1.1 Fitted insertion loss
The fitted insertion loss ILfitted as a function of frequency f is defined in Equation (1).
IL fitted ( f ) = a1 f + a 2 f + a 4 f 2 dB
(1)
Given the cable assembly insertion loss IL measured between TP1 and TP4 over N frequencies fn spanning
50 MHz to 7500 MHz, the coefficients of the fitted insertion loss shall be calculated as follows.
Define the frequency matrix F as shown in Equation (2).
⎡ f1
⎢
f
F =⎢ 2
⎢ M
⎢
⎢⎣ f N
f1
f2
M
fN
f12 ⎤
⎥
f 22 ⎥
M ⎥
⎥
f N2 ⎥⎦
(2)
The polynomial coefficients a1, a2, and a4 shall be calculated as shown in Equation (3).
⎡ a1 ⎤
⎢a ⎥ = ( F T F ) −1 F T IL
⎢ 2⎥
⎢⎣a 4 ⎥⎦
(3)
In Equation (3), “T” denotes the matrix transpose operator and IL is a column vector of the measured
insertion loss values, ILn at each frequency fn.
The cable assembly insertion loss shall satisfy the requirements defined in Table 1. The fitted insertion loss
corresponding to the maximum insertion loss at 5.15625 GHz and the maximum allowed values of a1 , a2,
and a4 is illustrated in Figure 1.
Table 1 - Cable assembly insertion loss characteristics
Parameter
Condition
Units
Insertion loss at 5.15625 GHz
Max.
dB
Fitted insertion loss, a1
Max.
dB/root-GHz
Fitted insertion loss, a2
Max.
dB/GHz
Fitted insertion loss, a4
Max.
dB/GHz2
Note – The limit on the insertion loss at 5.15625 GHz prevents the coefficients a1, a2,
the maximum allowed values simultaneously.
Healey 7/15/2009
IEEE P802.3ba Task Force
Value
17.04
6.0
1.0
0.08
and a4 from having
1
Frequency (GHz)
0
1
2
3
4
5
6
7
8
0.00
Fitted insertion loss (dB)
5.00
10.00
15.00
20.00
25.00
Figure 1 - Illustration of fitted insertion loss
1.2 Insertion loss deviation
The insertion loss deviation ILD is the difference between the measured insertion IL and the fitted insertion
loss ILfitted as defined in Equation (4).
ILD( f ) = IL( f ) − IL fitted ( f )
(4)
The ILD shall be within the region defined by Equation (5) and Equation (6) for all frequencies from 50
MHz to 7500 MHz.
ILD( f ) ≥ ILDmin ( f ) = −0.7 − 0.0002 f dB
(5)
ILD( f ) ≤ ILDmax ( f ) = 0.7 + 0.0002 f dB
(6)
Healey 7/15/2009
IEEE P802.3ba Task Force
2
0.0000
0.0000
-2.0000
-0.2000
-4.0000
-0.4000
-6.0000
-0.6000
-8.0000
-0.8000
-10.0000
-1.0000
-12.0000
-1.2000
-14.0000
-25.00
-20.00
-15.00
-10.00
a4 (dB/GHz 2)
a1 (dB/root-GHz)
1.3 Justification for proposed requirements (NOT FOR INCLUSION IN THE DRAFT)
-1.4000
0.00
-5.00
SDD21 magnitude at fundamental (dB)
a1
a4
CA limit
Frequency (GHz)
0
1
2
3
4
5
6
7
8
0.00
Insertion loss (dB)
5.00
10.00
15.00
20.00
25.00
30.00
a1 = 6.0, a4 = 0.08
Healey 7/15/2009
Draft 2.1, 10 m
IEEE P802.3ba Task Force
Draft 2.1, 17.04 dB
3