Abstract: In a communications data link network of the type having a plurality of ground stations and a single moving airborne station, there is provided a doppler frequency compensation circuit in each of the ground stations. The downlink carrier frequency is fixed and continuously broadcast to the receiving ground station which continuously receive the doppler shifted carrier signal. The ground stations are provided with coherent demodulators which provide a coherent I.F. recovered carrier signal that is applied to a scaling phase-locked loop to provide a deviation frequency signal that is applied to an inverting phase-locked loop which provides a pre-compensated uplink R.F. carrier signal. The uplink R.F. carrier signal has a compensated uplink doppler frequency component which equals the inverted and scaled doppler frequency of the received downlink carrier.
Abstract: The invention disclosed herein relates in general to an improved circuitry or narrow band frequency tracking system for doppler radar and includes third order phase lock loop circuitry to improve tracking techniques. This enables tracking input frequency variations caused by target maneuvers with substantially smaller tracking bandwidths than is currently possible.
Type:
Grant
Filed:
December 3, 1973
Date of Patent:
July 23, 1991
Assignee:
The United States of America as represented by the Secretary of the Navy
Abstract: A circuit for removing abrupt phase changes in a received signal, such as those caused when an object tracking system's directional receiving antenna becomes misaligned with the tracked object. The circuit uses a phase detector to determine when an abrupt phase change has occurred, such as when a signal returned from the tracked object aligns with an antenna null and reverses the phase of a control signal fed to a phase locked oscillator. A delaying low pass filter insures the control signal is stable before it is fed to the phase locked oscillator.
Abstract: A static-split tracking radar system with substantially improved performance. The system includes parallel signal processing channels for processing sum and difference signals from a target-seeking aerial array, to produce target tracking signals. Novel means are provided for trimming relative phase and gain of these channels to achieve substantially perfect matching, which gives a receiver stability sufficient for homing head use in a guided missile system. The system also includes a receiver for acquiring a reference frequency signal, the receiver having novel bandwidth adaptation and doppler tracking facilities. Other novel features provide improved clutter rejection and jamming immunity.
Abstract: A signal acquisition circuit for a missile guidance system has a phase lock loop which is responsive to incoming signals received from a target and will lock on to the frequency of the received signal. The bandwidth of the phase lock loop is altered in dependence on the signal being received in order to distinguish between a valid target and noise.
Type:
Grant
Filed:
April 5, 1978
Date of Patent:
February 9, 1988
Assignee:
The Marconi Company Limited
Inventors:
Michael A. Jones, John W. Attwood, Peter Szyszko, John T. Floyd
Abstract: A phase-lock loop system with particular use in radar tracking systems is disclosed. From a number of input signals of varying frequencies such as a carrier frequency and several side band frequencies the system can lock into phase and frequency with the input which has the largest amplitude by sweeping across a predetermined range of frequencies and allowing the phase-lock loop to operate only when a predetermined amplitude is exceeded.
Type:
Grant
Filed:
July 23, 1974
Date of Patent:
June 9, 1987
Assignee:
The Marconi Company Limited
Inventors:
John T. Floyd, Christopher D. Huggett, Michael A. Jones, John R. G. Woods
Abstract: A dual frequency band radar detector responds to radar signals occurring within either of a first or a second range of frequencies. The detector comprises one or more antennas for receiving radar signals including radar signals occurring within the first and second ranges of frequencies. At least one pilot signal at a predetermined frequency is produced for modulating the received radar signals. The modulated signals produced in response to received signals in either of said first range of frequencies or said second range of frequencies are isolated. A detector is coupled in circuit for detecting the one pilot signal in these isolated and modulated signals and a control output signal is produced responsive to the detected pilot signal. Accordingly, the presence of a control output signal indicates the reception of radar signals occurring within at least one of the first and second ranges of frequencies.
Abstract: A frequency-agile source of microwave frequency signals is shown to include: a voltage-controlled oscillator operating within a band of microwave frequencies; a crystal-controlled oscillator operating at a frequency lower than the band of microwave frequencies and producing harmonics within such band; a phase detector having samples of the signals out of the crystal-controlled oscillator and the voltage-controlled oscillator applied as input signals; and a shaping amplifier receiving the output signal of the phase detector to provide a control signal related to the phase difference between the signal out of the voltage-controlled oscillator and the harmonic of the crystal-controlled oscillator nearest to the frequency of the voltage-controlled oscillator.