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Message started by RFn00b on Sep 25th, 2019, 6:32pm

Title: Loading LTE Signal on RF ASIC
Post by RFn00b on Sep 25th, 2019, 6:32pm

Hi guys,

First of all, I apologize in advance if my question makes no sense, but this is the first time I am dealing with an entire RF transmitter. For my research project in grad school I designed an RF transmitter that includes a digital baseband (SPI and SRAM for loading the IQ samples), analog baseband (IQ DACs and filters), and the RF frontend (mixer and a class-A PA driver).

I would like to test the performance by loading an LTE signal. For this purpose I am generating the LTE signal in MATLAB using the LTE toolbox and in the lab I have the R&S K101 LTE module installed in the FSW26 Spectrum Analyzer. From my understanding, the module needs to read at least 1 LTE subframe to synchronize. The LTE signal sampling rate is specified by the standard, e.g. for 100 resource blocks (RB) it uses 30.72 MHz sampling rate. Given that the duration of the subframe is 1ms, this translates to 30720 samples. However, the SRAM of my ASIC can only hold 8192 samples, which should be enough for narrower bandwidths (25 RB or less). To complicate things, I would like to increase the sampling rate to a higher value for my application for filtering purposes. In other words, there needs to be some upsampling, downsampling and FIR filtering. Do you know, if there is a way to correctly populate the SRAM, so that the K101 module can correctly demodulate the subframe? It may very well be that what I am asking for is impossible given the SRAM restriction.

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