Abstract: A pulse width modulated signal generator is comprised of an N-bit ripple counter (12) that generates a down counted output value which is input to a combinatorial logic circuit for generating a pulse width that is defined as a predetermined number of clock cycles from a clock that is utilized to clock the ripple counter (12). The ripple counter (12) is cycled from a maximum value to a minimum value with the value "0000" inhibited. This count value is combined with a plurality of AND gates which also receive as an input an enable value from a input (18). When the ripple counter (12) is initiated at its maximum value, the output is pulled high and then a predetermined number of the clock pulses counted, as defined by the value of the enable word. Thereafter, the output is pulled low to define the length of the pulse.
Abstract: A differential inverter such as may be used in an oscillator circuit. The differential inverter is connected between first and second current sources. The differential inverter includes first and second single signal CMOS inverters connected in parallel between the first and second controlled current sources. Each of the current sources is a MOS transistor. A bias circuit is connected to the control gates of the MOS transistors and provides bias signals thereto, the bias circuit includes a variable current source with bias signals being generated in response to the current flow in the variable current source.
Abstract: A modulating device applicable to a digital radio communications system which is adaptable to a 16 or greater multi-level QAM modulation system. The device has two multi-input digital filters to implement the role of cosine roll-off filters. A logic circuit precedes the digital filters to logically manipulate n-bit data streams except for m bits (m<n) thereof which should be modulated, in a predetermined manner. The logic circuit is capable of correcting deviations of signal points of a QAM wave or changing the contour of signal constellation to a circular contour or the like, as desired.