**7. Conclusions**

A highly reliable RF WuRx is presented for ETC systems in this article. For improving WuRx reliability and enhancing battery performance, the IDC is proposed as final stage. The IDC also acts as filter and replaces complex and power demanding analog blocks such as BPF, ADC, and FD. With the proposed configurable digital controller, high reliability and accuracy are achieved by sensing and ensuring a successive, configurable number of wake-up signal cycles before enabling power hungry RF transceiver. The presented self-hibernation technique reduces IDC and RC oscillator current consumption during the non-wake-up period and improves battery life. The digital hysteresis accommodates wake-up signal frequency variation and enhances WuRx accuracy. To avoid uncertain conditions during poor and false wake-up, a watch-dog timer for IDC self-recovery is integrated. During wake-up, the digital controller requires 34.62 nW power. In self-hibernation mode, its current reduces from 38.47 nA to 9.7 nA. It is fully synthesizable and needs 809 gates for its implementation in a 130 nm CMOS process with an area of 94 × 82 μm2. The WuRx measured power consumption is 2.48 μW, has −46 dBm sensitivity, and a 0.484 mm<sup>2</sup> chip area. The extensive measurement and verification make the proposed WuRx an ideal solution for a highly reliable DSRC wake-up circuit.

**Author Contributions:** K.-Y.L. guided and directed the authors for this research. I.A. proposed, designed, simulated, and implemented the overall architecture and wrote the paper. M.A., M.R.U.R., D.K., and H.Y. contributed to the synthesis and place and route (P & R) simulation. They also contributed to the design of the top layout of the chip. S.J.K. helped writing the paper, designing the testing board, and during the measurements. Y.P. and S.-S.Y. gave advice about implementation issues and reviewed the paper before submission. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the National Research Foundation of Korea (NRF) gran<sup>t</sup> funded by the Korean governmen<sup>t</sup> (MSIP) (2014R1A5A1011478).

**Conflicts of Interest:** The authors declare no conflict of interest.
