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:
Jul. 12, 1994
Filed:
Jun. 16, 1993
Takashi Matsuura, Tokyo, JP;
Nec Corporation, , JP;
Abstract
A multilevel frequency-shift keying (FSK) modulator is disclosed in which the transient response for frequency transition can be easily set. The modulator is of a type in which a frequency generated by a voltage-controlled oscillator (VCO) is changed in accordance with multilevel code and is phase-locked by a phase-locked loop (PLL). The modulator is provided with a phase-lock feedback circuit that, combined with a VCO, makes up a PLL, and includes first and second VCOs and a filter having a desired transient response characteristic. At a transient time of frequency transition due to a change of the multilevel code, the first VCO and feedback circuit makes up the PLL, and a first control voltage for the first VCO produced in the PLL is inputted as a second control voltage to the second VCO through the filter. Accordingly, the FSK signal delivered from the second VCO has a transient response characteristic depending on the characteristic of the filter, and as a result, the transient response characteristic of the FSK modulator can be set to a desired characteristic by modifying the characteristic of the filter without changing the other circuit parameters.