Development of High Isolation Ping-Pong DDS-PLL Based Frequency Synthesizer for Fast Frequency Hopping Applications

High isolation ping pong based fast frequency hopping source is presented in this paper. The Direct Digital Synthesis (DDS) driving Phase Locked Loop (PLL) is adopted to design the frequency synthesizer. The proposed ping pong configuration not only minimizes the frequency switching time and tuning step but also reduces the self-interference between synthesizers. The measurement results shows that the single path of the proposed ping pong structure, a DDS-PLL frequency synthesizer with 80 MHz DDS output as PLL reference input, has the frequency switching time of less than 20 μs with 3 MHz hopping distance, the output frequency resolution of about 3 Hz, the spurious of better than -70 dBc, and the phase noise of -95 dBc/Hz at an offset of 10 kHz for the centre frequency of 2.4 GHz. The switching time of 2 ping-pong synthesizers is no more than 1 μs and the isolation of that is up to 73 dB.