Agilent Technologies N4962A Podręcznik Użytkownika Pobierz pdf (Strona 3)

BER Tester for Use with a Simple Electrical DUT for 10 Gb/s

Applications

The N4962A serial BERT 12.5 Gb/s can be used as a high-performance GPIB-

programmable BERT (bit error rate tester). This application is ideally suited for

measuring the errors caused by an electrical DUT operating at 10 Gb/s (9.85 to

11.35 Gb/s, to be exact).

A block diagram is shown in Figure 3; this setup is used to verify the perfor-

mance of the BERT. By connecting the OUT directly to the IN, the BERT will

measure the amount of signal degradation introduced by the coaxial cable – this

should result in BER=0 at most phase adjustment settings.

In this case, we are using the ‘precision timebase’, a high-precision trigger input on

the oscilloscope. This scope input can accept a higher frequency rate trigger signal,

and is connected to HF TrigO (a full-rate clock) on the BERT.

Even though we are using a more precise method of triggering the oscilloscope, the

performance of the DUT is slowing down the transition times and increasing RMS

jitter. The scope is shown making an ‘eye-mask’ measurement.

LF TrigO

HF TrigO

JitterI

EXT CKI

TX CKO

~IN

~OUT

OUT

RX CKI

RX CKO

TX CKI

N4962A serial BERT

12.5 Gb/s

Figure 3. Block diagram – BERT

veriﬁcation measurement

Another block diagram is shown in Figure 4; this setup is used to measure the

BER introduced by a simple single-ended electrical DUT. The two cables used to

connect the DUT to the output and input do not need to be phase-matched.

LF TrigO

HF TrigO

JitterI

EXT CKI

TX CKO

~IN

~OUT

OUT

RX CKI

RX CKO

TX CKI

N4962A serial BERT

12.5 Gb/s

DUT

Figure 4. Block diagram – BER

measurement of single-ended DUT

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