Camera anecoica TEM (Transverse Electromagnetic Mode) sviluppada da Tekbox. Adatta a frequenze fino ai 2GHz e oltre.
E' inclusa una terminazione a 50 Ohm (25W) ed un modulo di cancellazioni componenti DC per proteggere l'ingresso dell'analizzatore di spettro.
Specifiche tecniche:
TEM cell dimensions
Length: 1038 mm
Width: 501 mm
Height: 305 mm
Septum height: 150 mm
Rectangular area under the septum: 36 cm x 48 cm x 15 cm
TEM cell connectors: N-female
Nominal cell impedance: 50 Ohm
Wave impedance: 377 Ohm
Maximum RF input power: 25W (limited by supplied 50 Termination)
Input return loss: S11 up to 700 MHz < -16dB
Transmission loss: up to 730 MHz < 3 dB
DC-Block 50V-6GHz-N
Connectors: N-Male/Female
Nominal impedance: 50 Ohm
Max. continuous RF power: 2W
Max. continuous RF voltage: 50V RMS
Frequency: 500kHz to 6 GHz
VSWR: ≤ 1.2
RF-Termination 50Ω-3GHz-25W-N
Connector: N-Male
Nominal impedance: 50 Ohm
Max. continuous RF power: 25W
Frequency: DC to 3 GHz
VSWR: ≤ 1.2
Third order intermodulation: ≤ 120 dBc
What is the usable volume of Tekbox TEM Cells?
The TBTC1 TEM cell has a septum height of 5cm and a septum width of 13cm. The flat section of the bottom plane has an area of 20cm x 20 cm.
The TBTC1 was designed to be a small device, that easily fits on a lab desk and which typically would be used to investigate spurious signals emitted by small to medium size PCB assemblies.
If the purpose is rather checking frequencies than levels of spurious signals, basically any DUT that would physically fit can be inserted into the TEM cell. For safety reason, an insulation distance of 0.5 cm to 1cm to the bottom and 1cm to the septum is recommended. Thus the usable height of a DUT would be limited to 3-4 cm. A consequence of a large DUT would be a degradation of the impedance matching of the TEM cell. Tests with large DUTs in the TBTC1 have shown the S11 to vary between the value at empty state and -10dB. Consequently, a physically large DUT adds to the uncertainty when it comes to estimate equivalent spurious levels that would be measured using antennas in an anechoic chamber set up.
The TBTC2 TEM cell has a septum height of 5cm and a septum width of 23cm. The flat section of the bottom plane has an area of 30cm x 30 cm. The TBTC2 was dimensioned according to specifications given in Annex E of the CISPR 25 specification. With respect to the maximum DUT size, similar considerations as mentioned above can be applied. However CISPR 25 specifies an allowed working region which is 18cm x 18cm and located as per the screenshot below. Of course, similar considerations can be applied to the TBTC1.
Documenti:
TBTC manual
Q&A Open TEM Cells
EMC pre compliance testing guide
Application Note: Radiated Noise Measurement example using Tekbox TEM Cells
TBTC 3 insertion loss (S21)
