Ayman S. Al-Zayed

SEVEN PORTS POWER DIVIDER WITH VARIOUS POWER DIVISION RATIOS

A seven ports network is proposed to act as a six-way power divider/combiner. The proposed network structure consists of a set of ‚=4 planar transmission lines at the design frequency and does not require any isolating resistor. The power divider is capable of providing various power ratios by judicious choice of the transmission lines characteristic impedances. Design equations are derived for arbitrary power ratios. Simulation results obtained from the ADS software proved the possibility of achieving preset power ratios with fairly linear phase response over a certain bandwidth. The latter depends on the chosen power ratios. Measured results of manufactured power dividers agree well with simulations and theory.

Aperture-Sparsity Analysis of Ultrawideband Two-Dimensional Focused Array

We investigate the effects of aperture sparsity on the focusing performance and the angular-resolution capability of a two-dimensional focused array antenna excited by ultrawideband (UWB) impulse waveforms. The UWB-focusing array is characterized by a planar square aperture and a design parameter referred to as array spatial bandwidth. Spatial bandwidth is a function of the number of array elements, inter-element spacing, and frequency bandwidth. Performance analysis is carried out by generating computer plots of three-dimensional and two-dimensional antenna patterns for different values of array spatial bandwidth that hold for large aperture sparsity and large aperture density. The antenna patterns are peak-amplitude pattern, peak-power pattern, and energy pattern, whose narrow beamwidth and low sidelobe level are robust against aperture sparsity that may be caused by removed or failed elements. The half-power beamwidth (HPBW) of the antenna patterns, the focal distance, and the far-field distance of the UWB-focused array are expressed in terms of array spatial bandwidth. Computer simulation results show that UWB-focused-array beamforming based on impulse waveforms achieves efficient focusing of the radiation energy in the radiation-near-field region and beyond, and yields improvement in focusing performance and angular resolution for increased values of array spatial bandwidth. Such practical advantages are achieved without encountering grating lobes, large sidelobe level, or distortion of the radiation beam pattern that often limit the performance of the conventional narrowband phased array antennas.

EM FULL-WAVE ANALYSIS AND TESTING OF NOVEL QUASI-ELLIPTIC MICROSTRIP FILTERS FOR ULTRA NARROWBAND FILTER DESIGN

A new class of microstrip filter structures are designed, optimized, simulated and measured for ultra-narrowband performance essential to the wireless industry applications. More accurate model of the coupling coefficient is outlined and tested for narrowband filter design. Two sample filters are fabricated and measured to verify the simulations and prove the concept. The idea behind the new designs is based on minimizing the parasitic couplings within the resonators and the inter-resonator coupling of adjacent resonators. A reduction of the overall coupling coefficient is achieved even with less resonator separation which is a major issue for compactness of such filters. The best new designs showed a simulated fractional bandwidth (FBW ) of 0.05% and 0.02% with separations of S = 0.63 mm and S = 0.45 mm, respectively. The measured filters tend to have even narrower FBW than the simulated, though its insertion loss deteriorates, possibly due to mismatch at the interface with external circuitry and poor shielding effect of the test platform. The investigated 2-pole filters are accommodated on a compact area of a nearly 0.6 cm2. An improvement of tens of times of order in narrowband performance is achieved compared to reported similar configuration filters and materials. A sharp selectivity and quasi-elliptic response are also demonstrated with good agreement in both simulations and measurements. In all filters, however, the study shows that the narrower the FBW , the larger the insertion loss (IL) and the worse the return loss (RL). This is confirmed by measurements.

Five Ports Power Divider Designs with Controllable Power Division and Switching Capabilities

Two new 5-port power divider designs capable of controlling the power division ratios between the output ports are proposed. In the first design, the input power is switchable between two pairs of the output ports. This is implemented by terminating the dividers’ two open-ended stubs with varactor diodes. In the second design, the power division is controlled by a single varactor diode that terminates one of the dividers two open-ended stubs. With judicious choice of dc bias voltage, it is possible to realize equal as well as unequal power division ratios between the four output ports. High power division ratios was achieved without the necessity of involving transmission lines with high impedances. It is demonstrated that this design is capable of generating amplitude modulated signals. Simulation and measurement results are presented for the designs to show their power division and matching performance.

Performance of feed-forward linearizers of power amplifiers in OFDM systems under complex gain errors

Adaptive feed-forward FF linearization schemes of power amplifiers provide high distortion cancelation and adjacent channel power ratio ACPR reduction. However, FF schemes are very sensitive to imbalances in the circuit parameters used to achieve signal cancelation. In this paper, an FF linearization circuit is analyzed using the orthogonalization of the nonlinear model and considering the effects of complex gain errors in the signal and distortion cancelation loops on the overall performance of the FF linearizer. The analysis enables the effective signal-to-distortion ratio SDR and ACPR to be estimated from FF circuit model. It is shown that complex gain errors in the distortion cancelation loop have a more significant effect on in-band distortion than out-of-band distortion, which means that the design of FF linearizers based on ACPR improvement is not optimal. Copyright

The design of an integrated diplexer-power divider based on dual-band impedance transformers and a five-port power-divider

In this paper, a novel method to design diplexers with integrated power division capabilities is presented. The diplexer is developed from a five-port power divider that is capable of providing power division ratios of 1:1:0:0 and 0:0:1:1 between its outputs. The development does not involve filter design, and is implemented using dual-band quarter-wavelength lines, dual-band dual-susceptance stubs, and dual-band impedance buffers. The proposed method is applied to design a microstrip diplexer that operates at 1 and 2.5 GHz. Simulation results are presented to verify the validity of the proposed design method.

Tunable H-Shaped Microstrip Antenna with Dual Feeding

The design of a frequency reconfigurable dual-band H-shaped microstrip antenna fed by two coaxial probes is presented. Each probe excites one of the two fundamental modes of the antenna which are linearly polarized and orthogonal to each other. The antenna is symmetrically loaded with four varactor diodes to simultaneously tune these two modes. Simulation results show that the tunable range of the first mode is between 1.69 and 2.19 GHz (1.3 : 1 tuning ratio), whereas it is between 1.94 and 2.72 GHz (1.4 : 1 tuning ratio) for the second mode. In the range between 1.94 and 2.19 GHz, the radiation of the proposed antenna can be switched between two orthogonal linear polarizations by a simple adjustment to the capacitance of the varactor diodes. The proposed antenna achieves a good performance in terms of port-to-port isolation, directivity, and cross-polarization.

Compact composite right /left -handed stripped impedance resonator band pass filter designs

One of the popular implementations of RF in microwave communication system is the bandpass filter. In this paper Three band pass filter designs are introduced based on composite right/left handed stepped impedance resonator (CRLH SIR) where the pass band is controlled by changing the dimensions of one unit cell which consists of capacitance interdigits and shunt inductance.