This site is
presently dedicated to the posting of design information useful for
amateur/hobbyist construction of electronic test equipment.
FILES
Following is a
list of files containing schematics, board layouts or other useful information.
Schematics and layouts should be considered works in progress.
Items
related to Scotty’s Modular Spectrum Analyzer (MSA)
MSA
Overview—An overview of the MSA capabilities and
construction, to provide orientation to potential builders.
Documentation
for MSA Operation
Walk-Throughs
The
following documents walk the user through the actual use of the MSA, using
simulated data. You do not need the MSA hardware to use these. They provide an
overview of the MSA capabilities and an introduction to the use of the
software.
Walk-Through:
VNA Transmission Mode
Walk-Through:
VNA Reflection Mode
Bench-top Operating Guides
Spectrum Analyzer
Operating Guide—MSA operating guide for Spectrum Analyzer Modes.
VNA
Operating Guide—MSA operating guide for VNA modes. (Also includes SNA
mode.)
Other
Documentation
Operation
of the MSA as a VNA—Overview and supporting documents regarding the MSA as
a Vector Network Analyzer, including theory, procedures, fixtures, and test results.
RLC Analysis—Analysis
of devices modeled as series or parallel combinations of a resistor, inductor
and capacitor. Useful for measuring component values and parasitics.
Measuring
PCB Dielectric Constant—Procedure and test results for measuring the
dielectric constant of printed circuit boards from to 3 GHz, using the 1G, 2G
and 3G bands of the MSA.
Measuring
PCB Dielectric Constant Spreadsheet—Spreadsheet to help when matching
resonant modes to measured peaks.
Fringe
Effects in PCB—Experiments evaluating Fringe Effects that can affect the
measurement of dielectric constant.
Measuring L and Q of High-Q Coils—Techniques
for measuring inductance value and Q, especially for coils with high Q.
Front-End
Compensation—New feature (as of 6/10) to adjust spectrum analyzer displays
for the frequency characteristics of probes, amplifiers, attenuators or other
front-end devices.
Version
116 ReadMe—Info on changes between MSA software versions 115 and 116
(scheduled for release Jan., 2011).
Filter
Matching—Determining optimum filter matching
components using the Auto Match feature of the Two-Port module in MSA software
version 116.
Effects of
Interference—Analyzes the errors caused by various
types of interference, such as the imperfect directivity of a bridge or leakage
in switching mechanisms. Specifically analyzes the “VHF”
Transmission/Reflection switch for the MSA.
PortView—A
program for viewing and manipulating S-Parameter data, including a circuit
layout module and a graphing module.
OSL
Calibration—Collection of documents explaining the equations used for OSL
calibration, the MSA method for describing calibration standards, information
on construction of standards, and some test results. Specific data is provided
for standards constructed with Amphenol RFX
connectors and certain Molex connectors.
Marker
Interpolation—Discussion of some issues arising when markers are placed
between data points. Also illustrates some related features of the MSA.
Construction
Photographs And Diagrams
Enclosure—Brass
box to hold everything
High Frequency
Grid Back—The high frequency grid holds the microwave and signal generator components—DDSs,
PLOs, Mixers and a few other modules. It is made of
0.016” brass strips reinforced on the back with small brass
Progress 11/8/08—PDF file containing
photos with most of the microwave modules installed.
Progress
12/3/08—PDF file with photos of the almost-finished innards. All modules are
in place on brass grids, and most have their brass lids tacked in place. As is,
this is functional enough for testing. Note: PDM inputs are reversed in this
photo.
Module
Layout and Coax Wiring—Modules viewed from bottom with coax connections.
Express PCB format.
MSA
Logic Wiring—Modules viewed from bottom with logic wiring. ExpressPCB format
MSA
Documentation Relating to Hardware
RBW Filter Switch
Board—Description and test results of switching board for selection of one
of four RBW filters.
Video Filter Switch
Board—Schematics and PCB layout (ExpressPCB
formats) for automated video filter switching, and necessary corrections to the
original PCB.
Calibration
Accessories—Documentation, schematics and PCB files for several accessory
boards that are useful for calibration of the MSA. Includes fixed attenuators,
switched attenuators, calibration signal source and Leveler, most of which are
described in more detail elsewhere on this site.
Control Board
Tester—Zip file with program to set, clear or toggle the latches on the MSA
control board via the parallel port. The latch bits can then be tested on a
voltmeter or oscilloscope.
Calibration
Source Schematic and PCB layout (ExpressPCB)
Calibration Source Test Results (pdf)—A simple device to generate a square or sine wave of
predictable strength (near 0 dbm, accurate to +/-0.1
db) for spectrum analyzer calibration. The square wave is clean enough
that a large number of odd harmonics also have very predictable values, which
may be handy for other purposes. Built at several frequencies but output of 2
MHz is ideal for MSA calibration.
Peak Detector—ExpressPCB layout of a high frequency peak detector;
component values are shown on the layout. This might be useful for verifying
the PLO output levels for anyone without a power meter.
High Frequency
Log Detector—ExpressPCB layout of a high
frequency log detector; component values are shown on the layout. Has wider
range than the Peak Detector.
Cavity Filter
Tuning with the Peak or Log Detector—A procedure
for tuning the cavity filter using the Peak Detector or Log Detector and a
partially completed MSA.
Switchable Attenuator Schematic (ExpressSchem)
Switchable Attenuator PCB (ExpressPCB)
Switchable
Attenuator Photo (jpeg)—Switchable
attenuator with individually selectable attenuations of 2.5-5-10-20-20db which
can be combined to cover 0-57.5 db in 2.5 db steps. This is intended to
be used at 1 MHz for calibration of the MSA. At that frequency the attenuation
should be accurate within 0.1 db at all settings. It is functional with
somewhat less precision to at least 500 MHz.
Active Bridge
for MSA—Documentation of an active reflection bridge that can also be used
as a buffer amplifier in MSA test setups.
Buffer
Amplifier—Buffer amplifier made by modifying the
ExpressPCB
schematic and layout for
AGC Loop—A high dynamic range method for amplification and magnitude
measurement of the final IF in Scotty’s Spectrum Analyzer. This is an alternative to the log detector.
Modifications
to the original Cash Olsen AGC Loop boards to avoid oscillations (jpeg file)
SLIM version of
AGC Loop—New layout and test results for modules
in the SLIM format.
Updated
Schematic and Layout for ExpandedLogDetector
Even
More Updated Schematic and Layout —Similar concept
to the AGC loop, with slightly less potential range. A VGA is combined with a
log detector (with a noise filter between them) to expand the effective range
of the log detector. Combined with a preamp placed before the RBW filters
(which preamp replaces the original IF amp), the range of the spectrum analyzer
can be increased to cover -115 dbm to 0 dbm.
IF2
Amp—Amplifier with 28 dB gain, based on OPA847, to replace the standard MSA
IF Amp, which provides 40 dB gain. This amplifier should be used when the
Expanded Log Detector is used.
Digital Phase Detector Test—Schematic
and test results of digital phase detector. Test is at 20 MHz, but detector is functional
to 100 MHz. Different logic family but similar to Scotty’s design.
High Voltage Supply PCB—Schematic and
PCB layout (ExpressPCB format) for a nominally +23V
supply to power VCO control voltages, from a +10V source. It is a
switching style design, but creates very little oscillator ripple at its input
and output, and little radiation, though it should be encased with a fence and
top. Output voltage can be adjusted.
1G/2G Diplexer—Documentation,
schematic
and PCB
layout (ExpressPCB) for diplexer on Mixer 1
output to simplify switching between 1G and 2G modes. 1G is the normal 0-1 MHz mode.
2G mode is 1-2 GHz. 3G mode is 2-3 GHz and operates with the same hardware
setup as 1G mode.
Cavity
Filters (Box) –Construction method for cylindrical and box shaped cavity
filters.
Stepped Phase
Shifter—MS Word document describing a simple device for generating a test
signal whose phase can be shifted manually or by digital command. Can be used to calibrate a VNA or for other
purposes.
SPI
Transmitter PCB
—PNG and ExpressPCB files for a simple device
which can transmit data to SPI compatible devices. Just push a series of 0’s and 1’s, and the
necessary clock and data signals are generated.
Select signal can select one of three target devices. Great for setting up digital attenuators,
potentiometers, DDS’s, PLL’s, etc. You don’t want to spend your whole life
transmitting manually in binary, but it is a great way to test devices without
messing with a computer hookup.
Attenuators—Schematic (ExpressSchem), PCB layout (ExpressPCB),and PDF document describing homemade attenuators, with test results to 1.5GHz. These attenuators work extremely well—very accurate and very flat.
Fixtures/Reflection
Bridges/Impedance Measurement
Measuring Resistance of Calibration Loads—Simple techniques to precisely determine the DC resistance of
Loads used for OSL calibration. It’s easy with a 4 ½ digit DMM, but this
explains how to get good results with the more common and much cheaper 3 ½ digit
meters.
S21/Shunt
Impedance Measurement—Measurement of impedance with the MSA using a normal
transmission measurement (no OSL calibration) in a shunt test fixture.
Describes the technique and test results.
Impedance
Measurement with the Series Fixture and OSL Calibration—Description of
simple test fixture for measuring impedance (and S11) of certain
devices without use of a reflection bridge. The devices must be “floating”
two-terminal devices (i.e. one terminal can’t be permanently grounded) such as
resistors, capacitors, inductors and crystals. Test results show very good
measurement from 1 ohm to 100K ohms, depending on frequency. In many cases the
measurements are accurate to 500 MHz.
Shunt Fixture
for Low Impedance Measurements—Simple fixture for impedance measurements as
low as 0.01 ohms. Can be used with the MSA, or independently
with manual calculations.
Fixture
for Dip Meter—Same shunt fixture, used with a coil
for coupling to resonant circuits to measure resonant frequency. Can also be used without a VNA.
Three-Bead-Balun
Bridge—A reflection or return loss bridge which
may be used in conjunction with Scotty’s Spectrum Analyzer configured with the
VNA feature, or may be used manually as a freestanding bridge. Performance is
good from 250 KHz to beyond 1 GHz. Note that for a second build of this bridge,
I got somewhat lesser, but acceptable results. I prefer the “Bridge with Balun
Plus Beads” described below.
Bridge
with Balun Plus Beads—A reflection or return loss
bridge that is ideal for use with Scotty’s Spectrum Analyzer configured with
the VNA feature. Good from 50 KHz to beyond 1 GHz. Can also be used for manual
measurements, but is not as good for that purpose as the ones below.
Bridge with Dual TC1-1-13M
Performance
Graph—A reflection or return loss bridge useable with
Scotty’s Spectrum Analyzer. Simpler than the ones above, but good only down to
about 250 KHz, and not as good for manual measurements.
Manual
Return Loss Measurements—Describes two bridges for manual measurement of
return loss. The passive bridge (
Using Manual
Measurements to Estimate Impedance-PDF describing how to use multiple
measurements of scalar return loss to determine impedance.
Spreadsheet
for Impedance Calculation—Excel spreadsheet to do the graphs and
calculations described above.
Bridge PCBs—PCB layout (ExpressPCB) for the above bridges.
Low Frequency Bridge—PNG--Image of
schematic for a reflection bridge using one IC.
Simple Scalar Network Analyzer—Device
to measure return loss/VSWR and transmission properties using a signal
generator or sweep generator.
About $30 in parts. Includes
schematic, method of use, and some sample scans of filters and cables.
Reflection Bridge PCB Layout—PNG and ExpressPCB files for a two op amp reflection bridge.
Similar to
Circulator PCB
Layout— PNG and ExpressPCB files for a circulator
based on the Charles Wenzel article.
Visible
Square Wave Reflections—Technique for viewing coax cable reflections using
a square wave source and an oscilloscope. Can be used
to find defects in the cable or its termination.
Other
Bypass Tests—PDF file
describing some tests of capacitor bypassing.
Quadrature
Sampling-PDF describing a method of using quadrature
digital sampling for phase and magnitude measurement of a low-IF signal for a
VNA
ADE-1 Mixer as Phase Detector –Some experiments using the ADE-1 mixer as a phase detector, and potentially as a phase and magnitude detector.
Improve AD8302 with
Phase Shifting—PDF file describing a method to use phase shifting circuitry
to improve the accuracy of the AD8302 phase/magnitude detector, as well as to
determine the sign of the phase, which the AD8302 always outputs as positive.
Expand
AD8302 Range with AD8330 –MS Word file describing a method to combine a VGA
with the AD8302 to expand its dynamic range.
The AD8302 nominally has a 60 db range, but is quite inaccurate at the
edges.
AD995x
Carrier Board—MS Word document describing a small carrier board for the
AD995x DDS family, designed to confine intricate soldering to a single small
board which can then be soldered onto a motherboard.
Test Results of Fancier Bridge—MS Word document showing results of experiments with reflection/transmission bridge using an AD8309 log amp to provide direct output measurement in db.
DDS Clock Calculator—Excel
spreadsheet to calculate whether an integer multiple of the output of a DDS is
also an integer multiple of the clock frequency, which aggravates spurs. Assumes that the DDS has an output range
centered at a user specified frequency, with a small excursion around that
frequency, as when the DDS is used in a hybrid synthesizer to control a PLL.
Conversion of Phase Noise to Jitter—Excel
spreadsheet to calculate the RMS jitter corresponding to a user-entered phase
noise profile. Can also be used
in reverse to estimate how much phase noise corresponds to a specified amount
of jitter.
VHF Noise Generator—Schematic
for a noise generator for 100kHz to 30MHz and above. Useful as a signal source to generate a DUT
frequency response on a spectrum analyzer.
Analyzer100
The Analyzer100,
formerly the VectorAnalyzer60,
currently in the prototype stage, is intended to be a stand-alone vector
network analyzer for the 1kHz-100MHz range. “Stand-Alone” means it requires no computer
control. It does depend on an external
signal source for the test signal. In this
prototype, the phase or magnitude is displayed on the panel meters. Ultimately, the displays will be
microprocessor controlled. To see a further description, and the results of
some tests, see Analyzer100.
LINKS
Following is a
list of useful links:
Scotty’s
Spectrum Analyzer—web site explaining the original
SSA and the Modularized Spectrum Analyzer.
Cash Olsen's Kits --kits for building
Scotty’s Spectrum Analyzer, and related kits
SSA Builder’s Group
--Builder’s group for Scotty’s Spectrum Analyzer
swetterlin at comcast dot
net –My email address. Comments are
welcome.