A tuning system employing a UHF tuner for tuning a television receiver over the UHF band and the ultraband is disclosed. The system employs indirect frequency synthesis in providing user initiated, microcomputer generated commands to the tuner in the form of a channel number and an operating mode control word. Inter-channel spacing of 6 MHz is maintained over both tuning bands with a respective channel in one band offset from the closest channel in the other band by 2 MHz.

Dual mode UHF tuning system

A digital pulse-width modulator is provided that receives a digital command input signal and a secondary control input signal and provides a pulse-width-modulated output signal. The pulse-width-modulated output signal comprises a pulse-width that corresponds to an integer number of slots each having a time duration. The integer number of slots corresponds to a value of the digital command signal, and the time duration is determined based upon the secondary control input signal. In one embodiment, the digital pulse-width-modulator comprises a plurality of delay cells arranged in series for propagating a clock signal through the plurality of delay cells. A time delay for each of the delay cells is determined by the secondary control input signal. A controller is enabled to set the output signal to a first value at the start of a propagation of the clock through the plurality of delay cells and to set the output signal to a second value when the clock signal propagates to one of the delay cells identified by the digital command signal. In another embodiment, the digital pulse-width-modulator is used with a switched-mode power converter. A digital command signal based on a feedback signal from the converter and a secondary control signal derived from an input voltage of the converter are received by the digital pulse-width-modulator. The digital pulse-width-modulator provides a pulse-width-modulated output signal based on the digital command signal and the secondary control signal. The output signal is then provided to the converter to control at least one switch of the converter.

Digital pulse-width modulator

A pulse width digital to analog converter is constructed which provides an output clock rate that is a multiple of the input sampling rate. In one embodiment a latch is used to store N-bit digital word representing the analog signal value to be generated. (N-K) of the most significant bits are stored in a counter which decrements its count in response to a clock signal. A plurality of least significant bits of said digital word stored in said latch are applied to a logic circuit. A ring counter is utilized to indicate which section of the output signal is currently being generated. The plurality of the least significant bits of the digital word stored in the latch, together with the output signals from the ring counter, are applied to said logic circuit, and the transition of the output signal of the digital to analog converter from a logical one to a logical zero is delayed, when required, to provide a slightly increased output pulse width in response to said plurality of least significant bits of said digital word, thereby maintaining or even increasing the resolution of the system.

Digital to analog converter utilizing pulse width modulation

A digital-to-analog converter suitable for use in a television tuning system for converting bits of a digital word to a corresponding tuning voltage includes a first digital-to-duty factor converter responsive to a group of the most significant bits of the digital word for generating a first incrementally variable duty factor pulse signal and a second digital-to-duty factor converter responsive to a group of the next most significant bits of the digital word for generating a second incrementally variable duty factor pulse signal. The amplitude of the first and second pulse signals are differentially weighted, e.g., by standard tolerance resistors (±10%), such that the maximum average DC potential of the second signal is greater than a single increment of the average DC potential of the first signal. The weighted signals are combined and filtered by a lowpass filter which derives the tuning voltage. This deliberately results in non-monotonicity but without a significant reduction in resolution.

Digital-to-analog converter useful in a television receiver

An all-electronic, integrated television channel tuning indirect frequency synthesis system capable of operating over the VHF, UHF and CATV spectra in which digital bandswitching is accomplished automatically. Keyboard selected control inputs are provided to a microcomputer for the generation of digital bandswitching signals and, in combination with a phase locked loop, tuning voltages. The bandswitch signals and tuning voltages are provided to a tuner having several resonant frequency circuits, each including a varactor diode and a plurality of coupled inductors and switching diodes.

Multi-mode automatic channel frequency synthesis system

A voltage generating system comprising generators for producing a plurality of reference voltages, switching devices provided in the reference voltage generators such that any of a given one or given ones of the reference voltages may be selectively taken out, an integrator to smooth a selected reference voltage to obtain an output voltage, a switching pulse generator to produce a switching pulse signal for switching the switching devices and a circuit to vary the duty ratio of the switching pulse signal so as to vary the magnitude of the output voltage. This voltage generating system may be used for generating a channel selection voltage for electronic tuners (varactor tuners), for digital-to-analog converter circuits etc.

Voltage-generating system

A D-A converter for converting a digital signal to a duty factor of a pulse train signal and for averaging the pulse signal by a low-pass filter to convert it to an analog signal is disclosed. A plurality of pulses which are to be selected in accordance with the input digital signal comprise a plurality of basic pulses of different phases and pulse widths derived by frequency division and auxiliary basic pulses which occur at a cycle period which is at least twice as long as a repetition cycle period of the basic pulses. The basic pulses are selected by high order bits of the digital signal while the auxiliary basic pulses are selected by low order bits of the digital signal to produce an output pulse train signal a duty factor of which changes in accordance with the digital signal. The pulse train signal is then averaged to convert it to an analog signal.

D-A Converter utilizing a main and auxiliary pulse generator to control the duty factor of an averaged pulse train signal

OF THE DISCLOSURE A D-A converter for converting a digital signal to a duty factor of a pulse train signal and averaging the pulse signal by a low-pass filter to convert it to an analog signal is disclosed A plurality of pulses which are to be selected in accordance with the input digital signal comprise a plurality of basic pulses of different phases and pulse widths derived by frequency division and auxiliary basic pulses which occur at a cycle period which is at least twice as long as a repetition cycle period of the basic pulses, and the basic pulses are selected by high order signals of the digital signal while the auxiliary basic pulses are selected by low order digit signals of said digital signal to produce an output pulse train signal a duty factor of which changes in accordance with the digital signal The pulse train signal is then averaged to convert it to an analog signal

Yukio Koyanagi

Papers

Voltage-generating system

D-A Converter utilizing a main and auxiliary pulse generator to control the duty factor of an averaged pulse train signal

D-a converter

Digital-analog-wandler