Wideband Spectrum Monitoring

[DOHAAACB19619]

Hi everybody.
I downloaded the Wide band Spectrum Analysis example as my project is to make spectrum scan for certain area I tried it , but there is a problem that it may be an obstacle in my project .
http://www.ni.com/white-paper/13882/en
the software is:labview2015
the hardware is:USRP2932

I HAVE TWO QUESTIONS:
(1)connecting the laptop to the usrp2932 and inserting the suitable parameters , the starting frequency is[2400]MHz and the stop frequency is[2410]MHz so I want t make a scan for only [10]MHz the problem is that half of the [10]MHz will be scan,the attached screen shot showing this problem.

(2)when I insert  the starting frequency is[2400]MHz and the stop frequency is[2500]MHz so I want t make a scan for [100]MHz the problem is that there are many discontinuities along all the band ,any one can give me an answer for these two problems and how I can solve these problems ,there is an screenshot for the results.

[Stop_Luke_and_Listen]

Hi DOHAAACB19619,

I'm working on reproducing the issue you are seeing with this example.  I'll let you know what I find.

[DOHAAACB19619]

Hi  Stop_Luke_and_Listen,

 thank you very much ,I am grateful for your help,I want to tell you that this project is very important for me and this issue made me stop ,so I will wait your solution ,

thanks,

[Stop_Luke_and_Listen]

Hi DOHAAACB19619,

After taking a look at the code and running some tests with a USRP, I believe I can provide some answers to your questions.

1. The reason that you aren't getting the full spectrum is a result of how the code determines what carrier frequencies to acquire. The code uses a ramp function to create an array of carrier frequencies that starts at the Start Carrier input, ends with the Stop Carrier input, and has a delta of 0.25*IQ Sampling Rate. This means that the carrier frequency is determined by the function: Carrier Frequency(k)=Start Carrier Input + k*0.25*IQ Sampling Rate where Carrier frequency<=End Frequency. So if you input your parameters into this function you get the following carrier frequencies: 2.4 and 2.40725 GHz. If you decrease your IQ rate you will be able to get closer to your full acquisition bandwidth.

2. The reason you are seeing the “discontinuities” in your spectrum is because of LO leakage. The LO frequency is being set near the carrier frequency at every iteration of the acquisition so that the LO leakage ends up in every frame of the wide band acquisition. You can set the LO frequency manually out of band of the acquisition using the LO Frequency property of the NI-USRP driver.