High output power multiplier is necessary for local oscillator (LO) source of millimeter-wave and terahertz applications. However, single multiplier chip power-handling capability is limited by understandably low efficiency level and other technical constraints. Conventional in-phase power-combined structures are sensitive to the fabrication and assembly errors. In order to circumvent these limits, we propose a power-combined multiplier architecture at 60 GHz based on fundamental frequency vector modulation at 30 GHz. The fundamental vector modulator adjustment can compensate the phase deviation at the two doubler output ports despite fabrication and assembly tolerances. We can increase the output power by approximately 3 dB compared with single multiplier without sacrificing the bandwidth.
A novel tri-band pattern reconfigurable planar antenna is proposed. Tri-band is achieved by inserting a bandstop filter at the feed line of a wideband monopole antenna with complementary split ring resonator (CSRR) on a circular patch. Two parasitic arc-shaped stubs are in the back side of the radiator that works as a reflector. The antenna radiation pattern is switched from omnidirectional to one of two different directional modes by activating one of the stubs. Three different radiation modes are controlled by four ideal switches. Radiation pattern reconfigurability makes it suitable for the use of flexible cognitive radio front-end system. The proposed antenna is suitable for WLAN 2.4/5.2/5.8 GHz and WiMAX 3.5/5.5 GHz applications. Good agreement between simulated and measured results validates its possible application.
This paper presents a microstrip wideband antenna and its utilization in integration of multiple wireless communication systems. A simple fork-like strip antenna, fed by a coplanar-waveguide (CPW) transmission line, is designed to excite a right-hand circularly polarized wave at 1.57 GHz. A rectangular patch is added at the end of one prong to enhance the circular polarization performance. By modifying the geometry of the ground plane, a left-hand circularly polarized wave is excited at 2.33 GHz, and the wideband frequency response is derived. To reduce the lower resonant frequency, a stub is added at the left side of the ground plane. The measured impedance bandwidth of reflection coefficients (S11) < -10 dB ranges from 1.49 to 2.92 GHz, which satisfies the system bandwidths of most of commercial wireless communication systems. The 3-dB axial-ratio bandwidths are approximately 40 MHz at the lower band (1.57 GHz) and 290 MHz at the upper band (2.33 GHz).
A novel balanced antipodal Vivaldi antenna (BAVA) with high gain and good directivity is proposed in this paper. The outer edges of the flare are modified by a binomial curve to broaden the impedance bandwidth. A metal director is adopted to improve the antenna gain and directivity. The measured results show that the proposed BAVA achieves a bandwidth from 2 to more than 40 GHz with peak gain >0 dBi and >10 dBi over the 8-40 GHz range. The squinting beam of E-plane is less than 5° from 4 to 40 GHz and less than 3° from 22 to 40 GHz.
This paper presents the design flow of a compact GaAs MMIC for Extremely High Frequency (EHF) satellite communications. The proposed circuit enables sub-harmonic mixing capability and integrates a LO buffering section, thus allowing for low frequency and low power reference signal interface. Circuit design is described in detail providing a comprehensive view of the followed theoretical approach, starting from mixer core definition until the complete synthesis of LO/RF/IF interfaces. In particular, the design flow of an innovative three-conductor Marchand balun is deeply analysed. Fabricated MMIC operates in the 43.5-50 GHz band and results in a compact layout (2.4x2.4 mm2) featuring a port-to-port isolation better than 25 dB with a typical conversion loss of 12 dB.
A circular monopole antenna for ultra wideband (UWB) applications with triple band notches is proposed. The proposed antenna rejects worldwide interoperability for microwave access WiMAX band (3.3 GHz-3.8 GHz), wireless local area network WLAN band (5.15 GHz-5.825 GHz) and X-Band downlink satellite communication band (7.1 GHz-7.9 GHz). The antenna utilises mushroom-type and uniplanar Electromagnetic Band Gap (EBG) structures to achieve band-notched designs. The advantages of band-notched designs using EBG structures such as notch-frequency tuning, triple-notch antenna designs and stable radiation pattern are shown. The effect of variation of EBG structure parameters on which notched frequency depends is also investigated. Fabricated and measured results are in good agreement with simulated ones.
This paper proposes a planar monopole antenna design for achieving gain enhancement. The radiation pattern is achieved straightforwardly by employing a detached glass slab and placing a reflected metal slab after the glass slab onto the antenna structure. Geometrical parameters were examined to optimize the performance of the proposed antenna. Such a configuration causes constructive interference between the incident and reflected fields. The radiation patterns can be adjusted the thickness of the glass slab and dielectric constants. The radiated fields are redistributed because of the inclusion of the glass slab, which has a permittivity of εr = 7.75 and a thickness of h = 1 mm. Consequently, the planar monopole gain achieved using the glass slab and reflected metal slab is increased to approximately 5 dBi, whereas the antenna resonant frequency remains almost unchanged at nearly 14% in impedance bandwidth. The results obtained for the directional pattern, return loss, gain, and radiation efficiency of the proposed antenna were analyzed. The antenna volume of the radiation area and ground plane was 3 × 32 × 52 mm3. Detailed simulations and experiments were conducted to optimize the gain enhancement operations, and the measured results agreed with the simulated ones.
A double printed rotated quadrilateral dipole UWB antenna for wireless communication is presented. The rotation of quadrilateral and modification of integrated balun structure is employed to enhance bandwidth and impedance matching. The proposed antenna shows impedance bandwidth of 3.8-18.1 GHz which covers the entire C, X and Ku bands. The Radiation patterns of the designed antenna structure are relatively stable and omnidirectional over the entire obtained bandwidth with an average gain of 3.6 dB. A good agreement is found between the simulated and experimental results. The proposed antenna has a simple design, comparatively compact size and more bandwidth than previous reported double rhombus antenna.
The purpose of this paper is to theoretically investigate the properties of electromagnetic wave propagating in both one-dimensional periodic and quasiperiodic photonic crystals consisting of high-temperature yttrium barium copper oxide and strontium titanate dielectric nano-scale materials in the ultraviolet wavelength region. By using the transfer matrix method, angle-, polarization- and thickness-dependences of created PBGs are explored individually for periodic and quasiperiodic structures, and some interesting features are presented in the results section. Such supposed structures can be acts as very compact polarization sensitive splitters and defect-free multichannel narrowband tunable filters.
A 2×2 circularly polarized (CP) MIMO antenna is proposed to resonate at 5.8 GHz IEEE 802.11 WLAN band for non-line of sight (NLOS) communication. The proposed design achieves circular polarization with two optimized 90˚ apart rectangular slots etched at the center of a truncated rectangular patch. The proposed MIMO covers 5.49-6.024 GHz frequency band. The achieved isolation between two ports is more than 33 dB. The gain at the 5.8 GHz resonant frequency is 5.34 dBi. The diversity performance in terms of gain, ECC, and MEG has been reported.
A compact coupled-fed monopole handset antenna with multi-frequency band operation is proposed in this paper. It occupies a no-ground space of only 26×14mm2, and two wideband operations can be achieved by the coupled-fed two opposite-direction spiral branches. The low frequency bands of LTE700 operation are achieved by two spiral branches' 0.25-wavelength monopole modes, which generate a dual-resonance mode at 740 and 780 MHz. At around high frequency ranges, a 0.25-wavelength monopole mode of a T-shaped monopole is generated at 1.75 GHz, and combined with two 0.75-wavelength high-order monopole modes of the left and right side spiral branches to cover the DCS1800/PCS1900/UMTS2100/LTE2300/2500 bands. In addition, the proposed antenna is easily printed on the dielectric surface of a low cost FR4 substrate, which makes it suitable for practical mobile applications. The proposed antenna is successfully simulated, fabricated, and measured to validate the design.
We report the modelling and characterization of microwave absorbing materials specially designed for 26-37 GHz frequency range (Ka-band). Composite materials based on carbon nanotubes/BaTiO3/Fe3O4 in a phosphate ceramic matrix were produced, and their electromagnetic response was investigated. Both theoretical and experimental results demonstrate that this material can absorb up to 100% of the power of an incident plane wave at a normal incidence angle. The physics underlying such absorption level is discussed in terms of refractive index of the material.
Transmission zero behavior of two coupled sections - interdigital and combline - is investigated. It is shown that the shifting of transmission zero of any coupled-section of a particular length depends on the width of various parts and the orientation of coupled-section. Mathematical formulation has been performed to show the effect of stepped discontinuity on the transmission zero. Further, this transmission zero allocation property is used in suppression of harmonics. The idea is implemented in two types of resonators - first in parallel-coupled resonators and second in open-loop resonators. Two parallel coupled resonator based bandpass filters (BPFs) with second harmonic suppression - one of second-order and the other of fourth-order - using different coupled-sections have been fabricated, and suppression up to -30 dB and -54 dB respectively has been achieved. A fourth-order open-loop resonators based BPF with suppression of undesired passbands up to 6.3fo has been fabricated. Further, the above property is also used to design a dual-band BPF with wide stopband without increasing the size of the filter.
Wireless power transfer system to capsule endoscope at sub-gigahertz (GHz) frequency is presented. Compact self-resonant antennas are designed to realize the transcutaneous power transfer. Experiment shows that at a distance of 5 cm, the designed system operating at 433.9 MHz can realize 1.21% power transfer efficiency (PTE) through duck intestine and porcine multilayered tissues, that is, 47.55 mW power delivered to load (PDL) at the specific absorption rate (SAR) occupational exposure limitation.
This paper proposes a fully integrated broadband power amplifier for LTE-A application using GaAs HBT process. To improve the linearity and broadband performance, RC feedback structures and dynamic bias circuits are employed and designed through optimization. With careful design of the broadband matching networks in the proposed 3-stage power amplifier topology, a power gain above 21.6 dB is achieved from 1.8 GHz to 2.8 GHz. Driven by an 80 MHz wideband LTE-A signal with PAPR of 7.5 dB, the designed RF power amplifier achieves an average output power about 22 dBm at ACLR=-30 dBc over the entire 1 GHz frequency band. Considering the broad bandwidth of the driven signal and wide frequency coverage bandwidth, the performance merits of the proposed design compare favorably with the state-of-the-art.
Previously reported staggered double vane (SDV) slow wave structure (SWS) traveling wave tube (TWT) gave electron efficiency as low as 3.4% at 220 GHz, which needs to be improved. One easy method to improve the electron efficiency and the output power is to reuse the spent electron beam energy, by resynchronizing electron velocity to the phase velocity of the terahertz (THz) signal at the second section of the TWT. In this article, we have modified the pitch of the SWS to realize the tapered phase velocity, which is for the first time to our knowledge applied to the SDV SWS at 220 GHz. By varying the geometry configuration, an optimized structure of tapered pitch SWS has been successfully developed. The results reported in this paper show a significant improvement of the output power, gain and electron efficiency. At 220 GHz, the output power has increased by about 65% with respect to the previous reported value reaching 111 W, and the electron efficiency has improved from 3.4% to 5.6%. In order to simplify the microfabrication process, an input/output coupler with E-plane bending has been designed, which can be fabricated by using only one mask UV-LIGA process.
This paper presents an ultra-compact filtering integrated antenna for GPS (1.57 GHz) and LTE (2.65 GHz) applications. The antenna comprises integration between dual composite right/left-handed antenna and band stop filter in one platform. The whole integrated antenna size is only 30×28.5 mm2. Compared to conventional antenna with the same dimensions, the proposed antenna is only 6.5% at GPS band and 16.5% at LTE band. The deign procedures of individual antennas, bandstop filter and the filtering integrated antennas are explained in details. The full wave simulations supporting the design procedures and experimental measurements for all introduced components are introduced with good agreement. Finally, as a consequence of the proposed antenna ultra small size and its filtering capability, the antenna is a good candidate for implanted antenna applications.
In this paper, a magnetically tunable metamaterial is proposed and studied. The metamaterial is based on the combination of ferrite sheets and dielectric rods. The tunable property is originated from the ferromagnetic resonance and electric response of dielectric rods. The retrieved electromagnetic parameters and transmission characteristic showed that by simultaneously inspiring the ferromagnetic resonance and electric resonance, composite metamaterial can possess double-negative band in the resonant state. Moreover, this band was tunable by adjusting applied magnetic fields. The simulations and experiments verified that the composite metamaterial clearly displayed a tunable feature. The proposed method is simple in designing tunable metamaterials.
Two single-layer X/Ku dual-band dual-polarization reflectarray antennas of different sizes with double parallel dipole elements are presented. Elements of the two bands are set to two orthogonal linear polarizations and placed in interlaced grid. The proposed reflectarrays operate in two frequency-bands within X-band centered at 10 GHz and Ku-band centered at 13.58 GHz. The smaller size reflectarray with elements arranged in a 13×13 grid for X-band and in a 12×12 grid for Ku-band is designed and simulated first. Based on the excellent dual-band performance of the small size reflectarray, then a larger size prototype has been designed, manufactured and measured. Measured results demonstrate the maximum gain of 28.54 dB with 50.93% radiation efficiency at 10 GHz and 31.06 dB with 51.34% radiation efficiency at 13.58 GHz, which show desirable dual-band dual-polarization radiation performance.
In earlier time, we proposed a flat LHM-based hyperthermia scheme for conformal hyperthermia of a large superficial tumor. It is demonstrated that in this scheme by de-ploying multiple microwave sources in a specific array to shape the heating zone and properly setting the source-to-lens distance or phases of sources to adjust the inclination of heating zone, a heating zone better fit to large superficial tumor can be generated. In this paper, we propose a new hyperthermia scheme based on a cylindrical LHM lens which would be more maneuverable for tumors located in tissues with curved surface. It is shown that the same way adopted in the flat LHM-based scheme can be used in this new scheme to acquire desired heating zone for better fitting to tumor region. And larger critical source intervals defined in this new applicator greatly relax the restriction to the size of practical antennas applied in this scheme.