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Cavity type resonator method, Shield case material evaluation system for EMC measures

Model No. EMC71

Traditionally, iron, aluminum, and aluminum vapor- deposited plastics are the materials used to build the backside cases of plasma displays.

For these materials, the following measures are taken:

Recently, however, a serious problem has been recognized with this system: the inside of the case functions as a resonator, and therefore unnecessarily amplifies radio waves by as much as 100 or 500 times.

This is often caused by leaks in the holes of the case, the cables, or the screen.

For this reason, a conductive case with radio wave absorbing function --- the case is conductor and its surface has property of radio wave absorption, so that it becomes conductive when connected --- has become more important than ever.

KEYCOM's compact measurement system is of great help to develop materials having this characteristics.

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Measurement Process

Step 1.

Cut the material into a square with 25 mm sides, attach the square to a plastic fixture, and place the square into a resonant cavity (see picture on the left).

Step 2.

The resonance frequency and the Q value of the empty resonator grow lower when the sample specimen is inserted.
The lower the Q value drops, the better the material of the case.
The Q value of the material measured with this system, as well as that of the case fabricated with the material measured, are shown in Table 1, where the trend corresponds well with the EMC effect.

Table 1. Q value by this system of various materials and Q value of case

Material Q value of material Q value of case produced with left material Effect of EMC
Material none 6265
A 6133 2300 None
B 5635 2110 Normal
C 5370 2000 Better
D 5218 1950 Best

One example of the measurement screen when material C is measured is shown as below image.
It is a resonance curve. Q value is indicated in a right part.

Measurement Example


Frequency Around 1GHz
Sample size Size: 25mm x 25mm
Thickness: 0.1mm ~ 2mm
Measuring equipment
1. or 2.

1.Vector network analyzer, Scalar network analyzer

2. Synthesized sweeper with receiver, Windows PC ( GPIB boad with National Instrument driver 〉

Ordering Information(Please inform us Part No. or your requirement for measurement)

Part No.
Product Name
MEMC-COE-01 Resonator Kit
COE-01 Reconator Controller
TMR-1D Resonator Kit for 1GHz
TMR-5D Resonator Kit for 5GHz
DMP-70 Program for evaluating marerials of EMC countermeasure case
CM06D - APC2.9(m) APC2.9(m) - 1000 Coaxial cable assembly at 40GHz : 1m-2 pcs
VNA(Optional) Vector Network Analyzer
Windows PC(Optional) You can purchase Windows PC(Printer included) at the same time