A direct digital synthesizer that outputs at least a predetermined output frequency related signal from a received digital signal, K, with minimum spurious signal levels. A storage device stores an initial phase value of the digital signal, K, and provides the initial phase value on an output thereof. An adder is provided having a first input for receiving the digital signal, K, having a second input and having an output which provides a summation of signals received on the first and second inpu...

A digital tone generator includes a modulo adder, an increment number register, two latches and a master clock. The adder continuously adds one of a plurality of predefined increment numbers with the adder's previously generated sums to create further sums and a carry output corresponding to one of a plurality of predetermined output tone frequencies. The system characteristics and increment numbers are selected to correspond to the predetermined frequencies and generate exact tonal frequency si...

A lookup table includes a complementer, a memory and a switching element. The complementer selectively complements a subset of bits of a multibit designation of an angle based on a most significant bit of the multibit designation to produce an address signal. The memory is addressed by the address signal and produces two values. The switching element receives the two values from the memory and selectively outputs the values based on the most significant bit.

A trigonometric function arithmetic processor comprises a first arithmetic unit for executing, in m steps, a pseudo-division operation for obtaining from an initial value .theta. a sequence of numbers {ak} and a pseudoremainder .epsilon. which fulfill the following equation ##EQU1## where a.sub.k =+1 or -1, and the trigonometric function arithmetic processor also comprises a second arithmetic unit for executing the following pseudo-multiplication operation in m steps from initial values Xm=P and...

A phase accumulator for accumulating digital frequency words, which, as accumulated, represent the phase of a cyclic waveform of a predetermined frequency. The phase accumulator includes a coarse-component accumulator for accumulating coarse phase components of the digital frequency words; a fine-component accumulator for accumulating fine phase components of the digital frequency words; and means for incrementing the coarse-component accumulator in response to accumulation of the fine phase com...

A method of comparing a newly acquired working image with a previously acquired reference image and a system for comparing a newly acquired working image with a previously acquired reference image. A reference text regarding areas of interest is displayed. This invention is particularly useful for displaying and comparing slices obtained by computer tomography and magnetic resonance imaging technology.

A programmable frequency synthesizer (PFS) consists of three serially conted stages: an accumulator, a triangle converter, and a sine shaper. The accumulator is the frequency-generating stage of the synthesizer. It consists of an input latch to store the binary programmed frequency, an adder, an output latch to store the output of the adder, and a clock oscillator. The output frequency of the accumulator can be directly scaled by changing its clocking frequency. The square wave output of the acc...

A digital frequency synthesizer for generating square wave signals employing a phase accumulator, triangle wave logic function, smoothing filter, and hard limiter. A triangle wave logic function simplifies the implementation of stable square wave signals.

A simple method and apparatus for generating approximate sine waves is described. A digital accumulator or adder is driven at a basic counting rate to accumulate increments representative of phase with the total sum representative of total phase angle of a sine wave. The output is periodically sampled and the value is converted into an analog output voltage in a normal D to A converter. A straight line ramp voltage approximation to the sine wave function is created as the result. The accumulator...

The invention relates to a device for reducing unwanted frequency components in digital frequency generation, comprising an accumulator device (4, 5) for generating output signals depending on an input code (F) corresponding to a desired frequency, the accumulator device (4, 5) being connected to at least one memory unit (6, 7) which comprises codes corresponding to wave shapes, and further comprising a generator (1) for generating a random code (P) and a digital/analog converter (9) for generat...