High performance millimeter-wave microstrip circulators and isolators

Millimeter wave systems, phased array antennas, and high performance components all require wideband circulators (and isolators) to perform diplexing and switching, to improve isolation and Voltage Standing Wave Ratio (VSWR), and to construct IMPATT diode reflection amplifiers. Presently, most of the millimeter-wave circulators and isolators are available in the configurations of waveguide or stripline, both of which suffer from the shortcomings of bulky size/weight, narrow bandwidth, and poor compatibility with monolithic millimeter-wave integrated circuits (MMIC). MMW microstrip circulators/isolators can eliminate or improve these shortcomings. Stub-tuned microstrip circulator configuration were developed utilizing the electromagnetic fields perturbation technique, the adhesion problems of microstrip metallization on new ferrite substrate were overcome, the fabrication, assembly, packaging techniques were improved, and then successfully designed, fabricated a Ka band circulator which has isolation and return loss of greater than 16dB, insertion loss less than 0.7dB. To assess the steady and reliable performance of the circulator, a temperature cycling test was done over the range of -20 to +50 C for 3 continuous cycles and found no significant impact or variation of circulator performance

Development and application of a prognostic cumulus parameterization

June 1995.Also issued as author's dissertation (Ph.D.) -- Colorado State University, 1995.Includes bibliographical references.The Arakawa-Schubert cumulus parameterization assumes a quasi-equilibrium between the cumulus convection and the "large-scale forcing." It is, however, not very clear that it is always possible to distinctly separate the "non-convective processes" from the convective processes. We therefore propose a prognostic approach for implementing the Arakawa-Schubert parameterization. We relax the assumption of cloud work function quasi-equilibrium by explicitly using a cumulus kinetic energy (CKE) equation. This approach bypasses the ambiguity in separating the large-scale forcing from the cumulus convection, and may be the first step toward improving the interactions between parameterized physics in large-scale numerical models. The CKE approach also simplifies the calculation and hence allows more sophisticated physics of convection, such as downdrafts, to be taken into account. Simple experiments with constant radiative cooling in a one dimensional (1-D) model showed that the steady-state solution depends on the value of a., a parameter that relates CKE to cloud base mass flux. Experiments also showed that LSP (large-scale precipitation) is a part of the "forcing" for the cumulus convection, and that how we parameterize the LSP has direct effects on the results. In the meantime, the LSP is also a response to convective detrainment. Therefore, we cannot really clearly separate forcing and response, as Arakawa and Schubert (1974) did. The prognostic CKE approach was tested in the 1-D model to simulate observations from the GARP (Global Atmospheric Research Program) Atlantic Tropical Experiment. We can successfully simulate the time evolution of the precipitation rate and the vertical distribution of the apparent heat source and moisture sink. The atmosphere is saturated too often in the simulation, however. This can be attributed to the over-simplified largescale saturation parameterization (LSP) which re-evaporates the precipitation falling from upper levels. LSP does not become active until the whole grid box is saturated. Two different values of ex were tested in the GATE simulation. Results indicate that one value of ex produces a better time evolution, while the other generates a more realistic vertical structure of the heating rate. This may be due to the fact that we have used only one ex for all cloud types. According to the relation derived from the definitions of CKE and cloud-base mass flux, ex should be a function of cloud depth. We tested the prognostic CKE approach against the cloud work function quasi-equilibrium with the Colorado State University general circulation model. It was found that the model produces much higher anvil incidence which dramatically reduces the absorbed solar radiation in the tropics. A "fractional coverage" has been introduced in the simple anvil parameterization. Using the fractional anvils with the CKE approach, we found improvements in the January global precipitation distribution, especially over land. Cumulus convection also occurs much more often. As a part of the development of the prognostic CKE cumulus parameterization, the fractional entrainment rate, A, is used as the cloud spectral parameter, replacing the detrainment- level height as chosen by Lord (1978). Lord (1978)'s approach had been questioned by other authors (e.g. Kao and Ogura, 1987) and was proven incompatible with the CKE approach. With this approach, A is an independent variable and the value of ex should depend on llA and the vertical resolution of the model. The independent variable A appears to be a physically more reasonable identifier for cloud types.Sponsored by the National Science Foundation ATM-9121629 and ATM-9214981; and the U.S. Department of Energy DE-FG03-94ER91629

The Harbin Jewish Community and the Regional Conflicts of Northeast China, 1903-1963

This study examines the historical development of the Harbin Jewish community in Northeast China from its beginning in the early 1900s to its end in the 1960s. Scholars seldom pay enough attention to the Harbin Jewish community, the largest and most influential Jewish community in Asia. This study aims to fill this significant geopolitical gap of the history of Jews in the East. I develop two major narrative strategies in locating the Harbin Jewish Community in its historical map: (1) chronologically intertwining the development of the Harbin Jewish community within the local history of Harbin, by examining the relations between the Harbin Jewish community and its changing governors, namely, the Russian, Chinese, and Japanese policies towards the Jews; (2) investigating in parallel the contacts between the Harbin Jewish community with its contemporary Jewish communities in Shanghai, Europe and the United States, especially during the globally influential World War I and World War II period. This study challenges the argument that the Chinese and the Jews did not cross paths in these important historical events mentioned above. By tracing the history of the Harbin Jewish community, this study demonstrates that Jewish experience in China must be perceived as a whole and the survival of the Jewish refugees in Shanghai during the Holocaust in WWII should be put into its historical context rather than a single historical accident. The Harbin Jewish community thereby has an enduring legacy in the reconstruction of postmodern historiography and international relationships

Demailly-Lelong numbers on complex spaces

We establish a pointwise comparison of two notions of Lelong numbers of plurisubharmonic functions defined on singular complex spaces. This shows a conjecture proposed by Berman-Boucksom-Eyssidieux-Guedj-Zeriahi, affirming that the Demailly-Lelong number can be determined through a combination of intersection numbers given by the divisorial part of the potential and the SNC divisors over a log resolution of the maximal ideal of a given point. We also provide an estimate for quotient singularities and sharp estimates for two-dimensional ADE singularities.Comment: 15 page

Asymptotic distributions of the signal-to-interference ratios of LMMSE detection in multiuser communications

Let ${\mathbf{s}}_k=\frac{1}{\sqrt{N}}(v_{1k},...,v_{Nk})^T,$ $k=1,...,K$, where $\{v_{ik},i,k$ $=1,...\}$ are independent and identically distributed random variables with $Ev_{11}=0$ and $Ev_{11}^2=1$. Let ${\mathbf{S}}_k=({\mathbf{s}}_1,...,{\mathbf{s}}_{k-1},$ ${\mathbf{s}}_{k+1},...,{\mathbf{s}}_K)$, ${\mathbf{P}}_k=\operatorname {diag}(p_1,...,$ $p_{k-1},p_{k+1},...,p_K)$ and \beta_k=p_k{\mathbf{s}}_k^T({\mathb f{S}}_k{\mathbf{P}}_k{\mathbf{S}}_k^T+\sigma^2{\mathbf{I}})^{-1}{\math bf{s}}_k, where $p_k\geq 0$ and the $\beta_k$ is referred to as the signal-to-interference ratio (SIR) of user $k$ with linear minimum mean-square error (LMMSE) detection in wireless communications. The joint distribution of the SIRs for a finite number of users and the empirical distribution of all users' SIRs are both investigated in this paper when $K$ and $N$ tend to infinity with the limit of their ratio being positive constant. Moreover, the sum of the SIRs of all users, after subtracting a proper value, is shown to have a Gaussian limit.Comment: Published at http://dx.doi.org/10.1214/105051606000000718 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org