Low cost high frequency signal synthesis: Application to RF channel interference testing

The quality of a communication link is commonly indicated by signal to noise/interference ratio and affected by noise and interference variance. To ensure a power efficient adaptive OFDM system´s performance, the system needs to be tested against various channel conditions. Conventional algorithms and experiments assume that the noise and interference density stays constant over the OFDM frequency band but in reality the communication link often populated with both white noise and interference that results an uneven impact on OFDM spectrum. To create such channel condition, an up-conversion is commonly used. However, due to the non-linearity of the mixer, the up-converted interference is always distorted. The proposed method uses a modified higher-than-Nyquist-rate RF signal generation algorithm to minimize the distortion of generated interference within a pre-defined output bandwidth. Both concept validation and experimental measurement have been conducted to prove the effect of proposed method.