A novel single-negative magnetic (SNG) metamaterial (MTM) insulator is designed to reduce mutual coupling between high-profile monopole antennas. As a kind of metamaterials, the proposed SNG MTM-resonator utilized concentric rings embedded complementary metal structures. Then, an insulator is achieved with a highly compact structure. The band-gap of the insulator is attributed to the negative permeability of the magnetic resonance. A well-engineered MTM-resonator is then embedded in between a high-profile monopole antenna array for coupling reduction. The antenna array is designed, fabricated, and measured. Both numerical and experimental results indicate a mutual coupling reduction of more than 17 dB. The 20 dB isolation bandwidth about 16% is obtained. The proposed prescription with electrically small dimensions and high decoupling efficiency opens an avenue to new types of high-profile antennas with super performances.
A novel hybrid antenna capable of both spectrum sensing and then accordingly reconfiguring its operating characteristics is proposed here. The proposed antenna is versatile in nature as it can reconfigure its resonant frequency, polarization state, bandwidth and radiation pattern. The physical structure of antenna is also versatile in nature as different printed parts are used several times in different operating modes using PIN diodes. The proposed versatile antenna senses spectrum over a wide frequency range from 3 GHz-12 GHz by using a separate UWB antenna. After sensing, the antenna can reconfigure its frequency in five different bands using three matching stubs. The proposed antenna can reconfigure its polarization state over two frequency bands by controlling the switchable slot. The antenna can also reconfigure its pattern by shorting the parasitic arc using PIN diodes. The prototype is fabricated, and the functioning is verified through measurement.
In this paper, the design of a broadband, high-efficiency, and high-linearity Class-J GaN HEMT RF power amplifier (PA) over 1.6-2.6 GHz is explained. The source impedance is conjugate-matched to the input impedance of the device resulted from small signal simulation to make a high-gain power amplifier. The load impedance related to the maximum power added efficiency (PAE) and maximum output power is obtained by pulling the only fundamental and second harmonic components over frequency bandwidth. Thus, not only a high-efficiency PA but also a high-linearity PA is formed. The input and output matching networks are implemented by microstrip transmission lines. The theoretical PA designed is optimized using computer-aided simulations. The fabricated PA provides output power in the range of 38-39.9 dBm with 60%-73% PAE and 15-16.3 dB power gain across the band. The worst measured ACLR1 as the PA is fed by the CDMA signal with 1.2288 MHz bandwidth is at a level of -38.6 dBc. A close agreement between the measured and simulation results is observed due to the use of high-order harmonic balance simulator and high-accuracy implementation procedure.
A broadband rectangular waveguide calorimeter for power sensor calibration in the millimeter-wave region is presented in this study. The calorimeter has a dual-load structure, an operational frequency range of 26.5 GHz to 40 GHz, and high substitution efficiency and sensitivity. Its effective efficiency uncertainty is 0.74%~1.1%.
In this paper, an antenna with reconfigurable radiation pattern in H-plane at 2.45 GHz for high power applications is presented. It is based on a 3-slot array in E-plane covered partially with two mobile metallic flaps in order to reduce their length, and in consequence, they ensure the mechanical reconfiguration pattern in H-plane. The power distribution of the array is ensured with a power splitter in E-plane, and the uniform and in phase field distribution on the slots is ensured with a sectorial horn placed before the splitter. To reduce cost and weight, the power splitter is realized with metalized wood.
An approach of miniaturizing planar Yagi array using metamaterial is presented in this paper. In this methodology, metamaterial structures are incorporated in the antenna in place of directors. An investigation in reflection and radiation characteristics of the antennas is done, and the findings are presented. The metamaterial loaded antenna shows improved directivity and efficiency of 16.3% and 2.95% with respect to the microstrip Yagi antenna while achieving a noticeable size miniaturization of 33.3%. Also, a better matching, compared to Yagi antenna, is observed in this proposed design. The fabrication and measurement of ones.
This paper presents a method of designing a bandpass filter using hybrid polynomials. Two different approaches are discussed in this paper. The first method uses class hybridization of a lowpass Chebyshev and highpass maximally flat to achieve the hybrid filtering function (HFF). The second method employs both Chebyshev polynomials of the first and second kinds to form a modified Chebyshev polynomial. Both methods achieve a narrowband dual-band lowpass prototype (DBLPP) without much deviation from classical methods of synthesis. The designs can be adapted into a modified interdigital prototype which will be shown in this paper. The results and measurements reflect a good adherence to the theoretical calculations.
A compact dual-polarization, ultra-wideband quad-ridged horn antenna has been proposed for breast imaging. CST Microwave Studio Simulation has been used to design the horn antenna. The antenna size was reduced, and impedance matching was achieved by a modest change in the dielectric constant of the matching liquid and by the introduction of four semi-elliptical structure at the flared ridges. To test the polarization isolation, many field probes were distributed at different positions in front of the antenna. The probes have been set to measure both vertical and horizontal electric field components at each location. Results show that adding elliptical parts can provide impedance matching over the whole frequency band of the antenna. Measurements show high isolation between the transmitted vertical and horizontal electric fields. Almost 40 dB polarization isolation exists at boresight of the antenna over the entire frequency band. This characteristic is central to polarimetric radar work. Effective gain and ports isolation were obtained.
In this study, a trapezoidal-rule integrator and inverting a differentiator are employed to form the transfer function of an approaching integrator in the Z domain. The integrator was implemented to verify the feasibility of the technique, and the integrator exhibited an operating frequency of 1.45 to 6 GHz. Adding microwave integrators to a receiver's radio frequency (RF) circuits in a communication link improves the signal-to-noise ratio (SNR). As a result, an experimental environment was constructed in a wireless local area network (WLAN) band (2400 to 2483.5 MHz). In addition, the RF transmitter emitted the main signal at 2.45 GHz, which included the high-frequency interfering signals at 3.5, 4.5, and 5.5 GHz. The integrators and low-pass filters were implemented to perform signal analysis of the RF signals. To compare the interference suppression of the integrators with the interference suppression of the original and low-pass filters, the receiving power of the main signal and the interfering signals from the different frequencies in the end of the receiver were analyzed. The experimental results indicated that inserting integrators into RF circuits improved the SNR of the communication link by up to 10 dB.
In this paper, an L-band wideband quad-ridged waveguide orthomode transducer (OMT) for the Five hundred meter Aperture Spherical radio Telescope (FAST) is presented with a simple design principle. By designing two critical parts of the OMT separately and introducing matching rings into two orthogonal probes, an improved wideband performance has been realized successfully. The OMT is designed to operate across the 0.95 GHz-1.9 GHz band, and the simulation shows a return loss better than -20 dB for both polarizations, cross-polarized isolation levels over 45 dB and insertion loss lower than 0.15 dB over the entire bandwidth. The measured results are in good agreement with the simulations.
A wideband orthogonally polarized resonant cavity antenna (RCA) with double-layer Jerusalem Cross type partially reflective surface (PRS) as superstrate is presented in this paper. The PRS is analyzed using equivalent circuit modelling and full wave simulations. Two-port dual-polarized aperture coupled microstrip patch has been used as primary feed antenna. Measured results show that the antenna structure exhibits 10 dB return loss bandwidth of 14.7% at 10 GHz (9.4-10.9 GHz), and the isolation between the feeding ports is better than 18 dB over the bandwidth. The cross-polarization levels in both E and H planes are better than 15 dB. The peak directivity of the antenna is 13 dBi in the entire band. The antenna is suitable for marine and weather Radar applications.
A compact microstrip resonator based on the interdigital structure is proposed. The resonator has several times higher unloaded quality factor compared to similar resonators presented previously and can even reach the Q-factor of a regular λ/4 resonator. The size of the resonator can be significantly reduced with a substantial increase in quality factor by incrementing the number of pins in the interdigital structure. In addition, for each gap between the pins exist an optimal number of pins that correspond to the maximum Q-factor. An extension of the upper stopband for a bandpass filter designed using the resonator can be achieved by the interconnection of the pins in each of the comb structures. The simulation results were proven by fabricated resonators and 4-pole bandpass filter. For the central frequency of 2000 MHz and 16.2% fractional bandwidth, the lateral size of the filter is only 11.5 mm×3.8 mm for alumina substrate (eps=9.8). The filter has an upper stopband up to 5.8f0 at the level -40 dB.
A low-profile wideband circularly polarized (CP) microstrip antenna with conical radiation pattern is designed in this paper. Based on the center-fed circular microstrip patch structure, the proposed antenna symmetrically employs 5 shorting vias connecting the patch and the ground plane to provide the θ-polarization and 11 slant sector branches at the edge of circular patch to generate the φ-polarization. With the phase difference of 90° between the two orthogonal polarizations, the design radiates right-handed circularly polarized (RHCP) waves. The proposed antenna works at three resonant modes. To realize broad operating bandwidth, the slant sector branches should be carefully adjusted to make the second resonant mode couple the first mode (TM01 mode) and third mode (TM02 mode) together. The measured results show that the proposed antenna has a low profile of 0.025λ, impedance bandwidth of 35.4% (3.74-5.35 GHz), and axial ratio (AR) bandwidth of 38% (3.7-5.45 GHz). To further verify the characteristics of the proposed antenna, the studies on several important parameters are carried out by HFSS simulation, and a simple design guideline is provided.
A new technique is developed to couple the advantages of both the microstrip patch antenna and rectangular waveguide. An equilateral triangle is used as a radiating patch. This patch is fabricated on one face of a single-layer dielectric substrate with double-sided copper clad coated with tin, and on the other face an iris is fabricated and coupled to the waveguide. Antenna parameters such as return loss and bandwidth are studied for a circular patch. The results obtained are discussed in detail and explained. Matlab PDE toolbox is used to generate two-dimensional meshes. These meshes are converted into a three-dimensional form using subdomain numbers. RWG basis functions are used for MoM to calculate impedances. Reection coefcient and 2D current are obtained using the complex impedances.
A wideband circularly polarized (CP) cross-dipole antenna is proposed for wireless applications. In this design, four parasitic square patches are utilized around the radiation patch to enhance the Axial-ratio (AR) bandwidth. By employing the bowtie-shape dipoles, the proposed antenna can achieve a wide impedance bandwidth. Meanwhile, by integrating with a curved-delay line which provides a 90° phase difference, the proposed antenna can radiate a CP pattern. A prototype is calculated, fabricated, and measured. Good agreement between the simulated and measured results is achieved. The measured results show an impedance bandwidth for VSWR≤2 of 47.73% (1.93-3.14 GHz) and a 3-dB AR bandwidth of 42.8% (2.00-3.09 GHz).
In order to improve the focusing and imaging effects of conventional spiral zone plates (SZPs), we design a new type of spiral photon sieve (SPSs) apodized by a robust Bessel-like window. The design principle and numerical simulation results show that the Bessel-like window has a better modulation effect on the main lobe compression and side suppression of the point spread function (PSF) than other traditional window. Taking advantage of the robustness of Bessel-like windows, the proposed SPS can achieve a higher spatial resolution and lower side lobe noise than the conventional SPS and SZP. The practical effects have also been demonstrated by image experiments on the micropore. Our work may find some potential applications in laser alignment, optical trapping, optical communication and edge enhancement imaging fields.
In this paper, a novel W-band substrate integrated waveguide (SIW) power combiner/divider is analyzed theoretically and demonstrated experimentally/numerically, based on the antipodal fin-line SIW-rectangular waveguide (SIW-RW) transition and longitudinal slot coupling techniques. This antipodal fin-line SIW-RW transition can work at the frequency band of 86.4 GHz-106.1 GHz with return loss larger than 15 dB and inserting loss less than 2 dB. By combining the antipodal fin-line SIW-RW into the four-way longitudinal-slot SIW coupling structure, a novel back-to-back power dividing/combining system is achieved, which can operate at the frequency band of 92.8 GHz-93.8 GHz with return loss more than 10 dB and insertion loss less than 3.9 dB. Such a design can be used in future for spatial power amplifier applications.
A novel concept of using slotted ground structure and a single circular split ring resonator (SRR) to achieve multiband operation from a miniaturized UWB antenna is presented in this paper. Initially a miniaturized volkswagen logo ultawideband (UWB) antenna having -10 dB impedance bandwidth of about 124% (2.9-12.4 GHz) in simulation and 116.7% (3.1-11.8 GHz) under measurement is designed. This miniaturization leads to about 10% increment in -10 dB reflection coefficient bandwidth and about 66.71% reduction in volume of the proposed UWB antenna as compared to the conventional circular antenna. In order to reconfigure the proposed UWB antenna to operate it at 1.5 (GPS), 3.5 (WiMAX), 5.2 and 5.8 GHz (WLAN) frequency bands, slotted ground structure with metamaterial is used. The proposed metamaterial is a circular split ring resonator (SRR) consisting of single circular ring and is placed on the slotted ground structure of the proposed antenna to achieve 1.5 GHz band. The proposed configuration has a volume of 0.290λ0×0.290λ0×0.015λ0 (30×30×1.6 mm3) at lower resonating band of 2.9 GHz and is fabricated on a widely available FR4 substrate with a loss tangent of 0.02 and dielectric constant of 4.4. Simulated and experimental results shows that the proposed design yields S11<-10 dB at the targeted frequencies. Good impedance matching, stable radiation characteristics with cross-polarization level less than -15 dB (both in E and H planes), VSWR<2, average gain of 3.09 dBi and radiation efficiency of more than 85% are observed at the designed band when the antenna is fabricated and tested.
A compact microstrip lowpass filter with ultra-wide stopband characteristics and high suppression level is presented. To achieve compact size and wide stopband suppression along with improved impedance matching, symmetrically loaded resonant patches, open stubs and stair shaped high impedance stub is introduced in the filter. The measurement results show good agreement with the simulations. The 3 dB cutoff frequency of the filter is 2.44 GHz. The stopband with attenuation level better than 22 dB is extended from 2.84 GHz to 16 GHz, hence an ultra wide stopband with 6th harmonic suppression is achieved. The proposed filter has low insertion loss and high return loss in the passband, together with compact size of 0.257λgx0.148λg, where λg is the guided wavelength at cutoff frequency. The relative stop bandwidth of the proposed design is identified to be 139.5%.
A novel compact unidirectional UWB antenna is presented in this paper. First a novel planar omnidirectional UWB antenna with CPW-feed is designed. The antenna is composed of a half-elliptical disc with a small ground plane. A slot is inserted on the patch as a novel technique to improve the gain bandwidth of the antenna at higher frequencies is presented. The omnidirectional antenna shows UWB matching and gain bandwidth of 2 GHz to 6.5 GHz. Furthermore, to make the radiation pattern of the omnidirectional antenna unidirectional, a rectangular shape metallic reflector without bottom wall is used on the backside of the antenna. The unidirectional antenna with a total dimension of 0.52λm x 0.33λm x 0.18λm (λm wavelength of the minimum operating frequency) has a matching bandwidth of 1.5 GHz to 7.7 GHz with a gain of 5 dBi to 10.2 dBi over 1.7 GHz to 6.5 GHz, and flat group delays of less than 1 nsec. To validate the proposed design, the antenna is fabricated, and measured results are compared with simulations.