Design of a composite dipole antenna array with direct feed is presented. In the form of printed-circuit antennas, the structure of the design consists of a doublet antenna and an elliptic loaded monopole antenna with a skirted dipole. As the load of the antenna array, this elliptic monopole provides wider bandwidth. Therefore, with the load possessing a radiation characteristic, it contributes to enhancing efficiency of the antenna array and hence the omni-directional radiation gain. A good agreement between simulated results by CST Microwave Studio® and tested results suggests that the reflection coefficient for the frequency range between 4.35 GHz to 5.0 GHz is lower than -10 dB. The out-of-roundness on H-plane is lower than 2dB and the maximum gain is higher than 6dB for the frequency range from 4.6 to 5.0 GHz. What's more, the gain per wavelength is about 4 dB, showing the antenna's excellence in miniaturization.
Behavioral modeling technique provides an efficient and convenient way to analyze and predict the performance of the RF power amplifiers (PAs) in system-level, and thus helps to constructe a suitable predistorter to linearize the PA system. To accurately describe the nonlinear dynamic characteristics of PAs, an orthonormal Hermite polynomial basis neural network (OHPBNN) is utilized to represent the PAs behavioral model, which outperforms, mainly in respect of modeling accuracy, the classic feedforward neural network using sigmoid activation functions. In addition, we apply an adaptive algorithm to determine the appropriate memory depth of PA behavioral model. Simulation results show that the proposed model provides more accurate prediction of the PAs output signal compared with classic neural network models.
A new broadband microstrip branch-line quadrature hybrid with very flat phase response is presented. The device is made by cascading four branch-line couplers with arbitrary power division. The novel design is based on the microstrip transposition of a broadband waveguide polariser . Across a 32% bandwidth centred at 9.3 GHz, the RL and the IL are respectively -15 dB and -3 dB/-4 dB; the phase difference is very flat, i.e. 90°±1.5°.
A novel microstrip grid array antenna that is simultaneously high in gain and wide in bandwidth is proposed. To enhance its bandwidth, the antenna adopts elliptically shaped and variably dimensioned radiation elements as well as a linearly tapered ground plane, and is optimized by a parallel genetic algorithm (GA) on a cluster system. A prototype antenna was fabricated and tested. Results of simulation and measurement agree well and show the antenna exhibits encouraging properties, e.g., a maximum gain of approximately tely 15.1 dBi at 5.8 GHz; the |S11| ≤ 10 dB bandwidth and the 3dB gain-drop bandwidth are 25.6% (from 5.03 GHz to 6.51 GHz) and 27.6% (from 5.0 GHz to 6.6 GHz), respectively, of the center frequency, both of which are much wider than that of conventional microstrip grid array antennas. Moreover, the overlap between the antenna's impedance bandwidth and the gain bandwidth results in a wide effective operating frequency bandwidth of 25.6%, which is the largest so far achieved for microstrip grid-array antennas.
The paper demonstrates a novel antenna which can achieve a broad impedance bandwidth and circularly polarized bandwidth with a suspended corner-truncated square patch and a new probe-fed rectangular strip. By incorporating a probe-fed rectangular strip inside a high substantial cavity (~ 0.144λ0), a broad impedance bandwidth (VSWR < 2.0) of 770 MHz (31.43%) is achieved. To obtain a good circularly polarized (CP) bandwidth overlap with the impedance bandwidth, two stubs with optimized lengths are loaded with the non-radiating edges of the corner-truncated square patch symmetrically. Measured results show that the CP antenna features a wide operating bandwidth of 10% ranging from 2.41 GHz to 2.66 GHz (VSWR < 1.5 and axial ratio < 3 dB) and that of 22.45% ranging from 2.31 GHz to 2.86 GHz (VSWR < 2 and axial ratio < 6 dB) and good radiation patterns with cross-polarization level (LHCP) lower than the co-polarization level (RHCP) by more than 20 dB at the broadside direction. The average gain of this antenna is recorded as about 8.16 dBi across the operating bandwidth.
Two SPDT switches that have low insertion loss with impedance-transformation networks are presented. The proposed SPDT switches are comprised of two shunt PINs and two quarter-wavelength microstrip lines together with impedance transformation networks, which canceled the capacitance effect at off-state and the inductance effect at on-state simultaneously. The simulated insertion loss performance is less than 0.3 dB and the fabricated ones exhibit on-state low insertion loss of 0.5 dB within the range of 4.6-4.8 GHz.
In this paper, a novel bandwidth reconfigurable bandpass filter is proposed. Based on a varactor loaded tri-mode resonator consisted of one constant odd mode and two independent varactor-tuned even modes, each passband edge of the proposed filter can be freely adjusted. By varying the reverse bias voltage applied to the varactor diode that is connected to the resonator, the bandwidth can be controlled conveniently. The resonant frequencies and Transmission Zeros (TZs) are derived and verified by both theoretical analysis and simulation. Stepped Impedance Resonator (SIR) is introduced to optimize the harmonic suppression. Finally, the measurement of the fabricated filter shows a fractional bandwidth tuning range of 11.4-32.0 % with a center frequency of 1.75 GHz, a quite low insertion loss of 0.4-1.1 dB, and wideband harmonic suppression up to 6 GHz. The measurement and simulated results show good agreement.
This paper presents an experimental investigations and analyses of ultra-wideband antenna diversity techniques and their effect on the onbody radio propagation channels. Various diversity-combining techniques are applied to highlight; how the overall system performance may be enhanced. Diversity gain is calculated for five different on-body channels and the impact of variation in the spacing between diversity branch antennas is discussed, with an emphasis on mutual coupling, correlation and power imbalance. Results demonstrate the repeatability and reliability of the analysis with error variations as low as 0.8 dB. The study highlights the significance of diversity techniques for non-line-of-sight propagation scenarios in body-centric wireless communications.
In this paper, a novel end-loaded quarter-wavelength resonator is investigated for the designs of wideband tunable bandpass filter (BPF) and bandstop filter (BSF). The novelty of the resonator lies in that two varactors are added to the two ends of the resonator, and then its resonant frequency can be bi-directionally tuned. As a result, the theoretical frequency tuning range can be significantly extended to approximately double that of the conventional tunable quarter-wavelength resonator. For demonstration, the proposed resonator is applied to design wideband tunable BPF and BSF. As expected, the tuning ranges are 52.4% and 53.5% for the BSF and BPF, respectively. Good agreement can be observed between the simulated and measured results.
A wideband dual segment three element triangular dielectric resonator antenna (TDRA) has been proposed for applications in X-band. Proposed antenna has been fabricated and tested. The simulation study of the antenna is carried out using Ansoft HFSS simulation software. The simulation results for input characteristics and radiation patterns of the proposed antenna are compared with corresponding experimental results at the resonant frequency. The simulation results are in agreement with measurements. The return loss-frequency characteristics of the proposed antenna are also compared with those of single element, and three element TDRAs.
This paper presents a novel wideband to narrow band reconfigurable log periodic aperture coupled patch array. The wide to narrow band reconfiguration is realized by closing a selected group of slot apertures, to deactivate the corresponding group of patches. The patches are fed with a modulated meander line through aperture slots. A wideband mode from 7 - 10 GHz and three selected narrow band modes at 7.1, 8.2 and 9.4 GHz are demonstrated. Potentially, the number of sub bands can be increased or decreased as can the bandwidth of the sub bands by selecting a specific number of active elements. To verify and demonstrate the proposed design method, a prototype has been developed with ideal switches. Very good agreements between the measured and simulated results are presented.
In this paper, we present a new type of a double-negative metamaterial absorber (MMA) with a periodic array composed of in-plane an electric-field-coupled-LC (ELC) resonator and a wire. In contrast to common MMA configurations, a metallic pattern layer of the proposed absorber is placed parallel to the incident wave propagation direction. An appropriately designed combination structure is etched on one side of an FR-4 substrate. Here, we fabricated a prototype absorber with a planar array of 66 × 30 unit cells. Our experiments showed that the proposed absorber exhibited a peak absorption rate greater than 86% at 10.1 GHz, irrespective of the incident angles up to 60°.
A high-speed triple-modulus frequency divider (FD) is designed and fabricated in a 90-nm CMOS process. With three pairs of nMOS switches inserted in the signal paths of the regenerative divider, the FD can offer three selectable division ratios of 1/2, 1/3, and 1/4. The corresponding behavior model of the proposed divider is utilized to explain the operation principle and analyze the locking range. From the experimental results, the divider consumes 6.8 mW of dc power from a 1.2-V supply voltage, and the locking ranges for the 1/2, 1/3, and 1/4 divide modes are 16-23.8, 12.3-18, and 16.8-22.8 GHz, respectively. The maximum input frequencies of 23.8, 18, and 22.8 GHz for the 1/2, 1/3, and 1/4 division modes are demonstrated that the divider is attractive for application to a frequency synthesizer.
In this paper, 4G smart planar dual-band phased array antenna suitable for fourth generation (4G) Long Term Evolution (LTE) and also Wireless Local Area Network (WLAN) systems is developed. The proposed planar array antenna is built using a microstrip rectangular U-slotted patch antenna element. Single element and linear sub-arrays with 1 x 2 and 1 x 4 dimensions of this element are designed, fabricated, and measured by the same authors. Separate feeding technique is used for each element of the smart planar array antenna; such that full beam-shaping can be achieved by steering the pattern main-loop to different angles in both azimuth and elevation directions with different amplitudes. Beam steering up to ±22 degrees can be achieved in both azimuth and elevation direction at 60 degrees phase shift without the presence of any grating lobes. At this value of phase shift, the gain is 22.62 dBi without changing in the mutual coupling. This is also suitable for 4G Multiple-Input Multiple-Output (MIMO) wireless mobile applications with reduced power consumption. Design simulation and optimization processes are carried out with the aid of the Agilent Advanced Design System (ADS) electromagnetic simulator that uses the full-wave Method of Moment (MoM) numerical technique.
This article presents a novel technique for isolation enhancement between two closely packed antennas. First, an inverted-U loop antenna (IULA) integrated into the top edge of a laptop panel is designed for 2.6-GHz LTE application. The mutual coupling between two designed IULA antennas has considerable effects by the placing positions of them. The results indicate the ground of the two IULA antennas placing against each other obtain the best isolation. At last, a three-element MIMO antenna was designed and measured. Although the gap between two adjacent antennas is only 1 mm, the experimental results show that the proposed two-element and three-element MIMO antennas achieve more than 20 dB isolation within the operating band. The important performances of antenna efficiency, envelope correlation, and channel capacity are also presented.
In this paper, a novel planar array antenna for multi-band linear polarization discrimination is proposed. The proposed array antenna consists of 12 patch elements and a double-balanced multiplier. A slot-ring and four diodes used in the multiplier also act as an antenna and amplitude detector, respectively. Furthermore, slot lines which are parts of feeding circuits also act as slot antennas. The Both-sided MIC technology is effectively employed to realize the feeding circuit which eliminates the extra impedance matching circuit. The array antenna is realized in a very simple and compact structure as all the antenna elements, feeding circuit and the multiplier/amplitude detector are arranged on both sides of a substrate. The proposed array antenna can discriminate ±45° linear polarization in three frequency bands. The ability of the proposed array antenna to discriminate orthogonal linear polarization is successfully confirmed in C and X band by the experimental investigation.
Based on the Composite Right/Left-Handed (CRLH) Transmission Line (TL) approach this paper presents a 3-band T-Junction power divider. The proposed design strategy uses a stub-loaded TL for the right-handed portion of the line; this way, with respect to a conventional CRLH line, one more degree of freedom is available. Experimental and numerical results referring to a prototype using surface-mount capacitors and inductors are reported and discussed. It is demonstrated that the artificial transmission line (ATL) here presented is an optimum candidate for designing high-added value microwave devices. Furthermore, based on the use of metal-insulator-metal capacitors and short circuited stubs, a monolithic implementation is also proposed.
In this paper a novel broadband quadrature power divider and its robust design method are presented. The QPD consists of a two-section power divider in combination with a 90-degree differential phase shifter. The two-section power divider is calculated to provide equal power split, high output port isolation, and good return loss at all three ports. The differential phase shifter consists of a composed right/left handed transmission line and pure-right handed transmission line named CRLHu-TL and PRHd-TL, respectively. The CRLHu-TL is divided into two parts; one of them consists of a pure-left handed section whose parasitic pad effects are represented by means of a pure right handed section named PRHp. On the other hand, the PRHd-TL is composed by a microstrip transmission line of characteristic impedance 50Ω and electrical length 50° and two sections equivalents to PRHp. The proposed circuit is applied to develop a broadband balanced amplifier with measured fractional bandwidth (FBW) of 124.4% at the center frequency of 2 GHz.
A novel segmented structure is proposed as a versatile approach to reject certain band of UWB printed monopole antennas (PMAs). To validate the effectiveness of the proposed structure, three UWB PMAs with typical circular, beveled rectangular and regular hexagonal patch shapes are selected and investigated. Good agreement between simulation and measurement shows that, by segmenting every selected patch into three parts, intensive coupling occurs between the center patch and the side patches at the target frequency, and consequently the band-notched function in IEEE 802.11a WLAN band is obtained. The measured radiation properties of these antennas are also presented and discussed. Moreover, a pair of equivalent lumped circuit models is presented, which provides a physical correlation between the notch band behaviors and the control parameters. The input impedance of the antennas calculated by the equivalent circuit models agree very well with the HFSS simulated results.
A high-selectivity microstrip wideband bandpass filter with six transmission zeros using transversal signal-interaction concepts is proposed. A fifth-order wide passband with six transmission zeros (0-2f0, f0 is center frequency of the passband) can be realized two transmission paths. The bandwidth and locations of the transmission zeros can be adjusted conveniently by changing the characteristic impedances of open stub and coupling coefficients of the open/shorted coupled lines. A prototype of planar wideband bandpass filter with 3 -dB fractional bandwidth 43.3% (2.33-3.63 GHz) is designed and fabricated. The measured and simulated results both indicate good performances of high selectivity and wideband harmonic suppression.