Simulation tool for high-speed communications links
A link simulation tool for simulating high-speed communications link systems is provided. Communications links may include link subsystems such as transmit (TX) circuitry, receive (TX) circuitry, oscillator circuits that provide reference clock signals to the TX and RX circuitry, and channels that link the TX and RX circuitry. The link simulation tool may model each of the subsystems using behavioral models. The behavioral models may include characteristic functions such as transfer functions, probability density functions, and eye characteristics. The link simulation tool may have a link analysis engine that is capable of performing two-dimensional (two-variable) convolution operations and in applying dual-domain (frequency-time) transformations on the characteristic functions provided by the behavioral models to simulate the performance of the link system. The link simulation tool may have an input screen that allows a user to specify desired link parameters and a data display screen that display simulated results.
1. A method of simulating a communications link using a link simulation tool implemented on computing equipment, wherein the communications link includes respective link subsystems and wherein the link subsystems in the communications link are represented by subsystem models in the link simulation tool, the method comprising:
performing two-dimensional convolution operations on the subsystem models to determine link performance for the communications link using the link simulation tool, wherein the two-dimensional convolution comprises convolution on expressions that are a function of time and voltage, wherein the link subsystems comprise a transmitter subsystem that is represented by a transmitter subsystem model in the link simulation tool, and wherein performing the two-dimensional convolution operations comprises performing two-dimensional convolution operations with the transmitter subsystem model.
2. The method defined in claim 1 , wherein the link subsystems comprise a receiver subsystem that is represented by a receiver subsystem model in the link simulation tool and wherein performing the two-dimensional convolution operations further comprises performing two-dimensional convolution operations with the receiver subsystem model.
3. The method defined in claim 2 , wherein the transmitter and receiver subsystems comprise transmitter and receiver subsystem components each of which is represented by a respective one of a plurality of characteristic functions, the method further comprising:
performing two-dimensional convolution operations on the plurality of characteristic functions.
4. The method defined in claim 3 , wherein the transmitter subsystem components of the communications link comprise components including: a first equalizer, a first phase-locked loop, a first oscillator, and a driver, and wherein the receiver subsystem components comprise components including: a buffer, a second equalizer, a second phase-locked loop, and a second oscillator.
5. The method defined in claim 4 , wherein performing the two-dimensional convolution operations on the characteristic functions comprises:
convolving the characteristic functions of the first equalizer, the first phase-locked loop, the first oscillator, and the driver to produce the transmitter subsystem model; and
convolving the characteristic functions of the buffer, the second equalizer, the second phase-locked loop, and the second oscillator to produce the receiver subsystem model.
6. The method defined in claim 1 , wherein the link subsystems comprise a channel subsystem that is represented by a channel subsystem model in the link simulation tool and wherein performing the two-dimensional convolution operations further comprises performing two-dimensional convolution operations with the channel subsystem model.
7. A method of simulating a communications link using a link simulation tool that is implemented on computing equipment, comprising:
with the link simulation tool, displaying a timing diagram for transmitted signals having varying signal amplitudes at a given point in the communications link;
with the link simulation tool, displaying a probability density function plot that represents a distribution of signal amplitude variations in the transmitted signals for the communications link; and
with the link simulation tool, displaying a first cumulative density function plot that is only a function of voltage and a second cumulative density function plot that is only a function of time.
8. The method defined in claim 7 , wherein displaying the timing diagram comprises displaying an eye diagram of the transmitted signals of the communications link.
9. The method defined in claim 7 , wherein displaying the probability density function plot comprises displaying a noise histogram plot for the transmitted signals for the communications link.
10. The method defined in claim 9 further comprising:
with the link simulation tool, displaying a jitter histogram plot for the transmitted signals for the communications link.
11. The method defined in claim 7 further comprising:
with the link simulation tool, displaying a three-dimensional bit error rate plot for the transmitted signals at the given point in the communications link.
12. A method of simulating a communications link using a link simulation tool implemented on computing equipment, comprising:
with the link simulation tool, providing a user with an opportunity to specify random jitter requirements for the communications link;
with the link simulation tool, providing the user with an opportunity to specify random noise requirements for the communications link;
with the link simulation tool, producing simulation results for the communications link based on the random jitter and noise requirements specified by the user; and
with the link simulation tool, providing the user with an opportunity to specify a target bit error rate for the communications link.
13. The method defined in claim 12 further comprising:
with the link simulation tool, providing the user with an opportunity to specify a data rate for the communications link.
14. The method defined in claim 12 , wherein producing the simulation results comprises displaying jitter and noise probability density function plots that are based on the random jitter and noise requirements specified by the user for the communications link.
15. A non-transitory computer-readable storage media for simulating performance in a communications link, comprising instructions for:
providing a user with an opportunity to specify link simulation settings for the communications link;
performing two-dimensional convolution operations to simulate performance in the communications link, wherein the two-dimensional convolution comprises convoluting a first function that is dependent on time with a second function that is dependent on voltage, wherein the communications link includes a transmitter subsystem that is represented by a transmitter subsystem model, and wherein performing the two-dimensional convolution operations comprises performing two-dimensional convolution operations with the transmitter subsystem model; and
displaying simulation results for the communications link produced by performing the two-dimensional convolution operations.