NASA/CR--2001-210889

Reconfigurable Array Antenna Using

Microelectromechanical Systems

(MEMS) Actuators

Rainee N. Simons

Dynacs Engineering Company, Inc., Brook Park, Ohio

Donghoon Chun and Linda P.B. Katehi

University of Michigan, Ann Arbor, Michigan

Prepared for the

2001 AP-S International Symposium and USNC/URSI National Radio Science Meeting

sponsored by the Institute of Electrical and Electronics Engineers

Boston, Massachusetts, July 8-13, 2001

Prepared under Contract NAS3-98008

National Aeronautics and

Space Administration

Glenn Research Center

April 2001
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RECONFIGURABLE ARRAY ANTENNA USING

MICROELECTROMECHANICAL SYSTEMS (MEMS) ACTUATORS

Rainee N. Simons

Dynacs Engineering Company, Inc.

NASA Glenn Research Center

21000 Brookpark Road, Mail Stop 54-8

Cleveland, Ohio 44135

Donghoon Chun and Linda P.B. Katehi

University of Michigan

Radiation Laboratory, EECS Department

Ann Arbor, Michigan 48109-2122

Abstract: The paper demonstrates a patch antenna integrated with a novel microelectromechanical

systems (MEMS) actuator for reconfiguring the operating frequency. Experimental results

demonstrate that the center frequency can be reconfigured by as much as 1.6 percent of the nominal

operating frequency at K-Band. In addition, a novel on-wafer antenna pattern measurement technique

is demonstrated.

I. INTRODUCTION

Recently there has been tremendous interest in planar antennas capable of dynamically reconfiguring the

radiation pattern to provide horizon-to-horizon scan coverage over a wide frequency range, through

geometric reconfiguration [1]. These capabilities are possible through the use of microelectromechanical

systems (MEMS) based switching and actuating devices or circuits. The MEMS devices offer the

following advantages over semiconductor devices first, significant reduction in insertion loss. Second,

they consume insignificant amount of power during operation. Third, higher linearity hence lower signal

distortion. Typical examples of MEMS based antennas are reported in [2], [3], and [4].

In this paper, we present a new frequency reconfigurable patch antenna via use of integrated

microelectromechanical systems (MEMS) actuators. The key features of this approach is, that it does not

increase the antenna element dimensions, thus allowing for use in planar phased arrays. Second, each

actuator requires only a single bias line for control, which implies greatly simplified construction and

operation. In addition, the paper also demonstrates a novel on-wafer pattern measurement technique. The

advantage of this technique is that there is no need to dice and separate the individual antennas on the

wafer, thus resulting in tremendous savings in cost and time.

II. MEMS ACTUATOR DESIGN AND FABRICATION

A Patch antenna with two independent MEMS actuators is illustrated in Fig. 1. The antenna is fabricated

on high resistivity silicon wafer (¢, = 11.7, h = 400_m) with spin-on-glass (SOG) (¢rl = 3. l, hi _ 1.51am)

as the dielectric support layer. Each actuator consists of a moveable metal overpass suspended over a

metal stub and supported at either ends by metalized vias which are electrically connected to the patch

antenna. The metal strip of length L and width W attached to the metal stub behaves as a parallel plate

capacitor. The patch antenna operates at its nominal frequency as determined by the dimension b when

the actuator is in the OFF state. The actuator is in the ON state when the overpass is pulled down by the

electrostatic force due to the bias, and the capacitance of the metal strip appears in shunt with the input

impedance of the patch antenna. This capacitance tunes the patch to a lower operating frequency.

NASA/CR--2001-210889 1
III. EXPERIMENTAL RESULTS AND DISCUSSIONS

The measured return loss for the two states of the actuators are shown in Fig. 2. When both the actuators

arc in the OFF state, the patch resonates at its nominal operating frequency (f0) of about 25.0 GHz. When

both actuators are in thc ON state, the fON is 24.6 GHz. The 400 MHz shift is about 1.6 percent of f0.

To measure the E- and H-plane radiation patterns of the patch antenna, the RF probe station is modified to

accommodate a small horn antenna. The horn antenna is attached to a Plexiglas TM fixture and is driven

along an arc by a stepper motor. Thus the horn can measure the relative field intensity of the patch as a

function of the angle from boresight. The experimental setup is shown in Fig. 3. The measured E- and

H-plane radiation patterns are shown in Fig. 4. At thc present time, these actuators are being integrated

into a 2x2 patch antenna array shown in Fig. 5. The array characteristics will be presented at the

symposium.

IV. CONCLUSIONS

A novel frequency reconfigurable patch antenna with integrated MEMS actuators is presented for the first

time. This patch can be dynamically reconfigured to operate at frequencies separated by about 1.6 percent

of the nominal operating frequency. In addition, a novel on-wafer antenna pattern measurement technique

is demonstrated.

REFERENCES

[1] J.K. Smith, "Reconfigurable Aperture Program (RECAP) - MEMS Revolutionary Impact on RF

Systems," Workshop Notes: RF MEMS for Antenna Applications, 2000 IEEE Ant. and Prop. Inter.

Symp., Salt Lake City, UT, July 16, 2000.

[2] D. Chauvel, et al., "A Micro-Machined Microwave Antenna Integrated with its Electrostatic Spatial

Scanning," Proc. IEEE Tenth Annual Inter. Workshop on Micro Electro Mechanical Systems (MEMS

97), pp. 84-89, Nagoya, Japan, Jan. 26-30, 1997.

[3] J.-C. Chiao, et al., "MEMS Reconfigurable Vee Antenna," 1999 IEEE MTT-S Inter. Microwave

Symp. Dig., vol. 4, pp.1515-1518, Anaheim, CA, June 13-19, 1999.

[4] C. Bozler, et al., "MEMS Microswitch Arrays for Reconfigurable Distributed Microwave

Components," 2000 IEEE Ant. and Prop. Inter. Symp., Dig., Vol. 2, pp. 587-591, Salt Lake City, UT,

July 16-21, 2000.

_f

("

,, _-- Metal strip r- Moveable

i, ', and stub '_ overpass

, i i jifol. ' _,' ::_:_:: ..... :- _ ._ Via

[ ! hole

I

I L_ DC bias L_Dielectric i

[ pad film

,,_'_ MEMS ,L[ j__ j I ._,_Lllf

', actuator.- I I '1 l/ I .. , II lib

! Microstrip I _ a i[__ MEMS

! feed _-- I- ...... I actuator

! DC bias .-'_ ,__1

I pad _ -"

t_Patch i _-- G-S-G

antenna,

) RF probe

pads

Figure 1.-Frequency reconfigurable patch antenna element with two independent

MEMS actuators, L = 580 _m, W = 50 lam, a = 2600 _m, b = 1500 tam.

NASA/CR--2001-210889 2
0

n_

E -lz

r_

-18

R

,- Both actuators OFF

/

/

/ /- Both actuators ON

1 i t I I

23.50 23.96 24.42 24.88 25.34 25.80

Frequency, GHz

Figure 2.- Measured return loss demonstrating frequency

reconfigurability with integrated MEMS actuators while

maintaining good impedance match.

Swivelable

microscope

Figure 3.- Computer controlled on-wafer radiation pattern measurement

set-up for MEMS actuator based patch antennas (surrounding microwave

absorber panels have been removed).

NASA/CR--2001-210889 3
rm

d

-10

,B

Q.

E

tO

-20

- 30

- /r- _'- E-plane

;,.

I 1 I I 1 I

- 90 - 60 - 30 0 30 60 90

Angle, deg

Figure 4.- Measured E and H-plane radiation patterns

of the patch antenna.

Figure 5.-

I---MEMS

actuator

--- Patch

antenna

Microstrip

feed network

-,*- DC bias

lines

__ P G-S-G RF

probe pads

Schematic showing a 2x2 patch antenna array with MEMS actuators and

DC bias line for control.

NASA/CR--2001-210889 4

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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE

April 2001

4. TITLE AND SUBTITLE

Reconfigurable Array Antenna Using Microelectromechanical

Systems (MEMS) Actuators

6. AUTHOR(S)

Rainee N. Simons, Donghoon Chun, and Linda P.B. Katehi

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

Dynacs Engineering Company, Inc.

2001 Aerospace Parkway

Brook Park, Ohio 44142

9. SPONSORINCVMONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

3. REPORT TYPE AND DATES COVERED

Final Contractor Report

5. FUNDING NUMBERS

WU-755-O8-OB-00

NAS3-98008

8. PERFORMING ORGANIZATION

REPORT NUMBER

E- 12645

10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

NASA CR--2001-210889

11. SUPPLEMENTARY NOTES

Prepared for the 21301 AP-S International Symposium and USNC/URSI National Radio Science Meeting sponsored by the Institute of

Electrical and Electronics Engineers, Boston, Massachusetts, July 8-13, 2001. Rainee N. Simons, Dynacs Engineering Company, Inc.,

2001 Aerospace Parkway, Brook Park, Ohio 44142; Donghoon Chun and Linda EB. Katehi, University of Michigan, Radiation

Laboratory, EECS Department, Ann Arbor, Michigan 48109-2122. Project Manager, Erick N. Lupson, Office of Acquisition,

NASA Glenn Research Center, organization code 0616, 216--433-6538.

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Available electronically at htto://zltrs._c.nasa._ov/GLTRS

This publication is available from the NASA Center for AeroSpace Information, 301--621-0390.

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

The paper demonstrates a patch antenna integrated with a novel microelectromechanical systems (MEMS) actuator for

reconfiguring the operating frequency. Experimental results demonstrate that the center frequency can be reconfigured by

as much as 1.6 percent of the nominal operating frequency at K-Band. In addition, a novel on-wafer antenna pattern

measurement technique is demonstrated.

14. SUBJECT TERMS

Microelectromechanical systems; MEMS; Antenna; Patch; Array

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