, the CPU
13 is interrupted. As a result, the CPU reads the input value of the D / A converter 10 into a predetermined area of the RAM 14. A / D conversion is performed by the above operation.

In this way, the control voltages of the notch filters 2 to 5 and the tuning circuit 7 are set at to to t4, and the signal level at the notch filter condition and the tuning frequency is sampled at t5. And this to-t5 is 1
As a cycle, the frequency is sequentially changed from a low frequency range to a high frequency range within a certain set bandwidth, and the frequency is swept, and a signal level, that is, a spectrum at each frequency is stored.

When the D / A converter 10 is 8 bits, both the frequency and the signal level within the set bandwidth are 1 /
A resolution of 256 is obtained, and there is no problem in practical use.

When one sweep is completed, the signal level, that is, the spectrum at each frequency as shown in FIG. 2 is accumulated in the RAM 14. From this spectrum, the interfering wave having the largest influence is determined based on the predetermined signal level condition and frequency condition.

In this case, the criterion for determining the degree of influence of the interference wave is determined by preset conditions such as the difference from the center frequency, the level of the interference wave, and the level difference from the white noise level.

For example, in FIG. 2, it is determined that the disturbing wave P1 having a high level near the center frequency becomes the first place, and P2 and P3 are the following disturbing waves.

If the first order interference wave is determined by the above determination, the blocking frequency of the first variable frequency notch filter 2 is set to the frequency of the interference wave. Interference effect After the maximum interference wave is removed by the first variable frequency notch filter 2, the interference frequency level of the whole band is measured again by the variable frequency tuning circuit 7, and the interference effect in each measurement cycle is similarly performed. The highest disturbance frequency is assigned to the unused notch filter.

A series of processing procedures of the CPU 13 described above will be described with reference to the flowchart of FIG.

First, voltage data to be applied to each notch filter such that the stop frequencies of the notch filters 2 to 5 are out of the sweep frequency band are set in a predetermined area of the RAM 14 (n1). Then, the voltage data for the tuning circuit so that the tuning frequency of the tuning circuit 7 becomes the lowest frequency (70 KHz) of the sweep frequency band is set in a predetermined area of the RAM 14 (n2). afterwards,
As shown in to to t3 in FIGS. 3 and 4,
Each notch filter is selected by the multiplexer 11, and corresponding voltage data is output to the D / A converter 10 (n3). Subsequently, the tuning circuit 7 is selected in the section of t4, and the corresponding voltage data is output to the D / A converter 10 (n4). Then t
In the section of 5, the selection of the notch filter or the tuning circuit by the multiplexer 11 is set to the non-selected state (n5). After that, the initial value 0 is set in the RAM as the comparison voltage data (Vc).
14 areas (n6) and set the data to D / A
Output to the converter 10 (n7). The comparison voltage data (Vc) is sequentially increased until the comparison voltage data (Vc) reaches the maximum value of 255 (n8 → n9 → n7 ...
・). If the output of the comparator 12 falls from the high level to the low level while the comparison voltage data (Vc) rises, the CPU 13 is interrupted. The CPU stores the comparison voltage data (Vc) by the interrupt process as shown in FIG. Through the above processing, the signal level A / D conversion at the initial tuning frequency 70 KHz and its storage are performed.

After that, the tuning circuit voltage data is increased by one step (n10 → n11) (at this time, since the tuning circuit voltage data has not reached the maximum value, the determination in step n10 is No.
Becomes ). Then, the signal level at that frequency is A / D converted by performing the processing from step n3 again, and the value is stored. The above process is repeated until the tuning circuit voltage data reaches the maximum value (255), that is, the tuning frequency of 130 KHz, and the tuning frequency is swept. Thereby, the signal level (spectrum) at each frequency is obtained in a predetermined area of the RAM 14. Then, the interference wave having the maximum influence is discriminated from this spectrum based on a predetermined signal level condition and frequency condition (n10 → n).
12). Then, the voltage data corresponding to the frequency of the extracted interference wave is stored in the corresponding area of the RAM 14 as the voltage data for the unused notch filter (n13 → n14).
→ n15) (Here, it is assumed that there is an interfering wave).

After that, the tuning circuit voltage data is set to the initial value 0 again, and the tuning frequency is swept in the same manner. Therefore, at this time, the notch filter 2 removes the interference wave, and the other notch filters 3 to 5 are set outside the band, so that the spectrum is obtained in a state where the interference wave is removed by the notch filter 2. As a result, if there is no interference wave to be removed, without setting the data for the notch filter,
The control voltage corresponding to the data for each notch filter that has already been set is repeatedly applied to each notch filter every cycle (n13 → n2 → n3 ...). Similarly, when there is no unused notch filter, the control voltage corresponding to the already set data for each notch filter is repeatedly applied to each notch filter every cycle (n
14 → n2 → n3 ...).

When setting the voltage data for the notch filter,
The notch to be applied by changing the voltage data for the notch filter by about 10 steps before and after the voltage data for the tuning circuit corresponding to the extracted interference wave frequency, and searching for the value at which the signal level becomes the lowest. It is desirable to find the optimum voltage data for the filter. As a result, it is possible to eliminate the deviation of the frequency setting due to the variation in the characteristics of the tuning circuit and the notch filter.
The search operation can be performed by performing the same sweep used for measuring the interference wave by the variable frequency tuning circuit 7 on the notch filter.

As described above, the notch filters 2 to 5 are sequentially assigned from the high-level disturbing waves, and the disturbing waves of the fourth rank are simultaneously removed. If a certain time has elapsed after the setting of the interference wave removal frequency, the set notch filter is reset. This is to prevent a shift in the blocking frequency due to a change in the frequency of the jamming radio wave and a change in the frequency due to the temperature conditions of the notch filters 2 to 5. In addition, since it is possible that the interfering wave may disappear in the middle of the process, the preset notch filter is temporarily set outside the band and compared with the level at which the interfering wave is detected, and the presence or absence of the interfering wave is compared. It is desirable to confirm. It should be noted that, in the decker receiving device, it is necessary that this fixed time is not an integral multiple of 20 seconds of the transmission period of the decker signal.

This operation of confirming the presence or absence of the interfering wave is repeated several times in succession. As a result, if it is confirmed that there is no interfering wave, it can be determined that the interfering wave has disappeared, and the notch filter can be set outside the band.

Further, when all the notch filters are set and a strong disturbance appears, the notch filter (2, 3, 4 or 5) for removing the lowest-level disturbance is switched and applied. It may be configured to.

<Effects of the Invention> As described above, according to the present invention, in the case of removing an interfering wave, first, the bandwidth is first swept over the entire width, and a predetermined signal level condition among signals recognized as a spectrum is set. Since the one with the maximum interference influence is determined based on the frequency conditions and the interference wave is removed, the frequencies can be sequentially assigned to the notch filter from the interference wave with the large influence, and the interference wave removal effect is improved. It becomes very high, and the interference wave removal within the bandwidth can be performed completely automatically without requiring any manual operation.

When the power to the receiver is cut off, the RAM is backed up with a battery to protect the memory and store information such as voltage data for the notch filter, so that the notch filter is activated immediately after the power is turned on. It is also possible.

[Brief description of drawings]

FIG. 1 is a block diagram of an interfering radio wave removing device according to an embodiment of the present invention, FIG. 2 is a diagram showing signal levels at respective frequencies received within a fixed bandwidth, and FIG. 3 is D / of FIG. A
The figure which shows the output voltage waveform of the converter 10, FIG.
It is a figure which shows the operation timing of the multiplexer 11 of the figure. 5A to 5D are flowcharts showing the processing procedure of the CPU of FIG.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hayato Torii 9-52 Ashihara-cho Nishinomiya-shi, Hyogo Furuno Electric Co., Ltd. (72) Inventor Shinichi Fukumoto 9-52 Ashihara-cho Nishinomiya-shi Hyogo Prefecture Furuno Electric Co., Ltd. In-house company (56) References JP-A-58-17734 (JP, A)

Claims (1)

[Claims] 1. A variable frequency tuning circuit for sweeping a signal input through a plurality of variable frequency notch filters within a constant bandwidth, and a storage circuit for storing a spectrum within the bandwidth obtained by the variable frequency tuning circuit. And a determination means for determining a signal component having the maximum interference influence from the contents stored in the storage circuit based on a predetermined signal level condition and a frequency condition, and an unused portion of the plurality of variable frequency notch filters. 2. An interference radio wave removing device comprising: a command means for tuning the stop frequency of the variable frequency notch filter to the frequency of the signal component judged by the judging means.