3300

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 55, NO. 11, NOVEMBER 2007

A Five-Band Reconfigurable PIFA for Mobile Phones Kevin R. Boyle, Member, IEEE, and Peter G. Steeneken

Abstract—We describe the design of a small microelectromechanical systems (MEMS) switched planar inverted F antenna capable of operation in five cellular radio frequency bands. Both simulated and measured results are shown using MEMS devices fabricated in an industrialized process based on high-ohmic silicon. Results show that the antenna bandwidth (or size) and specific absorption rate can be significantly improved using such devices.

TABLE I UTRA FREQUENCY BANDS

Index Terms—Antennas, microelectromechanical (MEM) devices, planar inverted F antenna (PIFA), specific absorption rate (SAR).

I. INTRODUCTION

P

LANAR inverted F antennas (PIFAs) are widely used in mobile phones [1]–[8]. This is primarily because they exhibit an inherently low specific absorption rate (SAR) and because they can be installed above other components. PIFAs suffer from a problem that is common to all electrically small antennas—they have limited bandwidth for a given size. This is a constant challenge for antenna designers, since higher degrees of global operation (or “roaming”) are sought, which, in turn, requires operation within continually more frequency bands. This is illustrated in Table I, which shows the nine bands allocated for the “3RD Generation”—or 3G—UMTS Terrestrial Radio Access (UTRA) system. UTRA bands II, III, V, and VIII are also currently widely used by “2ND Generation”—or 2G—systems such as Global System for Mobile Communications (GSM). With the addition of UTRA band I, these bands allow quad-band 2G and tri-band 3G operation. Because of this, future mobile phones are likely to be capable of operation in these bands, which are shown pictorially in Fig. 1. As indicated, bands II and V are used in the USA, whereas bands I, III, and VIII are used in Europe. All bands are also widely used worldwide. Fortunately, simultaneous operation is not required in all bands. This means that the antenna can be switched to operate in a subset of the total number of bands at any given time. To achieve this (over a bandwidth of approximately one octave) without significantly reducing efficiency, low loss switches are required. Mobile phones typically use either P-I-N diode or GaAs pseudomorphic high electron mobility transistor (pHEMT) based , in the ON switches. Both can be modeled by a resistor, state and by a low quality factor (Q) capacitor, , in the OFF state. There is normally a tradeoff between and , Manuscript received November 21, 2006; revised May 21, 2007. K. R. Boyle is with NXP Semiconductors Research, Redhill, Surrey RH1 5HA, U.K. (e-mail: [email protected]). P. G. Steeneken is with NXP Semiconductors Research, 5656 AE Eindhoven, The Netherlands (e-mail: [email protected]). Digital Object Identifier 10.1109/TAP.2007.908822

Fig. 1. Common cellular frequency bands used in Europe and the USA (MHz).

such that, for a particular technology, the product is constant. This results in a tradeoff between insertion loss and isolation. High quality microelectromechanical systems (MEMS) switches offer the prospect of both low loss in the ON state (ON resistances of less than an ohm are feasible) and high Q capacitance in the OFF state. These characteristics make them ideal for antenna switching. Two variants are applicable: galvanic devices, where direct metal-to-metal contacts are made in the ON state, and capacitive devices, where a thin dielectric separates the contacts in the ON state. In both types, a relatively wide air gap is maintained in the OFF state, giving a low valued, high Q capacitor (air is a very good dielectric). The metal-to-metal contact of the galvanic devices is ideal electrically, since it gives low losses over a wide bandwidth. However, the contacts are prone to wear (pitting, hardening or material transfer of the contact metals), making such devices difficult to realize in practice [9]. Capacitive devices, on the other hand, are easier to implement, but the residual ON capacitance must either be resonated out by a small series

0018-926X/$25.00 © 2007 IEEE

BOYLE AND STEENEKEN: FIVE-BAND RECONFIGURABLE PIFA FOR MOBILE PHONES

3301

Fig. 2. Cross-sectional view of a capacitive MEMS switch realized in the NXP Semiconductors PASSI process (shown in the open state). The silicon nitride acts as a dielectric in the closed state. Fig. 4. Radiating and balanced mode analysis of a slotted PIFA with an arbitrary load.

Fig. 3. Typical simulation and measurement of the variation of capacitance with dc actuation voltage for a capacitive MEMS switch at 900 MHz.

inductance (adding resistance and reducing the overall quality factor) or incorporated in designs. Capacitive switches, of the type shown in Fig. 2, are reported here [10]–[17]. These devices are fabricated in the industrialized NXP Semiconductors PASSI process: a thin-film high-ohmic silicon process with just five mask steps (with two dielectric and three metal layers). Only slight modifications are made to the process in order to manufacture MEMS devices. A typical device characteristic is shown in Fig. 3. With zero dc bias the switch is in the OFF state and exhibits a low capacitance (point in Fig. 3). As the dc voltage is increased, the capacitance slowly increases as the beam slowly deforms and the air gap reduces. At point the electrostatic force on the beam overcomes all other mechanical forces and the beam collapses onto the silicon nitride layer. This is termed “pull-in”. Beyond the dc voltage at which “pull-in” occurs the capacitance increases only slightly as more pressure is applied at interface between the beam and the silicon nitride layer. After “pull-in” the switch is in the ON state and exhibits a high capacitance. If the dc voltage is then reduced, the capacitance slowly reduces (between points and in Fig. 3) as the beam begins to lift from the silicon nitride layer. At point the mechanical force overcomes the electrostatic force and the beam “releases” and returns to a low capacitance state. This capacitance reduces very slightly as the dc voltage is further reduced. Clearly a high dc voltage is required to turn the device on: it is anticipated that this will be provided by a charge pump circuit with low power consumption [17].

Although MEMS switched antennas have been reported previously [18]–[20], none have been shown to be capable of operation over five mobile phone frequency bands. Reconfigurability is normally achieved in one of three ways: by selectively switching parts of the antenna structure in or out, by changing the antenna geometry (i.e., by mechanical movement) or by loading or re-matching the antenna externally. This paper focuses on the latter of these techniques—it is the least studied method, but has the considerable advantage of allowing the antenna to be reconfigured entirely in the circuit domain. This is an attractive option, since all switching and biasing circuitry is kept off the antenna structure. Circuitry located on the antenna is more problematic than might be expected, since isolation must be maintained and because a minimum number of (relatively large) connections between the antenna and the supporting PCB are desirable in a mobile phone. Also, the technology used to fabricate the antenna is often incompatible with circuit manufacturing techniques such as reflow soldering etc. The remainder of this paper is arranged as follows. Section II gives the basic theory of operation of the switched antenna structure. Section III describes the antenna geometry. Section IV gives details of the circuits attached to the antenna. Section V presents simulation results for the combination of antenna and circuitry in the different operational modes of the system. Results for both input impedance and SAR are shown. Section VI describes the hardware implementation of a prototype that is, as far as is reasonable, identical to the simulated structure. In Section VII, the measured results for this prototype are presented and discussed. Finally, conclusions are drawn in Section VIII. II. ANTENNA THEORY A slotted PIFA and a supporting PCB/handset are shown diagrammatically in Fig. 4. This configuration can be decomposed into radiating and balanced modes as previously shown in [21]. The input impedance is given by (1) where is the load impedance applied to the un-fed side of is the radiating mode impedance, and is the the slot, impedance of the short circuit transmission line formed by

3302

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 55, NO. 11, NOVEMBER 2007

Fig. 5. Equivalent circuit with a short circuit load.

Fig. 7. S of a slotted PIFA with different load reactances applied to the un-fed side of the slot (referenced to 50 ).

Fig. 6. Equivalent circuit with an open circuit load.

the slot, derived from the balanced mode. The current sharing factor, is given by (2) and are the radiating mode currents at the feed and load, respectively. , this simplifies to For the special case of (3) This is similar to the well-known expression for a folded dipole—the radiating mode is impedance transformed by a and adds in parallel with the balanced mode. factor The equivalent circuit is illustrated in Fig. 5. It should be noted that the impedance transformation in this mode is high, is greater than due to the position of the slot. since This tends to produce an impedance that is too high. It is also and worthy of note that the bandwidth can be enhanced if are resonant at the same frequency (when becomes a double-tuning circuit). gives Also of interest is the open circuit case. Setting (4) The balanced mode impedance is transformed by a factor , and adds in series with the radiating mode. The equivalent circuit is shown in Fig. 6. The balanced mode causes the antenna to resonate twice at lower and higher frequencies than determined by the radiating and ). The low and high frequency mode (controlled by resonances occur when the radiating mode capacitance and inductance are cancelled by the inductance and capacitance of the

transformed balanced mode respectively. There is no impedance transformation with an open circuit load, which tends to produce an impedance which is too low. With a reactive load the antenna can be tuned over a wide range of impedances: from below the first resonance up to the second resonance of the open circuit mode. Qualitatively, this in (1), making the substitucan be understood by varying and tions . Values that are of the same order as those used in , , the subsequent detailed design are: , , , . is illusUsing these values, the impedance variation with trated in Fig. 7. With inductive loading, any frequency between the first resonance of the open circuit mode and the resonance of the short circuit mode can be achieved. Capacitive tuning allows frequencies between the resonance of the short circuit mode and the second resonance of the open circuit mode to be covered. From the equivalent circuits with open and short circuit loads, it is clear that the open circuit mode exhibits resonance at a lower resistance than the short circuit mode (since the resistance is not impedance transformed). Hence, with both increasing inductive and decreasing capacitive loading, the resistance at resonance falls compared to that of a short circuit load (indicated by in Fig. 7). With capacitive loading, this is an increase in not a serious problem, since the simple model above does not account for the increase in the antenna radiation resistance that tends to occur over the range of frequencies of interest (1.71 to 2.17 GHz). However, degradation of the match at the lower end of the tunable range (where the radiation resistance tends to fall as frequency is reduced) is problematic: in the design that follows the low frequency match is improved by switching in a shorting pin to give an upwards impedance transformation. It should be noted that it is possible to tune the antenna to frequencies below and above the first and second resonances of the open circuit mode using capacitive and inductive loading respectively. However, this can result in low radiation resistance and hence, low bandwidth. Despite this, a tunable range of 3:1 or more is achievable with a compact antenna.

BOYLE AND STEENEKEN: FIVE-BAND RECONFIGURABLE PIFA FOR MOBILE PHONES

3303

The slot is located such that it is unlikely to be perturbed when the phone is held. For the same reason, slots are avoided in the part of the antenna parallel to the PCB [21], [22]. The slot is also designed to give some double-tuning in the high frequency modes. IV. MEMS CIRCUITRY

Fig. 8. MEMS switched PIFA and PCB (dimensions in mm).

III. ANTENNA GEOMETRY The antenna geometry is shown in Fig. 8. The antenna has dimensions 40 mm 12 mm and is located 8 mm above the phone printed circuit board (PCB). The PCB has dimensions and is metalized on the back surface to provide an RF ground. The antenna is connected to the RF circuitry at points A, B, C, and D. For ease of manufacturing, all circuitry is on the PCB rather than the antenna. The antenna is fed at point D and shorted to ground at point B. The impedance at point A controls the antenna resonant frequency according to the theory developed in [21] and outlined in the previous section. With a high impedance at this point (i.e., a MEMS device in the OFF state), the slot in the antenna acts as an inductor, reducing the resonant frequency and allowing operation in the low-band. In this condition, the antenna resistance is transformed up by the provision of a low impedance at point C (i.e., a MEMS device in the ON state connected to ground). A double-tuning capacitor is also introduced when point C is switched to ground in order to tune out shunt inductance introduced and, hence, extend the bandwidth. With a low impedance at point A, the inductance of the slot is removed and the antenna resonates at a high frequency. In this mode the slot provides an upwards impedance transformation, hence point C is switched to a high impedance. This also disconnects the double tuning capacitor from ground, since it not required in the high frequency modes. At high frequencies, the resonant frequency can be shifted slightly higher or lower by capacitively or inductively loading at point A respectively, as shown in Section II.

A MEMS-based circuit is used in conjunction with the antenna and is shown in Fig. 9. The MEMS devices (shown as variable capacitors) are used as capacitive switches, having a low capacitance in the OFF state and a high capacitance in the ON state. The required actuation voltage is between 30 V and 50 V. The circuit values for each operational mode are given in Table II. The matching inductor, L1 is fixed and is realized as a meander line on the PCB. L2 is for dc biasing and is realized using a 10 nH surface mount device (SMD). Capacitors CB1 and CB2 are used for dc blocking, whereas CD1–CD4 are for decoupling. All are 200 pF SMDs. Finally, resistors R1-R4 have a and are for decoupling the dc actuation voltresistance of 10 ages of the MEMS switches applied at terminals VDC1–VDC4. The MEMS capacitors CM2 and CM3 are realized as a series combination of two capacitive switches in order both to reduce the OFF state capacitance and to improve voltage handling. CM1 is a parallel combination of two capacitive switches in order to increase the ON state capacitance. CM4 is the combination of a fixed and a MEMS capacitor, since this allows a lower ON/OFF capacitance ratio to be used. CDT is a fixed capacitor that is used to double-tune the antenna in the lowest frequency mode. It is realized on the MEMS die to allow non-preferred values to be used, and because PASSI capacitors have a better quality factor to size ratio than equivalent SMDs. V. SIMULATED RESULTS A. Impedance Simulations The simulations presented in this section are performed using two steps. First, the antenna and interconnects are modeled using Ansoft HFSS, with all component positions represented as lumped ports. This allows a multiport s-parameter file to be generated and subsequently imported into the Agilent ADS circuit simulator. Components are placed at the ports of the s-parameter network and the input impedance and circuit efficiency (including antenna mismatch but not radiation efficiency) simulated. The MEMS devices are represented by the simplified equivand represent the contact alent circuit shown in Fig. 10. inductance and resistance of the devices respectively. and represent the inductance and resistance of the internal intermodels the intrinsic connects of the devices respectively. and low capacitance of the device, which is used in high states with a simulated maximum ratio of and represent the substrate approximately 20. Finally, capacitance and resistance respectively. At the frequencies conis negligibly small sidered here the reactance associated with compared to . The reader is referred to [16] for further details of the physical phenomena that give rise to this equivalent circuit. This reference also gives simulated and measured quality factors.

3304

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 55, NO. 11, NOVEMBER 2007

Fig. 9. MEMS switched PIFA circuit. Points A, B, C, and D correspond with those shown in Fig. 8.

TABLE II MEMS CAPACITOR VALUES (PF) WITH OPERATIONAL MODE

resonant frequency of the UTRA Band I mode is deliberately designed to be too high, to allow dc tuning to a higher capaciof 6 dB tance and, therefore, a lower frequency (when an is achievable). dc tuning is applied over the “pre-pull-in” range indicated in Fig. 3 (between points A and B). At resonance the antenna Q is approximately 10 and 12 in the low- and high-bands respectively. This is a significant improvement over equivalent dual-band (un-switched) configurations, due to the band specific matching that is made possible by switching. B. SAR Simulations

Fig. 10. Simplified equivalent circuit of a capacitive MEMS switch.

The simulated impedance in the four operational modes is shown in Fig. 11. All modes, with the exception of UTRA Band of 6 dB or better (referred to 50 Ohms). The I, have an

The SAR in the high frequency modes can be significantly less than that of conventional antennas. This happens because the entire antenna is used, whereas for conventional antennas an additional local resonance is often employed to give extended high frequency bandwidth. This is illustrated in this section. SAR is simulated in Ansoft HFSS using a truncated flat phantom as shown in Fig. 12. A flat phantom is considered to be more appropriate for comparative simulations than a curved alternative since a constant spacing is maintained between the phantom and the PCB. In the simulations that follow the , , spacing is 5 mm. At 900 MHz , , , whereas at 1800 , , , , MHz .

BOYLE AND STEENEKEN: FIVE-BAND RECONFIGURABLE PIFA FOR MOBILE PHONES

3305

Fig. 12. Flat phantom used for comparative SAR simulations.

Fig. 11. Simulated input impedance: 824–960 MHz (black, solid), 1710–1880 MHz (gray, solid), 1850–1990 MHz (black, dashed), 1920–2170 MHz (gray, dashed). (a) Smith chart, (b) S .

To minimize reflections at the truncation surfaces of the phantom, these surfaces are defined as impedance boundaries, having the characteristic impedances of the dielectrics used. The characteristic impedance of the head is and per square at 900 and 1800 MHz, respectively. The characteristic impedance of the skin layer (modeled as Perspex to be consistent with SAR measurement procedures) is 183.8 ohms per square at both frequencies. Fig. 13(a) shows the simulated SAR of a conventional tri(also shown band antenna of dimensions in Fig. 12). A parasitic element—which is very common in practical implementations—is used to extend the high-band frequency range: the antenna covers the frequency bands 880–960 MHz and 1710–1990 MHz. It can be seen that the SAR contours are localized between the driven antenna and the parasitic eleaveraging ment. The maximum SAR is 13.4 W/kg with a 1 volume and an input power of 1 W.

Fig. 13(b) shows contours for the MEMS switched antenna. Clearly, the SAR contours are less localized and the maximum SAR is significantly less at 9.3 W/kg, despite the fact that the MEMS switched antenna has a volume that is approximately only 55% of that occupied by the conventional antenna. Simulated efficiencies are comparable. Low high-band SAR is one of the principal advantages of using a MEMS switched antenna: it is possible to provide operation over a wide band without using additional resonances that, in turn, lead to high SAR. The SAR in the low-band is approximately the same for MEMS switched and conventional designs. VI. IMPLEMENTATION A photograph of the MEMS switched antenna is shown in Fig. 14. The antenna is fabricated from a polyimide flexible PCB that is first bonded to a rigid GETEK PCB and then folded over a Rohacell block. The antenna/PCB combination is fed via a coaxial cable at a central point on the PCB to avoid excessive perturbation from the feeding cables [23]. A microstrip line runs between this point and the antenna feed. The MEMS capacitors are placed on two dies, separated from the wafer using laser dicing. Die 1, containing CM1 and CDT, is mounted near points C and D (refer to Fig. 9) and Die 2, containing CM2, CM3, and CM4, is mounted near points A and B. Each MEMS capacitor has a unique geometry, as required to give the values given in Table II. The dc bias lines used to actuate the MEMS switches run from the circuitry under the antenna to a connector that is adjacent and close to the RF connector. dc cables from this connector

3306

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 55, NO. 11, NOVEMBER 2007

Fig. 14. MEMS switched PIFA and PCB.

Fig. 13. Simulated SAR at 1845 MHz (W/kg with a 1 cm averaging volume and an input power of 1 W): (a) conventional antenna (with parasitic element), (b) MEMS switched antenna.

are routed down the outside of the coaxial cable during measurements. The unfolded antenna and PCB, with all components present, is shown in Fig. 15. Parts of the MEMS-based frequency switching circuitry and antenna matching circuitry (connected to the antenna at points A and C, respectively, in Fig. 9) are shown in detail in Fig. 16 and Fig. 17, respectively. These photographs show that the bond wires used to connect from the MEMS dies to the PCB interconnects are rather

Fig. 15. MEMS switched PIFA and PCB.

long—much longer than simulated—in part due to the solder used to connect the SMDs. To compensate for device and assembly uncertainties, MEMS devices with slightly varying layouts are implemented (within the expected tolerance range) on four identical PCBs (with antennas). VII. MEASUREMENTS The MEMS devices—early research devices of 2005—are unpackaged and, hence, susceptible to sticking. Because of

BOYLE AND STEENEKEN: FIVE-BAND RECONFIGURABLE PIFA FOR MOBILE PHONES

3307

Fig. 18. Capacitance (C) as a function of actuation voltage (V) for capacitive MEMS switches CM1-4. Device CM1 consists of two switches in parallel. CM2 and CM3 consist of two switches in series. Device CM4 has a parallel 0.3 pF capacitor (Fig. 9). The hysteresis in the CV curve is indicated by the arrows. Fig. 16. MEMS die2 and surrounding components.

Fig. 17. MEMS die1 and surrounding components.

this, all tests that involve actuation of the devices are performed whilst blowing nitrogen over them. Fig. 18 shows typical capacitance-voltage measurements of all 4 switches (CM1, CM2, CM3 and CM4) at a measurement frequency of 10 MHz using an HP 4275A LCR meter. Capacitance values of the switches in the OFF state are near the designed values. However, the ON state capacitances are only 40% of the designed value due to the surface roughness of the bottom of the moving beam. This creates an air gap between the electrodes that reduces the capacitance density. The measured capacitance is approximately 8, which is subswitching ratio stantially less than the designed value of 20. Band selection is performed by applying dc voltages at the terminals VDC1, VDC2, VDC3, and VDC4 to close the appropriate switches according to Table II. Measured results for the antenna and MEMS combination with the best overall performance are shown in Fig. 19.

Fig. 19. Measured S for band V/VIII (black, solid), band III (dark gray, solid), band II (black, dotted) and band I (light gray, dotted).

All 6 dB bandwidths are significantly lower than simulated. This is largely due to antenna mismatch: the low-band response is inductive whilst the high-band is capacitive. Matching the low-band capacitively and the high-band inductively (in simulation with lossless components) yields the results shown in Fig. 20. of better In the low-band the antenna is matched to an than 6 dB from 748–912 MHz. This represents a fractional bandwidth of 19.9%. Another identical antenna with MEMS having slightly different capacitance values achieved 765–950 MHz (fractionally, 22%) without any matching, showing that a wide bandwidth resonance is obtained. The center frequencies are somewhat lower than simulated.

3308

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 55, NO. 11, NOVEMBER 2007

ACKNOWLEDGMENT The authors gratefully acknowledge J. van Beek, P. van Eerd, R. Smulders, P. Snoeijen, and T. den Dekker for their assistance in the assembly and fabrication of the MEMS switched antenna. Also colleagues at NXP Semiconductors, particularly F. van Straten and P. Lok, for their support. REFERENCES

0

Fig. 20. Measured S after matching (shown below 6 dB) for band V/VIII (black, solid), band III (dark gray, solid), band II (black, dotted) and band I (light gray, dotted).

For the high frequency bands, the resonant frequencies are higher than simulated. With matching, the 6 dB bandwidths are 1840–2151 MHz, 1849–2156 MHz and 1901–2185 MHz for the UTRA bands III, II, and I, respectively, (fractionally, approximately 15%). These bandwidths are slightly wider than those simulated. Resonant frequency shifts are clearly observed in the high frequency modes, though the magnitudes of the shifts are less than simulated. The differences between simulation and measurement are attributed predominantly to uncertainties in the capacitances of the MEMS devices and the long (un-simulated) bond wires used. Capacitance tolerances in the ON state are determined mainly by the surface roughness of the top metal layer (the layer that moves). In the OFF state, tolerances are defined predominantly by geometric variations (i.e., the size of the air gap). The bond wires are longer than expected (and difficult to simulate due to their somewhat arbitrary shape) in part because the solder associated with the SMDs prevented direct routing. No radiation pattern measurements are presented due to the need to actuate the MEMS devices in a nitrogen environment and the difficulty of doing so in an anechoic chamber. However, simulations indicate that the loss of efficiency due to the MEMS devices is less than 7% in all modes. VIII. CONCLUSION A five-band reconfigurable antenna, utilizing capacitive MEMS switches is demonstrated. The measured prototype confirms that the antenna is capable of operating in several modes over a bandwidth of greater than one octave. It also confirms that wide bandwidths are feasible (in each mode) from an antenna that is smaller than conventional. Simulations show that superior SAR performance is possible in high frequency modes. In the future, the use of directly soldered, packaged MEMS devices with improved capacitance density tolerances, will lead to closer agreement between simulations and measurements. The use of packaged devices will allow simple measurement of antenna radiation properties.

[1] Y.-X. Guo, M. Y. W. Chia, and Z. N. Chen, “Miniature built-in multiband antennas for mobile handsets,” IEEE Trans. Antennas Propag., vol. 52, no. 8, pp. 1936–1944, Aug. 2004. [2] Y.-X. Guo and H. S. Tian, “New compact six-band internal antenna,” IEEE Antennas Wireless Propag. Lett., vol. 3, no. 1, pp. 295–297, 2004. [3] P. Ciais, R. Staraj, G. Kossiavas, and C. Luxey, “Compact internal multiband antenna for mobile phone and WLAN standards,” Electron. Lett., vol. 40, no. 15, pp. 920–921, Jul. 2004. [4] P. Ciais, C. Luxey, A. Diallo, R. Staraj, and G. Kossiavas, “Pentaband internal antenna for handset communication devices,” Microw. Opt. Technol. Lett., vol. 48, no. 8, pp. 1509–1512, Aug. 2006. [5] J. Ollikainen, O. Kivekäs, A. Toropainen, and P. Vainikainen, “Internal dual-band patch antenna for mobile phones,” presented at the Proc. Millennium Conf. Antennas and Propagation, Davos, Switzerland, Apr. 9–14, 2000, Session 3A9. [6] M. Martinez-Vazquez and O. Litschke, “Quadband antenna for handheld personal communications devices,” in Proc. IEEE Antennas and Propagation Society Int. Symp., 2003, pp. 455–458. [7] K.-L. Wong and Y.-C. Lin, “Thin internal planar antenna for GSM/DCS/PCS/UMTS operation in PDA phone,” Microw. Opt. Technol. Lett., vol. 47, no. 5, pp. 423–426, Dec. 2005. [8] K. R. Boyle and P. J. Massey, “Nine-band antenna system for mobile phones,” Electron. Lett., vol. 42, no. 5, pp. 265–266, Mar. 2006. [9] V. Ermolov, H. Nieminen, K. Nybergh, T. Ryhänen, and S. Silanto, “MEMS for mobile communications,” Circuits Assembly, pp. 42–44, Jun. 2002. [10] T. G. S. M. Rijks, J. T. M. van Bee, M. J. E. Ulenaers, J. De Coster, R. Puers, A. den Defier, and L. van Teeffelen, “Passive integration and RF MEMS: A toolkit for adaptive LC circuits,” in Proc. 29th Eur. SolidState Circuits Conf., 2003, pp. 269–272. [11] T. G. S. M. Rijks, J. T. M. van Beek, P. G. Steeneken, M. J. E. Ulenaers, J. De Costes, and R. Puers, “RF MEMS tuneable capacitors with large tuning ratio,” in Proc. 17th IEEE Int. Conf. on Micro Electro Mechanical Systems, 2004, pp. 777–780. [12] T. G. S. M. Rijks, J. T. M. van Beek, P. G. Steeneken, M. J. E. Ulenaers, P. van Eerd, J. M. J. Den Toonder, A. R. van Dijken, J. De Coster, R. Puers, J. W. Weekamp, J. M. Scheer, A. Jourdain, and H. A. C. Tilmans, “MEMS tuneable capacitors and switches for RF applications,” in Proc 24th Int. Conf. on Microelectronics, 2004, vol. 1, pp. 49–56. [13] J. T. M. van Beek, M. H. W. M. van Delden, A. van Dijken, P. van Eerd1, A. B. M. Jansman, A. L. A. M. Kemmeren, T. G. S. M. Rijks, P. G. Steeneken, J. den Toonder, M. J. E. Ulenaers, A. den Dekker, P. Lok, N. Pulsford, F. van Straten, L. van Teeffelen, J. de Coster, and R. Puers, “High-Q integrated RF passives and RF-MEMS on silicon,” in Proc. Mat. Res. Soc. Symp., 2004, pp. B3.1.1–B3.1.12. [14] P. G. Steeneken, T. G. S. M. Rijks, J. T. M. van Beek, M. J. E. Ulenaers, J. De Coster, and R. Puers, “Dynamics and squeeze film gas damping of a capacitive RF MEMS switch,” J. Micromechan. Microeng., vol. 15, no. 1, pp. 176–184, Jan. 2005. [15] J. T. M. van Beek, P. G. Steeneken, G. J. A. M. Verheijden, J. W. Weekamp, A. den Dekker, M. Giesen, A. J. M. de Graauw, J. J. Koning, F. Theunis, P. van der Wel, B. van Velzen, and P. Wessels, “MEMS for wireless communication: Application, technology, opportunities and issues,” in Proc. MEMSwave2006, Jun. 2006, pp. 27–30. [16] T. G. S. M. Rijks, P. G. Steeneken, J. T. M. van Beek, M. J. E. Ulenaers, A. Jourdain, H. A. C. Tilmans, J. De Coster, and R. Puers, “Microelectromechanical tunable capacitors for reconfigurable RF architectures,” J. Micromechan. Microeng., vol. 16, no. 3, pp. 601–611, Mar. 2006. [17] A. J. M. de Graauw, P. G. Steeneken, C. Chanlo, J. Dijkhuis, S. Pramm, A. van Bezooijen, H. K. J. ten Dolle, F. van Straten, and P. Lok, “MEMS-based reconfigurable multi-band BiCMOS power amplifier,” in Proc. IEEE Bipolar/BiCMOS Circuits and Technology Meeting, to be published. [18] J. Kiriazi, H. Ghali, H. Ragaie, and H. Haddara, “Reconfigurable dualband dipole antenna on silicon using series MEMS switches,” in Proc. IEEE Antennas and Propagation Soc. Int. Symp., 2003, vol. 1, pp. 403–406.

BOYLE AND STEENEKEN: FIVE-BAND RECONFIGURABLE PIFA FOR MOBILE PHONES

[19] P. Panaia, C. Luxey, G. Jacquemod, R. Staraj, L. Petit, and L. Dussopt, “Multistandard reconfigurable PIFA antenna,” Microw. Opt. Technol. Lett., vol. 48, no. 10, pp. 1975–1977, Oct. 2006. [20] S. Onat, M. Unlu, L. Alatan, S. Demir, and T. Akin, “Design of a re-configurable dual frequency microstrip antenna with integrated RF MEMS switches,” in Proc. IEEE Antennas and Propagation Soc. Int. Symp., 2005, vol. 2A, pp. 384–387. [21] K. R. Boyle and L. P. Ligthart, “Radiating and balanced mode analysis of PIFA antennas,” IEEE Trans. Antennas Propag., vol. 54, no. 1, pp. 231–237, Jan. 2006. [22] K. R. Boyle, Y. Yuan, and L. P. Ligthart, “Analysis of mobile phone antenna impedance variations with user proximity,” IEEE Trans. Antennas Propag., vol. 55, no. 2, pp. 364–372, Feb. 2007. [23] P. J. Massey and K. R. Boyle, “Controlling the effects of feed cable in small antenna measurements,” in Proc. 12th Int. Conf. on Antennas and Propagation, 2003, pp. 561–564.

Kevin R. Boyle (M’05) was born in Chelmsford, England, on January 23, 1966. He received the B.Sc. degree (Hons.) in electrical and electronic engineering from City University, London, U.K., in 1989, the M.Sc. degree (with distinction) in microwaves and optoelectronics from University College, London, U.K., in 1997, and the Doctor of Technology degree from Delft University of Technology, Delft, The Netherlands, in 2004. He was with Marconi Communications Systems Ltd., Chelmsford, U.K., until 1997 working on all as-

3309

pects of antenna system design. He joined Philips Research Laboratories, Redhill, U.K., in 1997 (part of which became NXP Semiconductors Research in 2006) where he is currently a Principal Research Scientist and a Project Leader for antenna and propagation related activities. His areas of interest include antenna design for mobile communication systems, diversity, propagation modeling and related areas of mobile system design. He has published 25 papers in refereed international journals and conferences and holds sixteen patents. Dr. Boyle is a Chartered Engineer in London, U.K. He is a member of the Institution of Engineering and Technology (IET), London, U.K. He has actively participated in COST 259 and COST 273.

Peter G. Steeneken was born in Groningen, The Netherlands, in 1974. From 1996 to 2002, he studied magnetic and superconducting materials using optical and electron spectroscopy. He received the M.Sc. (cum laude) and Ph.D. degrees in experimental physics from the University of Groningen, Groningen, The Netherlands. He joined Philips Research in 2002, where he investigated microelectromechanical systems (MEMS). In 2006, he joined NXP Semiconductors Research, Eindhoven, The Nethelands, and became Project Leader of the RF MEMS research project. His current interests include the design, simulation, reliability and characterization of RF MEMS switches.

A Five-Band Reconfigurable PIFA for Mobile Phones - IEEE Xplore

PLANAR inverted F antennas (PIFAs) are widely used in mobile phones [1]–[8]. This is primarily because they ex- hibit an inherently low specific absorption rate ...

3MB Sizes 16 Downloads 230 Views

Recommend Documents

Low SAR, Five-Band MEMS Switched PIFA For Mobile ... - IEEE Xplore
Future mobile phones will be required to operate in the five bands shown in Fig. 1. Operation is only required in one band at a time, so a small antenna can be switched to operate over a number of narrow bands. However, to achieve this over a total b

TechWare: Mobile Media Search Resources - IEEE Xplore
Jun 15, 2011 - es on mobile media search, which has enjoyed rapid ... device for all our social, business, and ..... ing algorithms in Java for data mining tasks.

Secure Mobile Ad hoc Routing - IEEE Xplore
In mobile ad hoc networks (MANETs), multi-hop mes- sage relay is the common way for nodes to communicate and participate in network operations, making ...

Stable Topology Control for Mobile Ad-Hoc Networks - IEEE Xplore
Abstract—Topology control is the problem of adjusting the transmission parameters, chiefly power, of nodes in a Mobile. Ad Hoc Network (MANET) to achieve a ...

IEEE Photonics Technology - IEEE Xplore
Abstract—Due to the high beam divergence of standard laser diodes (LDs), these are not suitable for wavelength-selective feed- back without extra optical ...

wright layout - IEEE Xplore
tive specifications for voice over asynchronous transfer mode (VoATM) [2], voice over IP. (VoIP), and voice over frame relay (VoFR) [3]. Much has been written ...

Device Ensembles - IEEE Xplore
Dec 2, 2004 - time, the computer and consumer electronics indus- tries are defining ... tered on data synchronization between desktops and personal digital ...

wright layout - IEEE Xplore
ACCEPTED FROM OPEN CALL. INTRODUCTION. Two trends motivate this article: first, the growth of telecommunications industry interest in the implementation ...

Evolutionary Computation, IEEE Transactions on - IEEE Xplore
search strategy to a great number of habitats and prey distributions. We propose to synthesize a similar search strategy for the massively multimodal problems of ...

Mobile Camera Identification Using Demosaicing Features - IEEE Xplore
School of Electrical and Electronic Engineering. Nanyang Technological University. Singapore [email protected]. Abstract—Mobile cameras are typically ...

I iJl! - IEEE Xplore
Email: [email protected]. Abstract: A ... consumptions are 8.3mA and 1.lmA for WCDMA mode .... 8.3mA from a 1.5V supply under WCDMA mode and.

A New Outer Bound for the Gaussian Interference ... - IEEE Xplore
Wireless Communications and Networking Laboratory. Electrical Engineering Department. The Pennsylvania State University, University Park, PA 16802.

Ubiquitous Robot: A New Paradigm for Integrated Services - IEEE Xplore
virtual pet modeled as an artificial creature, and finally the. Middleware which seamlessly enables interconnection between other components. Three kinds of ...

A New Parameter for UWB Indoor Channel Profile ... - IEEE Xplore
Abstract—This paper proposes a new parameter for identifying the room typology when the receiver is in ultra wideband. (UWB) indoor environments.

a generalized model for detection of demosaicing ... - IEEE Xplore
Hong Cao and Alex C. Kot. School of Electrical and Electronic Engineering. Nanyang Technological University. {hcao, eackot}@ntu.edu.sg. ABSTRACT.

Gigabit DSL - IEEE Xplore
(DSL) technology based on MIMO transmission methods finds that symmetric data rates of more than 1 Gbps are achievable over four twisted pairs (category 3) ...

IEEE CIS Social Media - IEEE Xplore
Feb 2, 2012 - interact (e.g., talk with microphones/ headsets, listen to presentations, ask questions, etc.) with other avatars virtu- ally located in the same ...

Grammatical evolution - Evolutionary Computation, IEEE ... - IEEE Xplore
definition are used in a genotype-to-phenotype mapping process to a program. ... evolutionary process on the actual programs, but rather on vari- able-length ...

Throughput Maximization for Opportunistic Spectrum ... - IEEE Xplore
Abstract—In this paper, we propose a novel transmission probability scheduling scheme for opportunistic spectrum access in cognitive radio networks. With the ...

SITAR - IEEE Xplore
SITAR: A Scalable Intrusion-Tolerant Architecture for Distributed Services. ∗. Feiyi Wang, Frank Jou. Advanced Network Research Group. MCNC. Research Triangle Park, NC. Email: {fwang2,jou}@mcnc.org. Fengmin Gong. Intrusion Detection Technology Divi

striegel layout - IEEE Xplore
tant events can occur: group dynamics, network dynamics ... network topology due to link/node failures/addi- ... article we examine various issues and solutions.

Digital Fabrication - IEEE Xplore
we use on a daily basis are created by professional design- ers, mass-produced at factories, and then transported, through a complex distribution network, to ...