A quadrature modulator based scheme for frequency hopping applications

摘要

In this study a new frequency hopping scheme which relies on digital up-conversion of baseband data is proposed. Since the frequency of the local oscillator is kept constant and hopping is achieved in the baseband, the time required for the frequency jump is independent of the frequency step, allowing a narrow loop bandwidth and low noise performance for conventional phase locked loops (PLLs). Moreover the spurious signals resulting from the modulator is around -70 dBc, which is a lower value when compared to spurious signal performance of commercially available direct digital synthesis (DDS) integrated circuits. We have analyzed the error vector magnitude (EVM) and frequency hopping speed on a practical setup and have shown that quite satisfactory results can be obtained with the proposed scheme.