« PreviousContinue »
United States Patent m
 Patent Number:  Date of Patent:
 FREQUENCY MODULATED MODEM TRANSMITTER
 Inventor: William N. Smith, III, Carrollton, Tex.
 Assignee: Agile Systems, Inc., Carrollton, Tex.  Appl. No.: 796,007  Filed: Nov. 7,1985
 Int. Q.* H03C3/09
 U.S.C1 375/62; 455/113;
331/1 R; 332/19
 Field of Search 375/45, 62, 65, 120;
331/10, 23, 179, 1 R, 1 A; 332/16 R, 19;
 References Cited
U.S. PATENT DOCUMENTS
4,068,199 1/1978 Madoff 375/65
4,471,328 9/1984 Chapman 375/62
4,481,489 11/1984 Kurby 375/120
4,567,603 1/1986 Howell et al 375/65
OTHER PUBLICATIONS Millman & Halkias, Integrated Electronics: Analog and
Digital Circuits and Systems, McGraw-Hill, 1972, pp. 636-647.
Primary Examiner—Benedict V. Safourek
Attorney, Agent, or Firm—Hubbard, Thurman, Turner
A frequency modulated transmitter including a reference frequency source providing a reference frequency to a phase locked loop circuit. The phase locked loop circuit provides a frequency output signal stabilized in accordance with this reference frequency and in accordance with a feedback signal. The phase locked loop circuit further includes a data input circuit that adjusts the output frequency in accordance with input data. Also included is the feedback circuit that provides the feedback signal to the phase locked loop circuit. This feedback circuit is derived from the frequency output signal. A synchronization circuit is connected to the feed back circuit and synchronizes the output of the feedback circuit with the reference frequency signal and the input data.
2 Claims, 5 Drawing Figures
U. S. Patent Jua 2,1987 Sheet 2 of3 4,670,888