Measurements using a GTEM cell above 1GHz Dr Tian Hong LOH

Overview of the Presentation Introduction to GTEM cell Reason for GTEM measurement above 1GHz Equipment under test (EUT) Experimental Setup Experimental Results

Overview of the Presentation Introduction to GTEM cell Reason for GTEM measurement above 1GHz Equipment under test (EUT) Experimental Setup Experimental Results

Introduction: What’s GTEM? GTEM cell – Giga-Hertz Transverse Electromagnetic cell. Tapered Coaxial Transmission Line with 50  termination at both ends.

Introduction: What’s GTEM? Designed for use as EMC radiated emission and radiated immunity test facility without impact of the ambient electromagnetic environment.

Introduction: What’s GTEM? At the input, a normal 50  coaxial line is physically transformed to a rectangular cross section. The cross sectional dimensions are a ratio of 3:2 horizontal to vertical cross sectional dimensions. a b b/a = 3/2

Introduction: What’s GTEM? The centre conductor – septum, is a flat and wide conductor that will produce a uniform electrical field distribution underneath it which form a test volume for testing the EUT.

Overview of the Presentation Introduction to GTEM cell Reason for GTEM measurement above 1GHz Equipment under test (EUT) Experimental Setup Experimental Results

Reason for GTEM measurement above 1GHz The use of GTEM cell above 1GHz is still novel to product manufacturers. Increasing clock speed of computer processors. The need to measure the wave structure and to understand potential limitations in the use of the cell at higher frequencies.

Overview of the Presentation Introduction to GTEM cell Reason for GTEM measurement above 1GHz Equipment under test (EUT) Experimental Setup Experimental Results

Equipment under test (EUT) Dummy device that is commissioned resembling typical products. Consists of monocone antenna as radiating source mounted on the inside of a metal box.

Equipment under test (EUT) Power by a battery operated York EMC Services CGE01 comb generator with 100MHz harmonic spacing. Fundamental signal of 100MHz. Measurable E-field from EUT up to 15GHz.

Equipment under test (EUT) Small EUT (SEUT): [ (L:W:H) = 23cm  20cm  11cm ] Side 5 Side 2 Side 1 Side 5 Side 3 Side 2

Equipment under test (EUT) Large EUT with complicated slots (LEUTC): [ (L:W:H) = 12.5cm  48.5cm  48.5cm ] Side 1 Side 2 Side 3

Overview of the Presentation Introduction to GTEM cell Reason for GTEM measurement above 1GHz Equipment under test (EUT) Experimental Setup Experimental Results

Experimental Setup Instrumentation used: 1.Spectrum Analyser (PSA) 2.Microwave Amplifier 3.Cables 4.Computer System 5.GTEM cell 6.Foam Table 7.EUT

Experimental Setup Vertical Polarisation 7 5 Instrumentation used: 1.Spectrum Analyser (PSA) 2.Microwave Amplifier 3.Cables 4.Computer System 5.GTEM cell 6.Foam Table 7.EUT 6

Experimental Setup SEUT: 1750mm 1620mm 450mm 535mm 590mm 645mm 1

Experimental Setup SEUT: 1750mm 1620mm 450mm 535mm 590mm 645mm 1120mm 3mm 483mm 538mm 1 2

Experimental Setup SEUT: 1750mm 1620mm 450mm 535mm 590mm 645mm 1120mm 3mm 483mm 538mm 820mm 255mm 60mm 370mm 425mm 1 2 3

Experimental Setup LEUTC: 1750mm 1620mm 450mm 85mm 485mm 535mm 777.5mm 125mm

Overview of the Presentation Introduction to GTEM cell Reason for GTEM measurement above 1GHz Equipment under test (EUT) Experimental Setup Experimental Results

SEUT: Sensitivity --- Transverse displacement

Experimental Results SEUT: Sensitivity --- Vertical displacement

Experimental Results SEUT: E-field comparison between GTEM & FAR

Experimental Results LEUTC: E-field comparison between GTEM & FAR

Modified Experimental Setup LEUTC: 1750mm 1620mm 450mm 85mm 485mm 535mm 777.5mm 125mm Stepper Motor

Experimental results LEUTC: E-field comparison between GTEM & FAR

Experimental results: Radiation Pattern Radiation pattern of LEUTC in GTEM:

Thank you for your attention. Any Questions?