Post on 06-Dec-2014
description
Design and Realization of Passive Phase Shifter for Non Mechanical 1.8 GHz BTS Antenna Tilting
Dr.Ir.Joko Suryana
Andrian Agung, ST
Laboratory of Radio Telecommunications and Microwave
School of Electrical Engineering and Informatics ITB
1
Outline
• Abstract
• Antenna Tilting Concept – What, Why, How
• Research Design
• Design and Simulation– Array Antenna
– Passive Phase Shifter
• Implementation and Measurement
• Conclusions
3
Abstract• In this paper, we propose a low cost tilting control for
BTS antenna system based on passive phase shifter.
• The proposed BTS antenna has operating frequency at
1.8 GHz BTS
– This BTS antenna consists of 4 elements array.
– This antenna is designed with meander microstrip line and 0.4 λ
spacing and implemented on FR-4 substrate with permittivity 4.3.
• The phase shifter is implemented using Alumina which
has permittivity 9.4.
– The Alumina has higher permittivity than the antenna substrate
to cover each branch of transmission line of array antenna for
providing a non mechanical tilting control.
ANTENNA TILTING
What ?
• One of the most important aspects of BTS optimizationtasks is adjusting tilts, or the inclination of the antennain relation to an axis.
• With the tilt, we direct irradiation further down forconcentrating the energy in the new desired direction.
5
What ?• There are 2 tilting types :
– Mechanical tilt: Beam tilted by placement of the antenna with the help of mounting accessories.
– Non Mechanical or Electrical tilt: Beam tilted by varying the phase (using phase shifters)of the antenna elements
Why ?
• When we apply the tilt to an antenna :– we improve the signal in areas
close to the site; and – reduced the coverage in more
remote locations.
• In other words, when we're adjusting the tilt :– we seek a signal as strong as
possible in areas of interest (where the traffic must be), and ;
– similarly, a signal the weakest as possible beyond the borders of the cell.
How ?
• Mechanical tilt :– tilting the antenna by
physically adjusting the specific accessories on its bracket, without changing the phase of the input signal
• Electrical tilt :– Modification of the diagram is
obtained by changing thecharacteristics of signal phaseof each element of theantenna, as seen below.
How ?
Phase Shifter can be implemented in two
ways :
1. Active :
– Expensive
– Using active components
2. Passive :
– Cost efficient
Product ?
RET
RESEARCH DESIGN
Research Questions
• How to provide low cost non-mechanical tilting for BTS antenna ?
1. The passive phase shifter material should be available in Indonesia
2. The dimension of BTS antenna is not allowed bigger than before
3. The tilting angle is minimal 3 degree
13
Research Objectives
1. Designing and implementing BTS antenna model using 4-elements antenna array which has specific transmission lines for providing variable phase shifting function
2. Designing and implementing passive phase shifter based on Alumina substrate
3. Measuring the tilting performance of the implemented BTS antenna and its passive phase shifter
13
DESIGN AND SIMULATION : ARRAY ANTENNA
15
4-Elements Array Antenna : Standard Transmission Lines
• Frequency band : 1.8 GHz• Substrate= FR-4
• Thickness = 1.6 mm
• Patch dimension :
– L = 52,26 mm
– W = 37,75 mm
15
Port 2 SMA Connector
Rectangular Patch Antenna
Transmission Line
16
Simulation Results : Radiation Pattern and S11
16
DESIGN AND SIMULATION : PHASE SHIFTER
Substrate Choice
Substance Dielectric Constant Loss TangentAir 1.00054 0Alumina - 96% 10 0.0002 @ 1 GHzAlumina -99.5% 9.6 0.0002 @ 100 MHz
0.0003 @ 10 GHzFR-4 - low resin 4.9 0.008 @ 100 MHzFR-4 - high resin 4.2 0.008 @ 3 GHzGlass (Corning 7059) 5.75 0.0036 @ 10 GHzSilicon 11.7 - 12.9 0.005 @ 1 GHz
0.015 @ 10 GHzTeflon® (PTFE) 2.0 - 2.1 0.00028 @ 3 GHz
Substrate : Alumina
• Aluminium oxide is an amphotericoxide with the chemical formula Al2O3.
• It is commonly referred to as alumina (α-alumina), aloxide, or corundum in its crystalline form, as well as many other names, reflecting its widespread occurrence in nature and industry.
• Its most significant use is in the production of aluminium metal
• Although it is also used as an abrasive owing to its hardness and as a refractory material owing to its high melting point.
Design and Simulation : Passive Phase Shifter
20
Tran
smis
sio
n L
ine
Alumina AluminaAlumina
Die
lect
ric
len
gth
Port 2 SMA Connector
Port 1 SMA Connector
Dielectric Length Effects
• The longer the dielectric material covering the microstrip line, the greater the resulting phase difference
21
0123456789
10111213141516171819202122
5 10 15 20 25 30 35 40 45 50 55
Ph
ase
Sh
ift
(de
gre
e)
Dielectric Length (mm)
Dielectric Thickness Effects
0123456789
10111213141516171819202122
5 10 15 20 25 30 35 40 45 50 55
Ph
ase
Sh
ift
(de
gre
e)
Dielectric length (mm)
selisih fasa tebal 0,1
selisih fasa tebal 0,7
selisih fasa tebal 0,05
• Thicker dielectric material, the greater the resulting phase
22
Permittivity Effects
0123456789
10111213141516171819202122232425
5 10 15 20 25 30 35 40 45 50 55
Ph
ase
Sh
ift
(de
gre
e)
Dielectric Length (mm)
permitivitas 9,4
permitivitas 20
permitivitas 48
permitivitas 60
• The higher value of the dielectric permittivity of the material used, the greater the resulting phase difference
23
24
Standard Transmission Lines With Passive Phase Shifter
24Port 2 SMA Connector
Rectangular Patch Antenna
AluminaTransmission Line
25
Simulation Results : Radiation Pattern and S11
25
DESIGN AND SIMULATION : MEANDER LINE
Meander Line
• From the simulation results we have seen that the longer thedielectric material covering the microstrip line, the greaterthe resulting phase difference– But it is not practical due to increasing the array antenna dimension
• So we need another approach to increase phase shift whilekeeping the BTS dimension same as before– We used Meander Line for extending the transmission line of each
branch while keeping the dimension
27
28
4-Elements Array Antenna : Meander Transmission Lines
• The length of meander lines = 29,3 mm
• Patch dimension:
– L = 52,26 mm
– W = 37,75 mm
28
Port 2 SMA Connector
Rectangular Patch Antenna
Meander Line
29
Simulation Results : Radiation Pattern and S11
29
30
Meander Transmission Lines With Passive Phase Shifter
3030
Port 2 SMA Connector
Rectangular Patch Antenna
AluminaMeander Line
31
Simulation Results : Radiation Pattern and S11
31
IMPLEMENTATION
32
32
33
Two Model Implementation
• The antenna is implemented using FR-4 as the PCB with
copper ground plane.
• These following figures are the fabricated antennas that
have been combined with their passive phase shifters.
• First antenna model :
– 4-elements array antenna and passive phase shifter
with standard transmission lines
• Second antenna model :
– 4-elements array antenna and passive phase shifter
with meander transmission lines
34
Implemented Array Antenna and Passiver Phase Shifter : Standard
34
35
Implemented Array Antenna and Passiver Phase Shifter : Meander
35
MEASUREMENT SETUP
Antenna Measurements
• Return Loss Measurements
– For measuring the S11 parameters
– Using Vector Network Analyzer
• Radiation Pattern Measurements
– For measuring the radiation pattern with and without alumina-based phase shifter equipped to the array antennas
– Using Signal Generator, Spectrum Analyzer and Antenna Positioner
Return Loss Measurements
Block Diagram of Measurement Setup
VNA 0 – 3.5 GHz
Antenna ( DUT )
Radiation Pattern Measurements
Block Diagram of Measurement Setup
Radiation Pattern Measurements
Spectrum Analyzer
SignalGenerator
AntennaPositioner
MEASUREMENT VS DESIGN SIMULATION RESULTS
Simulation vs Measurement : S11
• Standard Transmission Lines
42-18.00
-16.00
-14.00
-12.00
-10.00
-8.00
-6.00
-4.00
-2.00
0.00
1.70 1.80 1.90 2.00
S11
(d
B)
Frekuensi (GHz)
pengukuran
simulasi
• There is a frequency operating
shift from 1.78 GHz (software
simulation) to 1.9 GHz (prototypemeasurement)
Simulation vs Measurement : S11
• Meander Transmission Lines
• Without passive phase shifter :
– The best S11 is -14.68 dB at the exact frequency is 1.802 GHz for simulation.
– In measurement, at 1.8 GHz, S11 is -10.68 dB.
43
-16.00
-14.00
-12.00
-10.00
-8.00
-6.00
-4.00
-2.00
0.00
1.70 1.80 1.90
S11
(d
B)
Frekuensi (GHz)
pengukuran
simulasi
Simulation vs Measurement : S11• Antenna –Standard Transmission Lines
with Alumina-based Phase Shifter
44
-20.00
-18.00
-16.00
-14.00
-12.00
-10.00
-8.00
-6.00
-4.00
-2.00
0.00
1.70 1.80 1.90 2.00
S11
(d
B)
Frekuensi (GHz)
pengukuran
simulasi
• There is a frequency operating
shift from 1.83 GHz (software
simulation) to 1.86 GHz (prototypemeasurement)
Simulation vs Measurement : S11
• Antenna –Meander Transmission Lines with Alumina-based Phase Shifter
• With passive phase shifter :
– The S11 is above -10 dB at frequency 1.8 GHz for the simulation
– The S11 is -12.45 dB at frequency 1.8 GHz for measurement 45
-20.00
-18.00
-16.00
-14.00
-12.00
-10.00
-8.00
-6.00
-4.00
-2.00
0.00
1.70 1.80 1.90
S11
(dB
)
Frekuensi (GHz)
pengukuran
simulasi
Radiation Patterns• Without Alumina
Standard Transmission Line Meander Line
-40.00
-35.00
-30.00
-25.00
-20.00
-15.00
-10.00
-5.00
0.00
04 8 1216202428
3236
4044
4852
5660
646872768084889296100104
108112
116120
124128
132136
140144
148152156160164168172176
180184188192196200204208
212216
220224
228232
236240
244248
252256260264268272276280284288292296
300304
308312
316320
324328
332336340344348352356
simulasi
pengukuran
46
-35.00
-30.00
-25.00
-20.00
-15.00
-10.00
-5.00
0.00
04 8 1216202428
3236
4044
4852
5660
646872768084889296100
104108
112116
120124
128132
136140
144148
152156160164168172176180
184188192196200204208212
216220
224228
232236
240244
248252
256260264268272276280284288292296
300304
308312
316320
324328
332336340344348352356SimulationMeasurement
Radiation Patterns• With Alumina
Standard Transmission Line Meander Line
-40.00
-35.00
-30.00
-25.00
-20.00
-15.00
-10.00
-5.00
0.00
04 8 1216202428
3236
4044
4852
5660
646872768084889296100104
108112
116120
124128
132136
140144
148152156160164168172176
180184188192196200204208
212216
220224
228232
236240
244248
252256260264268272276280284288292296
300304
308312
316320
324328
332336340344348352356
simulasi
pengukuran
47
-60.00
-50.00
-40.00
-30.00
-20.00
-10.00
0.00
04 8 1216202428
3236
4044
4852
5660
646872768084889296100104
108112
116120
124128
132136
140144
148152156160164168172176
180184188192196200204208
212216
220224
228232
236240
244248
252256260264268272276280284288292296
300304
308312
316320
324328
332336340344348352356SimulationMeasurement
Small Alumina sheet can be used
as low cost passive phase shifter
to give 0o-3.5o tilting control.
CONCLUSIONS
49
Conclusions
1. From our simulation and measurement results we can conclude that : – The tilting function has been demonstrated
successfully by using passive shifter based in alumina
2. From the simulation and measurement results we can also conclude that :
– Small Alumina sheet can be used as low cost passive phase shifter to give 0o-3.5o tilting control.
3. Moreover, these Alumina sheets which cover the transmission lines of the array antenna will also :
– Enhance the return loss of the array antenna.
THANK YOU