An injection-locked frequency doubler with improved odd-order spur suppression

This paper presents a novel injection-locked frequency doubler (ILFD) with good odd-order harmonic rejection ratio (HRR). By utilizing a pair of complementary input signals, the odd-order harmonics are cancelled out effectively after current summation, leaving the even-order harmonic components unaffected. This technique is easy to implement, effective, frequency-independent, and suitable for wide-band operation. Theoretically all the odd-order HRRs could be improved simultaneously. As a concept design, a 7 GHz ILFD is implemented in 180nm CMOS process. From post-layout simulation, odd-order HRRs achieved improvements of more than 30 dB.