Police traffic radar using double balanced mixer for even order harmonic suppression
DCFirst Claim
1. An antenna for a traffic surveillance radar, comprising:
- a microwave horn for emitting a directional microwave energy beam in a direction said microwave horn is pointed, and for receiving microwave energy reflected from objects in the path of said beam;
an oscillator for generating a microwave signal;
a double balanced mixer means for mixing a portion of the microwave energy from said oscillator with reflected microwave energy received by said microwave horn;
energy guidance means for guiding microwave energy from said oscillator to said microwave horn and for guiding received microwave energy and a sample portion of said energy from said oscillator to said double balanced mixer means while preventing most of said energy from said oscillator from being coupled to said double balanced mixer means and while preventing said received microwave energy from being coupled to said oscillator.
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Abstract
A police radar utilizing digital data transmission from the antenna unit to a separately housed counting and display unit. The antenna has a double balanced mixer to suppress even order harmonics. The counting and display unit has a computer programmed to perform digital signal processing on the digital data received from the antenna to improve the quality and accuracy of calculated speeds for patrol speed, strongest target speed and fastest target speed. Fastest target speed can be displayed simultaneously with strongest target speed. Signal processing techniques are used to suppress false signals caused by double and triple bounce, harmonics, intermodulation products, video display terminal interference, etc.
79 Citations
13 Claims
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1. An antenna for a traffic surveillance radar, comprising:
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a microwave horn for emitting a directional microwave energy beam in a direction said microwave horn is pointed, and for receiving microwave energy reflected from objects in the path of said beam; an oscillator for generating a microwave signal; a double balanced mixer means for mixing a portion of the microwave energy from said oscillator with reflected microwave energy received by said microwave horn; energy guidance means for guiding microwave energy from said oscillator to said microwave horn and for guiding received microwave energy and a sample portion of said energy from said oscillator to said double balanced mixer means while preventing most of said energy from said oscillator from being coupled to said double balanced mixer means and while preventing said received microwave energy from being coupled to said oscillator. - View Dependent Claims (2, 3)
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4. A police radar, comprising:
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an antenna unit comprising; a microwave horn for emitting a directional radar energy beam in a direction said microwave horn is pointed, and for receiving radar energy reflected from objects in the path of said beam; an oscillator for generating a radar signal; a double balanced mixer means for mixing a portion of the radar signal energy from said oscillator with reflected radar energy received by said microwave horn; energy guidance means for guiding radar signal energy from said oscillator to said microwave horn and for guiding received radar energy and a sample portion of said energy from said oscillator to said double balanced mixer means while preventing most of said energy from said oscillator from being coupled to said double balanced mixer means and while preventing said received radar energy from being coupled to said oscillator; a processing and display unit for receiving signals from said double balanced mixer means and calculating and selectively displaying a patrol speed representing the speed of a patrol car in which said police radar is supported, and calculating and selectively displaying a strongest target speed representing the speed of a moving target having the strongest reflected radar energy; and a signal path coupling signals from said mixer means to said processing and display unit. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12)
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13. A police radar, comprising:
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an antenna unit comprising; a microwave horn for emitting a directional radar energy beam in a direction said microwave horn is pointed, and for receiving radar energy reflected from objects in the path of said beam; an oscillator for generating a radar signal; a double balanced mixer means for mixing a portion of the radar signal energy from said oscillator with reflected radar energy received by said microwave horn; energy guidance means for guiding radar signal energy from said oscillator to said microwave horn and for guiding received radar energy and a sample portion of said energy from said oscillator to said double balanced mixer means while preventing most of said energy from said oscillator from being coupled to said double balanced mixer means and while preventing said received radar energy from being coupled to said oscillator; a processing and display unit for receiving signals from said double balanced mixer means and calculating and selectively displaying a patrol speed representing the speed of a patrol car in which said police radar is supported, and calculating and selectively displaying a strongest target speed representing the speed of a moving target having the strongest reflected radar energy; analog-to-digital converter and transmission means for converting analog signals from said mixer means to digital data and transmitting said digital data to said processing and display unit; a digital signal path coupling digital data from said analog-to-digital converter and transmission means to said processing and display unit; an amplifier in said antenna unit having a variable gain set by a gain control signal received at a gain control input said amplifier for amplifying signals from said mixer means, and further comprising automatic gain control circuitry for adjusting the gain of said amplifier to keep the amplitude of the output of said amplifier within acceptable upper and lower limits and for reporting the gain level for any signal generated by said mixer means to said processing and display unit, and wherein said processing and display unit includes means for calculating and displaying the speed of the fastest moving target having a reflected radar signal having certain attributes, and for using the gain level at which any signal from said mixer means was amplified to calculate true power of the corresponding received signal(s), and for using said true power information for improving the process of selection of signals for calculation of said patrol speed and said strongest target speed and said fastest target speed by imposing first predetermined selection criteria on signal candidates from which a signal will be selected to calculate said patrol speed, and for imposing second predetermined selection criteria on signal candidates from which a signal will be selected to calculate said strongest target speed, and for imposing third predetermined selection criteria on signal candidates from which a signal will be selected to calculate said fastest target speed, thereby substantially reducing the possibility that a weak signal will be selected for patrol speed processing or that the signal from which said strongest target speed is calculated is a harmonic of the signal from which patrol speed is calculated, or that the signal from which said fastest speed is to be calculated is a false signal resulting from harmonics of the signal from which said patrol speed was calculated or harmonics of other strong signals in said spectrum or from intermodulation products of strong signals in said spectrum.
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Specification