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. 27, 1997
Filed:
Sep. 29, 1994
Ross W Lampe, Raleigh, NC (US);
Jyun-chen Chen, Chapel Hill, NC (US);
Ericsson Inc., Research Triangle Park, NC (US);
Abstract
Continuous phase modulated (CPM) signals, such as quaternary CPFSK signals, are filtered to limit their bandwidth while simultaneously minimizing the amount of amplitude modulation and intersymbol interference introduced by this filtering process. By designing a modulation filter such as a finite impulse response (FIR) filter to add only a nominal, controlled amount of amplitude modulation, high efficiency, nonlinear power amplifiers may be employed to transmit the filtered CPFSK signals. Although the filter adds a small amount of amplitude modulation and intersymbol interference, digital signal processor-based receivers satisfactorily demodulate this type of signal using sequence estimation algorithms such as the Viterbi algorithm. Thus, the filtering of CPM signals permits narrowing of the transmitted signal spectrum while managing the intersymbol interference resulting from the controlled amount of amplitude modulation added by filtering. Narrowed bandwidth along with high efficiency, nonlinear power amplifiers make the present invention particularly well suited to narrowband mobile radio communications.