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FIR Filter for up to 70 GBaud PAM4

Feb 23, 2023 | New products

SHF is going to release a new stand-alone analog (clockless) FIR equalization module for speeds up to 70 GBaud PAM4. The SHF C683 A can significantly improve the quality of heavily degraded signals. It literally opens up your eyes.

The following pictures show 64 GBaud (128 Gbps) PAM4 signals measured with a high-speed sampling scope in its original state (e.g. degraded by a DUT) and improved by equalization through the SHF C683 A.

64 GBaud Input and Output of SHF C683 A

Measured 64 GBaud (128 Gbps) input and output signal of a SHF C683 A

Comparing these measured eye diagrams with the signals calculated by the complementary software “SHF-Optimizer” shows how accurate the software predicts the reality. The calculated signals at different stages in the signal chain are shown below.

The SHF-Optimizer bases its calculation either on ideal inputs, imported signal traces or measurements directly acquired from supported sampling oscilloscopes. Additionally, these signals can be distorted or modified (e.g. by loading s-parameter files). The result is used by the software for a fast and quick calculation of the output eye, the frequency response and the group delay of the signal chain without optimization.

SHF Optimizer - responses and signals of the calculated distorted signal

Responses and signals of the calculated distorted signal
(without SHF C683 A Filter)

The SHF-Optimizer does the tap calculation for the SHF C683 A with regard to SNR, jitter, eye heights, or a combination of these. The preview of the calculated optimized signal shows the output eye and frequency responses. One may note that while the optimization is done for best time domain performance, the insertion loss becomes smooth and Bessel shaped. The group delay will also be improved.
SHF Optimizer - responses and signals of the calculated optimized signal

Responses and signals of the calculated optimized signal
(with SHF C683 A Filter)

Another unique feature of the SHF C683 A is its ability to emulate various RF and microwave modules. If a DUT is not physically available, the SHF C683 A can mimic that DUT based on loaded s-parameters or for ideal components like cables, PCB traces, Bessel filters, attenuators or amplifiers within certain ranges.

Key Features – SHF C683 A

  • Bandwidth > 55 GHz (suitable for PAM4 signals from 20 to 70 GBaud)
  • 6 taps
  • Compensates insertion losses of up to 12 dB
  • Input signals up to 350 mV single-ended or differential
  • Differential input and output ports can also be used single-ended (even mixed configurations)
  • Compact module is flexible enough to be placed wherever adaptive equalization is required

The full data sheet is available in our “RF & Microwave Modules and Instruments” product section.