Side Lobes

A pair of ultrahigh-frequency (UHF) radars system for measuring the two-dimensional river flow patterns is presented. The system consists of two all-digital UHF radars with exactly the same hardware structure, operating separately at 329-339 MHz and 341-351 MHz. The adoption of direct radio frequency (RF) sampling technique and digital pulse compression simplifies the structure of radar system and eliminates the distortion introduced by the analog mixer, which improves the SNR and dynamic range of the radar. The field experiment was conducted at Hanjiang River, Hubei province, China. Over a period of several weeks, the radar-derived surface velocity has been very highly correlated with the measurements of EKZ-I, with a correlation coefficient of 0.958 and a mean square error of 0.084 m/s.

A pair of ultrahigh-frequency (UHF) radars system for measuring the two-dimensional river flow patterns is presented. The system consists of two all-digital UHF radars with exactly the same hardware structure, operating separately at 329–339 MHz and 341–351 MHz. The adoption of direct radio frequency (RF) sampling technique and digital pulse compression simplifies the structure of radar system and eliminates the distortion introduced by the analog mixer, which improves the SNR and dynamic range of the radar. The field experiment was conducted at Hanjiang River, Hubei province, China. Over a period of several weeks, the radar-derived surface velocity has been very highly correlated with the measurements of EKZ-I, with a correlation coefficient of 0.958 and a mean square error of 0.084 m/s.

Using a low coherence interferometry (LCI) model, a comparison of broadband single-Gaussian and multi-Gaussian light sources has been undertaken. For single-Gaussian sources, the axial resolution improves with the source bandwidth, confirming the coherence length relation that the resolution for single Gaussian sources improves with increasing spectral bandwidth. However, narrow bandwidth light sources result in interferograms with overlapping strata peaks and the loss of individual strata information. For multiple-Gaussian sources with the same bandwidth, spectral side lobes increase, reducing A-scan reliability to show accurate layer information without eliminating the side lobes. The simulations show the conditions needed for the resolution of strata information for broadband light sources using both single and multiple Gaussian models. The potential to use the model to study optical coherence tomography (OCT) light sources including super luminescent diodes (SLDs), as reviewed in this paper, as well as optical delay lines and sample structures could better characterize these LCI and OCT elements. Forecasting misinformation in the interferogram may allow preliminary corrections. With improvement to the LCI-OCT model, more applications are envisaged.

A random Phase Center Motion (PCM) technique is presented in this paper, based on Frequency Modulated Continuous Wave (FMCW) radar, in order to suppress the angle-Doppler coupling in Time Division Multiplex (TDM) Multiple-Input-Multiple-Output (MIMO) radar when employing sparse array structures. The presented approach exploits an apparently moving transmit platform or PCM due to spatio-temporal transmit array modulation. In particular, the work considers a framework utilizing a random PCM trajectory. The statistical characterization of the random PCM trajectory is devised, such that the PCM and the target motion coupling is minimal, while the angular resolution is increased by enabling the virtual MIMO concept. In more details, this paper discusses sidelobe suppression approaches within the angle-Doppler Ambiguity Function (AF) by introducing a phase center probability density function within the array. This allows for enhanced discrimination of multiple targets. Simulation results demonstrate the suppression angle-Doppler coupling by more than 30 dB, even though spatiotemporal transmit array modulation is done across chirps which leads usually to strong angle-Doppler coupling.

The most recent generation of Global Navigation Satellite Systems (GNSS) are implementing Binary Offset Carrier (BOC) modulation. These signals are expected to provide not only better precision in the estimation of the signal's delay and phase but also more robustness to multipath effects. The advantage of BOC signals is that the main lobe of the correlation is very narrow, but on the other hand they present side lobes. For high-order signals, the amplitude of the side lobes can be similar to the amplitude of the main one or even exceed it under specific scenarios. Some techniques to mitigate the code ambiguity exploit the fact that BOC signals can be understood as the sum of two BPSK signals. Even though these techniques achieve their objective, they lose the robustness against multipath and increase the tracking noise. This paper presents a new combination between the time delay estimated by these kind of techniques and the time delay estimated using the full BOC. The idea of the combination is the same as the carrier smoothing but instead of using the carrier measurement, two code measurements are combined. Since the delay introduced by the ionosphere is the same, or very close, using the Full-BOC and the two-BPSK techniques, as it will be shown in this paper, the smoothing time can be large values, compared with the common carrier smoothing time. Several simulations of the new code smoothing strategy for different scenarios are presented in this paper.

This paper introduces a new geometry of a rectangular microstrip patch antenna that improves the performance of a conventional microstrip patch antenna .This antenna is designed to operate at 5.38 GHz with enhanced bandwidth of 11.15%. For the desired result, a triangular notch is inserted into the patch antenna. The proposed geometry provides improvement in other radiation parameters like gain, efficiency and impedance behavior, when it is compared with conventional antenna. Keywords— Rectangular Microstrip Patch Antenna, Antenna Feed, Antenna Radiation Pattern.

A novel electromagnetic band gap (EBG) design has been introduced as a replacement for the conventional mushroom-like EBG that surrounds the array patch antenna. This innovative design, known as the Triple Side Slotted EBG (TSSEBG), aims to enhance the antenna's radiation performance by mitigating surface wave effects. The TSSEBG demonstrates significant improvements in antenna efficiency, directivity, and gain when compared to the reference antenna, which lacks an EBG. These enhancements are primarily attributed to the reduction of side lobes resulting from the diminished surface wave effects. The TSSEBG is achieved through specific modifications to the conventional mushroom-like EBG structure, simplifying its complexity by reducing the number of unit cells and vias. Furthermore, the TSSEBG introduces the advantage of providing three distinct band gaps, in contrast to the single band gap frequency of 6 GHz offered by the mushroom-like EBG structure. The flexibility of TSSEBG's placement makes it a versatile choice for various antenna applications. Simulation results for the array patch antenna, both with and without the mushroom-like EBG and TSSEBG, are presented in Table 1. This structure holds significant potential for a wide range of applications in satellite communications.

This paper describes the comparative analysis of different types of microstrip transmission sensor for rice quality detection. Basically the cylindrical slot antenna and microstrip line based structure have been discussed. This paper shows focus on the advantage and tremendous characteristics of microstrip couple line sensor over the other microwave sensors and the substantial amount of efficiency has been achieved by the use of Coupled line filter approach. The analysis on the basis of various parameters like, characteristics impedance, microstrip width and dielectric constant of the substrate, modes of reflection coefficient, insertion loss, radiation, moisture content in rice grain, and the frequency applied. By applying the different principles and methods and finally with Vector Network Analyzer the reflection coefficient measurement reading give us the measurement of broken rice. Keywords-Coupled Line Filter, Microstrip, Moisture Content (m.c), Slot Antenna, Vector Network Ana...