Removal of channel impairments due to skew and channel asymmetry with a composite filter
In one embodiment, a transmission system includes a transmitter, a receiver, and a filter operable at one of the transmitter and the receiver to remove channel impairments. The filter is operable according to a sum of a Gaussian function and a reciprocal of cosine function, wherein the Gaussian and reciprocal of cosine functions comprise tunable parameters to account for skew and channel asymmetry.
1. A transmission system comprising:
a transmitter;
a receiver; and
a filter operable at one of the transmitter and the receiver to remove channel impairments;
the filter operable according to a sum of a Gaussian function and a reciprocal of cosine function, wherein said Gaussian function and said reciprocal of cosine function comprise tunable parameters to account for skew and channel asymmetry.
2. The transmission system of claim 1 wherein the skew comprises time delay skew, rise and fall time skew, and amplitude skew.
3. The transmission system of claim 1 wherein the filter comprises a band pass filter with shaping for use in equalization.
4. The transmission system of claim 1 wherein said tunable parameters comprise frequency, a Gaussian variable, a standard deviation variable, and a skew variable.
5. The transmission system of claim 1 wherein the sum of said Gaussian function and said reciprocal of cosine function is defined as:
T
=
∑
i
=
1
n
1
2
π
μ
i
e
-
1
2
(
f
-
f
i
0
σ
i
)
2
+
1
cos
(
π
t
skew
f
)
;
wherein f is a frequency, f i o is a tunable frequency parameter; σ i is a tunable Gaussian variable, μ i is a tunable standard deviation variable of said Gaussian function, and t skew is a tunable skew parameter.
6. The transmission of system of claim 1 wherein at least some of said tunable parameters are defined based on an impulse response at the receiver.
7. The transmission system of claim 1 wherein the filter operates at the receiver.
8. The transmission system of claim 1 wherein the filter operates at the transmitter.
9. The transmission system of claim 1 wherein the transmission system operates in a pulse amplitude modulation serializer/deserializer and the transmission system further comprises a continuous time linear equalizer located after the filter.
10. A method comprising:
receiving at a receiver, a transmission signal from a transmitter;
filtering the data with a composite Gaussian and reciprocal of cosine filter to remove channel impairments; and
tuning tunable parameters of the composite Gaussian and reciprocal of cosine filter to account for skew and channel asymmetry.
11. The method of claim 10 wherein the skew comprises time delay skew, rise and fall time skew, and amplitude skew.
12. The method of claim 10 wherein the composite Gaussian and reciprocal of cosine filter comprises a band pass filter with shaping for use in equalization.
13. The method of claim 10 wherein said tunable parameters comprise frequency, a Gaussian variable, a standard deviation variable, and a skew variable, and wherein said tunable parameters are defined based on insertion loss deviation.
14. The method of claim 10 wherein Gaussian and reciprocal of cosine functions of the composite Gaussian and reciprocal of cosine filter operate according to:
T
=
∑
i
=
1
n
1
2
π
μ
i
e
-
1
2
(
f
-
f
i
0
σ
i
)
2
+
1
cos
(
π
t
skew
f
)
;
wherein f is a frequency, f i o is a tunable frequency parameter; σ i is a tunable Gaussian variable, μ i is a tunable standard deviation variable of said Gaussian function, and t skew is a tunable skew parameter.
15. The method of claim 10 wherein at least some of said tunable parameters are defined based on an impulse response at the receiver.
16. A method comprising:
receiving transmission data at a transmitter;
filtering the transmission data with a composite Gaussian and reciprocal of cosine filter to remove channel impairments;
tuning tunable parameters of the composite Gaussian and reciprocal of cosine filter to account for skew;
generating a transmission signal; and
transmitting the transmission signal to a receiver.
17. The method of claim 16 wherein the skew comprises time delay skew, rise and fall time skew, and amplitude skew.
18. The method of claim 16 wherein the composite Gaussian and reciprocal of cosine filter comprises a band pass filter with shaping for use in equalization.
19. The method of claim 16 wherein said tunable parameters comprise frequency, a Gaussian variable, a standard deviation variable, and a skew variable.
20. The method of claim 16 wherein the composite Gaussian and reciprocal of cosine filter operates in combination with a continuous time linear equalizer.