JP7528354B2 - Wireless devices - Google Patents

Description

The present invention relates to radio equipment used, for example, in air traffic control, and in particular to radio equipment capable of quickly and accurately detecting the presence or absence of interference.

Description of the Prior Art
In wireless communication, when multiple wireless stations transmit simultaneously at the same frequency, interference occurs at the receiving station.
For example, in air traffic control, there have been reports of interference caused by simultaneous transmissions from multiple aircraft radio stations, which could lead to serious incidents.

Air traffic control radio communication uses AM modulation, and when there is interference, audio overtones and strange noises occur at the receiving end. Air traffic controllers use these to determine whether there is interference or not.
However, when the relative level difference between the signals in an interference state is 20 dB or more, the weak signal is suppressed by the strong signal, and the abnormal sound may not be recognized, making it difficult to detect interference.
Furthermore, in the past, since the judgment was based on human hearing and experience, there was a risk of overlooking detection.

[Related Technology]
Incidentally, a conventional technique for detecting the presence or absence of interference in a wireless device is disclosed in Japanese Patent No. 6647424 "Wireless Device" (Patent Document 1).
Patent Document 1 describes a radio device that converts a received signal output from an ADC to a baseband frequency, converts it to an optimal sampling rate, applies window processing, and then performs FFT (Fast Fourier Transform) processing, detects peak power of the output of the FFT processing, and detects an interference state based on the number of detected peaks.

Patent No. 6647424

However, with conventional wireless devices, air traffic controllers had to listen to signals to determine whether or not there was interference, which resulted in low detection accuracy and the risk of interference being overlooked.
Furthermore, conventional wireless devices have the problem that they are not capable of reporting the degree of danger according to the level of interference.

Furthermore, Patent Document 1 does not mention performing FFT using overlap processing to shorten the time required to detect interference and improve detection accuracy.

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a wireless device that can quickly and accurately detect the presence or absence of interference, and further notify the user of the level of risk according to the degree of interference, thereby enhancing safety.

The present invention, which solves the problems of the above-mentioned conventional examples, is a wireless device that detects interference occurring on a receiving side when a plurality of wireless devices simultaneously transmit radio waves at the same frequency in one wireless communication area, and includes a window processing unit that performs window processing on the received signal in order to optimize the results of subsequent fast Fourier transform (FFT) processing, a rate conversion unit that rate converts the signal output from the window processing unit to a high frequency, extracts FFT frames each containing a specific number of samples by overlapping while shifting the frames by a fixed number of samples, and sequentially outputs the FFT frames every fixed number of samples , an FFT unit that performs a fast Fourier transform on the signal of the FFT frame output from the rate conversion unit so as to have a frequency-level relationship, and an interference detection unit that detects peak power in a band including the carrier frequency output from the FFT unit, and detects interference by determining the interference state every fixed number of samples based on the number of peaks detected.

The present invention also provides, in the wireless device, an interface unit that acquires time information via the NTP protocol or GPS.

In addition, in the above wireless device, the present invention is connected to a memory device that stores data on the interference state when interference is detected by the interference detection unit.

In addition, in the above-mentioned wireless device, the present invention is connected to a computer device that reads out and displays interference status data from the storage device.

In addition, in the wireless device of the present invention, when the computer device receives data indicating that an interference state exists, it displays a warning indicating that the risk is low and starts timing, and if the interference state continues for longer than a specific time, it displays an alarm indicating that the risk is high.

The present invention also provides a wireless device that increases the number of samples per frame in FFT processing and increases the number of overlaps.

In addition, in the above-mentioned wireless device, the present invention is provided with a window processing unit, an FFT unit, and an interference detection unit for each of multiple frequencies corresponding to multiple wireless communication areas.

According to the present invention, a wireless device that detects interference occurring on a receiving side when a plurality of wireless devices simultaneously transmit radio waves at the same frequency in one wireless communication area includes a window processing unit that performs window processing on the received signal in order to optimize the results of subsequent fast Fourier transform (FFT) processing, a rate conversion unit that rate converts the signal output from the window processing unit to a high frequency, and cuts out FFT frames including a specific number of samples by overlapping while shifting the FFT frames by a fixed number of samples, and sequentially outputs the FFT frames every fixed number of samples, an FFT unit that performs fast Fourier transform on the signal of the FFT frame output from the rate conversion unit to a relationship between frequency and level, and an interference detection unit that detects peak power in a band including the carrier frequency output from the FFT unit, and detects interference by determining the interference state every fixed number of samples based on the number of detected peaks. This wireless device has the effect of shortening the time required to detect the presence or absence of interference and increasing the number of FFT points to improve detection accuracy, thereby enabling the presence or absence of interference to be determined quickly and with high accuracy.

In addition, according to the present invention, the wireless device is connected to a storage device that stores data on the interference state when interference is detected by the interference detection unit, which has the effect of making it possible to use the data on the interference state for analysis.

In addition, according to the present invention, the wireless device is connected to a computer device that reads out and displays data on the interference state from the storage device, thereby having the effect of being able to notify the user of the interference state by displaying it.

Furthermore, according to the present invention, when the computer device receives data indicating an interference state, the wireless device displays a warning indicating that the risk is low and starts timing, and if the interference state continues for longer than a specific time, displays an alarm indicating that the risk is high. This has the effect of notifying the user of the risk according to the level of interference, thereby enhancing safety.

In addition, according to the present invention, a wireless device is provided that increases the number of samples per frame in FFT processing and also increases the number of overlaps, thereby reducing the noise floor and further improving detection accuracy.

In addition, according to the present invention, the above-mentioned wireless device is provided with a window processing unit, an FFT unit, and an interference detection unit for each of a plurality of frequencies corresponding to a plurality of wireless communication areas, and thus has the effect of being able to detect the presence or absence of interference in a plurality of wireless communication areas.

FIG. 2 is an explanatory diagram showing a configuration example of the present wireless device. FIG. 2 is a configuration block diagram of a receiving device 4. 4 is a flowchart showing a process in the interference detection device. FIG. 1 is an explanatory diagram showing an overview of overlap processing in an interference detection device. FIG. 11 is an explanatory diagram showing an example (1) of a waveform when interference is detected. FIG. 11 is an explanatory diagram showing an example (2) of a waveform when interference is detected.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.
[Outline of the embodiment]
A wireless device according to an embodiment of the present invention (this wireless device) includes an interference detection device that detects the presence or absence of interference that occurs on the receiving side when a plurality of wireless devices transmit using the same frequency. In the interference detection device, a window processing unit performs window processing on a received signal having a carrier frequency as a center frequency in order to optimally perform subsequent FFT processing. A rate conversion unit rate converts the output signal from the window processing unit at a high frequency and outputs frames containing a specific number of samples while overlapping them. An FFT unit performs FFT processing on the signal output from the rate conversion unit on a frame-by-frame basis to output the relationship between frequency and level. An interference detection unit detects peaks of the carrier output from the FFT unit and determines that an interference state exists if multiple peaks are detected. By performing FFT processing with overlapping frames, the time required to detect the presence or absence of interference can be shortened and the number of FFT points can be increased to improve detection accuracy, making it possible to quickly and accurately determine the presence or absence of interference.

In addition, when this wireless device detects interference, it outputs a warning indicating that interference is present and begins measuring the duration, and if the duration exceeds a certain period of time, it outputs an alarm indicating a high level of danger, thereby reporting the level of danger in real time and calling attention to the danger.

In addition, this wireless device is equipped with the above-mentioned interference detection device for each frequency corresponding to multiple wireless communication areas, and is capable of detecting the presence or absence of interference in multiple wireless communication areas.

[Example of the configuration of this wireless device: Figure 1]
An example of the configuration of this wireless device will be described with reference to Fig. 1. Fig. 1 is an explanatory diagram showing an example of the configuration of this wireless device.
As shown in FIG. 1, the wireless device includes an antenna 1, a GPS (Global Positioning System) antenna 2, a high-frequency unit 3, a receiving device 4, a network device 5, a personal computer 6, and an external storage device 7.

The antenna 1 transmits and receives radio signals to and from a radio device (radio station) installed on the aircraft.
The GPS antenna 2 receives GPS signals from a plurality of GPS satellites and outputs the GPS reception signals to the receiving device 4. The receiving device 4 obtains position information and time information based on the GPS reception signals.

The high frequency unit 3 performs frequency conversion and amplification associated with the transmission and reception of radio signals. Specifically, the high frequency unit 3 amplifies the radio signal from the antenna 1, down-converts it to an IF signal, and outputs it to the receiving device 4. It also converts the IF signal from the receiving device 4 into a high frequency signal and outputs it to the radio antenna 1.

The receiving device 4 includes a demodulation section, which demodulates the received signal and outputs the received sound to a speaker.
The receiver 4 of the wireless device is also provided with an interference detection device for detecting the presence or absence of interference in the received signal, and detects the presence or absence of interference in the input received signal and outputs the result to the personal computer 6. The interference detection device will be described later.

Furthermore, the receiving device 4 includes a GPS interface unit that acquires time information based on the GPS reception signal from the GPS antenna 2 .
The interference detection device then adds time information to the detection result and outputs it to the personal computer 6 or the external storage device 7, which will be described later.
Here, the time information is acquired from a GPS reception signal, but it may also be provided with a network interface unit that acquires NTP (Network Time Protocol) time information from a network signal.

The wireless device is also provided with a transmitter that modulates the input transmission sound and outputs it to the high frequency section 3, but this is not shown here. The receiver 4 may also be configured as a transceiver to perform modulation and demodulation associated with transmission and reception.

The network device 5 connects the receiving device 4 to a network. In this case, a personal computer 6 and an external storage device 7 are connected via the network device 5, but it may also be connected to an external network such as the Internet.

The PC 6 is a terminal operated by an operator such as an air traffic controller, and displays warnings and alerts indicating the presence or absence of interference and the level of interference based on the information on interference (interference state data) from the receiving device 4. It is also equipped with a speaker that outputs received audio and a microphone that inputs transmitted audio.

The external storage device 7 stores the information related to interference output from the receiving device 4, and outputs the stored information upon request from the personal computer 6. By storing data in the external storage device 7, it is possible to analyze the state of interference.

[Configuration of receiving device: Figure 2]
Next, the configuration of the receiving device 4 will be described with reference to Fig. 2. Fig. 2 is a block diagram showing the configuration of the receiving device 4.
The receiver 4 demodulates the received signal and outputs the received sound, and also detects the presence or absence of interference for a narrow band signal centered on a predetermined carrier frequency.
As shown in FIG. 2 , the receiving device 4 includes an ADC (Analog Digital Converter) 11, a frequency conversion unit 12, a first rate conversion unit (rate conversion unit (1)) 13, a second rate conversion unit (rate conversion unit (2)) 14, a window processing unit 15, a third rate conversion unit (rate conversion unit (3)) 16, an FFT unit 17, an interference detection unit 18, a power detection unit 19, a demodulation unit 21, and a DAC (Digital Analog Converter) 22.
Of these, the portion including the second rate conversion section 14, the window processing section 15, the third rate conversion section 16, the FFT section 17, the interference detection section 18, and the power detection section 19 constitutes an interference detection device.
In this embodiment, a bandpass filter that passes a narrow band centered on a predetermined carrier frequency is provided in front of the ADC 11 .

The ADC 11 converts an analog signal of an IF frequency or an analog signal of an orthogonalized baseband frequency into a digital signal.
The frequency converter 12 converts the digital signal of the IF frequency into a baseband frequency, but when an orthogonalized digital signal of the baseband frequency is input, the frequency converter 12 can be omitted.
The first rate converter 13 converts the baseband frequency signal into a sampling rate (for example, 1 MHz) optimal for demodulation processing.

The demodulation unit 21 amplifies or attenuates the signal output from the first rate conversion unit 13 to an appropriate level, and then AM demodulates the signal.
The DAC 22 converts the demodulated digital signal into an analog signal and outputs audio.

The second rate converter 14 further converts the input signal into a sampling rate (for example, 24 kHz) suitable for the window processing in the subsequent stage.
The window processing unit 15 processes the signal output from the second rate conversion unit 14 using a window function so as to optimize the FFT result at the subsequent stage.

The third rate conversion unit 16 converts the signal output from the window processing unit 15 into an FFT frame including the number of samples that is the unit of FFT processing, into a sampling rate optimal for FFT processing (e.g., 200 MHz), and outputs the converted FFT frame.
At this time, the third rate conversion unit 16 outputs frames while overlapping a preset number of samples. The third rate conversion unit 16 corresponds to a rate conversion unit recited in the claims.

When the size of the FFT frame is fixed, it is possible to improve the frequency resolution of the FFT by narrowing the sampling frequency of the received signal even further than the bandwidth required for demodulation. This is determined by the frequency deviation of the transmitter. The sampling frequency is adjusted to the extent that the FFT frequency resolution can identify fluctuations in the radio's transmission frequency, and the relationship between frequency and reception level is calculated by performing FFT processing.

The FFT unit 17 performs FFT processing on the input FFT frame as a unit, and converts it into a relationship between frequency and level, thereby detecting a peak of the power level at the carrier frequency.
The FFT unit 17 of the wireless device outputs the FFT processing results for each of the overlapped FFT frames. By overlapping, multiple FFT frames containing the same samples are subjected to FFT processing, which improves detection accuracy and prevents interference from being overlooked.

The interference detection unit 18 detects the number of power peaks based on the relationship between the frequency and level from the FFT unit 17, and detects the presence or absence of interference. Specifically, if there is one peak, it is determined that there is no interference, and if there are two or more peaks, it is determined that there is interference, and outputs the determination result to the computer 6.

At this time, the interference detection unit 18 inputs the peak power power value (peak power value) in the FFT processing result from the power detection unit 19 described later, and if the peak power value is less than a predetermined threshold value, it is not detected as a peak.

This is because minute increases and decreases in the noise floor level are not detected as peaks, and only peak powers above a certain level are detected as peaks.
The threshold value of the peak power value for detecting the peak is set according to the radio wave reception conditions (radio wave conditions), and the setting can be changed by an external signal from the personal computer 6 or the like.

The power detection section 19 detects the power of the signal from the FFT section 17 and outputs the peak power value to the interference detection section 18 .
In addition, when interference occurs, a beat (waveform fluctuation) occurs depending on the power difference between each modulated wave, so the power detection unit 19 may be configured to detect and output the interference level based on that.
Specifically, the power detection unit 19 inputs the signal output from the first rate conversion unit 13, detects its power value, detects the power difference between the two modulated waves from the amount of beat fluctuation, and outputs this as an interference level to the personal computer 6, etc.
Then, the operator of the personal computer 6 may make a final judgment as to whether or not there is interference, taking into account the result of the interference judgment from the interference detection unit 18 .

[Interference detection process: Figure 3]
Next, the processing in the interference detection device shown in Fig. 2 will be described with reference to Fig. 3. Fig. 3 is a flow chart showing the processing in the interference detection device. Note that the processing numbers in Fig. 3 (the numbers following "S") correspond to the reference numerals of the components in Fig. 2.
As shown in FIG. 3, in the interference detection device, when a received signal that is band-limited around a carrier frequency is input, the input signal is converted into a digital signal by the ADC 11 (S11), and then converted into a baseband frequency by the frequency conversion unit 12 (S12).

Then, the baseband frequency signal is rate converted (rate conversion (1)) to a rate suitable for demodulation in the first rate conversion unit 13 (S13), rate converted (rate conversion (2)) to a rate suitable for window processing in the second rate conversion unit 14 (S14), and window processing is performed in the window processing unit 15 (S15).

Furthermore, the windowed signal is rate converted (rate conversion (3)) to a rate suitable for FFT in the third rate conversion unit 16 (S16), and FFT processing is performed on a frame-by-frame basis in the FFT unit 17, and the relationship between frequency and level is output (S17).

Then, the interference detection unit 18 performs an interference detection process (S18).
In the interference detection process of process S18, the interference detection unit 18 detects the number of peaks having a power value equal to or greater than a predetermined threshold based on the FFT result output from the FFT unit 17, and determines whether the number of peaks is two or more (S181).

In step S181, if the number of peaks is two or more, the interference detection unit 18 determines that interference exists and outputs a result of "interference exists" to the personal computer 6 and the external storage device 7 (S182). At that time, the interference detection unit 18 outputs the detection result of interference existence together with the time information acquired from the GPS reception signal.
Also, in process 181, if the number of peaks is one, the interference detection unit 18 determines that there is no interference, and outputs the result of "no interference" with time information to the personal computer 6 and the external storage device 7 (S183).
In this manner, processing is carried out in the interference detection device of this wireless device.

[Overview of overlap processing: Figure 4]
Next, an overview of the overlap processing of FFT in the interference detection device of this wireless device will be described with reference to Fig. 4. Fig. 4 is an explanatory diagram showing an overview of the overlap processing in the interference detection device.
4 shows a case where the received signal shown in the upper part is subjected to overlap FFT processing, with the horizontal axis representing time.
As described above, in this wireless device, the third rate conversion unit 16 converts the rate to 200 MHz, extracts frames containing a predetermined number of samples by shifting them by a specific number of samples (here, one sample), and outputs the frames with overlapping to the FFT unit 17, which then sequentially performs FFT processing on the input frames and outputs the results.
In FIG. 4 , frames (1), (2), (3), etc. are overlapped by being shifted by one sample each. Therefore, after the result of FFT processing for frame (1) is output, the results of FFT processing for frames (2), (3), etc. are output with a delay of one sample time.

In this way, in this wireless device, FFT processing is performed every sample time by overlapping, so that the detection result of the presence or absence of interference can be notified more quickly than in the past.
Similarly, when a state where there is interference changes to a state where there is no interference, the notification can be given more quickly than in the past.

In addition, because FFT processing is performed for the same sample the number of times it overlaps, the detection accuracy can be significantly improved. This wireless device can detect interference even when the relative level difference between signals is 40 dB or more, preventing interference from being overlooked.

Furthermore, it is possible to increase the number of samples per frame used for FFT processing and increase the number of overlaps, thereby reducing the noise floor and further improving detection accuracy.

[Warning/alarm display]
In this wireless device, when interference is detected, the personal computer 6 outputs a warning or alarm to notify the operator.
For example, when the control unit of the PC 6 receives an input of "interference detected" from the interference detection unit 18 of the receiving device, the control unit of the PC 6 outputs an alarm display of "warning" on the display unit. The warning indicates an interference state with a relatively low degree of danger.
At the same time, the control unit of the PC 6 starts measuring time, and when the measured time exceeds a preset specific time, it outputs an alarm display of "Warning." The warning indicates that a dangerous interference state exists.
When "no interference" is input, the control unit of the PC 6 resets the measurement time.

This allows air traffic controllers and others to know in real time that interference is occurring and the extent of the interference, and can alert aircraft to the situation and prevent serious incidents from occurring.
In particular, since it is possible to tell at a glance whether interference is occurring, it is possible to reduce oversights compared to when listening for interference with the ear, and furthermore, it is possible to reduce the burden on air traffic controllers.

Also, although an example of displaying warnings and alerts in real time has been described here, in this wireless device, information relating to interference from the receiving device 4 (date and time, reception status, presence or absence of interference, power value data, waveform data, etc.) is stored in the external storage device 7, so that the personal computer 6 or an analysis terminal can read out the data from the external storage device 7 and perform detailed analysis.
The information on interference corresponds to the data on the interference state described in the claims. The information on interference may also include various data on a state without interference.

For example, it is possible to calculate the duration of interference by taking the time when the interference detection result changes from "no interference" to "interference" as the interference start date and time, and the time when the interference detection result changes from "interference" to "no interference" as the interference end date and time.
Similarly, it is also possible to determine the duration of interference based on the waveform data by determining the timing when two peaks are detected as the start of interference and the timing when the peak returns to one as the end of interference.
Furthermore, the personal computer 6 may display a list of interference history based on data read from the external storage device 7, so that the state of interference occurrence can be known at a glance.

[Examples of waveforms when interference is detected: Figures 5 and 6]
Next, examples of waveforms when interference is detected will be explained using Figures 5 and 6. Figure 5 is an explanatory diagram showing an example of a waveform when interference is detected (1), and Figure 6 is an explanatory diagram showing an example of a waveform when interference is detected (2). Figures 5 (1) to 6 (6) show the waveforms detected in a series of interference states in chronological order.

In Figures 5 and 6, the upper graph shows the FFT output result, and the horizontal axis is frequency. The lower graph shows the observed frequency band, which indicates the band in which the received signal was observed in the upper graph. Also, the scales of the horizontal axes in Figures 5 and 6 do not match.

As shown in Figure 5 (1), when aircraft A is transmitting, the FFT result shows a power peak (first peak) at a specific frequency. In this state, there is one peak and no interference.

Then, as shown in Figure 5 (2), when aircraft B starts transmitting on the same frequency, a power peak due to aircraft B appears. The received signal from aircraft B is not yet very strong, and there is a large level difference with the received signal from aircraft A, but in this wireless device, a second peak is detected from the FFT results, and a second peak also appears in the waveform, so that the interference detection unit 18 can quickly detect the start of interference, and if the waveform is displayed on the PC 6, it can also be easily recognized from the waveform.

When interference occurs, even if the transmitting side is transmitting at the same frequency, multiple AM modulated carrier signals can be detected at the receiving side due to fluctuations in the original oscillation and Doppler shift. This wireless device makes use of this phenomenon to detect the peak power of the carrier signal, and if there are two or more peaks with a power value above a threshold, it determines that interference has occurred.
As described above, in real-time processing, the control unit of the personal computer 6 starts measuring the interference time in this state and displays a warning that "interference exists."

Furthermore, as shown in FIG. 5(3) and FIG. 6(4), as aircraft B approaches, the second peak due to aircraft B becomes larger, and the interference state continues.
6(5), when the transmission from aircraft A ends, the first peak becomes smaller and the interference ends. The interference detection unit 18 detects the end of the interference when the power level of the first peak falls below a certain value.
At this point, the control unit of the personal computer 6 stops counting the interference time.
In FIG. 6(6), aircraft B is transmitting and no interference is occurring.

These waveform data can be displayed in real time on the personal computer 6 and are also stored in the external storage device 7, so that the data can be read out at a later date and used for analysis.

[Detects interference on multiple frequencies]
2 shows an example of a receiving device that detects the presence or absence of interference at one carrier frequency, but it is also possible to use RF direct sampling to detect the presence or absence of interference at multiple frequencies, including carrier frequencies used in adjacent sectors.

Specifically, the receiving device is configured to include filters that pass a plurality of different frequencies, ADCs corresponding to the respective filters, and interference detection devices corresponding to the respective ADCs.
Then, each ADC converts the frequency that has passed through each filter into a digital signal, and the corresponding interference detection device detects the presence or absence of interference for each input frequency and outputs the result to the PC 6. The PC 6 identifies the frequency according to the interference detection device that detected it, and displays the detection result, warning, and alarm with the frequency.
The operation of each interference detection device is similar to the above-mentioned example.
This makes it possible for the present wireless device to simultaneously detect the presence or absence of interference across multiple sectors, thereby improving the reliability of air traffic control over a wide area.

[Effects of the embodiment]
According to this wireless device, an interference detection device is provided that detects the presence or absence of interference that occurs on the receiving side when a plurality of wireless devices transmit using the same frequency. In the interference detection device, a window processing unit 15 performs window processing on a received signal having a carrier frequency as a center frequency in order to optimally perform subsequent FFT processing. A rate conversion unit 16 rate converts the output signal from the window processing unit 15 at a high frequency and outputs frames containing a specific number of samples while overlapping them. An FFT unit 17 performs FFT processing on the signal output from the rate conversion unit 16 on a frame-by-frame basis to output the relationship between frequency and level. An interference detection unit 18 detects peaks of the carrier output from the FFT unit 17 and determines that an interference state exists when a plurality of peaks are detected. Therefore, by performing FFT processing with overlapping frames, the time required to detect the presence or absence of interference can be shortened and the number of FFT points can be increased to improve detection accuracy, resulting in the effect of being able to quickly and accurately determine the presence or absence of interference.

In addition, according to this wireless device, when the control unit of the personal computer 6 receives data indicating the presence of interference from the interference detection unit 18, it outputs a warning indicating that an interference state exists and starts measuring the duration, and when the duration exceeds a certain period of time, it outputs an alarm indicating that the degree of danger is high, thereby having the effect of reporting the degree of danger in real time and alerting air traffic controllers, etc.

The present invention is suitable for wireless devices that can quickly and accurately detect the presence or absence of interference in air traffic control, and can further increase safety by reporting the level of danger according to the level of interference.

1...antenna, 2...GPS antenna, 3...high frequency unit, 4...receiving device, 5...network device, 6...personal computer, 7...external storage device, 11...ADC, 12...frequency conversion unit, 13...first rate conversion unit, 14...second rate conversion unit, 15...window processing unit, 16...third rate conversion unit, 17...FFT unit, 18...interference detection unit, 19...power detection unit, 21...demodulation unit, 22...DAC

Claims (7)

A wireless device that detects interference that occurs on a receiving side when multiple wireless devices simultaneously transmit radio waves at the same frequency in one wireless communication area,
a windowing unit that performs windowing on the received signal to optimize the results of subsequent Fast Fourier Transform (FFT) processing;
a rate conversion unit that performs rate conversion on the signal output from the window processing unit to a higher frequency, extracts FFT frames including a specific number of samples by shifting the frames by a certain number of samples and overlapping the frames, and sequentially outputs the FFT frames at a time corresponding to the certain number of samples ;
an FFT unit that performs a fast Fourier transform on the signal of each FFT frame output from the rate conversion unit to obtain a relationship between a frequency and a level of the signal of the FFT frame ;
and an interference detection unit that detects peak power in a band including the carrier frequency output from the FFT unit, and determines an interference state every certain number of samples based on the number of detected peaks to detect interference. The wireless device according to claim 1, which has an interface unit that acquires time information using the NTP protocol or GPS. The wireless device according to claim 1, to which a storage device is connected that stores data on the interference state when interference is detected by the interference detection unit. The wireless device according to claim 3, which is connected to a computer device that reads and displays data on the interference state from the storage device. 5. The wireless device according to claim 4, wherein when the computer device receives data indicating an interference state, the computer device displays a warning indicating that the danger is small and starts timing, and if the interference state continues for longer than a specific time, the computer device displays an alarm indicating that the danger is large. The wireless device of claim 1, which increases the number of samples per frame in FFT processing and also increases the number of overlaps. The wireless device according to claim 1, which is provided with a window processing unit, an FFT unit, and an interference detection unit for each of a plurality of frequencies corresponding to a plurality of wireless communication areas.

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