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:
Feb. 22, 2000
Filed:
Apr. 21, 1998
Christian V Olgaard, Sunnyvale, CA (US);
Benny Madsen, Los Altos, CA (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
A modulation synthesizer circuit produces a fixed intermediate frequency unmodulated signal without harmonics aliasing back into the transmit spectrum, thus, eliminating the need for a bandpass filter. The modulation synthesizer circuit includes a phase shifter placed before the down conversion mixer. The phase shifter may be placed outside the modulation synthesizer loop such that the phase shifter produces quadrature carrier wave signals to the down conversion mixer. In the alternative the phase shifter may be kept within the modulation synthesizer loop and produce quadrature modulated transmit signals to the down conversion mixer. Any harmonic frequencies generated by the phase shifter are harmonics of the carrier wave signal or modulated transmit signal. Thus, with the appropriate choice of carrier wave signal or modulated transmit signal, any harmonics generated by the phase shifter can be prevented from aliasing back into the transmit spectrum and therefore need not be filtered. Consequently, the bandpass filter typically found after the quadrature modulator can be eliminated.