This paper examines an efficient low phase noise oscillator using a high Q resonator and harmonic suppression filter. The oscillator is designed using a combined bandpass filter (BPF), which is used as a feedback element to an amplifier. The filter consists of an embedded spur line filter in the L-shaped input and output section which encloses a perturbed square ring. All of these sections are assembled to form a combined BPF which gives an excellent suppression of second and third harmonics. Low phase noise oscillator results are evaluated at 2 V power supply. The measured results show the fundamental frequency at 2.4 GHz, total output power of 14.92 dBm, phase noise -130.7 dBc/Hz at 1 MHz offset frequency, figure of merit (FOM) -175.64 dBc/Hz, reduction in 2nd and 3rd harmonics to below -45 dBm and DC-to-RF efficiency of 51.73%.
A novel multi-mode resonator-fed filtering patch antenna with improved selectivity and bandwidth is proposed in this paper. Unlike well-known cascaded-resonator structure, the proposed filtering antenna shows five poles in the reflection coefficient response utilizing only one resonator. The gap-coupled radiating part introduces two gain zeros along each side of the gain response. Meanwhile, the dual-mode resonator feeding structure of the antenna will also produce another two gain zeros. All these four gain zeros highly improve the selectivity of the filtering antenna without increasing the number of coupling resonators. In addition, the bandwidth of the antenna is also considerably extended using this feeding structure. For validation, a prototype is designed, fabricated, and measured. The measured results agree well with the simulated ones.
This letter proposes a compact single-layer balanced bandpass filter (BPF), which is realized by a new arrangement of eighth-mode substrate integrated waveguide (EMSIW) cavities. Under differential-mode (DM) operation, the half bisection topology of the proposed EMSIW filter can be equivalent to a quadruplet scheme based on four coupled EMSIW cavities. The negative cross coupling can be easily realized by the nature of the fringe electric fields of opened ends of EMSIW cavities. For the demonstration, a balanced EMSIW filter with the operating frequency at 2.4 GHz is designed, fabricated, and measured.
In this paper, a simple approach for enhancing the gain of a planar dipole antenna using the concept of grounded metamaterial (MTM) has been proposed. In this regard, a magnetic metamaterial with Mu-very large (MVL) property has been utilised to increase the gain of the electric dipole source. A fully planar structure has been configured due to the placement of the metamaterial just over the ground plane. A significant amount of gain improvement (about 3.7 dB) of the dipole antenna can be attained using the metamaterial. In addition, a fair increase of fractional bandwidth by 2.2% has been obtained due to the loading of the metamaterial. A comparative study with respect to recently reported literature for the gain enhancement of planar dipole has also been discussed. The proposed antenna is a worthy candidate for wireless communication owing to the high gain, low profile, and wide bandwidth characteristics.
As one of the important means in discriminating every mode in a high power microwave (HPM) multimode system, utilizing a mode-selective directional coupler to quantitatively analyze multi-modes and power measurement has been proposed. The first step of this method is to calibrate the coupling coefficients of each coupled mode in the HPM system. Moreover, the conventional calibrating method must make the corresponding single mode exciter or mode generator. In this manuscript, a different calibrating method is presented by measuring the output power from each output port of two back-to-back identical mode-selective couplers, including the backward wave power, then the coupling coefficients of each coupled mode can be calculated by combining and solving equations. In this way, it is not necessary to manufacture the single mode exciter or mode generator for each mode in the HPM system, and also to repeat iteration solution; therefore, this method is more precise, convenient, efficient, and has lower cost than the current other methods.
A CPW-fed compact multiband planar printed monopole antenna for WLAN/WiMAX/X-Band applications is presented in this paper. The structure size of antenna is 0.144λ0×0.176λ0×0.008λ0. The proposed antenna is composed of three monopole radiators, a microstrip feed line and the ground with chamfer. With these structures employed, the antenna can generate four different resonances to cover the desired bands while maintaining low profile. The antenna simulation results show four distinct bands from 2.24 to 2.85 GHz, from 3.29 to 4.12 GHz, from 5.13 to 6.24 GHz, and from 6.58 to 8.57 GHz, which cover the entire WLAN bands (2.4-2.484, 5.15-5.35, and 5.725-5.825 GHz), WiMAX bands (2.5-2.69, 3.4-3.69, and 5.25-5.85 GHz), and X-band satellite communication systems (7.25-7.75 and 7.9-8.4 GHz). For verification of simulation results, a prototype of quad-band antenna is designed, fabricated, and tested. The simulated and measured return losses, radiation patterns, and gains are presented. The proposed antenna possesses compact size, simple structure, high gain, and omnidirectional radiation pattern, which make it a suitable candidate used in small/portable WLAN/WiMAX/X-Band devices.
A band-pass frequency selective surface (FSS) structure using capacitance layers is proposed to improve the performance of angular stability. It consists of band-pass FSSs, supporting dielectrics, and capacitance layers out of band-pass FSS. The supporting dielectrics and capacitance layers work as a transmission line and capacitance impedance matcher. Through the impedance matcher, the bandwidth is stabilized, and insertion loss at passband is reduced from -0.76 dB to -0.39 dB for incident angles up to 60°. The equivalent circuit of the proposed structure is presented, and the Smith chart is given to explain the mechanism of the capacitance layers. Finally, a prototype is manufactured and measured. A relatively good agreement is obtained between simulations and measurements. Therefore, the proposed structure can be an effective solution to improve the angular stability performance of band-pass FSS design.
An improved Taguchi's method (ITM) is proposed in this paper. The dynamic reduced rate function linked with the contributions of each parameter is used to increase the convergence speed. An extra procedure is added in the ITM to determine whether the experiment results in orthogonal array meet the termination criterion which is neglected in the traditional Taguchi's method (TM). Three experiments, including the syntheses of linear arrays and the designs of an E-shaped antenna and an ultra-wide band monopole, are conducted to investigate the performance of the proposed method, and the results are compared with those of traditional TM and other meta-heuristic methods. The results show that the same or even better results are obtained by the improved TM with fast convergence speed.
A circularly polarized (CP) half-mode substrate integrated waveguide (HMSIW) cavity-backed antenna is developed by a novel design method in this paper. The single-fed antenna contains two coupled HMSIW cavities with orthogonal polarizations. Its design method evolves from filter synthesis procedure, which takes the advantage of equivalent circuit model to accelerate the optimization. The antenna radiates high-purity right handed CP waves with measured axial ratio (AR) of 0.33 dB at 3.55 GHz, while its gain and AR bandwidth are comparable to other CP SIW antennas. With the robust design method, the proposed antenna is competitive in practical applications.
Magnetoacoustic tomography with magnetic induction (MAT-MI) is a multiphysics imaging technique that combines electrical impedance imaging with ultrasound imaging. In order to study the influence of parameters on the source of MAT-MI , such as radius and permeability of magnetic nanoparticle clusters, the paper is divided into the following stages. Firstly, this paper analyzes the electromagnetic and acoustic properties of MAT-MI after adding magnetic nanoparticles. Secondly, to determine the suitable simulation conditions, a two-dimensional model is constructed. Thirdly, use the finite element method to solve physical processes of electromagnetic field and acoustic field under conditions of different magnetic nanoparticle clusters' radii and permeabilities, then obtain the magnetic flux density image. Consequently, make the qualitative and quantitative analysis according to the theory and simulation results. The results show that magnetic nanoparticle clusters interact with each other and distort the magnetic field to different degrees; its radius increases with the degree of flux density distortion around it, so does its permeability and magnetoacoustic signal intensity. The research results can play a guiding role in the parameter selection of magnetic nanoparticle clusters in practical applications to a certain extent.
This paper presents a new type of vertically stacked substrate integrated waveguide (SIW) filtering antenna. It is composed of an SIW bandpass filtering circuit and an antipodal linearly tapered slot antenna (ALTSA). The filtering circuit consists of two vertically stacked SIW cavity resonators which are coupled with each other by etching slot on the common metal layer. By introducing electric and magnetic mixed coupling structures, close-to-passband transmission zeros can be realized and flexibly adjustable. Due to the partially vertically stacked structure, the proposed filtering antenna also shows a compact physical size. For validation, two vertically stacked SIW filtering antennas operating at 30 GHz with transmission zero at the upper or lower side of the passband are designed, fabricated, and measured. Good agreement is observed between the measured and simulated results.
In this paper, a compact triangular defected ground plane monopole antenna with 5G, WLAN, and a downlink/uplink of X-band notched characteristic for UWB applications is presented. The initial design consists of a CPW rectangle-shaped patch with a triangular, slotted ground plane to obtain ultra-wideband feature. The 3.3-3.7 GHz for the 5G band is eliminated by inserting dual symmetrical T-shaped slots at the upper edge of the ground plane. Further, a metamaterial as dual symmetrical single split ring resonator slits is etched at the bottom edge of the ground plane to suppress electromagnetic interference at IEEE upper WLAN band from 5.72 to 5.84 GHz. To restrict the interferences with the existing downlik and uplink for X-band signals from 7.1 to 8.39 GHz, we load a single I-slot to the radiator patch. The small size of the presented triple band eliminated antenna makes it a candidate suitable for recent communication systems.
Cables and electronic devices typically employ electromagnetic shields to prevent coupling from external radiation. The imperfect nature of these shields allows external electric and magnetic fields to induce unwanted currents and voltages on the inner conductor by penetrating into the interior regions of the cable. In this paper, we verify a circuit model tool using a previously proposed analytic model , by evaluating induced currents and voltages on the inner conductor of the shielded cable. Comparisons with experiments are also provided, aimed to validate the proposed circuit model. We foresee that this circuit model will enable coupling between electromagnetic and circuit simulations.
The research and development of microwave-tunable equipment has promoted the advancement of electronic countermeasures and electronic surveillance in the field of military communications. The research of fully tunable filters is a hotspot in the field of tunable filter research. Parameters such as center frequency (CF), absolute bandwidth (ABW), and transmission zero (TZ) are important indicators of fully tunable filters. In this paper, a high-performance fully tunable substrate integrated waveguide filter is designed and fabricated to achieve constant ABW (100 MHz) and TZ (1.59 GHz) with CF tunable, and the adjustable range is 1.1-1.3 GHz. Meanwhile, the constant CF (1.15 GHz) is achieved with the ABW tunable, and the adjustable range is 70-120 MHz. Also the constant ABW (100 MHz) and CF (1.14 GHz) are achieved with the TZ tunable, and the adjustable range is 1.59-1.89 GHz. The measured results show that the insertion loss of the tunable filter is lower than 2.04 dB, and the return loss is greater than 20 dB.
A new miniaturized microstrip lowpass filter with ultra-wide stopband performance using trapezoid patch resonators is investigated. To achieve compact design and ultra-wide band rejection, trapezoid patch resonators are employed in the filter. To further reduce the circuit size of the filter, a meander transmission line is also introduced in the design. A demonstration filter with 3 dB cutoff frequency at 0.50 GHz has been designed, fabricated, and measured. Results indicate that the proposed filter is able to suppress the 26th harmonic response referred to a suppression degree of 15 dB. Furthermore, the proposed filter exhibits a small size of 0.122λg×0.109λg, where λg is the guided wavelength at 0.50 GHz.
An algorithm named MUSIC-like algorithm was previously proposed as an alternative method to the MUltiple SIgnal Classification (MUSIC) algorithm for direction-of-arrival (DOA) estimation. Without requiring explicit model order estimation, it was shown to have robust performance particularly in low signal-to-noise ratio (SNR) scenarios. In this letter, the working principle of a relaxation parameter β, a parameter which was introduced into the formulation of the MUSIC-like algorithm, is provided based on geometrical interpretation. To illustrate its robustness, the algorithm will be examined under symmetric α-stable distributed noise environment. An adaptive framework is then developed and proposed in this letter to further optimize the algorithm. The proposed adaptive framework is compared with the original MUSIC-like, MUSIC, FLOM-MUSIC, and SSCM-MUSIC algorithms. A notable improvement in terms of targets resolvability of the proposed method is observed under different impulse noise scenarios as well as different SNR levels.
In a MIMO system, scattering is always an important problem since it is closely related to the channel capacity of system. In most of previous works, scattering was usually neglected so as to simplify the process of analysis. Therefore, it is really necessary to investigate and understand the scattering effect on capacity. To this end, scattering is taken into consideration in terms of channel capacity in this paper. From the antenna point of view, antenna element layout can be viewed as an optimization problem. To resolve this problem, a binary whale optimization algorithm (BWOA) is proposed. We investigate the effect of scattering environment on the capacity of a MIMO system and make comparison with an existing method in performance. The simulated results demonstrate that the nonuniform sampling method is able to efficiently improve the capacity of system even for poor scattering environment.
In this paper, a novel miniaturized microstrip branch-line coupler (BLC) with good harmonic suppression using radial stub loaded resonators is proposed. The novel structure has two significant advantages, which not only effectively reduces the occupied area to 10.3% of the conventional BLC at 0.5 GHz, but also has high 14th harmonic suppression performance. The measured results indicate that a bandwidth of more than 121 MHz has been achieved while the phase difference between S21 and S31 is within 90° ± 1.5°. The measured bandwidth of |S21| and |S31| within 3 ± 0.4 dB are 146 MHz and 151 MHz, respectively. Furthermore, the measured insertion loss is comparable to that of a conventional BLC. To validate the design concept, a new miniaturized planar BLC with good harmonic suppression using radial stub loaded resonators is designed and fabricated. Simulated and experimental results are achieved with good agreement.
In this paper, a half-mode substrate integrated waveguide (HMSIW) semi-circular cavity backed antenna, using two higher order modes (TM210 and TM020), has been proposed for dual-band operation. A semicircular slot is engraved on the top of the HMSIW structure forming a cavity that is fed by co-axial feeding to get impedance matching with the line. The theoretical operation of TM210 and TM020 modes is explained using the simulation tool. The antenna parameters such as reflection coefficient, gain, and radiation patterns have been measured for the fabricated antenna. The antenna radiates in two bands, in which the first band center frequency is 8.5 GHz, and the second band center frequency is 10.6 GHz. Peak gains at boresight direction are around 7.5 dBi and 6 dBi, respectively.
Characterizing the random errors at the elements of a phased array antenna leads to equations that estimate the associated performance degradation. The increase in sidelobe level and decrease in gain due to random errors is well established. This paper derives an expression that predicts the axial ratio degradation due to random errors in the circularly polarized elements of an array. In the case of small errors in an array of crossed dipoles, we found a simple expression for the axial ratio of the array under random errors at broadside.