E2v ELIIXA+ 16K CXP COLOR User Manual - Appendix C. Data Cables
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Appendix C. Data Cables
CXP cables and the separate lanes of a CXP-multi-cable shall be coaxial with a characteristic impedance
of 75Ω ± 4 Ω. When a series connection of CXP-cables is considered, all of the BNC connectors used
have to be of the 75Ω type, including any inline couplers.
A CXP cable and the separate lanes of a CXP-multi-cable shall have a return loss better than or equal to :
The maximum length of a CoaXPress cable is the lowest figure from three different requirements:
power supply voltage drop, high speed link requirements and low speed link requirements.
Power Supply Voltage Drop : A CXP cable and the separate lanes of a CXP multi-cable shall each
have a total DC roundtrip resistance of less than 4.98Ω for each of the coax cables.
High Speed Link Requirement : A CXP cable and the separate lanes of a CXP-multi-cable that are
specified for a given bit rate shall have an attenuation that is less or equal to the following
attenuation at its corresponding frequency (example with Belden 1694A Cable) :
Bit Rate (Gbps)
Maximum Attenuation (dB)
@ Frequency (GHz)
Belden 1694A (m)
1.250
-21.2
0.625
130
2.500
-26
1.25
110
3.125
-26.8
1.5625
100
5.000
-20.9
2.5
60
6.250
-15.8
3.125
40
Low Speed Link Requirement : A CXP cable and the separate lanes of a CXP-multi-cable shall have a
signal attenuation at 30 MHz of less than, or equal to, -4.74dB.
Cable Current Capacity : A CXP cable and the separate lanes of a CXP-multi-cable shall each be
designed to carry 1A in normal operation.
A CXP-cable and the separate lanes of a CXP-multi-cable shall have attenuation versus frequency
characteristic exhibiting cable-like behaviour over the frequency ranges as indicated in the table
below. A series connection of cables shall also fulfil this requirement as if it is one cable including all
of its connectors and inline couplers.
Frequency Range
Return Loss
0-500MHz
-20dB
500MHz – 3.2GHz
-15dB
Cable Rating (Gbps)
Frequency Range
From
To
1.250
1
0.625
2.500
1
1.25
3.125
1
1.5625
5.000
1
2.5
6.250
-15.8
3.125