Sidelobe Characteristics Research Articles

A Novel Interpolated DFT Synchrophasor Estimation Algorithm With an Optimized Combined Cosine Self-Convolution Window

With the current power system being electronicized nowadays, synchrophasor estimation (SE) plays an increasingly critical role in the monitoring, analysis, and protection of the state of the power grid. One proposal has been brought to enhance the commonly used discrete Fourier transform (DFT) algorithm that has a large error due to the inherent spectral leakage and fence effect in asynchronous sampling by interpolations. This article proposes an SE algorithm based on an optimized combined cosine self-convolution (OCCSC) window. Using the sidelobe characteristics of the window functions as the evaluation index, an optimized combined cosine window is obtained by the accelerated particle swarm optimization (APSO) algorithm. The window function’s self-convolution is used to further expand its excellent characteristics. Based on these characteristics, combined with interpolated DFT, simulations and experimental verifications compared with other algorithms show the effectiveness of the proposed algorithm.

Laser Doppler signal processing based on trispectral interpolation of Nuttall window

Due to the asynchronous sampling in practical applications, spectrum leakage and fence effect significantly decrease the precision of fast Fourier transform (FFT)-the common signal processing method for laser Doppler velocimeter (LDV). In order to increase the precision of LDV signal processing, trispectral interpolation of Nuttall window is proposed. Based on the comparison and analysis of sidelobe characteristics, four-term first-order, four-term third-order, four-term minimum sidelobe, three-term minimum sidelobe Nuttall windows were adopted to reduce the spectrum leakage. Trispectral interpolation of these four kinds of window functions were carried out to alleviate the fence effect. Processing results of simulated and measured signals verify the viladity and accuracy of proposed method. For measured signals in laboratory, the minimum relative error of trispectral interpolation is 0.06% (four-term minimum sidelobe Nuttall window). Meanwhile, for simulated signals, the minimum relative error is only 0.0068% (four-term third-order Nuttall window in low frequency range). Overally speaking, four-term third-order and four-term minimum sidelobe Nuttall windows have better accuracy. Owing to its conciseness and efficience, trispectral interpolation of Nuttall window is a practical method for LDV signal processing.

A 60-GHz Four-Element Beam-Tapering Phased-Array Transmitter With a Phase-Compensated VGA in 65-nm CMOS

This paper reports a 60-GHz four-element beam-tapering phased-array transmitter with a lower sidelobe level (SLL). The array factor and the error vector magnitude (EVM) were calculated to explain the low sidelobe characteristic of a nonuniform amplitude array and to emphasize the importance of phase compensation, respectively. The phase-compensated radio frequency (RF) variable gain amplifiers (VGAs) were proposed to compensate the gain variance of phase shifters and, simultaneously, excite the nonuniform amplitude to each array element. The proposed VGA improves the relative phase error by 2° and the OP1dB by 2.4 dB within a gain control range of 5 dB, compared to the current steering without any compensation. Implemented in a commercial 65-nm CMOS process, the integrated array chip displays an root-mean-square (rms) gain error of <;0.53 dB and an rms phase error of <;8.8° in the frequency range of 57-66 GHz, while consuming a dc power of 403.2 mW and occupying a chip area of 2.88 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The fabricated array was integrated with a 1 × 4 Teflon array antenna to verify the beamforming and beam-tapering operations. With proper gain and phase control, the integrated array decreases the SLL by up to 5.2 dB, and the minimum SLL is -15.2 dB. To the best of the authors' knowledge, this is the first report on the implementation of CMOS beamtapering arrays in the 60-GHz band.

Multi-dimensional Ambiguity Function for Coherent Pulsed-LFM FDA Radar

Frequency diverse array (FDA) which employs a small frequency increment between adjacent elements can provide a range-angle-dependent beampattern with new application potentials. In this paper, the proposed coherent pulsed-LFM FDA scheme enables full spatial coverage with a single transmit waveform, wherein the transmit beamforming can be performed at the receiver with flexible signal processing means. In the coherent pulsed-LFM FDA radar configuration, the range sidelobe level (SLL) can be reduced significantly. Analyses of the multi-dimensional ambiguity function in terms of the low sidelobe characteristics, spatial coverage capability, and resolution properties in range, angle and Doppler domains are given by ambiguity function profiles. Comparisons with conventional phased array and MIMO (Multiple-Input Multiple-Output) radar are presented in the simulation. Results demonstrate the superiority of the proposed approach in angular coverage and sidelobe level with simplicity in engineering.

Range Coherence Factor for Down Range Sidelobes Suppression in Radar Imaging Through Multilayered Dielectric Media

In radar imaging applications through layered dielectric media, an antenna array with a limited operating frequency bandwidth at the low end of the microwave band is usually employed to probe the target space of interests. As a result, the focused radar imagery is characterized by severe sidelobes in the down-range direction, which leads to the degradation of the image quality. Several techniques, such as windowing and apodization filtering combined with phase coherence factor (PCF) filtering, have been reported to suppress the down-range sidelobes. However, these approaches either expand the main lobe width or are sensitive to parameter tuning. In this paper, by investigating the distribution characteristics of the down-range sidelobes among sub-frequency radar imageries, a robust and efficient range coherence factor (rCF) technique is proposed to suppress the down-range sidelobes in the focused radar imagery. The performance of the proposed approach is assessed by the finite-difference time-domain (FDTD)-based numerical simulations as well as onsite experiments to verify its sidelobes' reduction capabilities.

Radiation Pattern Performance of Unequally Linear Arrays with Parasitic Element

&lt;p&gt;For next generation of 5G mobile base station antennas, multibeam, multifrequency and low sidelobe characteristics requested. Simplify the feeding network will contribute a low feeder loss and frequency dependent. From the previous research by the author, low sidelobe level reported by density tapered array configuration from -13 dB to -16 dB and the result maintained for wideband operation frequency at 28 GHz, 42 GHz, and 56 GHz. However, the grating lobe has occurred due to element spacing larger than a wavelength of higher frequency (56 GHz). In this paper, an investigation was made of the performance of radiation pattern for unequally microstrip linear array antenna in frequency 42 GHz and 56 GHz by loading parasitic elements. The effect of parasitic element to the impedance, gain, and sidelobe level of unequally microstrip linear spaced tapered array also examined. The design has been simulated using Ansoft High Frequency Structural Simulator (HFSS) ver 16.0.&lt;/p&gt;

LOW SIDELOBE AND WIDEBAND CHARACTERISTICS OF DENSITY TAPERED ARRAYS FOR 5G MOBILE SYSTEMS

Conventional mobile base station antennas are composed of equally spaced linear array antennas. In order to achieve low side lobe characteristics, excitation coefficients for array elements are determined by a feeding network. Because of complexity of the feeding network, applicable frequency range is limited. In 5G mobile system, multi frequency band operation is requested. For achieving low sidelobe and wide frequency characteristics, a density tapered array configuration is promising. Because of uniform excitation coefficients, feed network has no frequency dependence and wide frequency range application is expected. In this paper, abilities and design method of low sidelobe characteristics are investigated. By density tapering, sidelobe levels are reduced from -13dB to -16dB. As for wide band characteristics, low sidelobe characteristics are maintained during 28GHz to 56GHz operations. Usefulness of a density tapered array is numerically clarified.

High-Gain SIW Cavity-Backed Array Antenna With Wideband and Low Sidelobe Characteristics

A 16 ×16 gain-high substrate integrated waveguide (SIW) cavity-backed slot array antenna with wideband and low sidelobe level (SLL) characteristics is proposed in this letter. The array is fed by an 8 ×8 SIW corporate-feed network in the bottom layer. A series of 2 ×2 compact SIW sub-arrays are employed as radiating elements in the top layer. The 45 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> linearly polarized technique is used in the design of radiating slots, which can substantially suppress the SLL of the array. Meanwhile, benefiting by the broadband merit of the sub-array and the corporate-feed structure, the proposed array has a broad bandwidth. A prototype is fabricated to verify the array properties. The measured bandwidth is 12% from 19 GHz to 21.5 GHz and the maximal gain can reach up to 29 dBi. Besides, the low sidelobe characteristic is achieved and the measured first SLLs are below -24 dB across the entire work band.

A 45$^{\circ}$ Linearly Polarized Hollow-Waveguide 16$\,\times$16-Slot Array Antenna Covering 71–86 GHz Band

A 45° linearly polarized hollow-waveguide 16 × 16- slot array antenna is proposed for point-to-point wireless communication in the 71-76 GHz and 81-86 GHz bands. The antenna is composed of an equally-split corporate-feed circuit and 2 × 2-element sub-arrays which radiate the 45 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> linear polarization. Low sidelobe characteristics are obtained in the E-plane by diagonal placement of the square antenna rotating by 45 degrees. To suppress cross polarization, a radiating narrow-slot pair is adopted. The sub-array is designed by a genetic algorithm and 25.7% reflection bandwidth for is obtained by decreasing the Q of two eigenmodes of the radiating element. A 16 × 16-element array is fabricated by diffusion bonding of thin copper plates. The total thickness is 3.2 mm which is less than 1 free space wavelength. A high gain of 32.9 dBi, high antenna efficiency of 86.6% and low sidelobe characteristics of -27.1-dB first sidelobe levels are measured at the center frequency of 78.5 GHz. Further, the broadband characteristics of reflection , show a gain of more than 31.4 dBi, and low cross polarization of less than -30 dB are achieved over the 71-86 GHz band.

Fault Location Scheme for Transmission Lines Using Kaiser Self-Convolution Windowed FFT Phase Comparison

In order to improve the fault location accuracy, and eliminate the influence of spectral leakage in power transmission line fault location, we proposed a novel fault location scheme for transmission lines based on multi-measurements and phase comparison with Kaiser self-convolution windows FFT, which can locate the fault between two adjacent towers in the fault-prone segment. It is based Kaiser self-convolution window's excellent performance of leakage suppression, which can effectively solve the phase current fault component is relatively large errors due to spectral leakage problem. Firstly, this paper analyzes the causes of the phase spectrum leakage, then elaborates the sidelobe characteristics of Kaiser self-convolution window, and lists phase comparative fault location using steps, finally, verifies the correctness of the proposed method by simulation. The results show that the proposed method can effectively suppress spectral leakage, has a high location accuracy, a wide applicability and its solving of phase difference is precise.

콤팩트 안테나 테스트 레인지용 경면수정 오프셋 복반사경 시스템의 설계

경면수정 오프셋 그레고리안 반사경 안테나는 고이득, 저 사이드로브 특성 때문에 위성 통신 시스템에 널리 사용되고 있다. 그러나 본 논문에서는 CATR(Compact Antenna Test Region)을 위한 반사경 시스템으로 설계하고 그 근접 전계 특성을 조사하였다. CATR은 시험 영역에 진폭과 위상 리플이 작고 교차 편파가 낮은 균일 평면파를 제공하여야 한다. 따라서 근접 전계를 개구면의 전력 분포, 급전 혼의 복사 패턴, 개구면과 시험 영역까지의 거리 변화에 따라 계산하여 나타냈다. 또한, 30 GHz에서 동작하는 경면수정 오프셋 복반사경을 제작하고 근접전계를 측정하였다. 그 결과, 측정치와 계산치가 비슷하게 나타났다. 이로서 본 논문에서 설계된 경면수정 오프셋 복반사경은 콤팩트 안테나 테스트 레인지로 사용될 수 있을 것으로 생각된다. Gregorian offset dual-shaped reflector antennas have been widely used in the satellite communication systems for their high gain and low sidelobe characteristics. However, in this paper, it is designed as the CATR(Compact Antenna Test Range) reflector system, and its near-field characteristics are investigated. The CATR facility needs to provide an uniform plane wave with the minimum amplitude and phase ripple and the low cross polarization to the test region. Therefore, the reflector near-field patterns are calculated and presented with the variations of the aperture power distribution, the feed horn pattern, and the distance from the aperture to the test zone. Also, the offset dual-shaped reflector is fabricated at 30 GHz, and its near-field patterns are measured. The measured results are in good agreement with the calculated results. From theses results, we confirm that the designed offset dual-shaped reflector can be used as the reflector system for the compact antenna test range.

DESIGN AND ANALYSIS OF PHASED ANTENNA ARRAY WITH LOW SIDELOBE BY FAST ALGORITHM

In this paper,a high performance phased antenna array is designed. Compared with the traditional ones,this antenna array has a lower sidelobe characteristic of down to −16 dB. At different scanning angles,the comparison between calculated and measured results of S-parameters and E- and H-plane antenna patterns is made and a very good agreement is found. Moreover,the precorrected fast Fourier transform method is employed to accelerate the entire computational process to reduce significantly both the memory requirement and computational time,but to increase the design accuracy and optimization efficiency.

Better narrowband spectral measurements

Spectrum analysis based on traditional FFT techniques is a widely available, commonly understood and general purpose tool for use with mechanical systems. In applications such as system identification, modal analysis and rotating machinery signature analysis, relevant information content in signals is greatest near narrowband phenomena in the frequency domain. Effort should be focused on reducing bias error in these regions in preference to reducing variance error. Time aliasing methods of spectrum analysis can result in superior bias error reduction, producing an accurately sampled spectral estimate and permitting window function characteristics to be decoupled from the DFT resolution, or frequency line spacing. Windows created with time aliasing can be optimized by adjusting the amount of time or frequency localization, according to the type of spectrum being measured. Assuming conventional criteria, time aliased windows can achieve better mainlobe and sidelobe characteristics than other windows. An innovative approach, appropriate with continuous spectra, is to use the window as a discrete sampling function in frequency to eliminate bias error inherent in the effective convolution between window and signal transform. Both approaches have been successfully implemented and results are presented using time aliased spectral estimates showing more accurate measurements of narrowband phenomena when used in applications of rotating machinery vibration and system identification.

A NRD Guide Fed Dielectric Lens Antenna with High Gain and Low Sidelobe Characteristics

A NRD guide fed dielectric lens antenna with high gain and low sidelobe characteristics is proposed for millimeter wave applications. The measured results showed very good performance at 60 GHz. It exhibited a gain of 24.9 dBi, 27 dB sidelobe level suppression.

Development of modified polyphase P codes with optimum sidelobe characteristics

The unique range sidelobe properties of P codes are reviewed and a detailed description of the sidelobe reduction technique is given. Based on this analysis, a novel waveform and corresponding pulse compression filter concept are developed. This new approach achieves a highly improved range-sidelobe reduction effect without increasing the system complexity. It is shown how the peak of the range sidelobe can be kept minimised to the Barker code level on this particular waveform. Simulation results are provided to demonstrate the superior performance of this pulse compression scheme and verify its robustness to various noise sources existing in real environments.

A method for generating complex finite sequences with a small peak sidelobe, using one period of a complex binary orthogonal sequence

AbstractFinite sequences with a small sidelobe level of an autocorrelation function are used for the pulse compression of radar signals and the synchronization of pulse communication circuits. This paper demonstrates that a finite sequence with a small peak sidelobe level can be generated through an algebraic approach from a period of a complex binary orthogonal sequence that is obtained by mapping M sequences on GF(2) to complex periodic sequences. The generated sequence is a complex finite sequence comprised of two complex numbers as its components, for which the code length can be given as 2k − 1, where k is a positive integer. By comparing the sidelobe characteristics of the resulting sequence with those of conventional real binary finite sequences for which the components are given as 1 and −1, this paper shows that the peak sidelobe level can be suppressed compared with conventional cases by rendering the finite sequence into a complex binary sequence. In the case of a code length of 7, for example, complex binary finite sequences with a peak sidelobe level lower than the real binary finite sequence shown by Barker by approximately 3.0 dB can be generated. In addition, radio frequency (RF) signals that are code‐modulated with the complex binary finite sequence are produced and their sidelobe characteristics are evaluated from signal waves that are obtained by correlating the signals, with the paper showing a high degree of agreement between experimental and calculated values. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 86(3): 67–76, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.1141

Spatial-spectral holographic correlator at 1536 nm using 30-symbol quadriphase- and binary-phase-shift keyed codes

Optical 30-symbol quadriphase-shift keyed (QPSK) and binary-phase-shift keyed (BPSK) codes were processed in a spatial-spectral holographic correlator with the Er(3+): Y(2)SiO(5) spectral hole-burning material operating at 1536 nm in the important 1550-nm communications band. The results demonstrate the ability of spatial-spectral holographic correlators to process QPSK codes and BPSK codes with the same apparatus. The high-fidelity correlations produced by this optical coherent transient device exhibit the low sidelobe characteristics expected for the codes used.

Wideband beamspace adaptive array utilizing FIR fan filters for multibeam forming

We propose a a wideband beamspace adaptive array that uses FIR fan filters to construct a multibeam forming network. We also describe a method for designing such FIR fan filters. Approximation is achieved by combining spectral transformation and the window method such that the beam patterns including the sidelobe characteristics of the resulting fan filters are virtually frequency independent. This is a requirement of beamforming networks used in multibeam forming. Fan filters designed with the proposed method are used to demonstrate that the beam-space adaptive array can suppress interference signals having a wide fractional bandwidth and that the array has fast convergence.

Improvement of sidelobe characteristics of an offset dual reflector antenna with an elliptical beam

After we manufactured an offset dual-shaped reflector antenna with an elliptical beam designed by the geometrical optics approach, we found that the antenna could not provide the desired low sidelobe characteristics. In general, we often encounter the case in which the desired sidelobe characteristics are not attained because of design inaccuracy, reflector surface error, and reflector alignment error after antenna manufacturing. We here propose a newly developed method, called aperture phase distribution control by adjustment of reflector segments (APCAR). This method has been verified through improvement of sidelobe characteristics of the offset dual-shaped reflector antenna with an elliptical beam, whose aperture diameter is 1.3 m × 2.8 m. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(12): 10–19, 1999

Improvement of sidelobe characteristics of an offset dual reflector antenna with an elliptical beam

After we manufactured an offset dual-shaped reflector antenna with an elliptical beam designed by the geometrical optics approach, we found that the antenna could not provide the desired low sidelobe characteristics. In general, we often encounter the case in which the desired sidelobe characteristics are not attained because of design inaccuracy, reflector surface error, and reflector alignment error after antenna manufacturing. We here propose a newly developed method, called aperture phase distribution control by adjustment of reflector segments (APCAR). This method has been verified through improvement of sidelobe characteristics of the offset dual-shaped reflector antenna with an elliptical beam, whose aperture diameter is 1.3 m × 2.8 m. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(12): 10–19, 1999