Signal Hound VSG60A Product Manual

VSG60A Vector Signal Generator

Product Manual

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Signal Hound VSG60A Product Manual

Published 8/23/2019

© 2019, Signal Hound, Inc.

1502 SE Commerce Ave, Suite 101

Battle Ground, WA USA

Phone [phone]

This information is being released into the public domain in accordance with the Export Administration

Regulations 15 CFR 734

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Contents

1 Introduction .......................................................................................................................................................... 1

2 Understanding the Hardware ............................................................................................................................. 2

3 Capabilities ........................................................................................................................................................... 6

4 Calibration ............................................................................................................................................................ 6

5 Adjustments ......................................................................................................................................................... 6

6 VSG60A Preliminary Specifications .................................................................................................................. 7

7 Typical Performance ......................................................................................................................................... 10

Introduction | Preparing for first use

1

1 Introduction

The Signal Hound VSG60A Vector Signal Generator offers mid-range performance and agility at an
affordable price. Continuously streaming up to 40 MHz of bandwidth at up to 51.2 MSPS from a PC
or laptop virtually eliminates I/Q pattern buffer size restrictions.

The VSG60A hardware features an agile low phase noise LO synthesizer, digital baseband
oversampling with reconstruction filter, harmonic filters across the full frequency range, and a trigger
output, timed to match the RF output, for integrating the VSG60A in to test systems.

I/Q phase, amplitude, and offset are corrected across RF frequency, baseband frequency, and
temperature in our environmental chamber, and stored on the VSG60A. The software applies these
corrections in real-time.

Commands to change frequency and amplitude are embedded in the same data stream from the PC
as the I/Q data, giving the user precise timing across frequency and amplitude changes. The agile
LO can change frequency and settle in 200 µs and offers outstanding phase noise.

PREPARING FOR FIRST USE

• Install the VSG60A software, either from signalhound.com or the included CD.

• Plug in the VSG60A using the included USB Y cable by first connecting the USB 3.0 type A

connector to a USB superspeed port on your PC or laptop. Then plug in the thinner USB 2
type A connector (for extra power). Finally, plug in the micro-B connector to the VSG60A until
it is fully seated and tighten the thumb screws. Do not overtighten. You should see a solid
green LED on the VSG60A.

o Note: The VSG60A is intended for use only with the included USB cable. Longer

cables may result in an intermittent connection, especially around electromagnetic
interference.

• Launch the software.

Understanding the Hardware | Preparing for first use

2

2 Understanding the Hardware

At the heart of the VSG60A is pair of quadrature modulators, one for below 2 GHz, and one for above

2 GHz (and a small segment around 800 MHz), driven by a dual channel DAC. The DAC clocks in
I/Q samples at 66-102 .4 MSPS. The data rate from the PC to the FPGA is 22-51.2 MSPS I/Q, so
inside the FPGA we digitally up-sample by a factor of 2 or 3. This allows the use of a single optimized
reconstruction filter for typically better than 60 dB rejection of any aliased baseband signals, and
allows the PC to efficiently up-sample the user-selected baseband clock rate by a simple power of
two.

The baseband clock is generated from a 2.4 to 2.8 GHz VCO and divided down to 66-102.4 MHz.
Standard telecom symbol rates can be produced with 0 ppm additive error, and any symbol rate can
be produced with less than 1 ppm error.

The local oscillator (LO) generates a low phase noise CW signal (typically -125 dBc/Hz at a 10 kHz
offset from 1 GHz) for the I/Q modulators. Below 2 GHz, the LO runs at twice the RF frequency and
is digitally divided into quadrature. Above 2 GHz, a polyphase filter generates the quadrature LO for
the mixers. The LO switches frequencies in 200 microseconds for frequency-hopping applications.
The LO has 1/6 Hz resolution when digital tuning is disabled, and better than 1 µHz when digital tuning
is enabled. See the section on digital tuning for more information.

Both the baseband clock and LO are synthesized from a low phase noise 80 MHz clock, tied to either
the internal 10 MHz voltage-controlled, temperature-compensated crystal oscillator (VCTCXO), or the
user’s external 10 MHz input.

From the modulators, up to 20 dB of gain or 50 dB of attenuation is applied, in 2 dB steps. The
VSG60A software typically automatically selects the best setting based on output amplitude, but

Understanding the Hardware | External 10 MHz input

3

manual control is available as well. Fine amplitude control is handled digitally, providing 0.01 dB
resolution on the output amplitude.

Finally, a bank of harmonic filters reduces the amplitude of harmonics generated from the modulators
and amplifiers, typically below -40 dBc.

The FPGA in the VSG60A can quickly switch between streaming I/Q and changing LO frequency or
attenuator settings at precise intervals (200 µs and 10 µs, respectively), allowing the user to build
signals that hop across the entire frequency range of the device. This makes the VSG60A a good
choice for generating frequency hopping signals or signals that must cover a wide amplitude range.

EXTERNAL 10 MHZ INPUT

A low-jitter comparator provides low additive phase noise for an external 10 MHz reference input of 0
dBm to +13 dBm. When external reference is enabled, the internal 10 MHz VCTCXO is disabled and
the external reference disciplines the 80 MHz VCXO directly. Inputs as low as -15 dBm will work, but
phase noise degrades at lower amplitudes. A square wave provides the highest slew rate and
therefore the best phase noise.

TRIGGER OUTPUT

The trigger output is a series-terminated 3.3V logic signal, meant to typically drive a high impedance
load. The trigger output is synchronized with the RF output. Up to 1000 triggers per second can be
output, with a user-selectable pulse width. This enables the VSG60A to be connected to other
equipment in an automated testing environment.

LOW SPUR MODE (DIGITAL TUNING)

The LO uses a fractional-N PLL. This can lead to integer boundary spurs, as well as other spurious.

To mitigate these spurs, a low spur
mode has been added, which is on
by default. When low spur mode is
enabled, the fractional-N PLL uses a
very low denominator to keep the
spurs at least 2 MHz away from the
carrier and typically below -50 dBc
above 3.7 GHz, and below -55 dBc
below 3.7 GHz. This gives a coarse
LO frequency, which is then digitally
tuned to the exact requested
frequency. The advantages of digital
tuning are very low-level, predictable