The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 22, 1997
Filed:
May. 09, 1996
Wong Hee, San Jose, CA (US);
Gabriel Li, San Francisco, CA (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
A phase-to-frequency converter uses a triangular waveform synthesizer to generate a triangular wave using both PDM and a DC modulation scheme. A 4-bit PDM and associated logic generates the PDM output waveform with polarity information and two switching waveforms that encode the DC level information to provide a resultant sum. The resulting waveform, after filtering, is the multiple phases of the triangular waveform. The generated multiple phases of the triangular wave are then modified by reducing the ramp rate at appropriate points to suppress the third harmonic and its multiples. The ramp rate is proportional to the pulse density output of the Pulse Density Modulator. In one embodiment, the rate of the PDM output is reduced by one half during appropriate periods by gating the output by its clock, thereby reducing its density by one half during those periods.