Coordinate converter using multiplying digital-to-analog converters

Claim 2

A multiplying digital to analogue converter, comprising: means for receiving an analogue input; means for receiving a digital input in two''s complement form; means for generating a first analogue output which is alternatively zero or iNdicative of said analogue input, depending upon the most significant bit of said digital input; and means for generating a second analogue output indicative of the product of said analogue input and the quantity represented by the remainder of the bits of said digital input.

Claim 3

A multiplying digital to analogue converter in accordance with claim 1 in which the means for generating the first analogue output includes a switch connected to said analogue input and operated in response to the most significant bit of said digital input.

Claim 4

each converter being for generating a first voltage output which is alternatively zero or indicative of the analogue input depending upon the most significant bit in said digital input; and

Claim 5

each converter being for generating a first voltage output which is alternatively zero or indicative of the analogue input depending upon the most significant bit in said digital input; and

Claim 6

each converter being for generating a second voltage output indicative of the product of said analogue input and the quantity represented by the remainder of the bits of said digital input; B. means for applying the negative of an analogue voltage indicative of x to said first and third converters and applying the negative of an analogue voltage indicative of y to said second and fourth converters; C. means for applying a digital quantity in two''s complement form indicative of the cosine of theta to said first and fourth converters and for applying a digital quantity in two''s complement form indicative of the sine of theta to said second and third converters, D. means for summing saId First output of said first converter, said second output of said second converter, the negative of said second output of said first converter and the negative of said first output of said second converter, whereby a voltage indicative of the new x coordinate is obtained, and E. means for summing said first output of said third converter, said first output of said fourth converter, the negative of said second output of said third converter and the negative of said second output of said fourth converter whereby a voltage indicative of the new y coordinate is obtained.

Claim 7

each converter being for generating a second voltage output indicative of the product of said analogue input and the quantity represented by the remainder of the bits of said digital input; B. means for applying the negative of an analogue voltage indicative of x to said first and third converters and applying the negative of an analogue voltage indicative of y to said second and fourth converters; C. means for applying a digital quantity in two''s complement form indicative of the cosine of theta to said first and fourth converters and for applying a digital quantity in two''s complement form indicative of the sine of theta to said second and third converters, D. means for summing saId First output of said first converter, said second output of said second converter, the negative of said second output of said first converter and the negative of said first output of said second converter, whereby a voltage indicative of the new x coordinate is obtained, and E. means for summing said first output of said third converter, said first output of said fourth converter, the negative of said second output of said third converter and the negative of said second output of said fourth converter whereby a voltage indicative of the new y coordinate is obtained.

Claim 8

A multiplying digital to analogue converter in accordance with claim 2 in which the means for generating the second analogue output includes an output line, a plurality of resistors and a plurality of switches, each of said switches being operated in response to one of the remaining bits of said digital input and each arranged to selectively connect one of said resistors between said analogue input and said output line.

Claim 9

Apparatus for deriving a unidirectional voltage the magnitude and sign of which are indicative of the function x cos theta -y sin theta where x and y are available as unidirectional analogue voltage inputs indicative thereof and sin theta and cos theta are available as binary digital quantities in two''s complement form indicative thereof, comprising: first and second multiplying digital to analogue converters, each for receiving one of said analogue voltage inputs and one of said digital quantities, each for generating a first analogue output voltage which is alternatively zero or indicative of the analogue voltage applied thereto, depending upon the most significant bit of the digital quantity applied thereto, and each for generating a second analogue output voltage indicative of the product of the applied analogue input and the quantity represented by the remainder of the bits of the applied digital quantity; means for applying the negative of said voltage indicative of x and said quantity indicative of cos theta to said first multiplying digital to analogue converter; means for applying the negative of said voltage indicative of y and said quantity indicative of sin theta to said second multiplying digital to analogue converter; and means for summing said first output voltage of said first converter, said second output voltage of said second converter, the negative of said second output voltage of said first converter and the negative of said first output voltage of said second converter, whereby the resulting voltage is indicative of the function x cos theta -y sin theta .

Claim 10

Apparatus for deriving a unidirectional voltage the magnitude and sign of which are indicative of the function x cos theta -y sin theta where x and y are available as unidirectional analogue voltage inputs indicative thereof and sin theta and cos theta are available as binary digital quantities in two''s complement form indicative thereof, comprising: first and second multiplying digital to analogue converters, each for receiving one of said analogue voltage inputs and one of said digital quantities, each for generating a first analogue output voltage which is alternatively zero or indicative of the analogue voltage applied thereto, depending upon the most significant bit of the digital quantity applied thereto, and each for generating a second analogue output voltage indicative of the product of the applied analogue input and the quantity represented by the remainder of the bits of the applied digital quantity; means for applying the negative of said voltage indicative of x and said quantity indicative of cos theta to said first multiplying digital to analogue converter; means for applying the negative of said voltage indicative of y and said quantity indicative of sin theta to said second multiplying digital to analogue converter; and means for summing said first output voltage of said first converter, said second output voltage of said second converter, the negative of said second output voltage of said first converter and the negative of said first output voltage of said second converter, whereby the resulting voltage is indicative of the function x cos theta -y sin theta .

Claim 11

Apparatus for deriving voltages indicative of the rectangular coordinates of a point which has been rotated about the origin through an angle theta from an initial point having coordinates x, y, comprising: A. First, second, third and fourth multiplying digital to analogue converters,

Claim 12

Apparatus for deriving voltages indicative of the rectangular coordinates of a point which has been rotated about the origin through an angle theta from an initial point having coordinates x, y, comprising: A. First, second, third and fourth multiplying digital to analogue converters,

Claim 13

A coordinate converter, comprising, first and second multiplying digital to analogue converters, each including: means for receiving an analogue input; means for receiving a digital input in two''s complement form; means for generating a first analogue output voltage which is alternatively zero or indicative of said analogue input, depending upon the most significant bit of said digital input; means for generating a second analogue output voltage indicative of the product of said analogue input and the absolute value of said digital input; means for applying analogue inputs indicative of the negative of the abscissa and the negative of the ordinate of a point to said first and second converters, respectively; means for applying digital inputs indicative of the sine and cosine of an angle through which said point is to be rotated to said first and second converters, respectively; and means for summing; said first output of said first converter; said first output of said second converter; the negative of said second output of said first converter; the negative of said second output of said second converter; and whereby the sum is an analogue quantity indicative of the new ordinate of said point after rotation through said angle.

Claim 14

A coordinate converter, comprising, first and second multiplying digital to analogue converters, each including: means for receiving an analogue input; means for receiving a digital input in two''s complement form; means for generating a first analogue output voltage which is alternatively zero or indicative of said analogue input, depending upon the most significant bit of said digital input; means for generating a second analogue output voltage indicative of the product of said analogue input and the absolute value of said digital input; means for applying analogue inputs indicative of the negative of the abscissa and the negative of the ordinate of a point to said first and second converters, respectively; means for applying digital inputs indicative of the sine and cosine of an angle through which said point is to be rotated to said first and second converters, respectively; and means for summing; said first output of said first converter; said first output of said second converter; the negative of said second output of said first converter; the negative of said second output of said second converter; and whereby the sum is an analogue quantity indicative of the new ordinate of said point after rotation through said angle.