This article presents a multi-receiver cross-correlation technique for (B)FSK receivers, targeting wireless sensor network applications. Here, multiple receiver outputs are pair-wise cross-correlated ...and the correlated output samples are averaged to lower the noise floor at the receiver output. Compared to a two-receiver cross-correlation, multi-receiver cross-correlation generates more cross-correlated output samples in a given time. Hence it requires a shorter measurement time for a desired noise floor reduction and facilitates a higher data rate for (B)FSK operation. Compared to a single receiver, it improves the linearity and the harmonic interferer tolerance using passive splitters and different LO frequencies in the receiver paths respectively. These theoretical insights are verified with measurements for the first time using a 2- and 3-receiver cross-correlation in a BFSK receiver. Operating at 1GHz and with a data rate of 200kbps, the demonstrator, using sub-mW mixer-first receiver front-ends for power efficiency, achieves −102dBm sensitivity and >40 dB rejection for both narrow and wideband harmonic interferers without any RF filters.
A low-power interferer-robust mixer-first receiver front end that uses a novel capacitive stacking technique in a bottom-plate N-path filter/mixer is proposed. Capacitive stacking is achieved by ...reading out the voltage from the bottom plate of N-path capacitors instead of their top plate, which provides a 2x voltage gain after downconversion. A step-up transformer is used to improve the out-of-band (OOB) linearity performance of small switches in the N-path mixer, thereby reducing the power consumption of switch drivers. This article explains the concept of implicit capacitive stacking and analyzes its transfer characteristics. A prototype chip, fabricated in 22-nm fully depleted silicon on insulator (FDSOI) technology, achieves a voltage gain of 13 dB and OOB IIP3/IIP2 of +25+66 dBm with 5-dB noise figure while consuming only 600 μW of power at fLO=1 GHz. Thanks to the transformer, the prototype can operate in the input frequency range of 0.6-1.2 GHz with more than 10-dB voltage gain and 5-9-dB noise figure. Thus, it opens up the possibility of low-power software-defined radios.
In this article, we present a passive mixer-first receiver front end providing a low-power integrated solution for high interference robustness in radios targeting Internet-of-Things (IoT) ...applications. The receiver front end employs a novel N-path filter/mixer, a linear baseband amplifier, and a step-up transformer to realize sub-6-dB NF and >20-dBm OB-IIP3 concurrently. The proposed N-path filter/mixer exploits an implicit capacitive stacking principle to achieve passive voltage gain of 3 during down-conversion and high out-of-band linearity simultaneously while using at least 2<inline-formula> <tex-math notation="LaTeX">\times </tex-math></inline-formula> less total capacitance for the same RF bandwidth compared to a conventional switch-capacitor N-path filter. Fabricated in 22-nm complementary metal-oxide-semiconductor (CMOS) fully depleted silicon on insulator (FDSOI), the receiver prototype-including a 2:6 transformer-occupies only 0.2 mm 2 of active area. Operating in the frequency range of 1.8-2.8 GHz, the front end provides a 45-47-dB conversion gain and a baseband bandwidth of 2 MHz. Due to passive voltage gain in the filter/mixer and transformer, the implemented front end consumes only 1.7-2.5 mW of power to achieve < 6-dB NF, ~24/60/1 dBm out-of-band IIP3/IIP2/B1dB, respectively.
This paper presents an energy-/area-efficient digitally controlled oscillator (DCO)-based phase-tracking Receiver for Internet-of-Things (IoT) applications. The RX leverages the constant-envelope ...nature of frequency shift keying modulation adopted in many IoT protocols, e.g., IEEE802.15.4 and Bluetooth low energy (BLE), to enhance the energy efficiency and to reduce the chip area. The proposed RX, with the DCO acting as a local oscillator (LO) and binary frequency feedback, promotes low-power and low-voltage circuit design, while a data-aided carrier-frequency tracking ensures the received carrier stability without a power-/area-hungry phase-locked loop (PLL). The RX avoids a compromise between a power-hungry I/Q LO generation and the image rejection in traditional RXs. An equivalent mathematical model is further presented, which helps to analyze and optimize the frequency response of the proposed RX. Fabricated in 40-nm CMOS, the RX consumes 1.55 mW from a 0.85-V supply and has a -87-dBm sensitivity at 2 Mb/s, which leads to a 0.77-nJ/b energy efficiency and 178-dB RX sensitivity FoM.
This paper presents a sub-mW mixer-first RF front-end that exploits a novel capacitive stacking technique in an altered bottom-plate N-path filter/mixer to achieve passive voltage gain and ...high-linearity at low noise figure. Capacitive stacking is realized implicitly by reading out the voltage from the bottom-plate of N-path capacitors instead of their top-plate, which provides a 2x gain at the read-out capacitors. Additional passive voltage gain is achieved using impedance upconversion while improving the out-of-band linearity performance of small switches. With no other active circuitry, only clock generation circuits determine the total power consumption of this RF front-end. A prototype is fabricated in GF22 nm FDSOI technology. Operating at f LO = 1 GHz, the prototype achieves a voltage gain of 13 dB, 5 dB Noise Figure and +25/+66 dBm Out-of-band IIP3/IIP2 at 160 MHz offset while consuming only 600 μW of power from a 0.8 V supply.
We propose an ultra-low-power (ULP) and low-voltage phase-tracking RX for IoT applications. Several popular standards are defined for IoT, e.g., IEEE802.15.4 and Bluetooth Low Energy (BLE), where ...they envision massive numbers of interconnected sensors; however, the cost of replacing/recharging batteries can become an impediment to their massive deployment. In this work, aggressively improving the transceiver energy efficiency, lowering the supply, and simultaneously reducing the cost (die area) of the design are our primary goals. Hence, we propose a digitally-controlled oscillator (DCO)-based phase-tracking RX, which efficiently combines frequency downconversion, channel selection, carrier generation and signal demodulation, all of which lead to an ultra-low-power, low-voltage and low-cost RX.
Recent advancements in composites involve integrating natural fibers into polymer matrices as a reinforcement or filler. This approach offers several benefits, including eco-friendliness, abundant ...natural materials, exceptional strength, cost-effectiveness, and simple extraction methods. Substituting synthetic materials with natural ones has environmental advantages, as some synthetics release toxins at high temperatures. Natural materials reduce the risk of toxic emissions, fostering a safer environment. Thus, our research centers on experimentally characterizing Fishtail Palm Leaf Stalk Fiber (FPLSF) through methods like Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), single fiber tensile test, and scanning electron microscope (SEM) analysis. These techniques unveil insights into composition, structure, thermal properties, strength, and morphology. Results highlight FPLSF’s attributes: 63.67% cellulose, 1473 kg/m³ density, 380.85 µm diameter, 31.37% crystallinity index, 249.23 MPa tensile strength, and 326°C thermal stability. In addition, the sound absorption properties such as sound absorption coefficient (SAC) and noise reduction coefficient (NRC) are found to be 0.34 and 0.39, respectively. FPLSF’s properties suggest its potential as an alternative reinforcement in composite manufacturing.
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