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Shahvarpour A.,Poly Grames Research Center | Alvarez Melcon A.,Technical University of Cartagena | Caloz C.,Poly Grames Research Center
IEEE Transactions on Antennas and Propagation | Year: 2013

The paper addresses the problem of the radiation efficiency of planar antennas on electrically thick substrates. First, the non-monotonic dependency of the radiation efficiency of an infinitesimal horizontal electric dipole on grounded and ungrounded substrates versus the substrate electrical thickness is analyzed. Next, the phenomenology of the observed radiation efficiency is explained with the help of a novel substrate dipole approach, which reduces the actual structure to an equivalent source dipole composed of the original dipole and the substrate dipole radiating into free space. Finally, two solutions for enhancing the efficiency at electrical thicknesses where the efficiency is minimal are studied. © 1963-2012 IEEE.


Shahvarpour A.,Poly Grames Research Center | Kodera T.,Poly Grames Research Center | Parsa A.,Poly Grames Research Center | Caloz C.,Poly Grames Research Center
IEEE Transactions on Microwave Theory and Techniques | Year: 2010

The realization of arbitrary perfect electromagnetic conductor boundaries by a grounded ferrite slab using Faraday rotation is proposed. This is the first practical realization of a perfect electromagnetic conductor boundary to the authors' knowledge. The key principle of the grounded ferrite perfect electromagnetic conductor boundary is the combination of Faraday rotation and reflection from the perfect electric conductor of the ground plane. From this combined effect, arbitrary angles between the incident and reflected fields can be obtained at the surface of the slab, so as to achieve arbitrary perfect electromagnetic conductor conditions by superposition with the incident field. An exact electromagnetic analysis of the structure is performed based on the generalized scattering matrix method and an in-depth description of its operation phenomenology is provided. As an illustration, a tunable transverse electromagnetic (TEM) waveguide with grounded ferrite PMC lateral walls is demonstrated experimentally. Due to its flexibility in the control of the polarization of the reflected field, the proposed grounded ferrite perfect electromagnetic conductor may find applications in various types of reflectors and polarization-based radio frequency identifiers. © 2006 IEEE.


Nikfal B.,Poly Grames Research Center | Zhang Q.,South University of Science and Technology of China | Caloz C.,University of Montréal
IEEE Microwave and Wireless Components Letters | Year: 2014

The concept of signal-to-noise ratio (SNR) enhancement in impulse radio transceivers based on phasers of opposite chirping slopes is introduced. It is shown that SNR enhancements by factors M-2 and M are achieved for burst noise and Gaussian noise, respectively, where M is the stretching factor of the phasers. An experimental demonstration is presented, using stripline cascaded C-section phasers, where SNR enhancements in agreement with theory are obtained. The proposed radio analog signal processing transceiver system is simple, low-cost and frequency scalable, and may therefore be suitable for broadband impulse radio ranging and communication applications. © 2014 IEEE.


Adhikari S.,Poly Grames Research Center | Hemour S.,Poly Grames Research Center | Ghiotto A.,University of Bordeaux 1 | Wu K.,Poly Grames Research Center
IEEE Microwave and Wireless Components Letters | Year: 2015

A magnetically tunable ferrite-loaded half-mode substrate integrated waveguide (HMSIW) is presented. To achieve the magnetic tuning, a planar Yttrium Iron Garnet (YIG) slab is loaded along the metalized wall of the HMSIW, where the concentration of the magnetic field is strongest. Static (DC) magnetic bias is applied on the ferrite slab transversely to the direction of propagation. Measured phases of forward and reverse transmission coefficients show the non-reciprocal behavior of this transmission line. Measured results illustrating the comparison between a single ferrite slab-loaded SIW and a HMSIW are presented. As an application example, a two-dimensionally tunable bandpass filter (BPF) operating at X-band is proposed and studied. By controlling the value of loaded lumped capacitors and the applied magnetic bias, a bandwidth tunable BPF is demonstrated. © 2015 IEEE.


Djoumessi E.E.,Poly Grames Research Center | Wu K.,Poly Grames Research Center
IEEE MTT-S International Microwave Symposium Digest | Year: 2010

A varactor-based tunable diplexer is proposed and experimentally validated for IEEE802.16 standard-based system applications. The proposed transmit/receive (TxlRx) diplexer consists of two tunable dual-mode bandpass filters. Size reduction and band tunability are achieved by using the capacitance of varactors diodes. With two-tone nonlinear characterization test, the diplexer (with higher biased voltage) is found to introduce, in Tx frequency band, a high level of intermodulation product (IIP3). A better insertion loss inf passbands is observed for a lower room temperature. Measuredf insertion loss of our fabricated diplexer is obtained between 5.3 to 2.89 dB and 5.2 to 3.7 dB over the tuning frequency range for the Tx and Rx channels filters bands, respectively. Both filters exhibit better than 40 dB rejection in the passband of its counterpart. The varactors diodes attached to both filters allow 24.5% and 23.3% center-frequency tunability in Tx and Rx filters bands, respectively. © 2010 IEEE.


Ladan S.,Poly Grames Research Center | Wu K.,Poly Grames Research Center
IEEE Transactions on Microwave Theory and Techniques | Year: 2015

This paper presents and demonstrates a harmonic harvesting technique, which aims at rerectifying and recycling the rectifier output harmonics in order to increase the RF-to-dc conversion efficiency. Firstly, an analytical framework is developed based on the Ritz-Galerkin technique to investigate the output power distribution of a simple millimeter-wave rectifier circuit over its dc and generated harmonics components. The numerical results show that about 32% and 66% of the output power is distributed over the dc component and the first harmonic, respectively. In order to recycle and harvest the first harmonic power component, a 35-GHz voltage doubler rectifier implemented in microstrip technology and capable of harmonic harvesting is then studied and designed. To evaluate the performance of the proposed rectifier, the conventional voltage doubler and the harmonic signal rectifiers are fabricated and measured. The measured RF-to-dc conversion efficiencies of 34% at 20-mW input RF power for the harmonic harvester configuration, and 23% at the same input RF power level for the conventional voltage doubler are observed. Moreover, it is shown that the proposed harmonic rectifier suggests about 12% efficiency improvement compared to previously reported millimeter-wave rectifiers at the same level of input power (20 mW). The proposed rectifier configuration can find potential applications in the development of millimeter-wave wireless power transmission devices operating at medium power range (1-100 mW). © 2015 IEEE.


Wang Z.,University of Quebec at Rimouski | Adhikari S.,Poly Grames Research Center | Dousset D.,Poly Grames Research Center | Park C.-W.,University of Quebec at Rimouski | Wu K.,Poly Grames Research Center
IEEE MTT-S International Microwave Symposium Digest | Year: 2012

In this paper, for the first time a novel substrate integrated waveguide (SIW)-based 10W power amplifier (PA), designed with conductor-backed coplanar waveguide (CBCPW)-to-SIW transition matching network (MN), is presented. Transition between CBCPW and SIW is employed for both input and output MN designs, the proposed SIW PA can be easily connected with any microstrip or SIW-based circuits. Asymmetrical and symmetrical types of CBCPW-to-SIW transition MN are proposed. Output SIW-based MN is designed with asymmetrical structure by using one inductive metalized post and input SIW-based MN is designed with symmetrical structure by using two identical inductive metalized posts. One SIW-based 10W PA using GaN HEMT at 3.62 GHz is designed, fabricated, and measured. Measured results show that the maximum power added efficiency (PAE) is 54.24 % with 39.74 dBm output power and the maximum gain is 13.31 dB. At the design frequency of 3.6 GHz, the size of proposed SIW-based PA is comparable with other microstrip-based PAs. © 2012 IEEE.


Wu K.,Poly Grames Research Center | Choudhury D.,Intel Corporation | Matsumoto H.,Kyoto University
Proceedings of the IEEE | Year: 2013

The articles in this special issue focus on the topics of the key technologies and applications that support wireless power transmission. © 1963-2012 IEEE.


Fesharaki F.,Poly Grames Research Center | Wu K.,Poly Grames Research Center
Journal of Lightwave Technology | Year: 2012

High-frequency electro-optical modulator is critical for enabling signal processing and distribution in the next generation cloud-computing, tele-medicine, and telecommunications. In this paper, substrate integrated waveguide (SIW) is exploited as an alternative fundamental transmission line structure in support of electrical signal for the design and development of millimeter-wave and terahertz (THz) traveling-wave polymeric electro-optic (EO) modulator. Optical and full-wave electromagnetic analyses are carried out and structure optimization is made on the basis of such analyses in order to obtain millimeter-wave transmission characteristics and optical response. Compared to its conventional TEM-mode transmission lines, this bandpass non-TEM mode SIW-based EO modulator presents numerous advantages, namely compact structure, low transmission loss, low driving power, simple packaging and flat optical response over a wide frequency range. © 2012 IEEE.


Lemaitre-Auger P.,Ecole Polytechnique de Montréal | Abielmona S.,Poly Grames Research Center | Caloz C.,Poly Grames Research Center
IEEE Transactions on Antennas and Propagation | Year: 2013

Bessel beams are proposed as a practical way to generate well collimated and confined beams at mm-waves or THz for quasi-optical applications. To achieve that, we propose the use of two-dimensional antenna arrays as realizable launchers. Truncated Bessel beams with a main lobe width of few wavelengths (λ) can propagate over several hundreds of λ if the antenna aperture is electrically large. Because such a large aperture would require a large number of antenna elements, sub-sampling distributions are proposed in this work. It is found that arrays with spacings of approximately 4λ generate high quality beams with very low amplitude oscillations over distances of about 300λ in vacuum. The optimal excitation function for such arrays greatly departs from the Bessel one. It is synthesized with an analytical method based on a least mean square error minimization. The synthesis method is scalar, but the pseudo-Bessel beams obtained are vectorial and linearly polarized. Theoretical predictions are confirmed by full-wave simulations using Ansoft Designer. © 1963-2012 IEEE.

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