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7

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 pointers on how to get rid of the spike. That spike is probably nothing surprising – just the LO leakage/DC offset, a very common artifact in direct conversion ...


4

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 considered bandwidth, assumptions on the modulation scheme, duration of transmission, generally: It's a estimation of received signal strength based on some property of ...


1

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 rational resampler doesn't require going to the common multiple of in- and output rate. The magic of polyphase filtering allows to operate at a lower rate. In fact, I'...


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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 help you: each of two potential the UBX per motherboard has a fixed frontend bandwidth of 160 MHz, and thus if you tune them to the same center frequency, you'd ...


1

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 the range of hundreds of MHz, not a mere handful! For your proposed rates, cheap ADCs can directly sample sufficiently fast. In fact, in the context of SDR, you'...


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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 processing in GNU Radio is performed on the complex baseband version of the received signal. You could tune the USRP to 900 MHz, then have two bandpass filters-- one ...


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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 baseband filter each IQ component separately with either a real FIR or real IIR low-pass filter. Or you can multiply a FIR low-pass filter kernel by those same ...


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