Vol. 2, No. 4 November 2011 http://www.comm.ntu.edu.tw [email protected] Technology Developed in GICE In this issue Message from the 2 A New Topology for a Common Mode Choke Based on Metamaterial Director Concept Technology from Electromagnetics Group Developed in GICE - A New Topology 1-3 Differential signaling becomes 3(b) and produces transmission zero for a Common popular in high-speed digital circuits for common mode. That is, common Mode Choke due to its adaption of low-power- mode noise can be suppressed by Based on level operation and immunity to the proposed common mode choke Metamaterial crosstalk and EMI. Ideally, it supports at some frequency range. Concept balanced signal propagation on the - Antenna 3-4 differential interconnects. However, Miniaturization Using Zeroth- the non-ideal effects, such as Order Resonance unequal rising and falling at the - Physical Layer 4-5 output buffer, bend and length Security Using mismatch in the differential pairs, Artificial Noise and layout requirement for dense Assisted routing, will induce unintended Beamforming common mode noise coupling to - Stimulation of 5-7 Cooperation in the heat sink or shielding metals and Fig. 1. The configuration of the Cooperative cause serious EMI/EMC problems. To proposed structure solve this problem, a topology for a Spectrum Sensing for Cognitive common mode choke is presented. The proposed common mode choke Radio is fabricated on low temperature co- Fig. 1 shows the configuration of the fired ceramic (LTCC) substrate with Activities 7-8 proposed common mode choke. It is dielectric constant of 7.5 to verify its a periodic structure and each cell filtering properties for common mode. International 8 Corner comprises a pair of coupled line, a Only four layers are applied here, patch, and a connecting structure which means it can be easily shorting the patch to the ground fabricated and embedded on PCB plane. Different from conventional technology. Fig 4 shows its S common mode choke, it can be parameter result. The differential Upcoming Events: realized without the use of the ferrite mode maintains below 3 dB up to 10 material, which is usually applied to GHz while common mode noise is Nov. 30 produce large inductanc e. Its reduced over 10 dB from 3.8 to 7.1 Prof. Natalia K. Nikolova Visit Department of Electrical and equivalent circuit mode l GHz. The common mode suppression Computer Engineering, corresponding to unit cell is in time domain is also demonstrated McMaster University established to explain its behavior in in Fig 5. It shows that the common- different mode operation and can mode peak-to-peak voltage is Dec. 16 be decomposed into two kinds of suppressed over 50 % when the 5 Prof. K.J. Ray Liu Visit Christine Kim Eminent half circuit models, the odd and Gb/s PRBS with a time skew of 40 ps is Professor of Information even mode. Odd-mode half circuit injected into a differential pair. Its Technology, Electrical and model consists of a series inductor electrical size is about 0.16 × 0.26 λg2. Computer Engineering and a shunt capacitor and Department, behaves like an equivalent circuit of In addition, according to the Distinguished Scholar- Teacher, University of the quasi-TEM transmission line as proposed topology in Fig. 1, a Maryland shown in Fig. 3 (a). It has well-defined component-type common mode characteristic impedance and can choke can be realized using one cell Dec. 19 be designed for differential signal circuit. Fig. 6 (a) and (b) shows its Prof. Truong Nguyen Visit transmission. On the other hand, the configuration and test sample, Department of Electrical and Computer Engineering, even mode half circuit model respectively and it has a compact University of California, introduces a parallel resonator in the size of 1.6 × 1.6 mm2. Instead of San Diego shunt admittance as shown in Fig. (Continued on page 2) 2 GICE NEWSLETTER NO 03 Technology (continued from page 1) L1 Lm L Cm 1 C1 C1 C2 L1 Fig. 2. The distributed equivalent circuit with common- mode suppression LL1m LL1m C1 Fig. 4. The S-parameter comparison of the simulation and CC 2 measurement for the four cells 1m 2L C21 1 0.5 0.4 Reference Filter 0.3 (a) (b) 0.2 Fig. 3. The equivalent circuit models for (a) odd mode and 0.1 (b) even mode. 0 simple routing on the top layer,a spiral routings are -0.1 introduced on the top layer to lower stopband and Amplitude-0.2 (mV) invoke the two zeros to enhance the common- -0.3 mode suppression band. Four signal pads and one -0.4 ground pad are formed for the application of the -0.5 component. The S parameter result corresponding 0 2 4 6 8 10 Time (ns) to the common mode coke incorporating the pad effect is shown in Fig 7. Its differential mode insertion Fig. 5. The measured common-mode noise is reduced loss keeps below 3 dB up to 8 GHz. It leads in two by the proposed filter zeros for common mode at 2.5 GHz and 5.5 GHz, and meanwhile a suppression band over 10 from 2.2 to 6.5 GHz. Based on the proposed topology, two common mode chokes, an embedded periodic Message from the Director structure and a surface-mounted device, were realized on LTCC substrate. The two structures prove that the proposed topology not only preserves a good differential mode transmission but also Kwang-Cheng Chen addresses a wide suppression band for common mode. The most important thing is the proposed Professor & chokes without using ferrite materials possess lower GICE Director cost than conventional one. GICE Honors As time flying, GICE Newsletters is 2 years old. We hope the readers to enjoy our research Student Winning 2011 IEEE International Workshop on results, while GICE covers research areas in Multimedia Signal Processing – The Top 10% Paper communications, signal processing and Award multimedia, networks, EM waves and circuits. We also look forward to feedback and Keng-Sheng Lin comments from readers. Finally, on behalf of GICE, let me express Advisor: Professor Homer H. Chen Topic: Automatic highlights extraction for drama video Merry Christmas and Happy New Year! using music emotion and human face features 3 (continued from page 2) Technology 0 -5 -10 -15 -20 -25 1.6 mm 1.6 mm -30 Sdd21_simu S parameters (dB) parameters S -35 Scc21_simu (a) (b) Scc21_meas Sdd21_meas -40 Sdc21_meas Fig. 6. (a) The configuration and (b) test sample of the -45 proposed component-type common mode choke 0 1 2 3 4 5 6 7 8 9 10 Frequency (GHz) For more information please contact: Professor Tzong-Lin Wu Fig. 7. The simulation and measurement results of the Email: [email protected] proposed common mode choke Antenna Miniaturization Using Zeroth-Order Resonance from Electromagnetics Group Composite right/left-handed (CRLH) transmission lines Among the various kinds of TLs, we chose CPW as (TLs), composed of shunt inductors and series the host TL because of its uniplanar structure with capacitors periodically loaded along the host TLs, only one metallic and dielectric layer and ease of have drawn much attention because of several shunt connection between the signal trace and unique properties that they possess. One important bilateral ground plane. Using CPW as the host line, property is the zeroth-order resonance (ZOR), which is the shunt inductor and series capacitor can be also known as the infinite-wavelength property. A realized by using a pair of folded shorting stub CRLH TL would have a vanishing phase constant as inductors and interdigital capacitor, respectively, operating at its ZOR. Unbalanced CRLH TLs possess to keep the unit cell as compact as possible. Based two distinct ZORs, namely the shunt and series on the aforementioned formulas and the resonant resonances (ωsh and ωse). When terminated by an condition for ZOR, we have also derived a set of open/short circuit, the CRLH TL would become a formulas, which can be utilized to determine the shunt/series zeroth-order resonator. Both resonator values of the shunt inductance and series types can be exploited to design electrically small capacitance once the dimensions of the host CPW antennas since the resonant conditions are and the resonant frequency of the ZOR are given. independent of their physical lengths. However, only These formulas greatly simply the design and one is feasible because the CRLH TL should be analysis of IL and CL CPWs, and more importantly, terminated by either open or short circuit. they can easily be generalized to IL and CL wave- Consequently, the unused resonance may be guiding structures using other host lines, such as removed to decrease the design complexity of CRLH microstrip lines or striplines. TLs, leading to inductor-loaded (IL) TLs and capacitor- loaded (CL) TLs. Both IL and CL TLs are still periodic The associated ZOR of the IL and CL CPWs can be wave-guiding structures. The unit cell of an IL TL is exploited to realize electrically small antennas. To composed of two identical short sections of the host ensure a compact antenna size, both of the TL and a shunt inductor in between, while the unit cell proposed designs are formed by only two unit cells. of a CL TL has a series capacitor in between instead. Photographs of the two fabricated prototypes are The former sustains the shunt ZOR, while the latter shown in Fig. 2. Both antennas have been supports the series ZOR. Applying the periodic designed using our derived formulas, and the boundary condition and taking into account the predicted performance agrees very well with those losses of host TL, we have derived the closed-form obtained via measurements and full-wave formulas to calculate the propagation constants of IL simulations.