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11 votes
Accepted

Large spike at the center frequency when using Ettus X310

The problem that I have is that I always have a big spike (10-15 dB) directly on the center frequency (no matter what frequency I set). I am relatively new to all this so I would appreciate any ...
Marcus Müller's user avatar
4 votes
Accepted

Possible to Derive Receive Signal Power from RSSI?

I also read this from a response to a USRP user's question about RSSI measurements: [The] Received Signal Strength [Indicator is] always relative to some signal model, incorporating ...
Marcus Müller's user avatar
2 votes

Best way to resample an OFDM signal without interpolating + filtering?

I can't resample this signal using an interpolation plus filtering approach, as it should be computed in real time (I would need to interpolate the signals up to 480 MHz...). Fallacy! Using a ...
Marcus Müller's user avatar
2 votes
Accepted

How is the Tx/Rx Gain calculated in USRP?

The term "gain" is pretty appropriate. It's a number describing the output power relative to some arbitrary base power. So I would like to know how this transmitter channel gain process is ...
Marcus Müller's user avatar
2 votes
Accepted

Calculating transmitter power from spectral density

You're right, to convert from a power density to a power, you integrate over frequency! However: Well, if neither of your transmitter nor receiver are calibrated, then you simply can't find the "...
Marcus Müller's user avatar
2 votes

USRP N310 RX gain lower than other SDR with same GNURadio script

These devices are not calibrated. There's not even a hint at a guarantee that they have the same output power for the same gain settings! So, this is expected; note that the absolute digital receive ...
Marcus Müller's user avatar
2 votes

Can I create my IF signal on SDR before bringing data to PC?

I think the formula you got the 1m resolution from is actually the one for pulse radars with non-interpolating single pulses. You can do better! Note that in (linear-chirp) FMCW, the beat frequency, i....
Marcus Müller's user avatar
1 vote

Questions about the output sampling rate of the DUC(interpolation filter) of the USRP N210

I found that according to the user manual[1] AD9777 has an input sample rate of 160M and an output of 400M. So the sample rate of the DUC output of the N210 is 160MSps? How does USRP interpolate ...
Marcus Müller's user avatar
1 vote
Accepted

Phase Measurements of OFDM Signal with USRP

The unwrapping matlab function produces fake wraps (phase jumps) due to noise. This creates a cumulative error in all following phase samples. This usually happens when the SNR is low. To solve this ...
wesam amiri's user avatar
1 vote

USRP Frequency Drift Measurement

The issue that I am facing is how to get the modulated signal from the TX before the transmission through the antenna. Since that's already an analog RF signal: You would need a receiver. So, you'd ...
Marcus Müller's user avatar
1 vote
Accepted

Can I create my IF signal on SDR before bringing data to PC?

The theoretical data rate to transmit a signal with bandwidth $W$ Hz and resolution $R$ b/sample is simply $2WR$ b/s. In practice, you will need somewhere between that and $4WR$. One way to reduce the ...
MBaz's user avatar
  • 15.3k
1 vote

gnuradio , SDR usrpx300

I'm confused about Bandwidth and sample_rate. How i do calculate them? is sample_rate = Bandwidth? Sample rate: This is a design parameter, not usually something you caclculate, but a requirement ...
Marcus Müller's user avatar
1 vote

Periodic Jumps in received signal

I would guess it is some sort of frequency control, that automatically changes some of the circuit parameters to match the desired frequency. It could be done through a lower frequency oscillator, ...
Surprised Seagull's user avatar
1 vote

GNU Radio, Frequency Hopping Spread Spectrum for High Hopping Intervals

No you cannot change the carrier frequency of your local oscillator instantaneously. The RF local oscillator will be in a Phase-Lock Loop (PLL) circuit to a low frequency reference (to provide ...
Dan Boschen's user avatar
  • 50.2k
1 vote
Accepted

Confusion about the frequency of a signal recorded with a USRP

The USRP is taking a frequency band of width 256 kHz centered on 710 kHz, and downconverting it to baseband. Whatever is in that band will appear in the USRP output. To be specific, the band that the ...
MBaz's user avatar
  • 15.3k
1 vote

LoRa sensing using USRP GNURADIO

500 kHz (watch the capitalization: Khz is wrong!) is a very low sample rate for the N210. In fact, the N210 has to decimate by a factor of 200 from its ADC's sampling rate, and that might introduce ...
Marcus Müller's user avatar
1 vote
Accepted

Could 2 synchronised RX chains be used to receive a signal too wide for just one of them?

So, while you possibly could with extensive modification to the digital logic, theoretically allow the two (dual-)ADCs of the X3x0 motherboard to be offset by half a clock cycle, that still wouldn't ...
Marcus Müller's user avatar
1 vote

Could 2 synchronised RX chains be used to receive a signal too wide for just one of them?

In lack of more background, I can only give a general answer: What you describe is simply an interleaved ADC; that is a technique employed in very high-rate ADCs. And high-rate definitely is more in ...
Marcus Müller's user avatar
1 vote

Bandpass filtering IQ samples from USRP

One easy way would be to use GNU Radio, specifically GNU Radio Companion, to design your signal processing chain. GNU Radio has a large library of built-in signal processing blocks. All signal ...
Robert L.'s user avatar
  • 2,212
1 vote

Bandpass filtering IQ samples from USRP

There are many possible methods to isolate those 2 signals. You can heterodyne your IQ signal up or down by 25MHz by multiplying by a complex exponential of plus or minus that offset frequency, then ...
hotpaw2's user avatar
  • 35.3k

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