This paper firstly introduces the importance of temperature control in concrete measurement, then a passive radio frequency identification (RFID) sensor tag embedded for concrete temperature monitoring is presented. In order to reduce the influences of concrete electromagnetic parameters during the drying process, a T-type antenna is proposed to measure the concrete temperature at the required depth. The proposed RFID sensor tag is based on the EPC generation-2 ultra-high frequency (UHF) communication protocol and operates in passive mode. The temperature sensor can convert the sensor signals to corresponding digital signals without an external reference clock due to the adoption of phase-locked loop (PLL)-based architecture. Laboratory experimentation and on-site testing demonstrate that our sensor tag embedded in concrete can provide reliable communication performance in passive mode. The maximum communicating distance between reader and tag is 7 m at the operating frequency of 915 MHz and the tested results show high consistency with the results tested by a thermocouple.
A novel proportional series combining transformer using for power amplifier (PA) is presented. Compared with balanced series combining structures, the high efficiency range is extended by sophisticated power adjusting and impedance tuning. As a proof-of-concept, a 2.5 V dual-channel PA with the proposed transformer was implemented in standard 0.18-µm CMOS process. The fabricated PA achieved a saturated output power (P sat ) of 28 dBm and a maximum linear output power (P 1-dB ) of 26.8 dBm with the power added efficiency (PAE) of 33.5% and 31%, respectively. With power mode control, the high efficiency range exceeded 8.2 dB. The PA satisfied EVM requirements of LTE 2.3 GHz 20 MHz/64-QAM signal and WLAN 802.11g signal, respectively. Keywords: power amplifier, transformer, power combiner, proportional, power mode control Classification: Integrated circuits
In this work, a low cost Bluetooth Low Energy (BLE) transceiver for wireless sensor network (WSN) applications, with a receiver (RX) matching network reusing power amplifier (PA) load inductor, is presented. In order to decrease the die area, only two inductors were used in this work. Besides the one used in the voltage control oscillator (VCO), the PA load inductor was reused as the RX impedance matching component in the front-end. Proper controls have been applied to achieve high transmitter (TX) input impedance when the transceiver is in the receiving mode, and vice versa. This allows the TRX-switch/matching network integration without significant performance degradation. The RX adopted a low-IF structure and integrated a single-ended low noise amplifier (LNA), a current bleeding mixer, a 4th complex filter and a delta-sigma continuous time (CT) analog-to-digital converter (ADC). The TX employed a two-point PLL-based architecture with a non-linear PA. The RX achieved a sensitivity of −93 dBm and consumes 9.7 mW, while the TX achieved a 2.97% error vector magnitude (EVM) with 9.4 mW at 0 dBm output power. This design was fabricated in a 0.11 μm complementary metal oxide semiconductor (CMOS) technology and the front-end circuit only occupies 0.24 mm2. The measurement results verify the effectiveness and applicability of the proposed BLE transceiver for WSN applications.
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