Bluetooth Low Energy Receivers Research Articles

A novel programmable gain control low noise amplifier (PGCLNA) design for automatic gain control loop in BLE applications

Bluetooth low energy (BLE) is a widely used short-range communication protocol and BLE receivers frequently encounter transient high-power RF (radio frequency) signals from antennas, leading to receiver saturation. To address this issue, this work proposes a 2.4 GHz programmable gain control low-noise amplifier (PGCLNA), which is a key element in an automatic gain control (AGC) system for BLE receiver applications. The proposed PGCLNA achieves discrete levels of gain using the g m -boosting technique by splitting the negative feedback. The proposed circuit is simulated in UMC 180 nm technology and the maximum gain achieved is 41.4 dB, with a step decrease of 15 dB in discrete levels. The gain variations do not degrade the performance of S11, which is always less than -16 dB. The noise figure (NF) is always minimum of 5.5 dB and in high gain mode, the minimum value of NF is 1.82 dB. The third-order intercept point (IIP3) is −7.621 dBm in the best circumstances and always remains above −10.69 dBm. These results are achieved by utilising 5.4 mW power at 1.8 V of supply voltage. The circuit occupies an area of 732 μm × 771 μm. The proposed PGCLNA design offers a solution to accommodate a wide range of input signals in BLE receivers, excellent gain control, low noise and robust performance characteristics, making it an essential component in an AGC system for BLE receiver applications.

Self-Localization via Circular Bluetooth 5.1 Antenna Array Receiver

Future telecommunications aim to be ubiquitous and efficient, as widely deployed connectivity will allow for a variety of edge/fog based services. Challenges are numerous, e.g., spectrum overuse, energy efficiency, latency and bandwidth, battery life and computing power of edge devices. Addressing these challenges is key to compose the backbone for the future Internet-of-Things (IoT). Among IoT applications are Indoor Positioning System and indoor Real-Time-Location-Systems systems, which are needed where GPS is unviable. The Bluetooth Low Energy (BLE) 5.1 specification introduced Direction Finding to the protocol, allowing for BLE devices with antenna arrays to derive the Angle-of-Arrival (AoA) of transmissions. Well known algorithms for AoA calculation are computationally demanding, so recent works have addressed this, since the low-cost of BLE devices may provide efficient solutions for indoor localization. In this paper, we present a system topology and algorithms for self-localization where a receiver with an antenna array utilizes the AoAs from fixed battery powered beacons to self-localize, without a centralized system or wall-power infrastructure. We conduct two main experiments using a BLE receiver of our own design. Firstly, we validate the expected behaviour in an anechoic chamber, computing the AoA with an RMSE of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {10.7~ ^{circ}}$ </tex-math></inline-formula> . Secondly, we conduct a test in an outdoor area of 12 by 12 meters using four beacons, and present pre-processing steps prior to computing the AoAs, followed by position estimations achieving a mean absolute error of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {3.6~ \text {m}}$ </tex-math></inline-formula> for 21 map positions, with a minimum as low as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {1.1~ \text {m}}$ </tex-math></inline-formula> .

Accuracy Analysis of the Indoor Location System Based on Bluetooth Low-Energy RSSI Measurements

Systems for determining the position of objects inside buildings have a wide range of applications, such as the surveillance of people’s movements in hospitals, and of goods or mobile robots in warehouse spaces or production halls. Hence, there is a need for the development of methods that could be applied for those purposes. This paper presents the results of research on an experimental system for localizing people being evacuated from a building. The proposed solution was designed as a part of the building evacuation management system. The method used for finding location belongs to the class of proximity-type methods and is based on Received Signal Strength Indicator (RSSI) information of Bluetooth Low-Energy (BLE) devices. The devices used to build the system (BLE receivers) and the evacuee’s wristband (BLE transmitters) are low-budget electronic modules. The paper presents preliminary research and the process of selecting data processing methods, as well as the results of tests of the experimental network created for the evacuation system. The results of measurements and statistical analyses of the properties of the RSSI parameter of the BLE signal transmission between the modules used in the designed system are presented. In addition, the results of RSSI measurements and the analyses of RSSI recorded under varying environmental conditions in the building are presented. The choice of the data processing method and its parameters was made with the use of the determined probabilities of the nearest locator node detection. Finally, the performance of the experimental installation of the evacuee tracking system was tested and the effectiveness of the proximity method was evaluated. The experimental tests aimed to analyze the detection range and the impact of shading. They also allowed for determining the mean error and for estimating the maximum position determination error. It should be emphasized that the proposed position estimation method has a very low computational load, allowing the implementation of an extensive real-time system on a typical personal computer. Although the proposed system should be classified as a coarse positioning system, its features such as low cost, simplicity, flexibility, the use of commonly available components and low requirements for computational load make it attractive. Such a system is directly transferable to other applications in, for example, Industry 4.0.

2.4 GHz Low-power Receiver Front-end Employing I/Q Mixer with Current-reused Quadrature Transconductor for Bluetooth Low Energy Applications

In this paper, a 2.4 GHz Bluetooth low energy (BLE) receiver front-end with a new inphase/quadrature (I/Q) down-conversion active mixer employing a current-reused quadrature transconductor is presented for low-power low-voltage Internet of Things applications. In the proposed I/Q mixer, the current-bleeding circuit, whose main role is to reduce the flicker noise in the switching stage, enhances the overall transconductance and provides quadrature signals with the main quadrature transconductor. Consequently, it improves the conversion gain and noise figure of the mixer without additional power consumption. The proposed BLE receiver front-end consists of a current-reused push-pull low-noise amplifier and an I/Q mixer with a current-reused quadrature transconductor. Simulated in a 65 nm CMOS process, the designed receiver front-end achieves a noise figure of 3.3 dB, conversion gain of 37.6 dB, and input-referred third-order intercept point of -22.73 dBm. It draws a bias current of 1 mA from a nominal supply voltage of 1 V. The active die area is 0.5 mm².

2.4-GHz Low-Power Low-IF Receiver With a Quadrature Local Oscillator Buffer for Bluetooth Low Energy Applications

In this brief, a 2.4-GHz low-power single-quadrature low-IF Bluetooth low energy receiver employing a quadrature local oscillator (LO) buffer is presented for Internet of Things applications. The quadrature LO buffer, which consists of common-source amplifiers with capacitive degeneration, compensating resistors, compensating PMOS transistors and LC tanks, performs quadrature generation and supplies quadrature signals to a single-quadrature mixer, thus eliminating an additional circuitry for quadrature generation in the LO path and saving dc current consumption. The implemented receiver consists of a low-noise amplifier, a G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> -stage, double-balanced current-mode passive mixers, transimpedance amplifiers, an active- RC complex bandpass filter, and the quadrature LO buffer. Fabricated in a 65-nm CMOS process, the implemented receiver achieves a noise figure of 8.16 dB, a conversion gain of 54.5 dB, an image rejection ratio of 32.1 dB, and an input-referred third-order intercept point of -27.5 dBm. It draws a bias current of 2.5 mA from a nominal supply voltage of 0.8 V, and the active die area is 1.65 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

PatternBee: Enabling ZigBee-to-BLE Direct Communication by Offset Resistant Patterns

In Internet of Things (IoT), ZigBee and Bluetooth Low Energy (BLE) are two popular technologies. Their devices often coexist and enabling them to communicate with each other will facilitate our daily lives greatly. In this article, we present PatternBee, a lightweight physical-level cross-technology communication (PHY-level CTC) scheme which enables ZigBee-to-BLE direct communications. In PatternBee, the BLE receiver divides received ZigBee symbols into pieces. We find that some pieces always have a phase shift of 0 no matter how large the sampling offset is. We call these pieces offset resist pieces (ORPs). By identifying the occurrence pattern of these ORPs, we propose a Pattern-based decoding algorithm. With this algorithm, the BLE receiver can decode ZigBee symbols at very low processing complexity, while achieving very high decoding accuracy. Real-world experiments verify the effectiveness and accuracy of PatternBee.

A Performance Evaluation Framework for Direction Finding Using BLE AoA/AoD Receivers

Bluetooth low energy (BLE) has been significantly contributed to the Internet of Things applications due to its advantages, such as low power consumption and scalability. To further expand its applications, BLE has adopted the Angle of Arrival (AoA) and the angle of departure (AoD) to improve the accuracy in direction finding (DF). The AoA/AoD is calculated using the phase difference (PD) between slots in the received BLE data. The PD performance of BLE receiver (RX) in all directions should be evaluated in detail because it directly determines the accuracy of AoA/AoD. In the traditional test method, the reference PD is converted by an antenna array with switches, which is inaccurate due to the conversion errors and path mismatches. Moreover, because of the mechanical rotation of the turntable, the test processing is very time consuming. This article proposes a BLE test waveform generation method that directly includes the reference PD. A commonly used vector signal generator (VSG) is the only required instrument in the evaluation. The compact test setup not only eliminates the requirement of antenna array, switch, turntable, and anechoic chamber but also eliminates the measurement errors caused by these devices. After creating and downloading all BLE test waveforms with reference PD in the range of −180° to 180° by user-defined steps, the PD performance of BLE RX can be quickly evaluated by switching the test waveforms using commands or running them in the sequence mode. Furthermore, three enhanced test cases with automatic test procedures are proposed to evaluate the detailed PD accuracy of BLE RX under the low signal-to-noise ratio (SNR), carrier frequency offset, and modulation frequency deviation environments. Experimental results show that the PD error of the proposed method is 0.19°, and it needs 360 ms to evaluate the PD accuracy of CC2640R2F in all directions in 1° steps.

2.4 GHz BLE Receiver With Power-Efficient Quadrature RF-to-Baseband-Current-Reuse Architecture for Low-Power IoT Applications

In this paper, a 2.4 GHz Bluetooth low energy receiver employing a power-efficient quadrature RF-to-baseband-current-reuse architecture is presented for low-power low-voltage internet of things applications. The proposed quadrature RF-to-baseband-current-reuse RF front-end consists of a low-noise transconductance amplifier, an active-type polyphase filter-based quadrature generator, transimpedance amplifiers, and double-balanced current-mode passive mixers on a single dc current path. An input matching network is used to perform power-constrained simultaneous noise and input power matching and 1/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f$ </tex-math></inline-formula> noise reduction in the RF and baseband domains, respectively. The quadrature RF signals are provided to the single-quadrature mixers through an embedded active-type polyphase filter-based quadrature generator. The implemented Bluetooth low energy receiver is composed of the RF-to-baseband-current-reuse RF front-end, IF amplifiers, two-stage passive- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> polyphase filter, and fifth-order Chebyshev-II <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$G_{m}$ </tex-math></inline-formula> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-C</i> filters. The proposed design was fabricated using a 65-nm CMOS process and characterized primarily in the Bluetooth low energy operating frequency bands. The active die area of the implemented receiver was 0.85 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and the receiver drew a bias current of 1.41 mA from a nominal supply voltage of 0.8 V. The Bluetooth low energy receiver achieved a noise figure of 13.2 dB, conversion gain of 42 dB, image rejection ratio of more than 30 dB, and input-referred third-order intercept point of −25 dBm.

2.4-GHz Bluetooth Low Energy Receiver Employing New Quadrature Low-Noise Amplifier for Low-Power Low-Voltage IoT Applications

In this article, a 2.4-GHz Bluetooth low-energy (BLE) receiver employing a new quadrature low-noise amplifier (LNA) is presented for low-power low-voltage Internet of Things (IoT) applications. The proposed quadrature LNA consists of a common-source (CS) amplifier with inductive degeneration, an active-type poly-phase filter (PPF), and an LC tank. The proposed active-type PPF between the CS amplifier and the LC tank provides quadrature generation, and the CS amplifier determines and optimizes the overall LNA performance parameters. Moreover, the proposed active-type PPF shares the dc bias current with the CS amplifier, thereby eliminating the necessity for additional current consumption. The implemented BLE receiver is composed of the quadrature LNA, a $G_{m}$ -stage, a double-balanced current-mode passive mixer, a transimpedance amplifier, and an active- RC complex bandpass filter. The proposed design was fabricated in a 65-nm CMOS process and mainly characterized in the BLE operating frequency bands. The receiver achieves a noise figure of 8.2 dB, a conversion gain of 49.5 dB, an image rejection ratio of more than 33 dB, and an IIP3 of −25.75 dBm. The active die area of the implemented receiver is 1.16 mm2, and it draws a bias current of 2.7 mA from a nominal supply voltage of 0.8 V.

A 2.4-㎓ Low-power Low-IF Receiver Employing a Quadrature Low-noise Amplifier for Bluetooth Low Energy Applications

In this paper, a low-power low-IF receiver employing a quadrature low-noise amplifier (LNA) is proposed for Bluetooth low energy (BLE) applications. The proposed quadrature LNA, which can provide accurate quadrature signals in the RF path, consists of a common-source amplifier with inductive degeneration and a quadrature generator based on a common-gate amplifier with a single RC network. Therefore, a BLE receiver using the proposed LNA can eliminate quadrature generating circuitry of the LO chain, thereby reducing power consumption. The implemented receiver is composed of the quadrature LNA, single-to-differential double-balanced active mixer, and second-order G<SUB>m-</SUB>C complex filter. Simulated in a 65-nm CMOS process, it achieves a conversion gain, noise figure, and an image rejection ratio of 53.2 dB, 4.81 dB and 38 dB, respectively, and consumes 2.2 mA from a supply voltage of 0.8 V. The die area is 2.24 ㎟.

Indoor Localization System Based on Bluetooth Low Energy for Museum Applications

In the last few years, indoor localization has attracted researchers and commercial developers. Indeed, the availability of systems, techniques and algorithms for localization allows the improvement of existing communication applications and services by adding position information. Some examples can be found in the managing of people and/or robots for internal logistics in very large warehouses (e.g., Amazon warehouses, etc.). In this paper, we study and develop a system allowing the accurate indoor localization of people visiting a museum or any other cultural institution. We assume visitors are equipped with a Bluetooth Low Energy (BLE) device (commonly found in modern smartphones or in a small chipset), periodically transmitting packets, which are received by geolocalized BLE receivers inside the museum area. Collected packets are provided to the locator server to estimate the positions of the visitors inside the museum. The position estimation is based on a feed-forward neural network trained by a measurement campaign in the considered environment and on a non-linear least square algorithm. We also provide a strategy for deploying the BLE receivers in a given area. The performance results obtained from measurements show an achievable position estimate accuracy below 1 m.

Robust Localization for Robot and IoT Using RSSI

Node-localization technology has been supported in the wireless sensor network (WSN) environment. Node localization is based on a few access-point (AP) nodes that comprises positioning information because they are fixed, and a beacon node that comprises unknown positioning information because it is moving. To determine the position of the unknown node, it must use two or three APs that comprise certain positioning information. There are a number of representative range-based methods, including time of arrival (TOA), weighted centroid locating algorithm, received signal strength intensity (RSSI), and time difference of arrival (TDOA) signal, that are received by the receiver. The RSSI method has its advantages. A simple device structure means that the RSSI method is easy to use. Because the structures of previous wireless local area network (LAN) technologies make them compatible with RSSI information, the RSSI method is widely used in the related area of position tracking. In addition, this algorithm has a hardware system that cannot be increased, has the advantage of the miniaturization of the node, and can wear through obstacles. This paper proposes the application of a robust ranging method that can be applied in robots and Internet of Things (IoT) using RSSI, especially in the tracing location of each nursing home patient, where the RSSI method with trilateral technique is used. This paper shows the results of the measured point from the application of the trilateral technique, and it also represents the results of the error distance between the ideal point and the measured point using computer simulation. Finally, this paper presents an estimation of localization using a real experimental device with a BLE (Bluetooth low-energy) transmitter and receiver, and beacon gateway, by applying an RSSI algorithm with the trilateral technique.

A 0.4-V 10.9-$\mu$ W/Pole Third-Order Complex BPF for Low Energy RF Receivers

This paper presents a 0.4-V ultra-low power (ULP) third-order active-RC complex band-pass filter (CxBPF) for Bluetooth low energy receivers prototyped in a 180 nm CMOS process. The ULP is reached by using single-stage inverter-based operational transconductance amplifiers (OTA) instead of two or more stages OTA. The effects of the low voltage gain and resistive loading are reduced by using a process and temperature robust negative transconductor connected to the virtual ground. The ultra-low voltage operation is reached by using only two stacked transistors and PMOS bulk forward bias. The CxBPF operates well down to 0.4V power supply and the experimental results present power dissipation of only $10.9~\mu \text{W}$ /pole, 1 MHz bandwidth centered at 2 MHz, image rejection rate of 34 dB, and 12.7 fJ FoM.

City Marathon Active Timing System Using Bluetooth Low Energy Technology

This study proposes and implements city marathon timing technology using Bluetooth Low-Energy (BLE) communication technology. This study also performs a prevalidation of the athletes’ physiological sensory data that is sent out by the same timing system—the BLE active communication technology. In order to verify the timing and positioning technology, 621 K records of static measurement of the Received Signal Strength Indicator (RSSI) were first collected. The trend of the RSSI between the location and the BLE Receiver when the runners carried a BLE Tag was analyzed. Then, the difference between the runners’ passing timestamp and the runners’ actual passing time when the runners carried a BLE Tag and ran past the BLE Receivers was dynamically recorded and analyzed. Additionally, the timing sensing rate when multiple runners ran past the BLE Receivers was verified. In order to confirm the accuracy of the time synchronization in the remote timing device, the timing error, synced by the Network Time Protocol (NTP), was analyzed. A global positioning system (GPS) signal was used to enhance the time synchronization’s accuracy. Additionally, the timing devices were separated by 15 km, and it was verified that they remained within the timing error range of 1 ms. The BLE communication technology has at least one more battery requirement than traditional passive radio frequency identification (RFID) timing devices. Therefore, the experiment also verified that the BLE Tag of this system can continue to operate for at least 48 h under normal conditions. Based on the above experimental results, it is estimated that the system can provide a timing error of under ±156 ms for each athlete. The system can also meet the scale of the biggest international city marathon event.

A Compiled 9-bit 20-MS/s 3.5-fJ/conv.step SAR ADC in 28-nm FDSOI for Bluetooth Low Energy Receivers

This paper presents a low-power 9-bit compiled successive-approximation register (SAR) analog-to-digital converter (ADC) for Bluetooth low energy receivers. The ADC is compiled from a SPICE netlist, a technology rule file, and an object definition file into a design rule check and layout versus schematic clean layout and schematic in 28-nm FDSOI. The compiled SAR ADC reduces the design time necessary to port to a new technology, and to demonstrate technology porting the same SAR ADC architecture is compiled in 28-nm FDSOI with Input/Output (IO) transistors. This paper also includes a comparator clock generation loop that uses the bottom plate of the capacitive digital-to-analog converter. The proposed compiled core transistor SAR ADC achieves the state-of-the-art Figure of Merit (FoM) of 2.7 fJ/conv.step at 2 MS/s, and 3.5 fJ/conv.step at 20 MS/s with an area of 0.00312 mm2.

A novel motion monitoring system for activities of daily living

Capability to perform activities of daily living (ADLs) is a major factor in quality of life (QOL). While it can be difficult for the elderly, disabled, or patients with chronic diseases to deal with ADLs, they need to spend a great deal of money on healthcare and assistive technologies to keep a good QOL. The situation can be improved if a real-time ADLs monitoring and recognition system is available to provide health information to physicians, pharmacists, or caregivers to offer timely diagnosis, prescription, or emergency reaction. We have developed a wireless wearable motion monitoring system that is suitable for monitoring ADLs involving limbs. The system consists of six Bluetooth low energy (BLE) transponders that are small and light enough to be mounted on all limbs. Each transponder, called SensorTag (by Texas Instruments), is equipped with a tri-axial accelerometer, a tri-axial magnetometer, and a tri-axial gyroscope for motion monitoring. Each SensorTag can be linked to a smartphone for long-term outdoor monitoring. A graphic user interface is created to acquire signals from BLE receivers, display the sig-nals in real-time, process data, and store for off-line analysis. This system was tested in three scenarios, and signals were analyzed off-line using a quaternion-based motion recon-struction algorithm. First, a SensorTag was examined against a marker-based motion capture system in a linear motion test. Second, a SensorTag was worn on a subject’s wrist to monitor food-intake trajectory. Finally, six SensorTags were worn on wrist, knee, and ankle joints of left and right hands to monitor gait on a straight path. Results showed various er-ror rates in different scenarios, however, the error rates are within an acceptable range, and more importantly the patterns of the motions are reproducible.