摘要(英) |
In this thesis, phase shifter and variable transformer are designed using all-pass networks (APNs) and combined to realize an impedance tuner. With the proposed architecture, we can independently control the phase and magnitude of the reflection coefficient by separately adjusting the phase shifter and the variable transformer. Compared with the common Π- or T-shaped tunable matching networks, the proposed impedance tuner architecture exhibits the advantage of straightforward and convenient way of operation, which is good for adaptive matching system application.
The proposed impedance tuner consists of a two-stage phase shifter and a one-stage variable transformer, both of which are based on APNs. The impedance tuner is designed to operate at 2.45 GHz. Design procedures and considerations are described. The capacitors within the APNs are realized by ferroelectric varactors developed in our lab, whereas the inductors are commercially available 0201 surface mount devices. Simulation results show that, when the ferroelectric varactors exhibit a tunability of 2.2, the designed impedance tuner is able to provide a maximum VSWR of 4.83 and a full 360° impedance coverage over the Smith Chart. Within the impedance coverage, the dissipation loss ranges from 2 to 13.5 dB.
The proposed impedance tuner is realized on a sapphire substrate using a fabrication process developed by our lab. The fab process offers ferroelectric thin-film varactor and CrSi2 thin-film resistor. In this work, the CrSi2 thin-film resistor is, for the first time in our lab, used in an integrated circuit. Measurement results of the fabricated impedance tuner show that the maximum VSWR is 2.33 and full 360° impedance coverage is not achieved. We suspect that the reason for the degraded performance is the higher leakage current and lower quality factor of the ferroelectric varactors as the bias voltage increases, which leads to lower varactor tunability, less phase shift, and reduced maximum achievable VSWR. In the re-simulation, measured capacitances and quality factors of test varactors are used and lower varactor tunability values are assumed. It is found that the re-simulation results fit better to the measured results.
In this work, we demonstrate the potential of using APNs for realizing impedance tuners and, for the first time in our lab, realize bias resistors in an integrated circuit with CrSi2 thin film, which leads to a much smaller circuit area.
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參考文獻 |
[1] K. R. Boyle,“The performance of GSM 900 antenna in the presence of people and phantoms,” in IEEE Int. Conf. Antennas and Propagation, Mar. 2003, vol. 1, pp. 35–38.
[2] K. R. Boyle, Y. Yuan, and L. Lighthart,“Analysis of mobile phone antenna impedance variations with user proximity,”IEEE Trans. Antennas Propag., vol. 55, pp. 364–372, Feb. 2007.
[3] A. van Bezooijen, R. Mahmoudi, and A. H. M. van Roermund, “Adaptive methods to preserve power amplifier linearity under antenna mismatch conditions,”IEEE Trans. Circuits Syst. I, vol. 52, no. 10, pp. 2101–2108, Oct. 2005.
[4] W.-C. Chen,“Design and fabrication of phase shifters based on all-pass network,”Master dissertation, National Central University, 2011.
[5] J.-S. Fu,“Adaptive impedance matching circuits based on ferroelectric and semiconductor varactors,” Ph. D. dissertation, The University of Michigan, 2009.
[6] D. Adler and R. Popovich,“Broadband switched-bit phase using all-pass networks,”IEEE MTT-S International Microwave Symposium Digest, July 1991, pp. 265–268.
[7] X. Tang and K. Mouthaan,“Design of large bandwidth phase shifters using common mode all-pass networks,”IEEE Microwave and Wireless Components Letters, vol. 22, no. 2, pp. 55–57, Feb. 2012.
[8] George L. Ragan,“Microwave Transmission Circuits,” McGRAW-HILL BOOK COMPANY, INC., pp. 466-472, 1948.
[9] J. Cusack, S. Perlow, and B. Perlman, Automatic load contour map-ping for microwave power transistors,”IEEE Trans. Microw. Theory Tech., vol. MTT-22, no. 12, pp. 1146–1152, Dec. 1974
[10] Y. Lu, L. P. B. Katehi, and D. Peroulis,“High-power MEMS varactors and impedance tuners for millimeter-wave applications,”IEEE Trans. Microw. Theory Tech., vol. 53, no. 11, pp. 3672–3678, Nov. 2005.
[11] S. Jeong, J. Jeong, and Y. Jeong,“A Design of a Impedance Tuner With Programmable Characteristic for RF Amplifiers,”IEEE Microw. Wireless Compon. Lett., vol. 27, no. 5, pp. 473–475, May 2017.
[12] MT981BL10 High-Power Automatic Tuners, Maury Microw., Ontario, CA, USA.
[13] Y. Bae, U. Kim, and J. Kim,“A programmable impedance tuner with finite SWRs for load-pull measurement of handset power amplifiers,” IEEE Microw. Wireless Compon. Lett., vol. 25, no. 4, pp. 268–270, Apr. 2015.
[14] Q. Shen and N. S. Barker,“Distributed MEMS tunable matching network using minimal-contact RF-MEMS varactors,” IEEE Trans. Microw. Theory Tech., vol. 5, no. 6, pp. 2646–2658, Jun. 2006.
[15] R. K. Waits,“Silicide resistors for integrated circuits,” Proc. IEEE, vol. 59, pp. 1425–1429, Oct. 1971.
[16] T.-W. Ding,“Fabrication and Measurement of Ferroelectric Varactors with Through Substrate Vias on Silicon and Chromium Silicide Thin-Film Resistors,” Master dissertation, National Central University, 2017.
[17] C.-T. Yu,“An integrated passive device process featuring ferroelectric varactors and its application in the fabrication of a microwave phase shifter,”Master dissertation, National Central University, 2015.
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