A 0.2–2.6 GHz reconfigurable direct conversion receiver is proposed in this article. The receiver’s high-linearity mode and high-gain mode can be configured by either bypassing or including the low-noise amplifier (LNA) stage. An agile-switching module is designed to facilitate the mode transitioning. In high-gain mode, a variable-gain current-reused shunt-feedback (VGCRSF) LNA with radio frequency (RF) gain-adapted impedance matching technique is proposed. Instead of utilizing a shared transconductance (Gm) stage in both the I- and Q-path, the Gm-separated IQ-leakage suppression (GSIQLS) structure is employed in the mixer stage to reduce the complex and frequency-dependent IQ mismatch engendered by the nonideal local oscillator (LO) signal overlap. In baseband, both the gain and the bandwidth are made configurable through the utilization of a bi-quad low pass filter (LPF) and a programmable gain amplifier (PGA). The proposed receiver is fabricated in a 40-nm CMOS technology. Measurement results indicate a maximum conversion gain of 78.5 dB and a minimum noise figure (NF) of 2.5 dB are achieved. The input 1-dB compression point (IP1dB), in-band (IB) third-order input-referred intercept point (IIP3), and out-of-band (OOB) IIP3 are larger than 0, 9.7, and 13.1 dBm, respectively. The gain and phase mismatch of the quadrature receiver are lower than 0.3 dB and 1°, respectively, over the baseband bandwidth ranging from 410 kHz to 24 MHz. The receiver occupies an area of 0.605 mm2 and consumes a power of 75.4 mW.

This paper proposes a look-up-table (LUT)-based background calibration to improve the linearity of the ring voltage-controlled oscillator (VCO)-based analog-to-digital converter (ADC). The nonlinearity of the tuning gain$(\boldsymbol{K}_{\mathbf{VCO}})$of the VCO is considered as that there is an individual$\boldsymbol{K}_{\mathbf{VCO}}(\boldsymbol{K}_{\mathbf{VCOI}})$for each ADC output level. The$\boldsymbol{K}_{\mathbf{VCO}}-\mathbf{Locked}-\mathbf{Loop}$(KLL) is employed to force the$\boldsymbol{K}_{\mathbf{VCOI}}\mathbf{s}$to the same reference value, thus eliminating the nonlinearity. The effectiveness of the KLL-assisted linearization scheme is not affected by the matching property of the technology and the characteristics of ADC input signal. Thanks to the KLL-assisted calibration, the total harmonic distortion is suppressed by 37.8dB with the required ADC output samples of 218, achieving a fast linearization process.

This paper presents an energy-efficient single-ended (SE) transmitter (Tx) for memory interfaces, supporting non-return-to-zero (NRZ) and four-level pulse amplitude modulation (PAM-4) dual modes. The dual-mode Tx fully reuses the output driver, allowing high-performance impedance matching at the “/” and “1”/“11” levels of the NRZ/PAM-4 mode, and enabling low-power relaxed impedance matching at the “01” and “10” levels of the PAM-4 mode. The pre-emphasis equalization is proposed with high energy efficiency to enlarge the eye-opening using impedance modulation and a half-rate charge pump for the ground-terminated dual-mode Tx. The five-step three-point impedance (ZQ) calibration with offset cancellation is performed to enhance the level separation mismatch ratio (RLM). Implemented in a 22-nm CMOS process, the Tx achieves the data rate of 16 Gb/s/pin NRZ drawing 8.07 mW over a 12.9-dB loss channel and of 32 Gb/s/pin PAM-4 drawing 6.87 mW over a 4.6-dB loss channel with 99.0% RLM.

Recently, multi-rotor unmanned aerial vehicles (UAVs) have grown rapidly in popularity due to their simple structure, low cost and ease of operation. And they have been widely used in both academic research and commercial applications. As a core component of UAV, autopilot is normally used to realize autonomous control and navigation, including platform stabilization, flight trajectory generation, mission planning and so on. In this paper, we present a survey of existing autopilots for multi-rotor UAVs. First, we will introduce background and principle configuration of autopilots. Second, we will compare and analyze several popular autopilots in the market. Besides, several quality control methodologies will be introduced to improve the reliability and robustness of autopilots. Finally, we will discuss possible trend and technologies for autopilots in future.