An Integrated Millimeter-Wave Broadband Microstrip-to-Waveguide Vertical Transition Suitable for Multilayer Planar Circuits
An integrated broadband vertical microstrip-to-rectangular waveguide (RWG) transition at Ka-band is presented. This transition is especially suitable for multilayer planar circuits, by utilizing a section of multilayer three-dimensional (3-D) stepped substrate integrated waveguide (SIW) structure, along with a taper transition. A simplified initial transition model from 3-D stepped SIW to waveguide is first optimized, thereafter, a full microstrip-to-waveguide transition is constructed and further optimized. For demonstration, some back-to-back transition prototypes are fabricated by multilayer PCB processing. The experimental results show that the return loss better than 15 dB is obtained from 33 to 36.7 GHz, with the minimum net insertion loss about 0.7 dB for a single transition at 35 GHz.
Bandwidth Extension of Planar Microstrip-to-Waveguide Transition by Controlling Transmission Modes Through Via-Hole Positioning in Millimeter-Wave Band
This paper presents a design technique to achieve a broadband planar microstrip-to-waveguide transition in a millimeter-wave (mmWave) band. In the conventional planar microstrip-to-waveguide transition, via holes are located around the rectangular waveguide and microstrip line to prevent power leakage due to the generation of a multi-transmission mode. Therefore, a single-transmission mode is dominant at the input port of the transition, with a narrow bandwidth of the single resonance. In the broadband planar microstrip-to-waveguide transition, via-hole positioning is utilized to add inductance to constrain the predominance of the single-transmission mode at the input port of the transition. The double-resonant frequency yielded by excitation of the grounded coplanar waveguide transmission mode and parallel plate transmission mode is obtained by controlling the positions of holes adjacent to the microstrip line. Moreover, to simplify the structure and meet the requirement of high assembly accuracy in fabrication, two holes adjacent to the microstrip line are maintained, but the remaining holes are replaced by a choke structure that performs the equivalent function to the via-hole arrangement. The influences of the multi-transmission mode and choke structure on the characteristics are investigated by electromagnetic analysis, and the feasibility is confirmed by experiments in this work. A double-resonant frequency and a broad bandwidth of 10.6 GHz (13.8%) are obtained. The measured results of the broadband planar microstrip-to-waveguide transition using via-hole positioning show an insertion loss of 0.41 dB at the center frequency of 76.5 GHz.
Fragment Rotational State Distributions From The Dissociation Of NeIBr: Experimental And Theoretical Results
The IBr fragment rotational state distributions that result when the NeIBr van der Waals molecule undergoes vibrational predissociation have been measured in a pump–probe laser‐induced fluorescence experiment. Independent of initial vibrational state and the number of quanta of vibrational energy lost from the I–Br coordinate, the rotational distributions extend over the full range of energetically accessible states. From the observation of energetic constraints on the rotational distribution, the dissociation energy (D0) is calculated to be 65.5±1.2 cm−1 for the A electronic state, v=16. For the X electronic state, v=0, D0=71.8±1.2 cm−1. Quantum mechanical bound state calculations carried out on a model A electronic state potential energy surface are in quantitative agreement with this result. The rotational distributions are broader than that predicted by either a Franck–Condon or classical impulsive model for the dissociation. The distributions are qualitatively in accord with classical trajectory calc...