Wide-locking range LC-tank divide-by-4 injection-locked frequency divider using transformer feedback

Abstract

A wide locking range, injection locked frequency divider (ILFD) circuit topology is explored. The modulus‐four ILFD utilizes a cross‐coupled voltage‐controlled oscillator in conjunction with transformer feedback, parallel‐tuned resonator, and two‐segment, series mixers at the injection point. The transformer feedback and two‐segment mixing circuit topology achieves a locking range of 2.7 GHz (14.1 to 16.8 GHz) at an injection point bias of 0.9 Vdc and 0 dBm injection power. Spectral measurements at the ILFD output demonstrate proper phase‐lock operation and expected phase noise reduction using a high quality signal source at the ILFD input. The ILFD is implemented in the TSMC 0.18 μm 1P6M CMOS process, utilizes a die area of 0.839 × 0.566 mm2 and consumes 16.56 mW. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:557–562, 2015.

Review of Injected Oscillators

“…Due to the small locking range of injected LC oscillators, various techniques have been realized to enhance the locking range. Passive and active structures are explored for improving the injection efficiency such as combining inductors in series or parallel with the injection mixer to enhancing its transconductance, body biasing, transformer feedback, dual-resonance RLC resonators, dual injection for increasing the voltage and current injection paths, tapped resonators, switched resonators, harmonic suppression, and distributed injection to distribute the injection signals; in other words, the injection component is divided to several smaller components; input-power-matching and inductive input-matching network is located to the gate of the NMOS switch to heighten the injection power [63][64][65][66][67][68][69][70][71][72]. Figure 6 discloses a quadrature LC oscillator employed in the injection signal.…”