Microwave Engineering Europe - June 2008 - (Page 18)

18 ANTENNA DESIGN accurate compared to that predicted from method-of-moments technique, which shows no radiation in the plane of the assumed inﬁnite PCB. Co-simulated and co-optimized circuit elements and antenna To take advantage of polarization diversity, the dipoles are selectively switched on or off by connecting a pin-diode switching network to them. In analyzing this design we must consider: • The effects of the switching network on overall antenna performance. • The inﬂuence of one dipole on the other. • Matching of the switching network between the antenna and transceiver. These considerations can all be analyzed by performing an EM-circuit co-simulation. This can be achieved by integrated the Momentum planar 3-D EM simulator with the Agilent Advanced Design System (ADS). Figure 7 shows the co-simulation setup of the two dipoles and the switching network where the polarization selection is implemented by biasing the PIN diode at the base of each dipole with either a +5 V Figure 8: Reﬂection coefﬁcient of the polarization diversity dipoles including the effects of polarization switching circuitry. References [1] IEEE transactions on microwave theory and techniques, Vol.51, No.2, February 2003 [2] A 60 GHz 4-Way Adaptive Antenna Array Front-End in CMOS, S. Alalusi, R. Brodersen, http://bwrc.eecs. berkeley.edu/Presentations/Retreats/ Winter_Retreat_2005/WednesdayPM/ Win05%20Sayf.pdf. [3] RF-MEMS based adaptive antenna matching module, Bezooijen, et al IEEE Radio Frequency Integrated Circuits Symposium 2007. About the authors How-Siang Yap is the product manger for the Advanced Design System EDA platform in Agilent EEsof with responsibility for developing design solutions for the RF-SiP, MMIC, RFmixed signal board, RF-MW components and antennas targeted at the commercial wireless and defense-aerospace industries. He holds a 1st class honors engineering degree from the University of New South Wales, Australia and a postgraduate technology management diploma from the Helsinki School of Business, Finland. Bart Van Hecke is the product manager for the Advanced Design System RF-mixed signal board ﬂow. He started his career as RF designer and joined Agilent EEsof in 1999. Since, he has been involved in various high-frequency physical design solutions covering: RFmixed signal board, electromagnetic design and veriﬁcation and RF circuit simulation. He holds an engineering degree from the KHBO, Belgium. or -5 V control voltage. The S11 reﬂection coefﬁcient seen from the common feed to the 2 dipoles is shown in Figure 8, which agrees well with the measured response from Reference 1. From here on, if it is necessary to optimize the resonance frequency or S11 matching of the dipoles by adjusting their geometries and changing the switching circuit parameters. Similar techniques can also be used to design an adaptive-antennamatching or beam-forming [Ref 2] network under DSP control in software-deﬁned radios where a single antenna has to operate over different frequencies and bandwidths. It is equally useful for adaptively switching in a capacitor matrix to match the changing antenna characteristics in cell phones when handled in different proximity to the user [Reference 3]. Conclusion The use of EM-simulation techniques provides a powerful toolset for analyzing the design of printed wireless LAN antennas. Different techniques are available and with the rapid simulations available from the latest generation simulators, detailed information can be quickly obtained to assess and optimize the antennas and their associated circuitry. For more information, visit: www.agilent.com/ﬁnd/eesof. Figure 7: Circuit-EM co-simulation enables the two antennas and switching circuitry to be analyzed and optimized together. Applicable also to adaptive antenna matching and beam forming under DSP control. MICROWAVE ENGINEERING EUROPE Free subscription at: www.mwee.com/subscribe Microwave Engineering Europe ● June 2008 ● www.mwee.com http://bwrc.eecs.berkeley.edu/Presentations/Retreats/Winter_Retreat_2005/WednesdayPM/Win05%20Sayf.pdf http://bwrc.eecs.berkeley.edu/Presentations/Retreats/Winter_Retreat_2005/WednesdayPM/Win05%20Sayf.pdf http://bwrc.eecs.berkeley.edu/Presentations/Retreats/Winter_Retreat_2005/WednesdayPM/Win05%20Sayf.pdf http://bwrc.eecs.berkeley.edu/Presentations/Retreats/Winter_Retreat_2005/WednesdayPM/Win05%20Sayf.pdf http://www.agilent.com/nd/eesof http://www.mwee.com/subscribe http://www.mwee.com

Table of Contents Feed for the Digital Edition of Microwave Engineering Europe - June 2008

Microwave Engineering Europe - June 2008 Contents Comment News Cover Feature Designing and Simulating a Wireless LAN Antenna 60GHz: Achieving the Ultimate Wireless Dream New Radar Developments Include HFETs to Challenge DMOS/LDMOS and a 77-GHz CMOS PA for Automotive Applications Testing Raises Concerns Over 802.11-Based High-Speed Bluetooth IP2 & IP3 Design Considerations with Direct Conversion I/Q Demodulator Receiver Products Calendar

Microwave Engineering Europe - June 2008

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