A broadband rectifying circuit with high microwave-direct current (mw-dc) conversion efficiency is designed based on the voltage doubling circuit. The rectifying circuit consists of a broadband match network, a capacitance, a diode, a dc-pass filter formed by three fan-shaped stubs and a resistive load. The measured results show a maximum mw-dc conversion efficiency of 78.3% at 2.45 GHz centre frequency on a 900 Ω load. When the input power is 15 dBm, the bandwidth of efficiencies higher than 50% is about 57% (1.65 GHz-3.05 GHz). The simulated results agree with the measured ones. The rectifying circuit has the characteristics of simple structure and easy integration, which can be applied in the microwave power transmission systems.
A dual-band circularly-polarized microstrip antenna is proposed, and the antenna for GPS is designed. The radiation characteristics of the dual-band circular polarization are achieved by installing one pair of L-shaped slits at all edges of the square patch. The impedance matching in the dual band is tuned by an L-probe feed. The proposed antenna is effective and useful in the design for dual-band circularly-polarized operation.
This paper presents a broadband hexa-band dual-polarized loop antenna for mobile communications. Two orthogonal one-wavelength-perimeter modes of a rectangular loop are excited by two orthogonal feedings. One mode for vertical polarization is excited by a circular monopole, and the other mode for horizontal polarization is excited by a slot-coupled microstrip line. By optimizing the antenna structure and the orthogonal feedings, the orthogonal polarizations can be achieved in a wide bandwidth with high ports isolation. The overall size of the proposed antenna is only 58×53 mm2 (0.43λ0×0.39λ0, λ0 is the free-space wavelength at 2.2 GHz). A prototype of the proposed antenna is built and tested. The measured bandwidth with reflection coefficient less than -10 dB is 61.4% (1.65-3 GHz) for both orthogonal polarizations, covering the DCS, PCS, UMTS, WLAN, LTE 2300, and LTE 2500 operation. The measured ports isolation is better than 28 dB over the entire band. In addition, the radiation patterns, gains and diversity performance are also discussed.
In this letter, a compact branch-line coupler using a new type of uniplanar composite right/left-handed transmission line (CRLH-TL) is proposed. The transmission line is obtained by etching spiral structure and series meandered capacitive gaps at both ends on the host line. With the aid of lumped element equivalent circuit model and dispersion relations, the CRLH property of the line is studied. By using the proposed structures, the 90-degree phase shift 35.35 ohm and 50 ohm transmission lines are designed for a compact branch-line coupler operating at 1 GHz. It's occupied size is only 32.5% of that of the conventional one. Its uniplanar prototype makes it very useful for wireless communication systems requiring high encapsulation quality.
A novel miniaturized combined-element frequency selective surface (CEFSS) with simple design process is proposed for multiband applications. In this article, complementary meandered structures and complementary grid structures are combined to realize controllable tri-band characteristics, which allow the designed FSS to transmit different frequency signals at 3.3, 4.5 and 5.4 GHz while reflecting signals at 4.0 and 4.9 GHz. The miniaturized combined-element FSS in this paper has the advantage of smaller size comparing to traditional tri-band FSSs due to the use of meandered structures, which contributes to its independence of both angle and polarization. The associated equivalent circuit is provided to analyze its transmission characteristics. Furthermore, the performances of the proposed structure are evaluated by simulation and measurement, and they agree well.
A planar ultra-wideband (UWB) antenna with triple-notched bands based on square ring short stub loaded resonator (SRSSLR) is presented in this paper. By coupling a SRSSLR beside the microstrip feedline, band-rejected filtering properties around the C-band satellite communication band, 5.8 GHz WLAN band, and 6.8 GHz RFID band are generated. The notched frequencies can be adjusted according to specification by altering the SRSSLR. The results indicate that proposed planar antenna not only retains an ultra wide bandwidth, but also owns triple band-rejections capability. The UWB antenna demonstrates omnidirectional radiation patterns across nearly whole operating bandwidth that is suitable for UWB communications.
A novel coupled-defected ground structure (C-DGS) with inductors inserted between the adjacent defected ground structure (DGS) cells is presented in this paper. In comparison to conventional C-DGS structure, the proposed C-DGS exhibits a larger coupling-coefficient, resulting in a wider stop-band. Moreover, the stopband can be adjusted flexibly without modification since the coupling-coefficient varies with the change of the inductance of the inserted inductor. Based on this new C-DGS, a low-pass filter (LPF) using cascaded C-DGS is constructed. The proposed structure is experimentally verified through the demonstration of a low-pass filter design.
Novel compact ultra-wideband (UWB) rectangular stacked dielectric resonator antennas (DRAs) with band-notched characteristics are proposed. The DRAs are designed to cover the FCC band (3.1-10.6 GHz) and have very compact sizes, due to the shorting conductor. Printed dipoles that are placed on one side of the dielectric resonator will resonate and generate band notches within the ultra-wide operating band. Simulations and measurements confirm the validation of the design principle.
A loop antenna is designed and fabricated for ultra-high frequency (UHF) near-field radio frequency identification (RFID) readers. The artificial mu-negative transmission line (MNG-TL) structure has been applied to the antenna design, which will help the current distribution along the loop to keep in phase even with the perimeter of the loop more than two operating wavelengths. Thus a strong and uniform magnetic field distribution in the near field of the antenna can be generated. The simulated and measured results indicate that a relatively large impedance bandwidth from 762 MHz to 1048 MHz has been obtained. The overall size of the antenna is 216 mm×216 mm×0.4 mm, and a large interrogation zone with uniform and strong magnetic field distribution of up to 187.2 mm×187.2 mm has been achieved.
In this paper, a miniaturized planar rat-race coupler is proposed to achieve arbitrary power division ratio and harmonic suppression performance simultaneously. It consists of six enhanced T-shaped line sections. The T-shaped lines can be equivalent to arbitrary electrical length lines rather than the conventional λ/4 lines. The explicit design formulas are derived and the characteristic impedances variations with the freedom variable are discussed. Simulated and experimental results show the harmonic suppression to be over -35 dB, while maintaining the conventional performance at the fundamental frequency. The circuit area of the prototype is only 30.8% of the conventional coupler.
In this paper, an array aperture extension algorithm is developed for two-dimensional (2-D) direction-of-arrival (DOA) estimation with L-shaped array. We enlarge the dimension of the covariance matrix by using the rotational invariance in conjunction with the property that the signal covariance matrix is real diagonal matrix. Estimation of DOAs is performed by processing this larger dimensional matrix. The simulation results indicate that our method can improve the DOA estimation accuracy.
A new mathematical approach is proposed to highlight the nonlinear effect in a chiral medium, which is due to the magnetization vector under the influence of a strong electric field. In a chiral media, one can notice the coupling between the electric and magnetic quantities, which appears in the constitutive relations of the medium. According to our proposed approach, we illustrate the existence of the difference between a nonlinear achiral medium and a nonlinear chiral medium, where not only the polarization vector has a nonlinear form but also the magnetization vector. Thus, the nonlinear chiral medium is described by the new constitutive relations D=εgE+ε0μ0ξEHH and B=μH+ε0μ0ξHEgE. Therefore, a better fundamental understanding of the interaction between the electromagnetic waves and chiral media can be contemplated.
This letter proposes a novel ultra-wideband (UWB) bandpass filter with compact size and high-selectivity performance. The filter has been studied and implemented through multiple-mode resonator (MMR) using new coupling schemes such as capacitive source-load (S-L) coupling/inductive source-load (S-L) coupling. By properly adjusting the length and width of these stubs, its first four resonant modes can be allocated within the 3.1-10.6 GHz passband, whereas its fifth resonant mode is placed above 16.0 GHz. Two transmission zeros (an inherent transmission zero and an additional transmission zero) can be produced. Moreover, the position of the additional zero can be controlled by adjusting the direct coupling inductance/capacitance. Simulated and measured results are in good agreement indicating that the proposed BPF has a passband (3.0-11.0 GHz)/(2.92-10.6 GHz) and a wide stopband width with 23 dB/25 dB attenuation up to 27.0 GHz. The group delay of the filter is relatively constant and less than 0.65 ns/0.52 ns over the operating pass band.
Crosstalk is one of the bottlenecks for high-speed circuits to increase its rate and density. In order to make tradeoff between complexity and effect of the crosstalk cancellation circuit, a crosstalk cancellation method based on unitary transformation is proposed. In the method, two unitary matrixes are obtained by Singular Value Decomposition (SVD) of coupled transmission lines-channel transmission matrix (CTL-CTM), and then according to the form of the unitary matrixes, the crosstalk canceling circuits are built at both ends of the transmission line, which could transform the CTMes into unit ones and crosstalk would be cancelled out. Circuit simulation results show that at the signaling rate of 5 Gbit/s, jitter performance of eye diagram improves 85% and vertical performance improves 67.5%, which means the method achieves better crosstalk canceling effect with lower circuit cost.
A flexible VHF/UHF Vivaldi antenna is proposed. The antenna is realized on 600 × 600 mm2 silicone substrate with a thickness of 1.5 mm. The silicone substrate is used due to its low cost, its robustness and its flexibility. The antenna has a 6-dB impedance bandwidth from 150 MHz to 10 GHz. The measurements have shown that the bending slightly affect the impedance and the radiation patterns of the antenna. This last one is used for military applications to receive and find the source of VHF/UHF micro-wave emissions.
This paper presents a wideband circular polarization antenna for Global Navigation Satellite System (GNSS). By exciting four slots etched along each edge of a square ground with equal amplitude and 90° phase difference, good circular polarization performance is achieved. A novel radiation element, composed of back-side slot and front-side monopole, is proposed to realize a wideband radiation. Meanwhile, the feed network composed of Schiffman phase shifters and Wilkinson power dividers maintains this wideband performance. A backed cavity is used to suppress the backward radiation, therefore enhances the frontward gain. Measured results of the fabricated antenna show good agreement with the simulated ones. The main advantages of this antenna include its wide bandwidth, good circular polarization, high front to back ratio, low cost, and easy fabrication, which make it very attractive for GNSS terrestrial applications.
A new approach to design a dual-band matching network using a dual-band quarter-wave line is presented. The proposed matching network is capable of simultaneously matching frequency-dependent complex loads (FDCLs) having different values at two arbitrary frequencies to a real source impedance, Z0. A very simple step-wise design procedure is discussed for the transformer along with closed-form design equations which are very simple in nature. For experimental verification, two PCB prototypes have been fabricated using FR-4 material, operating at 1 GHz and 2.42 GHz. The measurements results matches well with that obtained from simulation, exhibiting good performance.
In this letter, a novel frequency-reconfigurable monopole antenna with several switchable states including an ultra wideband (UWB) state, filtering narrowband states, and a tunable filtering band state is presented. The antenna, which supports most applicable overlook narrowband frequencies between the 2-6 GHz, can be used in multiradio wireless systems. Moreover, the proposed antenna, which can avoid UWB interference and has narrowband functionality, has good potential for use in cognitive radio.
Microwave oven generates a harmful electromagnetic wave at 2.45 GHz of 1000 Watts. The generated microwave is confined within the cavity of the oven for efficient heating and secured operation. To prevent microwave leakage through the front glass door, a special construction of Faraday Cage is involved. In this paper, Faraday Cage is replaced with Transparent Frequency Selective Surface Front Door, which provides better visibility and avoids microwave energy to escape from the oven. Two works are proposed in this paper. The first one is band pass response which has been achieved for 10 GHz by printing array of Greek cross aperture (FSS) on the front glass door, and the second work is band stop response which has been achieved for 2.4 GHz frequency by printing the array of circular ring patch (FSS) on the front glass door. Design of two different FSS arrays and the simulation results were discussed.
In this paper, a multiband flexible antenna is presented. This antenna was realized on a flexible substrate in order to realize a deployable system for a distress beacon. We used the concept of open-sleeve antenna to change a quadrupole mode into a dipole mode. The main radiating element of the antenna is a dual-band folded U-shaped antenna. The operating frequencies of this antenna are studied depending on the length of the parasitic elements. In order to understand the matching and the radiation patterns in far field of both antennas (U-shaped and open-sleeve), their magnetic behaviors in near field are studied in simulation and in measurement. The simulated and measured radiation patterns are also presented to check the study in near field.