Khelifa Hettak

A class of novel uniplanar series resonators and their implementation in original applications

A class of novel millimetric uniplanar series resonators are presented, which can be used in monolithic and hybrid uniplanar microwave integrated circuits (MICs). The proposed structures are able to demonstrate low radiation and compactness characteristics, which are attractive for passive and active monolithic and hybrid integrated circuits. A principle of achieving these high-quality circuits is described and also confirmed by experimental and theoretical results, which are in good agreement up to 50 GHz. To illustrate the features of the proposed series resonators and demonstrate their effectiveness, two classes of miniature coplanar waveguide (CPW) filters (namely, low-pass and bandpass) are designed using these resonators. The developed low-pass filter has some important advantages such as low insertion loss in passband, very wide stopband, high cutoff rates, small size, low number of elements, and an effective control of spurious signals. On the other hand, the newly developed bandpass filter provides an alternative, yet compact, structure to classical filters. Obviously, many other classes of filters or passive components can also be designed.

Compact MMIC CPW and asymmetric CPS branch-line couplers and Wilkinson dividers using shunt and series stub loading

Circuit size may be reduced by up to 60% by embedding series and shunt uniplanar stubs inside the main uniplanar line since this reuses physical space in the longitudinal direction. This size-efficient stub loading of the main uniplanar line results in robust options for designing compact K-band 90/spl deg/ hybrid couplers and Wilkinson dividers. The approach is confirmed by experimental results that agree well with theory up to at least 30 GHz using both coplanar waveguide (CPW) and asymmetric coplanar stripline (ACPS). Furthermore, these couplers and dividers do not use lumped inductors or capacitors and, consequently, have excellent design accuracy even at millimeter-wave frequencies. Additionally, it is shown that it is possible to design an ACPS 90/spl deg/ branch-line coupler without the conventional CPW quarter wavelength transformers used to match the input and output port characteristic impedances.

A useful new class of miniature CPW shunt stubs and its impact on millimeter-wave integrated circuits

This paper proposes a new concept for the generation of millimeter-wave coplanar waveguide (CPW) shunt stubs printed within the center conductor, as opposed to those printed in the ground plane. Several new designs are presented for CPW open- and short-end shunt stubs patterned inside the center conductor. Unlike conventional stubs, which are patterned inside the ground plane, several advantages are derived from the use of the proposed framework: additional degrees of freedom, lower radiation loss, high compactness, and a reduction of the number of air bridges that are potentially expensive to build. The way to achieve high-quality circuits is detailed and confirmed by experimental results over the large frequency band from 1 to 50 GHz. Good agreement between experimental and theoretical results, obtained using two different full-wave techniques, validates the design procedure. In an effort to explore the advantages offered by the proposed CPW shunt stubs, in terms of their flexibility and potential for innovation, a possibility of the usage of such stubs in the area of filters is investigated. Thus, three novel variants of miniature filters are designed and measured, demonstrating that the proposed shunt stubs are entirely responsible for major reduction of size and better performance. The designs presented here show a new powerful way of achieving size, weight, and cost reduction. They are suitable for use as building blocks for the growing commercial radio-frequency/millimeter-waves wireless communications circuits and systems.

MIMO-UWB Channel Characterization Within an Underground Mine Gallery

Multiple input multiple output-ultrawide band (MIMO-UWB) systems are experimentally evaluated for underground mine high-speed radio communications. Measurement campaigns using two different antenna configurations have been made in an underground gold mine. Furthermore, two scenarios, which are the line of sight (LoS) and the non-LoS (NLoS), i.e., taking into account the mining machinery effect, are distinguished and studied separately. In fact, the channel is characterized in terms of coherence bandwidth, path loss, shadowing, channel correlation, and capacity. Results reveal how antenna array configuration affects main channel parameters and suggest that mining machinery presence substantially affects both received power and time dispersion parameters within the underground mine and should, therefore, be considered when assessing the performance of in-gallery wireless systems. Moreover, it is shown that the MIMO-UWB takes benefit of the large spreading bandwidth and the multipath propagation environment to increase the channel capacity.

A novel integrated antenna for millimeter-wave personal communications systems

Presents the design and experimental results of a coplanar waveguide (CPW) aperture-coupled patch antenna for the extremely high frequency (EHF) band around a center frequency of 37 GHz. The antenna is implemented on a high dielectric constant substrate (/spl epsiv//sub r/=9.9), which is close to the dielectric constant of GaAs and demonstrates the feasibility of integration of such an antenna structure into monolithic circuits. The major advantage of this configuration is that the reverse side of the antenna can be used for the active and feed components. The antenna structure combines the advantages of a CPW with those of the aperture-coupled microstrip antenna and simplifies the structure of the antenna by reducing the number of metallization levels, from three down to two. In addition, this type of coupling is advantageous when applied to millimeter-wave monolithic phased arrays. A unique feed design eliminates the competition for a surface space between the antenna elements and the feed network. In addition, the ground plane shields the antenna half-space from spurious radiation emitted by feed lines and active devices. Finally, aperture coupling avoids problems associated with probe feeds at millimeter-wave frequencies, such as complexity of construction and large probe self reactances. This new type of antenna opens ways to a large number of a new possibilities such as active antennas for millimeter-wave personal communications using monolithic microwave integrated circuits (MMICs) on the same substrate and a combination of optical and radio transmission.

New miniature broadband CPW-to-slotline transitions

This paper proposes a novel class of uniplanar coplanar waveguide (CPW)-to-slotline transitions, which is particularly suitable for monolithic millimeter-wave integrated circuits. Instead of using CPW series stub printed in the ground plane, as is the case in classical CPW-to-slotline transition, this paper shows the capability to use a CPW series stub printed in the center conductor of the CPW. Compared to classical CPW-to-slotline transitions, the proposed transitions have the following advantages: additional degrees of freedom, lower radiation loss, larger bandwidth, higher compactness, and a major reduction of the number of air bridges that are potentially expensive to build. One alternative configuration that appears to have some merit involves the use of the slotline ring resonator, which does not suffer from open-end or short-end effects and, therefore, gives more accurate resonance frequency, provides an accurate localized zero or infinite impedance point, and maintains low- or high-input impedance values over a wide frequency range, depending on the feed type. A principle of achieving such high-quality transitions is detailed and also confirmed by experimental and theoretical results, which are in good agreement up to 50 GHz. A maximum fractional bandwidth of 160% is achieved for a 10-dB return loss, and the corresponding insertion loss is less than or equal to 2 dB.

Simultaneous realization of millimeter wave uniplanar shunt stubs and dc block

The exploitation of the potentialities linked to uniplanar technology for telecommunications is only at its beginning and even if significant advances have been realized, the context remains evolutive. This paper therefore proposes a new concept for the generation of millimeter wave uniplanar shunt stubs by means of slotline resonator instead of coplanar line resonators. Thus, the short end slotline stub has now the ability to be configured as shunt and series stubs, and therefore acts as a bandpass and bandstop filter respectively. This gives additional degrees of freedom to the design. Compared to the existing CPW short-end shunt stub, the advantages which may be derived from the use of the proposed framework are: additional degrees of freedom, lower radiation loss, larger bandwidth, high compactness and a reduction of the number of air bridges which are potentially expensive to build. Its worth noting that the new short end shunt stubs provides both bandpass behavior and dc blocking simultaneously which is not the case for the standard CPW shunt stub. Furthermore, the present paper proves that the capability to generate shunt stubs in slot line form allows one also to relax the limitations inherent to the realization of low and high impedance levels. In this way, various shunt stubs in slotline form with proposed geometries including rectangular and slot ring shapes are fabricated and accurate on-wafer measurements are performed over a large band of interest (1-50 GHz), The realization of these shunt stubs is detailed and also confirmed with experimental results.

The integration of thin-film microstrip and coplanar technologies for reduced-size MMICs

This paper proposes the integration of coplanar waveguide (CPW) and thin-film microstrip transmission lines to achieve size reduction of monolithic microwave integrated circuits (MMICs). The proposed structures take advantage of the multilevel metallization processes offered in MMIC technology. A very compact 90/spl deg/ CPW branchline coupler, operating at 44 GHz, is used to illustrate the technique. In comparison with conventional hybrid couplers, this coupler offers lower insertion loss and significantly smaller dimensions. The area of the coupler is approximately 65% of a conventional coupler. This paper also presents a family of novel series/shunt matching stub structures based on the CPW/thin-film microstrip combination. The technique allows a reduction in the length of matching stubs of approximately 50% by collocating multiple stubs together. Simulated and experimental results are presented in support of the novel structures.

A New Type of Transmission Line-Based Metamaterial Resonator and Its Implementation in Original Applications

In this paper, a new type of transmission line-based metamaterial resonator is proposed. The structure is based on a modified uniplanar series resonator bent to form a close square loop inclusion which contains a distributed capacitance and inductance. Many advantages of the proposed structure over conventional split ring resonators are discussed. Based on simple transmission line theory, the resonance frequency at which a deep rejection frequency band occurs with sharp cutoff rates beside the stopband, due to the presence of negative effective permeability in the dielectric slab of the host transmission line in the vicinity of resonance, is calculated and verified with simulated and measured results. Two prototype microwave devices are designed to illustrate the potentiality of the proposed inclusion. The first design represents a dual-band bandstop filter with designed center band frequencies at 1.6 and 2.2 GHz. The lumped element model of this filter contains four series-connected parallel LC resonators which are implemented using our high Q-factor artificial magnetic materials (AMMs) patterned on the backside of a coplanar waveguide (CPW) transmission line. The second device is a miniaturized hybrid branch line coupler operating at 2.4 GHz, based on a special loading technique that increases the electric length of transmission lines by patterning the ground plane under the conductor trace in microstrip lines with the complementary, dual-behavior, configuration of AMMs. A size reduction factor up to 16.95% is achieved compared to conventional couplers. For both design examples the measured and simulated responses are in very good agreement which validates our work.

Size-reduction techniques for CPW and ACPS structures

In coplanar-waveguide technology, there is a possibility of locating shunt and series matching stubs inside the center conductor of the transmission line. This principle can be used to reduce of the dimensions of microwave components such as monolithic microwave integrated circuits. This paper discusses the concept and presents the design of a reduced-size Wilkinson divider based on the realization of short-circuit series stubs in the signal conductor of an asymmetric coplanar stripline.