What does a PRBS Generator do?
A PRBS generator is a standard piece of equipment that generates these desired PRBS test signals. It can be as simple as a connectorized PCB featuring an FPGA or ASIC or a highly sophisticated solution featuring a complete user interface. Since these signals are meant to test / evaluate parts under test, the signal quality tends to be extremely high (e.g. low jitter, sharp edges, minimal under/over shoot etc.). Most PRBS generators feature user programmable variable data rates, signal amplitudes and delays. Some come with multiple outputs usually in even pairs ranging from 2 up to 16. The parallel outputs can be phase and/or pattern matched or phase shifted in such a way that when multiplexed, they produce an identical pattern at a higher data rate.
What is a PRBS?
Pseudo random binary sequences (PRBS) signaling is commonly used in telecommunications test laboratories. The binary sequence, while generated with a deterministic algorithm, is difficult to predict. PRBS signals exhibit statistical behavior similar to truly random sequences. This is in contrast to using clock signals or limited data words as data test signals, which are far from being random. Only a random signal (or one as close as possible) truly tests the functionality of the part under test. The PRBS signals commonly found in telecom labs range from 27-1 up to 231-1.
What are some application of the PRBS Generator?
Common applications of PRBS generators are to evaluate the performance of individual ICs all the way up to complex systems that process data. Simple low level tests can involve using the PRBS signal as a data input to a device and observing the output of that device and how it differs from the test signal. Depending on what reference signal is being used on the oscilloscope, one can observe the individual bits (if the PRBS power is low enough) or the eye diagram.
How does the PRBS Generator solve a problem?
PRBS generators are frequently paired up with error detectors to test the error rates of ICs and systems. A typical setup involves again using the PRBS signal as an input data signal and then using the error detector at the output to ensure no errors are produced. Since these two functions are commonly utilized together, there are many products on that market that feature both. These solutions are generally referred to as bit error rate detectors or BERTs (Bit Error Rate Tester).
A few examples of ADSANTEC PRBS Generators and BERTs:
ADSANTEC has several PRBS generator offerings. These include the ASNT_PRBS45, ASNTPRBS56, ASNTPRBS20_1 and ASNT_MPSG. The ASNT_PRBS45 works from 100Mb/s to 45Gbps and can out PRBS patterns from 27-1 to 231-1 including 9, 11, 15, 17, 20, 23, and 29. The ASNTPRBS56 is similar, but works up to 56Gb/s. Finally, the ASNT_MPSG outputs 4 parallel phase matched PRBS signals ranging from 100Mb/s to 40Gbps. All solutions feature signaling with exceptional quality including low jitter and fast rise/fall times.
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