Passive and Semi-Passive Wireless Temperature and Humidity Sensors Based on EPC Generation-2 UHF Protocol

A 40 nW CMOS-Based Temperature Sensor with Calibration Free Inaccuracy within ±0.6 °C

“…where I DO is the saturation diode saturation current, η is the subthreshold slope-factor and V T is the thermal voltage. Using Equations (5) and (6) in Equation 4, and substituting the resultant into Equation 3gives the expression of I re f as follows:…”

“…These temperature sensing modules sense the temperature either by using BJT (Bipolar Junction transistor)-based or by using MOSFET (Metal Oxide Semiconductor Field-effect transistor)-based circuit arrangements. The BJT-based temperature sensors are widely accepted due to their accurate temperature sensing ability that can be below ±1 • C [4][5][6][7]. For all MOSFET-based implementations, a temperature accuracy less than ±2 • C has been achieved [8][9][10][11].…”

Architecture Characteristics and Technical Trends of UHF RFID Temperature Sensor Chip

“…Regarding the integration technology of RFID and TS, many works have proposed different technical architectures [7,9,28,48]. In general, RFID-TSC mainly consists of two parts: antenna and chip.…”

“…Therefore, RFID can be more easily integrated into sensor networks and other IoT applications. As shown in Figure 2, the serial peripheral interface (SPI) [33] bus and the interintegrated circuit (I 2 C) bus [28,51,60,61] are common interfaces. Because the SPI bus occupies more pins than the I 2 C bus, it limits the expansion of the RFID-TSC function.…”

“…Because different brands of UHF RFID-TSC products adopt different protocols and standards, Table 2 compares and analyzes the UHF RFID-TSC products on the market from the aspects of RF working frequency band, working mode, air interface protocol, temperature range/error, and communication distance. As shown in Table 2, the maximum communication distance of the products in the air is 10m [37], the maximum write distance under 4W(EIRP) is 6m [28], the temperature range is -40∼85 ∘ C [9,37], and the minimum error is 0.1 ∘ C [37]. It can be seen that the existing products can basically meet the needs of different application scenarios, such as food quality control temperature measurement range requirements -10∼30 ∘ C [6,8] and animal or human body temperature monitoring requirements at about 37 ∘ C [7].…”