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:
Apr. 07, 1998
Filed:
Jan. 31, 1995
Frederick J Harris, Lemon Grove, CA (US);
Robert W Caulfield, San Diego, CA (US);
William H McKnight, San Diego, CA (US);
The United States of America as represented by the Secretary of the Navy, Washington, DC (US);
Abstract
A band-pass sigma-delta modulator includes a translator for tuning to a selected signal passband within the tuning range of the modulator. In a network implementation, the translator is integral with each integrator associated with the sigma-delta modulator(s). The translator can comprise a network having a transfer function defined in the Z-domain as (Z.alpha.-1)/(Z-.alpha.), where -1.ltoreq..alpha..ltoreq.1 defines the tuning. The value of .alpha. is defined as .alpha..tbd.cos(2.pi.f.sub.gm /f.sub.s), where f.sub.gm is the geometric mean frequency of the passband and f.sub.s is the input sample frequency of the sigma-delta modulator(s). The invention can benefit many signal processing applications such as, for example, A/D, D/A and D/D converters; and digital communication systems including digital radio and digital TV. In digital communications (e.g., radio, TV, etc.), the invention can be used where it is desirable to digitize the full tuning range or bandwidth of a receiver at an intermediate frequency early in the processing chain, thus allowing digital tuning or mixing of the desired signal. Such digital mixing or tuning overcomes the limitations of analog mixers/receivers, for example limited linearity in dynamic range as well as the problems associated with aliasing, artifacts, ghosts, harmonics, distortion, gain and phase mismatch, etc. The sigma-delta modulator of the invention also provides variable bandwidth, is operationally stable and is easily and inexpensively realized.