Fig. 1. Transmitter architecture

A Differential printed antenna design for multiband Impulse Radio transmitter at 60 GHz

Cherif Hamouda2, Rahma Abdaoui1, Martine Villegas1, Benoit Poussot2, Laurent Cirio2, Jean-

Marc Laheurte2

1Université Paris-Est, ESYCOM, ESIEE Paris, Cité Descartes, 2 Bd Blaise Pascal, 93162 Noisy-le-Grand Cedex

²Université Paris-Est, ESYCOM, 5 bd Descartes, Champs-sur-Marne, 77454 Marne-la-vallée cedex 2

Email: hamoudacherifdj@gmail.com

ABSTRACT — We propose in this paper two microtrip planar antennas dedicated to a 60 GHz high data rate Impulse Radio Multi-band On Off Keying (IR-MBOOK) low power consumption transmitter architecture. The planar antennas were designed and simulated on a conventional and low-cost RT/Duroid 5880 substrate, and then are connected after two differential Power Amplifiers. The antennas serve for radiation as well as an out-of-phase power combiner. In this solution, the 57.05-63.7GHz dedicated band is separated into four balanced sub-bands. We propose the use of two differential planar antennas to cover the dedicated bandwidth on the transmitter architecture. An antenna covers the first 57.05-60.257GHz sub-band (band 1 and 2) and a second antenna covers the 60.257-63.7GHz sub-band (band 3 and 4). The planar antennas 1 and 2 were designed and simulated using the electromagnetic HFSS software and they give a maximum gain of 9.81 dBi and 10.03 dBi, respectively.

Index Terms — Differential planar antenna, 60 GHz, UWB, IR MBOOK, impulse radio architectures, differential power amplifier.

I. INTRODUCTION

With the growing demand concerning high data rates wireless applications and additional requirements such as low-cost and low power consumption, new radio architectures have to be developed in the 60 GHz band. These solutions make profit of the advantages of this band, especially with the allocation of about 9 GHz of the [57GHz-66GHz] band to unlicensed use in Europe for example, and over 7 GHz bandwidth in many other countries in the world [1][2]. In our study, we focus on short range indoor applications such as kiosk downloading or very high speed wireless connections for mobile devices. In these applications, directive antennas are not necessary. Therefore, integrated antennas with a sufficient trade-off between gain and Half-power beam width can be appropriate candidates. In this paper, new 60 GHz differential printed antennas designed for impulse radio multiband 60 GHz communications are presented and detailed. Both differential antennas avoid the use of power combiner and thus minimizing the 60 GHz power

combiner’s losses. The designed antennas exhibit very interesting performances in term of gain and bandwidth and they demonstrate the potentiality of the differential approach in the IR MBOOK architecture.

II. MULTIBANDS TRANSEIVER ARCHITECTURES

PRINCIPLES

During the recent years, we have seen a considerable development in communications systems operating in the millimeter frequency bands with a targeted data rate of at least 1 Gbps in a range of few meters. The multi band OOK approach represents in this way an original alternative promising high data rates with low complexity and good integration. In [3], a study was realized to see the influence of sub-bands numbers of an IR-MBOOK architecture in the data rate, the environment of test was IEEE.802.15.3c and the impulsionnel response of channel was generated by a Matlab program realized by H. Harada et al [4]. The results of simulations have shown the interest of multi-bands OOK solution in term of high data rate at 60 GHz.

Fig. 1 shows the transmitter architecture proposed in [3]. A pulse covering the allowed frequency band is generated with a repetition period Tr. The pulse generator is followed by a multiplexer that splits the input signal in

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N sub-bands. Each pulse on each banmodulated at a rate of 1/Tr. Then, the are amplified and combined before anUWB antenna. The receiver architectureeach sub band. After the receive antesplitter, a band-pass filter bank, a squaregate integrator in each band. The splibank are identical in transmitter and rOOK non-coherent architecture solutiosuitable for high data rate communicatio

III. THE DIFFERENTIAL APPR

In the previous architecture [3], the poof the amplifiers is too high. In additioand the losses introduced by the two stagcombiners are important. As a solution for this problem,architecture shown in figure 2 presealternative; it contains only two differconnected directly with two differentialscombiners. Consequently, it promises alow power consumption in a compacvalidate this concept, we design in thdifferentials antennas.

Fig. 2. Transmitter architecture by using diffe

Many works have previously propantennas as a solution to avoid the use[5], a differential antenna which is a bwas designed; it offers good performbandwidth. However, it takes a large ar30 mm by 30 mm, and radiates end-preferable for all applications. In differential patch array antenna for 60 was designed, a gain of 9.4 --- 12.4 dBi broad frequency range of 57 --- 66 GHtakes an area of about 10 mm by 7.4 mm The present work presents two dantennas (DPA) feed by a differential aThe first DPA works at the range 57.05presents a gain of 8.5-9.7dBi and the seat the band frequency 60.275-63.7 GHgain of 9.3-9.8dBi. The area of the twfeeding lines accesses in the same substby 14mm, approximately.

nd are filtered and modulated signals

nd sent toward the e is symmetrical in nna, it includes a e law device and a itter and the filter eceiver. The MB-on is simple and

ons.

ROACH

ower consumption on, they are bulky ges 60 GHz power

the differential ents a promising rentials amplifiers s antennas without

a high data rate and ct dimension. To his work the two

erential antenna.

posed differentials e of combiners. In bunny-ear antenna mance in a wide rea, approximately -fire which is not [6], an on-board GHz applications was achieved in a z and the antenna

m. differentials patch accesses each one. 5-60.275 GHz and econd DPA works

Hz and achieves a wo DPAs and the trate is about 5mm

IV. ANTENNA DESIGN

A. Antenna Design

The differential patch antennis designed on RT-Duroid-58thickness of 254um, at 60 GHzand a loss tangent of 0.001radiating element, two symmetand a pair of parasitic elementsand bandwidth [7]. In our study, we have dedifferential impedance betweeone (to be adapted with differea differential impedance of 20the band 1 (57.05-58.5 GHz) and the second one covers theand 4 (62-63.7 GHz). Geometrical dimensions of thon Table I.

TABLDIMENSIONS OF AN

Wl(um)

W=L(um)

Wp(um)

L(

Ant1

200

1680 650 1

Ant 2

200

1590 650 1

Fig. 3. Differential patch antenna (parasitic elements. Fig. 4 shows the design oincluding two DPA’s on themicrostrip accesses to connecaccesses of the two differential

Fig. 4. DPA 1 and 2 in the same su

N AND SIMULATION

na (DPA) depicted on Fig. 3 880 substrate which has a z; it has a permittivity of 2.2 1. The DPA contains the trically microstrip accesses, s to optimize as well as gain

esigned two DPA’s with en accesses of 200Ω each ential amplifiers which have 00Ω). The first DPA covers

and 2 (58.5-60.275 GHz) e bands 3 (60.275-62 GHz)

he antennas are summarized

LE I NTENNA 1 AND 2 Lp um)

Dp (um)

Sx(um)

Yo(um)

1480 200 150 535

1390 200 150 505

(DPA) with one pair of

of the complete structure e same substrate and four t the DPA’s with the four amplifiers.

ubstrate.

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B. Theory

1) Calculate the reflexion coefficient: When a differential feeding network is developed to generate two symmetrical signals toward a receiver device (a DPA for example), the parameter at the interface between the feeding circuit and the antenna is the odd mode reflection coefficient Γ [8]. This is the apparent reflection coefficient at port 1, when the excitation at port 2 is maintained to be equal in amplitude but perfectly out of phase with that at port 1. In terms of normalized wave variables a and b , representing the incident and reflected waves at port 1, we can thus write:

Γ 1

Fig. 5. Differential antenna modulated as a two ports network. But from the basic definition of S-parameters of the two ports network, we have:

(2) Then, under odd mode condition ( 2 , and from (1) and (2), we get: Γ (3) Thus, the results of simple two ports measurements or simulations can be used to calculate the apparent reflection coefficients that will be seen by each source in an odd mode excitation. This is very convenient in the development of differentially fed antennas, because the bandwidth and loss of the balun or coupler generating the odd mode signal can be eliminated from the initial design steps. The odd mode return loss in dB is defined as 20log Γ . 2) Calculate differential impedance: The patch is modeled as a two ports network. The relation betweentensions and currents at port 1 and 2 is:

V Z i Z i V Z i Z i (4)

Also, the relations of wave variables given in function of voltages and currents at ports 1 and 2 are:

2 , 2

2 , 2 5

Then , the expressions of voltages and currents in terms of the wave variables are: , , 6

If we put 2 and 2 (odd mode condition) in the expression of and given by (6), we get

, then from (4): | (7) Thus, the apparent impedance at the port 1 is equal to Z Z , and as we work with an impair mode in a symmetric ports network, we have an electrical wall at the center of the patch, and the differential impedance between port 1 and 2 will be 2 Z Z .

C. Antenna Simulation

1) Impedance Bandwidth and Gain: Fig. 6 shows the return loss of DPA 1 and 2. It shows that both antennas are correctly matched in the bands of 57-61GHz (bands 1 and 2), and 60.2-64GHz (bands 3 and 4), respectively, with a reflection coefficient lower than -10 dB. The resonance frequency is of 58.7GHz for DPA 1 and 62 GHz for DPA 2.

Fig. 6. Odd mode returns loss for antennas 1 and 2.

57 58 59 60-40

-35

-30

-25

-20

-15

-10

-5

Frequency (GHz)

Odd

mod

e re

flexi

on c

oeffi

cien

t (dB

)

antenna 1

61 62 63 64-40

-35

-30

-25

-20

-15

-10

Frequency (GHz)

Odd

mod

e re

flexi

on c

oeffi

cien

t (dB

)

antenna 2

[S or Z]

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Fig. 7. Realized gain of DPA 1 and 2.

Fig. 7 represents DPA 1 and 2 gain’s, it shows that a gain of 8.5-9.81dBi is realized with DPA1 at the bands 1 and 2 (57.05-60.275 GHz), and a gain of 9.3-10.03dBi is achieved with DPA2 at the bands 3 and 4 (60.275-63.7 GHz).

2) Radiation Pattern

(a)

(b)

Fig. 8. Radiation patterns (in dB) for DPA 1 simulated at 58.5 GHz in E-Plane (a), H-plane (b).

Fig. 8 represents the radiations patterns that are similar

to those obtained with a conventional patch antenna. The 3dB beamwidths is about 74 degrees in E-plane and 69 degrees in H-plane. The front to back ratio are more than 30 dB in the two planes.

V. CONCLUSION

Differential antennas design for multiband IR transmitter at 60 GHz was presented in this paper. These antennas are connected with two differentials amplifiers of a four sub-bands MBOOK differential architecture. Compared with classical architecture, this solution provides high data rate and low power consumption in a compact dimension. The DPA have a differential impedance of 200 Ω between accesses. Simulations results show that the first DPA has a gain of 8.5-9.81dBi in the bands 1 and 2 (57.05-60.275), and the second DPA has a gain of 9.3-10.03dBi in band 3 and 4 (60.275-63.7). They have a 3-dB beamwidth of about 74 and 69 degrees in E and H-plane, respectively. The realized antennas are in progress and the measured values will be presented in the conference presentation.

REFERENCES

[1] Federal Communications Commission, Code of Federal Regulations, “Part 15—radio frequency devices section 15.255: operation within the band 57.0–64.0 GHz”, USA: FCC, Jan. 2001.

[2] Ecc Report 114: Compatibility studies between multiple gigabit wireless systems in frequency range 57-66 GHz and Other services and systems (Except ITS IN 63-64 GHz), Budapest, September 2007, Revised Hyer, May 2009.

[3] R. Abdaoui, M. Villegas, G. Baudoin and M.Suárez, “Performances analysis dedicated to 60 GHz multiband impulse transceiver for Gbits data rate short range communication systems”, (EuWIT) 2010.

[4] Hiroshi Harada, Ryuhei Fanada, Hirokazu Sawada, Shozo Kato, CM MATALAB Release Support Documents, NICT , IEEE.1.-07/0559R3.

[5] R. Wang, Y. Sun, JC. Scheytt, “An on-board differential Bunny-Ear antenna design for 60 GHz applications,” GeMiC, Berlin, March 2010.

[6] R. Wang, Y. Sun, JC. Scheytt, “An on-board differential Bunny-Ear antenna design for 60 GHz applications,” IEEE COMCAS conference, Tel Aviv, Nov. 2011.

[7] J. F. Zürcher, and F. E. Gardiol, Broadband Patch Antennas, Artech House, London: 1995.

[8] E. Lee, KM Chan, P. Gardner, TE Dodgson, “Active Integrated Antenna Design Using a Contact-Less, Proximity Coupled, Differentially Fed Technique,” IEEE Transactions on Antennas and Propagation, Volume 55, Issue 2, Feb.2007.

57 58 59 608.5

9

9.5

10antenna 1

Frequency (GHz)

Gai

n (d

Bi)

61 62 63 649.5

9.6

9.7

9.8

9.9

10

10.1Antenna 2

Frequency (GHz)

Gai

n (d

Bi)

-40

-40

-30

-30

-20

-20

-10

-10

0

0

10 dB

10 dB

90o

60o

30o

0o

-30o

-60o

-90o

-120o

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180o

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120o

EθEφ

-40

-40

-30

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-20

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-10

0

0

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10 dB

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60o

30o

0o

-30o

-60o

-90o

-120o

-150o

180o

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120o

EθEφ

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