Frequency Agile Analog Kramers–Kronig Receiver in Silicon

Direct detection (DD) receivers (RXs) offer low power and complexity for high-frequency wireless communication but suffer from signal-to-signal beat interference (SSBI), which degrades signal quality. Kramers–Kronig (KK)-based RXs mitigate SSBI by recovering phase from amplitude, but conventional implementations are hindered by heavy reliance on digital signal processing (DSP), non-real-time operation, and spectrum broadening, limiting hardware integration. This article introduces an innovative fully analog detection scheme for a CMOS integrated circuit (IC) KK RX. Our solution employs Taylor-series expansion for nonlinear circuits, a poly-phase filter (PPF) for Hilbert transform, and an entirely analog RF signal chain. These techniques enable a low-power, local oscillator (LO)-free coherent DD RX capable of real-time signal reception without spectrum broadening, and they support coherent reception across various carrier frequencies. We demonstrate this technique with a W-band KK-based RX in a 65-nm CMOS process, achieving a 200-Mb/s modulation rate. The design shows a 1.8-dB error vector magnitude (EVM) improvement, 82.89% bit-error-rate (BER) improvement, and 0.8-dB carrier-to-signal power ratio (CSPR) reduction compared with conventional methods. The RF frontend exhibits 3.4-kV/W responsivity and 14.2-dB noise figure at 90 GHz, with the core module consuming 29 mW of dc power and occupying 0.132 mm2. These results highlight the potential for enhanced energy efficiency and local oscillator-free, coherent reception in high-frequency communication.