# Patent

## Title
Radar false alert reduction

## Abstract

A radar detector suppresses alerts from vehicle guidance systems, by sweeping for a consistent radar signal; the center frequency of the signal is stored and the detector suppresses warnings of radar signals near that frequency. The detector uses an enhanced method for suppression of signals near a known location of a false signal source; in the event the detector detects a radar signal and finds a matching stored false signal, the detector will first compare the strength of the received signal to a threshold strength that is computed based upon the distance of the detector from the stored false signal, and will only suppress signals below threshold. The detector includes a camera directed to the road in the vicinity of the vehicle. Image data from the camera is processed to identify police vehicles as identified by flashing lights, a profile including a rooftop light bar and/or highly contrasting colored panels.

## Background
BACKGROUND OF THE INVENTION
U.S. Pat. No. 6,670,905, invented by the inventor named herein, and hereby incorporated by reference, discloses a GPS enabled radar detector that uses GPS to aid in the management of non-police-related or otherwise irrelevant sources of radar signals, permitting the detector to dynamically improve its handling of such sources and reduce false alerts. The detector references previously-stored geographically-referenced information on such sources, and compares the detector's current location to locations of known stationary false alert sources of radar to improve the handling of detection of those sources. When the detector is within a threshold distance of a stored false alert source, the detector suppresses alerts to frequency bands or sub-bands that correlate to the frequency of the known false alert source. False sources may be manually identified and “locked out” by the user, or may be automatically identified based upon multiple repeated encounters of the detector with the source at a particular geographic area.
Systems embodying the invention of the '905 patent have been successfully commercialized by the assignee of this application, and have proven commercially viable, but those systems remain subject to certain vulnerabilities which will be discussed herein.
One vulnerability is false radar alerts created by traffic sensing equipment installed in many major metropolitan areas. The signals from traffic sensors appear in police radar bands, and are emitted in short bursts at a regular cadence. Because traffic sensors are geographically fixed and operate in a consistent frequency range, it is possible for a radar detector user to manually lockout traffic sensor alerts; however, traffic sensor signals do not appear regularly enough to be reliably locked out automatically, at least without a greater than normal number of encounters. In response to this source of false signals, the assignee developed a Traffic Sensor Rejection (TSR) method, which searches for the characteristic cadence and frequency of traffic sensor systems, and suppresses alerts of those systems using a processing logic separate from the location-based lockout described in the '905 patent. Because this logic is separate from location based lockouts, police radar or police-like false signal sources appearing in the same frequency band and same geographic area as a TSR signal will not be suppressed by the TSR method, which is preferable to a location based frequency lockout in that area which would potentially suppress police signals as well.
Another vulnerability is the increasing number of vehicle-borne radar sources. Examples include radar based systems attached to vehicles for lane sensing, adaptive cruise control, collision prevention, automated parking, and the like, which will be collectively identified herein as “vehicle guidance systems”. One specific example of these systems is the Mercedes-Daimler Distronic system, which emits a 24.125 GHz K-band frequency to provide adaptive vehicle cruise control, which is in the band used by police and normally detected by a radar detector whenever it is near to an operative Distronic system. Vehicle guidance systems often create an annoying false alarm when a radar detector passes the source vehicle, and this false alarm cannot be suppressed based on location because the signal source is a mobile vehicle. The annoyance becomes critical when the vehicle with the radar detector is itself carrying a vehicle guidance system; the constant alerting in this scenario essentially puts the vehicle operator to a choice between disabling an entire band of radar detection (or foregoing radar detection entirely), and disabling the vehicle guidance system.
Efforts are underway by the assignee to identify characteristic cadences or other profiles of vehicle guidance systems, much as was done for TSR, and some have been effectively identified and suppressed via a separate methodology like that used for TSR. However, some vehicle guidance systems have so far eluded effective characterization in this manner.
A third vulnerability of the existing systems is that location based lockouts can potentially prevent alerting to police radar that happens to appear in the same frequency range and within a geographic range of a stationary source. As radar detectors become more sensitive the effective scope of a location lockout area must increase to ensure that alerts to the false signal are suppressed, which entails also increasing the geographic area in which alerts will be given to other sources in the same frequency ranges, including police radar sources. A regular criticism of location based lockout methods is the potential a radar detector will fail to alert to police radar which happens to coincide in location and frequency to a stored false signal. It would be desirable to improve the manner in which stationary false signals are processed to reduce the likelihood that an alert to actual police radar is suppressed.
A final vulnerability of the existing systems is the continuing adoption of ‘instant-on’ and line of site speed monitoring technology. A radar detector provides advance warning of police speed monitoring by detecting the monitoring of other cars that are typically ahead of the vehicle carrying the radar detector. Modern radar guns which operate in the Ka band can turn on and off rapidly, on a car-by-car basis. If there is a long enough interval between uses of the gun, a radar detector will not be able to pick up the stray radar emissions from previous interrogations to give advance warning of the use of radar. Laser (LIDAR) speed detection poses an even greater challenge for the reason that it is generally line of sight and provides very little advance warning of its use, if any. To respond to these challenges the assignee and others have developed social networks through which drivers can share radar events and sightings of police into a social network, so that a warning can be delivered to other drivers approaching the area. Unfortunately, users of social networks often report police activities that are not actually speed traps, for example, social network users may warn of a police car that is driving with traffic, waiting at a traffic light on a cross street, or involved in other activities that are not characteristic of a fixed location speed trap. Alerts that can be confirmed, e.g., via radar detection, are more reliable, but the social network cannot rely only upon radar-based alerts, for the reason that a police car on station at a speed trap may be using instant-on radar or LIDAR, in which case not every vehicle will be exposed to radar. Accordingly, it would be useful to provide a method for better identifying particular situations which are actually indicative of a speed trap, such as police positioned at a roadside monitoring passing traffic, or operating its light bar adjacent to a stopped car.
SUMMARY OF THE INVENTION
The present invention addresses the shortcomings of the prior art by improving a radar detector in accordance with several different aspects.
According to a first aspect of the present invention, the challenge of false alarms from vehicle guidance systems is addressed by introducing a local source lockout sequence into the operation of a radar detector. The local source lockout sequence may be performed at any time of detector operation, but in one example it is performed when the radar detector is first powered. In the local source lockout sequence the radar detector sweeps for radar signals that are steadily present and/or appear to be location independent, and thus are characteristic of vehicle guidance systems on the vehicle carrying the radar detector. If such a signal is found, the radar detector identifies a center frequency for the signal, and stores that center frequency for future reference. Thereafter, the detector will suppress warnings of a radar signal that is detected at frequencies that are near to the stored center frequency. The center frequency may be in any of the sensitive bands of the radar detector, including the K-band, Ka-band or X-band. Furthermore, the detector may have a setting to enable or disable the local source lockout sequence, so that this sequence may be disabled, e.g., for vehicles that do not have vehicle guidance systems. Furthermore, the detector may identify cases in which two discriminable signals appear within the range of the stored center frequency, and in those cases, the detector will produce an alert (provided there is no applicable location-based lockout), thus avoiding to the extent possible suppressing police radar alerts.
In a second aspect, the invention features an enhanced method for suppression of signals near a known location of a false signal source. Specifically, in the event the detector detects a radar signal and finds a matching stored false signal (that is, the detected signal is within the frequency subrange of the stored false signal, and the detector is in a location near to the stored a known false signal source), rather than suppressing the received signal, the detector will first compare the strength of the received signal to a threshold strength that is computed based upon the distance of the detector from the stored false signal, and if the received signal exceeds the threshold strength the alert of the received signal is reported to a more prominent extent than if the received signal is below the threshold strength. For example, signals below the threshold may be reported by a minimal visual alert without accompanying warning sounds, whereas signals above the threshold may be reported with visual and audible cues in the manner of other radar signal detections. In the specific embodiment disclosed, the threshold is set at 3 dB higher than an expected signal strength, and the expected signal strength is computed according to an inverse square-law relationship between signal strength and the distance of the radar detector from location stored for the false signal source. In a most particular embodiment, signals falling below the threshold are tracked over time and in the event they are persistent over time, an alert is generated to those signals notwithstanding signal strength below the threshold.
According to a third aspect, the invention features an enhanced method for identifying police activity that is indicative of a speed trap, to improve the reliability of warnings of police activity delivered via social networks. To implement this method, a camera is integrated into a radar detector, the camera directed to the road in the vicinity of the vehicle. The radar detector gathers image data from the camera and processes that data to identify police vehicles in the image. In particular embodiments the processing by the radar detector evaluates sequential images to identify flashing lights characteristic of a functioning light bar on a police or emergency vehicle. In another embodiment the processing by the radar detector evaluates one or more images to identify the profile of a vehicle that is characteristic of a police vehicle (e.g., having a rooftop light bar and/or highly contrasting colored panels) and/or which is stationed to monitor traffic, such as at a roadside in a position that is not correlated with crossing traffic at an intersection. The radar detector may respond to image(s) indicative of police activity by automatically generating an alert to other drivers in a social network, or by suggesting to a vehicle operator the generation of such an alert, subject to validation by the vehicle operator.
The above and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a radar detector block diagram according to principles of the present invention;
FIG. 2 shows a flow chart of operation of the radar detector of FIG. 1 performing a lockout of vehicle guidance related false signals;
FIG. 3 shows a flow chart of operation of the radar detector of FIG. 1 performing evaluation of a detected radar signal in connection with stored locations of false signals;
FIG. 4 shows a flow chart of operation of the radar detector of FIG. 1 performing evaluation of image or video data from the camera included in the detector.



The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a radar detector 20 according to principles of the present invention, which features a fusion processor 22 for controlling all functions of the unit. Fusion processor receives information on radar signals from a conventional microwave receiver 24, coupled to processor 22 via a digital signal processor (DSP) 26. Microwave receiver 24 and DSP 26 may utilize any of the techniques known in the art for detection of radar signals, for rejecting noise and increasing discrimination between actual and spurious police radar signals. Further, receiver 24 and DSP 26 may be controlled by an optional second CPU 25, which can enable additional signal evaluation beyond that which is possible using a DSP.
Processor 22 is further connected to a laser detector 28 for detecting police LIDAR signals. Processor 22 is further connected to a GPS receiver 32 and a separate differential GPS (DGPS) receiver 30, such that differential GPS methodologies may be used where beacon signals are available.
Processor 22 executes a stored program, found in integrated or off-chip electrically erasable programmable read only memory (EEPROM), flash memory, or masked read only memory (ROM). The processor is programmed to manage and report detected signals in various ways depending on its stored program, including by methods described herein.
Processor is coupled to a cellular interface 34 to permit social network interaction with servers and data from other radar detectors. In one embodiment cellular interface 34 comprises a BLUETOOTH® (IEEE 802.15.1) or other 802.1x compliant radio for connecting to a cellular phone, smart phone, or other cellular device, which may operate on the control of a separate application such as the assignee's “Escort Live” smartphone app. In another embodiment cellular interface 34 may itself comprise a cellular radio for direct connection to cell towers. Other communication technologies may also be used for social network interaction, such as satellite telephony, mesh networking via wifi, BLUETOOTH® (IEEE 802.15.1), or 802.1x radio of other kinds, or other standards.
The radar detector further incorporates a user input keypad or switches 36. Operational commands are conveyed by the user to processor 22 via the keypad. Processor 22 is further connected to a display 38, which may comprise one or more light emitting diodes for indicating various status conditions, or in a more feature-rich device, may include an alphanumeric or graphical display for providing detailed information to a user. A speaker 40 is also provided to enable processor 22 to deliver audible feedback to a user under various alert conditions, as is elaborated below.
Processor 22 may further include a camera 42, positioned on a front-facing, side facing or rear facing surface of the device, and a video processor 44, such as for processing video or still images from camera 42 according to methods that are described herein.
Processor 22 is further coupled to a Universal Serial Bus (USB) interface 46 that provides a means for uploading and downloading information to and from processor 22. USB interface 46 may be used to automate the assimilation of coordinate information into data structures in EEPROM 34. USB interface 46 may also be used to interface the detector to a separate host computer or product application containing a larger storage capacity than available from internal memory. USB interface 46 may also be used for the purposes of firmware upgrade. From time to time updates and bug fixes may become available, e.g. through a manufacturer website. USB interface 46 will enable the user to apply the appropriate firmware upgrade or bug fix. USB interface 46 could also be used to add other user waypoints.
Referring now to FIG. 2, methods for suppressing false alarms caused by vehicle guidance systems can be described. In general, the method of FIG. 2 uses a frequency based “lockout” (not location based), which can be used on all radar detector devices (GPS, or non-GPS based detectors). The feature can be enabled or disabled in the device Preferences. On GPS based detectors, consistency of an apparent false signal the vehicle speed can be used as a factor to disable a locked frequency range at speed ranges where the vehicle guidance systems are not enabled.
The lockout sequence 204 is enabled under several circumstances. For example, when the unit is powered on 200, if the vehicle guidance suppression mode is enabled 203, a lockout sequence 204 is performed. Alternatively, when the user encounters a vehicle guidance interference, and in response enables 202 the vehicle guidance suppression mode via a sequence of button presses, the lockout sequence may be performed. A third alternative is for the vehicle guidance lockout sequence to be automatically enabled 201 upon detection of a time consistent alert that is frequency consistent with a vehicle guidance system.
The lockout sequence 204 scans 206 the radar band for a radar signal consistent with the frequencies of known vehicle guidance systems. The signal is then evaluated 208 for consistency over time with the on/off cadence of the known vehicle guidance system. If these tests are passed, then in step 210 the center frequency of the short-range sensor of the guidance system is identified, and stored 212. The detector then pads that frequency above and below to allow for drift of both the signal and, if appropriate, the radar detector.
After a lockout has been stored, if (step 214) the detector identifies one signal in the range of the stored center frequency, it suppresses 218 an alert to the signal. For example the device may show a small visual indication that there is a detected signal, but it has been determined to be a vehicle guidance system. As a further optional test (step 216), in a GPS-enabled radar detector, the speed of the vehicle as reported by the GPS receiver may be compared to the known speed ranges of operation of the vehicle guidance system (some systems do not operate below a threshold speed, or above a threshold speed). Using this optional test 216, the alert is suppressed only if the vehicle's speed is consistent with operation of a vehicle guidance system.
When a lockout has been stored, if (step 220) the detector identifies two signals in the range of the stored center frequency, then the detector will proceed to step 220 and produce a normal alert to the radar signal, if the signal is not subject to filtering on other bases (such as TSR filtering or GPS-location based lockout)
Referring now to FIG. 3, improvements to location-lockout methods can be described. The background principle to this method is that, in free space, electromagnetic waves obey the inverse-square law, which states that the power density of an electromagnetic wave is proportional to the inverse of the square of the distance from a point source. Therefore the signal level measured by a radar detector will vary in proportion to the distance between it and a signal source that is detected by the radar detector. Current location based false signal rejection methods prevent the detection of all “qualified” signals detected within a lockout region. The lockout region, however, may encompass a large area where the radar detector is relatively sensitive.
A significant enhancement will be realized by redefining a lockout region to be “a region in which the Radar Detector's sensitivity varies in proportion to the distance between it and the focal points that define that region.” The beneficial result is that police radar can still be reported, even if the police radar frequency matches one of the frequencies that is locked for false alarm signals for a given region. This method is accordingly referred to as “Variable Sensitivity Lockout Region” or VSLR.
In current GPS system without VSLR, the lockout decision is made by examining the current location of the detector to determine if it falls within any nearby regions, which may be defined in an octagonal shape for computational simplicity. The center of each of these Octagonal regions is referred to as a focal point. For each overlapping Octagonal region, a comparison is made between the frequency of the detected signal and the frequency of signals determined as being locked in each region. If there is a match, current GPS systems will suppress the reporting of the signal.
In a VSLR-enhanced method 300, shown in FIG. 3, after a determination 302 that the vehicle location is in the region of a locked signal, and it is determined 304 that the frequency of the detected signal is one of the frequencies locked in that region, extra steps must be performed before the signal suppression decision for each focal point can occur.
In a first step 306, the signal power level of the detected signal is determined, and in step 308, a threshold signal power level is computed, defined to be approximately 3 dB higher than the normal inverse square-law signal propagation expected from the previously locked signal source. If actual police radar at a locked frequency is being operated near a locked signal source, the police radar should be reported (and not suppressed) as soon as its signal level rises above this 3 dB threshold. Accordingly, in step 310, the received signal level is compared to the threshold, and if it is greater than the threshold, in step 312 an alert to the radar signal is produced, if the signal is not subject to other filtering such as TSR or vehicle guidance system suppression as discussed above. However, if the signal is below the threshold, then it is deemed to be from the locked stationary source, and (subject to optional processing discussed below) in step 316 warnings of the signal are suppressed.
Since it is possible that police radar could be operated immediately adjacent to a rejected stationary source it is important that the VSLR method report of locked signals, even if they are weaker than the 3 dB threshold. In current products of the assignee, a detected, locked signal is identified by a minimal visual indication on the radar detector display. This visual indication may, however, fail to adequately warn of a true police radar signal. Accordingly, In addition to using a signal level threshold as mentioned above, the VSLR method may optionally include a step 314 also use signal duration as a factor in the suppression decision. In one particular example, a time threshold is computed by first computing an average value of the difference between the detected signal's power level and the threshold power level. Call this average difference X, measured in dB. If the signal is continuously detected, it will be reported (10*(1+X/4)) seconds after the first detection. Thus, a signal which remains roughly 4 dB below the threshold will be reported after a 20 second delay.
Both the 3 dB signal level threshold of step 308 and the signal duration requirement of step 314 will be applied to all focal points for all locked false signals, which are the centers of nearby Octagonal regions that encompass the current position. Note, however, that if the suppression criterion for any focal point results in a decision to suppress an alert to a signal, none of the other focal points need to be considered relative to that signal. If all of the focal considerations fail to conclude in a signal suppression decision, the signal will be reported.
Referring now to FIG. 4, methods of the present invention using camera 42 (FIG. 1) can be explained. As part of its regular survey of radar data, social network data and GPS data, the processor in step 400 will activate the camera and image processor to assess the scene visible to the camera. In step 402 the image processor, or fusion processor itself, will search the image or video available from the camera for the presence of a police vehicle or other vehicle of interest.
One circumstance of interest, step 404, is video reflecting a flashing light bar on the road, typically indicative of police or other emergency vehicles, according to a standardized color coding. Flashing police lights are strongly indicative of speed monitoring in the local area.
A second circumstance of interest, steps 406 and 408, is a vehicle profile in the image of the road that matches a police car. Per step 406 a vehicle with a profile that includes a light bar, that moves across the field of vision in a manner suggesting a roadside traffic monitoring vehicle, is indicative of a possible speed trap. Alternatively, per step 408, a vehicle with block colored panels that is similarly situated is likely a police vehicle and is suggestive of a speed trap.
In the event no circumstances of interest are identified, then the image processing is done until re-initiated. However, if a circumstance of interest is identified in step 404, 406 or 408, then in step 412 the particular circumstance is evaluated to determine if a user confirmation is required. Some circumstances, such as a flashing light bar, may be unambiguous as to their relevance to others in a social network, whereas other circumstances, such as a vehicle with block colored panels, may or may not be of interest. Accordingly, user confirmation may be required for some circumstances and not others. If user confirmation is required in step 412, then in step 416 the user is alerted to the possible police sighting and a confirmation is requested, which can be provided by a button on the detector, or on a cord connected to the detector.
If a particular sighting is confirmed, or if no confirmation is required, then a police vehicle sighting and its GPS location and, optionally, details thereof such as the image or video, vehicle direction and/or speed, and are reported to the social network for use in alerting others. If a sighting is not confirmed, however, the processing finishes without alerting the social network.
The present invention has been described in connection with several embodiments and some of those embodiments have been elaborated in substantial detail. However, the scope of the invention is not to be limited by these embodiments which are presented as exemplary and not exclusive. The scope of the invention being claimed is set forth by the following claims.

## Claims

1. A radar detector including circuitry to identify and suppress alerts of locally generated radar signals from vehicle guidance systems, the radar detector comprising a radar receiver for detecting radar signals and signal processing electronics for controlling the radar receiver and evaluating detected radar signals, the signal processing electronics comprising a processor programmed via software to:
a. perform a lockout sequence during operation of the radar detector, the lockout sequence comprising scanning a radar band for a vehicle guidance radar signal that is consistently received and otherwise consistent with vehicle guidance systems signal emissions from the vehicle carrying the radar detector;
b. identify a center frequency of a vehicle guidance signal emission identified in the preceding step, and storing the center frequency; and thereafter
c. suppress warnings of radar signals at frequencies near to the stored center frequency.

2. The radar detector of claim 1 wherein the local source lockout sequence is performed when power is first applied to the radar detector.

3. The radar detector of claim 1 wherein in the local source lockout sequence the signal processing electronics scan for radar signals that are consistently received over time.

4. The radar detector of claim 1 wherein in the local source lockout sequence the signal processing electronics scan for radar signals that are consistently received at multiple locations.

5. The radar detector of claim 1 wherein the center frequency is in one of K-band, Ka-band or X-band.

6. The radar detector of claim 1 wherein the signal processing electronics are configurable to be placed in an operative mode in which the local source lockout sequence is not performed.

7. The radar detector of claim 1 wherein the signal processing electronics perform a discrimination function to identify that two discriminable signals appear near to the stored center frequency, the radar detector producing an alert in at least one instance when two discriminable signals are detected near to the stored center frequency.

8. A radar detector including circuitry for suppressing radar detector alerts of false signals near a known location of a false signal source, the radar detector comprising a radar receiver for detecting radar signals, signal processing electronics for controlling the radar receiver and evaluating detected radar signals, and storage for known locations of false signal sources, the signal processing electronics comprising a processor programmed via software to:
a. detect a radar signal;
b. identify a stored record of a known false signal source location having a frequency correlatable to the detected radar signal;
c. compare the strength of the received signal to a threshold strength, the threshold strength being computed based upon a distance of the detector from the stored false signal;
d. alter or not provide an alert of the received signal if the received signal is below the threshold strength.

9. The radar detector of claim 8 wherein an alert of the received signal is reported by in a visual but not audible alert where the strength of the received signal is below the threshold.

10. The radar detector of claim 8 wherein an alert of the received signal is reported by a visual and audible alert where the strength of the received signal is above the threshold.

11. The radar detector of claim 8 wherein the threshold is computed as 3 dB higher than an expected signal strength for the false signal source.

12. The radar detector of claim 11 wherein the expected signal strength is computed according to an inverse square-law relationship between signal strength and the distance of the radar detector from the location stored for the false signal source.

13. The radar detector of claim 12 wherein signals falling below the threshold are tracked over time and in the event they are persistent over time, an alert is generated.

14. A radar detector implementing a method of identifying visual information relevant to speed monitoring, comprising:
a. a housing;
b. a radar receiver for detecting radar signals integrated within the housing;
c. electronics for controlling the radar receiver and evaluating detected radar signals integrated within the housing;
d. a camera integrated with the housing directed forward from the radar detector face toward the oncoming road when the radar detector is in use;
wherein the electronics gather image data from the camera and process that data to identify visual information relevant to speed monitoring in the image data.

15. The radar detector of claim 14, wherein the electronics evaluate time-sequential images to identify flashing lights characteristic of a functioning light bar on a police or emergency vehicle.

16. The radar detector of claim 14, herein the electronics evaluate one or more images to identify a vehicle profile characteristic of a police vehicle.

17. The radar detector of claim 16 wherein the vehicle profile includes a rooftop light bar.

18. The radar detector of claim 16 wherein the vehicle profile includes highly contrasting colored panels.

19. The radar detector of claim 16 wherein the vehicle profile comprises a vehicle stationed to monitor traffic.

20. The radar detector of claim 14 wherein the electronics respond to one or more images indicative of police activity by generating an alert to other drivers in a social network either unilaterally or upon confirmation by a vehicle operator.