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This article presents a 0.3-V, −75.8-dBm differential wake-up receiver (WuRX) with temperature robustness for wireless sensor network (WSN) applications. In this work, an adaptive gate-biased pseudo-differential envelope detector (ED) with temperature compensation is proposed to achieve high conversion gain, wide range of tunability, and temperature robustness at the cost of low power consumption. To address the problem that the high supply voltage of the baseband amplifier (BB-AMP) limits the further reduction of the overall system supply voltage, a bulk-driven differential BB-AMP is also proposed, the characteristics of its ultralow supply voltage make the system supply voltage as low as 0.3 V. And the dual path offset calibration loop is proposed to eliminate all mismatches and offsets in the differential signal path, further ensuring the system robustness. This WuRX is implemented in a 65-nm LP CMOS process, operates at 434 MHz, consumes 6.96 nW from 0.3-V supply voltage, and achieves a sensitivity of −75.8 dBm at 250 bps. When the temperature changes from −10 °C to 50 °C, the sensitivity varies from −77.5 to −73.6 dBm. [ABSTRACT FROM AUTHOR]

An impulse radio ultra-wideband (IR-UWB) transceiver is implemented with low power, high data rate communication techniques, such as extended multipulse position modulation (E-MPPM), cross-coupled (CC) envelope detection, and digital frequency hopping (DFH). The use of the E-MPPM helps increase the modulation efficiency. The capacitive-CC technique helps improve the sensitivity by increasing the conversion gain of an envelope detector. DFH increases the pulse energy of a transmitted impulse without sacrificing the power spectral density (PSD) requirement. The proposed CMOS transceiver achieves a data rate of 1.125 Gbps and a radio range of 2 m with a power consumption of 28 mW and energy efficiency of 24.9 pJ/b. [ABSTRACT FROM AUTHOR]

The significant amount of unused spectrum in sub-TeraHertz frequencies is contemplated to realize high rate wireless communications for beyond 5G networks. Yet, the performance of radio-frequency sub-TeraHertz systems is severely degraded by strong oscillator phase noise. Therefore, we investigate in this paper the use of multiple-input multiple-output (MIMO) systems with energy detection receivers to achieve high rate communications robust to phase noise. First, the design of the receiver detection algorithm is addressed. Two detectors are proposed for the studied nonlinear MIMO channel, either derived from the maximum likelihood decision rule by using a Gaussian approximation, or based on the use of neural networks. Second, the communication performance is assessed through numerical simulations for uncoded and coded systems. We consider a realistic scenario modeling an indoor wireless link in D-band with directive antennas and strongly correlated line-of-sight channels. Our results demonstrate that spatial multiplexing with non-coherent sub-TeraHertz transceivers can be realized on strongly correlated line-of-sight channels using the proposed detection schemes. Thereby, we highlight that high-rate radio-frequency sub-TeraHertz systems can be implemented with low-complexity and low-power architectures using MIMO systems with energy detection receivers. [ABSTRACT FROM AUTHOR]

This brief presents a high-speed detector targeting quasi-coherent optical receivers operating up to 28 Gbps data rates. The circuit consists of a balanced rectifier based on diode-connected heterojunction bipolar transistors (HBTs) together with tailored input and output filtering networks. The rectifier is buffered by a linear DC-coupled single-ended to differential amplifier providing a $50\,\Omega $ output interface. The design was fabricated in a commercial 130 nm SiGe BiCMOS technology with f textsubscript t/f textsubscript max of 250/340 GHz, and was tested on a quasi-coherent receiver setup. Optical receiver sensitivity better than −28 dBm and −26 dBm (FEC-limited BER of 1E-3) is demonstrated, respectively, at 25 and 28 Gbps data rates. To the best of the author’s knowledge, the reported circuit represents the fastest envelope detector published to date. [ABSTRACT FROM AUTHOR]

In this letter, a novel near-field imaging method based on the startup time of the oscillator is proposed and validated by a circuit implemented in the 55-nm CMOS process. An interdigitated capacitor (IDC) is used as the sensor element and embedded in the oscillator. The simulation and measurement results show that the sensing oscillator’s startup time increases with the permittivity of material under test (MUT) accordingly. The core area of the near-field sensor is 0.154 mm $\times \,\, 0.123$ mm and the power consumption is 2.7 mW. The small area and low power consumption make it quite suitable for near-field imaging array and biomaterials detection. [ABSTRACT FROM AUTHOR]

The lack of an envelope detector (ED) hinders the realization of bidirectional communication between radio frequency identification (RFID)/near field communication (NFC) tags and readers in metal-oxide thin film transistor (TFT) technology. To solve this, we present a novel ED implementation based on unipolar metal-oxide TFTs. The ED is fully integrated by n-type TFTs and has a novel topology. It can detect an amplitude shift keying (ASK) signal with a minimum modulation depth of 15% and a maximum envelope rate of 8kbit/s, and its minimum supply voltage reaches 2.5 V. These characteristics are greatly improved compared with those of previous works based on complementary organic or hybrid organic/metal-oxide TFTs. [ABSTRACT FROM AUTHOR]

This brief presents a trim-less precision envelope detector for fail-safe circuit in LVDS receiver. A preamp is proposed using gm-constant biasing concept to produce an accurate gain of 9.78 dB across PVT covering the full range of the LVDS input common-mode voltage. The preamp produces a fixed output common-mode voltage of 200 mV across supply voltage variation which reduces its complexity by alleviating the need of a trimming circuit. A unique reference voltage generation of the envelope detector based on level shifted output common-mode voltage accurately compares the output common-mode and negative peak voltages to set the detection threshold. An LVDS receiver adopting the proposed envelope detector was fabricated on a standard 0.13-μm CMOS. With a supply voltage of 3.3 V, the envelope detector achieves a voltage trimming precision of 20 mV while only consuming 162 μW of power. [ABSTRACT FROM AUTHOR]

In response to anticipated shortages of ventilators caused by the COVID-19 pandemic, many organizations have designed low-cost emergency ventilators. Many of these devices are pressure-cycled pneumatic ventilators, which are easy to produce but often do not include the sensing or alarm features found on commercial ventilators. This work reports a low-cost, easy-to-produce electronic sensor and alarm system for pressure-cycled ventilators that estimates clinically useful metrics such as pressure and respiratory rate and sounds an alarm when the ventilator malfunctions. A low-complexity signal processing algorithm uses a pair of nonlinear recursive envelope trackers to monitor the signal from an electronic pressure sensor connected to the patient airway. The algorithm, inspired by those used in hearing aids, requires little memory and performs only a few calculations on each sample so that it can run on nearly any microcontroller. [ABSTRACT FROM AUTHOR]

The signal’s envelope contains important features for a host of applications empowered by machine learning algorithms. Conventionally, the raw analog signal is digitized first, followed by feature extraction in the digital domain. This brief presents an ultra-low-power envelope-to-digital converter (EDC), with respiratory monitoring as one of its applications. The EDC consists of a passive switched-capacitor envelope detector and an inseparable successive-approximation-register analog-to-digital converter (ADC). The two blocks at different sampling rates directly integrate without a buffer between them thanks to a ping-pong operation of their sampling capacitors. An EDC prototype was fabricated in a 180-nm CMOS. It provides 7.1 effective bits of ADC resolution and supports input signal bandwidth up to 5 kHz and an envelope bandwidth up to 50 Hz while consuming 9.6 nW. [ABSTRACT FROM AUTHOR]

This brief considers the design of an envelope detector for the front-end of a wake-up receiver. A design procedure that allows to optimize the trade-offs between gain, signal-to-noise ratio and power consumption is proposed. It is based on the analysis of the envelope detector in all inversion regions. Two novel figures of merit that only depend on the inversion level are proposed to aid the design. The predictions are verified against simulation and measurements results, both at the transistor and complete circuit level. An arrangement for the bias circuitry of the wake-up receiver front-end is proposed that leads to an intrinsic bandpass characteristic that improves the signal-to-noise ratio. A prototype integrated circuit, in a 130 nm CMOS process, of a fully integrated wake-up receiver front-end for the 2.4 GHz band was designed based on the presented approach and measured. The results show a remarkable conversion gain with a scaling factor of 9800 1/V with a current consumption of 100 nA from 1.2 V at 12 dB signal-to-noise ratio and −48.5 dBm sensitivity. [ABSTRACT FROM AUTHOR]

This paper presents the development of a wake-up receiver (WuRX) at nanowatt power levels for event-driven applications. This paper improves the state of the art, obtaining higher sensitivity than previous work in the 151.8- and 433-bands, low-power operation, and robustness to interference due to an integrated offset compensation algorithm operating without any external calibration. Simultaneous low-power operation and high sensitivity are achieved through a passive detector design based upon a terminal impedance boundary condition-based optimization of the detector dictated by the terminal impedances of the detector. This paper is implemented in a 130-nm CMOS process and obtains −76 dBm at the 151.8-MHz multi-use radio service (MURS) band and −71 dBm at the 433-MHz Industrial, Scientific and Medical (ISM) band with a total dc power draw of just 7.6 nW from 1.0- and 0.6-V supplies. [ABSTRACT FROM AUTHOR]

Piezoelectric vibration energy harvesting (PVEH) has been proved to be much promising in making low power electronics completely self-powered due to wide availability and high energy density. Self-powered synchronized switching harvesting on an inductor (SSHI) circuits have been proved to greatly increase the performance of a PVEH device and peak detector-based self-powered switches are widely used. In practice, however, the switch is impossible to turn on simultaneously at peak displacements due to nonlinear components so that switching delay (SD) always exists. Furthermore, the SD will degrade the performance of PVEH devices, so it must be reduced. Therefore, for this kind of SSHI circuits, the purpose of this paper is to explore basic causes of generating SD and investigate the corresponding solution. First, theoretical model of SD in self-powered parallel SSHI (SP-PSSHI) is derived and the SD is first proved to be positive. Then, effects of key component parameters on the SD are studied. Based on above results, an improved SP-PSSHI (ISP-PSSHI) circuit is proposed by adding a voltage divider and its SD is proved to be less than that of the SP-PSSHI circuit. Next, the key factor is discussed, namely the divider resistor. Circuit simulations validate theoretical results and also expose that there are optimal resistor and capacitor of the envelope detector for achieving the maximum harvested power. In the end, experimental results show that the ISP-PSSHI circuit can improve the averaged harvested power about 11% more than that of the SP-PSSHI circuit under choosing optimal components. [ABSTRACT FROM AUTHOR]

In this paper, a multi-mode ultra-low power wake-up receiver based on direct envelope detection in HF/UHF band is analyzed and presented. Narrow-band LC matching network with passive voltage gain, active common source envelope detector with high conversion gain and baseband modules with signal amplification are clarified, separately. In order to balance the power consumption and sensitivity, multi-mode with power detection (PD), signal detection (SD), and high sensitivity signal detection (HSSD) are adopted. The PD mode is used to monitor the incident radio power, while in SD/HSSD modes, the wake-up sequences of 100/10 kb/s are detected with different power consumption and sensitivity. The presented wake-up receiver prototype is fabricated in a 95-nm CMOS process with an area of 0.6*0.3 mm2. Measurement results show that the wake-up receiver achieves a sensitivity of −45/−42 dBm, −43/−40 dBm and −58/−55 dBm while dissipating 120 nW, 600 nW, and 1 $\mu \text{W}$ in PD mode, SD mode, and HSSD mode, respectively, while working in the HF/UHF band, separately. [ABSTRACT FROM AUTHOR]

In future photonic-based THz backhaul links, integrating the optical local oscillator (LO) in a remote antenna unit can be beneficial in terms of optical bandwidth efficiency and higher compatibility with passive optical networks. In such a scenario, two approaches can be used to reduce the high phase noise associated with free-running lasers: 1) baseband (BB) signals & carrier recovery, and 2) single sideband (SSB) signals & envelope detection. In this paper, we compare the performance of the two approaches for various optical LO linewidths using 5 GBd 16-QAM signals. We find that, for a total linewidth wider than 0.55 MHz, the SSB approach yields better results. The superior performance, however, comes at the expense of reducing the net information spectral density (ISD) of the SSB signal by 39% compared to that of the BB signal. However, using signal–signal beat interference-mitigation algorithms, an ISD only 15% lower than the BB signal ISD was sufficient to meet the FEC requirement. Given these results, we believe that the envelope detection of SSB signals is a promising solution to mitigate the phase noise problem of THz links based on free-running lasers, without excessively compromising the spectral efficiency of the system. [ABSTRACT FROM AUTHOR]

A novel pulse integration has been put forward in which the radar receiver, before combining envelope detector outputs in all pulses, first clips them to a suitable level to suppress excessive energy inflicted by a jammer. Mathematical expressions for various decision metrics relevant to this scheme are derived. Using these metrics it is shown that the proposed scheme, when combined with frequency agility, yields healthy performance gain over similar detection schemes when operating against pulse jamming. [ABSTRACT FROM AUTHOR]

In the software-based resolver-digital converters, angular position and speed are often demodulated from resolver signals after envelope detection. The accuracy of demodulation depends on the degree of perfectness of two envelope signals of the resolver. However, the envelope signals cannot be derived perfectly from the resolver outputs and they are often disturbed by amplitude deviations, DC offsets, and nonorthogonal phase shifts. In order to attenuate the effects of the unexpected factors on the accuracy of demodulation, an offline automatic calibration strategy is proposed for the two envelope signals of the resolver based on two-step gradient estimators. The first-step estimator is designed to obtain the estimate of only one parameter, i.e., angular frequency. At the second step, another gradient estimator is designed to estimate amplitudes, DC offsets, and phases of the two envelope signals. Since the angular frequency is estimated by an individual estimator which is independent from the other parameters, its estimation accuracy can be improved effectively. By using the estimate of the angular frequency with higher accuracy, the accuracy of the second-step estimator also can be improved. The effectiveness of the proposed method is verified by simulation and experimental results. [ABSTRACT FROM PUBLISHER]

During a recent consulting job to analyze acoustic telemetry signals transmitted by a deep-sea drill pipe, I was forced to investigate a process called digital envelope detection. This process is used to estimate the instantaneous magnitude of a zero-mean fluctuating-amplitude digital signal. While much tutorial information regarding envelope detection is available, that information is spread out over a number of communications textbooks and many websites. The purpose of this article is to collect and describe various digital envelope detection methods in one concise and consistent lesson. [ABSTRACT FROM PUBLISHER]

A time delay estimation method based on wavelet transform and speech envelope is proposed for distributed microphone arrays. This method first extracts the speech envelopes of the signals processed with multi-level discrete wavelet transform, and then makes use of the speech envelopes to estimate a coarse time delay. Finally it searches for the accurate time delay near the coarse time delay by the cross-correlation function calculated in time domain. The simulation results illustrate that the proposed method can accurately estimate the time delay between two distributed microphone array signals.

In this paper, we propose and experimentally demonstrate a millimeter-wave (mm-wave) system at 75 GHz with discrete Fourier transform spread (DFT-S) orthogonal frequency-division multiplexing (OFDM) signal transmission. The baseband signal is modulated by a directly modulated laser at the transmitter, and the mm-wave signal is converted to a lower frequency one by an envelope detector at the receiver. The intrasymbol frequency-domain averaging (ISFA) is used for channel estimation and a Volterra nonlinear equalizer is adopted to mitigate the nonlinearity caused by signal–signal beat interference. In this system, a 2-Gbd 16-ary quadrature amplitude modulation (QAM) DFT-S OFDM signal is delivered over 4-m wireless link under the bit error ratio of 3.8 × 10−3. Our experimental results show that the ISFA and the Volterra nonlinear equalizer can improve the system performance by about 2-dB and 1-dB receiving sensitivity, respectively. This is the first time the Volterra nonlinear equalizer has been used in a W-band mm-wave system to improve wireless transmission performance. [ABSTRACT FROM PUBLISHER]

We propose an improved hop-timing acquisition scheme by adding self-normalization to the conventional scheme with three envelope detectors of full, early-half, and late-half hop periods. The results of analysis and simulation show that the proposed scheme has better antijam performance than the conventional scheme against a partial-band noise jamming. [ABSTRACT FROM AUTHOR]

An uplink system with a single antenna transmitter and a single receiver with a large number of antennas is considered. We propose a single-shot noncoherent scheme which does not use the instantaneous channel state information (CSI), but rather only the knowledge of the channel statistics, a transmitter that modulates information only in the amplitude of the symbols, and a receiver which measures only the average received energy across the antennas. This system model is motivated by the simplicity of the circuit design and the energy efficiency it entails for both the transmitter and the receiver. We propose constellation designs which are asymptotically optimal with respect to symbol error rate (SER) with an increasing number of antennas, for any finite signal-to-noise power ratio (SNR), under different assumptions on the availability of CSI statistics. We describe in detail the case when there is a bounded uncertainty on the moments of the fading distribution. We present the numerical results on the SER performance achieved by these designs and find that they outperform the existing amplitude-modulation-based noncoherent scheme of amplitude shift keying (ASK). They also achieve a smaller peak-to-average power ratio (PAPR) for scenarios with a low SNR or a large line-of-sight (LOS) component. [ABSTRACT FROM PUBLISHER]

A wideband spectrum sensing system for cognitive radio is designed and implemented in a 130-nm radio frequency mixed-mode CMOS technology. The system employs an $I-Q$ downconverter, a pair of complex filters, and a pair of envelope detectors to perform the spectrum sensing from 250 MHz to 3.25 GHz. The design makes use of the bandpass nature of the complex filter to achieve two objectives: 1) separation of upper sideband and lower sideband around the local oscillator signal and 2) resolution of smaller bands within a large detection bandwidth. The measured sensitivity is close to −45 dBm for a single tone test over a bandwidth of 40 MHz. The measured image reject ratio is close to 30 dB. The overall wideband detection bandwidth is 250 MHz, which is partitioned into 40-MHz narrowband chunks with eight such overlapping chunks. [ABSTRACT FROM PUBLISHER]

A low-power auto-wake-up image-reject receiver front-end in 90-nm CMOS technology is presented for V-band applications. The proposed front-end generally operates in the sleep mode and consumes 19 mW. When an RF signal greater than -\50 dBm is received, the front-end wakes up automatically and enters into the active mode consuming only 46-mW power. Adjustable linearity (IP{{1dB}}) of the front-end is provided by changing two gain modes (high- and low-gain modes). When input RF power is higher than -\30 dBm, IP{{1dB}} will be improved (from high-gain mode to low-gain mode). Experiments show IP{{1dB}} of -\25.2 and -\22.5 dBm in high- and low-gain modes, respectively. An image-reject ratio greater than 32 dB is measured when using the proposed image-reject mixer topology. All passive phase-shift couplers for realizing the image-rejection are composed of standard CMOS lumped elements, thereby considerably reducing the chip size (0.82 mm^2). [ABSTRACT FROM PUBLISHER]

A new CMOS differential current-mode AGC on the division operation based is presented. The operation principle consists in detection of both positive and negative envelopes of the differential input signal cycles, respectively. The output signal with constant magnitude is obtained by dividing the differential input signal to the difference between the positive and negative detected envelopes. The new current-mode architecture of the proposed AGC (composed only by an envelope detector and a divider stage) diminishes significantly the settling time, the circuit complexity and the power consumption. The circuit yields an input dynamic range of 15 dB and provides a constant magnitude output signal in the frequency range from 10 MHz to 70 MHz. The current consumption is 5 mA from a single 3.3 V supply voltage. The simulations performed in 0.13 µm CMOS process confirm the theoretically obtained results. [ABSTRACT FROM AUTHOR]

In conventional noncoherent radar pulse integration (NCPI), the radar receiver sums the envelope detector outputs obtained in multiple pulses from the target within one scan. A novel modification to NCPI is proposed in which the receiver first normalizes the envelope detector output in each range bin by the sum of envelope detector outputs corresponding to all range bins of a pulse. It is shown that the proposed scheme yields significant performance gain against noise jamming. [ABSTRACT FROM PUBLISHER]

A dedicated ultra-low power fully integrated FSK wake-up receiver (WuRx) for wireless body area network (WBAN) is implemented in 0.18 \mum CMOS technology with 0.7 V supply voltage. For low power consumption, a body channel communication (BCC) physical layer (PHY) is adopted with an 80 MHz carrier frequency. Moreover, an injection-locking digitally-controlled oscillator (IL-DCO) is used to provide an extraordinary gain and frequency-to-envelope conversion in the simple and power-efficient envelope detection receiver architecture. The IL-DCO plays an important role in amplifying and demodulating the received FSK signal under a tight power budget. Finally, for low system cost without any external components and calibration overhead, a successive approximation register (SAR) auto-calibration algorithm is proposed to promptly calibrate the frequency drift of the IL-DCO. As a result, the fabricated 1 mm^2 single-chip WuRX consumes 45 \muW with a data rate of 312 kb/s, providing an 80 MHz reference frequency with 0.25% stability within 102 \mus calibration time. The proposed WuRX delivers a stable reference clock to the main transceiver for crystal-less WBAN applications. [ABSTRACT FROM AUTHOR]

Analytical expressions are obtained for predicting the amplitudes of the harmonics and intermodulation products at the output of an envelope detector excited by a signal formed of a carrier plus a number of sidebands. These expressions are in terms of the ordinary Bessel functions with arguments dependent on the modulations indecies. Comparison between results obtained using the proposed technique and previously published results is performed to establish the accuracy of the proposed technique.

The paper presents a new approach to detection of apnea/hypopnea events, in the presence of artifacts and breathing irregularities, from a single-channel airflow record. The proposed algorithm, based on a robust envelope detector, identifies segments of signal affected by a high amplitude modulation corresponding to apnea/hypopnea events. It is shown that a robust airflow envelope—free of breathing artifacts—improves effectiveness of the diagnostic process and allows one to localize the beginning and the end of each episode more accurately. The performance of the proposed approach, evaluated on 30 overnight polysomnographic recordings, was assessed using diagnostic measures such as accuracy, sensitivity, specificity, and Cohen's coefficient of agreement; the achieved levels were equal to 95 $\%$, 90$\%$ , 96$\%$, and 0.82, respectively. The results suggest that the algorithm may be implemented successfully in portable monitoring devices, as well as in software-packages used in sleep laboratories for automated evaluation of sleep apnea/hypopnea syndrome. [ABSTRACT FROM PUBLISHER]

This paper is a practical illustration of the adoption of alternate tests based upon the judicious selection of the set of parameters to be considered for design as well as to be observed subsequently. The notion of signatures is introduced, and their ability to predict design accuracy is analyzed. The application is demonstrated for an RF LNA circuit. [ABSTRACT FROM AUTHOR]

In this paper, a radio-over-fiber (RoF) communication system at 60 GHz based on passively mode-locked laser diode (PMLLD) is presented and the performance of different electrical down-conversion methods (coherent and non-coherent down-conversion) for this communication system is studied. Impact of PMLLD phase noise on error vector magnitude (EVM) is also observed and a complete theory and experimental survey on using non-coherent down-conversion (envelope detector) to reduce error of system caused by phase instability of PMLLD is provided. The performance of envelope detector to down-convert the signal with OOK modulation in this communication system is observed using eye diagram and quality factor (Q factor) measurement. [ABSTRACT FROM PUBLISHER]

An on/off keying receiver has been designed in 90 nm CMOS for low-power event-driven applications. Thanks to the synchronized-switching technique and power-efficient RF gain stages, this receiver achieves -86 dBm sensitivity (10^-3 bit error rate) at 10 kbps while consuming 123 µW from a 1 V supply. The receiver is highly scalable in data rates from 1 kbps at 64 µW to 100 kbps at 146 µW power consumption. The center frequency of the receiver can be also programmed from 780 to 950 MHz, covering different sub-GHz bands worldwide. The receiver is fully integrated, although an external SAW filter can be added for better selectivity. [ABSTRACT FROM PUBLISHER]

This paper presents a method for two-way ultrasonic communication and power delivery through thick metallic enclosures without physical penetration. Acousticelectric channels are implemented using a pair of coaxially aligned piezoelectric transducers having 25.4 mm diameters and 1 MHz nominal resonant frequencies, mounted on steel walls having lengths in the range of 57.15 to 304.8 mm. A protocol is described which uses ultrasonic waves to achieve simultaneous bidirectional communication through the metallic enclosures. It is shown that such channels are very frequency selective, and a carrier frequency selection and tracking algorithm is presented to choose a frequency of operation at which both adequate power delivery and reliable full-duplex communication are achieved. Using this algorithm, sufficient power is harvested to allow for the continuous operation of internal electronics which require an aggregate of less than 100 mW. Reliable communication of sensor data is achieved at rates in excess of 30 kbps. [ABSTRACT FROM AUTHOR]

An ultra-low-power RF envelope-detection radio has been designed for low-power short-range wireless applications. It introduces an interference rejection technique that improves the in-band selectivity by 24.5 dB. The transmitter adopts the power-efficient direct-modulation architecture, and the receiver maintains the simplicity and low power consumption of envelope detection receivers. In the 915 MHz ISM band at 10 kbps the transmitter output level reaches -3 dBm with 33.9% global efficiency, while the receiver achieves -83 dBm sensitivity with 121 \muW power consumption. The Tx and Rx implemented in 90 nm CMOS technology occupy 0.71 and 1.27 mm^2, respectively. [ABSTRACT FROM PUBLISHER]

Magnitude detection, such as envelope detection or RMS estimation, is needed for many low-power signal-analysis applications. In such applications, the temporal accuracy of the magnitude detector is as important as its amplitude accuracy. We present a low-power audio-frequency magnitude detector that simultaneously achieves both high temporal accuracy and high amplitude accuracy. This performance is achieved by rectifying the signal with a high-ripple peak detector and then averaging this rectified signal with an adaptive-time-constant filter. The time constant of this filter decreases with increasing amplitude, enabling the filter to quickly respond on a short time scale to transients, while steady-state ripple is averaged on a longer time scale. The circuit has been fabricated in a 0.18 \mum CMOS process and consumes only 1.1 nW–1.08 \muW when tuned for operation from 20 Hz–20 kHz. It exhibits a dynamic range of 70 dB across typical speech frequencies. [ABSTRACT FROM AUTHOR]

A regenerative frequency-modulated ultra-wideband (FM-UWB) receiver for low data rate (<100 kbits/s) and short-distance (<10 m) reception in the 4–5-GHz band, consisting of a 35-dB gain preamplifier, envelope detector/demodulator, IF amplifier, and 50-\Omega test buffer is described. The tunable (3.8–5.1 GHz) receiver front-end operates on a 50-MHz sub-band that is selected, amplified, and transformed from FM to amplitude modulated by a regenerative preamplifier. Energy efficiency of the regenerative FM-UWB receiver compared to previously published FM-UWB implementations is improved by a factor of 8, to 22 nJ/bit. Measured receiver sensitivity is -84 dBm at 100-kbits/s data rate (\10^- 3 bit-error rate). Implemented in 65-nm bulk CMOS, the 0.3 mm^2 test chip consumes 2.2 mW (excluding test buffer) from a 1-V supply. [ABSTRACT FROM AUTHOR]

An energy-efficient 920 MHz FSK transceiver for wireless body sensor network (BSN) applications is implemented in 0.18 \mu\ m CMOS technology with 0.7 V supply. A transceiver architecture based on injection-locked frequency divider (ILFD) is proposed for the low energy consumption. In the receiver, the ILFD in the signal path converts the received FSK signal to amplitude-modulated signal which is applied to the next envelope detector. In the transmitter, the ILFD is used as digitally-controlled oscillator (DCO) which directly modulates the FSK signal with digital data. The DCO replaces the frequency synthesizer to eliminate the crystal oscillator (XO), which leads to reduce power consumption and cost. The transceiver can detect whether injection locking occurs or not, and calibrates the frequency drift of DCO over temperature variation thanks to ILFD based architecture. The receiver and transmitter consume 420 \mu\ W and 700 \mu\ W, respectively, at -10 dBm output power with a data rate of 5 Mb/s, corresponding to energy consumption of 84 pJ per received bit and 140 pJ per transmitted bit. [ABSTRACT FROM AUTHOR]