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:
Mar. 06, 1990
Filed:
May. 09, 1988
Gregory M Cutler, Cupertino, CA (US);
Hewlett-Packard Company, Palo Alto, CA (US);
Abstract
A digital integrating mixer is described including a bandpass filter for filtering an input signal, a comparator for comparing the filtered signal to a reference signal to provide an output which may be of one of two values. A cascaded string of D flip-flops samples the comparator output at predetermined times to provide a first and second type of sample. The time interval between any two samples of the same type is an integral multiple of the cycles of the input signal. The time interval between any two samples of different types is different from an integral multiple of a cycle of the input signal. The mixer also includes a counter which counts up when the sample is of the first value and counts down when the sample is of the second value, when the sample is of the first type, and counts in the opposite direction when the sample is of the second type. If the string of D flip-flops samples approximately an equal number of the first and second types of samples, DC offset in the mixer is reduced. In addition a two channel digital integrating mixer with an analogous structure is disclosed. In the two channel mixer, the string of D flip-flops may also be used to sample the comparator output at predetermined times to provide four types of samples where the time interval between any two samples of the same type is an integral multiple of a cycle of the input signal. The time interval between any first type of sample and any second type of sample is different from an integral multiple of a cycle of the input signal; the same is true between the third and fourth types of samples. The time between any first and second type of sample and any third and fourth type of sample is other than a multiple of a half cycle of the input signal. A first counter is used to count in response to the first or second types of samples and the second in response to the third or fourth types of samples in the same manner as in the single channel mixer. If the string of D flip-flops samples approximately equal number of first and second types of samples and approximately an equal number of third and fourth types of samples, DC offset in the two channel mixer is reduced.