A conceptual design for a microstrip phased array with monolithic microwave integrated circuit (MMIC) amplitude and phase controls is described. The MMIC devices used are 20 GHz variable power amplifiers and variable phase shifters recently developed by NASA contractors for applications in future Ka band advanced satellite communication antenna systems. The proposed design concept is for a general NxN element array of rectangular lattice geometry. Subarray excitation is incorporated in the MMIC phased array design to reduce the complexity of the beam forming network and the number of MMIC components required. The proposed design concept takes into consideration the RF characteristics and actual phyical dimensions of the MMIC devices. Also, solutions to spatial constraints and interconnections associated with currently available packaging designs are discussed. Finally, the design of the microstrip radiating elements and their radiation characteristics are examined

Acosta, R.

Lee, R. Q.

Smetana, J.

English

NASA Technical Reports Server

NASA Technical Memorandum 88834
h DesignConceptfor an MMIC
Microstrip Phased Array
Richard Q. Lee, Jerry Smetana, and Roberto Acosta
Lewis Research Center
Cleveland, Ohio
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CSCL 20N
G 3/3 2
N87-145c9
Prepared for the
1986 Antenna Applications Symposium
cosponsored by the University of Illinois
and the Rome Air Development Center
Monticello, Illinois, September 17-19, 1986
https://ntrs.nasa.gov/search.jsp?R=19870005136 2020-03-20T12:19:31+00:00Z

A DESIGN CONCEPT FOR AN MMIC MICROSTRIP PHASED ARRAY
Richard Q. Lee, Jerry Smetana, and Roberto Acosta
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohio 44135
c_J
!
i,i
I. ABSTRACT
A conceptual design for a mlcrostrlp phased array with
monolithic microwave integrated circuit (MMIC) amplitude and
phase controls is described. The MMIC devices used are 20 GHz
variable power amplifiers and variable phase shlfters recently
developed by NASA contractors for applications in future Ka band
advanced satel'llte communication antenna systems. The proposed
design concept is for a general NxN element array of rectangular
lattlce geometry. Subarray excitation is incorporated in the
MMIC phased array design to reduce the complexity of the beam
forming network and the number of MMIC components required. The
proposed design concept takes into consideration the RF charac-
terlstlcs and actual physical dimensions of the MMIC devices.
Also, solutions to spatial constraints and Interconnectlons
associated with currently available packaging designs are
discussed. Finally, the design of the mlcrostrlp radiating
elements and their radiation characteristics are examlned.
2. INTRODUCTION
NASALewis Research Center has an on-golng program to
develop monolithic microwave integrated circuit (MMIC)devices
for satellite communication applications in the 20 and 30 GHz
frequency bands. In parallel with this activity, research
efforts have been focused on the development of active phased
array technology making use of these MMICdevices. The advan-
tages of active phased arrays with amplitude and phase control
at each radiating element or subarray are well known. In
addition to electronic beamsteering at nanosecondswitching
speed, an MMICphasedarray can provide adaptive nulllng of
interfering signals and dynamic compensation of a distorted
wavefront, l To investigate and demonstrate the feasibility of
MMICphased array concepts, NASALewis is currently developing
an MMICphased array feed system using horn radiators and wave-
guide beam-formlng networks with the MMICdevices placed inside
wavegulde houslngs.2 An active phasedarray with MMICdevices
in wavegulde housings, however, does not offer any significant
improvement in weight, size, and cost advantages. Recent
research efforts on MMICphased array have led to multi-layer
planar structure design concepts where the radiating elements,
MMICdevices, RFpower distribution and logic control networks
3
are deposited on different substrate layers. To our know-
ledge, a total system integration based on such design concepts
2
has not yet been realized to date. This paper discusses some
considerations and constraints relating the MMIC mtcrostrlp
phased array designs. Based on these considerations, a con-
ceptual design for a MMIC phased array composed of modular
mlcrostrlp subarray is proposed.
3. ARRAY DESIGN CONSIDERATIONS
Some considerations In active phased array designs are
spatial constraints, Interconnectlons, heat dissipation, and
cost. At hlgh frequency, the physical slze of the mlcrostrlp
antenna Is generally too small to allow direct amplitude and
phase control at each element. Wlth the currently available
PaCkaging designs for the 20 GHz transmitting module as depicted
In figure l, the overall dimensions of the MMIC devices are
larger than a single mlcrostrlp patch element. If MMIC devices
were placed at each element, the element spacing would be large,
and grating lobes would be generated. The spatial constraint may
require the use of modular subarray as radiating elements. When
an active phased array requires thousands of radiating elements,
cost Is an overriding factor 4 due to low production yields and
high costs for the RF characterization of MMIC devices. The
design concept developed by NASA Lewis uses modular subarray
instead of individual radiating elements. The subarray modular
approach reduces the cost and the complexity of the beam-formlng
network by reducing the number of MMIC devices required.
3
Another crltlcal Issue ts that of heat removal. The pro-
Jected efficiency for a power amplifier Is typically less than
20 percent. The MMIC devlces on substrate boards often generate
excess heat causing warping and device malfunctions. To prevent
excessive heatlng, MMIC devices are placed on separate substrate
boards and proper thermal heat stnks for the MMIC devices are
provlded.
The multi-layer design approach requlres very precise board
a11gnment in electrically connecting several layers containing
radiating elements, logic control circuit and beam-forming net-
work. The lnterconnectlon of large quantltles of NNIC devices
and mlcrostrlp patch elements pose formidable topology and mutual.
coupllng problems In active phased array designs. The complexity
of high-level Integration requlres Innovative feeding technique
and proper choices of array architecture and beam-forming network
deslgn. Electromagnetic coupllng techniques and optical beam-
forming network concepts are currently betng considered by NASA
5
Lewis as viable approaches to these problems.
4. ARRAY DESIGN CONCEPT
Flgure 2 shows a design concept of an NMIC mlcrostrlp phased
array. The MNIC amplitude and phase control modules are mounted
on a small rectangular substrate panels with RF power and logic
control lines extending to the edges. The panels are inserted
vertically lnto a properly designed bracket connecting the
4
radlattng element layer to the RF power distribution layers at
both ends. N_th MMIC devtces mounted on lndlvldual substrate
panels, the proposed array conftguratlon allows device character-
lzatlon as well as easy replacement of faulty devtces. Further-
more, the existence of large spacing between adjacent MMIC panels
alleviates heat dlsslpatlon difficulties. A thermal sink ls
generally requlred for multiple beam operations where several
sets of amplitude and phase controls are placed on the same
substrate panel. Figure 3 Illustrates a scheme for heat removal
qslng graphlte aluminum (GR/AL) heat pipe. GR/AL Is a composite
materlal w_th the property of lightweight, low coefficient of
thermal expansion and high thermal conductlvlty. NASA Lewis Is
currently supporting development of such materlal for space
applications.
The spatial and _nterconnect problems dellneates the cholce
• of subarray-type conflguratlon. Figure 4 shows four modular sub-
array configurations currently under Investigation. Subarray (a)
ls a corporate fed 2 by 2 rectangular subarray. Subarray con-
figurations b, c, and d all have a driven center element and
surrounding parasitic elements. The parasitic subarray conflg-
uratlons have the potential advantages of lower feed losses,
reduced feed 11ne radiation, lower s_delobes, and Increased
bandwidth. 6 Experimental Investigations are belng carried out
to study the clrcult and radiation characterlstlcs of these
5
subarray configurations. Figure S shows the typical radiation
patterns of a 2 by 2 rectangular subarray and a 3 by 3 parasitic
subarray along wlth that of a single mlcrostrlp patch.
The use of electromagnetic coupling between the feed llne
and the radiating element through an aperture wlll greatly
simplify the interconnect problem. An aperture-coupled micro-
strip antenna wlth a perpendicular feed has been investigated and
proven feaslble. 7 Thls technique Is particularly attractive
for use In the excitation of the parasitic subarrays. However,
further study and investigation is required to improve the
coupling efficiency.
5. CONCLUSION
A conceptual design for a mlcrostrlp phased array wlth cur-
rently available MMIC amplitude and phase control devices has
been described. The proposed design addresses the problems of
spatial constraints, Interconnectlons and heat removal. Although
the hardware and fabrication techniques for the MMIC phased array
system may already exist, much work still needs to be done to
reduce the complexity of MMIC control and lnterconnectlvlty while
achieving good performance.
REFERENCES
1. Acosta, R.J., (1986) "Compensation of Reflector Surface
Distortions Using Conjugate Field Matching," In IEEE 1986
Antennas and Propagation, International Symposium Digest,
Vo]. 1, IEEE, New York, pp. 259-263.
, Smetana, 3., Kascak, T.3., and Alexovlch, R.E., (1986) MMIC
Antenna Technoloqy Development in the 30/20 Gigahertz Band,
NASA TM-B?192.
3. Malloux, R.3., (1986) Phased Array Architecture for
Millimeter Wave Active Arrays, Microwave 3., 29:117-124.
4. Schell, A.C., (1986) Trends In Phased Array Development,
Microwave J., 29:26-35.
o Kunath, R.R. and Bhasln, K.B., (1986) Optlcally Controlled
Phased Array Antenna Concepts Using GaAs Monolithic
Microwave Integrated Circuits, NASA TM-87229.
, Lo, Y.T., et al, (1986) Study of Mlcrostrlp Antennas,
Mlcrostrlp Phased Arrays and Mlcrostrlp Feed Networks,
(RADC-TR-T7-406) UILU-ENG-77-2265.
o Buck, A.C., Pozar, D.M., (1986) Aperture-Coupled Mlcrostrlp
Antenna With a Perpendicular Feed, Electron. Lett.,
22:125-126.
ORtGINAL PAGE iS
c_ Poor QUALnY
_ r- .JP"
FIGURE 1. - PACKAGING DESIGNS FOR 20 GHz MMIC DEVICES.
PACKAGE
RF DISTRIBUTION
LAYER
t
ANTENNA LAYER
AND
MMIC CHIP
SUBARRAY
,_IGIJ,{E 2. - ill'lie MICROST.TIP PHASED A_RAY COIlFIGJ,_ATIOII.
ETCHED
COPPER
:LAED_:_Ns_-" I U
!,
ul
Ul
J OVERALL
HEIGHT
rU'.fir J_k
HEAT DISSIPATION
VPA (VARIABLE POWER
AMPLIFIER) - 0.5 W
VPS (VARIABLE PHASE
SHIFTER) - 0.5 W
CGA (CONSTANT GAIN
AMPLIFIER) - 1.3 W
l/ HEAT PIPE
FIGURE 3. - CONCEPT FOR HEAT REt'IOV_'_L USING GR/_L HEAT PIPE.
x FEED
D F--I[_
F--IF-I[Z]
F-IED
[Z]F-l
[Z]F-IEZ]
F--I[Z]
I
[fin
N_N
SN
(C) 7 ELEMENT PARASITIC. (D) 7 ELEMENT PARASITIC,
FIGURE q, - SUBARRAY CONFIGURATIONS.
1o
20
3o
o
lO
2O
3O
40
0 I
lO
2o
3o
I I I I I I I I I I
4o I i I I I I I I I I
-I00-80 -60 -40 -20 0 20 40 60 80 I00
ROTATION, DEG
(C) SINGLE MICROSTRIP ANTENNA.
F[GURE 5. - E PLANE RADIATION PATTERNS.
1. Report No.
NASA TR-88834
4. Title and Subtitle
!2. Government Accession No. 3. Recipient's Catalog No.
5. Report Date
A Design Concept for an MMIC Mlcrostrtp Phased Array
7. Author(s)
Richard Q. Lee, 3erry Smetana, and Roberto Acosta
9. Performing Organization Name and Address
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohlo 44135
12. Sponsoring Agency Name and Address
Natlonal Aeronautics and Space Administration
Washington, D.C. 20546
6. Performing Organization Code
506-58-22
8. Performing Organization Report No.
E-3213
10. Work Unit No.
11. Contract or Grant No.
13. Type of Report and Period Covered
Technical Memorandum
14. Sponsoring Agency Code
15. Supplementary Notes
Prepared for the 1986 Antenna Applications Symposium cosponsored by the
University of Illlnols and the Rome Air Development Center, Monticello,
Illinois, September 17-19, 1986.
16. Abstract
A conceptual design for a mlcrostrtp phased array with monolithic microwave
integrated circuit (MMIC) amplitude and phase controls ts described. The RMIC
devices used are 20 GHz variable power amplifiers and vartable phase shtfters
recently developed by NASA contractors for applications In future Ka band
advanced satellite communication antenna systems. The proposed design concept
Is for a general NxN element array of rectangular lattice geometry. Subarray
excitation ls incorporated In the MMIC phased array design to reduce the com-
plexity of the beam forming network and the number of MMIC components required.
The pFoposed deslgn concept takes Into consideration the RF characteristics and
actual physical dlmenslons of the MMIC devices. Also, solutions to spatial
constraints and lnterconnectlons associated with currently available packaging
deslgns are discussed. Finally, the design of the mtcrostrlp radiating elements
and their radiation characteristics are examined.
17. Key Words (Suggested by Author(s))
MRIC Rlcrostrlp phased array
Phased array design
18. Distribution Statement
Unclassified - unllmlted
STAR Category 32
19. Security Classif. (of this report)
Unclasslfled
_. S_udty Classif, (of this page)
Unclassified
21. No. of pages 22. Pdce °
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