Abstract: An FMCW radar transmits a signal the frequency of which repeatedly sweeps upwards and downwards at a rate .alpha.. Any target returns are applied to a mixer (6) which is also supplied with a sample of the transmitted signal. During each sweep the mixer output signal is therefore a beat frequency signal the frequency components of which correspond to respective targets. The spectrum of the beat frequency signal is analysed by an FFT-calculating arrangement (16) and the result is applied to a data processor (18) which calculates the ranges of the targets. The constant of proportionality between beat frequency and range is inversely proportional to .alpha., which is subject to uncertainty. In order to resolve this uncertainty, or correct .alpha. to the required value, the velocity of a given radially moving target is calculated in two different ways: from the perceived Doppler shift and from the rate of charge of the beat frequency component due to that target, only one of these being a function of .alpha..

Abstract: The present invention provides a microwave vehicle detector which includes a transceiver for transmitting microwave energy into a desired target area and for receiving reflections of this microwave energy from vehicle movement in this target area. The transceiver includes first and second diodes for enabling the microwave vehicle detector to determine the direction of vehicle movement relative to the position of the microwave vehicle detector. In this regard, these diodes are balanced, such that a predetermined phase difference will be produced between the doppler shift signals generated by these diodes. This phase difference is analyzed by a microprocessor to determine the speed and direction of the vehicle being detected.

Abstract: A unit for detecting a moving person or object by means of doppler frequency shift. The unit comprises a microwave circuit board (1) accommodating an oscillator and a mixer, and an antenna board (2) carrying transmit (8) and receive (9) patch arrays. In the assembled unit the two boards (1,2) are disposed adjacent one another. Coupling between the microwave circuit and the antenna arrays is achieved by two slots (6,11) resonant at the oscillator fundamental frequency and formed in a ground plane (5) on the microwave board (1). Feed striplines (7,10,12) on the two boards (1,2) lie orthogonal to the slots (6,11) and are terminated in T-sections (15,14). The stripline/slot arrangement suppresses emission at the oscillator second harmonic frequency. The antenna board (2) has no electrical connection to the microwave circuit, enabling the radiated beam shape to be changed by simply replacing the antenna board with one having a different patch array pattern.

Abstract: False target (reverberation, clutter, etc.) detection is suppressed in an echo ranging system (sonar or radar) in which target velocity and range are measured using a composite Doppler invariant-like signal having at least two segments, such as are present in a "rooftop" or "vee" HFM signal, such composite signal having an ambiguity function with two or more ridge lines of different slopes that intersect along the zero-velocity time axis. A bank of matched filters provides a distribution of outputs which has an ambiguity function-like character with intersecting pairs of ridge lines, the intersecting points of said pairs characterizing the range and velocity of the echo returns. This distribution is adjusted so that the intersecting ridge lines of each pair have equal and opposite slopes with respect to the time axis. In particular, fixed reverberators, which would have ridge lines intersecting on the zero-velocity time axis, would be symmetrical about this axis.

Abstract: A Doppler control circuit for a CW or pulse Doppler radar system for monitoring not only the phase shift between echo signals from several targets but also the amplitude difference between the several targets and to further tune the radar to a particular target among one or more targets from which echo signals return. The control circuit can be used in state of the art CW or pulse Doppler type radar systems. In a further system, a special circuit is provided for conditioning selected portions of the Doppler frequency spectrum to attenuate or de-emphasize portions of the echo signal corresponding to selected targets in the radar system environment, such as rain or stationary wayside objects, in order to give such echo signals less weight in determining roadway hazards.

Abstract: A Doppler control circuit for a CW or pulse Doppler radar system for monitoring not only the phase shift between echo signals from several targets but also the amplitude difference between the several targets and to further tune the radar to a particular target among one or more targets from which echo signals return. The control circuit can be used in state of the art CW or pulse Doppler type radar systems. In a further system, a continuously generated radar signal is repeatedly transmitted at different frequencies in time division fashion to define a succession of transmit and receive frames. The receive frames are divided into a plurality of time interval windows with selected windows being used to detect received signals at the different frequencies. The remaining windows can be used for subsystems of the radar system.

Abstract: A microwave radar signal is generated (16) and split by a circular (20). A phase shifter (24) introduces a plurality of phase shifts into a first part of the split signal which is then transmitted (36) by antenna (34). A like plurality of phase shifts are introduced by the phase shifter into the return signal (40) from the target. The circulator delivers the phase shifted return signal and the leakage signal from the circulator to a mixer (44) which generates an i.f. signal output at the doppler frequency. The i.f. signal is amplified (46l ), filtered (54), counted (58) per unit of time and the result displayed (62) to provide indications of target sense and range rate. An oscillator (50) controls rate of phase shift in the transmitted and received signals and provides a time base for the counter. The phase shift magnitude increases may be continuous and linear or discrete functions of time.

Abstract: A radar signal processor and methods of operating same for determining the differential sideband power of reflected energy received in a frequency window by a radar receiver, which processor contains a generator of orthogonal signals, a mixer for multiplying these orthogonal signals times quadrature signals, an integrating circuit for integrating the mixer outputs over a predetermined time interval, a multiplier for multiplying the integrals from the integrating circuit together, and a circuit to average the products from the multiplier over time.

Abstract: A multiple parameter doppler radar system transmits a radar signal which is alternated between a first and second frequency toward a target. The doppler shifted signals reflected from the target are received and processed to derive a pair of doppler signals related respectively to the first and second frequency signals. The frequency of one of the doppler signals is measured and scaled to a target speed. The phase magnitude between the two doppler signals is measured and scaled to a target range. The phase lead/lag relationship of the two doppler signals is detected to determine if the target is moving toward or away from the radar system. The components of the system are controlled by a microprocessor which is programmed to perform quality determinations on the data derived from the signals to assess the reliability of the data even in a multiple target environment prior to displaying the parameters of target motion.

Abstract: Audio frequency Doppler signals output from a radar are encoded and presented to left and right speakers of a headset. The Doppler signals are encoded so that the auditory effect produced by sounds emanating from the left and right speakers are perceived by an operator as originating from a particular location in space. In a preferred embodiment in-phase and quadrature Doppler signal outputs from a coherent radar couple through an optional phase shift to the left and right speakers. Sounds having phase differences dependent upon whether a target is approaching or receding result. The operator hears these sounds and perceives the sounds as being located toward the left or right.