Steady-State Responses of NRD-Guide LSE/LSM Mode Oscillators in MM-Wave Bands

The analysis methods for the steady-state responses of the mm-wave band NRD-guide negative impedance oscillators based on nonlinear microwave autonomous circuits harmonic balanced method are presented in the paper in details. Firstly, the large-signal nonlinear lumped equivalent circuits of the Gunn diode are studied in mm-wave bands. Then, the performances of two kinds of NRD-guide autonomous circuits, the probe-exciting LSM ₁₁ ^o-mode oscillator and the LSE ₁₁ ^o-mode oscillator, are analyzed by the way of extracting the large-signal dynamic harmonic admittance (conductance) of the Gunn diode or directly configuring the harmonic balance equations for the oscillator. The input impedance of the exciting probe in the oscillator and the performances of the load-pulling and the local stability of the NRD-guide oscillator are also involved.     

Discontinuity of NRD-Guide and Its Application in Millimeter Wave Circuits

In this paper, the performances of two typical discontinuous structures of the NRD-guide, the traverse metallic rod to disturb an incident wave and the traverse probe to excite required modes, are analyzed and computed by utilizing the theory of modes orthogonality of the NRD-guide. The moment method is used to evaluate the current distribution on the rod and probe and the affection of some higher-order modes is taken into account simultaneously. On these bases, the multitone exciting steady states of two kinds of important circuits that employ the above discontinuous structures, the NRD-guide crossbar balanced mixer and the LSM ₁₁ ⁰ -mode oscillator, are simulated by the harmonic balance technique based on the multi-dimensional discrete Fourier transformation (MDFT-HB method).     

Steady State Responses of NRD-Guide Crossbar Balanced Mixer in MM-Wave Band

The periodic and quasi-periodic steady states of the nonradiative dielectric waveguide (NRD-guide) crossbar single-balanced mixer excited by single tone or dual tones in mm-wave band are deeply researched in the paper. Based on the wideband dispersion characteristics, the mode self-contained property and the modes orthogonality and a series of modes excitation criterions of the NRD-guide, a novel mixer is designed and analyzed. Two important parameters, the local oscillator and incident wave inductive electromotive forces corresponding to the LSE/LSM mode-converter and LSM-mode probe respectively, are calculated firstly by using the wire-antenna theory and the moment method. According to the theorem of band-pass signal sampling, a kind of integrated and general quasi-periodical steady-state responses algorithm for the nonlinear microwave/mm-wave circuits excited by multiple tones, the inter-modulation balance method based on the multi-dimension discrete Fourier transformation (MDFT-IMB), is designed and then successfully applied to calculate the performances of the above NRD-guide mixer.     

A new type NRD-guide receiving front-end in Ka-band

A new type millimeter-wave receiving frond-end using NRD-guide as internal transmission line is presented in this paper. The receiving frond-end consists of a NRD-guide crossbar balanced mixer, a NRD-guide LSE mode local oscillator and two impedance-converters at two input ports of the mixer circuit. Firstly, the propagation characteristics of some transmission modes often used in NRD-guide are given, and the conditions which these modes are applied as the operating modes are discussed. Secondly, the principle of the balanced mixed which is regarded as the key circuit unit in the receiving frond-end is analysed by using vector Green's function, and the conversion loss of the mixer is computed with an equivalent circuit in Ka-band. And then, from the view of obtaining the optimum performances of the whole receiving frond-end, some methods of designing local oscillator are expound. Some experimental results of the receiving frond-end at Kaband are given in the paper lastly. Because the frond-end have the impedance matching and converting circuits, it possesses better electrical performance. The integrated frond-end which have compact size and excellent shock strength is suitable for varied millimeter-wave system.     

Oscillator strength measurements of the 4s5s 3S1 → 4snp 3Po2 Rydberg transitions of zinc

In the present experimental work, oscillator strengths of the 4s5s ³S₁ → 4snp ³P^o₂ (18?≤?n?≤?53) Rydberg transitions of zinc are reported. The stepwise laser excitation from the ground state 4s^{2 1}S₀ was achieved using three dye laser beams simultaneously pumped by the second (532?nm) and third (355?nm) harmonics of a Q-switched Nd: YAG (Neodymium-doped yttrium aluminum garnet) laser. The vapor containment and detection system was a single wire thermionic diode ion detector operating in space charge limited mode. A trend of the above-mentioned f-values from n?=?18 to 53 versus the principle quantum number n has been presented. Furthermore, continuity has been verified between the discrete f-values and the oscillator strength density at the threshold.     

Nonlinear Frequency-Modulation Distortion Analysis for VCO Based on Harmonic Balance Method

The analysis methods for the steady-state responses of the voltage tuning negative resistance oscillator (voltage-controlling oscillator, VCO) by the microwave nonlinear autonomous circuit harmonic balance method in millimeter-wave bands are studied in the paper. Firstly, the quasi-periodic characteristic of the steady-state response of the VCO modulated by a periodic signal is proved. Then, on the bases of the harmonic balance analysis and the inter-modulation balance analysis, a novel method for obtaining the steady-state tuning performance and the nonlinear frequency-modulation distortion characteristic of the VCO is presented. The total analysis process is aimed to a kind of NRD-guide Gunn diode VCO. The large-signal lumped equivalent circuit model of the millimeter-wave P⁺N-junction varactor is also given for explaining the algorithm and the principle of the NRD-guide VCO.     

Temperature study of the polariton associated with the 248 cm soft mode in LiNbO3

The temperature dependence of the dispersion curve of the polariton associated with the 248 cm^-1 mode in LiNbO₃ is measured by means of near-forward Raman scattering, and described through the classical oscillator dispersion theory. The measured intensity and line-width of the Raman line are compared to those expected from theory.     

Magnetically insulated transmission line oscillator oscillated in a modified HEM11 mode

This paper puts forward a novel magnetically insulated transmission line oscillator (MILO) for the first time which takes a modified HEM11 mode as its main interaction mode. The excitation of the oscillation mode is made possible by carefully adjusting the arrangements of each resonant cavity in a two-dimensional (2-D) slow wave structure. The high frequency characteristics are analyzed and a PIC simulation is carried out; the detailed results are discussed to get a better understanding of this new MILO. Employing an electron beam of about 441 kV and 39.7 kA, it finds that the modified HEM11 mode MILO generates a high power microwave output of about 1.47 GW at 1.45 GHz. The power conversion efficiency is about 8.4% and the generated microwave is in a TE11-like circularly polarized mode; its polarization direction is decided by the rotation direction of the SWS.     

The development of nonradiative dielectric waveguide transmitting front-end in Ka-band

The operating theory,design method and experimental results of the nonradiative dielectric waveguide (NRD-guide) transmitting front-end in millimeter wave band are related in details in this paper. As a kind of dielectric waveguide,the NRD-guide possesses fine transmission performances, and it can be used to fabricate the millimeter wave hyterodyne integrated circuits. The two kinds NRD-guide transmitting front-ends substantiated in the paper, the voltage controlling oscillator(VCO) and twin-Gunn-diode power-combiner,have very similar structures to each other and possess compact sizes, fine machinery and electric performances.For the VCO front-end in Ka-band, the frequency modulation band is greater than 150MHz, the output power is larger than 20mW.For the power-combiner, the output power is larger than 40mW,the combination efficiency is better than 90%,the frequency stabilization reaches 1.68×10^–5. Combined with the receiving front-end reported before,the transmitter and receiver can be composed to a dielectric waveguide R/T module to be applied in some millimeter wave sub-systems.     

A Noteworthy Trap in Using the EDC Method for Solving Dielectric Waveguide Problems

EDC method is probably the simplest method to obtain a good approximation for the propagation constant of a dielectric waveguide. It is well know that there are two ways to perform the EDC procedure: one is to treat the LSE mode first then the LSM mode and the other is just reverse. It is true that the difference between the results got from the two ways is usually rather small and thus both of them are good approximations. In this paper, we show that in some cases the two ways will lead to much different results; one is still a good approximation while the other is completely unacceptable. The theoretical analysis tells us that if performing the LSM mode first then with the LSE mode will usually get a good result.     

Orientation effects on the bandgap and dispersion behavior of 0.91Pb（Zn_（1/3）Nb_（2/3））O_3-0.09PbTiO_3 single crystals

0.91Pb(Zn_1/3Nb_2/3)O₃--0.09PbTiO₃ (PZN--9%PT) single crystals with different orientations are investigated by using a spectroscopic ellipsometer, and the refractive indices and the extinction coefficients are obtained. The Sellmeier dispersion equations for the refractive indices are obtained by the least square fitting, which can be used to calculate the refractive indices in a low absorption wavelength range. Average Sellmeier oscillator parameters E_o, $\lambda$_o, S_o, and E_d are calculated by fitting with the single-term oscillator equation, which are related directly to the electronic energy band structure. The optical energy bandgaps are obtained from the absorption coefficient spectra. Our results show that the optical properties of [001] and [111] poled crystals are very similar, but quite different from those of the [011] poled crystal.     

Magnetic modes in a resonator built around a circular evanescent waveguide and coaxial line

The eigenfrequencies of magnetic modes in a resonator made up of two segments of a circular evanescent waveguide and a coaxial line are found by solving an electrodynamic problem. For the fundamental H_11dH_{11\delta } mode, the performance of the resonator is studied analytically and experimentally over a wide range of its parameters. The feasibility of a high-power microwave semiconductor oscillator based on the resonator under study is demonstrated.     

光子晶体高功率微波模式转换器设计

研究了传输线中非截面排列金属光子晶体电磁特性,并利用其作为移相器提出了一种紧凑型TEM—TE11模式转换器的设计方法.利用电磁软件cst microwave studio优化设计了一套L波段TEM—TE11模式转换器,在中心频率1.58 GHz上转换效率为98%.在1.56—1.625 GHz频率范围内,模式转换器转换效率大于90%,对应带宽4.1%.模式转换器功率容量为GW级,适用于高功率微波源系统.结合磁绝缘线振荡器开展了粒子模拟研究工作,发现模式转换器性能与设计结果相符,并且其引入不影响高功率微波器件的正常工作.     

Thickness dependent optical dispersion parameters and nonlinear optical properties of nanostructured Cr doped CdO thin films

Cr doped CdO thin films were deposited on glass substrates by reactive DC magnetron sputtering with varying film thickness from 250 to 400 nm. XRD studies reveal that the films exhibit cubic structure with preferred orientation along the (2 0 0) plane. The optical transmittance of the films decreases from 92 to 72%, whereas the optical energy band gap of the films decreased from 2.88 to 2.78 eV with increasing film thickness. The Wemple–DiDomenico single oscillator model has been used to evaluate the optical dispersion parameters such as dispersion energy (E_d), oscillator energy (E_o), static refractive index (n_o) and high frequency dielectric constant (ε_∞). The nonlinear optical parameters such as optical susceptibility (χ⁽¹⁾), third order nonlinear optical susceptibility (χ⁽³⁾) and nonlinear refractive index (n₂) of the films were also determined.     

The first high-resolution analysis of the 10-μm absorption of thioformaldehyde

The 10 μm region of thioformaldehyde (H₂CS) has been recorded at high resolution (0.005 cm⁻¹) using a Fourier transform spectrometer. H₂CS was produced by low-pressure pyrolysis of a gas flow of C₃H₅SCH₃ in Ar at 560 °C or CH₃SCl at 1150 °C, which was introduced into a multipass White cell with an optical path length of 32 m. Forty scans were recorded for the range 750-1400 cm⁻¹ at a total pressure of 0.15 mbar. A thorough analysis of the three lowest wavenumber fundamental bands, ν₃, ν₄ and ν₆, which fall in this region, has been carried out using a Hamiltonian model, which takes explicitly into account the numerous resonances affecting the ro-vibrational energy levels; especially the massive A-type Coriolis resonance between the out-of-plane wagging mode, ν₄, and the in-plane rocking mode, ν₆. These two modes are only separated by 0.83 cm⁻¹, and they are thoroughly mixed. From the fittings, the following band centers were derived: ν_o (ν₄)=990.18213(40) cm⁻¹, ν_o (ν₆)=991.02021(50) cm⁻¹ and ν_o (ν₃)=1059.20476 (30) cm⁻¹ where the uncertainties are one standard deviation. In addition, a number of relative line intensities were measured permitting the determination of relative values of the first-order transition moments and therefore relative band intensities for all three bands. Finally, a comprehensive list of line wavenumbers and relative intensities has been generated.     

FULLY RELATIVISTIC CALCULATIONS OF THE ENERGIES, OSCILLATOR STRENGTHS AND EINSTEIN COEFFICENTS OF THE FORBIDDEN TRANSITIONS FOR Ne-LIKE SEQUENCES

We provide systematic calculations about the energy levels, Einstein coefficients and oscillator strengths for electric quadrupole (E2) and magnetic quadrupole (M2) transitions between n=3 and n=2 of Ne-like systems by using the fully relativistic multi-configuration Dirac-Fock method. The oscillator strengths of the E2 transitions under Coulomb and Babshkin gauges are compared with each other and show the differences from 1.2 to 12 percent. We also found that the M2 line (0.37429 nm) with the biggest oscillator strengths in Ne-like Ag³⁷⁺ mixes with the line (2p⁵_3/23s_1/23d_5/2)_3/2→gs (0.37427 nm) emitted by the Na-like Ag³⁶⁺.     

Measurement of the transition strength of the 00o2 9.4 μm sequence band in CO2 using a tunable diode laser

We report the first accurate measurements of the transition strengths and linewidths of the 00^o2 9.4 μm sequence lines of CO₂. This sequence band is found to be very similar to the regular 00^o1 laser band, except for an experimentally determined factor of 1.89±0.12 increase in transition strength (if the CO₂ molecule is treated as a simple harmonic oscillator the theoretical increase in transition strength is 2.0). The laser absorption spectrometer used for these measurements can detect absorption coefficients in CO₂ of ≈10⁻⁷ m⁻¹, and we discuss the feasibility of using this sensitivity to monitor rare isotopic forms of CO₂. Work supported by the Department of National Health and Welfare, Environment Canada, Ontario Ministry of the Environment, and Atmospheric Environment Service, Environment Canada.     

Anelastic and dielectric relaxation of scandia-doped ceria

Of all the trivalent dopants which may be added to ceria (CeO₂) to make it an oxygen-ion conductor, Sc³⁺ appears to be unique in producing unusually low conductivity due to a relatively high vacancy-dopant association energy. In order to better understand the defect structure of Sc³⁺-doped ceria, the present work was undertaken using both anelastic and dielectric relaxation. A number of relaxation peaks were found. Most strikingly, a new low temperature relaxation with activation enthalpy near 0.2 eV was observed; it was shown to be due to a low-symmetry off-center configuration of an isolated Sć_Ce defect. At higher temperatures the relaxation due to Sc-V_o pairs (where v_o = oxygen vacancy) was found to have an activation enthalpy of 0.41 eV (much lower than that of larger dopant ions, e.g. Y³⁺ and Gd³⁺. In addition, complex relaxation spectra are observed even for concentrations as low as 0.3mol% Sc₂O₃, showing that higher clustered defects readily form in this system.     

Photoacoustic spectroscopy of formaldehyde with tunable laser radiation at the parts per billion level

Selective and sensitive detection of formaldehyde (CH₂O) was achieved using a grazing-incidence optical parametric oscillator (GIOPO), pumped at high repetition rate, as a light source for photoacoustic spectroscopy. The photoacoustic spectrum of formaldehyde was measured in the range from 2785 to 2840 cm^-1 and an absorption line at 2805.0 cm^-1 was selected for detection. Concentrations down to 20 ppbv (parts per billion by volume) formaldehyde in nitrogen were recorded. The detection limit determined by background fluctuations was 3 ppbv (S/N=1) for 3 s lock-in time constant and 3 min acquisition time. The 2805.0 cm^-1 absorption line of the ν₁ vibrational mode was chosen because of the absence of interference with water and carbon-dioxide bands. This allowed the direct detection of formaldehyde in laboratory air without filtering. PACS 42.62.Fi; 42.68.Ca; 42.65.Yj; 07.07.Df     

Composite (La,Sr)MnO3–YSZ cathode for SOFC

(La, Sr)MnO₃ (LSM)–Y doped ZrO₂ (YSZ) composite was prepared using YSZ colloidal suspension (initial YSZ particle size ∼100 nm), YSZ and LSM polymer precursors on dense substrates at 800 °C annealing temperature. The results of a symmetrical LSM–YSZ composite cell test showed the area specific resistance for overpotential of 0.14 Ω cm² at 800 °C, which indicated that the LSM–YSZ composite could be a potential candidate for cathode in SOFCs. The performance of the cell with the LSM–YSZ composite cathode and Ni-YSZ anode was investigated and the power density of about 0.26 W cm^− 2 was obtained at 850 °C using hydrogen fuel.