Steven Lloyd Hendrix

US Patent:

6172579, Jan 9, 2001

Filed:

Feb 2, 1999

Appl. No.:

9/241810

Inventors:

Farron L. Dacus - Irving TX
Steven P. Hendrix - Sagamore Hills OH

Assignee:

Cleveland Medical Devices Inc. - Cleveland OH

International Classification:

H03L 300

US Classification:

332128

Abstract:

The present invention relates to a frequency modulated system, and a method for operating same, including a phase locked loop frequency synthesizer circuit which synthesizes a carrier frequency through the use of an electronically controlled oscillator. The circuit, which has a certain loop bandwidth, includes a reference frequency source and a bypassed correcting integrator. A modulating signal simultaneously modulates the oscillator, the reference frequency source and the bypassed correcting integrator such that the carrier frequency is frequency modulated with a certain frequency deviation. The magnitude of the modulation of the oscillator, the reference frequency source and the correcting integrator are controlled over a frequency range by frequency blending the reference frequency source and the bypassed correcting integrator such that low distortion modulation over a wide frequency range is achieved.

US Patent:

62230611, Apr 24, 2001

Filed:

Jul 25, 1997

Appl. No.:

8/900329

Inventors:

Farron L. Dacus - Irving TX
Robert N. Schmidt - Cleveland OH
Steven P. Hendrix - Sagamore Hills OH

Assignee:

Cleveland Medical Devices Inc. - Cleveland OH

International Classification:

H04B 100

US Classification:

455574

Abstract:

An apparatus for low power radio communication comprising a transmitter having a frequency synthesizer and transmit antenna such that the frequency synthesizer comprises a phase locked loop circuit with a voltage controlled oscillator having a variable frequency output and with a loop filter/sample and hold circuit that allows opening of the synthesizer control loop and with special means of limiting the resulting frequency drift in the open loop state. The transmitter produces an output signal and the loop filter/sample and hold circuit holds the voltage controlled oscillator substantially on frequency such that the output signal remains stable, with a minimum of frequency drift, over a period of time when the phase lock loop synthesizer is set to an open loop state to allow frequency modulation unimpeded by the normal frequency correcting action of the synthesizer and for the frequency synthesizer to be partially powered down to reduce power consumption. The frequency modulation is linearized over a band of interest and undesired frequency shift at the initiation of modulation is suppressed. Receiver having automatic frequency control is included to extend the open loop transmit time of the transmitter, where the automatic frequency control system automatically tunes the receiver to correct for frequency error and for the frequency drift resulting from opening the phase locked loop of the frequency synthesizer, allowing communications to continue in the presence of such drift and of other frequency error.