WO2014125240A1

WO2014125240A1 - A microwave detector and corresponding detecting method

Info

Publication number: WO2014125240A1
Application number: PCT/GB2014/000049
Authority: WO
Inventors: David Jones; Simon John HARRISON
Original assignee: Isensol Limited
Priority date: 2013-02-14
Filing date: 2014-02-13
Publication date: 2014-08-21
Also published as: GB2510836A; GB201302555D0

Abstract

A detector (10) comprises a microwave module arranged to transmit microwave energy (14) and receive a reflected microwave signal (16), and a microcontroller connected to the microwave module and arranged to filter the reflected microwave signal (16) into a set of frequency sub-components, to store the amplitude of the frequency sub-components in a plurality of bins, to access one or more profiles defining threshold levels for one or more bins, and to generate an alarm signal if the stored amplitude in the bins matches a stored profile.

Description

DESCRIPTION

A MICROWAVE DETECTOR AND CORRESPONDING DETECTING METHOD

This invention relates to a detector and to a method of operating the detector.

The use of microwaves in detectors is well-known. The presence of remote objects can be detected using transmitted microwaves that are reflected back by the object and the presence of the reflected signal can be detected. European patent application publication EP 1 968 027 A1 describes a system and method for implementing ranging microwave for detector range reduction. The system utilizes a Doppler microwave system capable of detecting an object range. Multiple range limited MW stages may be configured for different ranges to determine the general range of a moving object. Based on signal levels present on these MW stages, an approximate object range and size is determined.

However, existing detectors that use microwaves do not provide any detail concerning what is detected or any further information about the nature of the object being detected beyond approximate range and size.

It is therefore an object of the invention to improve upon the known art. According to a first aspect of the present invention, there is provided a detector comprising a microwave module arranged to transmit microwave5 energy and receive a reflected microwave signal, and a microcontroller connected to the microwave module and arranged to filter the reflected microwave signal into a set of frequency sub-components, to store the amplitude of the frequency sub-components in a plurality of bins, to access one or more profiles defining threshold levels for one or more bins, and to0 generate an alarm signal if the stored amplitude in the bins matches a stored profile. According to a second aspect of the present invention, there is provided a detection method comprising transmitting microwave energy, receiving a reflected microwave signal, filtering the reflected microwave signal into a set of frequency sub-components, storing the amplitude of the frequency sub- components in a plurality of bins, accessing one or more profiles defining threshold levels for one or more bins, and generating an alarm signal if the stored amplitude in the bins matches a stored profile.

Owing to the invention, it is possible to provide a detector and a detection method that is much more sophisticated and can distinguish between different objects and can provide much more information about the object being detected. By breaking the received reflected microwave signal into frequency sub-components, it is possible to obtain information about different parts of the object being detected, for example. In the case of the detection of a person, for example, different signal sub-components will be received for the person's head, for their torso and for their individual limbs. This can be used to obtain information, for example concerning the identity of the person detected and information about their rate of movement, for example.

The detector can function as an occupancy and activity detection microwave detector, which is a sophisticated movement detector that can detect multiple movements over a distance. Using integrated intelligence and computation mechanisms and processes, the resultant data can be analysed in order to create dynamic and adaptive detection profiles, which can be used to sensitize and de-sensitize the detector. The detector can be used as a standalone device or part of a system. The detector can provide information from and regarding its detection and analysis processes. The detector can be supplied with profile information in order to adjust and control the detection behaviour, analysis processes and power consumption activity. The profile information can be shared as a calibration process or ongoing process, as an ongoing process between the detector and host system, dynamic and adaptive profiling can take place. The microwave motion detection module generates radio frequency (RF) signals. When the signal hits an object, an amount of the signal is reflected. The microwave motion detection module receives the reflected signal. The output signal of the module is relative to the received signal. When an object moves within the range of the RF signal from the microwave module, the reflected signal varies in relation to the movement of the object. When an object, such as a person or animal moves, the output signal from the module is much more complex as each component of the object (head, body, limbs etc.) create individual signal reflections. The variation of the voltage of the output of the module can be analysed as various frequencies and amplitudes.

Sophisticated sample timing, data acquisition and digital filtering are applied to the resultant output from the microwave detector to extract the individual frequencies. The level of detection per frequency is extracted. Each frequency has a location referred to as a bin, which stores the level detected. The number of bins and relation to frequency is subject to the operating parameters selected for the application. Data is sampled as a session and a session comprises of the number of data acquisitions required to populate the bins via the digital filtering process. Historical bin levels may be retained, keeping a history of movement for a number of sessions.

In a preferred embodiment, the detector may be configured to sample data and monitor 128 bins, where each bin relates to a 1 Hz incremental frequency from 1 to 128Hz. The whole data session takes 1 second to sample and process. The digital filtering extracts the frequency levels per bin from the sampled data. Subject to the detected movement, various levels will be present in each bin. Logic is applied with reference to historical data in order to create a trigger condition.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:-

Figure 1 is a schematic diagram of a detector and an object bring detected,

Figure 2 is a schematic diagram of the components of the detector, Figure 3 is a schematic diagram of sub-components of a received signal being stored in bins,

Figure 4 is a schematic diagram of the detector connected to a host system, and

Figure 5 is a flowchart of a method of operating the detector.

Figure 1 illustrates schematically a detector 10 that transmits microwave energy 14 and receives back a reflected microwave signal 16 from an object 26. The detector 10 is able to detect the presence of the object 26 in its field of view. The detector 10 is also able to determine information about the object 26 and information about the identity of the object 26 through the processing of the reflected microwave signal 16. The processing will be described in more detail below, once the individual components of the detector 10 have been described in detail.

The detector 10 comprises various hardware sub circuits, as shown in

Figure 2. The detector 10 is comprised of the following functional hardware sub circuits: a microwave motion sensor module 12, a microwave module power supply and switching circuit 28, a sample and hold circuit 30, an analogue to digital converter and comparator module 32, a microcontroller 18, a power supply 34, a communications interface (wired/wireless) 36 and an LED and tamper detect module 38.

The microwave motion sensor module 12 is a Doppler transceiver module that generates signals in the microwave spectrum. The microwave module receives signals in the microwave spectrum and generates an output signal in relation to the signal. The microwave motion sensor module 12 can have single or multiple outputs. Multiple outputs, for example two outputs, enable direction of travel, multiple target tracking and speed of target movement to be analysed, along with relevant supporting software. Microwave signals of different frequencies are used in order to detect direction and multiple targets.

The microwave module power supply and switching sub circuit 28 controls the power to the microwave module 12 and related power supply rail conditioning. This will be used on most applications, but is optional; the inclusion of this sub circuit allows control of the power consumption of the microwave module 12.

The sample and hold circuit 30 is an optional sub circuit, used to minimise power consumption. When combined with the microwave module power supply and switching sub circuit 28, the microwave module 12 can be powered for a minimal time period and the resultant signal from the microwave module 12 can be sampled and held for use by the microcontroller 18. A sample and hold circuit 30 will be needed per output of the microwave module 12 if a multiple output module 12 is used.

Analogue to digital converter (ADC) and/or comparators 32 will be used to sample the output signal from the microwave module 12 for processing by the firmware in the microcontroller 18. The ADC and comparators used, as required, will preferably be integral to the microcontroller 18, but may also be designed as external devices as required by design and cost constraints. Individual ADC and/or comparators 32 are needed for each output of the microwave module 12.

In order to minimise complexity, increase functionality and design versatility, a microcontroller 18 is used. A microcontroller 18 from any vendor and of suitable speed and capability may be used. The microcontroller 18 carries out and is responsible for the functions described below in more detail. The microcontroller 18 is responsible for the processing of the received microwave energy 16.

The detector 10 may be powered by a battery and/or by an external power supply. In order to ensure the detector 10 is usable and viable as a battery powered device, sophisticated software and hardware functionality is included, such as the microwave power control 28, the sample and hold sub circuit 30, advanced RF functionality and protocols and other software features.

The detector 10 may be a standalone device, with simple relay output indicating detection and/or tamper detection. The detector 10 may have an RF interface 36, allowing communication of detection, alarm and similar conditions. The inclusion of a bi-directional RF interface 36 allows profile information to be exchanged between the detector 10 and any host system 40. The detector 10 may also have a wired interface 36, allowing communication of detection, alarm and similar conditions. The inclusion of a bi-directional wired interface 36 allows the profile information to be exchanged between the detector 10 and any host system 40. LEDs 38 may be included as required for power and status indications and a tamper detection device(s) 38 (i.e. switch) may be also be included as required.

The components of the detector 10 operate various software functions including microwave module power control, sample and hold control, analogue data input (including analogue to digital converter and comparators), signal processing, digital filtering and analysis, profile functions, system timing, power conservation and control, communications, local data and parameter storage, remote firmware update and tamper, low battery and fault detection.

The microwave module power control 28 allows the microcontroller 18 to power and de-power the microwave module 12. The sample and hold control 30 allows the output signal level from the microwave module 12 to be sampled and held for later use, after the microwave module 12 has been de- powered and the primary reason for this is to reduce power consumption. The analogue data from the microwave module 12 or sample/hold circuits 30 is monitored and converted to digital data and/or signals by the analogue to digital converter(s) and/or comparators 32. As mentioned above, the ADC and comparators 32 may be on the microcontroller device 18 or included within the detector 10 as separate devices. The configuration, control, timing and data acquisition is controlled by the microcontroller 18 as needed for processing requirements and power consumption reduction.

In relation to signal processing, the microcontroller 18 controls all configuration, input/output control and data acquisition. The microcontroller 18 processes all data into the device, applying any logic or filtering needed.

Sophisticated sample timing, data acquisition, digital filtering and analysis are applied to the resultant output from the microwave module 12 by the microprocessor 18. Digital filtering is employed to analyse the incoming signal 16 and extract individual frequency components 20 of the signal 16, as shown in Figure 3. Fast Fourier Transform (FFT) is the preferred digital filtering employed, but any other digital filtering and analysis may be used to filter and extract the required signal component from the input signal. Other software filtering such as high pass, low pass and band pass filtering may also be required to process the signal prior to the FFT or similar filtering stage.

The microcontroller 18 is arranged to filter the reflected microwave signal 16 into a set of frequency sub-components 20 and to store the amplitude of the frequency sub-components 20 in a plurality of bins 22. The filtered frequency sub-components 20 preferably represent 1 Hz increments in the reflected microwave signal 16, but this increment magnitude may differ subject to application parameters. The reflected microwave signal 16, sampled for a time interval (preferably one second, but may differ subject to application parameters), is split into the sub-components 20, and each bin 22, where the respective amplitude of each frequency sub-component 20 is stored, relates to 1 Hz incremental frequency from 1 to 128Hz in this preferred embodiment, but actual incremental frequency sub-components 20 and number of bins 22 may differ subject to application parameters. This provides a far more detailed view of the received signal 16 and allows sophisticated processing of the content of the bins 22 to take place.

Detection is determined by utilising logic functions, current session data, historical session data and stored profile parameters. False detections of known frequencies can be eliminated by either ignoring a specific bin or desensitizing the bin by raising the detection level required for that bin in order to create a detection trigger. Essentially, the microcontroller 18 will generate an alarm signal, if specific bin levels match a stored profile. The microcontroller 18 has access to a variety of profiles that define threshold levels for one or more bins 22, and these are accessed by the microcontroller 18 in order to check to see if an alarm condition has been met through an analysis of the bins 22.

A detection would require a number of bins 22 to be triggered to pre-set amplitude levels over a time period (number of sessions) in order to create a detection state, all of these parameters being contained in the profile information. An adaptive and dynamic profile system is created as the detection criteria can be adjusted at any time, taking into account current detection data, historical detection data and external parameters such as time, date, external sensor state (contacts, passive infra red sensors etc.). When integrated with a host system, ongoing changes of the profile parameters and monitoring of the detection session data create a learning process.

This process allows the detector 10 to learn its ambient conditions, reducing the risk of false triggers and increasing detection reliability. Due to the various frequency components contained in the filter result, different objects of speed, size and direction may be detected. For example, the detected frequencies within a data session of a human moving would be different to the detected frequencies of a dog, as each limb and body component will contribute to the detected signal frequency bin levels. This allows the detection of animals, people and any other moving object. As the speed of movements can be detected, elderly and patient activity level may be detected with reference to historical data.

As the person's condition worsens or improves, their level of activity may become an obvious indicator of this. As the detector 10 can detect the level of activity, derived from the multiple frequencies of movements (each detection will contain data relating to body, arm leg movements for example), the general trend in activity level may be detected over a period of time. This information may then be combined with other gathered information from the host system to provide daily activity level monitoring. Figure 4 illustrates the detector 10 in contact with a host system 40, which is storing the profiles 24, to which the detector 10 has constant access.

The acquisition, power control and session sampling require complex and precise timing, controlled by the microcontroller 18. The microcontroller 18 also controls many other system timing events relating to general housekeeping, communications, LED control and power consumption functions. Power conservation and control is an important function for the microcontroller 18. In order to operate the microwave based detector 10 for battery powered operation, significant power consumption features and functions are developed and integrated within the detector 10. The microcontroller 18 has the responsibility of controlling these features and carrying out these functions.

The normal functionality of the detector 10 is to run in a continuous mode, always having historical session data retained for processing. In order to reduce power consumption further, the microwave module 12 can be checked periodically to monitor for activity before conducting a data acquisition session. An external device (such as passive infra-red detector, door contact or similar) or event (message from host system etc) may be used to trigger the periodic check or start a data acquisition session. This will greatly extend battery life but may have an impact on data session history. Session history may need to be rebuilt for the required number of sessions before detection processing can be conducted.

The detector 10 can be switched to lower power modes including periodic checking (as above) and disabled. When the microcontroller is idle there will be no data processing or communications etc. and it will enter a low power mode, only being awoken periodically to run housekeeping and communication tasks, until timed processing events need performing.

In a preferred embodiment, the detector 10 will have integrated RF bi- directional capability. This allows profile and parameter reporting and adjustment via the host system. The RF protocol will support low power operation of the detector. Wired communications may be supported as required. Local data and parameter storage can also be provided with internal memory of the microcontroller 18 being used for data and parameter storage, although an external memory device can be integrated as per the design and cost considerations of the application. Remote firmware upgrade using wired or RF communication can be supported. This will allow the detector 10 to be upgraded for requirements of functionality or software modification as required. The firmware upgrade may also be conducted by connecting a suitable programmer to a connector on the detector 10, if included in the design.

The detector 10 can provide tamper, low battery and fault detection functions. By utilizing the current and session data acquired, the detector 10 may detect tamper conditions such as a blocked or covered sensor. A tamper switch or similar detection device may be included as required. The microcontroller 18 will detect low battery condition (where applicable). The microcontroller 18 is able to detect faults within the detector 10 due to the control and data inputs it may access. As the detector 10 uses motion detection, it is immune to temperature based issues that infrared based detectors suffer, since infrared devices rely on the temperature difference between the environment and target. The detector 0 cannot be fooled by slow movement attempts, as this detector is motion based and historical sessions are retained and used within detection algorithms. Any of the above detections may be reported to the host device 40 or cause a detection trigger.

Figure 5 is a flowchart showing the method of operating the detector 10. The detection method comprises step S1 , transmitting microwave energy 14, step S2 receiving a reflected microwave signal 16, step S3, filtering the reflected microwave signal 16 into a set of frequency sub-components 20, step S4 storing the amplitude of the frequency sub-components 20 in a plurality of bins 22, step S5 accessing one or more profiles 24 defining threshold levels for one or more bins 22, and step S6 generating an alarm signal if the stored amplitude in the bins 22 matches a stored profile 24.

In this way, the detector 10 will transmit a microwave signal 14 that will be reflected by one or more objects 26 in the field of view of the detector 10. These reflections 16 will be received and analysed by the detector 10. The reflected signal 16 is filtered into a plurality of frequency sub-components 20, which are then placed in respective bins 22. In the preferred embodiment, there are a number of bins spaced apart in frequency increments subject to application parameters. The bins 22 each contain the amplitude of the respective frequency sub-component 20, which generally will be of low value for the majority of the bins 22.

The detector 10 compares the amplitudes stored in the bins 22 to one or more stored profiles 24 and generates an alarm signal if there is a match between the stored amplitude in the bins 22 and a stored profile 24 where the number of bins above individual preset amplitude matches or exceeds the profile parameters. For example, a profile 24 may specify three separate bins with individual threshold levels (which could be above or below levels) and should the amplitudes in the bins 22 match or exceed those in the profile, then this will generate an alarm signal. For example, if a profile 24 specifies a threshold level of 20 for bin 50 and a threshold level of 25 for bin 100, and the measured amplitude levels for these bins is 30 for both bins, then a match to this profile 24 has occurred and an alarm is generated.

Claims

1. A detector (10) comprising:

o a microwave module (12) arranged to transmit microwave energy (14) and receive a reflected microwave signal (16), and

o a microcontroller (18) connected to the microwave module (12) and arranged to filter the reflected microwave signal (16) into a set of frequency sub-components (20), to store the amplitude of the frequency sub-components (20) in a plurality of bins (22), to access one or more profiles (24) defining threshold levels for one or more bins (22), and to generate an alarm signal if the stored amplitude in the bins (22) matches a stored profile (24).

2. A detector according to claim 1 , wherein the filtered subcomponents (20) represent 1 Hz increments in the reflected microwave signal (16).

3. A detector according to claim 1 or 2, wherein the microwave module (12) is arranged to vary the frequency of the transmitted microwave energy (14).

4. A detector according to claim 1 , 2 or 3, wherein the microcontroller (18) is further arranged to dynamically adapt a stored profile (24) according to the set of sub-components (20).

5. A detector according to any preceding claim, wherein the microcontroller (18) is further arranged periodically to store the contents of the plurality of bins (22).

6. A detector according to any preceding claim, wherein the microcontroller (18) will generate an alarm signal if the stored amplitude in the bins (22) matches a stored profile (24), if the stored amplitude in the bins (22) exceeds the defined threshold levels in the profile (24).

7. A detector according to any one of claims 1 to 5, wherein the microcontroller (18) will generate an alarm signal if the stored amplitude in the bins (22) matches a stored profile (24), if the stored amplitude in the bins (22) is below the defined threshold levels in the profile (24).

8. A detection method comprising:

o transmitting microwave energy (14),

o receiving a reflected microwave signal (16),

o filtering the reflected microwave signal (16) into a set of frequency sub-components (20),

o storing the amplitude of the frequency sub-components (20) in a plurality of bins (22),

o accessing one or more profiles (24) defining threshold levels for one or more bins (22), and

o generating an alarm signal if the stored amplitude in the bins (22) matches a stored profile (24).

9. A method according to claim 8, wherein the filtered subcomponents (20) represent 1 Hz increments in the reflected microwave signal (16).

10. A method according to claim 8 or 9, and further comprising varying the frequency of the transmitted microwave energy (14).

11. A method according to claim 8, 9 or 10, and further comprising dynamically adapting a stored profile (24) according to the set of subcomponents (20).

12. A method according to any one of claims 8 to 11 , and further comprising periodically storing the contents of the plurality of bins (22).

13. A method according to any one of claims 8 to 12, wherein the generating of an alarm signal if the stored amplitude in the bins (22) matches a stored profile (24), occurs if the stored amplitude in the bins (22) exceeds the defined threshold levels in the profile (24).

14. A method according to any one of claims 8 to 12, wherein the generating of an alarm signal if the stored amplitude in the bins (22) matches a stored profile (24), occurs if the stored amplitude in the bins (22) is below the defined threshold levels in the profile (24).