RF Signal Generators
SG380 Series — DC to 2 GHz, 4 GHz and 6 GHz analog signal generators

SG380 Series RF Signal Generators· DC to 2 GHz, 4 GHz or 6 GHz· 1 µHz resolution· AM, FM, ΦM, PM and sweeps· OCXO timebase (std.)· −116 dBc/Hz SSB phase noise(20 kHz offset, f = 1 GHz)
· Rubidium timebase (opt.)· Square wave clock outputs (opt.)· Analog I/Q inputs (opt.)· Ethernet, GPIB, and RS-232· SG382 ... $3,900 (U.S. list)· SG384 ... $4,900 (U.S. list)· SG386 ... $5,900 (U.S. list)

Stanford Research Systems

Introducing the new SG380 Series RF Signal Generators —finally, high performance, affordable RF sources.
The SG380 Series RF Signal Generators use a unique,innovative architecture (Rational Approximation Frequency
Synthesis) to deliver ultra-high frequency resolution (1 µHz),
excellent phase noise, and versatile modulation capabilities(AM, FM, ΦM, pulse modulation and sweeps) at a fraction of
the cost of competing designs.
The standard models produce sine waves from DC to
2.025 GHz (SG382), 4.05 GHz (SG384) and 6.075 GHz(SG386). There is an optional frequency doubler (Opt. 02)
that extends the frequency range of the SG384 and SG386 to
8.10 GHz. Low-jitter differential clock outputs (Opt. 01) areavailable, and an external I/Q modulation input (Opt. 03) isalso offered. For demanding applications, the SG380 Series
can be ordered with a rubidium timebase (Opt. 04).
On the Front Panel
The SG380 Series Signal Generators have two front-panel
outputs with overlapping frequency ranges. A BNC provides
outputs from DC to 62.5 MHz with adjustable offsets andamplitudes from 1 mV to 1 Vrms into a 50 Ω load. An
N-type output supplies frequencies from 950 kHz to the upper
frequency limit of each model, with power from +16.5 dBm to–110 dBm (1 Vrms to 0.707 µVrms) into a 50 Ω load.

phone: (408)744-9040
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SG380 Series RF Signal Generators

Modulation

SG380 Series Phase Noise vs. Offset Frequency

Unlike traditional analog signal generators, the SG380 Series
can sweep continuously from DC to 62.5 MHz. And for
frequencies above 62.5 MHz, each sweep range covers morethan an octave.
OCXO or Rubidium Timebase

-40
-50
-60

OffsetPhase Noise (dBc/Hz)

The SG380 Signal Generators offer a wide variety ofmodulation capabilities. Modes include amplitude modulation(AM), frequency modulation (FM), phase modulation (ΦM),
and pulse modulation. There is an internal modulation
source as well as an external modulation input. The internal
modulation source produces sine, ramp, saw, square, and noise
waveforms. An external modulation signal may be applied to
the rear-panel modulation input. The internal modulation
generator is available as an output on the rear panel.

-70
-80
-90
-100

4 GHz

-110

1 GHz

-120

100 MHz
10 MHz

-130
-140
-150

The SG380 Series come with a oven-controlled crystal
oscillator (OCXO) timebase. The timebase uses a thirdovertone stress-compensated 10 MHz resonator in athermostatically controlled oven. The timebase provides very
low phase noise and very low aging. An optional rubidium
oscillator (Opt. 04) may be ordered to substantially reduce
frequency aging and improve temperature stability.
The internal 10 MHz timebase (either the standard OCXO or
the optional rubidium reference) is available on a rear-panel
output. An external 10 MHz timebase reference may besupplied to the rear-panel timebase input.
Square Wave Clock Outputs
Optional differential clock outputs (Opt. 01) are available on
the rear panel which makes your SG380 a precision clock

10

100

1,000

10,000100,000

1,000,000 10,000,000

Frequency Offset (Hz)The SG380 Series always synthesizes a frequency inthe top octave and digitally divides to generate outputs
at lower frequencies. Doing so creates phase noisecharacteristics which scale with output frequency by
6 dB/octave or 20 dB/decade.
The low phase noise at small offsets (forexample, –80 dBc/Hz at 10 Hz offset from 1 GHz)is attributable to the low phase noise OCXO timebasereference oscillator. An important figure of merit forcommunications applications is the phase noise at
20 kHz offset, which is about –116 dBc/Hz at 1 GHz.

Differential Clock Outputs

Amplitude Modulation (100 %)Option 01 provides differential clock outputs inaddition to sine outputs. The clocks have transition
times of about 35 ps. Both the offset and amplitude of
the clock outputs can be adjusted for compliance withstandard logic levels. Shown here at 2 ns/division:
100 MHz front-panel sine wave output (top trace)and differential clock outputs (bottom traces). The
displayed transition times are limited by the 1.5 GHz
bandwidth of the oscilloscope.

The frequency range of the SG380 Series extends fromDC to 2 GHz, 4 GHz or 6 GHz (depending on model).
All of the analog modulation modes also extend to DC
allowing your SG380 to perform function generator
tasks. Shown here is a 20 kHz carrier being amplitude
modulated by a 1 kHz sine.

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Top trace: Modulation output
Bottom trace: Front-panel BNC output

SG380 Series RF Signal Generators

generator in addition to a signal generator. Transition times
are typically 35 ps, and both the offset and amplitude of theclock outputs can be adjusted for compliance with PECL,ECL, RSECL, LVDS, CML, and NIM levels.
I/Q Inputs
Optional I/Q inputs (Opt. 03) allow I & Q baseband signals tomodulate carriers from 400 MHz to the upper frequency limitof your instrument. This option also allows the I/Q modulator
to be driven by an internal noise generator with adjustablebandwidth. Rear-panel outputs allow the noise source to beviewed or used for other purposes.
I/Q Modulation of 1 GHz Carrier byInternal Noise Generator

Option 03 allows I/Q modulation of carriers
from 400 MHz to the upper frequency limit of yourinstrument. Two signal sources may be used for I/Q
modulation: external I & Q inputs or an internal
noise generator. The external I & Q BNC inputs areon the rear panel. The internal noise generator
has adjustable noise bandwidth. Shown here is a
1 GHz carrier being modulated by the internal noise
generator with 1 kHz noise bandwidth.

Output Frequency Doubler
The SG384 and SG386 can be ordered with a frequency doubler(Opt. 02) that extends the frequency range to 8.10 GHz. The
amplitude of the rear-panel RF output can be adjusted from–10 dBm to +13 dBm. This option also comes with a bias
source output which can be set with 5 mV resolution over
±10 VDC.
Easy Communication
Remote operation is supported with GPIB, RS-232 andEthernet interfaces. All instrument functions can be controlled
and read over any of the interfaces. Up to nine instrument
configurations can be saved in non-volatile memory.
A New Frequency Synthesis Technique
The SG380 Series Signal Generators are based on a new
frequency synthesis technique called Rational Approximation
Frequency Synthesis (RAFS). RAFS uses small integer
divisors in a conventional phase-locked loop (PLL) tosynthesize a frequency that would be close to the desired
frequency (typically within ±100 ppm) using the nominal PLL
reference frequency. The PLL reference frequency, which issourced by a voltage controlled crystal oscillator that is phaselocked to a dithered direct digital synthesizer, is adjusted sothat the PLL generates the exact frequency. Doing so provides
a high phase comparison frequency (typically 25 MHz)
yielding low phase noise while moving the PLL reference
spurs far from the carrier where they can be easily removed.
The end result is an agile RF source with low phase noise,essentially infinite frequency resolution, without the spurs offractional-N synthesis or the cost of a YIG oscillator.

Spectrum of Frequency Modulated 50 MHz Carrier
Unmodulated Spectrum of a 1 GHz Output

The SG380 Series outputs exhibit low phase noise andlow spurious content. In this direct measurement takenwith 100 Hz RBW, the noise floor of the spectrum
analyzer dominates over most of the 200 kHz span.

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Outputs below 62.5 MHz are generated by directdigital synthesis with a sample frequency of 1 GHz. In
this example, a 50 MHz carrier is frequency modulated
at a rate of 10 kHz and a deviation of 24.0477 kHz,for a modulation index β = 2.40477. The carrier
amplitude is proportional to the Bessel function J0(β),
which has its first zero at 2.40477.

phone: (408)744-9040
www.thinkSRS.com

SG380 Series RF Signal Generators

Polar Plot of 1.000001 GHz Referenced
to 1 GHz with 100 % AM at 5 kHz

The polar plot shows the trajectory of a signal in the
I/Q plane. An unmodulated carrier at the analyzer’s
reference frequency (1 GHz in this case) appears as asingle dot in the I/Q plane. When the carrier frequency
is offset, the single dot moves in a circle about thecenter of the I/Q plane. The pattern shown occurs
when the carrier amplitude is modulated with 100 %depth at a rate of five times the carrier offset frequency(creating five lobes). The symmetry of the lobes
indicates that there is no residual phase distortion(AM to ΦM conversion) in the amplitude modulator.
The narrow line of the trajectory is indicative of low
phase and amplitude noise.

SG384 rear panel

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Ordering Information
SG382
SG384
SG386
Option 01
Option 02
Option 03
Option 04
RM2U-S
RM2U-D

2 GHz signal generator
4 GHz signal generator
6 GHz signal generator
Rear-panel clock outputs
8 GHz doubler & DC bias
(SG384 and SG386 only)
External I/Q modulation
Rubidium timebase
Single rack mount kit
Dual rack mount kit

SG384 front panelSG380 Series Specifications

SG380 Series Specifications

20 kHz offset

Frequency Setting

1 MHz offset

Frequency ranges
SG382
SG384
SG386
Frequency resolution
Switching speed
Frequency error
Frequency stability

DC to 62.5 MHz (BNC output, all models)
950 kHz to 2.025 GHz (N-type output)
950 kHz to 4.05 GHz (N-type output)
4.05 GHz to 8.1 GHz (w/ Opt. 02)
950 kHz to 6.075 GHz (N-type output)
6.075 GHz to 8.1 GHz (w/ Opt. 02)
1 µHz at any frequency<8 ms (to within 1 ppm)<(10–18 + timebase error) × fC
1 × 10–11 (1 s Allan variance)

Residual FM (typ.)Residual AM (typ.)* Spurs, phase noise and residual FM scale by 6 dB/octave to othercarrier frequencies
Phase Setting on Front-Panel Outputs
Max. phase step
Phase resolution

Front-Panel BNC Output
Frequency range
Amplitude
OffsetOffset resolution
Max. excursion
Amplitude resolution
Amplitude accuracy
Harmonics
Spurious
Output couplingUser load
Reverse protection

DC to 62.5 MHz
1.00 Vrms to 0.001 Vrms
±1.5 VDC
5 mV
1.817 V (amplitude + offset)
<1 %
±5 %
<–40 dBc<–75 dBc
DC, 50 Ω ±2 %50 Ω
±5 VDC

Oscillator type
Stability (0 to 45 ºC)
Aging

Oscillator typePhysics package
Stability (0 to 45 ºC)
Aging

Frequency range
SG382
SG384
SG386
Power output
SG382
SG384
SG386
Voltage output
SG382
SG384
SG386
Power resolution
Power accuracy
Output couplingUser load
VSWR
Reverse protection

Frequency
Amplitude
Input impedance

1.5 Vrms to 0.7 µVrms
1.5 Vrms to 0.7 µVrms (<3 GHz)
1.5 Vrms to 0.7 µVrms (<4 GHz)
0.01 dBm±1 dB
AC, 50 Ω
50 Ω<1.6
30 VDC, +25 dBm RF

Spectral Purity of the RF Output Referenced to 1 GHz*
Sub harmonics
Harmonics
Spurious<10 kHz offset>10 kHz offset
Phase noise (typ.)
10 Hz offset
1 kHz offset

None<–25 dBc (<+7 dBm, N-type output)<–65 dBc<–75 dBc–80 dBc/Hz–102 dBc/Hz

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Oven controlled, 3rd OT, SC-cut crystal<±0.002 ppm<±0.05 ppm/year

Rubidium Timebase (Opt. 04)

Timebase Input+16.5 dBm to –110 dBm+16.5 dBm to –110 dBm (<3 GHz)
+16.5 dBm to –110 dBm (<4 GHz)±360º
0.01º (DC to 100 MHz)
0.1º (100 MHz to 1 GHz)
1.0º (1 GHz to 8.1 GHz)

Standard OCXO Timebase

Front-Panel N-Type Output
950 kHz to 2.025 GHz
950 kHz to 4.050 GHz
950 kHz to 6.075 GHz–116 dBc/Hz (SG382 & SG384)–114 dBc/Hz (SG386)–130 dBc/Hz (SG382 & SG384)–124 dBc/Hz (SG386)
1 Hz rms (300 Hz to 3 kHz BW)
0.006 % rms (300 Hz to 3 kHz BW)

Oven controlled, 3rd OT, SC-cut crystal
Rubidium vapor frequency discriminator<±0.0001 ppm<±0.001 ppm/year

10 MHz, ±2 ppm
0.5 to 4 Vpp (–2 dBm to +16 dBm)
50 Ω, AC coupled

Timebase Output
Frequency
SourceAmplitude

10 MHz, sine
50 Ω, DC transformer coupled
1.75 Vpp ±10 % (8.8 dBm ± 1 dBm)

Internal Modulation Source
Waveforms
Sine THD
Ramp linearity
Rate

Sine, ramp, saw, square, pulse, noise–80 dBc (typ. at 20 kHz)
<0.05 % (1 kHz)
1 µHz to 500 kHz(fC ≤ 62.5 MHz (SG382 & SG384))(fC ≤ 93.75 MHz (SG386))
1 µHz to 50 kHz(fC > 62.5 MHz (SG382 & SG384))(fC > 93.75 MHz (SG386))
Rate resolution
1 µHz
Rate error
1:231 + timebase error
Noise function
White Gaussian noise (rms = dev / 5)
Noise bandwidth
1 µHz < ENBW < 50 kHz
Pulse generator period 1 µs to 10 s
Pulse generator width 100 ns to 9999.9999 ms
Pulse timing resolution 5 ns
Pulse noise function
PRBS 25 – 219. Bit period (100 + 5N) ns

phone: (408)744-9040
www.thinkSRS.com

SG380 Series Specifications

Modulation Waveform Output
Output impedanceUser load
AM, FM, ΦM
Pulse/Blank

50 Ω (for reverse termination)
Unterminated 50 Ω coax
±1 V for ± full deviation“Low” = 0 V, “High” = 3.3 VDC

Ext. FM carrier offset <1:1,000 of deviation
Modulation bandwidth 500 kHz(fC ≤ 62.5 MHz (SG382 & SG384))(fC ≤ 93.75 MHz (SG386))
100 kHz(fC > 62.5 MHz (SG382 & SG384))(fC > 93.75 MHz (SG386))

External Modulation Input
Modes
Unmodulated level
AM, FM, ΦM
Modulation bandwidth
Modulation distortion
Input impedance
Input offset
Pulse/Blank threshold

AM, FM, ΦM, Pulse, Blank
0 V input for unmodulated carrier±1 V input for ± full deviation>100 kHz<–60 dB
100 kΩ<500 µV+1 VDCFrequency Sweeps (Phase Continuous)Frequency span
Sweep ranges
SG382 & SG384

Amplitude Modulation
Range
Resolution
Modulation source
Modulation distortion
BNC output
N-type output
Modulation bandwidth

0 to 100 % (decreases above +7 dBm)
0.1 %Internal or external

SG386<1 % (fC < 62.5 MHz, fM = 1 kHz)
<3 % (fC > 62.5 MHz, fM = 1 kHz)>100 kHzFrequency Modulation
Frequency deviation
Minimum
Maximum (SG382 & SG384)
fC ≤ 62.5 MHz
62.5 MHz < fC ≤ 126.5625 MHz
126.5625 MHz < fC ≤ 253.125 MHz
253.125 MHz < fC ≤ 506.25 MHz
506.25 MHz < fC ≤ 1.0125 GHz
1.0125 GHz < fC ≤ 2.025 GHz
2.025 GHz < fC ≤ 4.050 GHz (SG384)
4.050 GHz < fC ≤ 8.100 GHz (opt. 2)
Maximum (SG386)
fC ≤ 93.75 MHz

0.1 HzSmaller of fC or
64 MHz – fC
1 MHz
2 MHz
4 MHz
8 MHz
16 MHz32 MHz64 MHzSmaller of fC or
96 MHz – fC
1 MHz
2 MHz
4 MHz
8 MHz
16 MHz32 MHz64 MHz93.75 MHz < fC ≤ 189.84375 MHz
189.8437 MHz < fC ≤ 379.6875 MHz
379.6875 MHz < fC ≤ 759.375 MHz
759.375 MHz < fC ≤ 1.51875 GHz
1.51875 GHz < fC ≤ 3.0375 GHz
3.0375 GHz < fC ≤ 6.075 GHz
6.075 GHz < fC ≤ 8.100 GHz (opt. 2)
Deviation resolution
0.1 HzDeviation accuracy<0.1 %(fC ≤ 62.5 MHz (SG382 & SG384))(fC ≤ 93.75 MHz (SG386))<3 %(fC > 62.5 MHz (SG382 & SG384))(fC > 93.75 MHz (SG386))
Modulation source
Internal or external
Modulation distortion <–60 dB (fC = 100 MHz, fM = fD =1 kHz)

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Deviation resolution
Sweep source
Sweep distortion
Sweep offset
Sweep function

10 Hz to entire sweep range
DC to 64 MHz
59.375 MHz to 128.125 MHz
118.75 MHz to 256.25 MHz
237.5 MHz to 512.5 MHz
475 MHz to 1025 MHz
950 MHz to 2050 MHz
1900 MHz to 4100 MHz (SG384)
3800 MHz to 8200 MHz (Opt. 02)
DC to 96 MHz
89.0625 MHz to 192.188 MHz
178.125 MHz to 384.375 MHz
356.25 MHz to 768.75 MHz
712.5 MHz to 1537.5 MHz
1425 MHz to 3075 MHz
2850 MHz to 6150 MHz
5950 MHz to 8150 MHz (Opt. 02)
0.1 HzInternal or external<0.1 Hz + (deviation / 1,000)<1:1,000 of deviation
Triangle, ramp or sine up to 120 Hz

Phase Modulation
Deviation
Deviation resolution

0 to 360º
0.01º to 100 MHz, 0.1º to 1 GHz,
1º above 1 GHz
Deviation accuracy<0.1 %(fC ≤ 62.5 MHz (SG382 & SG384))(fC ≤ 93.75 MHz (SG386))<3 %(fC > 62.5 MHz (SG382 & SG384))(fC > 93.75 MHz (SG386))
Modulation source
Internal or external
Modulation distortion <–60 dB (fC = 100 MHz, fM =1 kHz,ΦD = 50º)
Modulation bandwidth 500 kHz(fC > 62.5 MHz (SG382 & SG384))(fC > 93.75 MHz (SG386))
100 kHz(fC > 62.5 MHz (SG382 & SG384))(fC > 93.75 MHz (SG386))
Pulse/Blank Modulation
Pulse mode
Blank mode

Logic “High” turns RF “on”
Logic “High” turns RF “off”

SG380 Series Specifications

On/Off ratio
BNC output
Type-N output
Pulse feed-throughTurn on/off delay
RF rise/fall time
Modulation source

70 dB
57 dB (fC ≤ 1 GHz)
40 dB (1 GHz ≤ fC < 4 GHz)
35 dB (fC ≥ 4 GHz)
10 % of carrier for 20 ns at turn on (typ.)
60 ns
20 ns
Internal or external pulse

DC Bias Source (comes with Opt. 02)
OutputVoltage range
Offset voltage
DC accuracy
DC resolution
Output resistance
Current limit

Rear-panel SMA±10 V<20 mV±0.2 %
5 mV
50 Ω
20 mA

External I/Q Modulation (Opt. 03)
GeneralCarrier frequency range 400 MHz to 2.025 GHz (SG382)
400 MHz to 4.05 GHz (SG384)
400 MHz to 6.075 GHz (SG386)
Modulated output
Front-panel N-type only
I/Q inputs
50 Ω, ±0.5 V
I or Q input offset<500 µV
I/Q full scale(I2 + Q2)1/2 = 0.5 V
Carrier suppression>40 dBc (>35 dBc above 4 GHz)
Modulation bandwidth 200 MHz (–3 dB)

Ethernet (LAN)GPIB
RS-232
Line power
Dimensions, weight
WeightWarranty

10/100 Base-T.TCP/IP & DHCP default
IEEE488.2
4800 to 115,200 baud, RTS/CTS flow
<90 W, 90 to 264 VAC, 47 to 63 Hz w/ PFC
8.5" × 3.5" × 13" (WHD)
10 lbs.
One year parts and labor on defects inmaterials and workmanship

Square Wave Clock Outputs (Opt. 01)
Differential clocks
Frequency range
Transition time (typ.)JitterfC > 62.5 MHz

Rear-panel SMAs drive 50 Ω loads
DC to 4.05 GHz<35 ps (20 % to 80 %)<300 fs rms (typ., 1 kHz to 5 MHz BW
at 1 GHz)fC ≤ 62.5 MHz<10–4 U.I. (1 kHz to 5 MHz or fC /2 BW)
Amplitude
0.4 Vpp to 1 Vpp
Offset±2 VDC
Ampl/offset resolution 5 mV
Ampl/offset accuracy ±5 %Output couplingDC, 50 Ω ±2 %Compliance
ECL, PECL, RSECL, CML, LVDS, NIM
Frequency Doubler Output (Opt. 02)
OutputFrequency range

Rear-panel SMA
4.05 GHz to 8.10 GHz (SG384)
6.075 GHz to 8.10 GHz (SG386)
RF amplitude–10 dBm to +13 dBm (4.05 GHz to 7 GHz)
–10 dBm to +7 dBm (7 GHz to 8.10 GHz)
+13 to +16.5 dBm (spec. not guaranteed)
Sub harmonic (fC/2)<–25 dBc (fC < 6.5 GHz)<–12 dBc (fC < 8.1 GHz)
Mixing products (3fC/2) <–20 dBc
Harmonics (n × fC)<–25 dBc
Spurious (8 GHz)<–55 dBc (>10 kHz offset)
Phase noise (8 GHz)
–98 dBc/Hz at 20 kHz offset (typ.)
Amplitude resolution 0.01 dBm
Amplitude accuracy±1 dB (4.05 GHz to 6.5 GHz)
±2 dB (6.5 GHz to 8.1 GHz)
Modulation modes
FM, ΦM, sweeps
Output couplingAC, 50 Ω
Reverse protection
30 VDC, +25 dBm RF

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phone: (408)744-9040
www.thinkSRS.com