Jonathan Bagby

Identification of propagation regimes on integrated microstrip transmission lines

There has been a resurgence of interest in the propagation characteristics of open integrated microstrip transmission lines. This is due in part to the discovery of diverse propagation regimes for higher-order modes on open lines. In contrast to the dominant EH/sub 0/ mode, three distinct propagation regimes exist for higher-order modes on microstrip transmission lines. In this paper, a rigorous spectral-domain integral equation formulation is used to analyze propagation in all three regimes. This formulation provides a clear physical picture of the different propagation regimes based on the mathematical location of poles and branch points in the complex spectral-variable plane. As an illustration, the formulation is applied to the case of an isolated uniform microstrip transmission line. The integral equation is discretized via the method of moments, and entire-domain basis functions incorporating suitable edge behavior are utilized to provide convergence with relatively few terms. The results obtained are compared to the results of other workers, and good agreement is observed. >

Entire-domain basis MOM analysis of coupled microstrip transmission lines

A full-wave spectral-domain integral equation formulation is used to analyze coupled open-boundary microstrip transmission lines. A general rigorous formulation is specialized to the case of two identical uniform lines and a method of moments (MOM) solution is implemented. In contrast with earlier subdomain basis MOM solutions, entire-domain basis functions which incorporate appropriate edge conditions for transverse and longitudinal current components are utilized. This allows closed-form evaluation of relevant spatial integrals and results in improved accuracy using far fewer terms. Numerical results in the form of propagation constants and current distributions are presented for the dominant and first two higher-order coupled modes, and compare favorably to results of other techniques. >

Resonator Type for the Creation of a Potentially Reconfigurable Filtering Band in a UWB Antenna

In this letter, a novel frequency-reconfigurable monopole antenna with several switchable states including an ultra-wideband (UWB) state, filtering narrowband states, and a tunable filtering band state is presented. The antenna, which supports most applicable overlook narrowband frequencies between the 2-6 GHz, can be used in multiradio wireless systems. Moreover, the proposed antenna, which can avoid UWB interference and has narrowband functionality, has good potential for use in cognitive radio.

Analysis of an adjustable modified Kaiser weighting function and its application to linear array antenna beamforming

In this paper we propose a novel class of adjustable modified Kaiser weighting functions based on minimizing the sidelobes by definition of a nonconvex problem. The proposed weighting function is rooted in the same way as the Kaiser weighting function, but it has a lower first sidelobe and equiripple form other sidelobes by determined level. Undesired sidelobes minimized by inserting a parameter for extending free degrees. The sidelobes of solving optimization problem will be compare by equal mainlobes. Simulation results show that the proposed weighting function performs better sidelobe ripple ratio than the Kaiser weighting function for the same weighting function length and normalized mainlobe width. The results show that the linear array coefficients designed by the proposed weighting function provide better far end stopband attenuation than the filters designed by the Kaiser weighting function.

MUTUAL COUPLING REDUCTION OF CLOSELY SPACED MIMO ANTENNA BASED ON ELECTRIC RESONATOR

A new technique for mutual coupling reduction, based on the application of electric resonator, is presented in this paper. In this method, first a custom-designed unitcell is presented that provides a proper S12 response for the mutual coupling reduction, and then, this unitcell is used in a two-element array of wideband dipoles. According to the results, this unitcell provides a maximum reduction of 15 dB in the frequency response of the antenna array while does not have a considerable effect on the reflection coefficient and radiation pattern of the antenna. To verify the results, the antenna is fabricated and measured, and there is a very good agreement between the simulation and measurement.

Monopole antenna with tunable stop-band function

In this paper a monopole antenna with a coplanar waveguide (CPW) resonant cell (CCRC) is proposed which can be used for ultra-wideband (3 - 10.3 GHz) applications, with a band-notch in the 5.4 - 6.1 GHz range. The notch frequency can be controlled by the signal applied to a varactor diode embedded in the antenna. The performance in the stop-band is verified by transmission parameter measurements, in addition to numerical antenna simulation.

Reconfigurable monopole antenna for filtered multi-radio wireless application

In this paper, a frequency reconfigurable antenna using a PIN diode and variable bandpass filtering using varactor diode and coplanar waveguide resonant cell has been proposed. By means of two PIN diodes and the associated dc bias network, the proposed antenna has the ability to alternatively switch the operating filtering frequency. The measured results agree with simulated results, and further verify the design concept.

Flexible exponential weighting function toward side lobe suppression in antenna arrays

In this paper a different class of flexible exponential weighting functions is proposed based on minimizing the sidelobes by definition of a nonconvex problem. The proposed weighting function is fixed by similar way as the Kaiser weighting function, nevertheless it has a lower sidelobe and other sidelobes have equiripple form by determined level. Undesired sidelobes suppression (SLS) by introducing a parameter for increasing free degree. The optimized suppressed sidelobes will be compered by equal mainlobes. Then, a rectangular antenna array is designed for experimental verification. Simulation results besides the experimental tests show that the proposed weighting function performs better SLS than the proposed weighting function for the equal weighting function normalized mainlobe width and length.

Design and development of linear array of rectangular aperture coupled microstrip antennas with application in beamforming

In this letter, we propose a Broadband stacked, low-cost low profile, based on an aperture coupled feeding with linear array. Paper presents the experimental investigations carried out for obtaining X-band operation of rectangular microstrip antenna by using aperture coupled feeding technique. Frequency range set at approximately 8.6 to 10.9 GHz, by incorporating frequency range of the antenna resonates for single wideband with an impedance bandwidth of 23%. The enhancement of impedance bandwidth and gain does not disturb the humor of broadside radiation characteristics. The design concepts of antennas are presented and experimental results are discussed. This letter describes the design, operation, and realization of the beamforming array antenna.

Adaptive antenna array beamforming using variable-step-size normalized least mean square

In this article novel Beamforming method is proposed for array antenna to control electrically and with software the beam pattern, reducing the noise, Orientation the pattern, signal superposition, Antenna array element selection and from hardware side in array antenna useful for power management. The proposed VSS-NLMS algorithm is used to weaken the undesirable interference. This algorithm utilizes continuous adaptation. The weights are attuned that the final weight vector to the most satisfied result. The gradient vector can be achieved by iterative beamforming algorithm from the available data. This algorithm is compared with LMS, NTMS, VSS-NLMS algorithms, it is determined that the VSS-NTMS algorithm is better performance to other algorithms. The proposed algorithm provides better convergence features than the LMS, NTMS, VSS-NTMS algorithms, because it can reduce the growth of the noise by dividing the step size parameter by input vector power. So finally, we can say that the VSS-NLMS is more useful for mobile communication system.