1893 results about "Side lobe" patented technology

An antenna system that includes a directional antenna designed to reduce the occurrence of side lobes, thus reducing the possibility of interference with other radio frequencies is disclosed. The directional antenna includes an antenna member and a reflecting tube. The reflective tube is sleeved over the antenna member. The reflective serves to block unwanted radial side lobes. The directional antenna can also include provisions that assist in suspending the antenna member within the reflective tube.

Disclosed is a lens antenna comprising a dielectric lens consisting of a collimating part and an extension part, and an antenna element. The extension part of the lens comprises a substantially flat surface crossed by the axis of the collimating part, and the antenna element is rigidly fixed on the surface. The antenna element is formed by a hollow waveguide and comprises a dielectric insert with one end thereof adjacent to said surface; the size of the radiating opening of the waveguide is determined by the predefined width of the main beam and by side lobe levels of the radiation pattern of the lens antenna. The technical result of the invention is an increase in realized gain value due to the use of a waveguide antenna element with a dielectric insert, which provides impedance matching in a wide frequency bandwidth. The present invention can be used in radio-relay point-to-point communication systems, e.g. for forming backhaul networks of cellular mobile communication, in car radars and other radars, in microwave RF tags, in local and personal communication systems, in satellite and intersatellite communication systems, etc.

The present invention relates to confocal self-interference microscopy. The confocal self-interference microscopy further includes a first polarizer for polarizing reflected or fluorescent light from a specimen, a first birefringence wave plate for separating the light from the first polarizer into two beams along a polarizing direction, a second polarizer for polarizing the two beams from the first birefringence wave plate, a second birefringence wave plate for separating the two beams from the second polarizer into four beams along the polarizing direction, and a third polarizer for polarizing the four beams from the second birefringence wave plate, in the existing confocal microscopy. Optic-axes of the first and second birefringence wave plates exist on the same plane, optic-axes of the first and second birefringence wave plates are inclined from an optical axis of the entire optical system at a predetermined angle, and self-interference spatial periods of the first and second birefringence wave plates are different from each other.

An efficient, low-loss, low sidelobe, high dynamic range phased-array radar antenna system is disclosed that uses metamaterials, which are manmade composite materials having a negative index of refraction, to create a biconcave lens architecture (instead of the aforementioned biconvex lens) for focusing the microwaves transmitted by the antenna. Accordingly, the sidelobes of the antenna are reduced. Attenuation across microstrip transmission lines may be reduced by using low loss transmission lines that are suspended above a ground plane a predetermined distance in a way such they are not in contact with a solid substrate. By suspending the microstrip transmission lines in this manner, dielectric signal loss is reduced significantly, thus resulting in a less-attenuated signal at its destination.

A radar system has different modes of operation. In one mode the radar operates as a single-input, multiple-output (SIMO) radar system utilizing one transmitted signal from one antenna at a time. Codes with known excellent autocorrelation properties are utilized in this mode. At each receiver the response after correlating with various possible transmitted signals is measured in order to estimate the interference that each transmitter will represent at each receiver. The estimated effect of the interference from one transmitter on a receiver that correlates with a different code is used to mitigate the interference. In another mode, the radar operates as a MIMO radar system utilizing all the antennas at a time. Interference cancellation of the non-ideal cross correlation sidelobes when transmitting in the MIMO mode are employed to remove ghost targets due to unwanted sidelobes.

Digital beamforming is provided for use with electronically scanned radar. In an aspect, the present invention provides enhanced sensitivity, wide angle or field of view (FOV) coverage with narrow beams, minimized number of receivers, reduced sidelobes, eliminated grating lobes and beam compensation for target motion. In an aspect, the present invention employs a uniform overlapped subarray feed network, a time multiplexed switch matrix, and a restructured digital signal processor. Antenna channels share a receiver, rather than maintain a dedicated receiver for each antenna element, as in conventional systems. In an aspect, Doppler/frequency filtering is performed on each antenna element or subarray output prior to digital beamforming. Further, Doppler compensation is employed following Doppler/frequency filtering, followed by digital beamforming.

A low sidelobe beam forming method and dual-beam antenna schematic are disclosed, which may preferably be used for 3-sector and 6-sector cellular communication system. Complete antenna combines 2-, 3- or -4 columns dual-beam sub-arrays (modules) with improved beam-forming network (BFN). The modules may be used as part of an array, or as an independent 2-beam antenna. By integrating different types of modules to form a complete array, the present invention provides an improved dual-beam antenna with improved azimuth sidelobe suppression in a wide frequency band of operation, with improved coverage of a desired cellular sector and with less interference being created with other cells. Advantageously, a better cell efficiency is realized with up to 95% of the radiated power being directed in a desired cellular sector.

A dual-polarization wireless base station antenna that implements vertical electrical downtilt and sidelobe reduction using beam steering circuit that includes a variable power divider and a multi-beam beam forming network. The variable power divider includes a single adjustable control element to divide an input voltage signal into a pair of complimentary amplitude voltage drive signals that exhibit matched phase and constant phase delay through the variable power divider. The beam forming network is configured as a double-sided, edge-connected microstrip module mounted to a main panel, which support the antenna elements in a vertical column organized into sub-arrays in a manner that implements sidelobe reduction. The power distribution network connecting the beam steering network to the antenna elements implements beam tilt bias and sidelobe reduction through coordinated phase shifting implemented through transmission media trace length adjustment.

A method and apparatus for detecting a spread spectrum signal is described. Signals can be detected using correlation techniques. When a signal is detected, declaring of signal presence is inhibited for offsets of signal parameters from the parameters of the detected signal, where the offset corresponds to a known sidelobe of the spreading code. This helps to reduce false detections caused by sidelobes of the spreading code.

An improved communication system and method employing an actively controlled antenna array architecture is disclosed. The array contains a plurality of driven radiating elements that are spatially arranged having a pair of radiating elements fed with an RF signal predistorted so as to provide a controlled variation of the antenna array's elevation radiation pattern. High power amplifier (PA) efficiency is maintained by adaptive predistortion, coupled to each high power PA, while providing beam tilt and side lobe control.

A microwave imaging system suppresses sidelobes in a microwave image captured using a sparse antenna array using an illumination system that operates in two different illumination modes. The antenna array including subarrays of antenna elements arranged in a sparse geometry to form complementary subarray patterns. The illumination system operates in a first mode to transmit microwave illumination to both of the complementary subarray patterns of the antenna array and receive reflected microwave illumination from both of the complementary subarray patterns of the antenna array to produce a first receive signal. The illumination system further operates in a second mode to transmit microwave illumination to a first one of the complementary subarray patterns of the antenna array and receive reflected microwave illumination from a second one of the complementary subarray patterns of the antenna array to produce a second receive signal. Sidelobes are suppressed using a linear combination of the first and second receive signals.

A diffraction grating of non-uniform strength is introduced into an optical waveguide by modulating its width. The waveguide may be fabricated using one of several planar processing techniques. Varying the size, position, and/or thickness of the grating teeth provides the desired variation of grating strength. Certain functional variations of grating strength suppress side-lobe levels in the grating reflection and transmission spectra. This process, termed apodization, is necessary for precise wavelength filtering and dispersion compensation. If desired, different periodicity gratings can be introduced in each side of the waveguide, multiple periodicities can be superimposed, the grating can be angled with respect to the waveguide, and the grating period and phase can be varied.

The invention provides transducer arrays which are capable of outputting sound beams having a relatively constant width, and with minimal sidelobes, across a range of frequencies. This is achieved by utilising one or more digital signal modifiers within the signal path between the input sound signal and the array of transducers. Variable window functions are also disclosed.

The invention discloses a multi-target detection method based on short-time Fourier transform and fractional Fourier transform, which belongs to the technical field of the radar target detection. The method comprises the following steps that the short-time Fourier transform is firstly used for conducting the primary detection on a signal, then a binaryzation method is used for processing a primary detection result, phase position of the signal is kept in the processing, the fractional Fourier transform is used for detecting a signal after being restored by the short-time Fourier transform, by adopting multiple methods for combined processing, advantages of overcoming phenomenon that a strong signal side lobe presses a weak signal main lobe, improving the signal-to-noise ratio of the signal to be detected, and solving the problem of the large false alarm possibility which is caused by adopting traditional method to detect the signal at the low signal-to-noise ratio can be realized; and meanwhile, an image contrast method and a gradual elimination method are adopted, multiple strong signals and weak signals with different or identical frequency modulation rates can be detected by utilizing the space and power strength information of the signal, so that the detection probability and the calculation efficiency can be further improved, easiness in project realization is realized, and the method is worth of being adopted and popularized.

A system and method for increasing the performance of a satellite communication system by using a multivariate analysis approach to optimize the pointing of the boresight of a satellite-mounted antenna. Optimizing the pointing of the boresight of the antenna minimizes sidelobe generation, and thus Co-Channel Interference (CCI) in geographic areas served by the system. By minimizing CCI, the overall system performance of the communication system is optimized. To optimize the pointing of the boresight of the antenna, the overall performance of the satellite communication system is determined, and the boresight of the antenna is iteratively repointed in the direction of increasing system performance until the optimized boresight pointing is determined. Alternatively, the frequency re-use plan of the satellite communication system may be analyzed to determine a high density cell region and the boresight may be pointed to the high density cell region.

A high resolution and high data rate spot grid array printer system is provided, wherein an image is formed by scanning spot-grid array of optical beams across a substrate layered with a resist. High resolution is achieved by apodizing the optical beams to provide a narrower main lobe. Unwanted recordation of side lobes upon the substrate is prevented by assuring that the side lobes do not include energy above the threshold of the resist, using a memoryless resist, and by using a slanted and interleaved scan pattern adapted for use with the spot-grid array pattern and the memoryless characteristic of the resist.

The invention discloses a four-dimensional antenna array based on a single-pole multi-throw switch. The basic structure of the four-dimensional antenna array comprises an antenna unit, a phase shifter, a variable amplitude fader, the single-pole multi-throw radio-frequency switch, a power divider, an FPGA (Field Programmable Gate Array) circuit board and a filter. The greatest innovation of the invention is that the single-pole multi-throw switch replaces a single-pole single-throw switch in a traditional four-dimensional antenna array. Compared with the original four-dimensional antenna array based on the single-pole single-throw switch, a small amount of radio-frequency switches are only used in the structural design proposed provided by the invention; and in the combination of low side lobes or multi-beam directional diagrams, the gain of an antenna is greatly improved, the transient directivity factor of the antenna and the stability of the gain in the modulation period are not changed. The dimension of the antenna is changed reasonably, so as to constitute other specific embodiments of the invention. The four-dimensional antenna array is used for wireless communication and is also used in a radar system.

To suppress adverse effects caused by side lobes of an antenna array when an AWV to be used for communication is determined based on a transmission/reception result of a training signal. A first transceiver generates a fixed beam pattern and transmits a training signal. In that state, a second transceiver receives the training signal while scanning for the main beam direction, and thereby determines a plurality of direction of arrivals (DOAs). Next, the second transceiver receives the training signal in a state where the signal receptions from the plurality of DODs are restricted one by one (e.g., a null direction or a direction close to the null direction is fixed in the DOA), and calculates the change of the signal characteristics from that obtained in the first reception. The transceivers obtain and use at least one AWV having the main beam direction or a sub-beam direction close to the main beam pointing to one of the plurality of DOAs except for the DOA for which the change is lower than a predefined threshold.