Grating Lobe Suppression Research Articles

Adaptive Grating Lobe Suppression in Ultrasound Imaging

Adaptive grating lobe suppression is provided. Received ultrasound data is measured, compared or otherwise processed to determine the presence of grating lobe energy. A further process is then altered as a function of the level of grating lobe energy. In one embodiment, the adaptive grating lobe suppression is implemented in the receive beamformer. Data representing a virtual element is formed as a normalized sum of data from adjacent sparse elements. The data from the adjacent elements is correlated to determine the presence of grating lobe energy as a function of the amount of shift associated with the peak correlation. A phase shift is applied to the data representing the virtual element where sufficient grating lobe energy is determined. In another embodiment, an amount of grating lobe energy is measured by comparing data from prior to a filter with filtered data. The filter is selected to isolate main lobe energy from grating lobe energy. A gain is modulated as a function of any detected grating lobe energy or filtered or unfiltered data is selected for further processing.

Optimum Spatial Arrangement of Array Elements for Suppression of Grating-Lobes of Radar Cross Section

A new method to optimize the radar cross section (RCS) for array antennas is presented. A previous work has reported that the RCS of an array is the product of the array RCS factor multiplying the element RCS factor. In this method, the strong scattering from an equally spaced array can be considerably reduced at some certain directions by optimizing the array RCS factor. With the proposed method, the optimized array will scatter waves at a much lower level against prescribed incident directions. In order to illustrate the validation of the proposed method, a planar dipole array and a linear array with bowtie antenna elements are designed and optimized by the proposed method. The numerical and simulated results show that the RCS pattern of equally spaced array generally has some grating-lobes at some certain directions. Hence, the proposed method is applied to suppress these grating-lobes to design a low RCS array. The algorithmically optimized and simulated results validate that the proposed method can help to suppress these grating-lobes.

77 GHZ MILLIMETER WAVE ANTENNA ARRAY WITH WILKINSON DIVIDER FEEDING NETWORK

A 77GHz microstrip antenna array with a small surface providing high side and grating lobe suppression is presented. This may serve as a starting point for 77GHz automotive radar applications. Multiple Wilkinson dividers guarantee both impedance matching at the input port (TX) as well as low return loss for the incoming (RX) signal. Phase shifting is done by adjusting the level of the Wilkinson dividers or by meandered sections of transmission line. The in∞uence of the radiation caused by the feeding network is analyzed and the absolute degradation in side lobe suppression is derived in this paper.

Grating lobes suppression in stepped-frequency pulse train

Frequency stepping is one of the known techniques employed by modern radars to achieve high range resolution. The main advantage of this approach is that the actual instantaneous bandwidth of a radar is quite small compared with the total processing bandwidth. This allows the transmission of waveforms with extremely wide overall bandwidth (and, as a consequence, the attainment of high range resolution) without the usage of the expensive hardware needed to support wide instantaneous bandwidth. Unfortunately, the autocorrelation function of uniform frequency stepped pulse trains can have undesirable peaks, known as lobes. We address this issue, using an approach which allows us to suppress grating lobes below a desired threshold level in the case of appropriately chosen stepped frequency waveforms. We discuss in detail how to choose relevant parameters in order to produce such waveforms with small grating lobes, and give examples of waveforms with small overlap ratio. We also discuss the issue of high sidelobes in the vicinity of the mainlobe, which are inevitable in a stepped frequency train of linear frequency modulated (LFM) waveforms with small overlap ratio, and show that it is possible to suppress these, as well as the grating lobes, by means of nonlinear frequency modulation (NLFM).

Multilayer frequency selective surface with grating lobe suppression

AbstractConventional multilayer frequency selective surface combined with substrate‐integrated waveguide technique for grating lobe suppression is studied in this letter. Simulation and experiment results show that the grating lobe generated by middle dielectric layer can be greatly suppressed using this structure. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2501–2503, 2007; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.22778

Grating Lobes Suppression in Transverse Slot Linear Array with a Dual Parasitic Beam of Strip Dipoles

A new technique called the Dual Parasitic Beam (DPB) technique is proposed to suppress grating lobes in a rectangular waveguide broad wall transverse slot array. This technique involves an extra layer of parasitic strip dipoles that generate the DPB to suppress the grating lobes without opposing the main beam of the original slot linear array. A full wave EM analysis in Method of Moments (MoM) is conducted to compute the coupling excitation coefficients as well as the far field patterns of the slot and dipole currents. Analysis shows that a suitable dimension and arrangement of dipoles are needed to get a desired level of dipole excitations to meet the grating suppression condition. It is found that the grating lobes can be suppressed as much as 15 dB in the presence of the parasitic dipoles. Experiments are conducted to confirm the computed results.

Suppression method of grating lobe by pulse power transmission from an array antenna

AbstractA new method is proposed for suppressing the grating lobe (GL) by pulse power transmission from an array antenna. GL suppression relies on the fact that the maximum electric field value is not synthesized by the waves from the array antenna at the undesired points even if the maximum electric field is attained at the desired receiving point, because the pulses emerging from different antenna elements do not overlap. Two computer simulations are carried out to confirm this suppression effect. In the simulation using a two‐element array antenna with an element spacing exceeding one wavelength, the GL suppression effect is confirmed with a pulsed wave even though the GL is generated with a continuous wave. In pulsed power transmission simulation with many elements, the GL suppression effect is enhanced with an increasing number of elements. It is also found that the effect increases as the pulse width becomes smaller. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(2): 1–10, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20156

Grating lobe control in limited scan arrays

The use of multiple higher order modes for grating lobe control in arrays of large aperture elements scanned over restricted spatial sectors is described. Arrays of this type are useful in a number of applications including precision approach radar, weapons locators, and satellite communications systems. An extensive experimental and theoretical study that includes the design and use of dielectric lenses for control of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</tex> -plane null filling for an eight-element array, the investigation of null width effects on sidelobe levels, the experimental study of an element and control circuitry for two-dimensional scan, bandwidth effects, and the use of dielectric spatial filters and row displacement for residual grating lobe suppression is summarized.

Grating-lobe suppression in phased arrays by subarray rotation

A method of suppressing grating lobes in a uniform planar array is presented. In this method, the array is divided into equal sub-arrays which are physically rotated with respect to each other by specified angles. As a result, the grating lobes, which remain at the same angular distance from the main beam, are multiplied in number by the number of subarrays while their amplitude is divided by the same number. Spacing within each subarray still remains uniform. Only at the subarray boundaries do different spacings occur.

Broad-band impedance matching of rectangular waveguide phased arrays

A method for wide-band wide-angle impedance matching of rectangular waveguide phased arrays is presented. A maximum VSWR of 2.3:1 is achieved over a 50 percent bandwidth with a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60\deg</tex> half-angle conical coverage using an element spacing six percent less than the condition required for grating lobe suppression. A further reduction in element spacing, bandwidth, or scan volume results in an even better impedance match. Simplicity and high radiation efficiency are the unique features of this matching technique.

A design procedure for matching volumetrically scanned waveguide arrays

The impedance of a phased array of waveguides arranged in a triangular lattice and fitted with H-plane corrugated plates is analyzed using a scattering matrix method. The principal result is a virtually exact equivalent network consisting of three interconnected three-ports, each derived in terms of physical dimensions and scan angles for any volume or plane of scan limited only by grating lobes. A typical design procedure is illustrated by the case of scanning anywhere within an octant of a sphere. The cause of surface wave impedance mismatches, and the circumvention of the difficulty are described. Very fine sampling of the impedance versus angle would be required to ensure good performance were it not for certain matching criteria which are developed from the network. To avoid conditions of complete mismatch, the element area must be reduced by 2 percent less than that spacing required for grating lobe suppression. The maximum VSWR is less than 3.0:1 and the average is close to 2.0:1 in this case.