Harmonic-injection divider based on feedback through a nonlinear transmission line

An application of nonlinear transmission lines (NLTLs) to the design of harmonic-injection frequency dividers by high division order is presented. The NLTL, composed by inductance-varactor cells, is used as a feedback block of an active-device circuit, which gives rise to a free-running oscillation. Due to its highly nonlinear behavior, the NLTL can be optimized to enhance the harmonic components required for high order division through mixing with the input signal. The frequency bandwidth is further increased through a combination of phase-locking and frequency-locking effects. This is done extracting an error baseband signal from the active-device output, which, after suitable amplification, is applied to the varactor diodes of the NLTL. A design procedure is also presented to enable the switching of the division order between N and N-1 through control of the bias voltage. The novel configuration can have the advantage of a low complexity, low dc power consumption, and scalability. The new concept has been applied for the design a dual-order frequency divider by 10 and 9 with about 2% bandwidth.