VNA-dsp / Antenna Analyzer
This project is my attempt to build a portable standalone VNA (Vector Network Analyzer).
My main focus was to build an instrument that could be used at the antenna feed point
to measure impedances. Once the antenna impedance is known, the smith chart can be used to suggest
various matching networks. This instrument uses the VNA RF board by
Paul N2PK .
I received a great deal of information from
Greg W8WWV regarding some of the complex math
involved dealing with the analyzer computations and calibration. He kindly provided the sources
for his gnat and exeter windows programs which I used to develop the vna-dsp software. Greg also supplied
blank PCB boards for the VNA and the reflection bridge. I sourced most of the parts through
the Analog Devices sample program,
the National Semicondutor sample program,
and the Microchip sample program.
My thanks to the hams and companies that made this project possible.
The N2PK board is meant to be used with a
computer or laptop as the operator interface. This project uses a very powerful micro controller
(the dsPic30f4011) to tie together the 2x24 LCD display, 3 push buttons,
a home made rotary encoder for frequency selection, a battery voltage monitor,
a serial remote computer interface, a dual regulated 5V supply
(one for the rf board and one for the digital processor board) and the VNA board. The whole box
is powered by 8 AA Nimh cells.
This project turned out to be a quite an undertaking.
In the process I had to:
- design and layout PCB's in the eagle PCB program
- mechanically etch circuit boards on a milling machine.
- work with little tiny surface mount parts
- solder under a 15X microscope
- reverse engineer how a mouse works
- build a dsPIC in circuit programmer (including linux programming software)
- program the dsPIC in C using the Microchip MPLab development environment
- interface to an LCD display
- work with complex numbers to compute OSL calibration data and results data
for a return loss bridge (this all had to fit in a single chip micro controller)
Below are some pictures I took as the project progressed...
Power Supply Board (dual 5 volt regulators) Top and Bottom
dsPic 30F4011 CPU Board Top and Bottom (note surface mount resistors and bypass caps)
Front Panel LCD display and Buttons, Encoder (from Mouse Parts)
Power/RF Assembly and the dsPIC Assembly on each side of a sub-panel
All the pieces mated together showing the Return Loss Bridge PCB
User Interface Description
A lot of this project is mechanical packaging of various components. The Microchip MPLab integrated
development environment with the C30 compiler was used running under VMware/WindowsXP on an Ubuntu
linux computer. The MPLab project files and all the source code files are available later on this page.
The eagle PCB files are supplied below for the power supply and the
processor board. I do not have plans to market this project or any of its parts.
I am releasing this design and software for anyone to use for non commercial use.
I am available as a consultant for commercial applications of this or similar products.
My contact information is available on my home page.
- flash display on battery voltage < 8.75v (1.1v/cell)
- a standbye mode where the DDS chips are powered down, encoder led powered down,
and the status led is shut off.
- Evgeny, VE3SSR has done a nice graphical interface... see lecont.net
power supply schematic - vna-ps-sch.png(27.7K)
processor board schematic- vna-dsp-sch.png(67.5K)
power supply - eagle schematic - vna-powersupply.sch(156.4K)
power supply - eagle board - vna-powersupply.brd(8.8K)
processor - eagle schematic - vna-dspic.sch(131.0K)
processor - eagle board - vna-dspic.brd(19.8K)
VNA-dsp project source code - vna-dsp-19may2006.zip(111K)
VNA-dsp project source code - vna-dsp-30nov2006.zip(114K)
VNA-dsp project source code - vna-dsp-22dec2007.zip(130K) interim release with SWR calc fix
VNA-dsp project source code - vna-dsp-14jan2008.zip(170K) supports bootloader or standalone operation
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