Communications: directive radio wave systems and devices (e.g. – Radar ew – Detection of surveilance
Reexamination Certificate
1999-11-15
2001-01-16
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Radar ew
Detection of surveilance
C342S089000, C342S195000, C455S227000, C455S315000
Reexamination Certificate
active
06175325
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microwave detector, and in particular relates to a wideband microwave detector capable of detecting microwaves in a plurality of different bands.
2. Description of the Prior Art
In general, prior art microwave detectors are equipped with a reception system in which microwaves are picked up or detected by an antenna and mixed with the output of a local oscillator which carries out a sweep over a prescribed sweep frequency to create an intermediate frequency signal that then undergoes amplification and wave detection.
Further, in the case where the detection target microwaves are present in a plurality of bands, the microwave detector needs to be able to carry out multi-band and wide-band operations. In such case, the number of reception systems connected to the antenna in the prior art microwave detector is increased to match the number of microwave frequency bands requiring detection. In other words, a reception system is established for each detection target band, and each of such plurality of reception systems is constructed from a local oscillator that oscillates at a prescribed frequency in accordance with a corresponding detection target band, and an intermediate frequency amplifier established in a pass frequency band in accordance with the corresponding detection target band.
Further, such plurality of reception systems is connected to the antenna in a parallel arrangement, and a selection means (e.g., a selector switch) is provided to alternatively select any one of the reception systems. With this structure, by using the selection means to select one reception system at a time in a sequential manner, it becomes possible to detect microwave signals present in a plurality of detection target bands.
However, the prior art microwave detector which is capable of multi-band and wide-band operations described above has the following problem. Namely, because each detection target band is sequentially selected one at a time to undergo a detection process, a relatively large amount of time is required to search all the detection target bands. In particular, this problem gets worse as the number of detection target bands is increased.
Further, in the case where the microwave detector is mounted in a motor vehicle (e.g., a car or a motorcycle) to detect microwave signals emitted from a radar type speed measurement device, because the vehicle will travel a relatively long distance during the time it takes to search all the detection target bands, there is the risk that the vehicle will reach a position near the radar type speed measurement device before detection of such microwave signals.
Furthermore, in the case where the microwave detector operates intermittently to conserve electricity, because an even greater amount of time will be required to search all the detection target bands, the problem described above (i.e., a long response time) is made worse. Further, if the suspension time is reduced in an attempt to alleviate such problem, the power conserving effect of such a microwave detector will be degraded.
SUMMARY OF THE INVENTION
In view of the background presented above, it is an object of the present invention to solve the problems of the prior art described above by providing a microwave detector which can carry out multi-band and wide-band operations with minimal power consumption without loss of detection sensitivity and detection accuracy.
In order to achieve the object stated above, the multi-band microwave detector according to the present invention is equipped with an antenna, a plurality of reception systems connected to the antenna in a parallel arrangement, judgement means for judging whether or not a microwave signal detected by the reception systems is a detection target microwave signal, and alarm means for outputting an alarm when the judgement means judges the detected microwave signal to be a detection target microwave signal, wherein each reception system is constructed from a superheterodyne reception circuit having a prescribed intermediate frequency that is mutually different from the intermediate frequencies of all the other reception systems, and wherein all the reception systems are operated simultaneously during one detection cycle.
In such a structure, even if the microwave detection bands are widened and the number of such microwave detection bands is increased, a detection target microwave signal included in the microwaves received by the antenna will be detected by at least one of the reception systems. Accordingly, in contrast with the prior art in which a plurality of reception systems are operated one at a time for each respective detection band, in the multi-band microwave detector according to the present invention, if a detection target microwave signal is included in the microwaves received by the antenna, such detection target microwave signal will be detected during a single search by one of the reception systems. In other words, even if the microwave detection bands are widened and the number of such microwave detection bands is increased, there will be no increase in the time required to carry out a single search.
Preferably, the multi-band microwave detector according to the present invention includes control means for controlling the operation and suspension of operation of each reception system.
Accordingly, by controlling the operations of all the reception systems, it is possible to search all the bands (frequency ranges) in a short time (i.e., in a single search), and by individually controlling each reception system, it is possible to determine which reception system received a microwave signal, and thereby determine the band of the microwave signal.
Further, in the multi-band microwave detector according to the present invention, the control means preferably operates all the reception systems when no detection target microwave signal is detected, and operates only one reception system when the judgement means judges a detection target microwave signal to have been detected, and preferably the judgement means carries out a further judgement to determine whether or not a detection target microwave signal is detected by the one reception system.
In the structure described above, during the time that no detection target microwave signal is detected, all the reception systems are operated to make it possible to judge the presence or absence of a detection target microwave signal in all the search bands within a short time interval. Then, when a detection target microwave signal is detected, the judgement means can be used to judge the presence or absence of the detection target microwave signal in the one reception system chosen for operation. Accordingly, it becomes possible to identify the reception system that received the detection target microwave signal.
In this way, an alarm can be outputted in accordance with the identified reception band and emission source. Further, if a search is carried out with special attention made to the detected band, it is possible to improve the detection accuracy.
Further, the multi-band microwave detector according to the present invention is preferably equipped with a first local oscillator and mixing means (i.e., the first mixer
5
in the embodiment of the present invention) for mixing the output of the first local oscillator with the reception signals of the antenna, and the first local oscillator and the mixing means are preferably used by each reception system.
In this way, such common use of elements makes it possible to design a compact multi-band microwave detector which is easy to control. Further, by making the first local oscillator capable of oscillating at both a fixed frequency and over a sweep range, it becomes possible to detect reverse detectors and the like, and for reason the first local oscillator is preferably arranged to have these two oscillation modes. Further, a second intermediate frequency amplifier is preferably provided to be used in common by the plurality of reception syst
Gregory Bernarr E.
Marger & Johnson & McCollom, P.C.
Yupiteru Industries Co., Ltd.
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