Polar-to-cartesian, digital-to-analogue converter

Claim 2

The combination comprising: input terminal means for receiving a digital signal that is representative of the value of an input variable quantity; an output terminal; digital-to-analogue converter means electrically connected to said output terminal and having a plurality of controls for selectively providing to said output terminal a voltage, the amplitude of which is proportional to a predetermined function of a different value of said input variable for each different combination of said plurality of controls that is activated; circuit means electrically connected to said input terminal means and to said digital-to-analogue converter means for activating that combination of controls that causes said digital-to-analogue converter means to provide a voltage having an amplitude proportional to said predetermined function of the value of said input variable quantity; said digital-to-analogue converter means comprising linear means electrically connected to said input terminal means and to said output terminal for generating a voltage which is proportional in amplitude to the value represented by said digital signal received by said input terminal means; and shunting means including said plurality of controls and being electrically connected to said linear means and to said input terminal meaNs for changing the amplitude of the voltage output from said linear means to conform it to a predetermined function of said digital signal received by said input terminal means.

Claim 3

The combination according to claim 1 in which said shunting means comprises: a plurality of impedances having different values; a plurality of switches electrically connected to said plurality of impedances and to corresponding sources of voltage potential; and logical switching means electrically connected to said input terminal means and to said plurality of switches, for selectively closing those switches which will place an impedance and voltage potential between said output terminal and ground that will alter the amplitude and provide a voltage translation of said voltage output from said linear means to cause it to conform to a predetermined function as determined by said logical means.

Claim 4

The combination according to claim 2 in which said linear means comprises a binary weighted-resistor ladder digital-to-analogue converter.

Claim 5

Apparatus as defined in claim 1 for converting a digital representation of an angle into an analogue representation of a trigonometric function of the angle wherein: said input terminal means receives said digital representation of said angles; said linear means generating a voltage which is proportional in amplitude to the value of said digital representation of said angle received by said input terminal means; and said shunting means changing the amplitude of the output voltage from said linear means appearing on said output terminal to conform it to said analogue representation of the trigonometric function of said angle.

Claim 6

Apparatus for converting a digital signal which represents an angle to an analogue signal representing a predetermined trigonometric function of said angle according to claim 4 in which said linear means is a binary ladder.

Claim 7

Apparatus for converting a digital signal which represents an angle to an analogue signal which represents a predetermined trigonometric function of the angle according to claim 5 in which said shunting means comprises a means for electrically connecting an impedance and voltage potential between said output terminal and a reference potential so as to alter said linear means output voltage to cause it to conform to the slope of the curve of the trigonometric function of said angle and to provide the required voltage translation to approximate the trigonometric function.

Claim 8

Apparatus for converting digital polar information to analogue cartesian information, comprising: a first input terminal adapted to receive digital information representative of the polar angle; a second input terminal adapted to receive digital information representative of a radius vector; an X output terminal adapted to provide analogue abscissa information; a Y output terminal adapted to provide ordinate analogue information; a first binary ladder electrically connected to said first input terminal; a second binary ladder electrically connected to said first input terminal; first switching means electrically connected to said first input terminal and to said first binary ladder for changing the slope of the output voltage from said first binary ladder to cause it to approximate the sine of said polar angle; second switching means electrically connected to said first input terminal and to said second binary ladder for changing the slope of the output voltage from said binary ladder to cause it to approximate the cosine of said polar angle; third binary ladder means having an input electrically connected to said second input terminal and a second input electrically connected to the output from said first switching means and having its output connected to said Y output terminal for converting said digital representation of said radius vector to an analogue value and multiplying it by the output from said first switching means; and a fourth binary ladder Means having a first input electrically connected to said second input terminal and a second input electrically connected to the output from said second switching means and having its output electrically connected to said X output terminal, for converting said digital representation of said radius vector to an analogue value and multiplying said analogue value by the output from said second switching means.

Claim 9

Apparatus for converting digital polar information to analogue cartesian information, comprising: a first input terminal adapted to receive digital information representative of the polar angle; a second input terminal adapted to receive digital information representative of a radius vector; an X output terminal adapted to provide analogue abscissa information; a Y output terminal adapted to provide ordinate analogue information; a first binary ladder electrically connected to said first input terminal; a second binary ladder electrically connected to said first input terminal; first switching means electrically connected to said first input terminal and to said first binary ladder for changing the slope of the output voltage from said first binary ladder to cause it to approximate the sine of said polar angle; second switching means electrically connected to said first input terminal and to said second binary ladder for changing the slope of the output voltage from said binary ladder to cause it to approximate the cosine of said polar angle; third binary ladder means having an input electrically connected to said second input terminal and a second input electrically connected to the output from said first switching means and having its output connected to said Y output terminal for converting said digital representation of said radius vector to an analogue value and multiplying it by the output from said first switching means; and a fourth binary ladder Means having a first input electrically connected to said second input terminal and a second input electrically connected to the output from said second switching means and having its output electrically connected to said X output terminal, for converting said digital representation of said radius vector to an analogue value and multiplying said analogue value by the output from said second switching means.

Claim 10

Apparatus for converting digital polar information to analogue cartesian information according to claim 7 in which said first switching means comprises a plurality of impedances and corresponding voltage sources; each impedance of said plurality of impedances being capable of changing the slope of said first binary ladder and each corresponding voltage source providing a voltage translation so as to approximate the slope of a different portion of a sine function; and decoding means electrically connected to said first input terminal and to said plurality of impedances for electrically connecting that one of said plurality of impedances and corresponding voltage sources in shunt with said first binary ladder which cause the slope of said first binary ladder to correspond to the slope of the sine of the polar angle represented by said digital signal being received on said first input terminal.