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How to achieve a homogeneous sensitivity in How to achieve a homogeneous sensitivity in

How to achieve a homogeneous sensitivity in - PowerPoint Presentation

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How to achieve a homogeneous sensitivity in - PPT Presentation

THz detector arrays M Sakhno J GumenjukSichevska F Sizov Institute of Semiconductor Physics NASU Kiev Ukraine email sakhnomgmailcom THz CMOS FPA principle Advantages ID: 813125

antenna substrate thickness thz substrate antenna thz thickness detector system gain antennas elements matching nep fet wave lens frequency

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Slide1

How to achieve a homogeneous sensitivity in THz detector arrays

M.

Sakhno

, J.

Gumenjuk-Sichevska

, F.

Sizov

Institute of Semiconductor Physics NASU,

Kiev, Ukraine,

e-mail: sakhno.m@gmail.com

Slide2

THz CMOS FPA principleAdvantages of Si FET THz Detectors Based on standard silicon technology with high level of integration

Un-cooled

Can be assembled into arrays for real time THz/mm wave imaging;

Mechanically robust;Low costs at high volumes

2

Antenna

FET

Slide3

Detector characterization

Uniform NEP for different

elements of the array

Minimal NEP

Goal

1. Maximal G and

η

a

2. Uniform

G and

η

aNEP – noise equivalent power. Minimal power which can be detected by detector

NEPel electrical NEP of detector itselfG the antenna gainηa matching between the antenna and the detector

3

Slide4

System photograph (silicon FET array implementation)

Printed antennas on finite electrically thick substrate

Modelled system

4

Slide5

System parameters

10

75.8

164

20

104

Modeling using EMSS

FEKO

10

mm

1

mm

1

mm

The modeled system design:

8

antennas on a substrate of finite size. Antennas are positioned symmetrically relative to the substrate center

5

Slide6

Cut-off frequency of the first mode fc1 for infinite substrate

h, µm

ε

r

=2

ε

r

=7

ε

r

=12

501.5THz

0.612 THz0.452 THz140

0.536 THz

0.219 THz

0.162 THz6500.116 THz

0.047 THz0.035 THz

Pozar, D.: Considerations for millimeter

wave printed antennas. IEEE Trans. Antennas Propag. 31, 740–747 (1983)

6

Slide7

Linear gain diagram for

substrate

thickness

h=50

μm

, f=300GHz

Each antenna was simulated and the results were combined on one picture to facilitate the comparison of different elements

7

Slide8

Linear gain diagram for substrate thickness h=140 μm, f=300GHz

8

Slide9

Linear gain diagram for substrate thickness h=650 μm, f=300GHz

9

Slide10

Antenna pattern for different substrate relative

permittivities

Substrate thickness is h=140

μm

10

Slide11

Dependence of the calculated total antenna gain G in the normal direction on the substrate permittivity

1

2

3

4

5

6

7

8

11

Slide12

Calculated gain for normal direction for 1st and 4th elements

1

2

3

4

5

6

7

8

12

Slide13

Antenna – transistor matching

Antenna

FET

R

G

= 150 Ω,

R

S

= 50 Ω,

C

p

= 4

fF

Z

tr

= (200 – j

130)

Ω at f

= 300 GHz

13

1-μm Si MOSFETW/L = 20/2 (μm)

Sakhno

, M.,

Golenkov

, A., &

Sizov

, F. (2013). Uncooled detector challenges:

Millimeter

-wave and terahertz long channel field effect transistor and

Schottky

barrier diode detectors.

Journal of Applied Physics

,

114

(16), 164503. doi:10.1063/1.4826364

Slide14

Antenna-detector matching for different substrate thickness

1

2

3

4

5

6

7

8

Optimal matching is not for electrically thinnest substrate

Matching coefficient variation is less than gain variation

14

Slide15

System with the lens

The angle of maximum gain versus the element position for the system with the lens (only the first four elements are shown because of the mirror symmetry). The substrate parameters are

h

=50

μm

,

r

=2, the incident radiation frequency is 300 GHz

15

Slide16

ConclusionsThe substrate electric thickness in THz FPAs plays a crucial role in the frequency characteristics of the systemElectrically thick substrate makes NEP of elements non-uniformDegradation of antenna pattern can be explained by excitation of substrate modes. Critical substrate thickness is approximately 0.25 wavelength in dielectricSimulation shows that Si CMOS system (substrate thickness

h

= 50μm and

εr = 2) with the lens can operate as FPA16

Slide17

AcknowledgementsThis work is partly supported by the SPS:NUKR.SFP 984544 Project and a joint grant 01-02-2012 from the National Academy of Sciences of Ukraine and Russian Academy of Sciences.17

Slide18

Thank You !18