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We present an ultra-low-power Bluetooth lowenergy (BLE) transceiver (TRX) for the Internet of Things (IoT) optimized for digital 28-nm CMOS. A transmitter (TX) employs an all-digital phase-locked loop (ADPLL) with a switched current-source digitally controlled oscillator (DCO) featuring low frequency pushing, and class-E/F 2 digital power amplifier (PA), featuring high efficiency. Low 1/ f DCO noise allows the ADPLL to shut down after acquiring lock. The receiver operates in discrete time at high sampling rate (∼10 Gsamples/s) with intermediate frequency placed beyond 1/ f noise corner of MOS devices. New multistage multirate charge-sharing bandpass filters are adapted to achieve high out-of-band linearity, low noise, and low power consumption. An integrated on-chip matching network serves to both PA and low-noise transconductance amplifier, thus allowing a 1-pin direct antenna connection with no external band-selection filters. The TRX consumes 2.75 mW on the RX side and 3.7 mW on the TX side when delivering 0 dBm in BLE. Index Terms-All-digital PLL (ADPLL), Bluetooth low energy (BLE), digitally controlled oscillator (DCO), discrete-time (DT) receiver (RX), Gaussian frequency shift keying (GFSK), intermediate frequency (IF), Internet of Things (IoT), low-power (LP) transceiver (TRX), matching network, transmit/receive (T/R) switch, transmitter (TX).

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We propose a new transmitter architecture for ultra-low power radios in which the most energy-hungry RF circuits operate at a supply just above a threshold voltage of CMOS transistors. An all-digital PLL employs a digitally controlled oscillator with switching current sources to reduce supply voltage and power without sacrificing its startup margin. It also reduces 1/f noise and supply pushing, thus allowing the ADPLL, after settling, to reduce its sampling rate or shut it off entirely during a direct DCO data modulation. The switching power amplifier integrates its matching network while operating in class-E/F2 to maximally enhance its efficiency at low voltage. The transmitter is realized in 28 nm digital CMOS and satisfies all metal density and other manufacturing rules. It consumes 3.6 mW/5.5 mW while delivering 0 dBm/3 dBm RF power in Bluetooth Low-Energy mode.

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Abstract-In this paper, reduction of peak specific absorption rate (SAR) for handsets with monopole type antenna through R-cards is investigated. While the numerical analysis was performed using finite integration in time domain (FIT), real measurement has been made to validate the simulation results. Both the simulation and measurement results revealed that a minimum SAR Reduction Factor (SRF) of 60% was achieved. The good agreement between the simulation and measurement results has evidenced the effectiveness of the proposed approach for SAR reduction in human head for handset applications.

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Vertical velocity data observed by SOUSY VHF radar from May 29 to June 2, 1978, are systematically analyzed. The altitude dependences of frequency spectra and wave number spectra are presented, and their physical implications are given on the basis of existing theoretical models. In this paper we will present the results of our analysis of both the frequency and wave number spectra of vertical velocity over 105 consecutive height ranges from 0.9 km to 16.5 km. We will then attempt to interpret the data using existing theoretical results. DATA STRUCTURE AND ANALYSIS PROCESSESThe data used in this report were taken with the Sounding System (SOUSY) VHF radar of the Max-Planck-Institut ffir Aeronomie between May 29 and June 2 of 1978. The radar is located in northern Germany and is described by Rb'ttger et al. [1978]. Pulse modulation, coherent detection, and on-line preintegration to raise the signal to noise ratio were applied, and the raw data were stored on magnetic tapes for off-line analysis. The radar operated at a frequency of 53.5 MHz, and it was pointed vertically with halfpower beam width of 10 ø. Two hundred fifty-six consecutive radar echo signals were on-line preintegrated within a time interval of 1.03 s to give one record; each record includes 105 complex data for 105 different height ranges between 0.9 km and 16.65 km with height resolution of 0.15 km. The raw data include continuous observation data of 11 consecutive time sections (see Table 1).Thirty-two consecutive complex signals of the same height were Fourier transformed into a power spectrum, and then two consecutive power spectra were averaged to obtain a smoothed Doppler spectrum with integration time of 65.92 s (= 1.03 x 32 x 2 s). If aliasing occurred in the Doppler spectra, it was systematically eliminated [Kuo et al., 1984]; thus the first three moments rno, rnx, and rn2 of each Doppler spectrum yield the essential parameters of the radar echo,