A planar bandpass filter is proposed in this paper. Its stopband is realized by using the concept of bandstop filter. A key merit of the filter configuration is that the position of the transmission zeros can be conveniently controlled whereas the bandwidth is fixed. The bandpass filter is realized using open circuited uniform impedance resonator and stepped impedance resonators. With five reflection zeros generated in the passband, ten controllable transmission zeros are introduced to sharpen the passband skirts. Skirt selectivity can be freely controlled by tuning the impedance ratio of the stepped impedance resonators. Without coupling gaps between resonators, the structure of the filter is simple and easy to fabricate. To illustrate the concept, a bandpass filter with ten transmission zeros is designed, fabricated and measured. Simulated and measured results are found to be in good agreement with each other, with insertion loss in the passbands less than 1 dB.
A new improved Least Trimmed Squares (LTS) based algorithm for Non-line-of sight (NLOS) error mitigation is proposed for indoor localisation systems. The conventional LTS algorithm has hard threshold to decide the final set of base stations (BSs) to be used in position calculations. When the number of Line of Sight (LOS) base stations is more than the number of NLOS BSs the conventional LTS algorithm does not include some of them in position estimation due to principle of LTS algorithm or under heavy NLOS environments it cannot separate least biased BSs to use. To improve the performance of the conventional LTS algorithm in dynamic environments we have proposed a method that selects BSs for position calculation based on ordered residuals without discarding half of the BSs. By choosing a set of BSs which have least residual errors among all combinations as a final set for position calculation, we were able to decrease the localisation error of the system in dynamic environments. We demonstrate the robustness of the new improved method based on computer simulations under realistic channel environments.
A new method for reducing the in-band radar cross-section (RCS) of a patch antenna within its operating frequency is presented. This method is based on the utilization of band-pass frequency selective surface (FSS) consisting of non-resonant constituting elements. The main novelty of this method is that it allows for the use of an FSS structure to reducing the in-band RCS of antennas. To validate the proposed method, a low RCS patch antenna resonating at 5 GHz is designed using this method. The simulated results show that the largest RCS reduction is about 15 dB at 5 GHz. A prototype of the proposed antenna is fabricated and tested in an anechoic chamber, and good agreements between the measured and simulated results are demonstrated.
In this paper, an optically transparent (OT) compact 4×4 Butler matrix (BM) operating at 2.4 GHz for Wi-Fi applications is proposed. The device has structured grids refined in quadrilateral cell shapes. The dimensions of cells are chosen based on a simple formulawhich guarantees a minimum required transparency levelin conjunction with a limited rounds of optimizations. A theoretical optical transparency value of 76.2% has been obtained without affecting the excellent electrical performance of the BM. Moreover, complimentary square split ring resonators (CS-SRRs) are patterned in the ground plane of each transparent transmission line in the BM. This loading technique provides a relative size reduction of 16.6% compared to a conventional structure. Simulated and measured results of the proposed design agree well with conventional BM's results. The proposed technique and its related features can be expanded to other microwave devices.
In this paper, a filtering antenna using a dual-mode resonator is presented. The rectangular patch performs not only as a radiator, but also as the last resonator of the bandpass filter. The dual-mode resonator works together with the patch antenna to form a third order bandpass filter with Chebyshev responses. The filtering antenna exhibits good performance, such as skirt selectivity, flat gain within the passband, and high out-of-band suppression.
A low cost and easy fabrication multilayer antenna for wireless applications was presented to cover the industrial, scientific, and medical ISM band of (5.725-5.875) GHz with a gain of 11.7 dB. The antenna was composed of a feeding patch fabricated on a Rogers RT/Duroid 5880 substrate, and three superstrate layers of Rogers RO3006 were located above the feeding patch at a specific height for each layer. The superstrate layers were added to enhance the bandwidth and gain of the antenna and reduce its side-lobe level and return loss. The simulated and measured results of the operating frequency, return loss, bandwidth, and gain for the antenna were presented. CST Microwave Studio was used in this design's simulation.
A high-performance microstrip low-pass filter (LPF) with low cutoff frequency, negligible passband insertion loss, very sharp transition band, and deep ultra-wide stopband is designed, fabricated and measured. The presented filter is realized using three types of resonators which are coupled C-shape defected ground structure (C-CDGS), mirrored series-resonant branch loaded by radial stub, and high impedance line loaded by radial stub. A novel equivalent circuit model of the C-CDGS resonator is created, and its corresponding parameters are also extracted. The proposed filter is experimentally verified through the measured results which show good agreement with electromagnetic simulations.
This paper presents a compact tri-band dual-polarized planar monopole antenna, which is linearly polarized in the lower and middle bands and circularly polarized in the higher band. The antenna is printed on a substrate with an asymmetrical ground plane and a loaded vertical stub. The vertical stub and asymmetrical ground plane are mainly used to make the antenna obtain circular polarization performance in the higher band. The antenna has been built and tested. Its measured 10-dB impedance bandwidths are 2.39-2.54 GHz, 3.38-4.12 GHz, and 4.57-6.04 GHz, which can fully cover all the 2.4/5.2/5.8 GHz WLAN bands, all the 2.4/5.5 GHz Wi-Fi bands, and 3.5/5.5 GHz WiMAX bands. In the higher band, the measured 3-dB axial-ratio bandwidth is 5.4-5.83 GHz.
We present a Hilbert curve fractal antenna operating at 2.45 GHz ISM and 5.5 GHz WLAN bands. The proposed antenna employs a third-order Hilbert curve and two shorting vias for antenna miniaturization and dual-band/mode operation. At 2.45 GHz, the antenna exhibits a monopole-like radiation pattern, while at 5.5 GHz, it provides a broadside radiation pattern, suitable for simultaneous on- and off-body communication using two distinct frequency bands. The antenna foot print is as small as 25.5 mm×25.5 mm. Simulation and measurement results demonstrate that the antenna gain is more than 1.9 dBi if the antenna is mounted on a ground larger than 40 mm×40 mm. The effect of human body presence on antenna performance was investigated by means of full-wave simulations locating the antenna on a human body phantom. It is shown that the proposed antenna is capable of maintaining its free-space performance over the human body phantom except for the gain reduction of 2.5 dBi at 5.5 GHz band.
A beam-scanning partially reflective surface (PRS) antenna is presented in this paper. By employing a reconfigurable feed network to a two-element phased array source, the PRS antenna can realize beam steering between -10° and 10° with respect to the broadside direction across an overlapped frequency range from 5.35 GHz to 5.76 GHz. Good agreement between the simulated and measured results is achieved, which validates its capability to be a good candidate for the modern communication systems.
A novel planar ultra-wideband (UWB) antenna with triple-notched bands using triple-mode stub loaded resonator (SLR) is presented in this paper. The basic UWB antenna consists of a circular-shaped radiating element, a 50 Ω microstrip feed line, and a partially truncated ground plane. Then, the resonance properties of the SLR are studied. Results reveal that the multiple-mode property of the SLR can be utilized in the UWB antenna design to achieve triple band-notched performance. To validate the design concept, a novel planar UWB monopole antenna with three notched bands respectively around the WiMAX band, WLAN band, and X-band satellite communication band is designed and fabricated. The results indicate that the proposed planar antenna not only retains an ultrawide 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 triple-band filter using triple-mode substrate integrated waveguide (SIW) resonator is presented in this paper. The proposed resonator consists of a square cavity with two additional metallic vias that split the first pair of degenerate modes (TE201 and TE102) at the diagonal of the cavity. Triple-band response is achieved by TE101, TE201 and TE102. The center frequencies of the first band and the third band can be controlled by appropriately adjusting the location of perturbation vias, while the second band keeps almost unchanged. A two-pole triple-band filter with two transmission zeros utilizing the coupled triple mode cavity resonators is designed and fabricated. The measured results agree very well with the simulated ones.
By using a composite coupling structure for coplanar waveguide (CPW)/microstrip, a new dual-band bandpass filter (DBBPF) stacking inverted Y-shaped CPW resonators and rectangular ring resonators is proposed. Two resonant frequency bands are simultaneously excited by the CPW feed line, However, it can be convenient to tune individually. Several transmission zeros are realized to improve the selectivity of the filter and achieve wide stopband rejection. Good agreement between simulated and measured results demonstrates the validity of this DBBPF.
In this paper a broadband radio frequency identification (RFID) tag antenna for the ultrahigh-frequency (UHF) band is designed. The proposed antenna consists of a first-order Hilbert fractal structure and a spiral structure. In order to ensure the conjugate matching between the tag antenna and the electronic chip, a T-matching structure is employed. The interaction between two radiating elements makes the proposed antenna a fractional bandwidth of 20% over the frequency range of 820 MHz-1010 MHz and a small size of 0.2092λ0×0.099λ0. Simulated and measured results validate the good performance of the designed tag antenna.
The ultra-wide band characteristic basis function method (UCBFM) is an efficient approach for analyzing wide band scattering problems because ultra-wide characteristic basis functions (UCBFs) can be reused for any frequency sample in the range of interest. However, the errors of the radar cross section calculated by using the UCBFM are usually large at low frequency points. To mitigate this problem, an improved UCBFs is presented. Improved UCBFs (IUCBFs) are derived from primary characteristic basis functions and secondary level characteristic basis functions (SCBFs) by applying a singular value decomposition procedure at the highest frequency point. This method fully considers the mutual coupling effects among sub-blocks to obtain the SCBFs. Therefore, the accuracy is improved at lower frequency points because of the higher quantity of current information contained in the IUCBFs. Numerical results demonstrate that the proposed method is accurate and efficient.
A compact circularly polarized (CP) crossed dipole antenna with chip inductors and square rings loaded for Global Positioning System (GPS) is proposed in this letter. The CP radiation is produced by crossing two dipoles through a 90° phase delay line of a vacant-quarter printed ring. Four chip inductors inserted in the dipole arms and four square rings loaded at the back of the dipole arms are introduced to obtain a compact dipole size. The plane dimension of the proposed antenna is 28 mm×28 mm, which can be widely used for GPS handheld devices. Details of the proposed antenna design and results are presented and discussed.
In this paper, a novel circularly-polarized (CP) patch antenna using organic magnetic substrate is proposed. This patch antenna works at 1.575 GHz frequency band which is for the global positioning system (GPS) application. The organic magnetic material is used to realize the miniaturization of antenna. To improve gain and axial ratio bandwidth of the antenna, fractal Hi-impedance surface electro-magnetic band gap (EBG) structures was used. The proposed antenna has been fabricated and measured. The simulation results for operating frequency band are shown to have good agreement with measurements.
A novel planar ultra-wideband (UWB) antenna with triple-notched bands is investigated and presented in this paper. The initial UWB antenna consists of a circular-shaped radiating element, a 50 Ω microstrip feed line, and a partially truncated ground plane. Then, by embedding a square ring short stub loaded resonator (SRSSLR) beside the microstrip feedline of the basic UWB antenna, band-rejected filtering properties in the satellite communication/wireless local area network/radio frequency identification for microwave access bands are generated. The notched frequencies can be adjusted according to specification by changing the SRSSLR. The results indicate that the proposed compact antenna not only retains an ultra wide bandwidth, but also owns triple band-rejections capability. The UWB antenna demonstrates omnidirectional radiation patterns across nearly the whole operating bandwidth that is suitable for UWB communications.
A new microstrip ultra-wideband (UWB) bandpass filter (BPF) with triple-notched bands is presented in this paper. The circuit topology and its corresponding electrical parameters of the basic microstrip UWB BPF are designed by modified genetic algorithm (MGA). Then, triple-notched bands inside the UWB passband are implemented by coupling a novel triple-mode stepped impedance resonator (SIR) to the main transmission line of the basic microstrip UWB BPF. The triple-notched bands can be easily generated and set at any desired frequencies by varying the designed parameters of triple-mode SIR. For verification, a new microstrip UWB BPF with triple-notched bands respectively centered at frequencies of 4.4 GHz, 5.9 GHz and 8.0 GHz is designed and fabricated. Both simulated and experimental results are provided with good agreement.
A simple 2×3 reconfigurable beam-forming network (R-BFN) for four-beam reconfiguration application is designed and implemented. The proposed R-BFN with two input ports and three output ports consists of a 2:1 power divider, a 90° hybrid, a 180° hybrid and a 2-bit phase shifter. The 2-bit phase shifter has two states: one is a 180° phase shifter (State 1); the other is a 0°/360° phase shifter (State 2). By introducing the 2-bit phase shifter, the constant phase differences of three output ports can be reconfigured. Specifically, as different input ports are excited, the R-BFN provides three output signals with equal power levels and the progressive phases of -120° and 120° when the 2-bit phase shifter at state 1, while -60° and 60° when the 2-bit phase shifter at state 2, respectively. When the proposed R-BFN is connected to an antenna array, a four-beam reconfiguration is obtained. Simulated and measured results show that good impedance matching, high port isolation, equal power division, and constant phase difference have been achieved simultaneously within the operation band of 2.4-2.6 GHz. The capability of the proposed R-BFN to reconfigure beams is also verified experimentally by using a 2.5 GHz dipole array.
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