Frequency drift

About: Frequency drift is a research topic. Over the lifetime, 5054 publications have been published within this topic receiving 56191 citations. The topic is also known as: chirp rate.

Direct conversion receiver

Abstract: In a frequency modulation radio receiver with direct conversion, a local oscillator signal is generated having a frequency within a preselected frequency range and the frequency is varied in response to a variable low frequency signal; the local oscillator signal is mixed with a received signal to provide a baseband signal. The variable low frequency signal is generated by a controlled oscillator in inverse relationship to a direct current component in said baseband signal. In a frequency modulation radio transceiver a broadcast function is provided by varying the low frequency signal with an information signal with the resulting local oscillator frequency being varied accordingly and amplified for broadcast. The transceiver is controlled to operate alternately in either a receive mode and a broadcast mode at substantially the same frequency. While in the receive mode the controlled oscillator causes the local oscillator signal to be drawn toward the carrier frequency of a received signal yielding preferred direct conversion of modulating information into the base band.

Apparatus and method for frequency modulation

Abstract: A method and apparatus for frequency modulating a continuous wave signal is shown to comprise a voltage-controlled oscillator (VCO) having a first and a second control loop to maintain the carrier frequency of such VCO at a frequency determined by a crystal-controlled oscillator and to maintain the peak deviation of the FM modulation on such carrier frequency at a value equal to the deviation of the first Bessel null from the carrier frequency.

Television tuning system with provisions for receiving rf carrier at nonstandard frequency

Abstract: RCA 70,849 TELEVISION TUNING SYSTEM WITH PROVISIONS FOR RECEIVING RF CARRIER AT NONSTANDARD FREQUENCY Abstract of Disclosure A tuning system for a television receiver includes a phase locked loop for tuning a local oscillator to the nominal local oscillator frequencies required to tune the receiver to RF carriers at standard broadcast frequencies allocated to the various channels a viewer may select. The tuning system also includes an automatic fine tuning (AFT) frequency discriminator fox tuning the local oscillator to minimize any deviation between the frequency of an actual picture carrier and the nominal picture carrier frequency. If the receiver is coupled to a television distribution system which provides RF carriers having nonstandard freq-uencies arbitrarily near respective ones of the standard broadcast frequencies, when the phase locked loop has achi-eved lock at a nominal frequency, a mode control unit selectively couples the discriminator and a frequency drift control circuit to the local oscillator. If the frequency of the local oscillator drifts more than a predetermined off-set from the frequency synthesized under phase locked loop control because no carrier has been detected by the discrim-inator, discriminator and drift control are terminated so that the receiver will not be tuned to an undesired carrier such as, for example, the lower adjacent channel sound carr-ier, and phase locked loop control is reinitiated to synthe-size a local oscillator signal having a frequency incremented from the frequency of the originally synthesized local oscillator signal by a predetermined amount. After the phase locked loop is locked at an incremented frequency, discriminator control is again initiated. If, during this cycle of discriminator control, the local oscillator again drifts more than the predetermined offset from the RCA 70,849 incremented local oscillator frequency because no carrier is detected by the discriminator, phase locked loop control is again reinitiated to synthesize a local oscillator signal having a frequency decremented from the frequency of the originally synthesized local oscillator signal by the pre-determined amount. If during any discriminator control cycle the local oscillator has not drifted further than the predetermined offset because the discriminator has tuned the local oscillator to a carrier within the predetermined offset, phase locked loop control is not reinitiated and the tuning sequence is complete. -1a-

FMCW radar system with linear frequency modulation

Abstract: It has been proposed in accordance with the invention to determine the linearity of the modulated oscillator frequency of an FMCW radar by means of the Hilbert transformation and to supply a control voltage, corresponding to the deviation, to the controllable oscillator via a digital/analog converter. A control and computing unit is used to determine the linearity of the modulated oscillator frequency.

Measuring temperature change in an electronic biomedical implant

Abstract: The change in temperature of an implanted electronic device can be determined by providing power to one or more circuit elements included in the implanted electronic device, wherein the circuit elements comprise a non-crystal oscillator A shift in the output frequency associated with the non-crystal oscillator can be detected, and the temperature change of the implanted electronic device can be determined based on the detected output frequency shift One or more signals based on the output frequency associated with the non-crystal oscillator can be transmitted by the implanted electronic device The transmitted signals can be received by an external device, which can detect the current output frequency associated with the non-crystal oscillator from the transmitted signals and compare the current output frequency with a previous output frequency to determine the output frequency shift associated with the non-crystal oscillator The output frequency can, for example, be converted to a voltage measure