			Home About us Contact

Operating Frequency (operating + frequency)

Distribution by Scientific Domains

Engineering	95%

Selected Abstracts

Thickness-Dependent Properties of Relaxor-PbTiO3 Ferroelectrics for Ultrasonic Transducers

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010
Hyeong Jae Lee
Abstract The electrical properties of Pb(Mg1/3Nb2/3)O3 -PbTiO3 (PMN-PT)-based polycrystalline ceramics and single crystals were investigated as a function of scale ranging from 500 ,m to 30 ,m. Fine-grained PMN-PT ceramics exhibited comparable dielectric and piezoelectric properties to their coarse-grained counterpart in the low frequency range (<10 MHz), but offered greater mechanical strength and improved property stability with decreasing thickness, corresponding to higher operating frequencies (>40 MHz). For PMN-PT single crystals, however, the dielectric and electromechanical properties degraded with decreasing thickness, while ternary Pb(In1/2Nb1/2)O3 -Pb(Mg1/3Nb2/3)O3 -PbTiO3 (PIN-PMN-PT) exhibited minimal size-dependent behavior. The origin of property degradation of PMN-PT crystals was further studied by investigating the dielectric permittivity at high temperatures, and domain observations using optical polarized light microscopy. The results demonstrated that the thickness-dependent properties of relaxor-PT ferroelectrics are closely related to the domain size with respect to the associated macroscopic scale of the samples. [source]

Lateral load distributions on grouped piles from dynamic pile-to-pile interaction factors

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 2 2009
Der-Wen Chang
Abstract The load distributions of the grouped piles under lateral loads acting from one side of the pile cap could be approximately modeled using the elasticity equations with the assumptions that the underground structure is rigid enough to sustain the loads, and only small deformations of the soils are yielded. Variations of the soil,pile interactions along the depths are therefore negligible for simplicity. This paper presents the analytical modeling using the dynamic pile-to-pile interaction factors for 2,×,2 and 2,×,3 grouped piles. The results were found comparative with the experimental and numerical results of other studies. Similar to others' findings, it was shown that the leading pile could carry more static loads than the trailing pile does. For the piles in the perpendicular direction with the static load, the loads would distribute symmetrically with the centerline whereas the middle pile always sustains the smallest load. For steady-state loads with operating frequencies up to 30 Hz, the pile load distributions would vary significantly with the frequencies. It is interesting to know that designing the pile foundation needs to be cautioned for steady-state vibrations as they are a problem of machine foundation. However, for transient loads or any harmonic loads acting upon relatively higher frequencies, the pile loads could be regarded as uniformly distributed. It is hoped that the numerical results of this paper will be helpful in the design practice of pile foundation. Copyright © 2008 John Wiley & Sons, Ltd. [source]

A reconfigurable design for bandwidth enhancement of circularly polarized slot antennas

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2010
Tsung-Hsun Hsieh
Abstract A reconfigurable design is proposed to improve the circular polarization (CP) operating bandwidth of an annular-ring slot antenna fed with an L-shaped coupling strip. The design involves four voltage-controlled varactor diodes, which are placed below the slot and symmetrically distributed along the circumference of the slot. When all antenna dimensions remain constant, the CP operating frequency of the slot antenna can be decreased by varying dc voltage values. In addition, theses CP operating frequencies, which are corresponding to different dc voltage values can form a successive frequency band, and the available CP bandwidth is thus improved. Experimental results indicate that with the reconfigurable design, the 3-dB axial-ratio CP bandwidth can be increased by a factor of 4 for the annular-ring slot antenna with a reflector. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1377,1380, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25192 [source]

A novel parallel-coupled line diplexer excited using slot-line resonators for ultra-wideband communications

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2009
Hon Kuan
Abstract In this letter, a novel design of microstrip diplexer used for ultra-wideband communication has been proposed. The primary structure of the diplexer comprises two different parallel-coupled line structures with slot-line resonators (SLRs), which are used for generating the filtering response with high-channel selectivity. The diplexer is designed to have the lower and higher passband with the operating frequencies at 3.2,4.8 GHz and 6.5,9.8 GHz, respectively. Experimental results also show a good agreement with the simulated results. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1552,1555, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24356 [source]

Compact dual-band filter design using crossly coupled ,/4 SIRs embedded with spur-line for WLAN applications

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2008
Pow-Wen Chen
Abstract This article presents a compact dual-band bandpass filter (BPF) design using ,/4 stepped impedance resonators (SIRs) embedded with spur-line for the WLAN applications. The filter covers both the operating frequencies of 2.45 GHz and 5.2,5.8 GHz. The crossly coupled mechanism is used in the filter design to provide attenuation poles by the passband edges for enhancing the signal selectivity and increasing stopband rejection levels. The tapped-line is incorporated in feed structure to save the circuit space. The spur-line is embedded in each I/O SIRs to push the upper stopband limit to a higher frequency. Experiments are conducted to verify the circuit performance. A good agreement is observed between the simulation and the measurement. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2807,2810, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23846 [source]

Dual-band filter design of combined half and quarter wavelength SIRs for WLAN applications

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2008
Pow-Wen Chen
Abstract This article presents a dual-band bandpass filter composed of ,/2 and ,/4 stepped impedance resonators for the wireless local area network applications. The filter covers both the operating frequencies of 2.45 GHz and 5.2-5.8 GHz. The doubly parallel-coupling mechanism is used in the filter design to reduce the insertion losses and to gain a wider bandwidth. The cross coupling configuration and the tapped-line I/O feed are adopted in this filter design to provide the attenuation poles for improving the signal selectivity and stopband rejection levels. Experiments were conducted to verify the circuit performance. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 13,15, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22979 [source]

Internal DTV antenna for folder-type mobile phone

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2006
Kin-Lu Wong
Abstract By using the upper and lower ground planes of a folder-type mobile phone, a novel internal shorted dipole antenna for digital television (DTV) signal reception in the 470,806-MHz band is presented. The shorted dipole antenna further comprises an internal matching circuit, which includes a chip capacitor and two narrow metal strips, for achieving improved impedance matching over the DTV band of 470,806 MHz. The proposed DTV antenna was constructed and studied. The measured return loss for the operating frequencies over the DTV band is better than 2.5:1 VSWR. In addition, good radiation characteristics are also obtained. Design considerations of the proposed internal DTV antenna are described. A parametric study of the internal matching circuit on the impedance matching of the antenna is also presented. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1015,1019, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21587 [source]

A planar dual-meander-line antenna for multiband mobile handsets

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2006
Hai-Ming Hsiao
Abstract A planar dual-meander-line antenna consisting of three branch strips for a low-profile GSM/DCS/PCS/WLAN multiband mobile handset is proposed. The branch strips are designed to operate as quarter-wavelength structures at 900 and 2000 MHz, respectively, and the obtained impedance bandwidths are 120 MHz (about 13.2%) and 924 MHz (about 44.4%) for covering the required bandwidths of the GSM (890,960 MHz) and DCS/PCS/UMTS/WLAN (1710,1880/1850,1990/1920,2170/2400,2484 MHz) bands. The proposed antenna can be mounted on top of a mobile phone with a low profile of 20 mm from ground plane. The measured antenna radiation patterns are approximately omnidirectional across the multiresonant bands. Peak antenna gains for operating frequencies across the GSM/DCS/PCS/UMTS/WLAN multiple bands are measured to be 1.8 and 2.9 dBi, respectively, with gain variations within 0.5 dBi. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 883,888, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21507 [source]

Trans-admittance control for eliminating the temperature effect of piezoelectric transformer in the CCFL backlight module

INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 8 2008
Yu-Kang Lo
Abstract A half-bridge (HB) resonant inverter for driving a cold cathode fluorescent lamp (CCFL) backlight module with a piezoelectric transformer (PT) is analyzed in this paper. The resonant inductance of the HB inverter is expressed as a function of the load current, the load resistance and the PT circuit parameters. Also, the trans-admittance of the PT-CCFL combination network is measured to track the operating frequency for the HB resonant inverter, which may be varied due to the temperature rise of PT. The lamp driving current and power can thus remain almost constant in a wide temperature range. Experiments show that the observed results match the theoretical analyses. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Performance comparisons for adaptive LEO satellite links

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 3 2006
William G. Cowley
Abstract This paper considers the potential to achieve improved throughput in time-varying satellite links which have flexibility in information bit rate and/or transmit power. We assume that other parameters of the link budget such as antenna gains and operating frequency are fixed. Simple results are derived, which illustrate what improvements in data throughput or power consumption are possible under two low-earth orbit scenarios: inter-satellite links and satellite to ground communications. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Size-reduced defected ground microstrip directional coupler

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2010
Ashraf S. Mohra
Abstract In this article, size reduction and harmonic suppression in coupled-lines microstrip directional couplers is attained using dumbbell, and reshaped dumbbell slots, as defected patterns, specifically placed under the metering position in the ground plane. Quantitative investigation of the performance of the directional coupler as controlled by the variations of the DGS rectangular slots height, DGS gap length, and the DGS reshaped rectangular slot height is presented. This concept is further illustrated experimentally for a 12 dB coupler realized on RT/Duroid 5880 substrate. The proposed DGS design confers size reduction because of the shift of the operating frequency to lower values. The measurements are in a good agreement with the simulated results and emphasize the size reduction and the harmonics suppression of the DGS coupled-lines microstrip directional coupler. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1933,1937, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25410 [source]

A reconfigurable design for bandwidth enhancement of circularly polarized slot antennas

Improved phase noise for dielectric resonators oscillators with broadband tuning

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2009
Liang Zhou
Abstract In this article, we describe a method of design of very low phase noise dielectric resonators oscillators at 13 GHz. By using two Silicon Germanium transistors with total gains 8 dB and lower flicker noise corner between 10 kHz and 40 kHz, the phase noise of the oscillators can be achieved ,125 dBc/Hz at 10 kHz offset. The resonator has unloaded Q around 14,000 at operating frequency and is then optimized and coupled to the amplifiers for minimum phase noise where QL/Q0 = 1/2 hence S21 = ,6 dB. To incorporate tuning, phase shifter is also investigated. The phase noise measurement system is also presented using two identical oscillators phase locked at the same frequency.© 2009 Wiley Pe riodicals, Inc. Microwave Opt Technol Lett 51: 1312,1316, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24334 [source]

Design a new structure 2.4 GHz/5.2 GHz dual-band bandpass filters on the MgTa1.5Nb0.5O6 ceramic

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2009
Cheng-Fu Yang
Abstract In this article, a ,/2 U-shaped hairpin resonator was contained in a modified end-coupled microstrip line. The increase of the sizes of U-shaped hairpin resonator and modified end-coupled microstrip line had no influence on the lower operating frequency and would shift the upper operating frequency to lower values. After finding the best designed parameters, a miniature dual-band microstrip bandpass filter with three transmission zeros generated in the stop-bands was developed on the MgTa1.5Nb0.5O6 microwave dielectric ceramic substrates. The dual-band filter had the central frequencies of 2.45 and 5.2 GHz and was suitable for the applications in the modern WLAN communication. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1085,1087, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24264 [source]

Analysis of frequency division in microstrip circuits by using the FDTD method

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2008
Oscar González
Abstract The accurate time-domain simulation of the nonlinear dynamics of circuits containing distributed elements is of great interest. Specially at high frequencies, it is essential to consider phenomena, such as crosstalk, packaging effects, and electromagnetic interaction between active and passive elements. These effects are mainly due to the distribute components of the circuit. Therefore, the accuracy in the instability or oscillation analysis of nonlinear circuits is often limited by the models used for such elements. Commercial simulators based on the equivalent-circuit approach hardly take into account the mentioned effects. In this work, the finite-difference time-domain (FDTD) method is applied to the nonlinear simulation of a diode-based microstrip circuit exhibiting a parametric frequency division by two. The FDTD method rigorously solves Maxwell's curl equations in the time domain providing a full-wave characterization of the distributed elements of the circuit. In the example considered, a relatively low operating frequency has been selected to allow a reliable comparison between the results obtained by the proposed technique and those provided by a circuit-based commercial simulator. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1300,1302, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23352 [source]

A miniaturized patch antenna at 2.4 GHz using uni-planar compact photonic band gap structure

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2008
Abdelnasser A. Eldek
Abstract This article presents a miniaturized patch antenna for wireless applications at 2.4 GHz. A conventional microstrip-fed patch antenna is firstly designed to operate close to 10 GHz. Then, the antenna is modified to operate at lower frequency without changing the antenna dimensions. First, the ground plane is replaced with a uniplanar-compact-photonic-band-gap (UC-PBG) structure. Then, a backed conductor is placed close to the UC-PBG and connected to it through four vias. These two modifications are utilized to decrease the lower operating frequency of the antenna from 9.7 to 2.42 GHz. Thus, a 75% size reduction factor is obtained. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1360,1363, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23381 [source]

Injection-locked GaInp/GaAs HBT frequency divider with stacked transformers

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2007
Hung-Ju Wei
Abstract The first integrated GaInP/GaAs heterojunction bipolar transistor (HBT) injection-locked frequency divider (ILFD) with the stacked transformers is demonstrated around 10 GHz. The stacked transformers formed by only two metal layers provide the inductive coupling in the cross feedback and separate biasing for base and collector to allow for the larger output swing in the LC tank and obtaining wide locking range. Under the supply voltage of 5 V and core power consumption of 20.5 mW, the locking range is 7.8% of the center operating frequency. The chip size of the entire ILFD including probing pads is 1.0 × 1.0 mm2. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2602,2605, 2007; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.22737 [source]

Bandwidth enhancement design of PIFA with slotted T-shaped ground plane

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2006
Xu Jing
Abstract A novel, planar inverted-F antenna with a slotted T-shaped ground plane is proposed. It is shown that introducing a cross-shaped slot onto the T-shaped ground can greatly broaden the bandwidth without affecting the operating frequency. The measured bandwidth of the proposed antenna is from 1950 to 2620 MHz. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2106,2108, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21875 [source]

A compact, broadband antenna for planetary surface-to-surface wireless communications

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2006
Philip Barr
Abstract The compact microstrip monopole antenna (CMMA) is a novel antenna design that combines a microstrip patch antenna with a 3D structure to attain a highly directive, broadband, compact antenna. A tri-lobed patch (TLP) is designed to minimize the patch's area while reducing the antenna's operating frequency. A grounding wall (GW) connects the patch to the ground plane and a vertical-enclosure wall (VEW) extends up, away from portions of the patch's perimeter. This VEW supplies the antenna with a higher directivity in the radial direction and also reduces the operating frequency. The CMMA was designed to operate at 2.23 GHz, but experimental results have shown this antenna resonates at 2.05 GHz which is on the order of approximately ,0/11.6 with respect to the antenna's largest dimension, with a directivity and bandwidth of 6.0 dBi and 130 MHz (6.3%), respectively. This miniature, radially emitting antenna makes the CMMA attractive for planetary-based surface-to-surface communications. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 521,524, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21397 [source]