Browsing by Author "Cheng X."

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An omnidirectional wrappable compact patch antenna for wireless endoscope applications
(2012) Cheng X.; Wu J.; Blank R.; Senior D.E.; Yoon, Y.K.
An inductively loaded compact patch antenna for a radiation frequency of 433 MHz is designed taking into consideration a human-body model and fabricated on a flexible liquid crystalline polymer (LCP) substrate, which is subsequently wrapped into a cylindrical shape to achieve a monopole-like omnidirectional radiation pattern for wireless endoscope applications. The wrapped patch antenna has a stretched length of 31 mm (0.07λ), and its cylindrical form has a diameter of 10 mm and a width of 18.5 mm, whose dimensions are designed to be comparable to those of a commercially available capsule endoscope. Compared to a traditional patch antenna with the same radiation frequency, an 86% length reduction is achieved. Omnidirectionality is desired to increase the space coverage in communication between the randomly moving capsule inside and the receiver outside the body. The enclosed cylindrical cavity, surrounded by the ground plane of the patch, provides an electromagnetic interference (EMI) protected room that is useful for the placement of other electronic components. Multiple inductive notches on a patch designed for antenna size reduction are described by an equivalent circuit model. Human-body phantom solution is used for antenna characterization. The antenna, located at the outermost layer, serves not only as a good radiating unit, but also as the EMI protecting, mechanically supporting, packaging layer of the endoscope system. © 2002-2011 IEEE.
Electrically tunable evanescent mode half-mode substrate-integrated- waveguide resonators
(2012) Senior D.E.; Cheng X.; Yoon, Y.K.
Electrically tunable evanescent mode half mode substrate integrated waveguide (HMSIW) resonators are implemented for S band applications. An HMSIW loaded with a complementary split ring resonator (CSRR) achieves forward electromagnetic wave transmission below the characteristic waveguide cutoff frequency due to evanescent wave amplification. A variable capacitor connected to one of the conductors of the CSRR changes its effective capacitance to ground, resulting in frequency tuning of the resonator. Three different configurations are investigated with a varactor diode connected between the ground and three different contact points of the CSRR. The external Q factor is slightly affected by the frequency tuning. More than 15% tunability is achieved around 3.4 GHz. Full wave structure simulation results are in good agreement with those of measurement. © 2006 IEEE.
Highly compact surface micromachined metamaterial circuits using multilayers of low-loss Benzocyclobutene for microwave and millimeter wave applications
(2012) Eliecer Sr. D.; Cheng X.; Yoon, Y.K.
This work explores the implementation of highly compact three dimensional (3D) integrable metamaterial based transmission lines on a low resistivity CMOS grade silicon substrate for microwave and millimeter wave applications. The composite right-left handed (CRLH) architecture is able to be integrated with an integrated circuit (IC) using a multilayer surface micromachined fabrication process as a post-CMOS process. The fabrication process employs the negative tone photo sensitive Benzocyclobutene (BCB) as a low-loss dielectric interlayer material allowing packaging compatible high performance RF circuits. Since the low temperature and multilayer fabrication is compatible with CMOS/MEMS processes, it allows the batch fabrication of multiple devices and the easy implementation of 3D vertical interconnects. The design, modeling, fabrication and on-wafer characterization are presented for 50 Ω compact multilayer finite ground coplanar waveguide (FGC) CRLH unit cells and transmission lines for broadband and multiband operation at Ku and Ka frequencies of 14 GHz and 35 GHz, respectively. Also, the comparison between the simulation and measurement results up to 40 GHz on the aforementioned 3D electromagnetic structures is provided. The left handed capacitance and inductance components of the CRLH structures are implemented with photolithographically defined Metal-Insulator-Metal (MIM) capacitors and BCB embedded meander inductors, respectively, which allows the fabrication of very compact CRLH devices. The fabricated dual band unit cell features a size of λ 0/30 at 14 GHz and an insertion loss of less than 2dB within the passband. © 2012 IEEE.
Wireless passive sensing application using a cavity loaded evanescent mode half mode substrate integrated waveguide resonator
(2011) Senior D.E.; Cheng X.; Jao, P.F.; Kim C.; Kim J.K.; Yoon, Y.K.
In this work, an evanescent mode half mode substrate integrated waveguide (HMSIW) resonator is designed for a wireless passive sensing application at 5 GHz. The wireless pressure sensor has been implemented by placing a small Polydimethylsiloxane (PDMS) cavity, covered with a metal coated membrane, on top of the original resonator or by using a cavity ground plane. When the metal coated membrane is deformed or deflected by an external pressure, it perturbs the electric field of a complementary split ring resonator (CSRR) patterned on top of the HMSIW, producing a shift in the resonance frequency. Because it operates in a microwave frequency spectrum, it offers a high pressure-frequency sensitivity. Resonance frequency as a function of an applied pressure has been presented. Also, a broadband antenna has been integrated to perform wireless interrogation of the sensor. © 2011 IEEE.