Download TR41.9-16-02-008-Transverse Balance test procedures for FAST

Telecommunications Industry Association
TR41.9-16-02-XXX
Document Cover Sheet
Project Number
TIA-PN-31-D-4
Document Title
Transverse Balance test procedures for FAST DSL
Source
Cisco Systems
Contact
Tim Lawler
170 West Tasman Dr.
San Jose, CA 95134
Distribution
TR-41.9
Intended Purpose
of Document
(Select one)
X
Phone: (408) 527-0681
Fax: (408) 853-3288
Email: [email protected]
For Incorporation Into TIA Publication
For Information
Other (describe) -
The document to which this cover statement is attached is submitted to a Formulating Group or sub-element
thereof of the Telecommunications Industry Association (TIA) in accordance with the provisions of
Sections 3.3.2.2 through 3.3.2.4 inclusive of the TIA Engineering Committee Operating Procedures dated
May 2014, all of which provisions are hereby incorporated by reference.
Abstract
This contribution is a proposal for adding Transverse Balance test procedures for FAST DSL to TSB-31-D-4.
V2.1 – 20141205
Telecommunications Industry Association
10.5
TR41.9-16-02-XXX
Transverse Balance, FAST TIA-968-B-3, 5.3.10.2
10.5.1 Background
See subclause 10.1.1.
10.5.2 Purpose
To determine transverse balance of FAST EUT.
10.5.3 Equipment
(1)
Spectrum analyzer SEL#34
(2)
Tracking generator SEL#39
(3)
Transverse balance test fixture shown in Figure 10.5-1
Note: Refer to subclause 5.5 for equipment details.
10.5.4 Equipment States Subject To Test
Active state with appropriate grounding applied and the EUT transmitter turned off.
Note: Terminal equipment may require special attention to ensure it is properly configured for this test. For
example, if the equipment would normally be connected to AC-power ground, cold-water-pipe ground,
or if it has a metallic or partially metallic exposed surface, then these points are connected to the test
ground plane. Similarly, if the EUT provides connections to other equipment through which ground
may be introduced to the equipment, then these points are connected to the test ground plane.
Equipment that does not contain any of these potential connections to ground are placed on a
conductive plate that is connected to the test ground plane (see comment 1); this applies to both
non-powered and AC-powered equipment.
10.5.5 Procedure
(1)
Connect the 100 ohm calibration test resistor (RCAL) to the test circuit of figure 10.5-1.
(2)
Set the spectrum analyzer and tracking generator frequency range to 2 MHz to 30 MHz.
(3)
Adjust the tracking generator voltage to measure a VM of 0.316 Vrms across the calibration
test resistor of 100 ohm.
(4)
Connect the spectrum analyzer across the RL resistor (90 ohm).
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Telecommunications Industry Association
TR41.9-16-02-XXX
(5)
Adjust the 20 pF differential capacitor until a minimum voltage across the RL resistor is
obtained. This represents the highest degree to which the bridge can be balanced. The
result of this balance calibration should be at least 20 dB better than the requirement for
the applicable frequency band. If this degree of balance cannot be attained, further
attention should be given to component selection for the test circuit and its construction.
(6)
Reverse the polarity of the tip-and-ring pair under test. If the transverse voltage (VL)
changes by less than 1 dB, the calibration is acceptable. If the transverse voltage changes
by more than 1 dB, it indicates that the bridge needs further adjustment to accurately
measure the balance of the EUT. Repeat the calibration process until the measurements
differ by less than 1 dB while maintaining the balance noted in step (5) above.
(7)
Replace the calibration resistor with the tip-and-ring pair of the EUT.
(8)
Measure the voltage across the tip and ring of the EUT; this is the metallic reference
voltage (VM).
(9)
Measure the voltage across the RL resistor; this is the longitudinal voltage (VL).
(10) Calculate the balance using the following formula:
TransverseBalance 20logV M
V
L
Note: If the readings are, for example, taken in dBV, then the equation may be simplified to:
Balance ( dB )  V
M
( dBV )  V L ( dBV )
(11) Reverse the tip and ring connections of the EUT and repeat step (8) through step (10).
The lesser of the two results is the transverse balance of the EUT.
10.5.6 Alternative Methods
See Appendix C.
Note: The test method that is described in Appendix C may be more appropriate to use for
frequencies above 3 MHz.
10.5.7 Suggested Test Data
(1)
Frequencies tested.
(2)
Balance measured for the EUT.
(3)
Calibration balance measured.
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Telecommunications Industry Association
TR41.9-16-02-XXX
10.5.8 Comments
(1)
EUT that is not normally grounded should be set in its normal position directly on a
conductive plate. It is recommended that the overall area of the conductive plate be at
least 50% greater than that of the base of the EUT. This represents the closest proximity to
ground that is likely to be encountered by the EUT.
(2)
Interference from power frequency harmonics can be minimized by using test frequencies
midway between multiples of 60 Hz.
(3)
In some cases, EUT may apply internally generated signals to the test set. Such signals
should not be construed as part of the transverse balance test.
(4)
Test leads between the test fixture and the EUT will affect the calibration and EUT balance
measurements. Such cables must be in place when making the calibration balance
adjustments.
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Telecommunications Industry Association
T1
TR41.9-16-02-XXX
1:1 impedance ratio, 100 ohm wide-band transformer.
Optimally a dual-stator air-variable RF capacitor that maintains a constant
20pF
capacitance between stators while providing a variable capacitance from either
Differential
stator to ground.
3 pF
Composition RF capacitor
RCAL
100 ohms
RL
90 ohms: A non-inductive precision resistor
(1) The 3 pF capacitor may be placed on either line of the test set, as required, to obtain proper balancing of
the bridge.
(2) The effective output impedance of the tracking generator should match the 100 ohms test impedance. The
spectrum analyzer's input should be differentially balanced to measure VM.
FIGURE 10.5-1 TRANSVERSE BALANCE, FAST
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