Stanford Research Systems SG386 datasheet

RF Signal Generators

SG380 Series — DC to 2 GHz, 4 GHz and 6 GHz analog 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 ... $4,600 (U.S. list)

· SG386 ... $5,900 (U.S. list)

SG380 Series RF Signal Generators

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) are
available, and an external I/Q modulation input (Opt. 03) is
also 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 and
amplitudes 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.

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SG380 Series RF Signal Generators

Modulation

The SG380 Signal Generators offer a wide variety of
modulation 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.

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 more
than an octave.

OCXO or Rubidium Timebase

The SG380 Series come with a oven-controlled crystal
oscillator (OCXO) timebase. The timebase uses a third­overtone stress-compensated 10 MHz resonator in a
thermostatically 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 be
supplied 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

SG380 Series Phase Noise vs. Offset Frequency

-40

-50

-60

-70

-80

-90

-100

-110

Phase Noise (dBc/Hz)

-120

-130

-140

-150

10 100 1,000 10,000 100,000 1,000,00 0 10,000,0 00

100 MHz

10 MHz

Frequency Offset (Hz)

4 GHz

1 GHz

The SG380 Series always synthesizes a frequency in
the top octave and digitally divides to generate outputs
at lower frequencies. Doing so creates phase noise
characteristics which scale with output frequency by
6

dB/octave or 20 dB/decade.

The low phase noise at small offsets (for
example, –80

dBc/Hz at 10 Hz offset from 1 GHz)
is attributable to the low phase noise OCXO timebase
reference oscillator. An important figure of merit for
communications applications is the phase noise at
20

kHz offset, which is about –116 dBc/Hz at 1 GHz.

Differential Clock Outputs

Option 01 provides differential clock outputs in
addition 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 with
standard 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.

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Amplitude Modulation (100 %)

The frequency range of the SG380 Series extends from
DC 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.

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

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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 the
clock 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 to
modulate carriers from 400 MHz to the upper frequency limit
of your instrument. This option also allows the I/Q modulator
to be driven by an internal noise generator with adjustable
bandwidth. Rear-panel outputs allow the noise source to be
viewed or used for other purposes.

I/Q Modulation of 1 GHz Carrier by

Internal Noise Generator

Option 03 allows I/Q modulation of carriers
from 400 MHz to the upper frequency limit of your
instrument. 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 are
on 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.
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 and
Ethernet 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) to
synthesize 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 is
sourced by a voltage controlled crystal oscillator that is phase
locked to a dithered direct digital synthesizer, is adjusted so
that 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 of
fractional-N synthesis or the cost of a YIG oscillator.

The

Unmodulated Spectrum of a 1 GHz Output

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

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Spectrum of Frequency Modulated 50 MHz Carrier

Outputs below 62.5 MHz are generated by direct­digital synthesis with a sample frequency of 1 GHz.
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.

In

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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 a
single dot in the I/Q plane. When the carrier frequency
is offset, the single dot moves in a circle about the
center 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.

Ordering Information

SG382 2 GHz signal generator $3,900
SG384 4 GHz signal generator $4,600
SG386 6 GHz signal generator $5,900
Option 01 Rear-panel clock outputs $750
Option 02 8 GHz doubler & DC bias $750
(SG384 and SG386 only)
Option 03 External I/Q modulation $750
Option 04 Rubidium timebase $1500
RM2U-S Single rack mount kit $100
RM2U-D Dual rack mount kit $100

SG384 rear panel

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SG384 front panel

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SG380 Series Specifications

SG380 Series Specifications

Frequency Setting

Frequency ranges DC to 62.5 MHz
SG382 950 kHz to 2.025 GHz (N-type output)
SG384 950 kHz to 4.05 GHz (N-type output)

4.05 GHz to 8.1 GHz (w/ Opt. 02)
SG386 950 kHz to 6.075 GHz (N-type output)

6.075 GHz to 8.1 GHz (w/ Opt. 02)
Frequency resolution 1 µHz at any frequency
Switching speed <8 ms (to within 1 ppm)
Frequency error <(10
Frequency stability 1 × 10

Front-Panel BNC Output

Frequency range DC to 62.5 MHz
Amplitude 1.00 Vrms to 0.001 Vrms
Offset ±1.5 VDC
Offset resolution 5 mV
Max. excursion 1.817 V (amplitude + offset)
Amplitude resolution <1 %
Amplitude accuracy ±5 %
Harmonics <–40 dBc
Spurious <–75 dBc
Output coupling DC, 50 Ω ±2 %
User load 50 Ω
Reverse protection ±5 VDC

Front-Panel N-Type Output

–18

+

–11

(1 s Allan variance)

(BNC output, all models)

timebase error) × f

C

20 kHz offset –116 dBc/Hz (SG382 & SG384)
–114 dBc/Hz (SG386)
1 MHz offset –130 dBc/Hz (SG382 & SG384)
–124 dBc/Hz (SG386)
Residual FM (typ.) 1 Hz rms (300 Hz to 3 kHz BW)
Residual AM (typ.) 0.006 % rms (300 Hz to 3 kHz BW)

* Spurs, phase noise and residual FM scale by 6 dB/octave to other
carrier frequencies

Phase Setting on Front-Panel Outputs

Max. phase step ±360º
Phase resolution 0.01º (DC to 100 MHz)

0.1º (100 MHz to 1 GHz)

1.0º (1 GHz to 8.1 GHz)

Standard OCXO Timebase

Oscillator type Oven controlled, 3rd OT, SC-cut crystal
Stability (0 to 45 ºC) <±0.002 ppm
Aging <±0.05 ppm/year

Rubidium Timebase (Opt. 04)

Oscillator type Oven controlled, 3rd OT, SC-cut crystal
Physics package Rubidium vapor frequency discriminator
Stability (0 to 45 ºC) <±0.0001 ppm
Aging <±0.001 ppm/year

Timebase Input

Frequency range
SG382 950 kHz to 2.025 GHz
SG384 950 kHz to 4.050 GHz
SG386 950 kHz to 6.075 GHz
Power output
SG382 +16.5 dBm to –110 dBm
SG384 +16.5 dBm to –110 dBm (<3 GHz)
SG386 +16.5 dBm to –110 dBm (<4 GHz)
Voltage output
SG382 1.5 Vrms to 0.7 µVrms
SG384 1.5 Vrms to 0.7 µVrms (<3 GHz)
SG386 1.5 Vrms to 0.7 µVrms (<4 GHz)
Power resolution 0.01 dBm
Power accuracy ±1 dB
Output coupling AC, 50 Ω
User load 50 Ω
VSWR <1.6
Reverse protection 30 VDC, +25 dBm RF

Spectral Purity of the RF Output Referenced to 1 GHz*

Sub harmonics None
Harmonics <–25 dBc (<+7 dBm, N-type output)
Spurious
<10 kHz offset <–65 dBc
>10 kHz offset <–75 dBc
Phase noise (typ.)
10 Hz offset –80 dBc/Hz
1 kHz offset –102 dBc/Hz

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

Timebase Output

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

Internal Modulation Source

Waveforms Sine, ramp, saw, square, pulse, noise
Sine THD –80 dBc (typ. at 20 kHz)
Ramp linearity <0.05 % (1 kHz)
Rate 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

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SG380 Series Specifications

Modulation Waveform Output

Output impedance 50 Ω (for reverse termination)
User load Unterminated 50 Ω coax
AM, FM, ΦM ±1 V for ± full deviation
Pulse/Blank “Low” = 0 V, “High” = 3.3 VDC

External Modulation Input

Modes AM, FM, ΦM, Pulse, Blank
Unmodulated level 0 V input for unmodulated carrier
AM, FM, ΦM ±1 V input for ± full deviation
Modulation bandwidth >100 kHz
Modulation distortion <–60 dB
Input impedance 100 kΩ
Input offset <500 µV
Pulse/Blank threshold +1 VDC

Amplitude Modulation

Range 0 to 100 % (decreases above +7 dBm)
Resolution 0.1 %
Modulation source Internal or external
Modulation distortion
BNC output <1 % (fC < 62.5 MHz, fM = 1 kHz)
N-type output <3 % (fC > 62.5 MHz, fM = 1 kHz)
Modulation bandwidth >100 kHz

Frequency Modulation

Frequency deviation
Minimum 0.1 Hz
Maximum (SG382 & SG384)
fC ≤
64 MHz – f

62.5 MHz < fC ≤

126.5625 MHz < fC ≤

253.125 MHz < fC ≤

506.25 MHz < fC ≤

1.0125 GHz < fC ≤

2.025 GHz < fC ≤

4.050 GHz < fC ≤
Maximum (SG386)
fC ≤
96 MHz – f

93.75 MHz < fC ≤

189.8437 MHz < fC ≤

379.6875 MHz < fC ≤

759.375 MHz < fC ≤

1.51875 GHz < fC ≤

3.0375 GHz < fC ≤

6.075 GHz < fC ≤
Deviation resolution 0.1 Hz
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 = fD =1 kHz)

62.5 MHz Smaller of fC or

C

126.5625 MHz 1 MHz

253.125 MHz 2 MHz

506.25 MHz 4 MHz

1.0125 GHz 8 MHz

2.025 GHz 16 MHz

4.050 GHz (SG384) 32 MHz

8.100 GHz (opt. 2) 64 MHz

93.75 MHz Smaller of fC or

C

189.84375 MHz 1 MHz

379.6875 MHz 2 MHz

759.375 MHz 4 MHz

1.51875 GHz 8 MHz

3.0375 GHz 16 MHz

6.075 GHz 32 MHz

8.100 GHz (opt. 2) 64 MHz

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))

Frequency Sweeps (Phase Continuous)

Frequency span 10 Hz to entire sweep range
Sweep ranges
SG382 & SG384 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)
SG386 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)
Deviation resolution 0.1 Hz
Sweep source Internal or external
Sweep distortion <0.1 Hz + (deviation / 1,000)
Sweep offset <1:1,000 of deviation
Sweep function Triangle, ramp or sine up to 120 Hz

Phase Modulation

Deviation 0 to 360º
Deviation resolution 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 Logic “High” turns RF “on”
Blank mode Logic “High” turns RF “off”

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SG380 Series Specifications

On/Off ratio
BNC output 70 dB
Type-N output 57 dB (fC ≤ 1
40 dB (1 GHz ≤ fC < 4
35 dB (fC ≥ 4
Pulse feed-through 10 % of carrier for 20 ns at turn on (typ.)
Turn on/off delay 60 ns
RF rise/fall time 20 ns
Modulation source Internal or external pulse

External I/Q Modulation (Opt. 03)

Carrier 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)
Carrier suppression >40 dBc (>35 dBc above 4 GHz)
Modulation bandwidth 200 MHz (–3 dB)

Square Wave Clock Outputs (Opt. 01)

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

1/2

= 0.5 V

GHz)

GHz)

GHz)

DC Bias Source (comes with Opt. 02)

Output Rear-panel SMA
Voltage range ±10 V
Offset voltage <20 mV
DC accuracy ±0.2 %
DC resolution 5 mV
Output resistance 50 Ω
Current limit 20 mA

General

Ethernet (LAN) 10/100 Base-T.TCP/IP & DHCP default
GPIB IEEE488.2
RS-232 4800 to 115,200 baud, RTS/CTS flow
Line power <90 W, 90 to 264 VAC, 47 to 63 Hz w/ PFC
Dimensions, weight 8.5" × 3.5" × 13" (WHD)
Weight 10 lbs.
Warranty One year parts and labor on defects in
materials and workmanship

Frequency Doubler Output (Opt. 02)

Output Rear-panel SMA
Frequency range 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 coupling AC, 50 Ω
Reverse protection 30 VDC, +25 dBm RF

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