Yangfan Liu

Printed L-probe antenna on multi-layered PCB

A printed L-probe antenna fabricated on a multi-layered printed-circuit-board (PCB) with a very wide operating band is proposed. This antenna is a four-layered structure, consisting of a circuitry layer, ground layer, probe layer, and patch layer. The printed part of the L-probe provides extra degrees of freedom for tuning the antenna, achieving a wide operating frequency. A printed L-probe antenna centered at the frequency of 6.5 GHz was designed with a measured impedance bandwidth of 40% with constant radiation patterns across the operating band.

Microstrip-fed wide slot antenna with wide operating bandwidth

A printed wide slot antenna fed by a microstrip line with a square patch within the arc-shaped slot is proposed for wideband application. The impedance bandwidth and radiation characteristics of this antenna are studied and improved by optimizing the slot shape and dimensions, resulting in an antenna with a 120% bandwidth for S/sub 11/ /spl les/ -10 dB and stable radiation patterns across the whole band.

The MEI–MoM method for solving conducting concave scattering

A hybrid numerical approach, the MEI-MoM method, which combines the measured equation of invariance method (MEI) combined with the method of moments (MoM), is presented for solving the problem of deep concave conducting scattering. Although the MEI as a fast computation method has been demonstrated to be robust, it still has problem when used in scatterers with deep concave parts. Examples of both TM and TE plane wave scattering from a deep concave conducting scatterer show that results of the MEI-MoM method are in excellent agreement with those of using the MoM alone. It is observed, however, the inaccuracy of the MEI method is only present within the concave region, so, an application afterwards of the MoM limited to the concave region should correct the result and it does.

Application of CMRC in antenna switch

For time division duplex (TDD) systems, a PIN-diode transmitting/receiving (TX/RX) switch is widely used for switching between the transmit and receive section to the antenna. There are two commonly used PIN diode antenna switches. The dual-biased switch is compact but with a relatively large control current consumption. The single-biased switch only needs half the current consumption, but needs a section of /spl lambda//4 microstrip transmission line and its applications are limited due to this size constraint. As power saving is a very important feature for portable communication equipment, the single-biased antenna switch is attractive if its size can be reduced. The compact microstrip resonant cell (CMRC) is a kind of microstrip structure with some suitable patterns on the conductor strip. To achieve a size reduction of the switch, we propose a CMRC with a spiral pattern. The CMRC with spiral pattern was employed to build a single-biased PIN diode antenna switch. With the CMRC as the /spl lambda//4 impedance transformer, the switch is not only reduced to a practical size, but the rejection of second harmonic radiation is greatly improved.

A 50-mW/ch 2.5-gb/s/ch data recovery circuit for the SFI-5 interface with digital eye-tracking

Typical frequency doublers achieve high conversion gain by reflecting back the 2nd harmonic to the input port of the active device through a quarter-wave open-circuited stub. In this paper, a S-band frequency doubler with a 12 dB conversion gain outperforms the conventional design by 5 dB, after replacing the conventional stub with a Compact Microstrip Resonant Cell (CMRC). The CMRC serves as suitable terminations for both the 2nd and 3rd harmonics to enhance the desired output power of the 2nd harmonic, while appearing as a good pass-band for the fundamental frequency.

Numerical computation of scattering by very large cylinders

Scattering by a conducting circular cylinder is a classical problem solvable by separation of variables. When the radius of the cylinder is very large, computation of the summation becomes very time consuming. Classically, the harmonic series may be converted into an alternative series by Watsons transformation. Practically, high frequency scatterings are approximately solved using optical techniques such an geometric optics, physical optics, or geometric theory of diffraction. Direct numerical solutions of electromagnetic scattering in the optical frequency range have never been attempted because the effort would be too expensive and there is no guarantee that the results will be reliable after an astronomical number of arithmetical operations. The measured equation of invariance (MEI) may have just reversed the situation. The advantage of MEI is its ability to terminate finite difference/element meshes very close to the scatterer surface. We demonstrate that the MEI coefficients at high frequency can be obtained by extrapolation of those at low frequencies. So, using the MEI with its coefficient extrapolation the number of arithmetical operations can be drastically reduced and the direct numerical method becomes feasible in the optical frequency range.

Multi-band printed dipole antenna using CRC structure

This paper presents a new approach to realizing multi-band antennas using a single printed dipole incorporating compact resonant cell (CRC) structures. A triple-band antenna that operates at 900 MHz, 2.4 GHz and 5.2 GHz was constructed to illustrate the design methodology. The overall length of the triple-band antenna is 107 mm, which is shorter than the conventional single frequency design of 130 mm at 900 MHz.

A PVM based parallel sparse matrix equation solver to speed up computation of MEI method

The conventional method of moments is capable of solving wave scattering problems of circumferential dimension of 100 wavelengths. Using the MEI (measured equation of invariance) method the problem of a cylinder of 10,000 wavelengths is within the storage capacity of a personal computer (PC). The MEI method requires the generation of a large sparse matrix for the boundary equations. The MEI matrix coefficients are computed from numerical integrations of the metrons. Interpolation and extrapolation techniques can be employed to save integration time. This means that the solution of the sparse matrix equation of the MEI method is the bottleneck of computation. Since the MEI equation matrix is a sparse matrix with nonzero diagonal elements and very small number of nondiagonal elements at the upper right and lower left corners for 2 dimensional problems, a matrix decomposition algorithm derived by Chen (1973) can be employed for the purpose of decomposition and parallel computing (using parallel virtual machine-PVM).

The MEI-MoM method for solving conducting concave scattering

A hybrid numerical approach, the MEI-MoM method, which combines the measured equation of invariance method (MEI) combined with the method of moments (MoM), is presented for solving the problem of deep concave conducting scattering. Although the MEI as a fast computation method has been demonstrated to be robust, it still has problem when used in scatterers with deep concave parts. Examples of both TM and TE plane wave scattering from a deep concave conducting scatterer show that results of the MEI-MoM method are in excellent agreement with those of using the MoM alone. It is observed, however, the inaccuracy of the MEI method is only present within the concave region, so, an application afterwards of the MoM limited to the concave region should correct the result and it does.

MEI solution of 2D scattering of a cylindrical-parabolic reflector

The measured equation of invariance (MEI) method was introduced by Mei et al. (see AP-S Int. Symp. Digest, 1992 and IEEE Trans. on Antennas and Propagation, vol.42, no.3., p.320-8, 1994) as a mesh truncation condition for the finite difference (FD) method, which allows the termination of the mesh very close to the scatterer surface. This approach has been proved to be more robust than the absorbing or radiation boundary condition applied close to the scatterer surface and, in contrast to the hybrid FE-BEM method, the interrelation between the field points is sparse. Thus, it has the advantages of the two popular methods: the sparse matrix in the FD method and a small number of unknowns in the moment method. Based on these advantages, the MEI method is used to deal with the scattering problem of an infinite long perfectly-conducting cylindrical parabolic reflector. Numerical results of the induced current density on the parabolic reflector with different geometric parameters are obtained.