This study introduces a wideband LNTA-based receiver employing full current mode (FCM) signal transmission, leveraging a broadband and highly linear current-mode analog baseband (CMAB). The CMAB module comprises a shunt feedback low pass filter and a programmable gain amplifier (PGA) with wide bandwidth, utilizing a regulated CG current mirror design, enriched by gm-boosting methodology and positive feedback capacitance reutilization through an identical boost amplifier. Fabricated in 12 nm FinFET CMOS process, the FCM receiver attains notable characteristics including a baseband bandwidth of 1 GHz, a conversion gain of 30 dB, a noise figure of 5.2 dB, and an OIP3 of 14.6 dBm, while operating with a low supply voltage of merely 0.9 V. Simulation results validate the efficacy of this FCM receiver for wideband communication, effectively addressing the linearity constraints associated with low supply voltages and maximizing the advantages of FinFET technology in current-mode signal transmission. The total layout area is 0.484 mm2.

Significance Anthropogenic greenhouse gas emissions represented by carbon dioxide and methane are an important driving force of global warming in the last century. The key to controlling global warming is to control greenhouse gas emissions. Carbon dioxide is an important greenhouse gas. Research and development of scientific carbon dioxide emission monitoring technology and scientific identification of regional carbon dioxide emission and absorption are of great significance to serving our country's carbon emission policies at different stages. Progress Traditional inventory methods calculate the total carbon emissions by counting the energy consumed by each emission source. Since statistics and emission factors cannot be updated quickly, it is difficult for these methods to capture the dynamic changes in emission sources. Flux data based on concentration measurement is updated frequently, and the measurement data is objective, which can provide a more accurate basis for greenhouse gas emissions and traceability. In recent decades, various methods have been proposed to measure fluxes based on concentration measurement. The measurement methods for the terrestrial biosphere flux include the chamber method, micrometeorology method, equilibrium boundary layer concepts, and inverse system for space-borne platforms. The measurement methods for the point sources flux contain the inverse diffusion technology represented by the Gaussian plume model, source pixel method, cross-sectional flux method, integrated mass enhancement method, Gaussian vector integral method, and horizontal net flux measurement method. The ground-based in-situ measurement technology represented by the flux tower features high measurement accuracy and strong time continuity and plays a vital role in the flux detection of forests, farmland, and other earth ecosystems. However, since the measurement area of the flux tower usually does not exceed 1 km(2), it is difficult to quantitatively understand the sources and sinks of greenhouse gases on a global scale due to the sparseness of the sites and limited representation distance. Satellite remote sensing data can obtain the global spatial distribution and changes of greenhouse gases with fast inversion speed, which can make up for the shortage of ground base stations. At present, satellite remote sensing can detect greenhouse gas emissions from the earth's ecosystems and point sources. Many countries and teams have inverted the greenhouse gas fluxes of global ecosystems based on satellite remote sensing. In 2021, the Chinese Institute estimated the global CO2 flux distribution based on the TanSat satellite, and the results are in good agreement with other satellites such as Japan's GOSAT and the US's OCO-2. There are also a number of studies that capture CO2 fluxes from terrestrial power plants through satellite measurements. However, satellite remote sensing still has many limitations in accuracy, resolution, and data coverage. The atmospheric chemical transport model can simulate the three-dimensional gas concentration field of the atmosphere, but due to the incomplete transport model and meteorological field, and uncertain initial field and emission sources, the obtained three-dimensional distribution of gas concentration deviates from the actual situation, and it needs to be combined with the actual situation. The observed data is further corrected to improve accuracy. Lidar technology is characterized by long detection distance, high spatial-temporal resolution, and all-day detection. Active remote sensing is an important direction for the development of satellite remote sensing. However, current satellite active remote sensing is mainly based on the path integration technology IPDA and can only obtain the concentration of the entire atmospheric column, thus making it difficult to accurately invert the vertical distribution of point source emissions and affecting the inversion effect of point source emission flux. The ground-based differential absorption lidar DIAL can obtain distance-resolved gas concentration distribution and simultaneously detect atmospheric wind field data with high precision. Although its coverage is not as good as that of satellites, it is wider than that of a single station. It is an effective means for local area gas flux monitoring. Conclusions and Prospects Although the measurement methods of greenhouse gas fluxes are becoming increasingly more abundant, the spatial-temporal resolution, data coverage, and measurement accuracy of the existing methods for the concentration distribution and emission flux of greenhouse gases are still very limited. In the future, greenhouse gas flux measurement technology can be further developed in several directions. Measurement data from satellites, and ground-based and airborne platforms is assimilated to obtain higher-precision three-dimensional distribution of greenhouse gas fluxes, the mechanism of greenhouse gas sources and sinks is analyzed, and natural and anthropogenic carbon emissions are identified. In addition, we develop a greenhouse gas assimilation forecast system and build accurate greenhouse gas source-sink models and inversion models at different scales. As a result, global high spatial-temporal resolution remote sensing is realized through satellite networking to form a global quality-uniform and continuous greenhouse gas observation dataset, and observe the greenhouse gas concentration and spatial-temporal changes of sources and sinks in an all-round way. Collaborative monitoring technologies for greenhouse gases and pollutants are also developed.

This paper presents a wideband and high linearity current mode analog baseband(CMAB) designed for broadband RF receivers. The CMAB consists of a shunt feedback low pass filter and a wideband current amplifier based on cascode current mirror, incorporating gm-boosting technique and positive feedback capacitance reusing the identical boost amplifier, employing in broadband receivers using full current mode signal transmission. Fabricated in 12 nm FinFET CMOS process, the CMAB achieves an impressive 1dB-bandwidth of 1.2 GHz, a current gain of 19.2 dB and an OIP3 of 15.8 dBm, while consuming a low power of 20.3 mW with a supply voltage of only 0.9 V. The simulated performance demonstrates that this analog baseband satisfactorily fulfills the requirements for broadband zero-IF RF receivers, successfully overcoming the linearity limitations associated with low supply voltages and maximizing the benefits of FinFET technology when signal transmission in current mode.

A current-mode two-stage continuous-time pipelined (CTP) ADC for wideband receivers is proposed in this paper, to eliminate power-hungry front-end trans-impedance amplifier (TIA). An improved current mirror with low input impedance and high linearity is used to receive the current input signal and duplicate it to the delay chain and the quantization path of the 3-bit first stage. Then, the residue current is amplified and filtered by an embedded 1st-order TIA and further quantized by the second stage, which is implemented by a VCO-based quantizer to improve ADC energy efficiency and anti-aliasing filtering. Simulation results in a 12 nm FinFET process show that clocked at 4.8 GS/s, the proposed ADC achieves 55.7 dB SNDR for a 600 MHz bandwidth and consumes only 83.4 mW power under supplies of 0.9 V, 1.2 V, and 1.5 V, corresponding to an excellent FoM of 154.3 dB.

Stratospheric aerosols play an important role in the atmospheric chemical and radiative balance. To detect the stratospheric aerosol layer, a 1064 nm lidar with high resolution and large dynamic range is developed using a superconducting nanowire single-photon detector (SNSPD). Measurements are typically performed at 1064 nm for its sensitivity to aerosol, whereas detectors are limited by low efficiency and high dark count rate (DCR). SNSPDs are characterized by high efficiency in the infrared wavelength domain, as well as low noise and dead time, which can significantly enhance the signal quality. However, it is still challenging to build an SNSPD with both large active area and high count rate. To improve the maximal count rate (MCR) so as to avoid saturation in the near range, a 16-pixel interleaved SNSPD array and a multichannel data acquisition system are developed. As a reference, a synchronous system working at 532 nm is applied. In a continuous comparison experiment, backscatter ratio profiles are retrieved with resolutions of 90 m/3 min, and the 1064 nm system shows better performance, which is sensitive to aerosols and immune to the contamination of the ozone absorption and density of molecule change in the lower stratosphere.

High-resolution wind detection plays a crucial role in aviation safety and aerodynamic research. A pulsed coherent Doppler wind lidar (CDWL) with sub-meter/sub-second resolution is demonstrated. The pseudorandom modulation (PRM) method is used to break the link between laser pulse duration and spatial resolution. Benefiting from the flexible pulse duration, the detection accuracy degradation related to the short pulse is largely mitigated. The backscattered spectra and wind profiles measured by the proposed lidar are compared with those obtained by a conventional pulsed CDWL, validating its capacity of radial wind detection within 700 m at 0.9 m/0.5 s resolution. With the help of the proposed high-resolution lidar, the meter-scale perturbation on the wind field from an electric fan is detected in a field experiment.

The monitoring and tracking of urban air pollution is a challenging environmental issue. The approach of synchronous 3-D detection of wind and pollution using a solo coherent Doppler wind lidar (CDWL) is developed and demonstrated. The 3-D distribution of pollutant is depicted by the backscatter coefficient based on signal intensity of CDWL. Then, a high-resolution wind field is derived to track the local air pollution source with its diffusion and to analyze transboundary air pollution episodes. The approach is experimentally implemented in a chemical industry park. Smoke plumes caused by point source pollutions are captured well using plan position indicator (PPI) scanning with low elevation. A typical source of pollution is located, combining the trajectory of the smoke plume and the horizontal wind vector. In addition, transboundary air pollution caused by the transport of dust storms is detected in a vertical profile scanning pattern, which is consistent with the results of national monitoring stations and backward trajectory models. Our present work provides a significant 3-D detection approach to air pollution monitoring with its sources, paths, and heights by using a solo-CDWL system.

A high-spatial-resolution coherent Doppler wind lidar (CDWL) with high modulation efficiency is reported. The pseudo-random phase coding (PRPC) links the spatial resolution to the modulation rate but suffers from the non-rectangular transition caused by the limited bandwidth. With the help of continuous phase modulation (CPM), the abrupt phase switching between successive bit intervals is avoided, thus significantly reducing the bandwidth requirement. By mapping the binary sequence into different transition states rather than phase levels, a 10-fold modulation efficiency improvement is realized. In experiments, the performance of the proposed lidar is compared with lidars in the PRPC method and conventional non-coding method. Continuous radial wind profile measurement of 800 m is demonstrated with spatial and temporal resolution of 1.8 m and 0.5 s, which is the highest spatial resolution realized by a pulsed CDWL to our best knowledge.

Coding technology provides new ideas for spatial resolution enhancement of coherent Doppler wind lidar (CDWL). To improve the performance of coding CDWL for ultra-fine-wind field detection, the crosstalk between neighboring laser pulses is analyzed in theory. The strong backscattered signal from aerosols in near field region will interfere with the weak atmospheric signal, making the accuracy of Doppler shift estimation deteriorate seriously. Considering the formation mechanism of crosstalk, a solution based on adaptive field of view (FOV) modulation is proposed to suppress the crosstalk which is validated by numerical simulation and experiment. Dynamic range of the backscatter intensity is controlled from 10 dB to 2 dB within the distance of 50 m to 300 m, thus the crosstalk is accordingly suppressed.

A micro-pulse lidar system incorporating differential absorption lidar (DIAL) and coherent Doppler wind lidar (CDWL) is proposed and demonstrated. Due to the high signal-to-noise ratio (SNR) of the superconducting nanowire single-photon detector (SNSPD), the DIAL channel achieves high sensitivity in CO2 measurement. Meanwhile, the CDWL channel is used to obtain the horizontal wind field. In the process of the optimization and calibration of the DIAL receiver, specifically, mode scrambling and temperature control of the connecting fiber between the telescope and the SNSPD enhance the stability and robustness of the system. Horizontal scanning of the CO2 concentration and the wind field is carried out in a 6 km range over a scanning span of 60° with a radial resolution of 150 m and 15 s. The results show that the hybrid lidar system captures the spatial distribution of CO2 concentration and the wind field simultaneously. The horizontal net CO2 flux in a radius of 6 km is estimated by integrating the CO2 concentration and the wind transport vector, indicating different characteristics of horizontal net CO2 fluxes in an industrial area, a university campus, and a park. During most of the experiment, CO2 flux remained positive in the industrial area, but balances fell to nearly zero on the campus and in the park. The horizontal net fluxes averaged over 24 h in the three areas are 3.5 × 105 ppm·m2·s−1, 0.7 × 105 ppm·m2·s−1, and 0.1 × 105 ppm·m2·s−1.

Generally, the pulse duration of a coherent Doppler wind lidar (CDWL) is shortened to minimize the spatial resolution at the sacrifice of carrier-to-noise ratio, since the peak power of a laser source is limited by the stimulated Brillouin scattering or other nonlinear optical phenomena. To solve this problem, an all-fiber CDWL incorporating Golay coding is proposed and demonstrated. Given the peak power of the laser pulse, the Golay coding method can improve the measuring precision by improving the pulse repetition frequency of the outgoing laser. In the experiment, the Golay coding implementation is optimized by normalizing the intensity of every single pulse of the outgoing laser with a closed-loop feedback, achieving a spatial resolution of 6 m and a temporal resolution of 2 s with a maximum detection range of 552 m. The wind profile in line of sight and the result derived from another noncoding CDWL show good agreement.

The phase-domain analog-to-digital converter (Ph-ADC) is proved to be more power efficient than traditional amplitude ADCs in wireless receivers . A low power multi-step Ph-ADC for zero intermediate frequency (IF) GFSK receivers as defined in Bluetooth low energy protocol is proposed in this paper. With dedicatedly designed binary code scheme and multi-step operation, the Ph-ADC requires only 52 current elements and one comparator, in contrast to the design in literature using 260 current elements and 8 comparators. Non-idealities due to transconductance errors and offset errors are theoretically analyzed, followed by a design strategy to minimize trip point errors. Simulation results show that the digital intensive Ph-ADC consumes only 7.9 μA current from a 1.8 V supply when implemented in a 180 nm CMOS process. Monte-Carlo simulations show that the maximum trip point error is only 2.3°, which is less than 1/8 least significant bit. When the Ph-ADC is used in a GFSK demodulator, the required IF Eb/N0 is 13.5 dB to achieve a bit error rates of 0.1%.

A 4-bit 4Msps successive approximation (SAR) phase-domain analog-to-digital converter (Ph-ADC) for zero intermediate frequency (IF) Bluetooth low energy (BLE) receivers is proposed. With the SAR operation, the Ph-ADC requires only 52 current elements and 1 comparator, in contrast to the conventional design which needs 260 current elements and 8 comparators. Simulation results show that the digital intensive Ph-ADC consumes only 7.9μA current from a 1.8V supply when implemented in a 180nm CMOS process.

A compact wearable smart sensor for the application of wireless body sound monitoring is presented. It supports several kinds of body sound monitoring and has been measured with heart sound as an example. With the sensor, a wireless body sound monitoring system can be realized, which enables us to "build a hospital in our pocket". In order to achieve a small form factor, a dedicated highly integrated chipset has been designed for the wearable sensor. The chipset consists of a sensor readout chip for data acquisition and a 400 MHz band transceiver chip for wireless communication. It has been fabricated in CMOS technologies and can provide all the necessary sensor functions with a commercial EEPROM chip. Excluding the matching network, only eight off-chip components are required to fabricate the hardware system of the sensor, which helps to significantly improve integrated level.

A 400-MHz/2.4-GHz combo transceiver (TRX) integrated chip (IC) Supporting simultaneous dual-band communication is designed and fabricated in a 65-nm CMOS technology for compact wireless personal area network applications. The IC is composed of a 3-10 Mb/s quadrature phase shift keying (QPSK)/offset QPSK (OQPSK) TRX working at the 400-500 MHz band, and a 1-3 Mb/s Gaussian frequency shift keying (GFSK)/half sine OQPSK (HS-OQPSK) TRX at the 2.4-2.4835 GHz band for the Bluetooth low energy/IEEE 802.15.4 protocols. The presented combo TRX IC requires one single antenna without any bidirectional RF coupler, to support simultaneous dual-band communication. Two key circuit techniques, namely, the combination biasing technique to suppress the high-order harmonics and the active in-band interference cancellation, are adopted to tackle the crosstalk interference between the two bands during simultaneous dual-band operation. Measurement results show that the in-band interference presented to the 2.4-GHz receiver due to the 400-MHz transmitter is suppressed by 19 dB with the presented design techniques.

A combinational biasing technique is presented for a 400–450 MHz power amplifier (PA). By combining two class AB amplifiers with different conduction angles and optimising the design parameters as well, the 5th and 6th harmonics are greatly suppressed in the PA's output. The designed PA is fabricated in 65 nm CMOS technology. Measurement results show that with the presented technique the 5th and 6th harmonic suppressions can be improved by 13 and 17 dB, respectively, compared with a PA with a fixed conduction angle. The presented PA technique can find its important use in multi-protocol transceivers.

This paper presents a 400MHz energy-efficient transceiver for body area applications. The transmitter employs a FIR-embedded phase modulator to shape signal and suppress unwanted side-lobe energy. It achieves 5.9% EVM value at 10Mb/s data rate. The receiver adopts zero-IF architecture and achieves a sensitivity of -86dBm at 10Mb/s HS-OQPSK modulation. Fabricated in 65nm CMOS process, the transmitter and the receiver consumes 2.98mW and 3.1mW from 1V supply, respectively. The TX and RX energy efficiency of the transceiver is 0.3 nJ/bit and 0.31nJ/bit, respectively.

A 10 Mbps OQPSK transceiver working in the 400-450 MHz frequency range is designed for medical telemetry applications requiring wireless communication with both high data rate and low power consumption. An inverter based phase-switching transmitter has been proposed to lower the transmitter power consumption. Moreover, a digital-assisted DC offset calibration (DCOC) technique that combines the PGA-gain-uncorrelated DCOC method and a lookup table is adopted to enable an zero-IF receiver architecture. Fabricated in 65 nm CMOS process, both the transmitter and the receiver consumes approximate to 3 mW from 1 V supply at 10 Mbps data rate. The transceiver energy efficiency is approximate to 0.3 nJ/bit, which outperforms the similar designs in recent literature.