Challenges for Software Defined Radio
Receiver analog/antenna frontends
Transmitter Power Amplifiers and antenna frontend
While the first two are progressing well, the last two are not. Frontends are insufficient and power amplifiers lack multiband solutions. What's more, there's little research going on for the last two. The primary challenge here is that the receiver needs the ability to receive a weak signal in spite of a strong interfering signal given that software defined radio applications are often targeted to operate in a crowded and noisy spectrum space. For antenna/RF front ends the problem relates to antenna basics not software or waveform. One potential solution is tunable passive filters or switched filter banks. There are examples of these in the market but they are under developed at this stage.