Practical Aspects of Microwave Filter Design and Realization IMS’05 Workshop-WMB

Microstrip Filter Design Jia-Sheng Hong Heriot-Watt University Edinburgh, UK [email protected]

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Outline



  

Introduction Design considerations Design examples Summary

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Introduction- Driving forces Recent development of microstrip filters has been driven by applications -

‰ Wireless communications ‰ ‰

Wireless sensor/radar systems …….

Driven by technologies -

‰ High temperature superconducting ‰ Micromachining ‰ LTCC ‰ Ferroelectric ‰ ……. Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Introduction- Microstrip Filter Publications Total 600+ in recent 10 years 120

Search from IEEE Xplore

100

N u m b e r

80 60 40 20 0 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

Year Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Considerations- Topologies l1 W1 s1 W1

Y0

WC WL l2

l1

l4

l3

l7

Wn sn Wn

L4

L2 L1

C6

L5

L3

l n+1

W2 s2 W2

C4

C2

Z0

l6

l5

ln

l2

Z0

W1

W2

W3

Wn+1 sn+1 Wn+1

Y0

Wn

CL1 CL2 l g0/4

l1

l2

l3

CLn-1 CLn

ln 0

l1h

CL3

l g0/4

l2h

l3h

l4h

Yt

l5h

Yn

Y1

1

2

3

q0

n-1

n

n+1

Yt

qt l1v s1

l3v s3

s2

l5v s5

s4 l2v

YA

YA

W

s1,2

s2,3

sn-1,n

l4v

~λ/4

~λ/4

~λ/4

~λ/4

Via hole grounding

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Considerations- Topologies The choice of a topology depends on

9 Characteristics of filters, such as chebyshev or elliptic 9 Bandwidth 9 Size 9 Power handling

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Considerations- Substrates The choice of a substrate depends on

9 Size 9 Higher-order modes 9 Surface wave effects 9 Implementations – couplings, line/spacing tolerances, … 9 Dielectric loss 9 Temperature stability 9 Power handling – dielectric strength (breakdown), thermal conductivity Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Considerations- Higher-order modes 9 Keep operating frequencies below the cutoff frequency of c the 1st higher-order mode, f c = ε r (2W + 0.8h )

90

90

εr = 3

80

εr = 6.15

70

εr = 10.8

60 50 40 30

Cutoff frequency fc (GHz)

Cutoff frequency fc (GHz)

W = 1.0 mm

εr = 10.8

80

W=0.5 mm W=1.0 mm W=1.5 mm

70 60 50 40 30 20

20

10 0.2

0.4

0.6

0.8

1.0

1.2

Substrate thickness h (mm)

1.4

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Substrate thickness h (mm)

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Considerations- Surface waves 9 Keep operating frequencies below the threat frequency of the lowest surface wave mode,

at which the surface mode couples strongly to the dominant mode of microstrip because the phase velocities of the two modes are close.

700

Threat frequency fs (GHz)

c tan −1 ε r fs = 2πh ε r − 1

600

εr = 3 εr = 6.15

500

εr = 10.8

400 300 200 100 0 0.2

0.4

0.6

0.8

1.0

1.2

1.4

Substrate thickness h (mm)

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Considerations- Losses There are three major losses in a microstrip resonator:

‰ Conductor loss

⎛ h ⎞ ⎛⎜ 377Ω ⎞⎟ Qc ∝ π ⎜ ⎟ ⋅ ⎜ ⎝ λ ⎠ ⎝ Rs ⎟⎠

‰ Dielectric loss

Qd ∝

1 tan δ

‰ Radiation loss 1 1 1 1 = + + Qu Qc Qd Qr Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Considerations- Power handling ‰Peak power handling capability – when the breakdown occurs in substrate

Vo2 Pp ∝ 2Z c Vo is the maximum breakdown voltage of the substrate Zc is the characteristic impedance of the microstrip

Narrower band filters result in higher electric field density, leading to a lower peak power handling

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Considerations- Temperature effect Temperature characteristic of a microstrip half-wavelength resonator on RT/Duroid substrate with εr = 10.2, h = 1.27 mm Copper CTE (coefficient of thermal expansion) = 17 ppm/oC Substrate CTE = 24 ppm/oC Substrate TCK (thermal coefficient of εr) = −425 ppm/oC At 23 oC

f0 = 1929.8 MHz

∆f = 0

At 73 oC for copper CTE only

f0 = 1928.1 MHz

∆f = −1.7 MHz

At 73 oC for substrate thickness CTE only

f0 = 1929.9 MHz

∆f = 0.1 MHz

At 73 oC for substrate TCK only

f0 = 1949.4 MHz

∆f = 19.6 MHz

At 73 oC (consider all)

f0 = 1947.8 MHz

∆f = 18.0 MHz

9 Frequency variation versus temperature is mainly due to dielectric constant change vs temperature Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Open-loop filters

1

4

2

3

1

2

5

3

4

6

( b)

(a) 1 1

2

3

6

4

5

7

8

8 2

( c)

3

6

4

5

7

( d)

From: Jia-Sheng Hong and M.J.Lancaster, Microstrip Filters for RF/Microwave Applications, John Wiley & Sons. Inc. New York, 2001

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Open-loop filters ¾Specifications: Center frequency

985MHz

Fractional Bandwidth

10.359%

40dB-Rejection Bandwidth

125.5MHz

Passband Return loss

−20dB

¾Design parameters for an 8-pole filter: M 1, 2 = M 7 ,8 = 0.08441

M 2,3 = M 6, 7 = 0.06063

M 3, 4 = M 5, 6 = 0.05375

M 4,5 = 0.0723

M 3, 6 = −0.01752

Qei = Qeo = 9.92027

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Open-loop filters On RT/Duroid substrate with a relative dielectric constant of 10.8 and a thickness of 1.27mm. Each resonator has a size of 16 by 16 mm.

Realisation 1

0

0

-20

-10 Insertion Loss (dB)

Insertion/Return Loss (dB)

-5

-15 -20 -25

-40

-60

-30 Insertion loss Return loss

-35

-80

-40 925

950

975

1000 1025 1050

Frequency (MHz)

600

800

1000

1200

1400

Frequency (MHz)

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Open-loop filters Realisation 2

On RT/Duroid substrate with a relative dielectric constant of 10.8 and a thickness of 1.27mm

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Trisection open-loop filters Midband or centre frequency

: 905MHz

Bandwidth of pass band

: 40MHz

Return loss in the pass band

: < −20dB

f 01 = f 03 = 899.471 MHz f 02 = 914.713 MHz Qei = Qeo = 15.7203 M 12 = M 23 = 0.04753

Rejection : > 20dB for frequencies ≥ 950MHz

M 13 = −0.02907 0

Magnitude (dB)

-10 -20 -30 -40

S21 S11

-50 700 750 800 850 900 950 1000 1050 1100 Frequency (MHz)

On RT/Duroid substrate with a relative dielectric constant of 10.8 and a thickness of 1.27mm

Measured response

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Trisection open-loop filters Midband or centre frequency

: 910MHz

f 01 = f 03 = 916.159 MHz

Bandwidth of pass band

: 40MHz

f 02 = 905.734 MHz

Return loss in the pass band

: < −20dB

Qei = Qeo = 14.6698 M 12 = M 23 = 0.05641

Rejection : > 35dB for frequencies ≤ 843MHz

M 13 = 0.01915 0

Magnitude (dB)

-10 -20 -30 S21

-40

S11

-50 -60 700 750 800 850 900 950 1000 1050 1100

On RT/Duroid substrate with a relative dielectric constant of 10.8 and a thickness of 1.27mm

Frequency (MHz)

Measured response

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Trisection open-loop filters

Insertion Loss (dB)

0

Insertion Loss (dB)

0

case 1 case 2 case 3 case 4

-20

-40

-60

-20

-80

-40

200

400

600

800

1000

1200

Frequency (MHz)

-60

Measured wideband response -80 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5

Experimental results on extra transmission zeros, where case 1 to 4 indicate the increase of direct coupling between the two feed lines.

Frequency (GHz)

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Multi-layer filters

Dielectric Substrate

Electric Coupling Aperture

Magnetic Coupling Aperture

Common Ground Plane

I/O Ports

Microstrip Open-Loop Resonator

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Multi-layer filters Transmission/Return Loss (dB)

0 Qu=200

-10 -20 -30 -40

Chebyshev Elliptic

-50

Linear Phase

-60 850

900

950

1000

1050

1100

Frequency (MHz)

(a) 35 Group Delay (ns)

30

Qu=200

25 20 15

Chebyshev

10

Elliptic Linear Phase

5 0 940

950

960

970

980

990

Frequency (MHz)

(b)

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Multi-layer filters 0

0

-10

-10

-10

-20 -30 -40

Transmission (dB)

0

Transmission (dB)

-20 -30 -40

-30 -40

-50

-50

-60 850

-60 850

-60

900

950

1000

1050

1100

900

Group delay (ns)

40 30 20 10 0 940

950

960

970

980

Frequency (MHz)

(a)

950

1000

1050

990

1000

40 30 20 10 0 940

950

960

970

980

850

1100

Frequency (MHz)

Frequency (MHz) Group delay (ns)

-20

-50

Group delay (ns)

Transmission (dB)

Experimental results

990

900

950

1000

1050

1100

Frequency (MHz)

40 30 20 10

1000

Frequency (MHz)

(b)

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

0 940

950

960

970

980

990

1000

Frequency (MHz)

(c)

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Design Examples- Slow-wave filters Capacitively loaded line resonator

d

I2

wa

Za, ba V1

CL/2

CL/2

V2

w2 w1

3.25

6

f1

3.00

f1 / f0

5

2.50

3

2.25

2

2.00

1

1.75

0

1.50 1

2

3

4

Loading capacitance (pf)

5

6

3.25

f0 f1

6

2.75

4

0

7

Frequency (GHz)

f0

f1 / f0

Frequency (GHz)

L2 7

Wa=1 mm, w1=2 mm, w2=3 mm, d=16 mm on RT/Duroid 6010

L1

3.00

f1 / f0

5

2.75

4

2.50

3

2.25

2

2.00

1

1.75

0

f1 / f0

d

I1

Microstrip slow wave resonator (I)

1.50 0

1

2

3

4

5

6

7

8

9

10 11

Open-stub length, L (mm)

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Slow-wave filters Centre Frequency : 1335 MHz 3dB Bandwidth :

30 MHz

passband Loss :

3dB Max.

Min. stopband rejection : D.C. to 1253 MHz 60dB 1457 to 2650 MHz 60dB 2650 to 3100 MHz 30dB 60dB Bandwidth : 200 MHz Max.

On RT/Duroid 6010 substrate

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Slow-wave filters 0

Transmission (dB)

37.75mm

-20

0.5mm

-40

-60

Substrate: εr=10.8 h=1.27mm

-80 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Frequency (GHz)

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Dual-mode filters Type I dual-mode resonator D ≈ 1.84λg 0 π

D ≈ λg 0 2

C1 (a)

L1

L2

C2

(b)

D ≈ λg 0 π

D ≈ λg 0 4

( c)

(d)

D < λg 0 4

Mode 1

Mode 2

(e)

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Dual-mode filters 0 16 mm

dxd Port 1

Amplitude (dB)

-10 -20 S21

-30

S11 -40 -50 1.3

1.4

1.5

1.6

1.7

1.8

Port 2

Frequency (GHz)

d =2 mm on RT/Duroid 6010 substrate

2.5% bandwidth at 1.58 GHz

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

1.9

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Design Examples- Dual-mode filters 20 mm

1 mm Port 1

Port 2

On RT/Duroid 6010 substrate

Centred at 820 MHz

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Dual-mode filters Electric Field Pattern

Type II dual-mode resonator

@ Mode 1

Y ⎛ a a⎞ ⎜⎜ , ⎟⎟ ⎝2 3 2⎠

1

2

0 0.5

0.5 0

1 .5

2 1.5 1

0.5 0

0.5

1

0

1

0.5

0

0.5

3.5

2.5

1.5

4

3

2

1

1

1.5

0.5

0.5 2

0.5 0 0.5 1 1.5 2 2.5 3 3.5

a E

0

0.5

2.5 2

1.5

1

0.5 0

1.5

2.5

X

1

1

0

2

Z

0.5

0.5

1

2.5

⎞ ⎛ a , 0⎟ ⎜− 3 ⎠ ⎝

@ Mode 2

1 2.5

3

4

Ed

a⎞ ⎛ a ,− ⎟ ⎜ ⎝2 3 2⎠

Equilateral triangular microstrip patch resonator

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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Design Examples- Dual-mode filters 1

L1

J0,1

w

0

b

3

J0,3

INPUT

OUTPUT

2

a J0,2

L2

J2,3 C2

Circuit model (No coupling between the two modes)

0

Magnitude (dB)

J1,3 C1

-10

|S11| (Theory)

-20

|S21| (Theory) -30

|S11| (EM)

Frequency response

|S21| (EM)

-40

-50 3.0

3.5

4.0

Frequency (GHz)

4.5

5.0

(a = 15 mm and b = 11.25 mm on a 1.27mm thick dielectric substrate with a relative dielectric constant of 10.8)

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

30

Design Examples- Dual-mode filters 10

w

b

a

Magnitude (dB)

0 -10 -20 -30

|S11| (Theory)

-40

|S21| (Theory)

-50

|S11| (Simulation)

-60

|S21| (Simulation)

-70 2.8

a = 15 mm and b = 14 mm on a 1.27mm thick dielectric substrate with a relative dielectric constant of 10.8

3.2

3.6

4.0

4.4

4.8

Frequency (GHz)

Frequency response

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

31

Design Examples- Dual-mode filters Four-pole dual-mode filters

On a substrate with a relative constant of 10.8 and a thickness of 1.27 mm

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

32

Design Examples- Dual-mode reject filters s

l W g a

Magnitude (dB)

0 S11

-10

S21

-20 -30 -40 3.6

Single dual-mode resonator

3.8

4.0

4.2

4.4

Frequency (GHz)

1

PORT 2

PORT 1 2

The details to be presented in another session (WE4C) at IMS2005

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

33

Design Examples- Extract-pole filters

Ls

zin

Cs

=

J=1

L=Cs

C=Ls

l1 ≈λg/4

zin

l2 s

zin Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

l3 ≈λg/2

34

Design Examples- Extract-pole filters

On RT/Duroid 6010 substrate

EM simulated performance

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

35

Design Examples- Extract-pole filters

On RT/Duroid 6010 substrate Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

36

Design Examples- CQ filters

PORT 1

PORT 2

dB

8 pole 5MHz wideband S21 res ponse 65K S21

0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 Start: 1.880000 GHz

Stop: 2.200000 GHz

Another 18-pole filter of this type with group delay equalisation will be presented in TH1F session at IMS2005 Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

37

Design Examples- CQT filters

PORT 1

PORT 2

10

dB 0

S11

1

S21

dB 0

-10

-5

-20

-10

-30

-15

-40

-20

-50

-25

-60

-30

-70

-35 1

-80

S21 1.974000 GHz -0.7590 dB

-90

-40 -45

-100

-50 Start: 1.960000 GHz

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

Stop: 1.985000 GHz

38

Design Examples- Wideband filters Optimum stub bandpass or pseudo highpass 2θc

2θc

0.9

2.8

2.0 23.8

y0=1

yn-1,n

y1,2 yn-1

y2

y1

y0=1

4.9

13.9

22.7

23.0

13.5

yn

Short-circuited stub of electrical length θc

150

π/2

π−θc π

On substrate: εr = 2.2, h = 1.57 mm 3π/2

0

θ

|S21|

Amplitude (dB)

θc

30

13.2

Via hole grounding

θc

Unit: mm

-10 -20 -30 -40

S21

-50

S11

-60 0

fc

(π/θc −1)fc

1

2

3

4

5

6

7

Frequency (GHz)

f

EM simulated performance

From: Jia-Sheng Hong and M.J.Lancaster, Microstrip Filters for RF/Microwave Applications, John Wiley & Sons. Inc. New York, 2001

Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

39

Summary 9 Microstrip filter designs involve a number of considerations, including careful choice of topologies and substrates. 9 Some design examples of new topologies with advanced filtering characteristics have been described, including – ƒ ƒ ƒ ƒ ƒ ƒ

Open-loop resonator filters Multilayer filters Slow-wave filters Dual-mode filters Extract pole, Trisection, CQ and CQT filters Optimum wideband stub filters

9 Driven by applications and emerging device technologies, many new and advanced microstrip filters have been developed and their designs are available in open literatures. Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]

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