Communications: directive radio wave systems and devices (e.g. – Radar ew – Detection of surveilance
Utility Patent
1998-08-18
2001-01-02
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Radar ew
Detection of surveilance
C342S013000, C342S195000, C455S227000, C455S229000
Utility Patent
active
06169511
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radar detector for detecting microwave signals transmitted from a microwave generator such as a radar gun which is a device for measuring the running speed of cars.
2. Description of the Related Art
Radar detectors detect microwave signals from a traffic radar, sound an alert, and inform the driver of the strength of the microwave signals and sometimes location of the radar source. Most radar detectors will identify the three common microwave frequencies employed in traffic radars:
X Band: 10.525+/−0.025 GHZ
K Band: 24.150+/−0.100 GHZ
Ka Band: 34.700+/−1.300 GHZ
FIG. 20
indicates a conventional receiving circuit of a radar detector. Micro-strip line
11
connects mixer
51
to an antenna which is not indicated in FIG.
20
. Dielectric resonators (DR)
31
,
32
,
33
in Dielectric resonator oscillators (DRO)
1
,
2
,
3
have a direct electromagnetic coupling to line
11
respectively, with the output of DRO
1
,
2
,
3
being supplied to mixer
51
. DRO
1
,
2
,
3
include field effect transistors (FET)
41
,
42
,
43
as amplifying elements, and lines
15
,
16
,
17
, the outputs of which are coupled to DR
31
,
32
,
33
electromagnetically and generate signals which create different frequencies f
0
,f
1
,f
2
respectively. Filters
21
,
22
,
23
function as band rejection filters, are open stub, and therefore have &lgr;/4 wavelength at frequencies that correspond to those of DROs respectively, and thus prevent the outputs of DROs
31
,
32
,
33
to propagate to the antenna.
However, utilizing DROs creates two problems, of which first is the increasing cost of the radar detector. The second is that the DROs type detector receives undesired signals because DROs inherently requires a wide intermediate frequency range, and thus have an increasing false alarm rate.
Utilizing one VCO as the 1st local oscillator invalidates the familiar method. One possible way is the one achieving a VCO circuit such oscillates over a vast frequency range, which enables each RX band can use a different 1st local frequency range without overlapping. If this work is done, we can treat the method being equivalent to that of DROs. However, such the VCO is not achievable due to the semiconductor performance in our time. Thus a narrow oscillation frequency range is preferable regardless some additional criteria may be required.
SUMMARY OF THE INVENTION
The present invention functions to solve the problems above, and aims to provide a radar detector which is comprised of a voltage controlling oscillator (VCO) instead of DROs, thereby decreasing the cost of radar detector.
The present invention aims to provide a radar detector which can decrease the false alarm rate.
The radar detector according to the present invention comprises an antenna for receiving a radar signal; a voltage controlled oscillator which receives a control signal and generates a signal of a frequency corresponding thereto; a first mixer in which said radar signal is mixed with the output signal of said voltage controlled oscillator; plurality of local oscillators which generate signals with frequencies that are different each other; a second mixer in which the output signal of said first mixer is mixed with one of the output signals of said plurality of local oscillators; a detector which detects said radar signals on the basis of the output of said second mixer; a sweep signal generating section which generates and supplies a sweep signal to said voltage controlled oscillator as said control signal; a memory section which stores pair combination data indicating the relation between the frequency of said voltage controlled oscillator, the frequencies of said local oscillators and the frequency of the received radar signal in advance; and a controlling section which obtains information regarding the frequency of said voltage controlled oscillator and the frequency of said one of the local oscillator from which the output is input to said second mixer when said detector detects a radar signal and decides the frequency of said radar signal by comparing the obtained information with said pair combination data in said memory section.
The radar detector according to the present invention comprises an antenna for receiving radar signals; a receiving section which demodulates the radar signal received by said antenna based on output signals of local oscillators; and a controlling section which, after detecting a radar signal demodulated by said receiving section, decides the received frequency of said radar signal and counts the number of detected signals during a receiving sequence, which is used to recognize the environment of straying signals, and generates an alarm signal on the basis of said number.
The radar detector according to the present invention comprises an antenna for receiving radar signals; a receiving section which demodulates the radar signal received by said antenna based on output signals of local oscillators; a controlling section which, after detecting a radar signal demodulated by said receiving section, decides the received frequency of said radar signal; and a filter circuit at a demodulation port, which reduces demodulated noise for X band and K band and lowers the threshold level so as to maximize sensitivity.
The microwave receiving circuit according to the present invention comprises a first local oscillator which generates a first local signal; a first mixer in which a input signal is mixed with the output signal from said first local oscillator and a signal of a frequency of the difference between the frequencies of the mixed signals is output therefrom; a second local oscillator which generates a second local signal; a second mixer in which a output signal from said first mixer is mixed with the output signal from said second local oscillator and a signal of a frequency of the difference between the frequencies of the mixed signals is output therefrom; and a controlling section which sweeps frequency of said first local oscillator so as to obtain a first receiving result when said second local oscillator oscillates at a first frequency and sweeps frequency of said first local oscillator so as to obtain a second receiving result when said second local oscillator oscillators at a second frequency and decides the frequency of said input signal on the basis of said first receiving result and said second receiving result.
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Iwakuni Mikio
Takiguchi Masahiro
Gregory Bernarr E.
McDermott & Will & Emery
Uniden Corporation
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