Offset Slot Research Articles

Circularly Polarized Electromagnetic Band Gap Patch-Slot Antenna with Circular Offset Slot

Circularly Polarized Electromagnetic Band Gap Patch-Slot Antenna with Circular Offset Slot

Mode excitation in the microstrip slot‐coupled three‐layer hemispherical dielectric resonator antenna

In this study, a microstrip slot-coupled multilayer dielectric resonator antenna (DRA) structure is rigorously analysed from the modal perspective, taking into account all layers. The choice of layer permittivities of the multilayer structure to reduce the Q-factor and obtain optimum bandwidth performance of the antenna is outlined. Next, the mechanism of bandwidth enhancement for the centred and offset slots is examined taking into account the excited modes in the structure. It is found that while the centred slot couples to one DRA mode, an offset slot can couple to multiple DRA modes together with the slot mode. Thereafter, the excitation efficiency of modes in the multilayer DRA structure is highlighted to thoroughly characterise the modal contribution in the coupling behaviour for the centred and offset-slots.

Room-Temperature Oscillation of Resonant Tunneling Diodes close to 2 THz and Their Functions for Various Applications

Compact and coherent source is a key component for various applications of the terahertz (THz) wave. We report on our recent results of THz oscillators using resonant tunneling diodes (RTDs). To achieve high-frequency oscillation, the electron delay time of RTD was reduced with a narrow quantum well and an optimized collector spacer thickness. Conduction loss at the air bridge connecting RTD and slot antenna, which works as a resonator and a radiator, was also reduced. By these structures, a fundamental oscillation up to 1.92 THz was obtained at room temperature. Theoretical calculation shows that an oscillation over 2 THz is further expected by improved structures of RTD and antenna. Using the offset slot antenna and two-element array configuration, high output power of 0.61 mW was obtained at 620 GHz. A direct intensity modulation of RTD oscillators up to 30 GHz, which is useful for high-speed wireless data transmission, was demonstrated. By the integration of a varactor diode, wide frequency sweep of 580–700 GHz in a single device and 580–900 GHz in a four-element array were also demonstrated. This result expands possible applications of RTD oscillators.

Effects of boundary-layer separation controllers on a desktop fume hood

ABSTRACTA desktop fume hood installed with an innovative design of flow boundary-layer separation controllers on the leading edges of the side plates, work surface, and corners was developed and characterized for its flow and containment leakage characteristics. The geometric features of the developed desktop fume hood included a rearward offset suction slot, two side plates, two side-plate boundary-layer separation controllers on the leading edges of the side plates, a slanted surface on the leading edge of the work surface, and two small triangular plates on the upper left and right corners of the hood face. The flow characteristics were examined using the laser-assisted smoke flow visualization technique. The containment leakages were measured by the tracer gas (sulphur hexafluoride) detection method on the hood face plane with a mannequin installed in front of the hood. The results of flow visualization showed that the smoke dispersions induced by the boundary-layer separations on the leading edges of the side plates and work surface, as well as the three-dimensional complex flows on the upper-left and -right corners of the hood face, were effectively alleviated by the boundary-layer separation controllers. The results of the tracer gas detection method with a mannequin standing in front of the hood showed that the leakage levels were negligibly small (≤0.003 ppm) at low face velocities (≥0.19 m/s).

A 79-GHz Resonant Laminated Waveguide Slotted Array Antenna Using Novel Shaped Slots in LTCC

This letter presents a laminated waveguide (LWG)-based slotted array antenna in LTCC. The introduced novel slot shape derived from a standard longitudinal offset slot provides a further degree of freedom for the antenna design by bending the outer sections of the slot. Based on the characteristics of a single slot, the design procedure of an antenna array with amplitude tapering at a constant slot offset is presented. As an example, design, realization, and measurement of a 12-element array at 79 GHz with Dolph-Chebyshev power distribution with a sidelobe level of -20 dB are presented.

Compact wideband double-layer half-mode substrate integrated waveguide 90° coupler

Presented are two novel double layer substrate integrated waveguide (SIW)-based couplers, the longitudinal-slots-based broadwall SIW coupler and its corresponding half-mode SIW coupler. Coupling takes place through a set of narrow, offset slots, which feature a flexible design providing a wide coupling dynamic range with wideband characteristics. This technique provides a compact design through both the double layer scheme and the half-mode structure. Isolation and input reflection characteristics better than 15 dB and 13 dB, respectively, are experimentally validated over 24% fractional bandwidth at 12.5 GHz. Measured coupling magnitudes and phases exhibit dispersive characteristics lower than 1 dB, and 8° with respect to the adopted design values, respectively, over the entire frequency band.

Inclined slot coupled hemispherical dielectric resonator antenna

A microstrip line coupled dielectric resonator antenna with an inclined and offset slot in the common ground plane has been analyzed. Excitation of the TE111 mode in this configuration is studied. It is also seen that the slot geometry and offset can be optimized to excite the higher order TM101 mode. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1527–1530, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23414

Efficiency and gain of slot antennas and arrays on thick dielectric substrates for millimeter-wave applications: a unified approach

A unified approach for representing the surface-wave fields and for computing the corresponding radiation efficiencies from arbitrarily shaped slot-type antennas on thick dielectric substrates at millimeter-wave (mm-wave) frequencies is presented. In this approach, two different representations of the surface-wave fields, i.e., the one based on the idea that the surface-wave power can be associated with a substrate radiation pattern and the other based on the cylindrical wave expansion, are linked together in a unified way. The developed theory is then applied for investigating the surface wave characteristics of printed twin offset slots and uniform linear slot arrays. Based on the developed theory, new insight into the mechanism with which surface-wave power is coupled by the slot pair is presented. Subsequently, the optimum number of elements and corresponding interelement spacing for linear, uniformly excited, slot dipole arrays is explored for achieving maximum radiation efficiency and gain. In order to provide guidance on practical mm-wave integrated slot antenna array design, supportive numerical results are presented for Substrates of dielectric constant /spl epsi//sub r/ = 4.0 and /spl epsi//sub r/ = 12.0.

Wide-band PIN diode SPST switch in unilateral asymmetric finline

This paper reports the design and modelling of a wide-band, low insertion loss finline SPST switch using beam lead PIN diodes at the Ka-band. A unilateral asymmetric finline with an offset slot has been used to realize a transmission line with lower impedance to best match the impedance of the diode. Finline tapered transitions have been designed with exponential profiles for minimum reflection coefficient over the band. Wide-band operation, covering the full Ka-band, has been achieved with reactive tuning by varying the diode spacing. Four PIN diodes have been shunt mounted across the unilateral asymmetric finline slot. An insertion loss of 0.9 dB minimum and 1.65 dB maximum over the entire Ka-band and isolation of >25 dB from 26.5 to 35GHz and >20 dB over the complete Kaband has been achieved.

Low-profile dual-frequency circular microstrip antenna for dual ISM bands

A novel dual-frequency design of a singIe-layer, single-feed circular microstrip antenna for dual ISM bands is demonstrated. Due to the embedding of an offset open-ring slot in a circular patch, a novel dual-frequency operation with its two operating modes centred at about frequencies 2.4 and 5.2 GHz has been obtained. The two operating frequencies have similar broadside radiation patterns and same polarisation planes, and small antenna-gain variation. Details of the antenna design and experimental results for the proposed antenna are presented.

Compact dual-frequency circular microstrip antenna with an offset circular slot

This paper presents a new, compact, dual-frequency design of single-feed circular microstrip antennas with an offset circular slot placed close to the patch boundary. It is found that, when the radius of the offset slot is about 0.38–0.62 times the radius of the circular patch, dual-frequency operation can be achieved using a single probe feed. The two operating frequencies have orthogonal polarization planes, and have a low frequency ratio of about 1.15–1.18. The two frequencies can also be much lower than the fundamental resonant frequency of a corresponding simple circular patch antenna without the offset slot. This behavior makes the proposed antenna have a reduced antenna size as compared to a simple circular patch antenna operated at either one of the two frequencies. Details of the antenna design and experimental results are presented. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 254–256, 1999.

Broadwall-to-Broadwall Coupling between two Cross Rectangular Waveguides through an Offset Slot

The problem of coupling through a slot in the broadwall between two rectangular waveguides has been investigated and Method of Moments used to find the co-efficients of the field function. Convergence of solution requires inclusion of thousands of waveguide modes in the numerical solution. Number of basis functions less than 10 usually gives less accurate result in the computation of slot admittance. The resolant length has been found to change noticeably with offsets.

The Effect of Slots on the Buckling and Postbuckling Behavior of Laminated Plates

An experimental study was conducted to evaluate the effect of lateral slots on the buckling response, the postbuckling response, and the failure characteristics of flat rectangular graphite-epoxy plates loaded in compression. The slots did not significantly affect the prebuckling and buckling behavior of the plates. The slots caused local changes in the strain distribution and out-of-plane deformations near the slot. Failure loads and modes were strongly affected by slot location. Centrally located slots did not affect the failure loads or failure modes of the plates. Slots located close to an unloaded edge of a plate reduced the postbuckling strength of the plate and affected the failure mode. For one slightly offset slot location, interaction of out-of-plane deformations with the slot tip was observed to affect the failure mode significantly without affecting the failure load.

The design of small slot arrays

The differences in mutual coupling for a central slot and a peripheral slot cannot be ignored in small arrays if good patterns and impedance are to be obtained. A theory has been developed whereby the length and offset of every slot in the array can be determined, in the presence of mutual coupling, for a specified aperture distribution and impedance match. The theory enlarges on Stevenson's method, and uses a modified form of Booker's relation based on Babinet's principle to treat nonresonant longitudinal shunt slots in the broad wall of a rectangular waveguide. A general relation between slot voltage and mode voltage is developed, and then formulas are derived for the active, self-, and mutual admittances among slots. These formulas result in a design procedure. Analogous treatments of inclined series slots in rectangular guide and of strip-line-fed slots are possible. Comparison between various experiments and the theory is presented. Tests of the theory include the resonant length of a zero offset slot, resonant conductance versus offset and resonant conductance versus frequency for a single slot, and self- and mutual admittances for two staggered slots. The design and performance of a two-by-four longitudinal shunt slot array is also described.

Conductance Data for Offset Series Slots in Stripline (Correspondence)

Conductance Data for Offset Series Slots in Stripline (Correspondence)