294 results about "Modulation index" patented technology

A space vector pulse-width modulator (SVPWM) and a method implemented by the modulator. A precalculation module accepts Ua and Ub modulation indexes and in response thereto, outputs modified Ua and Ub information; a sector finder has a U module which receives the modified Ua information and outputs a U sector; and a Z module which receives the U sector and the modified Ub information and outputs a Z sector. The U sector and the Z sector are 2-phase control signals for implementing 2-phase modulation. For 3-phase modulation, the SVPWM and method further possess an active vectors calculation module and an assign vectors module which receive the modified Ua and Ub information and the U sector, and which calculate active vectors for 3-phase modulation; a zero vector selector which receives the Z sector and calculates zero vectors for 3-phase modulation; and a PWM counter block which receives the active vectors and zero vectors and outputs 3-phase control signals for implementing 3-phase modulation. The SVPWM and method may have a symmetrical PWM mode, an asymmetrical PWM mode, or both. Advantageously there may also be a rescale and overmodulation module which receives duration information corresponding to the vectors and in response thereto, detects the occurrence of overmodulation. Overmodulation may be detected in response to a negative zero vector time. The module may respond to overmodulation by clamping the zero vector time to zero and rescaling the active vector times to fit within the PWM cycle. The rescaling may restrict a voltage vector to stay within hexagonal boundaries on the space vector plane, while preserving voltage phase.

An external transmitter circuit drives an implantable neural stimulator having an implanted coil from a primary coil driven by a power amplifier. For efficient power consumption, the transmitter output circuit (which includes the primary coil driven by the power amplifier inductively coupled with the implanted coil) operates as a tuned resonant circuit. When operating as a tuned resonant circuit, it is difficult to modulate the carrier signal with data having sharp rise and fall times without using a high power modulation amplifier. Sharp rise and fall times are needed in order to ensure reliable data transmission. To overcome this difficulty, the present invention includes an output switch that selectively inserts a resistor in the transmitter output coil circuit in order to de-tune the resonant circuit only during those times when data modulation is needed. Such de-tuning allows sharp rise and fall times in the data modulation without the need for using a high power modulation amplifier. Because data modulation is typically needed for only a small percent of the time that a carrier signal is present, it is thus possible using the present invention to achieve reliable data modulation, transmission and reception without having to use a high power modulation amplifier in the transmitter.

A coupling arrangement for allowing multiple wavelengths to be coupled into and out of a relatively thin silicon optical waveguide layer utilizes a diffractive optical element, in the form of a volume phase grating, in combination with a prism coupling structure. The diffractive optical element is formed to comprise a predetermined modulation index sufficient to diffract the various wavelengths through angles associated with improving the coupling efficiency of each wavelength into the silicon waveguide. The diffractive optical element may be formed as a separate element, or formed as an integral part of the coupling facet of the prism coupler.

An image encoding device includes: a predictor which predicts an input image signal and generates a predicted image signal; a subtractor which calculates a difference between the input image signal and the predicted image signal to generate a predicted residual signal; a converter which converts the predicted residual signal to generate a conversion coefficient; a modulation unit which modulates a quantization matrix to obtain a modulated quantization matrix; a quantizer which quantizes the conversion coefficient by using the modulated quantization matrix to generate a quantized conversion coefficient; and an encoder which encodes the quantized conversion coefficient and the modulation index to generate encoded data.