Composite right/left-handed transmission line based compact resonant antennas for RF module integration

Several electrically small resonant antennas employing the composite right/left-handed transmission line (CRLH-TL) are presented for integration with portable RF modules. The proposed antenna designs are based on the unique property of anti-parallel phase and group velocity of the CRLH-TL at its fundamental mode. In this mode, the propagation constant increases as the frequency decreases, therefore, a small guided wavelength can be obtained at a lower frequency to provide the small /spl lambda//sub g//2 resonant length used to realize a compact antenna design. Furthermore, the physical size and the operational frequency of the antenna depend on the unit cell size and the equivalent transmission line model parameters of the CRLH-TL, including series inductance, series capacitance, shunt inductance and shunt capacitance. Optimization of these parameters as well as miniaturization techniques of the physical size of unit cell is investigated. A four unit-cell resonant antenna is designed and tested at 1.06 GHz. The length, width and height of the proposed antenna are 1/19/spl lambda//sub 0/, 1/23/spl lambda//sub 0/ and 1/83/spl lambda//sub 0/, respectively. In addition, a compact antenna using a 2-D three by three mushroom like unit cell arrangement is developed at 1.17 GHz, showing that an increased gain of 0.6 dB and higher radiation efficiency can be achieved over the first prototype antenna. The same design is applied in the development of a circularly polarized antenna operating at 2.46 GHz. A 116/spl deg/ beamwidth with axial ratio better than 3 dB is observed. The physical size of the proposed mushroom type small antenna and the circularly polarized antenna is 1/14/spl lambda//sub 0/ by 1/14/spl lambda//sub 0/ by 1/39/spl lambda//sub 0/ and 1/10/spl lambda//sub 0/ by 1/10/spl lambda//sub 0/ by 1/36/spl lambda//sub 0/, respectively.     

Small dual C-slot printed antenna

A novel shorted dual C-slot printed antenna is presented. The antenna consists of two C-shaped slots embedded within the shorted patch antenna to maximise the current path of the antenna. A 10 dB return loss bandwidth of 5.4% has been achieved. The overall dimension of the antenna is 0.11/spl lambda//sub 0//spl times/0.074/spl lambda//sub 0//spl times/0.074/spl lambda//sub 0/ and is suitable for application where limited space is a premium. Importantly, the antenna is easy to develop.     

A novel approach for miniaturization of slot antennas

With the virtual enforcement of the required boundary condition (BC) at the end of a slot antenna, the area occupied by the resonant antenna can be reduced. To achieve the required virtual BC, the two short circuits at the end of the resonant slot are replaced by some reactive BC, including inductive or capacitive loadings. The application of these loads is shown to reduce the size of the resonant slot antenna for a given resonant frequency without imposing any stringent condition on the impedance matching of the antenna. A procedure for designing this class of slot antennas for any arbitrary size is presented. The procedure is based on an equivalent circuit model for the antenna and its feed structure. The corresponding equivalent circuit parameters are extracted using a full-wave forward model in conjunction with a genetic algorithm optimizer. These parameters are employed to find a proper matching network so that a perfect match to a 50 /spl Omega/ line is obtained. For a prototype slot antenna with approximate dimensions of 0.05/spl lambda//sub 0//spl times/0.05/spl lambda//sub 0/ the impedance match is obtained, with a fairly high gain of -3dBi, for a very small ground plane (/spl ap/0.20/spl lambda//sub 0/). Since there are neither polarization nor mismatch losses, the antenna efficiency is limited only by the dielectric and ohmic losses.     

Elliptical planar monopole antenna with extremely wide bandwidth

A planar monopole antenna with an extremely wide bandwidth is introduced, which is composed of an elliptical monopole patch and a trapeziform ground plane, both printed on the same side of a substrate, and is fed by a tapered CPW feeder in the middle of the ground plane. The simulated and experimental results demonstrate that this antenna achieves a ratio impedance bandwidth of 21.6:1 for VSWR/spl les/2, and exhibits a nearly omnidirectional radiation pattern, while its area is only about 0.19/spl lambda//sub l//spl times/0.16/spl lambda//sub l/ where /spl lambda//sub l/ is the wavelength of the lowest operating frequency.     

Design of an efficient miniaturized UHF planar antenna

The design aspects and the measured results of a novel miniaturized planar antenna are described. Such architectural antenna design is of great importance in mobile military communications where low visibility and high mobility are required. Slot radiating elements, having a planar geometry and capable of transmitting vertical polarization when placed nearly horizontal, are appropriate for the applications at hand. Slot antennas also have another useful property, so far as impedance matching is concerned. Basically, slot dipoles can easily be excited by a microstrip line and can be matched to arbitrary line impedances simply by moving the feed point along the slot. Antenna miniaturization can be achieved by using a high permittivity or permeability substrate and superstrate materials and/or using an appropriate antenna topology. We demonstrate miniaturization by designing an appropriate geometry for a resonant narrow slot antenna. A very efficient radiating element that occupies an area as small as 0.12/spl lambda//sub 0//spl times/0.12/spl lambda//sub 0/ is designed and tested. Simulation results, as well as the measured input impedance and radiation patterns of this antenna, are presented. This structure shows a measured gain of 0.5 dBi on FR4 substrate, which has a loss-tangent of the order of 0.01. Also, the effect of finite ground plane size on gain and resonant frequency is investigated experimentally.     

A cavity-backed rectangular aperture antenna with application to a tilted fan beam array antenna

A rectangular aperture of A/sub x//spl times/A/sub y/, cut in the top conducting plate of a triplate transmission line and backed by a cavity, radiates a tilted beam off the direction normal to the aperture. The mechanism of the radiation is explained using the Poynting vector distribution above the aperture and the phase distribution of the electric field over the aperture. The tilt angle is calculated as a function of side length A/sub x/ for a representative value of A/sub y/=18 mm=0.747/spl lambda//sub 12.45/, where /spl lambda//sub 12.45/ is the wavelength at a test frequency of 12.45 GHz. A tilted beam of approximately 27/spl deg/ is realized at A/sub x//A/sub y/=8/9 with a gain of approximately 8 dB. Using this value of A/sub x//A/sub y/, an array antenna composed of rectangular cavity-backed aperture elements is investigated. The array forms a tilted fan beam without phase shifters. The frequency responses of the gain and input impedance are discussed.     

2 GHz electromagnetic crystal reflector antenna

The radiation pattern of a monopole antenna with a small electromagnetic crystal (EMXT) reflector was investigated. High frequency structure simulations predict a considerable amount of near-field shielding with undisturbed antenna impedance matching when a perfect magnetic conductor reflector is positioned near the monopole. The pattern distortion created by the reflector gradually decreases, reaching a minimum in the far field. Experimental results show the monopole with an EMXT reflector, /spl lambda//sub 0//4/spl times//spl lambda//sub 0//2 in size, produces a radiation pattern with a front-to-back ratio of 10.8 and 5.7 dB in the near and far fields, respectively.     

Multilayer spatial angular filter with airgap tuners to suppress grating lobes of 4/spl times/1 array antenna

A multilayer spatial angular filter with airgap tuners to suppress the grating lobes of a 4/spl times/1 array antenna is proposed. By using the airgap tuner, a commercial standard substrate can be chosen for the filter, to achieve its resonance condition, instead of /spl lambda//sub g//4 substrate. The measured beam patterns of the 4/spl times/1 array with the filter show that the grating and sidelobes are effectively diminished by 15 to 30 dB in the region of interest.     

Package-level integrated antennas based on LTCC technology

We propose a novel package topology integrating multilayer miniaturized antennas. Such a functional package is suitable for the design of a system-on-chip device, or of system-on-package applications. A stacked patch antenna is designed and integrated in a package using a low temperature co-fired ceramic process. The overall size of the package is 10.3/spl times/10.3/spl times/1.3 mm/sup 3/, and this package contains an 8.3/spl times/8.3/spl times/0.7 mm/sup 3/ internal space for the integration of chip-scale packaged components. The package is mounted on a 20/spl times/20 mm/sup 2/ ground plane to miniaturize the volume of the system. The antenna is designed to have two neighboring resonant frequencies at 5.264 and 5.355 GHz, resulting in a 140 MHz impedance bandwidth. However, the measured resonant frequencies occur at slightly higher frequencies due to manufacturing tolerances. Radiation patterns are similar to a conventional patch antenna. In addition, various parasitic effects rooted in the package size, ground size, antenna height, SMA connector, via misalignment, and the number of via holes and their locations are fully investigated.     

RF HBT oscillators with low-phase noise and high-power performance utilizing a (/spl lambda//4/spl plusmn//spl delta/) open-stubs resonator

This paper presents a new type of transmission-line resonator and its application to RF (microwave and millimeter-wave) heterojunction bipolar transistor (HBT) oscillators. The resonator is a parallel combination of two open stubs having length of /spl lambda//4/spl plusmn//spl delta/(/spl delta//spl Lt//spl lambda/), where /spl lambda/ is a wavelength at a resonant frequency. The most important feature of this resonator is that the coupling coefficient (/spl beta//sub C/) can be controlled by changing /spl delta/ while maintaining unloaded Q-factor (Q/sub u/) constant. Choosing a small value of /spl delta/ allows us to reduce /spl beta//sub C/ or equivalently to increase loaded Q-factor (Q/sub L/). Since coupling elements such as capacitors or electromagnetic gaps are not needed, /spl beta//sub C/ and Q/sub L/ can be precisely controlled based on mature lithography technology. This feature of the resonator proves useful in reducing phase noise and also in enhancing output power of microwave oscillators. The proposed resonator is applied to 18-GHz and 38-GHz HBT oscillators, leading to the phase noise of -96-dBc/Hz at 100-kHz offset with 10.3-dBm output power (18-GHz oscillator) and -104-dBc/Hz at 1-MHz offset with 11.9 dBm (38-GHz oscillator). These performances are comparable to or better than state-of-the-art values for GaAs- or InP-based planar-circuit fundamental-frequency oscillators at the same frequency bands.     

Integrated high-/spl kappa/ (/spl kappa/ /spl sim/19) MIM capacitor with Cu/low-/spl kappa/ interconnects for RF application

We demonstrate a high-performance metal-high /spl kappa/ insulator-metal (MIM) capacitor integrated with a Cu/low-/spl kappa/ backend interconnection. The high-/spl kappa/ used was laminated HfO/sub 2/-Al/sub 2/O/sub 3/ with effective /spl kappa/ /spl sim/19 and the low-/spl kappa/ dielectric used was Black Diamond with /spl kappa/ /spl sim/2.9. The MIM capacitor (/spl sim/13.4 fF//spl mu/m/sup 2/) achieved a Q-factor /spl sim/53 at 2.5 GHz and 11.7 pF. The resonant frequency f/sub r/ was 21% higher in comparison to an equivalently integrated Si/sub 3/N/sub 4/-MIM capacitor (/spl sim/0.93 fF//spl mu/m/sup 2/) having similar capacitance 11.2 pF. The impacts of high-/spl kappa/ insulator and low-/spl kappa/ interconnect dielectric on the mechanism for resonant frequency improvement are distinguished using equivalent circuit analysis. This letter suggests that integrated high-/spl kappa/ MIM could be a promising alternative capacitor structure for future high-performance RF applications.     

Printed figure-of-eight wire antenna for circular polarization

A new printed wire antenna with circular polarization properties is presented. The geometry of the printed wire which takes the form of a figure-of-eight has a total length of 1.3/spl lambda//sub o/ and serves as a nonresonant traveling-wave antenna. It is shown that a 3-dB axial ratio bandwidth of 15% can be achieved. The half-power and 3-dB axial ratio beamwidth is approximately /spl plusmn/45/spl deg/, while its gain is of the order of 6.5 dB.     

Wideband simple cylindrical dielectric resonator antennas

Bandwidths of the coaxial fed and aperture coupled cylindrical dielectric resonator antennas (DRAs) with broadside radiation patterns are enhanced by exciting the HEM/sub 11/spl Delta// (1相似文献   

Exact thresholds and optimal codes for the binary-symmetric channel and Gallager's decoding algorithm A

We show that for the case of the binary-symmetric channel and Gallager's decoding algorithm A the threshold can, in many cases, be determined analytically. More precisely, we show that the threshold is always upper-bounded by the minimum of (1-/spl lambda//sub 2//spl rho/'(1))/(/spl lambda/'(1)/spl rho/'(1)-/spl lambda//sub 2//spl rho/'(1)) and the smallest positive real root /spl tau/ of a specific polynomial p(x) and we observe that for most cases this bound is tight, i.e., it determines the threshold exactly. We also present optimal degree distributions for a large range of rates. In the case of rate one-half codes, for example, the threshold x/sub 0//sup */ of the optimal degree distribution is given by x/sup *//sub 0//spl sim/0.0513663. Finally, we outline how thresholds of more complicated decoders might be determined analytically.     

Wideband small patch antenna

A small patch antenna fed by a coaxial probe with a wideband characteristic is presented. By employing dual shorting pins and cutting a slot in the patch, the size of the patch antenna is reduced while its impedance bandwidth is enhanced. The resonant frequency can be reduced by /spl sim/75% when compared with the resonance edge of a conventional patch antenna. The antenna has an impedance bandwidth of 21.5% (SWR<=2) and maximum gain of 2.2 dBi.     

Impedance, bandwidth, and Q of antennas

To address the need for fundamental universally valid definitions of exact bandwidth and quality factor (Q) of tuned antennas, as well as the need for efficient accurate approximate formulas for computing this bandwidth and Q, exact and approximate expressions are found for the bandwidth and Q of a general single-feed (one-port) lossy or lossless linear antenna tuned to resonance or antiresonance. The approximate expression derived for the exact bandwidth of a tuned antenna differs from previous approximate expressions in that it is inversely proportional to the magnitude |Z'/sub 0/(/spl omega//sub 0/)| of the frequency derivative of the input impedance and, for not too large a bandwidth, it is nearly equal to the exact bandwidth of the tuned antenna at every frequency /spl omega//sub 0/, that is, throughout antiresonant as well as resonant frequency bands. It is also shown that an appropriately defined exact Q of a tuned lossy or lossless antenna is approximately proportional to |Z'/sub 0/(/spl omega//sub 0/)| and thus this Q is approximately inversely proportional to the bandwidth (for not too large a bandwidth) of a simply tuned antenna at all frequencies. The exact Q of a tuned antenna is defined in terms of average internal energies that emerge naturally from Maxwell's equations applied to the tuned antenna. These internal energies, which are similar but not identical to previously defined quality-factor energies, and the associated Q are proven to increase without bound as the size of an antenna is decreased. Numerical solutions to thin straight-wire and wire-loop lossy and lossless antennas, as well as to a Yagi antenna and a straight-wire antenna embedded in a lossy dispersive dielectric, confirm the accuracy of the approximate expressions and the inverse relationship between the defined bandwidth and the defined Q over frequency ranges that cover several resonant and antiresonant frequency bands.     

Studies of CPW-fed equilateral triangular-ring slot antennas and triangular-ring slot coupled patch antennas

Designs of coplanar waveguide (CPW)-fed equilateral triangular-ring slot antennas with tuning-stub and triangular-ring slot coupled patch antennas are proposed and experimentally investigated. The impedance matching of the resonant frequency can be obtained only by adjusting the tuning-stub length for the proposed triangular-ring slot antenna with tuning-stub. For the design of ring-slot coupled patch antenna, slightly changing the patch size causes the tunable frequency-ratio f/sub 2//f/sub 1/ between the first two operating frequencies to fall in the range of about 1.1-1.42. Details of the proposed designs are investigated by experimental as well as theoretical studies.     

Design of square-ring microstrip antenna for circular polarisation

The design of a square-ring microstrip antenna with circular polarisation (CP) is presented. To compact the antenna size and overcome the high impedance problem, the CP antenna is excited by a coupling strip located inside the square-ring patch. Several prototypes of the square-ring CP antennas with various substrate thickness (0.013-0.09/spl lambda//sub 0/) have been constructed and studied experimentally, and their coupling-strip designs and CP performance are described.     

CLIP antenna for wireless bluetooth applications

In this paper, a novel design for a coplanar waveguide antenna is developed that consists of two U-shaped slots. The antenna is named CLIP. The antenna was designed for a central frequency of 2.4 GHz, with an input impedance of 50 /spl Omega/. The antenna dimensions represent a 72% size reduction compared to a conventional microstrip rectangular-patch antenna. The measured antenna bandwidth was about 11%, while its gain was about 17 dB. These values are fairly acceptable in all wireless communication systems. The antenna configuration has a bidirectional radiation pattern, while a unidirectional radiation pattern was achieved by using a /spl lambda//sub 0//4 reflector with a metal plate. A 2/spl times/2 multi-element sub array was implemented to widen the application area. The mutual coupling between adjacent elements was low. Orthogonal-plane coupling between adjacent elements was introduced to increase the reduction in the mutual coupling. The mutual coupling level was reduced to less than -23 dB in all coupling planes. The CLIP antenna element and arrays were fabricated. Experimental measurements showed very good performance, which agreed well with simulation results.