Amplitude Statistics of Sea-Ice Clutter Using a Millimeter Wave Radar

Sea-ice clutter was measured using a millimeter wave radar with frequency of 34.86GHz and pulse length of 30ns. To determine the sea-ice clutter amplitude statistics, we investigated the log-normal, Weibull, log-Weibull and K-distributions using the Akaike Information Criterion (AIC), which is more rigorous fit of the distribution to the data than the least-squares method. It is shown that the amplitude of sea-ice clutter obeys almost a log-Weibull distribution.     

Suppression of Sea-ice Clutter Observed by a Millimeter Wave Radar

Sea-ice clutter was measured using a millimeter wave radar (MWR) with a frequency of 34.86 GHz, the beamwidth of 0.25° and pulsewidth of 30 ns which is located at Mombetsu in Hokkaido, Japan. In this paper, targets are an iron tower and a breakwater which are embedded in sea-ice clutter. We have found that the sea-ice clutter amplitude obeys the Weibull distribution. As a result of this, we obtained target to clutter ratio improvement of 22.6, 17.2 dB for an iron tower and a breakwater, respectively, by considering the modified LOG/CFAR system which is the transformation from Weibull to Rayleigh distribution.     

Detection of Target Embedded in Sea Clutter by Means of Millimeter Wave Radar

Sea clutter was measured using a millimeter wave radar with a frequency of 34.86GHz and pulse length of 30ns. A car carrier ship target was embedded in sea clutter. It has been discovered that target pulse-to-pulse fluctuations obey a Weibull distribution and sea clutter obey a Rayleigh distribution. We obtained target to clutter ratio improvement of 23.8dB by applying the cell average LOG/CFAR techniques. The computer simulation has been made to evaluate the detection probability and the false alarm probability. The simulation result was in good agreement with the observed data.     

Analysis of Millimeter Wave Scattering by an Electrically Large Metallic Grating Using Wavelet-Based Algebraic Multigrid Preconditioned CG Method

An effective wavelet based multigrid preconditioned conjugate gradient method is developed to solve electromagnetic large matrix problem for millimeter wave scattering application. By using wavelet transformation we restrict the large matrix equation to a relative smaller matrix and which can be solved rapidly. The solution is prolonged as the new improvement for the conjugate gradient (CG) method. Numerical results show that our developed wavelet based multigrid preconditioned CG method can reach large improvement of computational complexity. Due to the automaticity of wavelet transformation, this method is potential to be a block box solver without physical background.     

Investigation of the Dielectric-Loaded, Ridged Helical Groove Slow-Wave System for the Millimeter Wave TWT

A dielectric-loaded, ridged helical groove slow-wave structure for the millimeter wave traveling wave tube is presented in this paper. The effects of the groove depth, ridge dimensions and the dielectric permitivety on the wave propagating properties and the interaction impedance are investigated in detail. From the analysis, it is indicated that for broader band amplification in a helical groove travelling wave tube, a ridged helical structure with shallow groove and loaded by dielectric with proper relative permitivety may be applied.     

A Novel Parallel-Series Feeding Network of Microstrip Patch Arrays with Composite Right/Left-Handed Transmission Line for Millimeter Wave Applications*

A novel parallel-series feeding network of microstrip patch arrays with composite right/left-handed transmission line (CRLH-TL) for millimeter wave applications is proposed. Since there is no inserting phase shift in the patch elements with CRLH-TL feeding structure, the inherent pattern shift resulting from the traditional parallel-series feeding network is removed. Besides, because of the simpler structure and the shorter length of the CRLH-TL feeding network, the antenna array is of higher gain than that with the conventional parallel feeding network.* Supported by the National Natural Science Foundation of China (No. 60371010) and (No. 60471037)     

Effect of Attenuator on BWO Start Oscillation Condition in a Helix Millimeter Wave TWT Under Magnetic Focusing

In a practical helix millimeter wave traveling-wave tube (TWT), there are always magnetic focusing system for constraining the electron beam as it passes through the interaction region and attenuator for suppressing the oscillations, including backward-wave oscillation (BWO) and improving the output power. In view of the attenuator and magnetic focusing system, a 2D linear theory is employed to analyze BWO start oscillation condition. Numerical results show that the start oscillation length of the millimeter wave TWT decreases when the start position of the attenuator is close to the input section of the slow wave structure (SWS), and that it increases with the decrease of the attenuation length or the increase of the attenuation quantity. Therefore, in order to predict the BWO accurately, we should take into the attenuator and magnetic focusing system account.     

Chaotic Motion of the cc System and a New Mechanism of J/Ø Suppression

Based on random matrix theory and reduced BS equation, it is found that the regular motion of cc system can be expected at a small value of color screening mass but the chaotic motion at a large one. It is shown that the level mixing due to color screening serves as a new mechanism resulting in J/Ø suppression. Moreover, this kind of suppression can occur before the color screening mass reaches its critical value for J/Ø dissociation. In addition, it is. implied that a strong J/Ø suppression is possible in the absence of dissociation of J/Ø.