The ON/OFF keying (OOK) transmitter is re-investigated to utilize its structural simplicity and low power features for the reliable, ultra-low power sensor network applications. A novel architecture of 2.4-GHz ternary sequence spread spectrum (TSSS) OOK transceiver with spreading gain, spur suppression, and dual-mode detection techniques is presented. A random bi-phase operation of a power amplifier rejects the intrinsic spur of spread spectrum OOK transmitter by 22 dB. A proposed TSSS-OOK transmitter supports a variable spread spectrum, such as 1 b to 4 chips (1/4), 3/8, and 5/32 and a dual reception of the coherent as well as non-coherent mode, achieving 12-dB SNR gain. For the power optimized frequency synthesis, both a phase locked loop (PLL) and a frequency locked loop (FLL) are merged with a single voltage controlled oscillator as a dual-precision frequency synthesizer, where the high-precision PLL is activated for the coherent reception and the low power, moderate precision FLL is activated for the non-coherent reception. The single-chip transceiver in 90-nm CMOS occupies an active area of 2.4 mm(2) and measures 1Mb/s, 22-dB spur-suppressed output spectrum, 5.5% EVM, and a sensitivity of -81 dBm at non-coherent mode and -93 dBm at coherent mode, dissipating 2.17 mW at TX and 0.614 mW at RX.