In this paper, we present a new design of a compact tri-band unequal power divider, which is composed of a circular-coupling power divider and a triple-band resonator. The unequal power dividing characteristic is realized by two circular shaped microstrip lines coupled through a circular shaped slot. The triple-band resonator, which comprises a conventional half-wavelength resonator, a short stub and an open stub, deals with the triple-bandpass performance. The proposed tri-band power divider with 1:1.6 output power ratios working at 3.4 GHz, 4.2 GHz, and 5.25 GHz is simulated and fabricated, and good agreements between the simulated and measured results are observed.
A novel quarter-mode substrate integrated waveguide (QMSIW) resonator with back-to-back triangular complementary split-ring resonators (CSRRs) etched on the waveguide surface is proposed in this paper. The proposed CSRR structures allow the implementation of a forward-wave passband propagating with high selectivity below the characteristic cutoff frequency of the conventional QMSIW. Utilizing the property of flexible open structure on QMSIWs' two sides, a cascaded quadruplet (CQ) bandpass filter (BPF) using the proposed QMSIW resonator and proximity coupling structure is presented. Compared with some other reported BPFs with SIW technique, the presented BPF using the novel QMSIW resonator has great improvements on size reduction and selectivity, simultaneously, with simple geometry. At the center frequency of 3.7 GHz, the designed BPF filter achieves a wideband with a fractional bandwidth up to 24.3% and a high selectivity with a shape factor of 1.23. The compact dimension of this filter is as small as 0.36λg×0.36λg, where λg is the guide wavelength at the center frequency. The proposed filter is simulated, fabricated and tested. The measured results are in good agreement with the simulation.
We present a new composite material containing calcium alginate microspheres incorporated into an epoxy matrix. The new material is mechanically stable and does not degrade over time. Its di-electric properties are extracted by model calculations and compared to the properties of some selected human tissues. Good agreement is observed, which identi es the proposed composite material as a good candidate for the use as a phantom material. The presented material is a two component composite and it is shown how its effective properties can be predicted by using appropriate mixing formulas.
A new wideband magneto-electric dipole antenna using coplanar waveguide (CPW) structure is proposed in this paper. The proposed antenna consists of a pair of horizontal triangular patches and two vertically oriented L-shaped strips. By introducing triangular patches working as an electric dipole, the antenna can operate in a wide band. With the use of L-shaped strips equivalent to a magnetic dipole, the antenna is low in profile. A microstrip feed line is located between the two L-shaped strips to form a coplanar waveguide structure and excite the antenna. By carefully adjusting the gap between the feed line and the strips, the impedance bandwidth can be improved largely. A parametric study is performed to provide information for designing and optimizing such an antenna. A prototype is fabricated and measured. The simulated and measured results show that the impedance bandwidth for SWR less than 2 of the proposed antenna is 58.7% (1.95-3.57 GHz). Due to the complementary nature of the antenna, the proposed antenna has a unidirectional radiation pattern with low-polarization and low back-lobe radiation over the whole operating band. Furthermore, the gain of the antenna is stable across the entire bandwidth.
In this paper, without using external power and active components, a design of pin coupled functional antenna tuner is presented. The tuner consists of two parts, a coupling pin and a tuning circuit. It is used to tune the bandwidth and antenna gain of the proposed slot patch antenna. The prototype, including a slot patch antenna and the tuner, was constructed and excited through a T-shape microstrip feed circuit resonated at 2.6 GHz. The impedance bandwidth BW (-10 dB return loss) of the slot patch antenna without coupling to the tuner was 3% referred to the operation frequency at 2.6 GHz. When the tuner was matched with the impedance 75 Ω through the coupling pin to the proposed antenna, the BW of the antenna was increased to 11% operated at 2.6 GHz. However, if the tuner was matched with the impedance 25 Ω to the proposed slot patch antenna, the impedance bandwidth of the antenna was increased 21% at operation frequency. Relatively uniform antenna gain was obtained when the matching impedance was decreased from 75 Ω to 20 Ω. In the meantime, the lower matching impedance corresponds to more reducing cross-polarization of the proposed slot patch antenna can be observed in the measured field patterns.
Wireless implantable body area network (WiBAN) is useful for monitoring vital human parameters in medical diagnosis such as breast cancer, heart attack and high blood pressure. The main objective of this paper is to design a small printed monopole antenna for WiBAN applications at 6.0 GHz. The small implantable antenna was tested in a lossy environment by being submerged into canola oil that mimics the dielectric properties of human breast fat tissue. The antenna performances were measured by using vector network analyzer (VNA) in order to evaluate the return loss and operating bandwidth of the antenna. The other parameters such as efficiency, radiation pattern and gain are evaluated by simulation of CST Studio 2012 software. When compared, there is good agreement between the simulation and measurement results. The simulated antenna gain and efficiency are 5.8 dBi and 97%, respectively, when submerged into canola oil. The antenna radiation pattern is directional, and it has 6 lobes implying its coverage in more directions which is of good benefit due to body movement. The antenna's polarization was tested by placing a wideband antenna at several degrees around the proposed antenna. The value of S21 was also analyzed to investigate the path gain of the selected links.
This paper considers the radar scenes which contain numerous rapidly changing terrains, i.e., there are more than one clutter-edge in the environment. This kind of radar scenes incurs sharply degradation in the performance of the present adaptive constant false alarm rate (CFAR) detectors as the statistical characteristic of reference cells is highly heterogeneous. To solve this problem, we propose a homogenous reference cells selector to improve the performance of CFAR detector in highly heterogeneous environment. The selector is comprised of an M-N clutter-edge detector cascading a terrain classifier. The M-N clutter-edge detector is used to obtain multiple clutter-edges in heterogeneous environment. With the detected clutter-edges, the terrain classifier is derived to obtain identical distributed range cells. Based on the selector, a modified Log-t-CFAR detector is suggested. Finally, the performance of the proposed selector and CFAR detector is evaluated by measured data and computer simulation.
A new broadband multiple-input multiple-output (MIMO) antenna with good isolation and compact size is proposed. The proposed antenna consists of two G-shaped elements in the upper layer and two inverted L protrude branches and a T slot etched in ground which is used to reduce the mutual coupling. This planar antenna has a bandwidth of 100% with |S11| ≤ -10 dB from 2.26 to 6.78 GHz. The value of isolation between the two antenna elements is more than 22.5 dB in the whole band. The experimental results verify the simulations.
Computer keyboards are often used to transmit confidential data such as passwords. The sensitive information such as keystrokes could be recovered by using the electromagnetic (EM) waves from the electronic components of the keyboard. In this paper, we have investigated the information leakage on the ground line of the PS/2 serial cable due to crosstalk and radiative coupling. The coupling principles are analyzed firstly. And then, through the experiments we found that the signals of keystrokes could leak to the ground line network which could then be detected on the other power outlets whose share the same electric line. Lastly, the eavesdropping experiments demonstrated that the keystrokes could be reproduced on the other places of the ground line network with no trace.
This paper presents two novel dual-mode dual-band bandpass filters (BPFs) by using stubs loaded coupled line. The analytical equations of their transmission poles and transmission ze-ros are given by the classical even-/odd-mode method. Design rules for two dual-band BPFs are al-so given, which shows the easily tuned passband frequency locations and in-band performance. As examples, two dual-mode dual-band BPFs, dual-band filter A with central frequencies (CFs) at 3.5/6.8 GHz and -3 dB fractional bandwidth (FBW) of 14%/10%, while dual-band filter B with CFs at 2.4/6.8 GHz and -3 dB FBW of 43%/16% are designed, fabricated and measured. Good agree-ment can be observed between the simulations and measurements. These two filters exhibit simple design procedures, simple physical topology, low insertion losses, good return losses, high isolation and compact sizes.
A compact quadrature hybrid coupler with harmonic suppression adopting lumped-element band-stop resonator is proposed aiming for bandwidth improvement. Conventionally, harmonic rejection is realized by three band-stop resonators in lumped hybrid design. The using of three band-stop resonators can realize better harmonic suppression while exhibiting narrower frequency response. So as to improve operation bandwidth performance, the number of band-stop resonator applied in this proposed topology is minimized to one. Trading off with acceptable reduction in harmonic rejection, the proposed hybrid can enlarge working bandwidth with fewer lumped devices. Detailed design and theoretical analysis are presented and the expressions of lumped elements with dependence of rejected harmonic frequency are obtained. To validate the analysis, three 2.45 GHz couplers are fabricated on an FR-4 printed circuit board. The experimental results exhibit 27.3%, 26.9% and 23.3% operation bandwidth with better than 16 dB, 17 dB, and 21 dB harmonic suppressions at 4.9 GHz, 6.1 GHz, and 7.35 GHz, respectively. Less than 0.8 dB amplitude imbalance and 2° phase error are achieved over the whole operation frequency for the all three couplers, which are matched well with theoretical analysis.
This paper proposes a square ring patch antenna for GPS L1 band application. The square ring patch located on the center of an FR4 substrate was truncated a square to guide two resonant modes. The dimensions of the truncated square located on the center of the patch controls the antenna's frequency band. Larger truncated square creates longer resonant path that decreases the resonant band. To achieve the CP radiation patterns, the corner-fed method and a truncated L-shaped slot on the ground plane are applied. After the size of the truncated L-shaped slot is optimized, the currents of Eθ and Eφ are around 90° shifts that make the antenna's AR lower than 3 dB. By switching the positions of the feed point and the L-shaped slot, both RHCP and LHCP can be obtained individually. Beside the CP operation, the proposed design also has advantages of planar structure, simple design, low cost, and good performances.
A novel approach for the design of a compact multiband monopole antenna for improving radiation characteristics at higher resonant frequencies is presented. The proposed structure consists of a conventional printed monopole loaded with spiral ring resonators and fed by microstrip. When at higher resonant frequency, the electrical length of the conventional monopole antennas is relatively large and the surface currents distribute on the patch periodically which will degrade the omnidirectional property. To achieve good radiation characteristics at the upper bands, two spiral ring strips are inserted into the microstrip line on the different layer and connected through via hole. Thus, the direction of surface currents on the spiral ring strips changes with the alteration of spiral structure and their effects on the radiation pattern are reduced. The radiation pattern is mainly contributed by the surface current on the microstrip line and very good stable radiation pattern can be obtained within all the operating bands. In comparison to the previous printed strip monopole structures, the miniaturized antenna dimension is only about 28 mm×20 mm×1 mm. The experimental results show that the proposed antenna can provide operating bands which meet the required bandwidths specification of 2.4/5.2 GHz WLAN and 3.5 GHz WiMAX standard. Detailed design considerations of the proposed antenna are described, and both the simulated and measured results of the proposed antenna are also presented and discussed.
A compact dual-band band-pass filter is proposed in this paper. The central frequencies of the passbands are around 2.46 GHz and 5.86 GHz. There are two resonators located at the top side layer and the bottom side(the CPW) layer, respectively. Dual-resonance operation usually needs two resonators on the same layer to generate two passbands simultaneously. However,in this paper the size can be reduced efficiently by connecting resonators at two layers through via-holes to implement dual-band performance. Furthermore, the stop-band for this novel filter with T slot-line, L-line and rectangular micro-strips can be extended to 30 GHz. To verify the feasibility of the design above, a dual-band band-pass filter has been implemented on a Rogers RT5880 substrate (thickness is 0.508 mm). This filter with passbands operated at 2.46 GHz and 5.86 GHz can finely meet the IEEE 802.11 n wireless local area network (WLAN) bands requirements.
Mechanical distortions of phased array antennas make transmit pattern distort. The transmit pattern cannot be simply calibrated by compensating the position error of each element since the effect of the mechanical distortions is angle-dependent. To solve this problem, we treat the element position errors measurement as prior knowledge and propose a knowledge-aided (potentially cognitive) transmit pattern design method. When the mechanical distortions occur, the cognitive transmit pattern can still place pattern nulls in the directions of interferences while preserving the main beam response of the target of interest. The proposed method is validated by simulation results.
In this study, a novel dual band-notched ultra-wideband (UWB) antenna has been proposed and discussed. The proposed antenna is fed by a micro-strip line and in the square-etched radiation patch a T-shape parasitic stub is attached. On the other hand, a pair of parasitic parallel micro-strip lines are also added on the ground plane, one of which is shorted to the radiation patch by a short-pin through dielectric substrate. The two parasitic units are to achieve band-notched characteristics at 3.3-3.7 GHz and 5.15-5.85 GHz, respectively. In order to realize impedance matching over the ultra-wideband, two arc-shape cuts are made symmetrically at the junction of feed-line and radiation patch. The simulated and measured results, including return loss, radiation pattern, group-delay and peak gains are in good agreement with theory analysis which validates our design concept.
An asymmetric coplanar waveguide (ACPW)-fed zeroth-order resonant (ZOR) antenna with extended bandwidth is investigated. By embedding a strip connected between the metallic patch and an ACPW ground plane, another resonant frequency at 2.53 GHz is achieved. The bandwidth enhancement of designed antenna can be obtained when the zeroth-order resonant frequency and the resonant frequency at 2.53 GHz are merging together. The size of the antenna is only 15×22×0.8 mm3 with simple planar structure. A prototype of the proposed antenna has been constructed and experimentally studied. The measured results show that operating bandwidths with 10 dB return loss are about 510 MHz (2.49-3.0 GHz), the simulated peak gain of 1.59 dBi at 2.68 GHz, which is suitable for WiMAX (2.5 GHz-2.69 GHz) application.
In this paper, a novel compact ultra-wideband (UWB) microstrip bandpass filter (BPF) with a notched band using the proposed multi-stub loaded ring resonator (MSLRR) is presented. The MSLRR is constructed by loading four open stubs in a ring resonator, i.e., one pair of high-impedance stub at the top side and another two low-impedance stubs at the bottom side locations. Five modes, including two odd modes and three even modes, could be designed within UWB band. Moreover, two transmission zeros (TZs) are generated by the ring structure, leading to a quasi-elliptic function response that enhances the selectivity significantly. Two slotline split-ring resonators (SRR) are used to create a narrow notched band at 8.3 GHz. The simulated and measured results are in good agreement and show good in-band filtering performance and sharp selectivity.
A closely-packed (4 mm) diversity slot antennas operating in the UWB frequency is proposed. High isolation (S21 < -20 dB) of two closely-packed slot antennas can be easily achieved in a broad band by taking advantage of the directional radiation characteristics of slot antenna. Quarter-wavelength slot resonator is adopted to improve the isolation in the low-band of the UWB. The simulated current distribution and the radiation patterns of the single antenna element with and without slots are also presented to explain the mechanism of decoupling in the diversity system. Furthermore, the diversity performance of correlation coefficient, mean effective gains (MEGs), diversity gain (DG) are also studied.
A compact, parasitic array antenna printed on both sides of the substrate to generate dual Notches is introduced. The antenna is composed of one driver and two directors. Both directors are discretely segmented and are twisted with each other to minimize the radiation interference from one director to the other at each resonance. The antenna is optimized for realized gains in the director direction at the two resonant frequencies. The optimized antenna has been fabricated and measured to verify the simulated results. At both resonances, the measured realized gains in the director direction are greater than 8.5 dBi, and the front-to-back ratios are more than 10 dB.
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