Using USB-5680 to measure the recived signal strength of a device that use frequency hopping

[liorRafa]

Hello

My companydevelops a Mesh type of WSN (Wireless Sensor Network) for distributedmonitoring and data collection. Our units transmit the signal in 26dBm and usea frequency hopping method that is bound to 916-950MHz.

We want to makesome tests, to determine the received signal strength in relation to distance. Thereare X transmission in a period of two seconds. Each transmission is sent with adifferent frequency (between 916-950MHz). Recently we have purchased theUSB-5680 RF power meter. And we want to use it to make these tests using theSFP (soft front panel).

The frequencyrange of the USB-5680 is 0.05GHz to 6GHz, so our system frequency is in thatrang. However, In the SFP I need to choose the frequency I am measuring, the problem isthat our units use frequency hopping method, so each transmission is indifferent frequency.

 Is there a way to measure the received signalstrength each moment, so each transmission in our system frequency range willbe measured with no respect to its specific frequency?

Thanks a lot

Lior

[nayer]

Hello Loir,

The NI USB-5680 is a 6 GHz true RMS power meter, which means that it returns a single RMS power measurement that represents the entire power within its 50 MHz to 6 GHz bandwidth, generally used for wired measurements. I believe you are attaching antenna to the power meter which is not a good idea unless you are using a highly tuned antenna which flat gain in freq. range of 916-950MHz. There is a channel bandwidth specification on the product page that indicates a channel bandwidth of 100 Hz. The channel bandwidth defines the size of the frequency bins used to make the RMS measurement. This channel bandwidth corresponds to a noise floor in a power spectrum and the time duration required to make the measurement. The center frequency is used to adjust the RF power meter calibration coefficients to flatten its internal passband around the center frequency of interest. For any center frequency that is set, the value returned is the RMS power across the entire 50 MHz to 6 GHz bandwidth. For accurate measurements what you would need is a VSA where you can tune the front end at the center frequency 933MHz, with the span of 34MHz.

As far as programming is concerned you can use native 568x VIs in LabVIEW or can use C APIs for USB 568x, more information about the C APIs are located in Start>> All Programs>> National Instruments>>NI 568x>>Documentation. Here is a good article that might help you.

Good Luck !

NI-khil 

[L.Saint]

hi,Khil

Where can i find native 568x VIs in LabVIEW?What i can get is two examples of ni568x (Getting Started and Averaging).

But i can`t find out those VIs in Functions...

BTW,can i use NI-RFSA to program in order to acquire data from USB-5680?

B.R

L.Saint

[Anthony_F]

Hello L.Saint,

The NI-5680 is not a device supportedby the RFSA driver. You will need to use the NI-568x driver available from www.ni.com/drivers.  If you have already installed this driver it will appear in the Function windows under Instrument I/O >> Instruments Drivers >> NI-568x.

[L.Saint]

Thank you so much!

Love NI....

[yash3207]

hello anthony_F ,

in our machine, there are 4 rf powermeters plugged through USB.

and when i connect them to pc. i can get powrmeters connected to my system device manager.

but it is not detected in NI front panel.

it occurs very frequently in all of the machines.

i have treid 3 pcs/

but the issue remain that all four rf powermeters arent shown in ni soft front panel

[shawn.t]

Hi Yash,

What are the model numbers for the 4 power meters? 5680, 5681, 5683, or 5684? Also, what version of the NI-568x driver do you have installed? If it's less than 15.0 can you upgrade?