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:
May. 05, 1992
Filed:
May. 06, 1991
Simha Erlich, Haifa, IL;
Hughes Aircraft Company, Los Angeles, CA (US);
Abstract
A digital FM modulator (10) which functions to modulate a fixed frequency, e.g. RF, reference signal f.sub.r with an incoming AM analog signal v(t) by way of utilization of digital signal processing circuitry (14, 18, 22, 26, 28, 38, 48). The digital FM modulator 10 includes a digital encoder, e.g. a codec 14, which samples the incoming analog signal v(t) at a prescribed sampling rate f.sub.s, and converts it into a digital signal S.sub.D comprised of successive digital words representative of a prescribed parameter (e.g. amplitude) of the analog signal v(t) at corresponding, successive sampling times t.sub.i. This digital signal S.sub.D is a digital data stream which is subsequently conditioned for input to a direct, digital synthesizer (DDS) (48), which, in response to this input, synthesizes an output signal having I.sub.A and Q.sub.A components disposed in phase quadrature relation to each other. The DDS output signal components I.sub.A and Q.sub.A are coupled to respective first and second mixers (62, 68) of an I/Q hybrid circuit (59), with the I.sub.A and Q.sub.A DDS output signal components serving to modulate the reference RF carrier signal f.sub.r, which is also coupled to the mixers (62, 68) in phase quadrature, to thereby ultimately produce, after summation of the resultant IF.sub.A and IF.sub.B mixer output signals, a modulated FM signal P(t). The modulated FM signal P(t) is essentially equivalent to a modulated FM signal generated by an analog FM modulator, wherein the incoming analog signal v(t) modulates a voltage controlled oscillator (VCO).