Agilent Technologies 4294A Specifications download pdf (Page 97)

5-9. Cable measurements

The characteristic impedance Z(Ω), capacitance per unit length C (pF/m) and the propagation con-

stants α (dB/m) and β (rad/m) are parameters commonly measured when evaluating cables. Figure

5-32 shows a measurement setup for coaxial cable using an auto balancing bridge type impedance

analyzer and the 16047E test fixture. Note that the High terminal of the test fixture is connected to

the outer conductor of the cable. This measurement setup avoids the effects of noise picked up by

the outer conductor of the cable, and is important to regard when the cable length is long. The char-

acteristic impedance and propagation constants are determined by measuring the impedance of the

cable with its other end opened and shorted (open-short method), and calculating using the equa-

tions shown in Figure 5-32.

The I-BASIC programming function of the impedance analyzer facilitates the calculations required.

Figure 5-33 demonstrates an example of measured characteristic impedance vs frequency.

Figure 5-32. Coaxial cable measurement setup and parameter calculation

5-23

1 2 ... 92 93 94 95 96 97 98 99 100 101 102 ... 125 126

No comments

Agilent Technologies 4294A Specifications Page 97