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 BAnalog FIR Filter

SHF reserves the right to change specifications and design without notice – SHF C681 B - V001 – June 30, 2020

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Description
The SHF C681 B 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 60 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 BInInττ∑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 B - V001 – June 30, 2020

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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.

Comment

900

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.

Comment

Vdata in

200

800

Eye Amplitude;
Single-ended

V1dB

200
100

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

Output Parameters

Output Amplitude

mVVoutSupply Voltage

VVcc

Supply Current

mA

Iee

Power Dissipation

W

Pd

300

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

2.5 x 0.7 mm
DC Power JackPower Requirements
+5250
1.25

1.38

@ VCC = +5V

Mechanical CharacteristicsConnectors

ΩDimensions

mmWeightg

50

1.85 mm (V) female
see page 790Conditions
Operating Temperature
1°CTambient

1535

Analog Bandwidth depends on the set filter characteristic (flat_maxBW)

SHF reserves the right to change specifications and design without notice – SHF C681 B - V001 – June 30, 2020

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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 B - V001 – June 30, 2020

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Typical FIR Filter Presets
Flat frequency responses for maximum bandwidth and maximum gain.
flat_maxBW_gain=-8dB
flat_gain=0dB

f-3dB

Frequency responses for a 3, 6 and 8 dB slope @ fNyquist = 28 GHz.

SHF reserves the right to change specifications and design without notice – SHF C681 B - V001 – June 30, 2020

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Typical Applications
Compensation of a low pass filtered signal at 53.1 GBit/s

Signal before equalization

Signal with equalization

Compensation of a 2.8 m TCF280 cable at 56 GBaud

Signals
beforeequalization

Signal withequalization(optimized)

NRZ

PAM4

SHF reserves the right to change specifications and design without notice – SHF C681 B - V001 – June 30, 2020

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Outline Drawing – Moduleb ca4x
Ø2.7

40
28

13.6

13.6

OutIn

SHF C681 B
InOut

51453551376

3

SHF Communication
Technologies AG+5 V DC

PortConnector

In

1.85mm (V) female

In1.85mm (V) femaleOut

1.85mm (V) femaleOut

1.85mm (V) female

13.63413.6

23.7

USB

354554Analog
FIR FilterAll dimensions are in mmPortConnectoraMini-USBbPowerc

Functional earth (FE)SHF reserves the right to change specifications and design without notice – SHF C681 B - V001 – June 30, 2020

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