US 4,307,396 A · Microprocessor controlled PPI sweep generator with automatic distribution of real-time video and synthetic display loads

Abstract

An improved method and apparatus for controlling the display of a plan position indicator radar display are disclosed which result in the elimination of both display flicker and the loss of critical real-time radar return data. The system is clocked by a series of fixed pulses related to the length of the radar beam on the display. Creation of the radar beam is given top system priority. Thereafter, the number of clock pulses allocated for radar beam creation is diminished as necessary to provide time for the display of prestored synthetic display data. The time is taken from a portion of each beam which has been preselected as least critical. Additionally, the beam length based clock pulses are employed to compensate for sweep overlap and in such functions as offset, range scale, and sweep off-scale.

Claims13

Dependent claims

In a radar plan position indicator display wherein data and real-time radar return beams rotating about an origin are displayed by display control circuitry on a time-shared basis, the method of controlling the display creation to prevent both display flicker and lost critical real-time data comprising the steps of:

(a) selecting the portion of the radar return closest to the origin of the actual radar beam as being either "most critical" or "least critical";
(b) dividing the time to create the entire real-time radar beam length on the display into a fixed number (L) of equal clock pulses;
(c) initially allocating the creation of each radar beam on the display a time of said fixed number L of said clock pulses on a priority basis in which to create the radar beam display;
(d) using only the time not employed in creating the real-time radar beams displayed to create the synthetic data on the display;
(e) testing the amount of time required for creating the synthetic data on the display against the time remaining following that allocated for creation of the radar beams on the display and, if sufficient, to allow creation of the synthetic data at a refresh rate above that required to prevent flicker, leaving the time in number of clock pulses allocated to create the radar beam on the display at its presently set value and continuing to step (g), otherwise continuing on to step (f);
(f) when the refresh rate of synthetic data is low enough to cause flicker, reducing the time in number of clock pulses allocated to create the real-time radar beams by a number which represents the added time necessary to refresh the synthetic data on the display at a nonflickering rate, the time being taken at the origin, or at the beam-end end of the radar beams selected directly or indirectly in step (a) as "least critical";
and,
(g) repeating steps (a)-(f) as necessary in response to changes in designated system conditions.

5 more elements

In a radar plan position indicator display having a radar range clock and having a display screen and display logic time-synchronized to a radar beam for creating a light beam on the display screen of a cathode ray tube indicating a portion of the radar beam between the origin and maximum range preselected by a range switch, the improvement comprising:

a deflection clock circuit connected to provide the time synchronization of the display logic as a function of clock pulses each representing a fixed deflection distance along the beam on the display screen regardless of the maximum range value selected.

In a radar plan position indicator display having a cathode ray tube and having recording logic time synchronized to a radar beam for recording the intensity of the video within a desired display area along the radar beam between the origin and a maximum range preselected by a range switch, and wherein the light beam on the display rotates about the origin in synchronization with a rotating radar causing beam overlap to occur adjacent the origin, the cathode ray tube having a sweep unblank line and a video line, the improvement comprising:

(a) a clock circuit connected to provide the time synchronization of the logic as a function of clock pulses each representing a fixed distance along the beam of the video record regardless of the maximum range value selected,
(b) means for generating a composite correction voltage being the summation of a range rate correction voltage and a digital overlap correction voltage;
(c) a first variable gain voltage amplifier, having a control input, connected in series with the sweep upblank line of the cathode ray tube;
(d) a second variable gain voltage amplifier, having a control input, connected in series with the video line of the cathode ray tube;
and
(e) means for connecting said correction voltage to said control inputs of said voltage amplifiers to maintain a flat field intensity pattern.

3 more elements

Dependencies are inferred from the claim text.

Microprocessor controlled PPI sweep generator with automatic distribution of real-time video and synthetic display loads

Life of this patent

Microprocessor controlled PPI sweep generator with automatic distribution of real-time video and synthetic display loads

Life of this patent

Abstract

Claims13