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Accurate time is essential in modern society; hence, the question of how to achieve accurate time synchronization of timekeeping devices at low cost is an important issue. Moreover, accurate time synchronization is required for instruments in factories and laboratories in closed networks to ensure the smooth operation of different processes to further improve the product quality. Using light emitting diodes (LEDs) for indoor lighting to conduct visible light communication, this system enables the broadcast transmission of time-related information to achieve time synchronization of all timekeeping devices. This system can realize the function of time synchronization at low cost while also transmitting additional data to effectively lower the system building cost.

A divide-by-4 injection-locked frequency divider (ILFD) with wide locking range is proposed. The divide-by-4 ILFD works by mixing the injection signal and the third harmonic. The frequency translation is given by ωRF - 3ω0 = ω0. A new method is demonstrated by mixing the second harmonic with the fundamental signal to generate the required third harmonic. It is different from the conventional method by directly employing the third harmonic of the non-linear amplifier. The measured locking range is from 20.8GHz to 27.6GHz (28.1%) with an output power of -0.4dBm as the core-circuit taking a power consumption of 3.68mW from 1V power supply.