Method for software scan conversion of target identification...

Communications: directive radio wave systems and devices (e.g. – With particular circuit – Display

Reexamination Certificate

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C342S195000

Reexamination Certificate

active

06211814

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to high-speed coordinate scan conversion of radar or sonar target identification data coordinates for video presentation and more particularly to programmed software, custom hardware, or combined software and hardware video coordinate conversion. The invention also relates to radar or sonar video distribution and more particularly to a system that allows for the distribution of audio, video and computer data as well as radar or sonar data, via a digital data network. The preferred embodiment of the invention is for radar systems, and the invention is described by reference to such systems herein.
2. Description of the Related Art
Traditional radar video distribution has been implemented with a central analog radar switchboard which accepts inputs from multiple radars, and provides outputs to a number of dedicated radar display consoles. The switchboard used a switch matrix to deliver one selected input radar video signal to each radar display console. Such systems were dedicated to this purpose and generally were large and expensive. Recent developments in very high-speed digital networks make feasible the distribution of digitized radar video over these digital networks, in addition to television video, audio, and computer data.
U.S. Pat. No. 5,923,285 entitled “Low Bandwidth Digital Radar Video Distribution System,” issued Jul. 13, 1999 to Martin J. Andrusiak, et al., describes a system architecture for distribution of digitized radar video on a modern computer network and is hereby incorporated by reference into this document. This system architecture enables software scan conversion within a general purpose computer by eliminating the need for dedicated hardware within the general purpose computer to capture and convert the radar video and azimuth signals from analog to digital form. It also improves the feasibility of software scan conversion within a general purpose computer because it substantially reduces the amount of data that needs to be processed for display.
Scan conversion is the process of converting radar data from a polar coordinate system (range and azimuth) to the Cartesian coordinate system (x, y) required for modern raster displays, typically in plan position indication (PPI) format. The scan converter may also allow the operator to select a unique view of the radar The options for this view include range scale, (the range of radar data represented on the display), and offset, (the relative location of the radar origin on the display). Centered PPI is defined as a PPI display, in which the radar origin is at the center, while offset PPI is defined as a PPI display in which the radar origin is not at the center of the display and may be off the display. While PPI is the most common radar display format, other scan conversion formats, such as range-height indication (RHI), B-Scan and A/R-Scan (amplitude-range) exist and may be implemented with the present invention.
Numerous types of such systems have been developed for providing the conversion of (r,&thgr;) information into (x, y) information. The majority of these have relied on relatively complex hardware-dominated systems for providing the scan conversion In the past, such complex hardware systems were required to achieve the high speed needed to process the information being received from the radar in real-time, U.S. Pat. No. 6,140,955 titled “Ruler Algorithm for PPI Rectangular Radar Scan Converter with Staircase Line Drawing,” filed in the name of Martin 3. Andrusiak, et. al., describes a scan conversion algorithm that is used as the basis for the scan conversion improvements described in this document, and is hereby incorporated by reference into this document.
Modern general purpose computers typically operate under the control of an operating system. Many of these operating systems support multi-tasking which means several programs may appear to operate simultaneously although each is allocated a portion of time for execution. The priority of tasks may also be adjusted to optimize system performance. These types of operating systems provide unpredictable amounts of CPU time to any given task. This presents a problem for processing real-time continuous data requiring some minimum amount of CPU time in order to keep up.
Modern CPUs are getting fast enough that it is often possible to perform scan conversion completely in software. However, the available CPU processing power may limit the display size, resolution and radar data pulse rate and rotation rates which may be achieved by a software scan converter. The unpredictable behavior and time varying loading of multi-tasking operating systems may also further complicate the problem of keeping up with real-time data. The present invention provides software scan conversion on a general purpose computer when the general purpose computer is provided range scaled and window detected digital radar video according to the Andrusiak, et. al., U.S. Pat. No. 5,923,285.
Target data from one or more radar or sonar systems may be mixed to provide multiple and composite images. U.S. Pat. No. 5,036,326 entitled “Method and Device for the Display of Several Radar Images in a Single Mosaic,” issued Jul. 30, 1991 in the names of Jean-Pierre Andrieu, et al., shows a method and device for the display of several radar images in a single mosaic image. The present invention also provides a network-based system that is also capable of providing mosaic images with enhanced flexibility, reduced cost, and optimal display quality.
SUMMARY OF THE INVENTION
A method of displaying real-time input target identification data on a display screen of a digital computer, which may have a non-real time operating system, proceeds by integrating the storage of said target identification data into a polar data buffer memory as the data is received with stored target identification data that was previously received. The data is then extracted from the polar data buffer memory and displayed on a display screen at a rate compatible with the digital computer. The stored target identification data in the polar data buffer memory may be modified by a decay function after it has been presented on the display screen in order to age or fade old target identification data. This decay function may simply decrement the stored target identification data by a predetermined decay value. The polar data buffer memory may also record, during the integration and decay operations, which target identification data has been changed from that most recently displayed. The source of the target identification data may be either radar or sonar systems.
The data may be converted from polar to rectangular, or Cartesian coordinates by an improved software scan conversion program that uses said recorded change information to reduce redundant display update operations. The improved software scan conversion program also detects consecutive polar coordinate data bits which map into the same Cartesian coordinate data bits, and then maps these consecutive polar coordinate data bits into the Cartesian coordinate data bits in a single display update.
The software scan conversion program itself is integrated with a method of converting and displaying radar data that is supplied by one or more analog radar systems, over a digital network, to display systems which include a digital computer executing said software scan conversion program. In this method, the analog radar is digitized, then range compression is applied to the digitized video data followed by window detection to provide digital range compressed, window detected video data. The digital range compressed, window detected video data is then transmitted over a digital network to the display systems. Control signals from the display systems select the images to be displayed.


REFERENCES:
patent: 5036326 (1991-07-01), Andrieu et al.
patent: 5315305 (1994-05-01), Noll
patent: 5923285 (1999-07-01), Andrusiak et al.
patent: 6140955 (2000-10-01), Andrusiak et al.

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