Millimeter-wave Microwave Research Articles

A microwave/millimeter-wave triple-band shared-aperture antenna integrating differentially-fed patch and transmitarray

This paper presents a microwave (MW)/millimeter-wave (MMW) triple-band shared-aperture antenna. It is implemented by integrating a differentially-fed patch (3.6 GHz) and a dual-band transmitarray (TA) (26 GHz and 39 GHz) through structure reuse. To realize an efficient integration, the patch antenna is evolved from a single-layer structure to a multi-layer one, with an extended ring-shaped patch added in each layer to obtain a proper transmitting surface (TS) size. For the TA, it adopts a unit cell (UC) consisting of two interleaved slots. By adjusting the lengths of the slots, independent dynamic phase shifts covering 360∘ can be attained for the 26 GHz and 39 GHz bands, respectively. To achieve an appropriate focal-to-diameter ratio (F/D) for the TA, a frequency selective surface (FSS) is employed to replace the ground plane of the patch antenna. Thanks to the spatial feeding architecture of the TA, the proposed antenna eliminates the need of complicated feeding network and features low feeding loss and high gain in the MMW bands. To validate the design idea, a prototype is fabricated and measured. The experimental results demonstrate that the proposed antenna can successfully operate in the three bands with peak gain of 7.6 dBi, 19.3 dBi and 19.5 dBi, respectively. In the 26 GHz and 39 GHz bands, beam scanning ranges of ±25∘ and ±13∘ can be obtained, respectively. The proposed antenna can be a promising candidate for 5G multi-band applications.

Severe perturbation and observation of forbidden transitions in asymmetrically deuterated methanol (CHD2OH) and atlas of very accurate torsional rotational spectrum obtained using Synchrotron radiation

High-resolution spectral studies have been continued for the doubly deuterated methanol species (CHD2OH) in the entire region from far infrared (FIR) to Infrared (IR). The spectrum has been obtained using a conventional Fourier transform spectrometer and the state-of-the-art Synchrotron radiation-based spectrometer with unprecedented resolution and very high signal-to-noise (S/N). During the investigation severe perturbation was encountered. The perturbation has been characterized as due to first and second-order Coriolis interaction. The interaction affected a wide range of states and caused the spectral study quite challenging. The perturbation caused a variety of mixing of states producing hybrid states. This hybridization resulted in producing a large number of transitions which should not be allowed by the dipole selection rules via the “intensity borrowing effect”. It was possible to identify a large number of such forbidden transitions that gain sufficient strength through the “Intensity borrowing” effect. The transitions connecting to these perturbed states have been analyzed using standard Coriolis interaction formulae. The possibility of “Fermi” interaction has been excluded as the interaction is highly dependent on the rotational quantum number J. In general, this kind of transition should be excluded from global analysis and should be treated in isolation. It is pertinent to note that some previously published works studied these states using un-substantiated assignments being perhaps unaware of the perturbation. Corrections have been suggested for the analysis and understanding of the properties of the energy levels which have subtle differences with the energy levels of normal asymmetric molecules. In all, available microwave (MW) millimeter wave (MMW) far infrared (FIR), and infrared (IR) assignments have been put together to prepare the most accurate and and complete atlas of about 12,000 spectral lines. This atlas (Appendix A) should be considered a work-in-progress supplement to this paper and supersedes all other lists known to date on this species can be had from one of us (IM) or via Researchgate.

A Bidirectional Fiber-Wireless and Fiber-IVLLC Convergence System with a Dual-Polarization Modulation Scheme and an MZM-OEO-Based BLS

A bidirectional fiber-wireless and fiber-invisible laser light communication (IVLLC) convergence system that adopts a dual-polarization modulation scheme and a Mach–Zehnder modulator (MZM)-optoelectronic oscillator (OEO)-based broadband light source (BLS) for hybrid cable television (CATV)/microwave (MW)/millimeter-wave (MMW)/baseband signal transmission is proposed and experimentally demonstrated. The MZM employed in the MZM-OEO is operated at the minimum transmission point, which results in the format of optical carrier suppression for the y -axis component of the light. Using a dual-polarization modulation scheme, the optical carrier modulated with CATV signal ( x -polarization) and the optical sidebands modulated with MW and MMW data signals ( y -polarization) are separated and polarized orthogonally automatically. Through an in-depth observation, good carrier-to-noise ratio, composite second-order, composite triple-beat, and bit error rate performances are obtained over a 40-km single-mode fiber and a 10-m RF/100-m optical wireless transport. Such a bidirectional fiber-wireless and fiber-IVLLC convergence system is a notable option; it would be attractive for providing broadband heterogeneous services such as CATV, Internet, and big data services.

Bidirectional fiber-wireless and fiber-IVLLC integrated system based on polarization-orthogonal modulation scheme.

A bidirectional fiber-wireless and fiber-invisible laser light communication (IVLLC) integrated system that employs polarization-orthogonal modulation scheme for hybrid cable television (CATV)/microwave (MW)/millimeter-wave (MMW)/baseband (BB) signal transmission is proposed and demonstrated. To our knowledge, it is the first one that adopts a polarization-orthogonal modulation scheme in a bidirectional fiber-wireless and fiber-IVLLC integrated system with hybrid CATV/MW/MMW/BB signal. For downlink transmission, carrier-to-noise ratio (CNR), composite second-order (CSO), composite triple-beat (CTB), and bit error rate (BER) perform well over 40-km single-mode fiber (SMF) and 10-m RF/50-m optical wireless transport scenarios. For uplink transmission, good BER performance is obtained over 40-km SMF and 50-m optical wireless transport scenario. Such a bidirectional fiber-wireless and fiber-IVLLC integrated system for hybrid CATV/MW/MMW/BB signal transmission will be an attractive alternative for providing broadband integrated services, including CATV, Internet, and telecommunication services. It is shown to be a prominent one to present the advancements for the convergence of fiber backbone and RF/optical wireless feeder.

Fiber-Wireless and Fiber-IVLLC Convergences Based on MZM-OEO-Based BLS

Fiber-wireless and fiber-invisible laser light communication (IVLLC) convergences that adopt the Mach–Zehnder modulator-optoelectronic oscillator (MZM-OEO)-based broadband light source for microwave (MW)/millimeter-wave (MMW)/baseband (BB) signal transmission are proposed and demonstrated. For downlink transmission, light is optically promoted from 15- and 25-GHz radio-frequency (RF) signals to 10-Gb/s/30-GHz MW, 15-Gb/s/50-GHz MMW, 20-Gb/s/60-GHz MMW, and 25-Gb/s/100-GHz MMW data signals based on fiber-wireless and fiber-IVLLC integrations. Bit error rate (BER) performs efficiently in the 40-km single-mode fiber (SMF) and the 10-m RF/25-m optical wireless transport scenarios. For uplink transmission, downstream light is successfully intensity-modulated with a 25-Gb/s BB data stream based on fiber-IVLLC integration. BER performs efficiently in the 40-km SMF and the 100-m optical wireless transport scenario. Such a hybrid MW/MMW/BB lightwave transmission system is an attractive alternative. It is shown to be a prominent one to present advancements in integrating fiber backbone and radio-frequency (RF)/optical wireless feeder networks.

Employing injection-locked FP LDs to set up a hybrid CATV/MW/MMW WDM light wave transmission system.

A hybrid cable television (CATV)/microwave (MW)/millimeter-wave (MMW) wavelength-division-multiplexing (WDM) light wave transmission system based on injection-locked Fabry-Perot laser diodes (FP LDs) is proposed and demonstrated. Different from conventional hybrid WDM light wave transmission systems, which need wavelength-selected distributed feedback laser diodes to support various services, the proposed systems employ injection-locked FP LDs to provide multiple applications. Over a 40 km single-mode fiber transport, impressive performances of carrier-to-noise ratio/composite second-order/composite triple-beat/bit error rate are obtained for 550 MHz CATV/20 GHz MW/40 GHz MMW/60 GHz MMW signal transmissions. Such a hybrid WDM light wave transmission system would be attractive for fiber links to provide broadband integrated services.

Fourier transform microwave spectroscopy and Fourier transform microwave–millimeter wave double resonance spectroscopy of the ClOO radical

Pure rotational spectra of the ClOO radical for the (35)Cl and (37)Cl isotopomers have been observed using Fourier transform microwave and Fourier transform microwave-millimeter wave double resonance spectroscopy. The rotational, centrifugal, spin-rotation coupling, and hyperfine coupling constants have been determined by least-squares fits of the observed transition frequencies. The molecular constants indicate that the electronic ground state is 2A". The r(0) structure is determined to be r(0)(ClO)=2.075 A, r(0)(OO)=1.227 A, and theta;(0)(ClOO)=116.4 degrees . Several highly accurate ab initio calculations have also been performed. Some of them turned out to be inaccurate because it is necessary to take into account both static and dynamic electronic correlations. Only multireference (single and double) configuration interaction calculations with large basis sets reproduce the present experimental results. The anharmonic force constants obtained by the ab initio calculations are used to determine the r(e) structure, r(e)(ClO)=2.084(1) A, r(e)(OO)=1.206(2) A, and theta;(e)(ClOO)=115.4(1) degrees . Unique features of the ClOO radical have become clear by the present experiment and the ab initio calculations.

The CO dimer: new light on a mysterious molecule

The present state of research on the CO dimer is reviewed. In recent years, both infrared and millimeter-wave spectra have been measured and partially assigned by the use of combination differences. A microwave-millimeter wave double resonance experiment, reported here for the first time, provides independent confirmation of these assignments and the resulting (CO) 2 energy level scheme. In the double resonance experiment, the OROTRON spectrometer functions as a supersensitive intra-cavity millimeter-wave detector. We update the continuing, but difficult, experimental efforts in recording the spectra, the quest for secure assignments, and the construction of a consistent and reliable energy level scheme. Although at present we have only limited knowledge of some aspects of the CO dimer, such as its geometrical structure, we have succeeded in characterizing unambiguously nine “stacks” of ground state energy levels with “microwave accuracy” (∼0.1 MHz). Every energy level within a given stack exhibits the same symmetry: either A − or A +. Only transitions between A + and A − levels are allowed, and consequently ordinary pure rotational transitions within a stack are forbidden. Transitions between stacks can be thought of as tunneling transitions, and the separation of the lowest energy A + and A − states corresponds to a value of 3.73 cm 1 for the effective “tunneling splitting” of the CO dimer. The stacks tend to fall into two groups, corresponding to “isomers” with effective inter-molecular separations of either 4.0 or 4.4 Å. The larger inter-molecular separation of the true ground state (4.4 Å) likely corresponds to a C-bonded configuration, while the low-lying (0.88 cm −1) excited state with the smaller separation (4.0 Å) likely displays an O-bonded geometry.

Global Fit of Torsion–Rotational Transitions in the First Three Torsional States of CH3OD

A global fit of the observed high-resolution microwave (MW), millimeter-wave (MMW), and Fourier transform far-infrared (FIR) spectra for CH3OD has been performed using a reduced torsion–rotational Hamiltonian that is obtained from the one-large-amplitude internal-rotation model. The CH3OD data set contains 460 MW and MMW transitions with two or fewer quanta in the torsion, vt ≤ 2, and 2348 Fourier transform FIR transitions with vt ≤ 1 and J ≤ 21. The MW and MMW transitions have been fitted with a root-mean-square (rms) deviation of 0.11 MHz (0.098 MHz for J ≤ 10) while FIR transitions have a rms deviation of 0.0002 cm−1. These deviations are approximately equal to the experimental uncertainties, indicating that the MW, MMW, and FIR spectral transitions have been fit to experimental accuracy.

Microwave and millimeter wave study of Ortho-N2 states of CO–N2

Microwave and millimeter wave transitions of the CO–N2 complex were investigated using three different instruments, namely, a pulsed molecular beam Fourier transform microwave spectrometer in the frequency region from 4 to 26 GHz, a microwave-millimeter wave double resonance spectrometer in the frequency regions from 8 to 18 GHz for the microwave and 107–118 GHz for the millimeter wave range, and an OROTRON spectrometer in the frequency range from 107 to 132 GHz. Both a- and b-type transitions associated with the ground-state K=0 levels and the lower K=1 levels of the ortho-N2 states, and with rotational quantum number J up to 19, were measured and analyzed. Nuclear quadrupole hyperfine splittings due to the presence of two equivalent N14 nuclei were resolved and analyzed to give additional information about the angular anisotropy of the interaction potential. The nuclear quadrupole coupling constants obtained are χaa=0.196 41(52) MHz for K=0 levels, and χaa=−1.0391(17) MHz, χbb=0.0633(17) MHz for the lower K=1 levels, respectively. The drastic difference between these two sets of coupling constants suggests that the orientation and motion of the N2 subunit are very different in these two states, and that the complex cannot be adequately described by a semirigid rotor model. In addition, measurements of the rotational spectra of the two new isotopomers containing C13O16 and C13O18 subunits provide further important information about the CO–N2 interaction potential.

Global Fit of Torsion–Rotation Transitions in the Ground and First Excited Torsional States of CD3OH Methanol

A global analysis of reported microwave (MW) millimeter wave (MMW), and Fourier-transform far-infrared (FTFIR) spectra of the CD3OH isotopic species of methanol has been carried out for the first two torsional states (νt= 0 below the barrier and νt= 1 straddling the barrier) of the ground vibrational state. The CD3OH data set contains 472 MW and MMW lines and 5320 FTFIR lines, representing the most recent available information in the quantum number rangesJ≤ 20 andK≤ 15. The transitions have been successfully fitted to within the assigned measurement uncertainties of ±100 kHz for most of the MW and MMW lines and ±6 MHz for the FIR lines with the use of a program (I. Kleiner and M. Godefroid, private communication) based on the formalism of Herbstet al.(J. Mol. Spectrosc.108,42–57, 1984). A convergent global fit was achieved using 54 adjustable parameters to reach an overall weighted standard deviation of 0.966. The new parameters for CD3OH are compared with previous global fitting results for the12CH3OH and13CH3OH isotopomers.

Effective fourth order torsion-rotation Hamiltonian parameters of C-13 methanol

In this work, the effective fourth order Hamiltonian parameters of 13C substituted methanol were determined using microwave (MW), millimeterwave (MMW) and Fourier transform far-infrared (FIR) assigned transitions in the ground and first excited torsional states. The data set consisted of 1060 transitions with the rotational angular momentum J < 13 (with 416 FIR lines). The data set was fitted with a recently developed effective Hamiltonian model to derive the molecular parameters. The results indicate that the model developed for the parent methanol species is valid for the C-13 substituted species also. The results will allow the energy levels of the molecule to be calculated with improved precision which will be of use for the discovery of new FIR laser emission in C-13 methanol and the discovery of this molecular species in interstellar space.