PPI radar apparatus
First Claim
1. A PPI radar apparatus for displaying an image of a target on a CRT screen by PPI sweep of an electron beam, comprising:
- an A/D converting means for converting a video signal received by a radar antenna into a digital video signal;
a distance range selecting means having switchover ranges of at least short distance ranges, middle distance ranges, and long distance ranges of generation period of a transmission pulse signal, for selecting a distance range of the target image to be displayed on said CRT screen;
a plurality of storing means each for writing therein and reading out therefrom said digital video signal which is outputted from said A/D converting means, in synchronism with said transmission pulse signal;
a transmission/reception control means for switching over a transmission/reception time cycle Tt of a transmission pulse relative to a constant sweep display time cycle Ts into a transmission/reception time cycle Tt=Ts/N obtained by dividing the sweep display time cycle Ts by an integer N in selection of said short distance ranges, into a transmission/reception time cycle Tt=Ts in selection of said middle distance ranges, or into a transmission/reception time cycle Tt=M. Ts obtained by multiplying the sweep display time cycle Ts with an integer M in selection of said long distance ranges;
a write/readout control means for selecting a predetermined number of storing means from among said plurality of storing means in accordance with a distance range selected from the short, middle, and long distance ranges by said distance range selecting means, allowing said predetermined number of storing means to successively write therein the digital video signals repeatedly obtained every transmission/reception time cycle and in parallel with the successive writing operations, and allowing said predetermined number of storing means to read out, in synchronism with said sweep display time cycle and said transmission pulse signal, the digital video signal which have been written in the storing means at least one time cycle before the present transmission/reception time cycle in which one of said predetermined number of storing means is writing a digital video signal therein; and
a displaying means for displaying on said CRT screen an anlog signal into which the digital video signal outputted from one of said predetermined number of storing means by said write/readout control means is converted.
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Accused Products
Abstract
A PPI radar apparatus is constructed such that even when a transmission time cycle of radio waves is varied by switchover of a distance range to any of short, middle and long distance ranges, a sweep display time cycle of a radar video signal received in any of the distance ranges is maintained constant at all times; the sweep display time cycle is determined to meet the middle distance ranges, in the short distance ranges in which the reception time of radio waves is short, the video signals are written in storage means in real-time and then displayed by readout of the video signals at a low speed in synchronism with the sweep time cycle, in the long distance ranges in which the reception time of radio waves is long, the video signals are written in storage means in real-time and then displayed by a number of readouts in one sweep display time cycle; and the video signals written in a plurality of storage means are parallelly read out and a mean value or peak of the read-out video signals is obtained by arithmetic operation to thereby enhance the signal-to-noise ratio of the radar image.
11 Citations
9 Claims
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1. A PPI radar apparatus for displaying an image of a target on a CRT screen by PPI sweep of an electron beam, comprising:
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an A/D converting means for converting a video signal received by a radar antenna into a digital video signal; a distance range selecting means having switchover ranges of at least short distance ranges, middle distance ranges, and long distance ranges of generation period of a transmission pulse signal, for selecting a distance range of the target image to be displayed on said CRT screen; a plurality of storing means each for writing therein and reading out therefrom said digital video signal which is outputted from said A/D converting means, in synchronism with said transmission pulse signal; a transmission/reception control means for switching over a transmission/reception time cycle Tt of a transmission pulse relative to a constant sweep display time cycle Ts into a transmission/reception time cycle Tt=Ts/N obtained by dividing the sweep display time cycle Ts by an integer N in selection of said short distance ranges, into a transmission/reception time cycle Tt=Ts in selection of said middle distance ranges, or into a transmission/reception time cycle Tt=M. Ts obtained by multiplying the sweep display time cycle Ts with an integer M in selection of said long distance ranges; a write/readout control means for selecting a predetermined number of storing means from among said plurality of storing means in accordance with a distance range selected from the short, middle, and long distance ranges by said distance range selecting means, allowing said predetermined number of storing means to successively write therein the digital video signals repeatedly obtained every transmission/reception time cycle and in parallel with the successive writing operations, and allowing said predetermined number of storing means to read out, in synchronism with said sweep display time cycle and said transmission pulse signal, the digital video signal which have been written in the storing means at least one time cycle before the present transmission/reception time cycle in which one of said predetermined number of storing means is writing a digital video signal therein; and a displaying means for displaying on said CRT screen an anlog signal into which the digital video signal outputted from one of said predetermined number of storing means by said write/readout control means is converted. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification