This article has been accepted for publication in a future issue of this journal, but has not been

fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TAP.2019.2900438, IEEE
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A Dual-Polarization Switched Beam Patch Antenna Array for Millimeter-Wave

Applications
Kirill Klionovski, Mohammad S. Sharawi, Senior Member, IEEE, and Atif Shamim, Senior Member, IEEE

Abstract—Increasing data transfer rates for future millimeter-wave polarization mode through the second separate BFN and radiating
communications require high capacity radio channels and user-centric elements that support dual-polarization mode. Some designs of mm-
communication network environments. Therefore, special requirements,
such as wide-angle beam steering, wide operational frequency bandwidth
wave antenna arrays based on single layer BM BFN were reported
and simultaneous operation with orthogonal polarizations are essential recently in [9-16]. A comparison of important parameters such as
for telecommunication antennas. In this paper, we present a compact practical implementation of BFN, impedance BW, polarization,
patch antenna array with a Butler matrix feed network for the frequency electrical size, efficiency and beam switching angle range has been
band of 26–31.4 GHz. The 16-element planar array has been designed to
operate with two linear orthogonal polarizations and provide ±42º beam TABLE I
switching. To ensure wideband operation, a novel combination of planar COMPARISON OF BUTLER MATRIX BASED ANTENNA ARRAYS
couplers, crossovers and phase shifters is designed to form the Butler Paper BFN Pol Size, f 0, BW, Eff, SLL BSR
matrix. A new phase shifter topology is used which is based on a type λ GHz % % dB
combination of open-short stubs and Shiffman phase shifter. The design [6] M DL NA 10 6 51 6 ±38º
is fabricated on a low-cost multi-layer board with a size of 120x70x1.62
[7] M DC NA 7.83 15 NA 8 ±40º
mm3. The size of the feeding network, which is implemented on a single
[8] M DC NA 1.58 8 NA 6.5 ±45º
board, is 76x23x0.1 mm3. Experimental measurements of return loss,
2.2 9 NA ±42º
mutual coupling and radiation patterns confirm simulated results.
[9] M L NA 43 NA NA 7 ±31º
Index Terms—Millimeter-wave antenna array, wideband antenna [10] M L 2.4x2 62.4 8.5 NA 8 ±40º
array, Butler matrix. [11] M L NA 60.5 11.5 NA 5 ±40º
[12] M L 2.75x2.5 61 13.5 NA 7 ±40º
I. INTRODUCTION [13] M L 2x2 60.2 11.6 NA 7 ±40º
[14] SIW L NA 61 11.5 NA 8 ±41º
Future wireless telecommunication standards are expected to
[15] SIW L 6x2.5 30 13.3 NA 7.5 ±51º
address the increasing demand in bandwidth (BW) and higher data
[16] M L 2.5x5 27.9 2 NA 6.5 ±32º
transfer rates and will operate at millimeter-wave (mm-wave) This M DL 2.4x 1.9 28.7 19 36 8 ±42º
frequency bands. For example, future Local Multipoint Distribution work
Service (LMDS) standard promises to cover the following bands:
27.5-28.35, 29.1-29.25, and 31-31.3GHz [1], therefore, operational BFN type - microstrip (M) or Substrate integrated waveguide (SIW)
BW covering all the bands is more than 13%. Also, the implementation of BM BFN; Pol - operating polarizations: dual linear (DL),
telecommunication standards require adaptive antenna arrays that are dual circular (DC), or linear (L); Size - overall size of BFN in fractions of
center operating wavelength (λ); f0 – central operation frequency; Eff -
capable of wide-angle beam steering [2, 3] to provide optimal speeds
efficiency; and beam switching angles range (BSR).
for devices, thereby creating a user-centric environment. If these
arrays can operate with two orthogonal linear polarizations, the done in Table I. From the comparison, we can see that antenna arrays
channel capacity can be enhanced and thus the spectral efficiency of with BM BFN published in [7, 12, 15] can cover 13% impedance
communication links can be boosted. BW, but all those BFN designs are characterized by huge amplitude
Designing an antenna that operates with two orthogonal linear (>4 dB) and phase (>20º) imbalances, as well as low isolation (<12
polarizations and provides beam-steering with a BW of more than dB) between output ports of the BFN inside the operational
13% is quite challenging. For beam steering, there are two popular impedance BW. Such imbalances and isolation lead to asymmetrical
choices, (1) an active antenna array, and (2) a switched-beam beams with increased SLL, thus making the steering angle range
antenna array. Although active components for millimeter-wave narrower. Therefore, we are interested not only to get wide
adaptive antenna arrays are commercially available [4, 5], the use of operational impedance BW, but also to get stable radiation patterns
switched-beam antennas based on a beamforming network (BFN), at all operation frequencies.
such as Butler matrix (BM) or Rotman lens, can be a cheaper In this paper, we present a novel switched-beam planar patch
alternative at the cost of a larger size. antenna array with dual polarization for future mm-wave
In recent years, some designs of dual-polarized antenna arrays applications. The beam switching is achieved through the use of a
with BM BFN were reported in [6-8]. Those designs consist of two wideband BM. The wideband operation covering 26-31.4 GHz is
separate BM BFN for each polarization. Therefore, a single achieved by using novel wideband crossovers, couplers and phase
polarized antenna array with BM BFN can be extended to a dual- shifters along with dual-fed superstrate loaded radiating patches. The
planar patch antenna array consists of 16 elements (in 4 x 4
This publication is based upon work supported by the King Abdullah
arrangement). Such arrangement is chosen to get the highest antenna
University of Science and Technology (KAUST) Office of Sponsored area efficiency for a massive multiple-input multiple-output (MIMO)
Research (OSR) under Award No. OSR-2016-KKI-2899. system [17]. Good agreement is achieved between the simulated and
K. Klionovski and A. Shamim are with the King Abdullah University of measured results. The antenna array demonstrates beam switching
Science and Technology (KAUST), Thuwal, 23955-6900, Kingdom of Saudi for angles of ±42º with a maximum gain of 12 dBi and 19% BW.
Arabia (e-mail: kirill.klionovski@kaust.edu.sa, atif.shamim@kaust.edu.sa).
M. S. Sharawi was with King Fahd University of Petroleum and Minerals
The obtained 8 dB SLL is comparable with the published designs
(KFUPM), Dhahran, Saudi Arabia. Now he is with the Department of and is sufficient for most mobile telecommunication system
Electrical Engineering, Poly-Grames Research Center, Polytechnique applications [3].
Montréal, Montréal, QC H3T 1J4, Canada (e-mail:
mohammad.sharawi@polymtl.ca).

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II. ELEMENTS OF THE ANTENNA ARRAY where p is an empirical constant ranging from 0.56 to 0.6; ε is the
A typical scheme of a 4-beam Butler matrix contains four 3-dB permittivity of the coupler’s substrate; a is the length of the major
quadrature directional couplers, two crossovers, two 45 º and two 0º axis of an ellipse.
phase shifters. The purpose is to feed the neighboring antenna 2. When the eccentricity of an ellipse is e=1 (the case of a disk),
elements with equal amplitudes and equally varying phase shifts. only 10% impedance BW can be achieved. To get 20-25% BW, the
Different phase shifts appear when different ports are excited, and eccentricity should be chosen from the range of e=0.6…0.8.
that causes the beam to switch in different directions. Thus, 3. When the coupler is fed through a 50-Ω microstrip line, the feed
excitation of ports 1R, 1L and 2R, 2L lead to ±45 º and ±135º phase point should be located on a radial line of the ellipse which is
shift between the signals fed to neighboring antennas, respectively. oriented at an azimuthal angle of Ф=45º relative to the major axis of
As a result, any one of the four beams marked as 1R, 1L, 2R and 2L the ellipse. In the case of 50-Ω feeding, the impedance BW is less
in Fig. 1 can be achieved when the corresponding port is excited. than 15%. To increase the impedance BW up to 25%, the impedance
Many papers have previously been published on the topic of Butler of a microstrip feeding line should be decreased to 20-Ω. With
matrix, however most of these papers present multilayer designs (for decreasing value of the impedance, the azimuthal angle Ф should be
example, [18]) to increase the BW of the feeding network. In this increased to values of Ф=55…65º.
work, one of the targets is to make 5G base station antenna array We optimized the design for the band of 26-31 GHz. The
which is low-cost and that can be easily of manufactured. Due to this optimized design is based on the use of a Rogers Ultralam 3850
reason, we have employed a single layer planar design for Butler laminate, which has a permittivity of 2.9, loss tangent of 0.0025, and
matrix feed network. a thickness of 0.1 mm. We choose the parameters p=0.59 and a=3.83
A. The Design of The Wideband Quadrature 3-dB Directional mm in (1) to get resonance frequency of 27.1 GHz. According to the
Coupler recommendations mentioned above, we choose an eccentricity of
Some designs of planar wideband 3-dB quadrature directional
couplers have been previously published in [19, 20]. The common
disadvantage of such designs is the large size and the complicated
fabrication required to realize them. One of the simplest design of a
3-dB coupler, which can offer wide BW, is an elliptic-patch
quadrature-hybrid coupler (see Fig. 1a) [21, 22]. The advantages
include wide BW, small size and simple fabrication in a single-layer
implementation.
Although the design has been published previously, there are no
recommendations on the proper selection of both the ports’ positions
Fig. 2. The S-parameters of the coupler.
and the eccentricity of the ellipse to get the widest BW. We have
e=0.793 and a port angle of Ф=60º. The coupler is fed by a 20-Ω
microstrip line with a width of W=0.84 mm and a length of L=0.756
mm. However, to connect this coupler with the rest of the elements
in the Butler matrix, the width of this feed line must be changed to
achieve 50-Ω characteristic impedance. This can be clearly seen in
Fig. 1, where narrowing width (Ws=0.25 mm) of the feed line
ensures this transition from 20-Ω to 50-Ω. A 3-dB quadrature
directional coupler with these parameters was simulated, and the
simulated results demonstrate a phase imbalance of less than ±4º, an
amplitude imbalance of less than 0.4 dB, and an isolation that
exceeds 14 dBs in the frequency range of 26-31.5 GHz (Fig. 2).

B. The Design of The Wideband Crossover

A few designs of planar wideband crossovers, based on Lange
coupler [24], have previously been demonstrated in [22, 25, 26].
However, these designs are difficult to fabricate because of the
required electrical connections between different sections of the
Lange coupler. A simpler design from fabrication perspective is a
square patch with circular slots (see Fig. 1b) [27]. The wide
Fig. 1. (a) the wideband quadrature 3-dB directional coupler design and (b) operational band of the crossover is based on excitation of two
the wideband crossover design. resonances inside the square cavity. The first resonance is the
resonance of modes TM100 and TM010 of the square patch. The
performed a parametric optimization of the 3-dB quadrature elliptic second one is obtained by the circular slots.
coupler using simulations of the design in ANSYS Electromagnetic The design has been optimized for a Rogers Ultralam 3850
Suite V.17.2. The main conclusions of the optimization are laminate with a thickness of 0.1 mm for the band of 26-31 GHz. The
summarized as follows. length Lc is critical for the first resonance, and from (4) we calculate
1. Resonance frequency f of the coupler is given by the equation it to be 3.3 mm to get the first resonance at 26.7 GHz. The radius of
[23] for an elliptical patch antenna: the slot Rc and the widths W1=W2 help in achieving the second
3 108 p resonance. From simulations, Rc=1.3 mm and W1=W2=0.15 mm
f  ,
a  (1) have been obtained as the best values to place the second resonance
close to the first resonance. A crossover with these dimensions has

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Fig. 3. The S-parameters of the crossover.

been simulated. The simulated results (Fig. 3) show that the
crossover has an isolation of more than 15 dB and insertion loss of
less than 1.5 dB within the range of 26-31.5 GHz. Due to the
influence of the slot, we can see a slight shift (~3%) of the first
resonance from the calculated value. It can be shown that in the
absence of the slot, formula (4) gives very precise value of the
resonance frequency of a square crossover. It is also observed in Fig.
3, that isolated ports (2 and 4) do not have ideal isolation. This is due Fig. 5. (a) the open-short-stub phase shifter element geometry; (b) the
to some minor reflected currents going into those isolated ports. Shiffman phase shifter geometry; (c) the overall proposed wideband phase
Nonetheless, the isolation is below -15 dBs for the entire band of shifter geometry; (d) the single element patch antenna element geometry.
interest. (compared with a 50-Ω microstrip line) is shown in Fig. 4 (curve 2).
Thus a novel combination of two open-short-stub phase shifter
C. The Design of The Wideband Phase Shifter elements with the Shiffman phase shifter (Fig. 5c) provides the
As per the requirement of Butler matrix feeding network, phase required group delay ratio. This design allows to get a stable phase
shifters must provide stable (with low phase imbalance) 45º and 0º shift with low phase imbalance when the square patch crossover is a
phase shifts as compared to the signal coming from the wideband reference line.
crossover. Many previous phase shifter designs use a straight Following conclusions can be deduced from the design process.
transmission line as a reference. However, in the proposed Butler 1. The width W3 of the transmission line in the open-short stub
matrix implementation, the square crossover with slots has a group phase shifter must have a characteristic impedance of 25-35 Ω,
delay that is quite different from that of a straight transmission line. provided the interconnecting lines have a characteristic impedance of
The ratio of the group delay of the crossover to the group delay of a 50-Ω (represented by Ws in Fig. 5a). For the proposed design, W3
50-Ω microstrip line is shown in Fig. 4 (curve 1). From this figure, it =0.52mm which corresponds to 30-Ω.
2. The width of the transmission line W4 in the Shiffman phase
shifter is the same as the width W3. The gap width W5 should be 4-6
times smaller than the width W4. For the proposed design, W5
=0.1mm.
3. The widths Wo and Wt of the open and shorted stubs
respectively must adhere to an impedance ratio of ~3:1 to maximize
the operational BW and to reduce the phase variation below 10%.
For the proposed design, an impedance ratio of 2.7:1 has been
utilized, whereas Wo and Wt correspond to 62 and 23-Ω respectively.
Fig. 4. The group delay ratio.
4. The lengths Lo and Lt of the open and shorted stubs have been
can be seen that the group delay of the crossover is more than twice
of that of the microstrip line. Therefore, well-known wideband calculated by the formula
 8   
, where λ is the center
planar designs of Shiffman phase shifter [28], Lange coupler based wavelength of the operational frequency band, ε is the permittivity of
phase shifters [29, 30], or T-shaped open stub [31] and open-short the phase shifter’s substrate.
stub phase shifters [32] cannot be used in the proposed Butler matrix 5. The height Hps of the Shiffman phase shifter is critical to
design as they provide unit group delay ratio, whereas this particular achieve the required nominal of the phase shift.
crossover design requires 2.5 group delay ratio. Therefore, a new The final dimensions of 0º and 45º phase shifter elements are listed
design is required to achieve the required group delay ratio and in Table II. Phase shifter with the optimized dimensions has been
subsequently a stable phase shift over the entire BW. simulated and the results are shown in Fig. 6. It can be seen that the
In order to resolve the above-mentioned issue and achieve a low TABLE II
phase imbalance for the frequency range of 26-31 GHz, we have DIMENSIONS (IN MM) OF 0º AND 45º PHASE SHIFTERS
come up with a planar design of phase shifter which is a combination Phase
Lps Hps Wo Lo Wt Lt W3 D
of series connected elements. An open-short phase shifter (Fig. 5a) shift
can create stable phase shift (i.e. unit ratio of group delays) as 0º 4.7 4.11 0.18 0.84 0.75 0.74 0.52 0.2
compared with a 50-Ω microstrip line in the frequency band of more 45º 4.5 4.3 0.18 0.775 0.7 0.775 0.52 0.2
than 20%, as it has been shown in [32]. Series connection of two phase shifter has an insertion loss of less than 0.6 dB for the entire
such phase shifters gives us the ratio of group delays equal to 2. range of 26-31.5 GHz. Phase shift of the wideband phase shifter has
Additional group delay to get the required 2.35-2.6 ratio is possible been calculated by subtracting the phase of S13 (ports for the
through a Shiffman phase shifter (Fig. 5b), whose group delay ratio crossover) from phase of S56 (ports for the phase shifter). From Fig. 6

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board. Both, the second and third board, are based on Rogers
RO4533 laminate. Each board has a size of 70x120 mm2. The patch
inter-element spacing is 5.5 mm (0.57 wavelength for the frequency
of 31.4 GHz) in both X and Y-directions. The electrical contact
between the feeding network and the radiating patches is created by
metallized vias between the 1st and the 2nd board.

Fig. 6. The S-parameters of the phase shifter.

we can see that phase deviation of the phase shifter is less than ±5º
from the required 0º and 45º phase shifts for the entire frequency
range of 26-31.5 GHz. In the following section, with simulated and
measured results for a complete design of antenna array, we will
show that the ±5º phase deviation does not affect the BSR and the
SLL.

D. The Design of The Wideband Radiating Element

For this particular design, we need a wide band antenna element
that can support two orthogonal linear polarizations over the
frequency range of 26-31.5 GHz and have a broad radiation pattern.
One possible antenna that satisfies the requirements on dual- Fig. 8. (a) the boards’ view of 16-elements antenna array; (b) PCB stack up
polarization operational mode as well as broad radiation pattern is a view (h1=h2=0.76 mm, h3=0.1 mm).
rectangular or circular patch. But, such patch antennas can typically
For simultaneous operation with two orthogonal linear
provide less than 7% BW [23]. In the proposed patch design (a
polarizations, we feed the radiating patches by two identical
square patch antenna with semi-circular cut-outs) [33], as shown in
independent Butler matrices (Fig. 9 (a)). Each Butler matrix has four
Fig. 5d, can fulfill the large BW requirement. The patch antenna is in
ports to create four beams. Each output microstrip line from the
the form of a square plate of length Lp=2.65 mm that has angled
Butler matrix feeds a 4-element linear patch array via a power
circular cutouts of the radii Rp=0.95 mm. The radiating element and
divider (Fig. 9 (b)) with non-uniform amplitude distribution. The
the superstrate have been implemented on a Rogers RO4533
normalized amplitudes at the outputs of the power divider are:
laminate, which has a permittivity of 3.3, loss tangent of 0.0025, and
A2=A3=1, A1=A4=0.6. The non-uniform amplitude distribution is
a thickness of 0.76 mm. The patch is excited by two metallic pins
used to provide low SLL in the radiation pattern in the plane that is
with diameters of 0.416 mm, which are located at distances of 0.78
orthogonal to the plane of beam scanning. When ports 1-4 are
mm from the center of the patch (along the X and Y-axes), through
excited, the antenna array operates with main polarization of the
circular holes with a diameter of 1 mm in the metallic ground plane.
electrical field in the Y-direction. When ports 5-8 are excited, the
The simulated results for this patch antenna are shown in Fig. 7.
main polarization of electrical field is in the X-direction.
Due to symmetricity of the patch in ZX and ZY-planes, |S11|=|S22| and
|S12|=|S21|. From Fig. 7, we can see that the antenna is well matched
B. Simulated and Measured Results
for the desired frequency range and the isolation between the two
A prototype of the antenna array (Fig. 10) has been fabricated and
ports is better than 12 dB.

Fig. 7. The S-parameters of the patch element.

III. RESULTS AND DISCUSSIONS

A. The Design of The Antenna Array
A 16 elements antenna array has been designed which requires
three boards (Fig. 8). The 1st board, based on Ultralam 3850
laminate, contains the feeding network, the 2nd board has the planar
Fig. 9. (a) the feeding network of the dual-polarized antenna array; (b) the
16 element (4x4) radiating patches and the 3rd is the superstrate power divider.

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Butler matrix 1 (note that |S12|=|S21|, |S13|=|S31|, |S14|=|S41|). From this

figure, we can see that isolation is more than 15 dB for the working
frequency band. Measurements show that isolation between ports 2-
3, 2-4 and 3-4 is also more than 15 dB. Measured curves of isolation
between ports of Butler matrix 2 are similar to the curves of isolation
between ports of Butler matrix 1, therefore they are not shown in a
separate figure. Fig. 11 (c) shows isolation between ports of the
Butler matrixes 1 and 2. Isolation between ports 1-8, 2-7, 3-6 and 4-5
is better than 25 dB in the working frequency band. For other ports,
isolation between two Butler matrixes is more than 30 dB.
Fig. 12 shows the radiation patterns of the antenna array in the
XZ-plane at frequencies of 26, 28.5, and 31 GHz when different
ports are excited. The angle θ in the figure is measured from the Z-
axis. From Fig. 12 we can see that the directions of the main beam
are -42º (-42º), -13º (-13º), 13º (13º) and 42º (42º) when port 2 (6), 4
(8), 1 (5), and 3 (7) are excited, respectively. Maximum gain is 12
and 9 dBi for the beams with ±13º and ±42º main directions,
respectively. The SLL in XZ-plane is -10 and -8 dB for the beams
with ±13º and ±42º main directions, respectively. Due to non-uniform
Fig. 10. Photo of the fabricated prototype: (a) layer of radiating patches; (b)
layer of the feeding network. amplitude power dividers of the feeding network, the SLL in the YZ-
plane is at least 15 dB. Measurements show that the cross-
measured in a far field chamber. The fabrication process includes polarisation levels are 16 dB lower as compared to the maximum of
drilling vias in the 1st and the 2nd boards with subsequent the co-polarised patterns, for all ports inside the operating frequency
metallization of the vias. The final manufacturing is performed by band of 26-31.4 GHz.
bonding all the three boards using Rogers 4450F bondply with a From the simulated and measured results we can see that the
thickness of 0.1 mm as prepreg. The prototype is fed by mini-SMP proposed design of the antenna array demonstrates wide impedance
connectors. During the measurements, all unused connectors are BW as well as wide BW for stable beam steering.
loaded by 50-Ω terminations. Additional investigation has been performed on the efficiency of
Simulated and measured S-parameters (Snm; n˅m=1, 2, …, 8) of the array. This investigation shows that the efficiency is in the range
the array are presented in Fig. 11. From Fig. 11 (a), we can see that of 29-36% inside the operational frequency band. It is worth
the reflection coefficients for ports 1-4 are less than -10 dB for the mentioning here that the efficiency of a single radiating element is
frequencies of 26-31.4 GHz (the BW is 19%). The same BW we more than 90% inside the operational band [33]. Thus, the microstrip
obtain for ports 5-8. Fig. 11 (b) show isolation between the ports of feed network losses (~4 dB) at such high frequencies are responsible

Fig. 11. (a) reflection coefficients for ports 1-4; (b) isolation between ports Fig. 12. Radiation patterns of the antenna at the frequency of (a, b) 26 GHz;
1-2, 1-3, 1-4; (c) isolation between ports 1-8, 2-7, 3-6, 4-5. (c, d) 28.5 GHz; (e, f) 31 GHz.

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for such relatively low efficiency. array with integrated Butler matrix and GaAs amplifiers,” IEEE Trans.
Note that BFN has been realized in microstrip line implementation Microwave Theory Tech., vol. 60, no. 11, pp. 3599–3607, Nov. 2012.
[14] N. Tiwari and T. Rama Rao, “A Switched Beam Antenna Array with
that leads to its potential radiation and interference with electronics Butler Matrix Network Using Substrate Integrated Waveguide
placed behind the antenna array. To avoid the interference issue and Technology for 60 GHz Communications,” in Proc. Int. Conf. on
get high isolation, the BFN can be implemented as a stripline where Advances in Computing, Communications and Informatics (ICACCI),
an additional board with ground plane is added to the bottom of the Kerala, India, 2015, pp. 2152–2157.
board 1. Investigation of a stripline based BFN shows that it can [15] Qing-Ling Yang, Yong-Ling Ban, Kai Kang, Chow-Yen-Desmond Sim
and Gang Wu, “SIW Multibeam Array for 5G Mobile Devices”, IEEE
provide the same BW and coupling characteristics as its microstrip Access, vol. 4, pp. 2788-2796, June 2016.
counterpart, without distorting the radiation pattern. [16] A. T. Alreshaid, M. S. Sharawi, S. Podilchak, and K. Sarabandi,
“Compact millimeter-wave switched-beam antenna arrays for short
range communications,” Microwave and Optical Technology Letters,
IV. CONCLUSIONS vol. 58, no. 8, pp. 1917-1921, Aug. 2016.
[17] P. Pan, H. Wang, Z. Zhao, and W. Zhang, “How Many Antenna Arrays
In this paper, we propose the design of a 16-element antenna array Are Dense Enough in Massive MIMO Systems,” IEEE Trans. Vehic.
covering the bands 26-31.4 GHz, which operates with two Tech., vol. 67, no. 4, pp. 3042–3053, April 2018.
orthogonal linear polarizations and provides ±42º beam switching. [18] N. Sutton and D. S. Filipovic, “Design of a K- thru Ka-band modified
The antenna array is based on a Butler matrix feed network and Butler matrix feed for a 4-arm spiral antenna,” in Proc. 2010
Loughborough Antennas & Propagation Conf., Loughborough, UK,
wideband patch radiating elements. The Butler matrix design is Nov. 2010, pp. 521–524.
implemented by planar wideband crossovers, couplers and phase [19] C. Caloz, A. Sanada, and T. Itoh, “A Novel Composite Right-/Left-
shifters. The proposed design provides better operating bandwidth Handed Coupled-Line Directional Coupler With Arbitrary Coupling
among the published switched-beam Butler matrix based antenna Level and Broad Bandwidth,” IEEE Trans. Microwave Theory Tech.,
array designs. The construction is fabricated by three boards of low- vol. 52, no. 3, pp. 980–992, March. 2004.
[20] R. K. Mongia, I. J. Bahl, P. Bhartia, J. Hong, RF and Microwave
cost Rogers laminates. Coupled-Line Circuits. Norwood, MA, USA: Artech house, 2007.
[21] K.-L. Chan, F. A. Alhargan, S. R. Judah, “A quadrature-hybrid design
REFERENCES using a four-port elliptic patch,” IEEE Trans. Microwave Theory Tech.,
vol. 45, no. 3, pp. 307–310, March 1997.
[1] “5G spectrum recommendations,” 5G Amer., Bellevue, WA, USA,
[22] T. N. Kaifas and J. N. Sahalos, “On the Design of a Single-Layer
White Paper, Apr. 2017. [Online]. Available:
Wideband Butler Matrix for Switched-Beam UMTS System
http://www.5gamericas.org/files/9114/9324/1786/5GA_5G_Spectrum_
Applications,” IEEE Antennas Propagat. Magazine, vol. 48, no. 6, pp.
Recommendations_2017_FINAL.pdf
193–204, Dec. 2006.
[2] W. Hong et al., “Multibeam Antenna Technologies for 5G Wireless
[23] J. R. James and P. S. Hall, Handbook of Microstrip Antennas.
Communications,” IEEE Trans. Antennas Propagat., vol. 65, no. 12,
London, UK: Peter Peregrinus Ltd., 1989.
pp. 6231–6249, Dec. 2017.
[24] J. Lange, “Interdigitated Stripline Quadrature Hybrid,” IEEE Trans.
[3] K. Fujimoto, Mobile Antenna Systems Handbook, Third edition.
Microwave Theory Tech., vol. 17, no. 12, pp. 1150–1151, Dec. 1969.
Norwood, MA, USA: Artech house, 2008.
[25] M. Daneshmand, R. R. Mansour, P. Musavi, S. Choi, B. Yassini, A.
[4] I. Uchendu and J. Kelly, “Survey of Beam Steering Techniques
Zybura, and M. Yu, “Integrated Interconnect Networks for RF Switch
Available for Millimeter Wave Applications,” PIER, vol. 68, pp. 35-64,
Matrix Applications,” IEEE Trans. Microwave Theory Tech., vol. 53,
2016.
no. 1, pp. 12–21, Jan. 2005.
[5] “AWMF-0157 Product data sheet,” Anokiwave, San Diego, CA, USA.
[26] T. N. Kaifas and J. N. Sahalos, “A 4 × 4 Butler matrix optimized for
[6] S.-C. Gao, L.-W. Li, M.-S. Leong, and T.-S. Yeo, “Integrated
UMTS applications,” Microwave and Optical Technology Letters, vol.
multibeam dual-polarised planar array,” in IEE Proc.-Microw.,
49, no. 3, pp. 585-588, March 2007.
Antennas and Propag., vol. 148, no. 3, pp. 174-178, June 2001.
[27] B. Henin, and A. Abbosh, “Wideband planar microstrip crossover with
[7] G. Exposito-Dominguez, J. M. Fernandez-Gonzalez, P. Padilla, and M.
high power handling capability and low distortion,” Microwave and
Sierra-Castaner, “Dual circular polarized steering antenna for satellite
Optical Tech. Lett., vol. 55, no. 2, pp. 439–443, Feb. 2013.
communications in x band,” PIER, vol. 122, pp. 61–76, 2012.
[28] B. M. Schiffman, “A new class of broad-band microwave 90º phase
[8] M. M. Cao, X. Wang, X. N. Huo, X. F. Wang and S. X. Wang, “A
shifters,” IRE Trans. Microw. Theory Tech., vol. 6, no. 2, pp. 232–237,
novel dual band and dual circularly-polarized multi-beam antenna based
Apr. 1958.
on Butler matrix,” in Proc. IEEE-APS APWC, Verona, 2017, pp. 64-66.
[29] G. Boyacioglu, Ş. Demir, “Wideband phase shifter design using Lange
[9] C. Dall’Omo, T. Monediere, B. Jecko, F. Lamour, I. Wolk, and M.
coupler and radial stubs,” in Proc. Mediterranean Microwave
Elkael, “Design and realization of a 4x4 microstrip Butler matrix
Symposium (MMS), Guzelyurt, Cyprus, Aug. 2010, pp. 36-39.
without any crossing in millimeter waves,” Microw. Opt. Technol. Lett.,
[30] S. Sarkooyeh, M. Salimi, “An Innovative Ultra Wideband Microstrip
vol. 38, no. 6, pp. 462–465, Sept. 2003.
Phase Shifter Based on the LANGE Coupler,” Int. J. of Science and
[10] C. H. Tesng, C. J. Chen, and T. H. Chu, “A low-cost 60-GHz switched
Engineering Applications, vol. 4, no. 2, pp. 43–45, Mar.-Apr. 2015.
beam patch antenna array with Butler matrix network,” IEEE Antennas
[31] S. Y. Zheng, W. S. Chan, and K. F. Man, “Broadband phase shifter
Wireless Propag. Lett., no. 7, pp. 432–435, July 2008.
using loaded transmission line,” IEEE Microw. Wireless Compon. Lett.,
[11] W. F. Moulder, W. Khalil, and J. L. Volakis, “60-GHz Two-
vol. 20, no. 9, pp. 498–500, Sep. 2010.
Dimensionally Scanning Array Employing Wideband Planar Switched
[32] M.-D. Wei, P. Gjurovski and R. Negra, “90 º Broadband Asymmetrical
Beam Network,” IEEE Antennas Wireless Propag. Lett., vol. 9, pp.
Open-Short-Stub Phase Shifter with Inductance Compensation,” in
818–821, 2010.
Proc. 46th European Microwave Conference (EuMC), London, UK,
[12] C. Rusch, C. Karcher, S. Beer, and T. Zwick, “Planar Beam Switched
Oct. 2016, pp. 979–982.
Antenna with Butler Matrix for 60 GHz WPAN,” in Proc. 6th
[33] K. Klionovski and A. Shamim, “Physically Connected Stacked Patch
European Conf. on Antennas and Propag. (EUCAP), Prague, Czech
Antenna Design with 100% Bandwidth,” IEEE Antennas Wireless
Republic, 2012, pp. 2794–2797.
Propag. Lett., vol. 16, pp. 3208–3211, 2017.
[13] C. E. Patterson, W. T. Khan, G. E. Ponchak, G. S. May, and J.
Papapolymerou, “A 60-GHz active receiving switched-beam antenna

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