USA as Represented by Secretary of the Navy

William P Huntley

David J Swanick

Kichul Cho

Jeffrey C Gremillion

John D Borla

The system and method for calibrating a signal detection threshold circuit is used in a radio frequency (RF) receiver, such as a in an early warning radar (EWR) system, in which a signal detection threshold circuit rejects signals below a predetermined threshold setting and prevents noise signals from causing false alarms. The system and method include setting an initial threshold setting and receiving noise signals in one or more channels. A threshold comparison circuit rejects noise signals below the threshold setting, and a pulse repetition frequency (PRF) detection circuit detects noise pulses above the threshold setting and determines the PRF. An automatic threshold determiner and setter determines whether the PRF has reached a predetermined frequency (e.g., 400 kHz) and lowers the threshold setting until the predetermined frequency is reached. When the predetermined frequency is reached the threshold setting is stored as a noise measurement. The process is repeated until a plurality of noise measurements are made in each signal channel, and the average value of the noise measurements are used to determine the calibrated threshold setting. A calibration indicator provides an indication of whether each of the signal channels has been properly calibrated.

System and method for calibrating a signal detection threshold circuit

A multi-function radio frequency (RF) signal warning system detects different types of RF signals, such as radar signals, provided in various RF bands and provides an indication of the type of radar signal and the RF band. The system detects pulsed radar signals having different pulse repetition frequency (PRF) ranges as well as high duty cycle radar signals and continuous wave radar signals. The system includes a receiver processor that detects the radar signals, video amplifies the radar signals with baseline correction, and processes the radar signals to determine the type of radar signal, e.g., the RF band and PRF range. The receiver processor generates audio and visual control signals and transmits the control signals to one or more remote units. The remote units receive the audio control signals and generate an audible alarm. The remote units receive the visual control signals and illuminate one or more visual indicators, such as LEDs, that indicate the RF band of the radar signal and the PRF range of the radar signal. The remote units can also select one or more bands in which the audio alarm is enabled or disabled. One of the remote units further controls testing and calibration functions in the multi-function RF signal warning system.

Multi-function radio frequency signal warning system

A ten db coupler receives an RF input signal and transmits an attenuated signal through a wideband/narrow band select switch to an RF amplifier. The signal is next processed through an RF amplitude detector. A comparator then receives the signal and generates a pulse in response to signals exceeding a predetermined threshold. A pulse stretcher then eliminates excessive pulses due to noise or other signal oscillations that exceeded the comparator's threshold. A circuit comprising a retriggerable monostable and an OR gate determine if the pulses received exceed a pulse repetition frequency threshold. A ripple counter than eliminates unwanted signals by resetting if a predetermined number is not reached in a specified time. A unique audio signal is then generated if the desired signal is detected. The output signal is audible even though the input signal is of a frequency above the normal hearing threshold. Also a visual signal is provided by a light emitting diode.

High pulse repetition frequency radar early warning receiver

A receiver selects and amplitude demodulates an RF signal from one of a pality of directional antennas. The demodulated signal is then delayed to put it in time synchronism with the same signal information from an omnidirectional antenna. A signal is then generated of the peak pulses of the demodulated signal when the pulses are in time synchronism with pulses from the omnidirectional antenna. A control indicator receives the peak pulses along with periscope bearing signals and ship's heading signals and gives an r,.THETA. display of the amplitude of the RF signal selected from the directional antenna at the periscope true bearing angle.

Semi-automatic direction finding set

An RF multiplexer divides an incoming signal from an RF antenna into disce frequency bands. Each frequency band has its own separate circuit on separate lines to operate on the frequency band and determine if a radar signal is present or if only noise is present on the line. This is done by comparing the incoming signal for magnitude with a DC signal that is generated within the circuit and is proportional to the noise within the frequency band. An indication that any of the signals within the discrete frequency bands exceed the DC signal generated within the same band results in an alarm indication.

Unidirectional amplitude sensitive noise riding threshold circuit

A linear, analog, synchro control differential transmitter for implementing he common synchro CDX function whereby a scaled linear analog voltage is used as input instead of a mechanical shaft angular displacement. Alternate synchro functions of CT and CX that the invention implements are also disclosed.

Analog electronic control differential transmitter

Automatic thresholding multichannel digital radar early warning system

A scan oscillator and a Pulse Repetition Frequency (PRF) oscillator with associated analog and digital circuits provide drive signals for two different RF PIN diode attenuators. When driven by a portable Gunn Diode Oscillator or other microwave source RF is generated that provides main lobe and adjustable side lobe radar signals to a directional microwave antenna. This output signal has adjustable scan rate, beam width, PRF, pulse width, and side lobe level and is self-contained in a package measuring 83/8.times.73/8.times.3 inches. The system allows 'on the sail' testing for periscope mounted Direction Finding Systems.

Portable radar simulator with adjustable side lobe generator

A system for transmitting low level analog signals wherein the analog sigs are converted into frequency modulated light amplitudes which are transmitted by means of an inexpensive fiber optic bundle, and the transmitted modulated light is demodulated at the receiving end to obtain an exact replica of the input signals. The system enables one to maintain a large amplitude dynamic range using an inexpensive photo-transistor.

Growing community of inventors

Old Lyme, CT, United States of America

William P Huntley