Transmission line with low dispersive properties and its application in equalization
View Patent ↗A transmission line is provided with added shunt resistance, R SH , distributed along the length of the micro transmission line permitting the extension of constant characteristic impedance to the transmission line to lower signal frequencies. The loss in gain to the signal propagating the transmission line due to the added resistance can be compensated for by amplification provided at the output of the transmission line or at output taps provided along the length of the transmission line such as in cases where the line is utilized as a circuit delay line. An exemplified application disclosed is an analog delay line formed as a metal microstrip in an IC chip circuit provided, for example, in a feed forward equalizer (FFE).
1. A transmission line, comprising:
a plurality of delay segments; and
a plurality of output taps, each of which being coupled to a corresponding one of the plurality of delay segments,
wherein each of the plurality of delay segments has a first shunt resistance, a second shunt resistance, and a series resistance, such that a sum of the first shunt resistance and the second shunt resistance matches the series resistance and a signal delay response associated with the transmission line is substantially flat.
2. The transmission line of claim 1 wherein an amplifier is provided at each of the plurality of output taps.
3. The transmission line of claim 1 wherein the transmission line is a metal microstrip integrated circuit delay line in a feed forward equalizer (FFE).
4. The transmission line of claim 1 wherein the second shunt resistance is distributed along a length of the transmission line.
5. The transmission line of claim 4 wherein the second shunt resistance is provided between adjacent ones of the plurality of delay segments.
6. The transmission line of claim 5 wherein the plurality of delay segments is a plurality of first delay segments, the transmission line further including a second delay segment provided at a first end of the transmission line and a third delay segment at a second end of the transmission line, the second delay segment having a third shunt resistance that is twice that of the first shunt resistance and the third delay segment having a fourth shunt resistance that is twice that of the first shunt resistance.
7. The transmission line of claim 1 wherein the transmission line has an output and a third shunt resistance provided at the output of the transmission line.
8. The transmission line of claim 7 wherein an amplifier is provided at the output of the transmission line.
9. A feed forward equalizer (FFE) comprising:
a transmission line including a plurality of delay segments;
a plurality of output taps, each of which being coupled to a corresponding one of the plurality of delay segments, such that each of the plurality of output taps is provided between adjacent ones of the plurality of delay segments;
a plurality of amplifiers;
a plurality of weighted stages each of which being coupled to a corresponding one of the plurality of amplifiers; and
a summation circuit coupled to each of the plurality of amplifiers,
wherein each of the plurality of delay segments has a series resistance and a shunt resistance, the shunt resistance matching the series resistance.
10. The feed forward equalizer (FFE) of claim 9 wherein each of the plurality of weighted stages comprises a multiplier circuit with a weighted value input.
11. A method of providing a transmission line, comprising:
forming a plurality of delay segments; and
forming a plurality of output taps, each of which being coupled to a corresponding one of the plurality of delay segments,
wherein each of the plurality of delay segments has a first shunt resistance, a second shunt resistance, and a series resistance, such that a sum of the first shunt resistance and the second shunt resistance matches the series resistance and a signal delay response associated with the transmission line is substantially flat.
12. The method of claim 11 comprising the further step of providing the second shunt resistance at an input or output of each of the plurality delay segments.
13. The method of claim 12 comprising the further step of coupling each of a plurality of amplifiers to a corresponding one of the plurality of output taps.
14. The method of claim 11 comprising the further step of providing the transmission line in an IC chip.
15. The method of claim 14 wherein the transmission line is a micro metal stripline in the IC chip.
16. The method of claim 11 comprising the further step of coupling each of a plurality of amplifiers to a corresponding one of the plurality of output taps.
17. The method of claim 16 comprising the further steps of
coupling each of a plurality of weighted stages to a corresponding one of the plurality of amplifiers; and
coupling a summation circuit to each of the plurality of amplifiers.
18. The method of claim 17 comprising the further step of providing the transmission line in a serpentine path on an IC chip.