Hans Hellsten has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
Abstract: A radar device (100) comprising transmit and receive parts, and a control unit (CU). The transmit part includes means (WG) for generating a signal within a certain band, and the receive part comprises a filter (AAF), an AD-converter (ADC) and a Fourier transform unit (FFT1). The transmit part generates a group of signals, each having a first bandwidth between a first and a second frequency, in such a way that a larger bandwidth (B1-B4) is covered by the group. The receive part is open over said larger bandwidth (B1-B4) during reception of each signal in said group, and the transmit part comprises means (PAD, FFT2) for creating FFT-copies of the received signals and means (CONJ) for creating conjugates of said copies. The receive and transmit parts comprise means (EXTR) for extracting data from the FFT from the first bandwidth covered by a received signal, and the radar device comprises means (DIFF) for correlating said extracted FFT-data.
May 31, 2005
May 21, 2009
Hans Hellsten, Nils Dagas, Torbjorn Elfstrom
Abstract: A method of for processing signals in a radar system is shown comprising an antenna system having at least two antenna elements, a beam forming arrangement (ABF_RX, ABF_TX) for selectively steering the directivity of the antenna system in a given selected direction, the directivity of the antenna system having a main lobe in the selected direction and a back lobe (BL) in another direction and of a lower magnitude than the main lobe. By utilizing various scale and subtract processing both noise levels and ghost signals can be considerably reduced. A SAR radar apparatus has moreover been shown.
Abstract: The present invention can be summarized by use of a diffraction limited SAR giving large integration angle and a short depth of field which gives that energy from underground targets is focused independently at different depths to enable 3d imaging. The radar device according to the invention should be implemented by considering the following parameters: Choice of the appropriate illumination geometry, i.e. elevation angle ?, and the appropriate use of low frequency diffraction limited SAR processing to obtain 3D imaging, and the choice of an appropriately low radar frequency.
Abstract: A filter scheme for broadcast interference cancellation that is computationally efficient and numerically robust Airborne Low Frequency Synthetic Aperture Radar (SAR) operating in the VHF and UHF bands has been shown. At least interference Doppler filtering or interference cancellation is utilised. The interference cancellation involves prediction of the interference for each particular reception interval of mixed interference and radar ground response. This prediction is then coherently subtracted from the incoming signal.
Abstract: The present invention relates to a system for using signals scattered by targets to determine position and velocity for each of the targets and comprises a set of transmitters and receivers of electromagnetic or acoustic signals, said transmitters and receivers dispersed to known points. Each pair of transmitter and receiver, monostatic or bistatic, is named a measuring facility. The ranges of the transmitters are chosen so that a target at an arbitrary point within the position space can be measured via scattering in the target by at least four measuring facilities. For each measuring facility, target detection occurs with constant false alarm rate in the form of probabilities over resolution cells with regards to range and Doppler velocity and conceivable targets are placed in a 2-dimensional linear space belonging to the measuring facility.
Abstract: The present invention relates to a system for using signals scattered by targets to determine position and velocity for each of the targets and comprises a set of transmitters and receivers of electromagnetic or acoustic signals, said transmitters and receivers dispersed to known points. Each pair of transmitter and receiver, mono-static or bi-static, is named a measuring facility. The ranges of the transmitters are chosen so that a target at an arbitrary point within the position space can be measured via scattering in the target by at least four, but preferably many more, measuring facilities.
Abstract: A Synthetic Aperture Radar (SAR) system and method capable of detecting moving targets which includes a platform that moves over a number of objects, such as a ground surface, and supports radar equipment which reproduces the objects by means of a fast backprojection synthetic aperture technique via at least two antennas without requirement as to directivity or fractional bandwidth. The imaging process is divided into three steps which are carried out in a determined order, the steps and the order being formation of sub-aperture beams at one speed, performing clutter suppression, and detection of moving targets.
November 2, 2000
Date of Patent:
February 11, 2003
Mats Peterson, Hans Hellsten, Lars Ulander
Abstract: The present invention relates to a radar system which comprises a platform which moves over a number of objects. The number of objects can be very large and the objects can appear in the form of, for example, a ground surface. The platform supports radar equipment which reproduces the objects by means of synthetic aperture technique (SAR) via at least one antenna without requirements as to directivity or fractional bandwidth. Moreover, the movement of the platform is, during the recording of data for a SAR image, essentially rectilinear and uniform. The invention is characterized mainly in that it comprises a signal-processing device which records received radar echoes from each transmitted radar pulse and records or calculates the position of the used antenna or antennae, and which calculates a one-parameter quantity of two-dimensional SAR images as a function of two image co-ordinates where the parameter is the relative speed. Here use is made of the fact that each object, i.e.
Abstract: The invention relates to a radar station placed on the surface of the earth, and to a radar system comprising at least two such radar stations.
The signal-processing equipment of the radar stations is adapted, at each point of time, to calculate probabilities of target positions and radial target velocity in relation to each individual radar station, based on the signals emitted and received by this station. These calculated values are associated over time, giving cumulative probability measures for target positions and radial velocities in relation to each individual radar station.
By providing a system of at least two radar stations, it is possible to calculate the position of a target by associating target positions, such as they are perceived by the different radar stations, with each other by an association of characteristic movements of the target. This is done without having to synchronize the stations.
Abstract: The present invention relates to an ultra wide band coherent radar system assessing the Doppler shift of the returned radar echoes, which radar system optimises the radio interference discrimination capability. The radar system comprises a control unit by which the transmit-receive process is partitioned into a number of consecutive sub-processes each of which consists of transmission followed by reception of a signal having a relative bandwidth of a fraction of an octave and where the received signals from the different narrow band transmissions are used to reconstruct broad band radar data by pulse compression techniques. Further, the control unit is arranged to determine the recurrence time, i.e. the time lapse between two consecutive transmissions, of a narrow band signal for a certain frequency step to be approximately inversely proportional to the frequency of this step and higher or equal to the Nyquist rate with respect to the Doppler bandwidth at this frequency.
Abstract: A method of improving data obtained by radar by interpolation over frequency bands jammed by narrow-band interference, at which the following steps (A)-(J) are carried out. (A) It is determined what frequency values are affected by narrow-band interference. (B) Every radar return which is continuously connected in time and represented by a time-discrete real or complex signal f(t.sub.i), containing N sample, i=1, 2, . . . , N, is Fourier-transformed into a frequency-discrete function F(.omega..sub.i), given by N sample. (C) A series of integers N.sub.1, N.sub.2, . . . , N.sub.M is fixed, such that 1.ltoreq.N.sub.1 <N.sub.2 < . . . <N.sub.M <N. (D) The signal processing device sets F.sub.k (.omega..sub.i)=H.sub.k (.omega..sub.i) within intervals having narrow-band interference. (E) H.sub.1 (.omega..sub.i) is equated to 0 and H.sub.k (.omega..sub.i) for k.gtoreq.2 is constructed according to the following steps (F)-(H). (F) F.sub.k-1 (.omega..sub.
Abstract: A signal processing apparatus for use in SAR radar. The signal processing apparatus uses a new method of processing SAR images, primarily for wide band SAR. The new method is based on the numerical unfolding of differential equations along the flight path. The method makes motion compensation possible and can be used along a curved flight path and irrespective of the acceleration of the aircraft. Moreover, the method makes real time processing possible.