Radar device, similar device, and received data write method

A radar and like apparatus, comprising:

• a video memory for successively performing coordinate conversions on received data from a polar coordinate system to a rectangular Cartesian coordinate system along with sweep rotation and storing the converted data;
• a subtractor for subtracting a constant value from pixel data of an area set on the video memory in parallel with data write accompanied by the coordinate conversion;
• and
• a LAST detector for detecting, as a LAST access, when a pixel of the video memory is accessed for the last time in performing the coordinate conversion during one sweep rotation, wherein the subtractor performs a subtraction at a time other than the LAST detection.

A method for writing received data into a memory comprising:

• a step for successively performing a coordinate conversion on received data from a polar coordinate system to a rectangular Cartesian coordinate system and storing the converted data into as video memory at each sweep rotation with the data being updated;
• a subtraction step for subtracting a constant value from pixel data of an area set on the video memory in parallel with data write accompanied by the coordinate conversion, wherein data in the area is successively subtracted during one sweep rotation;
• and
• a FIRST detection step for detecting, as a FIRST access, when a pixel of the video memory is accessed for a first time in performing the coordinate conversion during one sweep rotation,
• wherein in the subtraction step, a subtraction is performed at a time other than the FIRST detection.

A radar and like apparatus, comprising:

• a primary memory for temporarily storing received data;
• a video memory for successively storing the data stored in the primary memory;
• a display unit for displaying the data stored in the video memory;
• a coordinate converter circuit for performing a coordinate conversion to convert a polar coordinate position of received data into a rectangular Cartesian coordinate address of the video memory;
• a FIRST detector circuit for detecting, as a FIRST access, an access that a pixel of the video memory is accessed for a first time at the coordinate conversion during one sweep rotation, wherein the subtractor performs a subtraction at a time other than the FIRST detection;
• a subtraction area address generator circuit for setting an area on the video memory as a subtraction area and successively generating addresses of this area;
• a subtraction data generator circuit for generating, as subtraction data, data resulting from subtracting a constant value from pixel data in the subtraction area;
• and
• a selector for, at the FIRST detection, selecting a rectangular-coordinate address derived from the coordinate converter as an address for the video memory and further selecting data of the primary memory as write data to be written into the video memory, and for, at a time other than the FIRST detection, selecting an address derived from the subtraction area address generator as an address of the video memory and further selecting subtraction data generated by the subtraction data generator as write data to be written into the video memory.