Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Distributive type parameters
Reexamination Certificate
1998-06-02
2001-11-06
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Distributive type parameters
C342S028000, C342S027000, C119S721000
Reexamination Certificate
active
06313643
ABSTRACT:
FIELD OF THE INVENTION
THIS INVENTION relates to pest detection by transmitting a microwave signal into a part of a building or other structure for example a wall, floor or ceiling and processing reflections or modulations of the microwave signal to provide a signal indicative of the presence of a pest.
BACKGROUND TO THE INVENTION
Timber eating termites cause damage to property such as buildings. There are numerous ways of killing such pests, however, it is not always easy to detect their presence. As a result, a building structure can be severely damaged by these pests before they are detected. The invention is directed to detecting pests such as termites or other insects, preferably before they cause appreciable damage.
The problem of detecting termites has been addressed in the past but without success. Reference may be had to U. S. Pat. No. 5,285,668 in the name of Robbins and Mueller that describes a system for detecting wood-destroying insects by sensing acoustic emissions generated by the insects as they feed. The major shortcoming of this approach is that termites are not always feeding. The inventors have found that termites may use extensive galleries to move between a feeding region and a nest. The system disclosed in U.S. Pat. No. 5,285,668 will not detect the termites in the galleries. Furthermore, acoustic techniques are prone to spurious signals due to ambient noise.
It is known to use microwaves to kill termites and other insects. This can be hazardous due to the relatively large amounts of high frequency power required to be transmitted in order to kill such insects. Furthermore, the microwaves are generally only used once the insects are detected which may be after the insects have inflicted large and noticeable amounts of damage to the building.
OBJECT OF THE INVENTION
It is an object of the present invention to provide a method and system for detecting pests, such as termites, by the use of microwaves.
Further objects will be evident from the following description.
DISCLOSURE OF THE INVENTION
In one form, although it need not be the only or indeed the broadest form, the invention resides in a method of detecting insects in a structure including the steps of:
transmitting a near field microwave signal into a part of the structure;
receiving a receive signal dependent on the near field signal; and
processing the receive signal to provide an output signal indicative of the presence of the insects in the near field microwave signal.
In preference the step of transmitting a near field microwave signal involves transmitting a modulated signal. The modulation may be in amplitude, frequency or phase and is suitably in the audio range.
Preferably, the step of transmitting is further characterised by the near field microwave signal being less than 2 meters from a transmitter transmitting said signal. More preferably, the signal is less than 1 meter from the transmitter. Most preferably the transmitter is closely adjacent or abutting said part of the building, thereby the near field microwave signal is less than ½ meter from the transmitter. The step of transmitting may be further characterised by the near field signal being normal to said part of the structure.
Suitably, the near field microwave signal is circular polarized.
The receive signal is preferably a reflected signal.
Preferably, the method is further characterised by the steps of transmitting and receiving being effected by a common antenna. Suitably the antenna may be monostatic or bistatic. The antenna may be a horn, apertured printed circuit board, dish, or any other suitable antenna.
Suitably, in one aspect, the step of receiving includes the step of mixing the signal dependent on the near field signal with a reference signal to provide a receive signal which is a combined signal.
Suitably the combined signal comprises a beat frequency signal component.
The step of receiving a receive signal may involve receiving a signal synchronous with the modulation frequency of the transmitted signal.
Preferably, the step of processing may also include the steps of filtering and amplifying the receive signal. Filtering and amplifying may suitably maximise the beat frequency signal component.
Preferably, the step of filtering is characterised by the filtering being effected by a low pass filter having a cut-off frequency of less than 50 HZ. More preferably, the cut off frequency is less than 20 HZ and most preferably 10 HZ or less.
A band pass filter may suitably be used for the step of filtering in which the upper cut-off frequency may be any one of the above described values and the lower cut-off frequency being approximately 0.01 HZ.
In a further aspect of the invention the step of processing further includes the steps of digitizing and analysing the receive signal to provide said output signal or output data indicative of the presence of said insects in said near field microwave signal.
In a yet further form, the step of analysing may include analysis of spectral characteristics of the receive signal.
Suitably, said analysis of spectral characteristics includes Fourier transformation.
The step of processing the receive signal alternatively includes adaptive recognition of termite indicative signals. The adaptive recognition may suitably be performed in a neural network. A hidden Markov chain processor and/or a Kalman filter may suitably be employed at the input to the neural network to enhance the signal to noise ratio of the signal input to the neural network.
In a further form, the invention resides in a system for detecting insects in a structure, the system comprising:
signal generator means operatively coupled to transmitter means to thereby transmit a microwave signal into a part of a structure;
receiver means for receiving signals indicative of the presence or otherwise of insects in a near field of the microwave signal; and
processor means for processing the received signal to provide an output signal indicating the presence or otherwise of insects.
The signal generator means is preferably a microwave generator means. A Gunn oscillator is a suitable signal generator means.
Preferably, said transmitter means is adapted to transmit a circular polarized field. The transmitter means preferably comprises a transmitting antenna which may be a horn, apertured printed circuit board, dish, or other suitable antenna.
The receiver means preferably comprises a receiving antenna which may suitably be the same as the transmitting antenna.
In preference the system further comprises modulator means operatively coupled to the signal generator means for modulating the transmitted microwave signal at a selected frequency.
The receiver means may suitably comprise a synchronous rectifier for locking on receive signals synchronous with the modulated transmitted microwave signal.
The receiver means further comprise mixing means operatively coupled to the receiving antenna and the signal generator means, said mixing means providing a receive signal dependent upon an indicative signal received from said receiving antenna and a reference signal from said signal generator. The receive signal is a combined signal.
In one form, the processor means includes filter means for filtering said combined signal, wherein said combined signal comprises a beat frequency component.
The filter means is suitably adapted to reject frequencies other than frequencies indicative of the presence of insects in the near field, such insects typically being termites.
Preferably, the filter means is a low pass filter having a cut-off frequency of less than 50 HZ. More preferably, less than 20 HZ and most preferably 10 HZ or less.
The filter means may be a band pass filter in which the upper cut-off frequency may be any one of the above frequencies and the lower cut-off frequency may be approximately 0.01 HZ.
The processor means may include amplification means for amplifying the combined signal which may be filtered by said filter means.
The processor means may suitably include digitizing means operatively coupled to a microprocessor for providing s
Davies Robert James
Sanderson Gregory John
Tirkel Anatol Zygmunt
Christie Parker & Hale LLP
Deb Anjan K
J.I. Peston Pty. Ltd.
Metjahic Safet
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