Communications: directive radio wave systems and devices (e.g. – Radar ew – Detection of surveilance
Reexamination Certificate
1999-07-01
2001-01-23
Pihulic, Daniel T. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Radar ew
Detection of surveilance
C342S013000, C342S195000
Reexamination Certificate
active
06177902
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field Of The Invention
The present invention relates to radio frequency signal warning systems and more particularly, to a multi-function radar early warning system that provides an indication and warning of threats based on current and projected future radar systems.
(2) Description Of The Prior Art
Radar is commonly used to detect and locate objects or targets by radiating electromagnetic energy and using the echo or reflection of the electromagnetic energy from the object or target. In general, a typical radar system transmits one or more radio frequency signals to be reflected from objects in the environment. The radar system then receives and analyzes the reflected signals to determine the location or distance to the objects.
Different types of radar systems have used different types of radio frequency signals having a number of different frequency ranges or bands. For example, in a pulsed radar system, the transmitter transmits radio frequency signal pulses that are reflected from objects and then received to determine the distance to the object and the location of the object. In a continuous wave type radar system, a continuous radio frequency signal is transmitted. When the continuous wave is reflected from a moving object, the frequency of the wave changes, thereby providing an indication of moving objects in the environment.
Early warning radar (EWR) systems are commonly used by the military to detect and provide a warning of radar signals and possible threats posed by the vessels transmitting the radar signals. For example, underwater vessels, such as submarines, include periscope antennas that receive various types of radar signals on one or more channels.
Some problems encountered with existing EWR systems include the inability to detect a wide range of different types of radar signals. The existing EWR systems also do not provide an adequate indication of the type of radar signal that was detected.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a multi-function radio frequency signal warning system that provides an indication and warning of threats based on current and projected future radar systems using audible and visual indications of a number of different types of radar signals.
The present invention features a radio frequency (RF) signal warning system that receives one or more RF signals in one or more RF bands. The RF signals may include at least one pulsed RF signal having a pulse repetition frequency (PRF). The RF signals are amplified and conditioned to produce one or more amplified and conditioned RF signals. The amplified and conditioned RF signals are envelope detected to produce corresponding envelope detected RF signals. The corresponding envelope detected RF signals are video amplified to produce corresponding video bandwidth signals having the same pulse repetition frequency (PRF) as the corresponding pulsed RF signals. The video bandwidth signals are processed to determine the PRF range of the pulsed RF signal and to generate and transmit audio and visual control signals to one or more remote units that provide audible alarms and a visual indication of the RF band and the PRF range of the detected RF signals. The RF signal warning system also preferably receives, detects and digitally processes continuous wave (CW) RF signals.
In the preferred embodiment, the RF signal warning system combines the amplified and conditioned RF signals to generate a high amplitude RF signal that is detected and processed with the RF signals. If the high amplitude RF signal exceeds a predetermined high amplitude threshold setting, the system provides a high amplitude audible alarm and a visual indication of the high amplitude signal.
The preferred embodiment of the present invention features a receiver processor used in the RF signal warning system and having a plurality of channel inputs for receiving a plurality of amplified and conditioned RF signals in different RF bands. The receiver processor includes a plurality of RF detectors for envelope detecting each of the amplified and conditioned RF signals to produce the envelope detected RF signals. A plurality of video amplifiers and baseline correction circuits are coupled to the respective RF detectors for video amplifying and baseline correcting each of the envelope detected RF signals to produce the video bandwidth signals. The video bandwidth signals corresponding to pulsed RF signals have the same PRF as the corresponding pulsed RF signals. A processor is coupled to each of the video amplifiers and baseline correction circuits for processing the corresponding video bandwidth signal to determine the RF bands and the PRF range of the pulsed RF signals. In response to determining the RF bands and PRF range of the pulsed RF signals, the processor generates and transmits the audio and visual control signals.
The preferred embodiment of the processor includes a plurality of PRF detectors for receiving the video bandwidth signals and detecting the PRF range of the pulsed RF signals and a microprocessor, coupled to the PRF detectors, for receiving PRF information from the PRF detectors and for generating the audio and video control signals based upon the PRF information. At least one serial transceiver is coupled to the microprocessor for transmitting and receiving control and activity signals to the remote unit.
A plurality of video threshold circuits are preferably coupled to the respective video amplifiers and baseline correction circuits for comparing the video bandwidth signals to a predetermined threshold amplitude and for rejecting pulses in the video bandwidth signals lower than the predetermined threshold amplitude. A plurality of pulse stretching circuits are coupled to the respective video threshold circuits for stretching pulses of the video bandwidth signals.
The receiver processor also preferably includes a plurality of continuous wave signal amplifiers coupled to respective RF detectors for amplifying continuous wave RF signals. An analog-to-digital converter is coupled to the continuous wave signal amplifiers for digitizing the continuous wave RF signals to be processed by the microprocessor.
The present invention also features remote units including an audio control signal receiver for receiving audio control signals and a speaker for generating audible alarms corresponding to the RF signals. Each of the remote units further include a serial transceiver for receiving visual control signals from the receiver processor and a microprocessor for processing the visual control signals to determine characteristics of the RF signals detected by said system and for generating indicator control signals. A plurality of RF signal indicators are responsive to the indicator control signals for providing visual indication of the characteristics of the detected RF signals.
The RF signal indicators preferably include a set of activity indicators for indicating RF signal activity in at least one RF band. RF signal activity includes an indication of the PRF range of the pulsed RF signals in the RF bands that are above the audio frequency range. RF signal activity can also include an indication of continuous wave (CW) RF signals. The remote units also preferably include one or more band selection switches for enabling and disabling audible alarms in selected RF bands and an audio disable switch for disabling the high amplitude audible alarm.
One embodiment of the remote unit can include an analog/digital audio selector for selecting whether the audible alarm for signals with PRF in the audio frequency range follows the RF signal amplitude (analog) or is a fixed amplitude level as long as the signal threshold is broken (digital). One embodiment of the remote unit can also include a calibration offset switch for manually offsetting the threshold amplitude set when in the auto calibration mode.
REFERENCES:
patent: 5010341 (1991-04-01), Huntley et al.
Borla John D.
Cho Kichul
Huntley William P.
Swanick David J.
Gauthier Robert W.
Lall Prithvi C.
McGowan Michael J.
Pihulic Daniel T.
The United States of Americas as represented by the Secretary of
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