Probe

Abstract

To provide a detector that improves the detection accuracy of radar waves from speed measuring devices. [Solution] The detector 1 comprises a receiving unit 21 including an antenna, a receiving detection unit 22, and a refining unit 51. The receiving detection unit 22 generates an intermediate frequency signal while sweeping a predetermined frequency range fb to the termination frequency fe, and detects radio wave reception based on the intermediate frequency signal. The refining unit 51 fixes the frequency of the radio wave detected by the receiving detection unit 22, and determines that it is the reception of a radar wave from a speed measuring device if radio wave reception is detected continuously for a predetermined time. The radio wave detected during the sweep is a undulation signal Sw generated by low-frequency noise SL superimposed when radio waves are received while sweeping. The refining unit 51 identifies the frequency of the radio wave when low-frequency noise SL is not superimposed from the undulation signal Sw, and detects the continuation of radio wave reception by fixing it to the identified frequency.

Description

[[Technical Field]]

[0001] The present invention relates to a detector capable of receiving radar waves irradiated by a speed measuring device. [[Background Art]]

[0002] When a vehicle approaches a speed measuring device, or when the detector receives a radar wave that is a radio wave irradiated by the speed measuring device, the detector notifies information that directly or indirectly prompts compliance with speed limits. This detector notifies the information by receiving the radar wave irradiated by the speed measuring device via an antenna. Additionally, the detector detects that the position of the own vehicle specified by GPS has approached a predetermined distance from a pre-registered position of a speed measuring device, and notifies the aforementioned information.

[0003] This detector is capable of detecting X-band microwaves, K-band microwaves, and the like. For example, the detector comprises a first local oscillator and a first mixer. The first local oscillator generates a first frequency signal, and the first mixer mixes the received signal with the first frequency signal to generate a first intermediate frequency signal. Then, the detector comprises a detection unit that detects the radar wave from the speed measuring device from the first intermediate frequency signal.

[0004] In recent years, detectors have been equipped with double superheterodyne reception circuits (see, for example, Patent Document 1 and Patent Document 2). A detector of the double superheterodyne type further comprises a second local oscillator, a sweep control unit, and a second mixer for image suppression. The second local oscillator is a voltage-controlled oscillator (VCO) that generates a second frequency signal corresponding to the voltage input from the sweep control unit. The sweep control unit sweeps the voltage input to the second local oscillator, thereby causing the second frequency signal output from the second local oscillator to be repeatedly swept within a predetermined frequency range. The second mixer mixes the second frequency signal with the first intermediate frequency signal to generate a second intermediate frequency signal. The detection unit performs detection using this second intermediate frequency signal.

[0005] However, double superheterodyne detectors receive radio waves in the same frequency band emitted by devices other than speed measuring devices. These detectors may mistakenly identify these waves as signals from the speed measuring device. Therefore, the detector scrutinizes the received radio waves to suppress misidentification of signals emitted by devices other than speed measuring devices. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2017-96728 [Patent Document 2] Japanese Patent Publication No. 2022-139870 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] If radio wave reception is detected during a sweep by the second local oscillator, the sweep is temporarily paused. The second local oscillator then fixes the frequency of the second frequency signal for a certain period of time. During the sweep stop period when the frequency is fixed, a refinement process is performed on the radio waves to suppress misidentification. In this refinement process, for example, the continuity of the received signal is determined. A received signal that continues for a certain period of time or longer is determined to be a signal originating from the radar wave of the speed measuring device and is subject to information broadcasting. If the duration of the received signal is less than a certain period of time, the sweep stop is released and the sweep resumes from the fixed frequency.

[0008] In determining continuity, the second local oscillator fixes the frequency at the peak position of the radio wave. However, as a result of our diligent research, we have confirmed that there may be discrepancies between the frequency at which a peak appears during the sweep and the frequency of the radio wave actually emitted by the device. In other words, the frequency at which a peak appears during the sweep is different from the frequency of the radio wave actually emitted by the device.

[0009] If the continuity is judged by fixing the frequency to one that deviates from the original frequency, there is a risk that the received signal will not continue beyond a certain point, even if it originates from the radar waves of a speed measuring device. Alternatively, if the continuity is judged by fixing the frequency to one that deviates from the original frequency, there is a risk that the received signal will continue beyond a certain point, even if it originates from a device of a different type than the speed measuring device. As a result, the timing of information notification by the detector may be delayed, or the detector may misidentify the device, leading to a decrease in the accuracy of the detector.

[0010] The present invention was proposed to solve the above-mentioned problems, and its objective is to provide a detector that improves the detection accuracy of radar waves from a speed measuring device. [Means for solving the problem]

[0011] To achieve the above objective, the detector is installed in a vehicle and detects radar waves from a speed measuring device, and comprises a receiving unit including an antenna, a receiving detection unit that generates an intermediate frequency signal while sweeping a predetermined frequency range to a terminal frequency and detects radio wave reception based on the intermediate frequency signal, and a refining unit that fixes the frequency of the radio wave detected by the receiving detection unit and determines that it is the reception of radar waves from the speed measuring device when radio wave reception is detected continuously for a predetermined time, wherein the radio wave detected during the sweep is a undulation signal generated by low-frequency noise superimposed when radio waves are received while sweeping, and the refining unit identifies the frequency of the radio wave in a state where the low-frequency noise is not superimposed from the undulation signal, fixes it to the identified frequency and detects the continuation of radio wave reception.

[0012] The aforementioned analysis unit may identify the zero signal level included in the undulation signal, excluding the white noise range, and fix it at a frequency shifted by a pre-stored offset value from that zero signal level.

[0013] The fixed frequency may be the frequency at which the radio wave intensity peaks when the radio wave is received.

[0014] The system may also be equipped with a notification unit that notifies information when it is determined that the radar wave of the speed measuring device has been received.

[0015] The notification unit may also notify information when it determines a predetermined number of times that the radar waves of the speed measuring device have been received during a series of sweeps.

[0016] The receiving unit receives radio waves and converts them into a received signal, and the receiving detection unit may include: a plurality of local oscillators, each outputting a signal of a predetermined frequency; a first-stage mixing unit, which mixes the received signal with a signal of the frequency output by the first-stage local oscillator to output a first-stage intermediate frequency signal; a second or subsequent stage mixing unit, which mixes a signal of the frequency output by the same-stage local oscillator with the previous stage intermediate frequency signal to output a next-stage intermediate frequency signal; and a sweep control unit, which sweeps the frequency of the signal output by any of the second or subsequent local oscillators up to the termination frequency of a predetermined frequency band.

[0017] The receiving unit receives radio waves and converts them into a received signal, and the receiving detection unit may include: two local oscillator units, each outputting a signal of a predetermined frequency; a first-stage mixing unit, which mixes the received signal with the signal of the frequency output by the first-stage local oscillator unit to output a first-stage intermediate frequency signal; a second-stage mixing unit, which mixes the signal of the frequency output by the second-stage local oscillator unit with the first-stage intermediate frequency signal to output a next-stage intermediate frequency signal; and a sweep control unit, which sweeps the frequency of the signal output by the second-stage local oscillator unit up to the termination frequency of a predetermined frequency band.

[0018] The inspection unit may determine that the reception of a radio wave from the speed measuring device is a radar wave from the speed measuring device if it detects the reception of a radio wave of a fixed frequency for a predetermined period of time, the frequency of the radio wave detected by the reception detection unit is within a specific range, and the radio wave detected by the reception detection unit is an unmodulated wave.

[0019] The detailed examination unit continuously detects reception of a radio wave of a fixed frequency for a predetermined period of time, determines whether the frequency of the radio wave detected by the reception detection unit is within a specific range, and determines whether the radio wave detected by the reception detection unit is an unmodulated wave; and when the result of the detailed examination unit shows that reception of a radio wave is continuously detected for a predetermined period of time but the frequency of the radio wave detected by the reception detection unit is not within the specific range, if the radio wave detected by the reception detection unit is an unmodulated wave, the notification unit may be configured to determine radio wave detection information that is not specified as reception of a radar wave from said speed measurement device.

[0020] The detailed examination unit continuously detects reception of a radio wave of a fixed frequency for a predetermined period of time, determines whether the frequency of the radio wave detected by the reception detection unit is within a specific range, and determines whether the radio wave detected by the reception detection unit is an unmodulated wave; and when the result of the detailed examination unit shows that reception of a radio wave is continuously detected for a predetermined period of time but the frequency of the radio wave detected by the reception detection unit is not within the specific range, if the radio wave detected by the reception detection unit is not an unmodulated wave, the notification unit may be configured to notify information indicating that a radar wave from said speed measurement device has been received.

[0021] The detailed examination unit continuously detects reception of a radio wave of a fixed frequency for a predetermined period of time, determines whether the frequency of the radio wave detected by the reception detection unit is within a specific range, and determines whether the radio wave detected by the reception detection unit is an unmodulated wave; and when the result of the detailed examination unit shows that reception of a radio wave is continuously detected for a predetermined period of time, the notification unit may be configured to specify the type of the speed measurement device and notify information indicating that a radar wave from the speed measurement device has been received, in accordance with whether the frequency of the radio wave detected by the reception detection unit is within the specific range and whether the radio wave detected by the reception detection unit is an unmodulated wave. Effects of the Invention

[0022] According to the present invention, continuity can be examined while the frequency is fixed to a correct frequency, and the detection accuracy of the detector is improved. Brief Description of the Drawings

[0023] [Figure 1] It is a perspective view showing a face of the detector facing outside a vehicle. [Figure 2] It is a perspective view showing a surface of the detector facing the vehicle interior. [Figure 3] It is a block diagram showing the internal configuration of the detector. [Figure 4] It is a block diagram showing the configuration of a radio wave reception system according to the first embodiment. [Figure 5] It is a block diagram showing the configuration of a control unit according to the first embodiment. [Figure 6] It is a flowchart showing an operation example of the detector according to the first embodiment. [Figure 7] It is a schematic diagram showing the sweep operation in the radio wave reception mode of the detector according to the first embodiment. [Figure 8] It is a schematic diagram showing a storage operation of received information during sweeping in the radio wave reception mode of the detector according to the first embodiment. [Figure 9] It is a schematic diagram showing details of a demodulated signal output from a detection unit. [Figure 10] It is a flowchart showing an undulation correction operation. [Figure 11] It is a schematic diagram showing the correspondence between an undulation signal Sw and a demodulated signal. [Figure 12] It is a schematic diagram showing a waveform generated in a correlation filter, in which the signal zero level of the demodulated signal is replaced with a peak. [Figure 13] It is a schematic diagram showing the positional relationship between the signal zero level and the peak of a demodulated signal having an S-curve characteristic and a demodulated signal having an N-curve characteristic. [Figure 14] It is a schematic diagram showing a state of selection of received information in a close inspection mode according to the first embodiment. [Figure 15] It is a schematic diagram showing a close inspection operation of the detector according to the first embodiment. [Figure 16] It is a block diagram showing the configuration of a control unit according to a modified example of the first embodiment. [Figure 17] It is a flowchart showing a detection operation of a detector according to a modified example of the first embodiment. [Figure 18] It is a schematic diagram showing a detection operation of a detector according to a modified example of the first embodiment. [Figure 19] This is a flowchart showing an example of the operation of the detector according to the second embodiment. [Figure 20] This flowchart shows an example of the operation of the detector according to Modification 1 of the second embodiment. [Figure 21] This flowchart shows an example of the operation of the detector according to a modified example 2 of the second embodiment. [Modes for carrying out the invention]

[0024] (First Embodiment) (composition) A detector according to the first embodiment of the present invention will be described in detail with reference to the drawings. Figure 1 is a perspective view showing the side of the detector 1 facing out of the vehicle, and Figure 2 is a perspective view showing the side of the detector 1 facing inward into the vehicle.

[0025] Detector 1 is installed in vehicles such as automobiles, motorcycles, trucks, and buses. Detector 1 directly or indirectly provides information encouraging speed compliance in response to events that should prompt speed adherence. Detector 1 is typically installed on the dashboard and powered from the vehicle via an OBD-II connector or cigarette lighter socket. The dashboard is an example of a location where radar waves emitted by speed measuring devices can be easily received and information can be provided to the driver.

[0026] Speed ​​measuring devices include fixed and mobile devices that emit radar waves. Events that prompt speed compliance include when a vehicle reaches a predetermined distance from a speed measuring device whose location is known, and when the vehicle receives radar waves emitted by the speed measuring device. The radar waves are, for example, K-band frequencies in the 24GHz band and are modulated microwaves such as frequency-modulated microwaves. The information that the detector 1 reports may include, for example, the presence of a speed measuring device, the type of speed measuring device, the reception and type of radar waves emitted by the speed measuring device, or a warning to comply with the speed limit, or a combination of these.

[0027] As shown in Figures 1 and 2, the detector 1 is equipped with a screen 14, a speaker 15, and a lamp 16 on the outer surface of the housing 10. The screen 14 is a liquid crystal display or an organic EL display, etc., and is located on the front 12 of the detector 1, displaying notification information in a visually appealing format such as characters, pictures, and symbols. The speaker 15 outputs the notification information as sound. The lamp 16 indicates the notification information through regular illumination such as color, flashing, and lighting intervals. The front 12 faces inward and is visible to the driver, while the rear 11 faces outward through the windshield.

[0028] The rear surface 11 of the detector 1 is a reception area 13. The radio wave receiving system 2 and the positioning signal receiving system 3 are housed inside the housing 10 on the rear surface 11. The radio wave receiving system 2 has a double superheterodyne receiving circuit and receives and detects radar waves emitted by the speed measuring device. The positioning signal receiving system 3 has an antenna, demodulator, and processor capable of receiving radio signals from positioning satellites, and receives and demodulates GNSS (Global Navigation Satellite System) positioning signals to calculate the vehicle's position, which consists of the latitude and longitude of the current location.

[0029] Figure 3 is a block diagram showing the internal configuration of the detector 1. As shown in Figure 3, the detector 1 further comprises a control unit 5 and a notification unit 6. The radio wave receiving system 2 and the positioning signal receiving system 3 input and output signals to the control unit 5. This control unit 5 is a so-called computer that includes a processor such as a CPU, DSP, GPU, FPGA, or microcontroller, storage for storing programs and data, and work memory.

[0030] The control unit 5 controls the radio wave receiving system 2 and determines whether radar waves from the speed measuring device have been received. The control unit 5 also determines the distance between the vehicle's position, output by the positioning signal receiving system 3, and speed measuring devices whose installation locations are known, as well as locations where speed measuring devices have been installed in the past (hereinafter collectively referred to as registered speed measuring devices). The control unit 5 then causes the notification unit 6 to notify information according to the determination result. The notification unit 6 consists of a screen 14, a speaker 15, a lamp 16, or a combination thereof, located on the outer surface of the housing 10.

[0031] Figure 4 is a block diagram showing the detailed configuration of the radio wave receiving system 2 of the detector 1. The radio wave receiving system 2 comprises a receiving unit 21 and a receiving detection unit 22. The receiving unit 21 includes an antenna that receives at least the K-band frequency range and outputs a received signal RF, a bandpass filter that removes unwanted frequency components from the received signal RF, and a low-noise amplifier that amplifies the received signal RF. This receiving unit 21 may be separated from the detector 1 and mounted in a separate enclosure in the vehicle.

[0032] The reception detection unit 22 generates an intermediate frequency signal by sweeping the frequency of the local oscillator signal that is mixed with the received RF signal, and detects radio wave reception based on the intermediate frequency signal. This reception detection unit 22 includes a first-stage local oscillator unit 23, a first-stage mixing unit 24, a second-stage local oscillator unit 25, a second-stage mixing unit 26, a sweep control unit 27, and a detection unit 28.

[0033] The first stage mixing unit 24 and the second stage mixing unit 26 are active mixers that perform frequency conversion using transistors as a base, for example. The first stage mixing unit 24 converts the received signal RF input from the receiving unit 21 into the first stage intermediate frequency signal IFf. The second stage mixing unit 26 converts the first stage intermediate frequency signal IFf input from the first stage mixing unit 24 into the second stage intermediate frequency signal IFs.

[0034] The first stage mixer 24 receives the first stage local oscillator signal LFf from the first stage local oscillator 23. The first stage mixer 24 outputs the first stage intermediate frequency signal IFf as a result of the difference between the frequency of the received signal RF and the first stage local oscillator signal LFf. The second stage mixer 26 receives the second stage local oscillator signal LFs from the second stage local oscillator 25. The second stage mixer 26 outputs the second stage intermediate frequency signal IFs as a result of the difference between the frequency of the first stage intermediate frequency signal IFf and the second stage local oscillator signal LFs.

[0035] Furthermore, the first stage mixing unit 24 may be equipped with a low-pass filter and an amplifier in the subsequent stage. Alternatively, a low-noise amplifier that amplifies the received signal RF may be provided instead of the receiving unit. This first stage mixing unit 24 cuts out the received signal RF, the first stage local oscillator signal LFf, and the signal resulting from the sum of the frequencies of the received signal RF and the first stage local oscillator signal LFf from the mixing result. The first stage mixing unit 24 then amplifies and outputs only the first stage intermediate frequency signal IFf.

[0036] Furthermore, the second stage mixing unit 26 may also include a low-pass filter and an amplifier in the subsequent stage. This second stage mixing unit 26 cuts out the intermediate frequency signal IFf from the first stage, the local oscillator signal LFs from the second stage, and the signal resulting from the sum of the frequencies of the intermediate frequency signal IFf from the first stage and the local oscillator signal LFs from the second stage from the mixing result. The second stage mixing unit 26 then amplifies and outputs only the intermediate frequency signal IFs from the second stage.

[0037] The first-stage local oscillator signal LFf has a predetermined, fixed frequency. On the other hand, the frequency of the second-stage local oscillator signal LFs varies depending on the mode. In radio wave reception mode, the frequency of the second-stage local oscillator signal LFs changes by sweeping a predetermined frequency range fb from the start frequency fs at one end to the end frequency fe at the other end. In refinement mode, the frequency of the second-stage local oscillator signal LFs is fixed to one of the frequencies within the predetermined frequency range fb.

[0038] This second-stage local oscillator 25 is, for example, a voltage-controlled oscillator (VCO). This second-stage local oscillator 25 generates a second-stage local oscillator signal LFs in response to the sweep voltage signal SV input from the sweep control unit 27. The sweep control unit 27 inputs the sweep voltage signal SV to the second-stage local oscillator 25 so that the second-stage local oscillator signal LFs sweeps a predetermined frequency range fb from the start frequency fs at one end to the end frequency fe at the other end.

[0039] In other words, the sweep control unit 27 continuously changes the sweep voltage signal SV from, for example, a starting sweep voltage signal SVs of 0V corresponding to the starting frequency fs of a predetermined frequency range fb, to, for example, a ending sweep voltage signal SVe of 3.3V corresponding to the ending frequency fe of a predetermined frequency range fb.

[0040] This sweep control unit 27 is controlled by the control unit 5 of the detector 1. When the sweep is completed up to the termination frequency fe, the sweep control unit 27 inputs a sweep completion notification signal Ce to the control unit 5. The sweep control unit 27 receives a sweep start control signal Cs from the control unit 5 and starts controlling the sweep. When the control unit 5 inputs a specific frequency continuation control signal Cc indicating a specific frequency, the sweep control unit 27 continues to input a constant voltage signal CV to the second stage local oscillator unit 25 in order to continue the second stage local oscillator signal LFs indicated by the specific frequency continuation control signal Cc from the control unit 5.

[0041] Furthermore, the method for specifying a specific frequency using the specific frequency continuation control signal Cc may be any of the following: information indicating the frequency of the received radio wave, information indicating the second-stage local oscillator signal LFs, or information indicating the constant voltage signal CV output by the sweep control unit 27. If the specific frequency continuation control signal Cc includes information indicating the frequency of the received radio wave or information indicating the second-stage local oscillator signal LFs, the sweep control unit 27 calculates the constant voltage signal CV.

[0042] The detection unit 28 amplifies and detects the second-stage intermediate frequency signal IFs, and outputs a detection signal Sc expressed as a voltage. The detection signal Sc from the detection unit 28 is AD converted and input to the control unit 5. If no radio waves in the K-band frequency range are received, the detection signal Sc is white noise Sn. On the other hand, if a radio wave of a predetermined frequency within the K-band frequency range is received, the detection signal Sc is a demodulated signal Sd with a voltage level above a certain level. In other words, the demodulated signal Sd is a waveform with a voltage level higher than the white noise Sn.

[0043] Figure 5 is a block diagram showing the detailed configuration of the control unit 5 of the detector 1. The control unit 5 comprises a detailing unit 51 and a notification control unit 52. The detailing unit 51 determines whether a predetermined number of radio waves detected by the reception detection unit 22 while it is sweeping are radar waves from a speed measuring device, in order of decreasing radio wave intensity level Ds.

[0044] This inspection unit 51 includes a reception determination unit 53, a reception information storage unit 54, an inspection target selection unit 55, and an inspection determination unit 56. The inspection determination unit 56 also includes a tuning control unit 57 and a signal monitoring unit 58.

[0045] The reception determination unit 53 detects the demodulated K-band signal Sd from the detected signal Sc detected by the detection unit 28 of the reception detection unit 22. The reception determination unit 53 has a threshold value higher than the white noise Sn stored in its memory. The reception determination unit 53 compares the detected signal Sc with the threshold value. If the detected signal Sc exceeds the threshold value, the detected signal Sc is the demodulated signal Sd.

[0046] When the reception information storage unit 54 detects the demodulated signal Sd from the reception determination unit 53, it generates and stores reception information Dr. Reception information Dr is added to and stored each time the demodulated signal Sd is detected during a sweep. The group of reception information Dr added during a sweep is initialized during the next sweep. Reception information Dr includes frequency information Df and signal strength level Ds as a set. Frequency information Df directly or indirectly identifies the frequency of the received radio wave. Signal strength level Ds identifies the strength of the received radio wave by classifying it into levels.

[0047] The frequency information Df is, in principle, the frequency of the received radio wave when the demodulated signal Sd is generated. However, the detection signal Sc during the sweep is superimposed with noise of a magnitude corresponding to the strength of the radio wave. This noise is low frequency, causing the detection signal Sc to undulate. Due to this undulation, the frequency at which the peak of the demodulated signal Sd appears deviates from the frequency at which the peak of the demodulated signal Sd appears when the frequency is fixed without sweeping. Therefore, the received information storage unit 54 corrects the content of the frequency information Df obtained from the undulating detection signal Sc to the frequency of the peak that is estimated to appear in the detection signal Sc when there is no undulation.

[0048] The radio wave strength level Ds may be obtained by dividing the RSSI value (Received Signal Strength Indicator) into multiple levels. Alternatively, the radio wave strength level Ds may be obtained by dividing the peak-to-peak value of the demodulated signal Sd into multiple levels. Alternatively, the radio wave strength level Ds may be obtained by dividing the difference from the peak to the zero point of the demodulated signal Sd into multiple levels. The RSSI value may be obtained from the received signal strength indicator of the detection unit 28.

[0049] The refinement target selection unit 55 selects the radio waves to be refined. This refinement target selection unit 55 begins selection after receiving a sweep completion notification signal Ce from the sweep control unit 27, which indicates the end of the sweep. The refinement targets are selected from the received information Dr. The refinement target selection unit 55 picks up a predetermined number of received information Dr in descending order of radio wave intensity level Ds. Here, there is a characteristic that the demodulated signal Sd appears twice for one radio wave reception. Therefore, the predetermined number is preferably at least four or more, but the fewest possible number is advantageous, and most preferably four.

[0050] The refinement and determination unit 56 performs a refinement to determine whether the reception is of radar waves from the speed measuring device, by referring to the reception information Dr selected by the refinement target selection unit 55. Of the refinement and determination unit 56, the tuning control unit 57 inputs a specific frequency continuation control signal Cc to the sweep control unit 27. The specific frequency continuation control signal Cc directly or indirectly identifies the frequency of the radio wave to be received and instructs the continuation of reception of radio waves at this frequency. The frequency of the radio wave to be received is identified by the frequency information Df included in the reception information Dr. That is, the tuning control unit 57 generates the specific frequency continuation control signal Cc by referring to the frequency information Df included in the reception information Dr.

[0051] The sweep control unit 27 continuously inputs a constant voltage signal CV corresponding to the specific frequency continuation control signal Cc to the second stage local oscillator unit 25. The second stage local oscillator unit 25 continuously inputs the second stage local oscillator signal LFs, which is specified by the frequency information Df, to the second stage mixer unit 26. Therefore, the specific frequency continuation control signal Cc can be any of the following: the frequency of the received radio wave when the demodulated signal Sd is generated, the frequency of the second stage local oscillator signal LFs when this radio wave is received, or the sweep voltage signal SV that causes this second stage local oscillator signal LFs to be output.

[0052] Of the inspection and determination units 56, the signal monitoring unit 58 monitors the continuation of radio wave reception while continuously outputting a constant second-stage local oscillator signal LFs. That is, the signal monitoring unit 58 monitors the continuation of the demodulated signal Sd input by the detection unit 28. The predetermined time is, for example, 30 ms, according to the duration of the radio waves emitted by the speed measuring device. In other words, if the monitoring results show that the continuation of radio wave reception has reached the predetermined time, the received radio wave is the radio wave emitted by the speed measuring device.

[0053] The signal monitoring unit 58 stores a threshold value set to be less than the intensity of the demodulated signal Sd. The signal monitoring unit 58 also stores a predetermined time in advance. The signal monitoring unit 58 continuously compares the intensity of the demodulated signal Sd with the threshold value while timing the duration of the demodulated signal Sd. If the intensity of the demodulated signal Sd continues to exceed the threshold value until the predetermined duration is reached, the signal monitoring unit 58 determines that it is receiving radio waves emitted by the speed measuring device. When the notification control unit 52 determines that the signal monitoring unit 58 is receiving radar waves from the speed measuring device, it outputs information to the notification unit 6 to provide notification.

[0054] If the intensity of the demodulated signal Sd falls below a threshold, the refinement determination unit 56 performs a refinement using the remaining received information Dr selected by the refinement target selection unit 55. If it is not determined that all of the received information Dr selected by the refinement target selection unit 55 are radio waves emitted by the speed measuring device, the tuning control unit 57 inputs a sweep start control signal Cs to the sweep control unit 27 in order to start the next sweep.

[0055] Figure 6 is a flowchart illustrating an example of operation by the control unit 5. As shown in Figure 6, first the received information storage unit 54 initializes the received information Dr (step S101). Next, the tuning control unit 57 starts the sweep (step S102). In step S102, for example, the tuning control unit 57 inputs a sweep start control signal Cs to the sweep control unit 27.

[0056] When the sweep control unit 27 receives the sweep start control signal Cs, it sets the sweep voltage signal SV to the starting sweep voltage signal SVs and inputs it to the second stage local oscillator unit 25. The sweep control unit 27 inputs the sweep voltage signal SV while continuously and nonstop changing it from the starting sweep voltage signal SVs to the ending sweep voltage signal SVe. The second stage local oscillator unit 25 inputs the second stage local oscillator signal LFs to the second mixer 26 while continuously and nonstop changing it from the starting frequency fs corresponding to the starting sweep voltage signal SVs to the ending frequency fe corresponding to the ending sweep voltage signal SVe.

[0057] The received signal RF received by the receiving unit 21 is converted into the first-stage intermediate frequency signal IFf by the first-stage mixing unit 24. The first-stage intermediate frequency signal IFf is input to the second-stage mixing unit 26 and converted into the second-stage intermediate frequency signal IFs according to a sweep of a predetermined frequency range fb. The detection unit 28 detects the second-stage intermediate frequency signal IFs and inputs the detected signal Sc to the control unit 5.

[0058] When the detected signal Sc is input, the reception determination unit 53 analyzes the detected signal Sc to determine whether it corresponds to the reception of radio waves (step S103). In step S103, for example, the reception determination unit 53 determines whether the detected signal Sc contains a demodulated signal Sd. The reception determination unit 53 detects the demodulated signal Sd by comparing the detected signal Sc with a threshold. If it corresponds to radio wave reception (step S103, Yes), the reception information storage unit 54 stores the reception information Dr (step S104) and corrects the frequency information Df to the frequency of the detected signal Sc without fluctuations (step S105).

[0059] If the sweep is in progress within the predetermined frequency range fb (step S106, No), the sweep is not stopped, and the reception determination unit 53 repeatedly determines whether radio waves have been received and adds reception information Dr if radio waves have been received (steps S103-106). When the sweep is completed up to the termination frequency fe of the predetermined frequency range fb (step S106, Yes), the refinement determination unit 56 switches to refinement mode (steps S107-). For example, a sweep completion notification signal Ce is input to the control unit 5 from the sweep control unit 27. This sweep completion notification signal Ce triggers the refinement determination unit 56 to switch to refinement mode.

[0060] When one sweep is completed up to the termination frequency fe of the predetermined frequency range fb (step S106, Yes), the selection unit 55 selects a predetermined number of received information Drs from the group of received information Drs collected in one sweep, in descending order of radio wave intensity level Ds (step S107).

[0061] The tuning control unit 57 switches the received information Dr from the selected group of received information Dr in the order in which radio waves were received during the sweep, and fixes the frequency of the received radio wave in the frequency information Df included in the received information Dr (step S108). That is, the tuning control unit 57 inputs a specific frequency continuation control signal Cc to the sweep control unit 27, for example, which instructs the continuous output of a constant voltage signal CV corresponding to the frequency information Df.

[0062] While the frequency is fixed to this frequency information Df, the signal monitoring unit 58 monitors whether the demodulated signal Sd continues for a predetermined time (step S109). For example, the signal monitoring unit 58 compares the demodulated signal Sd input from the detection unit 28 with a threshold and continues to determine whether the demodulated signal Sd continues to exceed the threshold for a predetermined time.

[0063] If the demodulated signal Sd does not continue for a predetermined time (step S109, No), and if there are any unchecked received information Drs among the received information Drs selected by the inspection target selection unit 55 (step S110, Yes), the frequency is fixed to that of the remaining received information Drs (step S108). The signal monitoring unit 58 then monitors whether the demodulated signal Sd continues for a predetermined time (step S109). If none of the demodulated signals Sd continue for the predetermined time and the inspection of all received information Drs is completed (step S110, No), the process returns to step S101, the received information Drs are initialized, and the sweep for the next cycle is started (steps S102~).

[0064] On the other hand, if the demodulated signal Sd continues for a predetermined time or longer (step S109, Yes), the notification control unit 52 causes the notification unit 6 to notify (step S111). That is, the detector 1, after careful examination, determines that it has received radar waves emitted by the speed measuring device and notifies the information. Then, returning to step S101, the received information Dr is initialized and the sweep for the next cycle is started (steps S102~).

[0065] Figure 7 is a schematic diagram showing the sweep operation of the radio wave reception mode of this detector 1. As shown in Figure 7(a), in the radio wave reception mode, the tuning control unit 57 inputs the sweep voltage signal SV to the second stage local oscillator unit 25 while sweeping from the start sweep voltage signal SVs to the end sweep voltage signal SVe without sweep stopping.

[0066] As shown in Figure 7(b), the second-stage local oscillator 25, which receives the sweep voltage signal SV, inputs the frequency of the second-stage local oscillator signal LFs to the second-stage mixer 26 in the radio wave reception mode, sweeping a predetermined frequency range fb from the start frequency fs to the end frequency fe without sweeping.

[0067] As shown in Figure 7(c), the detected signal Sc becomes white noise Sn near zero when no radio waves are received. When radio waves are received, the detected signal Sc has a peak with a larger absolute value than the white noise Sn.

[0068] Figure 8 is a schematic diagram showing the memory operation of reception information Dr during sweep in the radio wave reception mode of the detector 1. As shown in Figure 8, during sweep in radio wave reception mode, the reception determination unit 53 determines whether a demodulated signal Sd is being received by using a threshold value. Even if it is a demodulated signal Sd, the sweep is not stopped, and the reception information storage unit 54 combines the frequency information Df that identifies the frequency of the demodulated signal Sd and the radio wave intensity level Ds of the demodulated signal Sd into a single reception information Dr. The reception information storage unit 54 then stores the reception information Dr each time it obtains a demodulated signal Sd during a single sweep.

[0069] For example, as shown in Figure 8, during one sweep, the demodulated signal Sd1 to demodulated signal Sd7 are detected seven times. The sweep voltage signal SV when demodulated signal Sd1 is detected is acquired as frequency information Df1. In addition, the peak value of demodulated signal Sd1 is acquired as the signal strength level Ds1.

[0070] The sweep voltage signal SV obtained when the demodulated signal Sd2 is detected is acquired as frequency information Df2. The peak value of the demodulated signal Sd2 is also acquired as the signal strength level Ds2. The sweep voltage signal SV obtained when the demodulated signal Sd3 is detected is acquired as frequency information Df3. The peak value of the demodulated signal Sd3 is also acquired as the signal strength level Ds3. In this way, the sweep voltage signals SV obtained when the demodulated signals Sd1 to Sd7 are detected are acquired as frequency information Df1 to Df7. The peak values ​​of the demodulated signals Sd1 to Sd7 are also acquired as signal strength levels Ds1 to Ds7.

[0071] Figure 9 is a schematic diagram showing the details of the demodulated signal Sd output by the detection unit 28. During sweeping in radio wave reception mode, low-frequency noise SL, whose magnitude corresponds to the strength of the radio wave, is superimposed on the detected signal Sc. Therefore, a swirling signal Sw, in which low-frequency noise SL is superimposed on the detected signal Sc during sweeping, may appear prominently. The frequency at which the peak of the swirling signal Sw appears may differ from the frequency at which the peak of the demodulated signal Sd obtained by fixing the frequency without sweeping appears.

[0072] Therefore, when frequency information Df is obtained from this undulation signal Sw to be included in the received information Dr, there may be cases where the frequency is fixed to a frequency outside the peak and the system monitors whether the demodulated signal Sd continues for a predetermined time. In this case, because the frequency is fixed to a frequency outside the peak, there is a risk that the demodulated signal Sd will fall below the threshold of the signal monitoring unit 58 without continuing for the predetermined time. In this case, the notification accuracy can be further improved.

[0073] Alternatively, in this case, because the frequency is fixed outside the peak range, signals from other devices not originating from the speed measuring device may persist for a predetermined period of time. In this case, the accuracy of false alarm suppression can be further improved.

[0074] In other words, the received information storage unit 54 corrects the undulation signal Sw to a detection signal Sc without undulation before acquiring the frequency information Df. Figure 10 is a flowchart showing the undulation correction operation by the received information storage unit 54, and details the operation of step S104 in Figure 6.

[0075] First, Figure 11 is a first schematic diagram showing the correspondence between the undulation signal Sw and the demodulated signal Sd. As shown in Figure 11, the undulation signal Sw, regardless of the low-frequency noise SL, and excluding the white noise range, has the same zero-level signal Z position in the demodulated signal Sd as the detected signal Sc. Therefore, the received information storage unit 54 identifies the zero-level signal position using a correlation filter.

[0076] Specifically, as shown in Figure 10, the receiving information storage unit 54 obtains a predetermined number of voltage values ​​before and after the voltage value to be converted into a filter output value from the undulation signal Sw (step S201). Next, the receiving information storage unit 54 calculates the average value of the predetermined number of voltage values ​​before and after the voltage value to be converted, including the voltage value to be converted, using a pre-installed correlation filter (step S202). The correlation filter has an adder, and the receiving information storage unit 54 then uses the correlation filter to calculate an adder value obtained by subtracting the average value from each voltage value that was the basis for calculating the average value (step S203). Then, the receiving information storage unit 54 uses the correlation filter to add up the sum of the values ​​obtained by multiplying the adder values ​​before the adder value to the voltage value to be converted by a negative coefficient, and the sum of the values ​​obtained by multiplying the adder value after the adder value to the voltage value to be converted by a positive coefficient, and calculates a filter output value corresponding to the voltage value to be converted (step S204).

[0077] The received information storage unit 54 applies the filter output value to the voltage value to be converted using a correlation filter (step S205). As a result, as shown in Figure 12, the correlation filter generates a replaced waveform Se in which the zero-level signal Z of the demodulated signal Sd is replaced by a peak. The received information storage unit 54 searches for the absolute peak among the filter output values ​​after this correlation filter has been applied (step S206). When the position of this peak is positive, it is the position of the zero-level signal Z in the demodulated signal Sd with an S-shaped curve characteristic, and when it is negative, it is the position of the zero-level signal Z in the demodulated signal Sd with an N-shaped curve characteristic.

[0078] Figure 13 is a schematic diagram showing the positional relationship between the zero level and the peak of a demodulated signal Sd with an S-curve characteristic and a demodulated signal Sd with an N-curve characteristic. As shown in Figure 13, if the sweep is not stopped, the demodulated signal Sd exhibits a waveform in which the minimum and maximum values ​​of the output voltage appear around the center frequency, due to the S-curve and N-curve characteristics that appear in the relationship between frequency and voltage. The S-curve characteristic shows an S-shaped waveform that drops below zero, passes through a minimum, and then rises towards the maximum value which is the peak. The N-curve characteristic shows an N-shaped waveform that rises towards the maximum value which is the peak, then drops below zero and reaches a minimum.

[0079] In a demodulated signal Sd with an S-shaped curve characteristic, the peak, which is the maximum value of the demodulated signal Sd, appears at a frequency higher than the zero signal level Z. In a demodulated signal Sd with an N-shaped curve characteristic, the peak, which is the maximum value of the demodulated signal Sd, appears at a frequency lower than the zero signal level Z. The received information storage unit 54 pre-stores the offset value Vs for the demodulated signal Sd with an S-shaped curve characteristic and the offset value Vn for the demodulated signal Sd with an N-shaped curve characteristic. The offset values ​​Vs and Vn can be pre-measured and stored from the demodulated signal Sd measured in an environment where no undulation occurs.

[0080] As shown in Figure 10, if the peak of the filter output value is positive (step S207, Yes), the received information storage unit 54 calculates the frequency by adding the offset value Vs for the S-curve of the demodulated signal Sd to the zero-level signal Z (step S208), and includes the calculated value as frequency information Df in the received information Dr (step S210). On the other hand, if the peak of the filter output value is negative (step S207, No), the received information storage unit 54 calculates the frequency by subtracting the offset value Vn for the N-curve of the demodulated signal Sd to the zero-level signal Z (step S209), and includes the calculated value as frequency information Df in the received information Dr (step S210).

[0081] Figure 14 is a schematic diagram showing the selection of received information Dr in the refinement mode. As shown in Figure 14, when the sweep reaches the termination frequency fe of a predetermined frequency range fb, the system switches from radio wave reception mode to refinement mode. In radio wave reception mode, when seven demodulated signals Sd1 to Sd7 are detected during the sweep, frequency information Df1 to Df7 is acquired for all demodulated signals Sd1 to Sd7, and radio wave intensity levels Ds1 to Ds7 are also acquired, and received information Dr1 to Dr7 is stored.

[0082] The selection unit 55 selects a predetermined number of received information Drs, for example, four. The selection criteria are in descending order of radio wave intensity level Ds. However, the review determination unit 56 reviews the selected received information Drs in the order in which radio waves were received during the sweep. The predetermined number is the maximum value. If the number of received information Drs is less than the predetermined number, all received information Drs are reviewed in the order in which radio waves were received during the sweep.

[0083] While continuing to sweep within a predetermined frequency range fb, the received information Dr of the detected demodulated signal Sd is stored. When the sweep reaches the termination frequency fe, the radio wave reception mode ends, and the system switches from radio wave reception mode to refinement mode. In refinement mode, a predetermined number of received information Dr1, Dr3, Dr6, and Dr7 with high radio wave intensity levels Ds are selected from the seven stored received information Dr1 to Dr7.

[0084] Figure 15 is a schematic diagram showing the operation of the detector 1's refinement process. As shown in Figure 15, after the sweep of the predetermined frequency range fb is completed, the radar waves of the speed measuring device are sequentially determined for the radio waves at the frequencies indicated by the selected received information Dr1, Dr3, Dr6, and Dr7. By selecting in the order in which the information was received during the sweep, the detection signal Sc in refinement mode becomes a step-like structure with a sequentially increasing voltage. Therefore, the signal amplitude when the next received information Dr is selected becomes smaller, and the detection signal Sc becomes more stable. On the other hand, if the refinement mode is executed sequentially starting with the received information Dr with the highest radio wave intensity level Ds, the possibility of detecting the radar waves of the speed measuring device earlier increases, and the refinement mode may be shortened.

[0085] As described above, the detector 1 of this embodiment is installed in a vehicle and detects radar waves from a speed measuring device, and comprises a receiving unit 21 including an antenna, a receiving detection unit 22, and a refining unit 51. The receiving detection unit 22 generates an intermediate frequency signal while sweeping a predetermined frequency range up to the terminal frequency, and detects radio wave reception based on the intermediate frequency signal. The refining unit 51 fixes the frequency of the radio wave detected by the receiving detection unit 22, and determines that it is the reception of radar waves from a speed measuring device if the radio wave reception is detected continuously for a predetermined time.

[0086] The radio waves detected during the sweep are undulation signals generated by low-frequency noise SL superimposed when radio waves are received while sweeping. The analysis unit 51 identifies the frequency of the radio waves when this low-frequency noise SL is not superimposed from the undulation signal Sw, and fixes it to the identified frequency to detect the continuation of radio wave reception.

[0087] This allows the demodulated signal Sd to be correctly fixed at the frequency where its peak is located, without having to fix it at a frequency deviating from the frequency where the peak of the demodulated signal Sd is located and then scrutinize its continuity. Consequently, the radar wave detection accuracy of the speed measuring device is improved.

[0088] Furthermore, the correction of the demodulated signal Sd by the scrutiny unit 51 excludes the white noise range, identifies the zero signal level included in the undulating signal Sw, and fixes it to a frequency shifted by a pre-stored offset value from that zero signal level. In this way, the frequency information Df from the undulating signal Sw can be corrected to the frequency information Df of the demodulated signal Sd without undulation through such a simple process, and the scrutiny accuracy can be improved without lengthening the scrutiny time.

[0089] This allows the fixed frequency to be the frequency at the peak of the radio wave intensity when the radio wave is received. Therefore, it is possible to reduce the cases in which the demodulated signal Sd falls below the threshold of the signal monitoring unit 58 without continuing for a predetermined time, even though the radar wave from the speed measuring device has been received. It is also possible to reduce the cases in which signals from other devices that do not originate from the speed measuring device continue for a predetermined time.

[0090] Furthermore, in the detector 1 of this embodiment, the detailing unit 51 is configured to limit the detection of radio waves during a sweep to a predetermined number of radio wave frequencies in descending order of radio wave intensity level Ds, and to determine whether they are radar waves from a speed measuring device. As a result, even if a large number of radio waves are detected during the previous sweep, the start of the next sweep will not be delayed, and the opportunity to receive radar waves from a speed measuring device will be improved.

[0091] To perform a detailed examination limited to a predetermined number of radio wave frequencies with high radio wave intensity levels Ds, the examination unit 51 includes a reception information storage unit 54, an examination target selection unit 55, and an examination determination unit 56. The reception information storage unit 54 stores reception information Dr, which is a set of frequency information Df that identifies the frequency at which radio wave reception was detected and the radio wave intensity level Ds at the time of detection. The examination target selection unit 55 sweeps up to the terminal frequency fe and then selects a predetermined number of reception information Dr in descending order of radio wave intensity levels Ds. The examination determination unit 56 sweeps up to the terminal frequency fe and then refers to the reception information Dr selected by the examination target selection unit 55. The examination determination unit 56 then fixes the frequency of the radio wave to be received based on the frequency information Df included in the reception information Dr and determines whether it is a radar wave from a speed measuring device.

[0092] In this way, even if radio waves are received during a sweep, the sweep is not stopped for further analysis. Instead, the sweep is completed, and the received radio waves are stored as reception information Dr. This allows for analysis to be limited to a predetermined number of radio wave frequencies in descending order of radio wave intensity level Ds. Furthermore, even with methods other than this, limiting the analysis to a predetermined number of radio wave frequencies in descending order of radio wave intensity level Ds prevents delays in the start of the next sweep, even if many radio waves are detected during the previous sweep, thereby improving the opportunity to receive radar waves from the speed measuring device.

[0093] In this embodiment, a double superheterodyne system was used as an example for explanation, but the system is not limited to this. For example, a third-stage local oscillator and mixer may be included to detect the intermediate frequency signal of the third stage. That is, the receiving detection unit 22 may be equipped with three or more stages of local oscillators and mixers.

[0094] Furthermore, in this detector 1, when it is determined during a sweep that the radar waves of the speed measuring device have been received, the notification unit 6 is instructed to notify the information. However, it is not limited to this, and the notification unit 6 may only notify the information when it is determined that the radar waves of the speed measuring device have been received continuously over multiple sweep cycles. In other words, the accuracy of false alarm suppression may be improved as the opportunities to receive radar waves from the speed measuring device are increased.

[0095] Furthermore, the notification unit 6 may be configured to notify information if it is determined that the radar waves of the speed measuring device have been received for a predetermined number of cycles or more within a series of consecutive cycles. This also improves the accuracy of suppressing false alarms.

[0096] (Modified version of the first embodiment) In the first embodiment, the detector 1 performed two modes: a radio wave reception mode in which a predetermined frequency range fb was swept from the starting frequency fs at one end to the ending frequency fe at the other end, and a reconnaissance mode in which, after the sweep was completed up to the ending frequency fe, the received radio wave was examined to determine if it was a radar wave from a speed measuring device. However, the detector 1 may also stop the sweep each time it receives a radio wave during the radio wave reception mode and switch to the reconnaissance mode for the currently received radio wave.

[0097] Figure 16 is a block diagram showing the configuration of the control unit 5 according to this modified example. Note that components identical to those in the first embodiment or with the same functions are denoted by the same reference numerals, and detailed explanations are omitted. As shown in Figure 16, the refinement unit 51 includes a swell correction unit 59 instead of the received information storage unit 54 and the refinement target selection unit 55. The swell correction unit 59 corrects the frequency information Df obtained from the swell signal Sw, which is generated when low-frequency noise SL is superimposed on the demodulated signal Sd, to the frequency of the detection signal Sc without swell.

[0098] The tuning control unit 57 generates a specific frequency continuation control signal Cc corresponding to the frequency information Df acquired by the undulation correction unit 59. The sweep control unit 27 continuously inputs a constant voltage signal CV corresponding to the specific frequency continuation control signal Cc to the second-stage local oscillator unit 25. This refinement mode using the specific frequency continuation control signal Cc is accompanied by a sweep stop. Furthermore, when the refinement mode after the sweep stop ends, the tuning control unit 57 generates a sweep restart signal Cr. The sweep control unit 27 restarts the radio wave reception mode by sweeping from the frequency at which the sweep stop occurred.

[0099] Figure 17 is a flowchart showing an example of operation by the control unit 5 in this modified example. As shown in Figure 17, the tuning control unit 57 starts the sweep (step S301). This sweeps a predetermined frequency range fb from the starting frequency fs. The reception determination unit 53 analyzes the detected signal Sc input by the sweep and determines whether it corresponds to the reception of radio waves (step S302).

[0100] If radio wave reception is involved (step S302, Yes), the swell correction unit 59 acquires frequency information Df of the demodulated signal Sd by the operation shown in step S104 of Figure 6 or in Figure 10 (step S303). That is, the correlation filter and offset values ​​Vs and Vn are used to calculate the frequency corresponding to the peak of the demodulated signal Sd from the swell signal Sw, which has low-frequency noise SL superimposed on it.

[0101] When the undulation correction unit 59 acquires frequency information Df, the tuning control unit 57 fixes the frequency of the received radio wave in the frequency information Df (step S304). That is, the tuning control unit 57 inputs a specific frequency continuation control signal Cc to the sweep control unit 27, for example, instructing it to continuously output a constant voltage signal CV corresponding to the frequency information Df. While the frequency is fixed in the frequency information Df, the signal monitoring unit 58 monitors whether the demodulated signal Sd continues for a predetermined time (step S305).

[0102] If the demodulated signal Sd continues for a predetermined time or longer (step S305, Yes), the notification control unit 52 causes the notification unit 6 to notify (step S306). Then, the tuning control unit 57 restarts the sweep from the frequency at which the sweep stopped (step S307). That is, the tuning control unit 57 inputs the sweep restart signal Cr to the sweep control unit 27. The sweep control unit 27 inputs the sweep voltage signal SV of the next stage after the sweep stop, continuously changing it up to the termination sweep voltage signal SVe.

[0103] If the demodulated signal Sd does not continue for a predetermined time or longer (step S305, No), no notification processing is performed. The tuning control unit 57 restarts the sweep from the frequency at which the sweep stopped (step S307).

[0104] When the sweep of the predetermined frequency range fb is completed up to the termination frequency fe (step S308, Yes), the process returns to step S301 and starts the sweep of the next cycle (steps S301~).

[0105] Figure 18 shows the operation of this modified example. As shown in Figure 18, when demodulated signals Sd1 to Sd7 are detected during sweep S1, a sweep stop is performed to temporarily pause the sweep after each detection of demodulated signals Sd1 to Sd7, allowing for verification that it is the radar wave of the speed measuring device. Even with this sweep method, even if a wave signal Sw occurs, it can be fixed to an accurate frequency and its continuity can be verified, thus increasing the accuracy of detecting the radar wave of the speed measuring device and suppressing false alarms.

[0106] (Second embodiment) A detector 1 according to a second embodiment of the present invention will be described in detail with reference to the drawings. In the second embodiment, components that are the same as those in the first embodiment or have the same functions are denoted by the same reference numerals and their detailed descriptions are omitted.

[0107] The radar waves emitted by the speed measuring device include K-band waves, but some are unmodulated. Figure 19 is a flowchart showing the operation of detector 1 in relation to these K-band, unmodulated radar waves. Detector 1 performs the processes from steps S101 to S108 and determines whether the demodulated signal Sd continues for a predetermined time or longer (step S109). If the demodulated signal Sd continues for a predetermined time or longer (step S109, Yes), it further determines whether false alarm suppression is turned on (step S410).

[0108] The false alarm suppression function is pre-configured based on user input. Input devices that accept user input include a touch panel, a remote control separate from the detector 1, a physical button attached to the detector 1, or a vehicle display that is connected to the detector 1 for communication.

[0109] If false alarm suppression is turned on (step S410, Yes), it is determined that the frequency identified and fixed by the correction of the frequency information Df, i.e., the swell signal Sw, is within a more specific range within the K band (step S411). The refinement determination unit 56 stores thresholds indicating the lower and upper limits of the specific range, and determines by comparison whether the frequency of the frequency information Df exceeds the lower threshold and the frequency of the frequency information Df falls below the upper threshold. It is preferable that the types of frequency information Df and thresholds be the same, but if they are of different types, the refinement determination unit 56 can unify the types by conversion.

[0110] If the frequency indicated by the frequency information Df is within a more specific range within the K band (step S411, Yes), the verification and determination unit 56 further determines whether the detected signal S is an unmodulated wave (step S412). If the detected signal S is an unmodulated wave (step S412, Yes), the notification control unit 52 causes the notification unit 6 to notify information indicating that the radar wave of the speed measuring device has been received (step S413).

[0111] Here is an example of how to identify an unmodulated wave: The tuning control unit 57 modulates the second-stage local oscillator signal based on the frequency information Df until the demodulated signal Sd reaches a voltage level at or near the zero point Sz. When the demodulated signal Sd reaches a voltage level at or near the zero point Sz, the low-pass filter cuts out the high-frequency components from the demodulated signal Sd. After passing through the low-pass filter, in the case of an unmodulated wave, no waveform appears in the demodulated signal Sd, and the demodulated signal Sd becomes linear. Therefore, if a waveform appears in the demodulated signal Sd, it is a modulated wave, and if the demodulated signal Sd is linear, it is an unmodulated wave.

[0112] On the other hand, if the frequency information Df included in the received information Dr is within a more specific range within the K band (step S411, Yes), but the detected signal S is not an unmodulated wave (step S412, No), the notification control unit 52 will not broadcast the information.

[0113] The detailed determination unit 56 further determines whether the detected signal S is an unmodulated wave (step S414) even if the frequency indicated by the frequency information Df included in the received information Dr is not within a more specific range within the K band (step S411, No). If the detected signal S is an unmodulated wave (step S414, Yes), the notification control unit 52 outputs information to the notification unit 6 indicating that a radio wave has been received, although it does not definitively determine that it is a radar wave from a speed measuring device (step S415).

[0114] The information indicating that a radio wave has been received is a notification that does not specify that it is a radar wave from a speed measuring device. If it is not within a specific range within the K band, it is possible that a speed measuring device emitting modulated waves in the K band has been detected, but if it is an unmodulated wave, it is also possible that a speed measuring device emitting unmodulated waves in the K band has been detected. Because the situation is uncertain, and to account for the possibility of false reception, information indicating that a radio wave has been received without specifying that it is a radar wave from a speed measuring device is provided to remind users to comply with speed limits.

[0115] Even if the demodulated signal Sd continues for a predetermined time or longer (step S109, Yes), but false alarm suppression is off (step S410, No), the notification control unit 52 does not definitively identify it as a radar wave from the speed measuring device, but outputs information to the notification unit 6 indicating that a radio wave has been received (step S415).

[0116] On the other hand, if the frequency information Df included in the received information Dr is not within a specific range within the K band (step S411, No), and the detected signal S is not an unmodulated wave (step S414, No), the notification control unit 52 will not broadcast the information.

[0117] (Modified version of the second embodiment) Figure 20 is a flowchart illustrating another example of the operation of detector 1 in relation to unmodulated radar waves in the K-band. Detector 1 performs the processes from steps S101 to S108 and determines whether the demodulated signal Sd continues for a predetermined time or longer (step S109). If the demodulated signal Sd continues for a predetermined time or longer (step S109, Yes), it further determines whether false alarm suppression is turned on (step S410). The on / off setting for false alarm suppression is determined in advance based on user input.

[0118] If false alarm suppression is turned on (step S410, Yes), it is determined that the frequency identified and fixed by the correction of the frequency information Df, i.e., the swell signal Sw, is within a more specific range within the K band (step S411). The refinement determination unit 56 stores thresholds indicating the lower and upper limits of the specific range, and determines by comparison whether the frequency of the frequency information Df exceeds the lower threshold and the frequency of the frequency information Df falls below the upper threshold. It is preferable that the types of frequency information Df and thresholds be the same, but if they are of different types, the refinement determination unit 56 can unify the types by conversion.

[0119] If the frequency indicated by the frequency information Df is within a more specific range within the K band (step S411, Yes), the verification and determination unit 56 further determines whether the detected signal S is an unmodulated wave (step S412). If the detected signal S is an unmodulated wave (step S412, Yes), the notification control unit 52 causes the notification unit 6 to notify information indicating that the radar wave of the speed measuring device has been received (step S413).

[0120] On the other hand, if the frequency information Df included in the received information Dr is within a more specific range within the K band (step S411, Yes), but the detected signal S is not an unmodulated wave (step S412, No), the notification control unit 52 will not broadcast the information.

[0121] The detailed determination unit 56 determines whether the detected signal S is an unmodulated wave if the frequency indicated by the frequency information Df included in the received information Dr is not within a specific range within the K band (step S411, No). If the detected signal S is not an unmodulated wave (step S414, No), the notification control unit 52 causes the notification unit 6 to notify information indicating that the radar wave of the speed measuring device has been received (step S413). If the frequency is not within a specific range within the K band and is not an unmodulated wave, there is a high possibility that a speed measuring device emitting a modulated wave in the K band has been detected, so information indicating that the radar wave of the speed measuring device has been received is notified.

[0122] On the other hand, if the frequency information Df included in the received information Dr is not within a specific range within the K band (step S411, No), but the detected signal S is an unmodulated wave (step S414, Yes), the notification control unit 52 will not broadcast the information. If it is not within a specific range within the K band, it is possible that a speed measuring device emitting a modulated wave in the K band has been detected, but if it is an unmodulated wave, it is also possible that a speed measuring device emitting an unmodulated wave in the K band has been detected. Since the situation is uncertain, the notification is withheld assuming the possibility of erroneous reception.

[0123] Furthermore, if the demodulated signal Sd continues for a predetermined time or longer (step S109, Yes), but false alarm suppression is off (step S410, No), the notification control unit 52 does not definitively identify it as a radar wave from the speed measuring device, but outputs information to the notification unit 6 indicating that a radio wave has been received (step S415).

[0124] (Modification 2 of the second embodiment) Figure 21 is a flowchart showing yet another example of the operation of detector 1 in relation to unmodulated radar waves in the K-band. Detector 1 performs the processes from steps S101 to S108 and determines whether the demodulated signal Sd continues for a predetermined time or longer (step S109). If the demodulated signal Sd continues for a predetermined time or longer (step S109, Yes), it further determines whether false alarm suppression is turned on (step S410).

[0125] If false alarm suppression is turned on (step S410, Yes), it is determined whether the frequency information Df, i.e., the frequency identified and fixed by the correction of the swell signal Sw, is within a more specific range within the K band (step S411).

[0126] The verification and determination unit 56 determines if the frequency indicated by the frequency information Df is within a more specific range within the K band (step S411, Yes), and further determines whether the detected signal S is an unmodulated wave (step S412). If the detected signal S is an unmodulated wave (step S412, Yes), the notification control unit 52 identifies the type of speed measuring device and causes the notification unit 6 to notify it of information indicating that a radar wave has been received (step S413). Here, the notification includes information that identifies it as a speed measuring device that emits an unmodulated wave in the K band.

[0127] On the other hand, if the frequency information Df included in the received information Dr is within a more specific range within the K band (step S411, Yes), but the detected signal S is not an unmodulated wave (step S412, No), the notification control unit 52 will not broadcast the information.

[0128] If the frequency information Df included in the received information Dr is not within a specific range within the K band, the verification and determination unit 56 further determines whether the detected signal S is an unmodulated wave (step S414). If the detected signal S is not an unmodulated wave (step S414, No), the notification control unit 52 identifies the type of speed measuring device and causes the notification unit 6 to notify it of information indicating that a radar wave has been received (step S413). Here, the notification includes information that identifies it as a speed measuring device that emits a modulated wave in the K band.

[0129] On the other hand, if the frequency information Df included in the received information Dr is not within a specific range within the K band (step S411, No), but the detected signal S is an unmodulated wave (step S414, Yes), the notification control unit 52 does not broadcast any information. Also, if the demodulated signal Sd continues for a predetermined time or longer (step S109, Yes), but false alarm suppression is off (step S410, No), the notification control unit 52 does not definitively identify it as a radar wave from a speed measuring device, but outputs information to the notification unit 6 indicating that a radio wave has been received (step S415).

[0130] (Other embodiments) As described above, several embodiments of the present invention have been presented, but these embodiments are presented as examples and are not intended to limit the scope of the invention. Specifically, combinations of all or any of the embodiments and modifications are also included. The embodiments described above can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and their variations are included in the scope and essence of the invention, as well as in the claims and their equivalents.

[0131] For example, when a demodulated signal Sd, which is a signal with a voltage level above a certain level, i.e., a signal exceeding white noise Sn, is received, reception information Dr is generated. Alternatively, the frequency and voltage of all radio waves, including white noise Sn, may be sampled and stored, and a predetermined number of high-voltage signals may be picked from this sample. In other words, the reception information storage unit 54 may store all radio waves, including white noise Sn, as reception information Dr, and the reception determination unit 53 that distinguishes between white noise Sn and demodulated signal Sd may be eliminated. [Explanation of Symbols]

[0132] 1 detector 10 cabinets 11 Back 12 Front 13 Reception Area 14 screens 15 speakers 16 lamps 2. Radio wave receiving system 21 Receiving unit 22 Receiving detection unit 23. First stage local oscillator 24. Mixed section of the first stage 25 Second stage local oscillator 26. Second stage mixing section 27 Sweep Control Unit 28 Detection section 3. Positioning signal receiving system 4 Input section 5 Control Unit 51. Inspection Department 52 Notification Control Unit 53 Reception determination unit 54 Received Information Storage Unit 55 Selection of items to be examined 56. Examination and Judgment Department 57 Synchronization Control Unit 58 Signal Monitoring Unit 59. Swell correction section 6 Hochi Department RF Received Signal LFf is the local oscillator signal of the first stage. IFf First stage intermediate frequency signal LFs Second stage local oscillator signal IFs: Second stage intermediate frequency signal fb predetermined frequency range fs starting frequency fe Termination frequency SV sweep voltage signal SVs Start sweep voltage signal SVe termination sweep voltage signal CV constant voltage signal Cs sweep start control signal Ce sweep completion notification signal Cc Specific Frequency Continuous Control Signal Cr sweep restart signal Sc detection signal SL Low-Frequency Noise Sw swell signal Se substitution waveform Z signal zero level Vs offset value Vn offset value Sd demodulated signal Dr. Received Information Df frequency information Ds signal strength level

Claims

1. A detector installed on a vehicle that detects radar waves from a speed measuring device, The receiving section, including the antenna, A receiving detection unit that generates an intermediate frequency signal while sweeping a predetermined frequency range up to the termination frequency, and detects radio wave reception based on the intermediate frequency signal, The reception detection unit fixes the frequency of the radio waves it detects, and if radio wave reception is detected continuously for a predetermined time, the verification unit determines that it is the reception of radar waves from the speed measuring device. Equipped with, The radio waves detected during the sweep are undulating signals generated by low-frequency noise superimposed when radio waves are received while sweeping. The aforementioned inspection unit identifies the frequency of the radio wave in a state where the low-frequency noise is not superimposed from the undulation signal, and detects the continuation of radio wave reception by fixing it to the identified frequency. A detector characterized by the following features.

2. The aforementioned analysis unit identifies the zero signal level included in the undulation signal, excluding the white noise range, and fixes it to a frequency shifted by a pre-stored offset value from that zero signal level. The detector according to claim 1, characterized by the following:

3. The fixed frequency is the frequency at which the radio wave intensity peaks when the radio wave is received. A detector according to claim 1 or 2, characterized by the above.

4. The system includes a notification unit that notifies information when it is determined that the radar wave of the speed measuring device has been received. A detector according to claim 1 or 2, characterized by the above.

5. The notification unit shall notify information when it is determined that the radar wave of the speed measuring device has been received a predetermined number of times during a series of sweeps. The detector according to claim 4, characterized by the following:

6. The receiving unit receives radio waves and converts them into a received signal. The reception detection unit is A multi-stage local oscillator, each outputting a signal of a predetermined frequency, The first stage mixer mixes the received signal with a signal of the frequency output by the first stage local oscillator to output an intermediate frequency signal of the first stage, A second or subsequent stage mixing unit mixes the signal of the frequency output by the local oscillator of the same stage with the intermediate frequency signal of the preceding stage to output the intermediate frequency signal of the next stage, A sweep control unit that sweeps the frequency of the signal output by any of the local oscillators from the second stage onward to the termination frequency of a predetermined frequency band, Having A detector according to claim 1 or 2, characterized by the above.

7. The receiving unit receives radio waves and converts them into a received signal. The reception detection unit is A two-stage local oscillator, each outputting a signal of a predetermined frequency, The first stage mixer mixes the received signal with a signal of the frequency output by the first stage local oscillator to output an intermediate frequency signal of the first stage, The second stage mixer mixes the frequency signal output by the second stage local oscillator with the intermediate frequency signal of the first stage to output the intermediate frequency signal of the next stage, A sweep control unit that sweeps the frequency of the signal output by the second stage local oscillator up to the termination frequency of a predetermined frequency band, Having A detector according to claim 1 or 2, characterized by the above.

8. The aforementioned inspection unit determines that the reception of a radio wave of a fixed frequency is the radar wave of the speed measuring device if it is detected that the reception of a radio wave of a fixed frequency continues for a predetermined time, the frequency of the radio wave detected by the reception detection unit is within a specific range, and furthermore, the radio wave detected by the reception detection unit is an unmodulated wave. A detector according to claim 1 or 2, characterized by the above.

9. The aforementioned inspection unit detects that radio waves of a fixed frequency are received continuously for a predetermined time, determines whether the frequency of the radio waves detected by the reception detection unit is within a specific range, and determines whether the radio waves detected by the reception detection unit are unmodulated waves. The notification unit determines that, if the results of the analysis unit indicate that radio wave reception is detected for a predetermined period of time, but the frequency of the radio wave detected by the reception detection unit is not within a specific range, and the radio wave detected by the reception detection unit is an unmodulated wave, then the radio wave detection information does not identify it as reception of the radar wave of the speed measuring device. The detector according to claim 4, characterized by the following:

10. The aforementioned inspection unit detects that radio waves of a fixed frequency are received continuously for a predetermined time, determines whether the frequency of the radio waves detected by the reception detection unit is within a specific range, and determines whether the radio waves detected by the reception detection unit are unmodulated waves. The notification unit shall, if the results of the analysis unit indicate that radio wave reception is detected for a predetermined period of time, but the frequency of the radio wave detected by the reception detection unit is not within a specific range, and the radio wave detected by the reception detection unit is not an unmodulated wave, then provide information indicating that it is the reception of a radar wave from the speed measuring device. The detector according to claim 4, characterized by the following:

11. The aforementioned inspection unit detects that radio waves of a fixed frequency are received continuously for a predetermined time, determines whether the frequency of the radio waves detected by the reception detection unit is within a specific range, and determines whether the radio waves detected by the reception detection unit are unmodulated waves. The notification unit, when the results of the detailed analysis unit indicate that radio wave reception has been detected for a predetermined period of time, identifies the type of speed measuring device and notifies information indicating that it is a radar wave from the speed measuring device, depending on whether the frequency of the radio wave detected by the reception detection unit is within a specific range and whether the radio wave detected by the reception detection unit is an unmodulated wave. The detector according to claim 4, characterized by the following:

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