vector network analyzer antenna design
I am doing antenna design w/o vna. I just simulate my designs and fab them then hope for the best.
And I haven't seen even a glimmer of hope. I could send/receive data but it is not correct. We use a devkit and when the code is tested there, it sends/receives perfectly.
In our testing, my board design is the TX and the devkit is the RX. The devkit is interfaced via USB to the computer and we could see the PANID, payload etc...
Everything is messed up. It changes PANid every time it sends, the payload is messed up. It is just wrong.
My guess is:
1. mismatch of antenna frequency
2. low gain/directivity of my antenna
3. SNR
4. impedance mismatch
All could be found out IF i only have a VNA on hand. :(
Any suggestions?
BTW my antenna is a dipole.
If you don’t have a VNA is good to have at least a Spectrum Analyzer. Using the SA can measure first the conducted power at antenna connector, and after that measure the radiated power at specific distance (usually at 3m).
Knowing the conducted power, the radiated power, distance and frequency, can find the gain of the antenna, and also the antenna pattern if you rotate the antenna.
Sadly, this is the company's first try at wireless comms. And no equipment is available for me.
Even the simtool I am using is the one I used at undergrad (HFSS) . The license is mine!
*sigh
Some years ago, engineers generally used to design antennas and other RF circuits without EM simulation tools. Many still don't need it.
I guess your targetting to 2.4GHz. For short distance, you can expect reliable communication with any short piece of wire,
most likely even to a board equipped with a termination resistor in the vincinity, because I don't expect perfect shielding of your design.
If it doesn't work at all, you should expect a different problem. But I guess, there are also means as RSSI monitoring outputs with your chip set.
A small handheld spectrum analyzer as TTI PSA2701 or some used benchtop instrument should hopefully fit your budget.
I really doubt if any equipment could be purchased now. Budget is very tight because of the lingering effects of the recession and all...
I was thinking of maybe fabricating everything in one board, all but the antenna.
Then use an sma connector to connect/disconnect the antenna, just to make trial and error easier.
But i would have to make a new design, a monopole or maybe PIFA...to make the connection to sma...
Also, if i do that, I still don't have any indication whether i need to clip the antenna leg or add on it once i am doing my testing against the devkit
i am really lost
I guess, even a schottky diode with wires cut to form a lamda/2 dipole and a multimeter connected to it by series resistors and twisted wires would be sufficient as a field strength indicator. There are also magnetron leak indicators available in DIY stores for a few 10 S maximum.
i will look for available magnetron leak indicator in our area...and will try this schottky idea of yours...
though i don't know the theory behind it, will research on this...thanks
but how about the frequency match? how can i be sure about 2.4GHz?
Search the net for WLAN/WIFI band monitor software, which transforms any standard WLAN/WIFI wireless card into a 2.4GHz band spectrum analyzer monitor.
Some of them don't need to decode the data, just show the RF level, based on the internal RSSI.
Anyway, gives you better (and more consistent) measurement results than a diode detector.
will do! thanks...