Iccs 2012 presentation joko suryana and audhia

Design and Realization of 1.8-2.4 GHz MIMO 2 x 2 Antenna

for Handset Applications

Ir.Audhia RezaDr.Ir.Joko Suryana

Laboratory of Radio Telecommunication and Microwave School of Electrical Engineering and InformaticsInstitut Teknologi Bandung INDONESIA

Sunday, November 25, 12

Abstract • A MIMO 2 x 2 antenna for handset application has been proposed.

– The antenna element of the MIMO system is based on a Wideband Planar Inverted F-Antenna (PIFA) which has been optimized at 1.8-2.4 GHz band.

– The PIFA is compact and small enough for the placement in handset which has a limited space

– Wideband characteristics of the PIFA is achieved by applying a meandering shorting strip in place of a normal shorting strip on a regular PIFA.

• Several MIMO configurations are applied for the dual PIFAs to meet the required return losses (S11 and S22), mutual couplings (S12 and S21), and correlation coefficient while maintaining its size to be small enough for the placement in handset.

• The presence of human head and hand has been simulated and analyzed to investigate their effects on performance of the antenna.


Outline

• The Challenges of MIMO 2x2 Antenna Design for LTE Handset

• Designing the MIMO 2x2 Antenna Systems• Performance Comparisons of Simulation and

Measurement Results• Head and Hand Effects of MIMO 2x2 Antenna • Conclusions


REQUIREMENTS OF MIMO 2X2 ANTENNA FOR LTE


MIMO Systems• Currently, MIMO systems

are considered as one of main technology applied in 4G system to meet the IMT-Advanced standard.

• MIMO systems provide better diversity gain for increasing the SNR and improving system performance on

Datarate vs SNR for various MIMOs


MIMO 2x2 Antenna Design Challenges

• LTE technology facilitates MIMO to support high data rate applications. However, integrating several antennas onto a printed circuit board (PCB) becomes progressively more difficult as each new generation of handsets experience miniaturization.

• The closely-spaced antennas produce high mutual coupling, which opposes the relatively low correlation between the received signals as required for effective MIMO performance.

• High port-to-port isolation is required to achieve the low correlation between closely spaced antennas.


Typical Handset Size

• Current mobile devices have limited space.

• A typical smartphone is about 60 mm wide x 130 mm long.


MIMO 2x2 Antenna Design • The typical antenna specification for 2x2 MIMO has

the following goals: 1.Number of independent antenna ports: 22.Radiation efficiency: as high as possible ~ 100 %3.Gain balance ratio : as high as possible ~ 1 • ratio of the gain at each antenna port

4.Correlation coefficient : As low as possible ~ 0• envelope correlation coefficient between the two antenna ports

Parameter/Impact Space Coupling Correlation Diversity GainSpace↓ - ↑ ↑ ↓

Coupling ↓ ↑ - ↑ ↓Correlation↓ ↑ ↑ - ↑


MIMO 2X2 ANTENNA DESIGN


Element Antenna : Reference • Reference : P. W. Chan, H. Wong, and E. K. N. Yung, "Wideband planar inverted-F

antenna with meandering shorting strip," Electronics Letters , vol. 44, no. 6, pp. 395-396, 2008.

• fc is the fundamental resonant

frequency of PIFA• C is the speed of light• L1 and L2 represent length and

width of the planar element of PIFA• εr represents dielectric permitivitty

of substrate (in this case air, εr = 1) • W represents the shorting strip

width. • For 1.8-2.4 GHz, the upper

frequency is set to be 2.2 GHz • The second resonant frequency

made by the meandering shorting strip should be < 2.2 GHz


Element Antenna : Optimization

Our optimization approach:• Adjust the ground plane

dimension • Modify the feeding distance from

the shorting • Control the height of the planar

element from ground plane


Element Antenna : Designed PIFA

• fc is the fundamental resonant frequency of PIFA

• C is the speed of light• L1 and L2 represent

length and width of the planar element of PIFA

• εr represents dielectric permitivitty of substrate (in this case air, εr = 1)

• W represents the shorting strip width.

• For 1.8-2.4 GHz, the upper frequency is set to be 2.2 GHz

• The second resonant frequency made by the meandering shorting strip should be < 2.2 GHz


MIMO 2x2 Antenna : Possible Configurations

• Before applying the MIMO configuration, the designed element antenna is placed at the top of a PCB that would act as a handset component board. Then, the MIMO configuration is applied by placing the second identical element antenna at the same PCB.

• The placement and positioning of the two antennas is varied but the placement should not use more than allowed space of 65 x 100 mm2 PCB. The minimum spacing required between two antenna in MIMO system is typically 0,5 λ .

• The best MIMO configuration is when 1st antenna placed vertically at the top left corner and 2nd antenna placed horizontally at the bottom right corner Far VH . In this configuration, the distance between the two antennas is 97.72 mm or equal as 0.715 λ.


MIMO 2x2 Antenna : Possible Configurations

VV HH + 45

Far VV Far VH


SIMULATION AND MEASUREMENT RESULTS


Simulation and Measurement Results

• The designed MIMO antenna is then implemented using FR4 Epoxy.

• The designed and fabricated antenna are shown at these figure :


Simulation and Measurement Results : Return Loss

• We can see that S11 measurement curve is deeper and also wider than simulation design at 1.72-2.41 GHz.

• The measurement result for S22 is also better and operates at 1.74-2.49 GHz.

• It can be concluded that the specification required for return loss is met by the antenna.


Simulation and Measurement Results : Mutual Coupling

• The figure shows us that the mutual coupling between measurement and simulation results is slightly different at 2.3 GHz.

• However, the overall both gives the result that S12 dan S21 < -15 dB for the 1.8-2.4 GHz.


Simulation and Measurement Results : Correlation Coefficients

• The measured correlation coefficient is lower than simulated correlation coefficient.

• However, these results are still appropriate to the required coefficient correlation, i.e. which must < 0.1 for MIMO antenna.

• The differences between measured and simulated results is come from the differences of S parameters between simulation and measurement.


Simulation and Measurement Results : Radiation Patterns # 1st Antenna


Simulation and Measurement Results : Radiation Patterns # 2nd Antenna


HEAD AND HAND EFFECTS


Simulation and Measurement Results : Head and Hand Effects• Effects of the usage of the antenna near human

head and hand to the antenna parameters are also investigated for analyzing its effect on performance of the MIMO antenna.


Simulation and Measurement Results : Head and Hand Effects

• The measured return loss for the MIMO antenna is slightly different than the simulated data.

• S11 for measurement is < -10 dB for 1.72-2.34 GHz, meanwhile simulation gives S11 < -10 dB for 1.74-2.34 GHz.

• S22 for measurement is < -10 dB for 1.75-2.37 GHz, meanwhile simulation gives S22 < -10 dB for 1.89-2.35 GHz.

• We missed the 2.4 GHz subband, but actually we do not use Wifi Access while putting handset on that position


Simulation and Measurement Results : Head and Hand Effects

• The measured mutual coupling for the MIMO antenna is also slightly different than the simulated data.

• Mutual coupling for measurement and simulation is < -15 dB for all frequency, included the frequencies outside the 1.8-2.4 GHz band.


CONCLUSIONS


Conclusions • The return loss of PIFA with meandering shorting

strip can be improved by ground plane width adjustment, planar height adjustment, and feed-shorting distance adjustment.

• The implemented antenna dimension is compact and small, i.e 20.5 x 16 mm2 with the shorting width of 2 mm and planar height 9.5 mm from the ground plane. – The MIMO antenna can be fabricated on PCB

which has 65 x 100 mm2 dimension.• The antenna works well at desired band, i.e 1.8-2.4

GHz for S11 < -10 dB thus can be used for various modern wireless communications such as DCS-1800, UMTS, LTE 2,3 GHz, and WLAN-bluetooth.


Conclusions• The antennas separation by 0.715 λ is enough for

small mutual coupling and correlation coefficient– The mutual coupling is < -15 dB and correlation

coefficient < 0.1 for the operating band• Finally, the presence of human head and hand has

been simulated and analyzed to investigate their effects on performance of the antenna. – In this case, the return loss is worse at frequency

> 2.35, but this should not be primary concern as we do not use the WLAN applications on this position ( putting handset by hand near the human head )


Thank You


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