It is then possible, through HW modifications, to interpose 2 differental analog baseband filters in order to improve the system in addition to oversampling. For example, if you oversample by 128 around 4 Msamp/s, you will obtain an effective sampling rate of around 31 Ksamp/s, thus a combined I/Q bandwidth of 31 KHz after digital filtering, with an effective number of bits of 8+3,5=11,5 bits (70 dB dynamic).Īnalyze of the used Realtek chipset shows analog I/Q signal if fed to digital A/D-USB chip via 4 capacitors (I/Q differential interface). This is OK for a single signal, isolated from others by physical filtering (TV signal indeed !), but not enough for narrowband multisignal handling (14 to 16 bits being a minimum).Ī solution is to oversample your baseband, and then decimate to increase the effective number of bits. However, be carefull, you have what you get for 20 $.I/Q interface is 8 bits which means around 48 dB maximum dynamics. While it may not be as cool as 's SDR, it's still very useful and only requires $20 in hardware. With a simple digital TV USB capture card, you can build your own software defined radio or spectrum analyzer.
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