SHF Communication Technologies AG
Wilhelm-von-Siemens-Str. 23D • 12277 Berlin • Germany
Phone +49 30 772051-0 • Fax +49 30 7531078
E-Mail: sales@shf-communication.com • Web: www.shf-communication.com

Datasheet
SHF C681 AAnalog FIR Filter

SHF reserves the right to change specifications and design without notice – SHF C681 A - V001 – November 18, 2019 Page 1/6

Description
The SHF C681 A is a tunable analog 6-tap finite impulse response (FIR) filter. The differential input
signal is amplified and filtered by a 6-stage FIR filter structure with fixed tap delays of ~7.5 ps. The
frequency response can be arbitrarily modified by adjusting the filter coefficients i.e. the gain of the tap
amplifiers in the GUI.
Equalizing operation has been verified for heavily degraded signals up to 60 GBaud PAM4 and 80 Gbps
NRZ (please be referred to the signals below).
All RF in- and output ports are AC-coupled and internally terminated with 50 Ohm to GND. Unused in- oroutput ports should be terminated with 50 Ohm.

Features

Differential data input and output
Complementary DSP software (“SHF FIR”) to calculate the optimum settings from s2p files
Compact module to be placed wherever adaptive equalization is required e.g. close to the DUTApplications

Quality Improvement of a degraded signal e.g. for BER measurements
Equalization of transmission channels
Signal predistortion to simulate various transmission channels
100GbE, 200GbE, 400GbE and 1TbE system evaluation & development
Telecom transmission
Broadband test and measurement equipment
Feed forward equalization (FFE)Block Diagram
SHF
C681 AInτInτ∑τ∑τ∑Equalizerτ∑OutOut∑

USB+5VAccessories
 +5V power supply desktop adapter
 Functional earth cable Mini-USB cable

SHF reserves the right to change specifications and design without notice – SHF C681 A - V001 – November 18, 2019 Page 2/6

Absolute Maximum Ratings
Parameter

Unit

SymbolData Input Voltage

mVVdata inExternal DC Voltage on
Data Input Ports

VVDCinExternal DC Voltage on
RF Output PortsV

DC Supply Voltage

Min.

Typ.

Max.

Comment900

Peak-to-Peak-6+6AC coupled input

VDCout-6+6AC coupled output

VVcc

0+6Unit

SymbolMin.

Maximum Analog Bandwidth

GHz

f-3dB

55

Data Input Voltage

mV

1 dB Compression

mV

Input Parameters

Specifications
Parameter

Typ.

Max.

CommentVdata in

200

800

Eye Amplitude;
Single-ended

V1dB

200
100

Input Parameters
1Eye Amplitude;
Single ended drive;
Differential drive

Output Parameters

Output Amplitude

300

Eye Amplitude;
Single-ended;
Depending on tap
settings+5.5

2.5 x 0.7 mm
DC Power Jack

mV

Vout

Supply Voltage

VVcc

Supply Current

mAIee

Power Dissipation

W

Pd

1.25

1.38°C

Tambient

1535

Power Requirements+5250@ VCC = +5VConditions
Operating Temperature

1 Analog Bandwidth depends on the set filter characteristic
SHF reserves the right to change specifications and design without notice – SHF C681 A - V001 – November 18, 2019 Page 3/6

Remote Interface & Software
The Filter is controlled by the easy to use software package SHF Control Center (SCC).

The Filter settings can be derived and optimized by a dedicated DSP program package “SHF FIR”.

SHF reserves the right to change specifications and design without notice – SHF C681 A - V001 – November 18, 2019 Page 4/6

Typical Applications

Compensation of a 30 GHz Bessel Filter at 80 Gbit/s

Before equalization
S/N: 3.3

Optimized for 15 dB loss
S/N: 5.1

Optimized for 15 dB loss
S/N: 5.8

Compensation of 2.8 m TCF280 cable at 56 GBaud

Before equalization

Optimized

NRZ

PAM4

SHF reserves the right to change specifications and design without notice – SHF C681 A - V001 – November 18, 2019 Page 5/6

Outline Drawing – Moduleb ca4x
Ø2.7

40
28

13.6

13.6

OutIn

SHF C681 AInOut

51453551376

3SHF Communication
Technologies AG+5 V DCPortConnector

In

1.85mm (V) female

In1.85mm (V) femaleOut

1.85mm (V) femaleOut

1.85mm (V) female

13.6

3413.6

23.7

USB354554

AnalogFIR Filter

All dimensions are in mmPortConnectoraMini-USBbPowerc

Functional earth (FE)SHF reserves the right to change specifications and design without notice – SHF C681 A - V001 – November 18, 2019 Page 6/6