SHF Communication Technologies AG
Wilhelm-von-Siemens-Str. 23D • 12277 Berlin • GermanyPhone +49 30 772051-0 • Fax +49 30 7531078
E-Mail: sales@shf.de • Web: http://www.shf.deDatasheet
SHF 78120 DSynthesized Clock Generator

SHF reserves the right to change specifications and design without notice – SHF 78120 D - V001 – Feb 12, 2018

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Description
The Synthesized Clock Generator SHF 78120 D is designed to provide our BERT customers with astandalone compact clock source featuring wide frequency range, adjustable output power, low jitter andlow harmonic levels.
It features a wide frequency range from 0.625 to 40 GHz with a 1 kHz resolution and a large outputpower (8 dBm up to 40 GHz). The output power can be adjusted in 0.1 dB steps.
For frequencies above 10 GHz, additional band-pass filtering ensures low harmonic levels. Up to 10 GHz,
short rise time clock signals are generated resulting in an increased level of higher-order harmonics.
The jitter injection functionality is integrated for jitter stress test applications. Arbitrary jitter types may beapplied to the clock signal by connecting an external signal source to the modulation input, enabling
various test scenarios such as compliance testing.
An additional trigger output provides a trigger signal whose frequency can be switched to a quarter orhalf the output frequency.

Block Diagram
Jitter Injection ON/OFFModulation In

fCLK
Synthesizer
Module10 MHz Ref Out
10 MHz Ref In

RF OutfCLK = 0.625 to 40 GHz

Jitter Injection
ModulefCLK /N

Trigger OutFeatures
Output clock frequency ranges from fCLK = 0.625 to 40 GHz with 1 kHz resolutionOutput power adjustable from –10 to +8 dBm with 0.1 dB resolution

External jitter injection using an external signal source such as SHF 19120 AWG

Supports three spread-spectrum clocking (SSC) modes10 MHz reference input and output for phase locking to other instrumentsRemote programming interface (Ethernet, USB) for automated measurements

SHF reserves the right to change specifications and design without notice – SHF 78120 D - V001 – Feb 12, 2018

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Ease of Use
The SHF 78120 D is controlled over a standard Ethernet or USB connection by an external computer (notpart of the delivery). Every system comes along with the intuitive, easy to use SHF Control Center. It
provides the interface for changing the device parameters, see screenshot below.
Additionally, the instrument may be programmed remotely over the Ethernet connection for automatedtests and measurements. Please refer to the SHF BERT Programming Manual.

SHF Control Center GUI

SHF reserves the right to change specifications and design without notice – SHF 78120 D - V001 – Feb 12, 2018

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Specifications
Parameter

Symbol

Unit

Min.

Typ.

Max.

CommentfCLK

GHz

0.625

Frequency Resolution

kHz1Frequency Accuracy

ppb

–250

250

Using internalreferenceFrequency Stability

ppb–50+50

Ambient
temperature 21°C

Frequency Stability Agingppb–300+300

per year

Clock Output (RF Out)Operating Frequency

40–10

Minimum Output PowerPout,mindBm

Maximum Output PowerPout,maxdBm+8Output Power Resolution

dB

0.1

Output Power Accuracy

dB–1

Output Power Temperature
DriftdB/°C

0.1

Harmonics/Spurious Signals

dBc

–20

Phase Noise

Jitter (RMS)

fs400

Ω

Output Impedance

For fCLK ≥ 10 GHz

For fCLK ≥ 10 GHz;on scope display (not1deconvolved)

50Connector
Parameter

Ambient
temperature 21°C

fCLK = 10 GHz
1 kHz offset
10 kHz offset
100 kHz offset
1 MHz offset–90–92–85–109

dBc/HzJRMS

12.92 mm (K) female
SymbolUnit

Min.

Typ.

Max.

Frequency

GHz

0.1562520

Output Amplitude

mVpp

400

1000

Output ImpedanceΩCommentTrigger Out

Connector

150
2.92 mm (K) female

Measured with Agilent 86100A, 70 GHz sampling head and precision time base triggered by Trig Out signal.

SHF reserves the right to change specifications and design without notice – SHF 78120 D - V001 – Feb 12, 2018

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External Jitter Injection
Modulation FrequencyMHz0.51000

Modulation Amplitude

mVpp

01200

Jitter Amplitude

ps050

Input ImpedanceΩPeak-to-peak

50Connector

2.92 mm (K) female

Spread Spectrum Clocking
Modulation Frequency

Hz10100 k

Deviation

ppm

020,000

Up/down/center

Ref InReference Frequency

frefMHzAmplitude

Vpp

Input Impedance

Ω100.2

3.3
50Connector

SMA female

Ref Out (using internal reference setting)2

Reference Frequency

MHz10Amplitude

Vpp

Output ImpedanceΩFrequency Accuracy

ppb

–250

250

Frequency Stability

ppb–50+50

Ambient
temperature 21°C

Frequency Stability Agingppb–300+300

per year0.850Connector

SMA female

GeneralPower Consumption

WWeightkg

Operating Temperature

°C

25
1.6
1.85
10+12V switching power
supply is included
without power supply
with power supply

35

Ambient temperature

2The specifications in this datasheet are only valid if the internal reference is activated. If the externalreference setting is activated the signal at Ref In is fed through to Ref Out. In this case the parameters
frequency, stability and amplitude depend on the Ref In signal.
SHF reserves the right to change specifications and design without notice – SHF 78120 D - V001 – Feb 12, 2018

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Typical Output Waveforms

16 GHz clock output at 4 dBm

20 GHz clock output at 4 dBm

32 GHz clock output at 4 dBm

40 GHz clock output at 4 dBm

Note that for clock frequencies above 10 GHz, the signal is band-pass filtered to achieve low harmonics
and a nearly pure sine wave. Below 10 GHz, however, the clock signals are amplified with subsequent
amplitude clipping to shorten the rise time. In the frequency range below 10 GHz, this generates
noticeable higher-order harmonics. The SHF 78120 D is optimized for clock source applications incombination with SHF BERT instruments, where a short rise time is preferred.

Output Amplitude
The output amplitude is factory-calibrated using a power meter. It can be varied from -10 to +8 dBm. By
default, the amplitude is software-limited to +4 dBm to prevent damage on connected devices. If required
the instrument can be configured to set the amplitude to the available hardware maximum. The typicalhardware maximum is +8 dBm. The amplitude can be set in 0.1 dB steps.
For clock frequencies above 10 GHz, the amplitude value in dBm, 𝑃𝑑𝐵𝑚 , can be converted from and to 𝑉𝑝𝑝using the following equations which are valid in a 50 Ω system:

𝑃𝑑𝐵𝑚 = 20 log10 (𝑉𝑝𝑝 ) + 4(Eq. 1)

𝑉𝑝𝑝 = 10(𝑃𝑑𝐵𝑚−4)/20.

(Eq. 2)

SHF reserves the right to change specifications and design without notice – SHF 78120 D - V001 – Feb 12, 2018

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Note that below 10 GHz, the measured 𝑉𝑝𝑝 will be slightly smaller than the value calculated from (Eq. 2)
since the clock signals in that frequency range are square waves rather than single-tone sine waves.

External Jitter Injection
For additional flexibility, arbitrary jitter injection may be applied to the high-speed clock signal. Jitter isinjected by connecting a signal source such as an arbitrary waveform generator to the external modulation
input. The maximum jitter amplitude is 50 ps peak-to-peak with a modulation bandwidth of up to 1 GHz. As
an example, the jitter amplitude of 50 ps corresponds to a relative jitter amplitude of 1.6 unit intervals (UI)
at a bit rate of 32 Gbit/s.
The jitter amplitude needs to be calibrated by the user.
In combination with an SHF Bit Pattern Generator and an Error Analyzer, the SHF 78120 D enables a test
solution for jitter tolerance tests as required by many telecommunication standards such as 100G Ethernet
and 40 GBit/s OTN, FibreChannel, InfiniBand, PCI Express®, and Serial ATA. For further details pleaserefer to the SHF application note „Jitter Injection using the Multi-Channel BPG“, available online atwww.shf.de.

 InfiniBand is a registered trademark of the InfiniBand Trade Association. PCI Express is a registeredtrademark of Peripheral Component Interconnect Special Interest Group (PCI-SIG).
SHF reserves the right to change specifications and design without notice – SHF 78120 D - V001 – Feb 12, 2018

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Typical Jittered Signal Waveforms
The external modulation input can be driven by a signal source such as the SHF 19120 arbitrary waveformgenerators (AWG). The waveform characteristics of the AWG determine the jitter type of the SHF 78120 D.
Sine Wave on Modulation Input
SHF 78120 D

Sinusoidal jitter on 28 GHz clock.
AWG SettingWaveform:

Sine wave

Gaussian-Distributed Noise on Modulation Input
SHF 78120 D

Random jitter on 28 GHz clock.
AWG Setting
Waveform:

Noise

Square Waveform on Modulation Input
SHF 78120 D

Peak-to-peak jitter on 28 GHz clock.
AWG Setting
Waveform:

SquareSHF reserves the right to change specifications and design without notice – SHF 78120 D - V001 – Feb 12, 2018

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Spread Spectrum Clocking
To meet the regulatory demands of electromagnetic interference several high-speed bus systems use aspread spectrum clocking (SSC) method. When SSC is enabled, the instantaneous frequency of the clock
signal varies periodically with time by a small amount, i.e. the clock signal is frequency-modulated. The
figure below illustrates the SSC frequency modulation with a triangular shape.
Instantaneous
Frequency

Frequency
DeviationTime
1/Modulation Frequency

The principle of SSC is the periodic frequency modulation of a clock signal.

The key SSC parameters are the following:
fCLK

original clock frequency without SSC

δrelative frequency deviation (often given in percent or ppm, parts per million)

fjittermodulation frequency.

The parameters are directly accessible in the SHF Control Center software or through remote
programming.
Depending on the relative position of the clock frequency and the frequency deviation, SSC can beclassified into three types: down, center, and up-spread. The figure below illustrates the three
configurations.

Down-Spread

Center-Spread

Up-Spread(1+δ) fCLK

Frequency(1+δ/2) fCLK
fCLK

fCLK

fCLK

(1–δ/2) fCLK

(1–δ) fCLK
1/fjitterTime

1/fjitter

TimeTime

1/fjitterThree types of SSC.

SSC effectively broadens the spectral peak of a clock signal so that the maximum of the power spectral
density is reduced leading to less radiated emission. This is illustrated in the following spectra measured at
the output of the SHF 78120 D for a 25 GHz clock with 30 kHz modulation frequency and 0.5% deviation.
Note that SSC does not reduce the total signal power of the clock. Rather, it redistributes the clock’s
spectral components as shown in the figure below.

SHF reserves the right to change specifications and design without notice – SHF 78120 D - V001 – Feb 12, 2018

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Without SSC

With SSC

Peak Reduction

SpectralBroadening

SHF 78120 D clock spectrum with and without SSC.

SHF reserves the right to change specifications and design without notice – SHF 78120 D - V001 – Feb 12, 2018

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Mechanical Drawing
SHF 78120 D

Synthesized Clock Generator
Modulation In

RF Out< 1 Vpp

1.2 Vpp Max< 8 dBm

PowerOutputs
OnOffOn
OffError

50.9Trig Out50  / 2.92 mm Female

50  / 2.92 mm Female

221.4

151.4
136.4
7.6

25.2

177.1

4 5

7.2

12339

24.2
59
99dbac50  / SMA Female

Ethernet
12 V / 3 A
USBService< 3.3 Vpp

3.3 Vpp Max

Ref Out

Ref InePos.
12345Designation
Trigger Output
Modulation Input
RF OutRef Out
Ref InConnector
2.92 mm (K) Female
2.92 mm (K) Female
2.92 mm (K) Female
SMA (K) Female
SMA (K) Female

Pos.
abcde

Designation
ServiceGND
Ethernet
Power Supply
USB

All dimensions are
specified inmillimeters (mm).

SHF reserves the right to change specifications and design without notice – SHF 78120 D - V001 – Feb 12, 2018

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