ENGINEERING COMMITTEE
Interface Practices Subcommittee AMERICAN NATIONAL STANDARD ANSI/SCTE 78 2012
Test Method for Transfer Impedance
NOTICE
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TABLE OF CONTENTS
1.0 Scope 1
2.0 Equipment 1
小猪画法3.0 Calibration 1
4.0 Specimen Preparation and Installation 1迪卡侬招聘
Figure 1 – Cable Sample and Window 2 5.0 Velocity Measurement 2
Figure 2 – V g Equipment Arrangement and Display 3
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6.0 Optimum Measurement Frequencies 3
7.0 System Frequency Respon 4
8.0 Chamber Inrtion Loss Measurement 4
Figure 3 – Chamber Inrtion Loss Measurement 5 9.0 Forward Measurement 5
Figure 4 – Forward Respon Measurement 5 10.0 Rever Measurement 6
Figure 5 – Rever Respon Measurement 6
11.0 Capacitive Coupling Impedance Calculation 6
12.0 Transfer Impedance Calculation 7
13.0 Terminated Triaxial Test Fixture 8
Figure 6 – Terminated Triaxial Test Fixture 8 14.0 Test Report 9
1.0SCOPE
This procedure is for the measurement of transfer impedance of coaxial drop
cables from 5 MHz to 1,002 MHz.
2.0EQUIPMENT
2.1. Terminated Triaxial Test Fixture (See Figure 6.)
2.2. Signal Source (Swept Frequency Oscillator)
2.3.Detector, Display
(Note: A spectrum analyzer with a tracking generator may be ud or a network物质的量浓度公式
analyzer with a signal source may be ud for the signal source, detector and
display.)
2.4. Loads
2.5. Attenuators
2.6. Optional Power Attenuators (ud in conjunction with the optional RF Amplifier)
2.7.Optional RF Power Amplifier
2.8.Coaxial “T” (For velocity of propagation measurements)
3.0CALIBRATION
The frequency of the signal source and loss of the attenuators shall conform to
appropriate laboratory standards including traceability to recognized measurement
standards.
4.0SPECIMEN PREPARATION & INSTALLATION
4.1. Measure the cable so that it will be long enough to fit through the chamber and
toroids and connect to the fittings at the end of the test fixture.
4.2. Carefully remove two small “windows” of jacket from the specimen. Each
window should be approximately 0.5 to 1 cm (3/16 to 3/8 inch) long and
形象广告approximately 0.5 cm (3/16 inch) wide. The windows should be placed 1.00
meter (39.37 inches) apart and each 0.5 meter (19.69 inches) from the center of
the sample so that the chamber probes, which are spaced 1 meter apart, can make
electrical contact with the outer conductor of the specimen. Care must be taken
not to damage the outer conductor when cutting through the jacket especially if the outer most layer of the outer conductor is a thin aluminum tape. See Figure 1.
39.37"
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Figure 1 - SPECIMEN AND WINDOW
4.3. Install the specimen through the terminated triaxial test fixture. See Figure 6.
Install the appropriate connectors at the ends of the specimen. Inrt the probes into the chamber to make electrical contact with the outer conductor of the specimen. Care should be taken not to damage the shield of the specimen especially if the outer conductor is a thin aluminum tape. An electrical continuity test can be performed to assure that the probes are making contact with the outer conductor of the specimen.
5.0 VELOCITY OF PROPAGATION MEASUREMENT
5.1.
Measure and record the length of the specimen, L s . The length of the specimen is the distance from the center of the coaxial “T” to the open circuit at the end of the specimen. Connect the equipment as shown in Figure 2. Measure the frequency of two adjacent null points. Calculate the velocity of propagation for the specimen, V gs , from:
9108.112x fL V x
gx ∆=
