Microwave And Millimeter-wave Research Articles

A Microwave/Millimeter-Wave Shared-Aperture Antenna Based on Slow-Wave Parallel-Plate Waveguide

Since the coexistence of microwave (MW) and millimeter-wave (MMW) technologies has become the inexorable trend of emerging wireless communication systems, the corresponding antennas are required to support two frequency bands simultaneously. However, the existing MW/MMW shared-aperture antennas are facing challenges in dealing with the interference between two bands and implementing beam steering at both bands. To address these issues, a windowed slow-wave parallel-plate waveguide (WSW-PPW) is proposed as the sharing platform, on which MW and MMW antenna elements can be flexibly arranged. WSW-PPW is implemented by embedding electromagnetic bandgap (EBG) structures into a dual-layer printed PPW. At the MW band, WSW-PPW exhibits a transmission feature for feeding and also integrating MW antenna elements. At the MMW band, WSW-PPW rejects the propagation of electromagnetic waves and functions as artificial magnetic boundaries for dielectric resonator antennas, which are realized by removing subarrays of EBG structures. For demonstration, an MW/MMW shared-aperture antenna is implemented by integrating a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times $ </tex-math></inline-formula> 2 MW patch array and a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times $ </tex-math></inline-formula> 8 MMW array on this platform. Steerable beams had been independently achieved at both bands. The antenna is fabricated and experimentally verified. The measured results show a reasonable agreement with simulations.

Crystallographically Textured and Magnetic LaCu-Substituted Ba-Hexaferrite with Excellent Gyromagnetic Properties

Excellent gyromagnetic properties of textured, bulk Ba-hexaferrite samples are required for low-loss, self-biased applications for microwave and millimeter-wave (MMW) devices. However, conventionally processed bulk Ba-hexaferrite ceramics typically demonstrate low remanent magnetization values, 4πMr, of 2.0~3.0 kG, and relatively large ferromagnetic resonance (FMR) linewidths, ΔHFMR, of 0.8~2 kOe. These properties lead to the development of high-performance, practical devices. Herein, crystallographically textured Ba-hexaferrite samples, of the composition Ba0.8La0.2Fe11.8Cu0.2O19, having excellent functional properties, are proposed. These materials exhibit strong anisotropy fields, Ha, of ~14.6 kOe, high remanent magnetization, 4πMr, of 3.96 kGs, and a low ΔHFMR of 401 Oe at zero-bias field at the Q-band. Concomitantly, the broadband millimeter-wave transmittance was utilized to determine the complex permeability, μ*, and permittivity, ε*, of textured hexaferrites. Based on Schlöemann's theory of complex permeability, μ*, the remanent magnetization, 4πMr, anisotropy field, Ha, and effective linewidth, ΔHeff, were estimated; these values agree well with measured values.

A Dual-Band Shared-Aperture Antenna for Microwave and Millimeter-Wave Applications in 5G Wireless Communication

The shared-aperture integration of microwave (MW) and millimeter-wave (MMW) band antennas has attracted lots of attention and interests recently. However, few designs, to date, can simultaneously satisfy the requirements of compact size for MW antenna, beam steerable array for MMW antenna, appreciable bandwidths for both bands, and high isolation between the two bands. In this communication, a dual-band 3.5/28 GHz shared-aperture antenna is proposed to solve this issue. By embedding two MMW <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times $ </tex-math></inline-formula> 2 subarrays to the MW perforated patch antenna, the two antenna types can be accommodated in a shared volume and integrated into the same structure. The shared-aperture antenna, which has a very compact size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.4\times 0.26\times 0.04\,\,\lambda ^{3}_{01}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{01}$ </tex-math></inline-formula> is the wavelength in the vacuum at 3.5 GHz), can be used as an array element to form the MW MIMO system and MMW beam-steering array. A validation array model with two cells is fabricated and measured. Measured results show that the antenna can cover a dual band of 3.38–3.64 GHz (7.4%) and 26.4–29.8 GHz (12.1%). The peak gains of 6.9 and 14.6 dBi are obtained by the single MW element and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times $ </tex-math></inline-formula> 2 MMW array, respectively. The MMW array can support ±30° beam scanning in the H-plane. The channel isolation between the two bands can be more than 45 dB at 3.5 GHz and 40 dB at 28 GHz.

Accurate 3-D Microwave Near-Field Imaging of Typical Concave Objects

High-resolution microwave and millimeter-wave (MMW) detection and recognition are often plagued with artifacts when facing complex objects with concave structures due to the ignorance of high-order scattering propagation. Previous works have demonstrated the effectiveness of accurate near-field reconstruction by considering multiple reflections reconstruction in planar dihedral structures. In this letter, we extend the proposed imaging model to three-dimensional (3-D) imaging scenario. Based on the shooting and bouncing ray (SBR) concept, we first analyze the mechanism of multiple scattering and establish a 3-D forward model. Utilizing circularly polarized measurements, each number of reflection times (RTs) echo can be separated. Also, by calculating and compensating for the multiple reflection propagation paths, the accurate 3-D reconstruction of dihedrals is realized. Numerical simulations and experiments show that the proposed method can obtain the high resolution in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$z$ </tex-math></inline-formula> -axis and effectively restore the pattern of reflectivity distribution on the target surface.

Very high-resolution Synchrotron radiation far infrared spectrum of C-13 methanol arising from the ground torsional vibrational state and evidence of avoided crossing due to ΔK = 4 interaction

In this work, very high-resolution far-infrared (FIR) and infrared (IR) Synchrotron Radiation spectra of C-13 substituted methanol species have been recorded with very high signal-to-noise (S/N) ratio in the entire region from 40 to 5000 cm−1. High resolution allowed the recording to be done with an unprecedented resolution of about 0.0014 cm−1 which is on the order of the doppler width of the lines. The peak of the spectral lines could be obtained with an estimated accuracy of ± 5 KHz. Analysis of the spectra has been performed for quantum numbers associated with the torsional ground state. Assignments have been obtained for K- values up to about 15 and J- values of about 35 for the three symmetry species. Asymmetry splitting has been observed for low K transitions and accurate asymmetry splitting constants have been obtained. Including the available microwave (MW) and millimeter-wave (MMW) measurements, a complete set of spectral line assignments have been obtained for the ground torsional state of the vibrational state. Following J.K. Watson’s method [1] all the spectral lines have been fitted to the exact term values of the energy levels. Localized perturbation has been observed for K = 9 A and state mixing resulted in forbidden transitions through intensity borrowing. A complete atlas has been presented for all possible quantum numbers for the ground state levels and the accurate term values have been obtained for all possible states. According to our knowledge, this atlas represents the most accurate line positions for this species reported so far. In addition, the results have been applied to confirm and obtain very accurate wavenumbers for several FIR laser lines pumped by CO2 lasers. The present atlas may be useful as a secondary wavenumber standard in the FIR region and should be useful for astrophysical detection.

Single‐fed dual wideband filtenna for 4G / 5G mobile applications

This article presents a single-fed single-layer dual-band slotted antenna which has the ability to simultaneously operate at microwave and millimeter-wave (MMW) frequency bands. It consists of a rectangular slotted ground plane, double cascaded tuning stubs, and embedded MMW element of L-shape inside the slotted ground. Ultra-wideband bandstop filter (BSF) is inserted at the feeding for isolating the two operational bands. The BSF consists of 3-open circuited stubs and in-line coupled line section. For demonstration, a design prototype of the complete integrated filtenna is fabricated and measured. Good agreements between simulated and measured results are observed. The proposed filtenna operates at 5.2 and 28 GHz with impedance bandwidth (15.23% and 17.03%) and the gain reaches (4.09 and 6.18 dBi).

Accurate Near-Field Millimeter-Wave Imaging of Concave Objects—A Case Study of Dihedral Structures Under Monostatic Array Configurations

With the fast progress of high-resolution microwave and millimeter-wave (MMW) near-field imaging systems, image artifacts caused by complex high-contrast target become a nonnegligible issue for accurate surface reconstruction and recognition. Among different types of artifacts, those caused by high-order scattering within concave structures are particularly difficult to interpret and to correct. This article focuses on analyzing these unconsidered effects in conventional imaging or beamforming algorithms and chooses a typical imaging scenario with dihedral structures under near-field monostatic cylindrical imaging geometry for discussion. The mechanism of multiple reflections and the formation of artifacts are firstly investigated, and the artifacts are classified into two categories based on the number of reflection times. Then shooting and bouncing rays (SBRs) method is utilized to establish an analytical forward model including the mechanism of multiple reflections. Furthermore, a new imaging algorithm based on this forward model is proposed to obtain more accurate reconstructions. By compensating phase shifts of different multiple reflection signals with the corresponding range equations, dihedral-type objects with different opening angles can be accurately recovered. Numerical results are presented to verify the applicability of the forward model and to validate the effectiveness of the proposed imaging algorithm. In the end, experimental results confirm the practicability of the proposed method.

SPPs-Shared Dual-Band Antenna With Large Frequency Ratio

The operating frequency of future communication systems will cover both microwave and millimeter-wave (MMW) bands simultaneously. This paper presents a novel design of spoof surface plasmon polaritons (SPPs) structure-shared dual-band antenna with large frequency ratio, which consists of a planar open sleeve monopole antenna operating at S-band and a taper slot antenna (TSA) at K/Ka-band. In this design, the SPPs structure takes important roles in two aspects: it serves as an equivalent-lens to enhance the gain of TSA and a monopole of the planar open sleeve antenna to keep a low profile. To realize high isolation between the two antennas, a substrate integrated waveguide (SIW) and an integrated coaxial line are designed to feed the TSA and the planar open sleeve monopole antenna respectively. The SPPs-shared antenna shows an enhanced endfire gain of 13.09 dBi in the frequency range of 19.32-32.90 GHz and an omnidirectional gain of 1.06-2.92 dBi over the range of 2.23-3.69 GHz, keeping a compact size. The large frequency ratio of 10.8, low profile and the wide operating bands in both lower and upper frequency ranges can meet many wireless communication applications. Reasonable agreement between the measured and simulated results is observed.

Crystallographically textured Ba0.8La0.2Fe11.8-xCu0.2O19-δ hexaferrites with narrow FMR linewidth

M-type hexaferrites which exhibit strong uniaxial anisotropy field, are promising for the applications in self-biased microwave and millimeter wave (MMW) devices. Here we demonstrate crystallographically textured hexaferrites with narrow ferromagnetic resonance (FMR) linewidth synthesized by the conventional ceramic method. Meanwhile, the relationship between iron-deficiency content and microstructure, crystallographic, and magnetic properties are researched. These hexaferrites have strong remanence ratio of above 0.9 along c-axis. By fitting of Lorentzian function to absorption derivative, we probe detailedly into the zero-field FMR linewidth of Ba0.8La0.2Fe11.8-xCu0.2O19-δ hexaferrites. When x equals 1.0, it indicates the narrowest FMR linewidth of 324Oe, as compared with previous reports for crystallographically textured hexaferrites.

Rapid Manufacturing of Microwave Circuits on Low-Cost Substrates Using Laser Machining

Microwave and millimeter wave (MMW) planar structures are sensitive to printed circuit manufacturing tolerances. A promising alternative to the conventional photolithographic fabrication technique is laser structuring. This paper presents the study and the experiments conducted to investigate the possibility of employing low-cost commercially available substrates for microwave and MMW circuits using laser ablation process. At least two of such materials (a) glass reinforced ceramic filled teflon (PTFE) and (b) glass reinforced hydrocarbon have been used to design and fabricate microwave and MMW passive structures such as edge-coupled bandpass filter (BPF) using laser machining. The experimental results exhibit the suitability of glass reinforced hydrocarbon materials for microwave circuits employing laser ablation process. However, it is deduced that the laser ablation process alters the complex permittivity characteristics of the ceramic filled PTFE materials. The measured results of laser ablated passive structures on both materials are presented along with the simulation results.

Modeling and Performance of Microwave and Millimeter-Wave Layered Waveguide Filters

This paper presents the novel designs, analysis, and performance of 4-pole and 8-pole microwave and millimeter-wave (MMW) waveguide filters for operation at X and Y frequency bands. The waveguide filters have been designed and analyzed based on the mode matching and coupled resonators design techniques employing layered technology. Thorough waveguide filters working at X-band and Y-band have been designed, analyzed, fabricated, and tested along with the analysis of the output characteristics. Accurate designs of RF waveguides along with their filters based on the E-plane filter concept have been carried out with the ability of fitting into layered technology in high frequency production techniques. The filters demonstrate the appropriateness in order to develop high-performance well-established designs for systems that are intended for the multi-layer microwave, millimeter- and sub-millimeter-waves devices and systems; with the potential employment in radar, satellite, and radio astronomy applications. DOI: http://dx.doi.org/10.11591/telkomnika.v11i7.2411 Full Text: PDF

Dynamic range improvement strategy for Mach-Zehnder modulators in microwave/millimeter-wave ROF links

Intermodulation distortions are generated by Mach-Zehnder modulators when they are driven by signals with certain bandwidth in microwave (MW) and millimeter-wave (MMW) radio-over-fiber (ROF) links. The optical spectral structure of the distorted optical signal is investigated. A strategy to improve the dynamic range of MW and MMW ROF links directly in the optical domain is proposed and experimentally demonstrated. Based on optical spectrum processing, the third-order intermodulation distortions (IMD3s) of the generated signals are suppressed. A 107.2dB∙Hz2/3 spurious-free dynamic range (SFDR) of the MW/MMW ROF link is obtained, which is improved more than 20dB. A 16QAM signal is transmitted in the system and the error vector magnitude (EVM) is measured with and without the proposed technique. The influence of the nonlinearity of modulators on EVM is almost completely eliminated.

Basic Performance of Refractive Index Measurement Method for LC Materials in Super High Frequency Region by Using Coplanar Wave Guide

Novel measurement method of complex refractive indices of liquid crystal (LC) materials in the ultrahigh frequency region such as microwave and millimeter-wave (MMW) is investigated to reduce the quantity of test sample by using a coplanar waveguide (CPW) substrate, which is known as an excellent planar type waveguide. Although it needs some calibration method for precise measurement, the amplitude and phase properties of the propagating electromagnetic waves are sufficiently sensitive to the extremely small amount of test sample and the basic performance for the loss and refractive index measurements is investigated by using the well known K15 LC material.

A bidirectional radio over fiber system with multiband-signal generation using one single-drive MZM

We propose and experimentally demonstrate a simple and cost-effective bidirectional radio-over-fiber (RoF) system for transmission of downstream multiband signals and upstream data. At the central station (CS), the multiband data consisting of baseband, micro-wave (MW) and millimeter-wave (MMW) signals are generated using only one single-drive x-cut Mach-Zehnder modulator (MZM), which is driven by a clock signal at radio frequency (RF) port and an electrical data at bias port. Upstream data transmission is realized by re-modulation of filtered frequency-shift-keying (FSK) signal, selected from the multiband signals.

Microwave harmonic generation in fiber-optical links

Optical transmission of microwave (MW) and millimeter-wave (MMW) signals has become an intensive research area in the last decade. There is a growing interest in optical processing of MW signals [1, 2], phased array applications [3] and wireless distribution of broadband data in fiber-fed MMW subscriber access systems [4 - 10]. This paper extends the existing models of MW/MMW optical links that are based on optical intensity [10, 11]. The model is suitable for estimating harmonic levels of the MW modulation signal generated in the optical path. Considering a MW fiber-optic link both the optical transmitter and the receiver are responsible for harmonic generation. Furthermore, the optical fiber itself inserted between the transmitter and receiver induces harmonics due to dispersion. Exact modelling of harmonic generation requires a calculation based on the optical field instead of on a purely intensity basis [12 - 14].

Investigation for Arcing Phenomenon in High Power MW/MMW Tubes

The arcing phenomenon in high voltage is one of the main failure modes for high power microwave and millimeter wave (MW/MMW) tubes. According operating principle of vacuum electronic devices, the factors of leading the arcing are discussed and the approaches for eliminating the arcing phenomenon are given in this paper. The theoretical and designing foundation raising the reliability for MW/MMW tubes are provided.

Distributed MEMS phase shifters bymicrostereolithography on silicon substrates for microwave andmillimeter wave applications

A distributed microelectromechanical system (MEMS)phase shifter has been fabricated on a high-resistivity siliconsubstrate using a microstereolithography technique. Thistechnique enables us to decrease the early development cost byremoving the need for photomasks used for defining the MEMSbridges. The distributed MEMS phase shifter fabricated consistsof a high-impedance coplanar waveguide transmission lineand ten MEMS bridges of 4.5 µm height, which givesa phase shift of 6° at 18 GHz with a bias voltage of30 V. This MEMS bridge design can be improved further using themicrostereolithography technique to give a phase shift of nearly90° at 18 GHz with a bias voltage of 20 V. Thefabrication procedure described here shows significant promisefor the use of microstereolithography techniques for RF MEMSdevices for ground and space telecommunication applications.

High Resolution Fourier Transform Far Infrared Spectroscopy of CH3OD

The high resolution Fourier transform far infrared spectrum of the torsion rotation band of CH3OD has been recorded in the range 20–350 cm−1at a resolution of 0.002 cm−1. The spectrum shows splitting of the lines due to strong torsional, rotational, and vibrational interactions in the molecule. Assignments were possible for rotational subbands in the ground torsional state (n= 0) forKvalues up to 15 andJvalues of up to 30, for all the symmetry species. In addition, some subbands were also identified which involve torsionally excited states. A total of 63b-type subband origins, including 6Q-branch origins obtained from microwave (MW) and millimeter-wave (MMW) studies, were fitted to a semiempirical model. The molecular parameters so determined were able to reproduce the subband origins almost to within experimental uncertainty. The torsional–rotational state-dependent effective molecular parameters and the asymmetry splitting parameters have also been determined. These should prove valuable in the assignment of transitions involving torsionally excited states in the ground vibrational state.

Methods of using commercial electromagnetic simulators for microwave and millimeter-wave circuit design and optimization

Efficient utilization of commercial electromagnetic (EM) simulators for design and optimization of microwave (MW) and millimeter-wave (MMW) circuits is achieved by classifying design problems into three categories-characterization of circuit elements, optimization of circuit elements, and creation of circuit element libraries such as scalable libraries. Practical aspects of the methods are illustrated by several examples. An equivalent circuit extraction technique suitable for n-port coupled structures is provided. The derived equivalent circuit is useful for extrapolating data, optimization, and deriving scalable models.