Dual frequency circularly polarised proximity-fed microstripantenna

The design feasibility of a three-layer proximity-coupled fed microstrip antenna structure for dual frequency operation with circular polarisation is demonstrated. As a proof of concept an antenna designed for operation at the two GPS frequencies is fabricated. The measured results show that dual axial ratios can be obtained at both frequency bands     

Dual slot-coupled microstrip antenna for dual frequency operation

A new dual slot-coupled circular antenna for dual frequency or dual polarisation operation is proposed. By optimising the placement of the two slots, high isolation between two ports is achieved. Experimentally, an isolation of more than 35 dB is obtained at L-band.<>     

Dual-band circularly polarised microstrip antennas with a singlefeed

The authors present a novel technique for obtaining circularly polarised (CP) dual frequency operation by using two spur-link band-stop filters within the perimeter of a microstrip patch antenna with optimum feed point location and aspect ratio. This circularly polarised dual frequency operation can be obtained without increasing either the size or the thickness of the patch. Furthermore, through several experiments the authors also demonstrate that the location of the feed point establishes and controls a trade-off between axial ratio and impedance bandwidth     

Dual-band dual polarised printed antenna element

A novel printed antenna element capable of providing dual polarised operation over two widely separated frequency bands is described. The element consists of a perforated proximity-fed microstrip patch antenna operating at the lower frequency, layered over a subarray of aperture coupled microstrip elements operating at the upper frequency. Results for a specific example operating at L and X bands (a frequency ratio of 8:1) are presented. The impedance bandwidth for both bands is >6%, with isolation within bands >20 dB and isolation between bands >40 dB. The element and feed network also has the advantage of being compact enough to be used in arrays, providing dual polarised dual-band operation from a single low-profile aperture     

双频贴片天线研究与设计

无线通信的发展对天线(尤其是贴片天线)的各项性能提出了新的要求。与此同时，双频天线的应用也愈为广泛。总结了贴片天线的主要双频解决方案，包括正交模、多贴片、电抗性加载以及空气缝隙双频贴片等方式，并提出了相应双频贴片天线的适用场合。最后，结合HFSS仿真设计了一个双频双贴片天线，讨论了该天线特性，并对双频天线未来的发展趋势进行了展望。     

Iterative technique for analysis of multi frequency patch antenna

This paper presents an efficient implementation of iterative method including fast modes transformations (fmt) for analysing dual frequency patch antenna. The optimisation of the dual frequency operation requires a set of calculation that is quite heavy to carry out with conventional numerical techniques. The employed one permits to shorten the calculation time, hence gives more freedom for the optimisation. This becomes essential as the structure becomes more complex, i.e. arrays. Two examples are treated and compared with experimental and theoretical results obtained through a classical technique.     

Proximity coupled linearly polarised patch antenna for dualfrequency use

A novel linearly polarised patch antenna for dual frequency operation is presented. Experimental results of the proposed antenna fed by microstrip lines using an electromagnetic coupled method are shown to verify the dual frequency use with a high isolation between the transmit and receive ports     

Broadband dual frequency microstrip antenna

A new dual port microstrip antenna geometry for dual frequency operation is presented. The structure consists of the intersection of two circles of the same radius with their centres displaced by a small fraction of the wavelength. This antenna provides wide impedance bandwidth and excellent isolation between its ports. The gain of the antenna is comparable to that of a standard circular microstrip antenna operating at the same resonant frequency. A theoretical analysis for calculating the resonant frequencies of the two ports is also presented     

A Wide Locking-Range Frequency Divider for LMDS Applications

A fully integrated frequency divider with an operation frequency up to 20 GHz is designed in 0.18-mum CMOS technology. The frequency divider includes two stages to divide the input signal by a factor of 4. A wide locking range from 18.8 to 23.2 GHz was obtained with a low phase noise of -134.8 dBc/Hz (1-MHz offset) at an output frequency of 4.7 GHz. The first stage is designed by an analog methodology with the varactors to extend the locking range, while the second stage is designed by a digital approach with the RF devices for a high operation frequency. With the advantages of both designs, this frequency divider is operated at the frequency range suitable for LMDS applications.     

Transition to pulsed operation in short external-cavity FMsemiconductor lasers

Conditions are established for the occurrence of a transition from FM operation to pulsed output in short external-cavity FM semiconductor lasers. It is shown that there are dual operating points around which FM operation is possible. The position of the modulation frequency in relation to these two FM operating frequencies determines the type of behavior exhibited by the configuration. In particular, pulsed and mixed pulsed-FM behavior is observed when the modulation frequency is between the two possible FM operating frequencies     

Time-frequency duality

This paper develops a concept of duality, called time-frequency duality, which is applicable to a class of networks called communication-signal-processing networks. Such networks consist of an interconnection of basic elements such as filters, mixers, delay lines, etc. The usefulness of time-frequency duality stems from the fact that two situations which may be quite distinct physically can have identical behavior patterns except for an interchange of the roles played by time and frequency. As a result, the solution to a detection or estimation problem may be found directly from the solution of the dual problem, if known, merely by replacing variables and quantities by their duals. This application of time-frequency duality is illustrated in the paper by the problem of measuring the transfer function of a scatter medium by means of an optimal gating operation prior to spectrum analysis. Another benefit to be obtained from time-frequency duality is the generation of new ideas for communication signal processing techniques. We illustrate this type of benefit by constructing the dual of the Kineplex communication system. A third benefit is the additional insight gained into a communication problem by the ability to look at it in another way. This benefit is illustrated by the characterization of time-variant linear channels. It is demonstrated that such channels may be characterized in an interesting symmetrical manner in time and frequency variables by defining dual system functions.     

Analysis and design of a dual-band circularly polarized microstrippatch antenna

In the last decade a great effort has been made concerning research on frequency agility of microstrip patch antennas. In all these attempts an increase in length or height of the patch is generally expected and there is a tradeoff between wider bandwidth and good axial ratio. This paper presents the analysis and design of a novel dual-band circularly polarized microstrip patch antenna using a spur-line band-stop filter and a perturbation segment technique. This dual frequency operation can be obtained without increasing either the size or the thickness of the patch while other features are not degraded     

Dual band tunable microstrip patch antenna

A simple design for a dual-band microstrip antenna operating at 3 GHz is presented. The dual band operation is obtained when the antenna is loaded with a cross-line shorted with a ground plane at one end. The frequency separation is found to be sensitive to the position of the cross-line     

磁性基片双频三角形微带贴片天线

采用国内首创的新型有机磁性材料做基片，提出一种创新设计实现了微带贴片天线的双频工作。这是通过在三角形微带贴片的底边加载矩形凹槽来实现的，结构简单且双频比易于调节。由于采用了新型磁性基片，使天线尺寸比相同频率的常规贴片天线缩小，而具有比常规微带天线宽得多的带宽。文中给出了仿真和实测结果，证明了设计的有效性．     

Design and Optimization of Dual Band Microstrip Antenna Using Particle Swarm Optimization Technique

Dual-frequency operation of antenna has become a necessity for many applications in recent wireless communication systems, such as GPS, GSM services each operating at two different frequency bands. A new technique to achieve dual band operation from different types of microstrip antennas is presented here. An evolutionary design process using a particle swarm optimization (PSO) algorithm in conjunction with the method of moments (MoM) is employed effectively to obtain the geometric parameters of the antenna performance. In this article a PSO based on IE3D®? method is used to design dual band inset feed microstrip antenna. Maximum return loss is obtained at 2.4 GHz is ?43.95 dB and at 3.08 GHz is ?27.4 dB. Its bandwidth, of 33.54 MHz, ranges from 2.38355 GHz to 2.41709 GHz. Simulated and experimental results of the antenna are discussed.     

A 120-W Boost Converter Operation Using a High-Voltage GaN-HEMT

A boost converter with a 940-V/4.4 A GaN-HEMT as the main switching device was demonstrated to show the possibility of using high-voltage GaN-HEMTs in power electronic applications. The demonstrated circuit achieved an output power of 122 W and a power efficiency of 94.2% under a drain peak voltage as high as 350 V and a switching frequency of 1 MHz. The dual field-plate structure realized high-voltage switching operation with high power efficiency as dynamic on-resistance was suppressed by an increase of the current collapse phenomena.     

Microwave power performance comparison between single and dualdoped-channel design in AlGaAs/InGaAs HFETs

Single and dual doped-channel AlGaAs/InGaAs FETs (DCFETs) were fabricated, characterized, and compared with each other in terms of dc, rf, and power performance. The dual doped channel design provides a higher current density, and a better linear operation range over a wide gate bias range and frequency. A 1 μm-long gate dual-DCFET operated at 1.9 GHz demonstrates a power-added efficiency of 51.5%, a gain of 19 dB, and an output power density of 305 mW/mm at 2.5 V. This performance suggests that dual doped-channel design is more suitable for linear and high power microwave device applications     

Dual band aperture coupled antenna using spur line

A new dual band microstrip antenna is presented. A spur line is embedded in the nonradiating edges of the patch to obtain dual band operation at two separate frequencies with good radiation characteristics. Very good agreement between the simulation and the measurements is obtained     

Dual-frequency electronically tunable CPW-fed CPS dipole antenna

A CPW-fed coplanar strip (CPS) dipole antenna is presented which operates at dual frequencies. A wideband CPW-to-CPS balun was designed and used. Dual-frequency operation of the CPS dipole antenna was realised by introducing a small gap in the length of the dipole. Varactors were integrated with CPS dipoles to form integrated antennas. The CPS dipole antenna was electronically tuned by varying the varactor bias voltages. Measurements showed good results of dual operating frequencies, frequency range, and antenna pattern     

A Switchable Microstrip Patch Antenna for Dual Frequency Operation

A novel design for equilateral‐triangular microstrip antennas with switchable resonant frequency is proposed. For dual‐frequency operation, the proposed design is achieved by loading a pair of slits in the triangular patch, and two PIN diodes are utilized to switch the slits on or off. By increasing the length of the slits, the lower resonant frequency can be varied in the range from 1.22 GHz to 1.72 GHz whereas the upper resonant frequency remains unchanged.