Amplitude Shift Keying Demodulator Research Articles

An Energy-Efficient ASK Demodulator Robust to Power-Carrier-Interference for Inductive Power and Data Telemetry.

Wireless power and datatelemetry based on amplitude-shift keying (ASK) modulation over dual inductive links has been widely adopted in biomedical implants. Due to the mutual inductance between the power and data links, the large power-carrier-interference (PCI) will inevitably cause low signal-to-interference ratio (SIR) of the received signal, thereby increasing the bit-error-rate (BER) of the ASK demodulation. In this paper, an innovative high energy-efficient ASK demodulator robust to PCI has been proposed. Thanks to the proposed sampling-and-subtraction (SAS) architecture, the demodulator is capable of withstanding PCI with an amplitude up to 2.5 times as the data carrier without the need for any high-order filters. The prototype has been implemented with 180 nm standard CMOS process, occupying a core area of 0.51 mm 2. The experimental results show that with 1 Mbps data rate and 13.56 MHz carrier frequency, the typical BER is less than 1.3×10 -3, while the energy efficiency is 280 pJ/bit, showing 7.5× improvement compared to the prior works. The energy-efficient robustness to PCI demonstrates the potential of the technique to be applied to retina prostheses as well as various kinds of ultra-low-power implantable biomedical devices.

Design and implementation of reconfigurable ASK and FSK modulation and demodulation algorithm on FPGA (Field Programmable Gate Array)

Our modern world is completely driven by our ability to communicate all over the world with great precision, accuracy, and the least amount of time possible. Communication systems are used vastly in our worlds such as radar, aerospace, naval/maritime communication, underwater communication, mobile communication, or even in outer space such as satellite communication or space missions. Different communication system needs different types of modulation techniques. Design and implementation of reconfigurable modulators on cyclone-II FPGA (Field-programmable gate array) are proposed in this paper, wherein the type of modulations and demodulation can be dynamically reconfigured on the fly based on the requirement at any particular instance. The demodulator is intelligent enough to demodulate any modulated signal. FPGA or Field Programmable Gate Array is a computing device that can be programmed like CPU (Central Processing Unit) but fasted than CPU in parallel processing and DSP (Digital Signal Processing) related tasks. Consisting method of FPGA-based modulation does not support multiple modulation techniques at the same time and is not fast as they used Simulink-based simulation. This study has proposed FPGA based alternative to that, which can embody all the modulation techniques at once, making it way more versatile, cost-effective, and easy to use and test. The process begins with designing an algorithm. Then this algorithm has to be simulated. The algorithm is designed for both modulation and demodulation. In the modulation part, it is just simple logic to create different phrases and different frequencies of sinusoidal waves. But in demodulation, based on the frequency it can detect ASK (Amplitude Shift Keying) or FSK (Frequency Shift Keying) signal all by itself. Depending on the period of the signal, the algorithm can decide whether it is an ASK or FSK signal. After deciding it is an ASK of FSK signal, it starts to demodulate the signal. The outcome is, this FPGA-based modulator and demodulator are cheap, easy to configure, and can demodulate any type of demodulated signal. As it is reconfigurable, it's easy to deploy in any situation.

A Wireless Power and Data Transfer Receiver Achieving 75.4% Effective Power Conversion Efficiency and Supporting 0.1% Modulation Depth for ASK Demodulation

This article presents a 13.56-MHz wireless power and data transfer receiver for implantable biomedical devices. To avoid the efficiency reduction of energy harvesting caused by the large amplitude modulation (AM) modulation depth (MD), and maintain low-power consumption for data receiving, an envelope-detector-based receiver with shifted limiters is designed for signal demodulation. The detectable MD is as low as 0.1%. Moreover, a dynamic impedance matching controller is proposed to adjust the input impedance of the rectifier automatically and thus optimize the power conversion efficiency (PCE). By using these techniques, when keeping the bit error rate (BER) of the proposed receiver to 10−3 for 100-kb/s data rate in the wireless amplitude shift keying (ASK) data receiver, the effective PCE of the corresponding wireless power receiver can be up to 75.4%.

An Ultra-low-power Fully-differential ASK Demodulator with 12.5 pJ/bit FOM for Implantable Biomedical Applications

In this paper, we propose a fully-differential amplitude-shift-keying (ASK) demodulator for suppressing the effect of undesired common mode variations on the received data, In addition, the ASK demodulator is robust against power supply ripples. The proposed demodulator consists of a fully-differential envelope detector (ED), programmable gain amplifier (PGA) and a differential comparator. The ED and PGA operate in the sub-threshold region and the inverter based comparator consumes only dynamic current, making it highly power-efficient. The proposed system is implemented in a 0.18 μm CMOS process and consumes 2.5 μA from a 1 V power supply. At a data rate of 200 kbps, this leads to an FOM of 12.5 pJ/bit.

Wireless energy‐harvesting circuit and system with error‐correction ASK demodulator for body sensor network with ultra‐high‐frequency RFID healthcare system

This study presents a low-power energy-harvesting circuit with error-correction demodulation for body sensor networks with radio-frequency identification (RFID) systems. The proposed circuit adopts a new structure that facilitates the demodulation of amplitude-shift-keying (ASK) signals, and it includes a power unit consisting of a wake-up circuit and a power-on-reset control circuit. The wireless bio-signal acquisition system and the digital processor are implemented on a field-programmable gate array to demonstrate the proposed RFID tag. The proposed energy-harvesting circuit can substantially decrease the capacitance used by the demodulator circuit and the wake-up circuit to as low as 14 pF. Moreover, a detection circuit and a correcting circuit are utilised to reduce the bit error rate of decoding. The wireless bio-signal acquisition scenario is also set up and the communication signal between reader and tag is measured to demonstrate the system that can be employed in body sensor network with the healthcare system. The chip was implemented in complementary metal-oxide-semiconductor 0.18 μm technology. The sensitivity of this work is - 13 dBm. The pulse width error can be reduced to <;1% by the error-correction demodulator to fit the EPC Gen-2 standard.

A 34-pJ/bit Area-Efficient ASK Demodulator Based on Switching-Mode Signal Shaping

This brief presents a new amplitude shift-keying (ASK) demodulator for biomedical implants based on waveform shaping on detected envelope signals. The proposed demodulator incorporates a novel switching-mode signal shaper, which can operate with much lower power consumption. The design does not require any comparator or Schmitt trigger and operates with a very low number of elements; thus, the silicon area is highly saved. With a carrier frequency of 5 MHz and a data rate of 500 kb/s, the proposed ASK demodulator can extract data with modulation indexes down to 5%, whereas the bit-error rate can be as low as 10−5 depending on the input signal-to-noise ratio. Using a 0.18- $\mu\text{m}$ CMOS process, the demodulator occupies a die size of 920 $\mu\text{m}^{2}$ . The average power consumption of the proposed demodulator is only 17 $\mu\text{W}$ by physical measurement on silicon.

An Inductively Coupled Power and Data Link with Self-referenced ASK Demodulator and Wide-range LDO for Bio-implantable Devices

This paper describes a neural stimulation system that employs an inductive coupling link to transfer power and data wirelessly. For the reliable data and power delivery, a self–referenced amplitudeshift keying (ASK) demodulator and a wide-range voltage regulator are suggested and implemented in the proposed stimulator system. The prototype fabricated in 0.35 um BCD process successfully transferred 1.2 Kbps data bi-directionally while supplying 4.5 mW power to internal MCU and stimulation block.

Threshold voltage-level change in ASK demodulator related to RF input signal amplitude for the ultra-high frequency RFID passive tag

In this paper, an amplitude shift keying (ASK) demodulator with 100% modulation depth is proposed. In order to achieve the higher power and wider reading range the designed ASK demodulator works in the ultra-high frequency. In this design, the average detector and voltage divider are used in order to define the appropriate threshold voltage level for the radio frequency input signal which leads to the accurate data detecting even at long distances between the tag and reader. In addition, for diminishing the power dissipation of the proposed demodulator, an enable input is used in the buffer and comparator. This circuit is simulated in 0.18 μm complementary metal–oxide–semiconductor (CMOS) technology with Cadence software. Its power dissipation and chip area are 3.9 nW and 0.0025 mm2, respectively.

Differentiating ASK Demodulator for Contactless Smart Cards Supporting VHBR

This brief proposes an amplitude shift keying (ASK) demodulator that uses switched-capacitor differentiators to make it compliant with the very high bit rate amendment to the ISO/IEC 14443 standard for contactless smart card applications. These differentiators detect transitions in modulated ASK signals with a carrier frequency of 13.56 MHz at data rates up to 6.78 Mb/s. The demodulator has been implemented in 0.18 μm CMOS technology. The total power consumption is under 350 μW. Measured results confirm correct operation, and it is further shown that this differentiating scheme allows the modulation index to be reduced to 2.56%.

DEVELOPMENT OF BIO-IMPLANTED MICRO-SYSTEM WITH SELF-RECOVERY ASK DEMODULATOR FOR TRANSCUTANEOUS APPLICATIONS

This paper deals with the development of bio-implanted micro-system with low-power and high data rate based on amplitude shift keying (ASK) modulation technique to stimulate nerves and muscles. The modified system is operated by a low-frequency band 13.56 MHz according to the industrial-scientific-medical (ISM) bands to avoid the biological tissue damage. The data rate on the demodulator side is from 1 Mb/s and up to 1.5 Mb/s depending of generating binary signal (T BIT = 1 μs or 0.5 μs) with modulation index of 13% and modulation rate 7.3%, 9% and 11%, respectively. The proposed inductive coupling link achieves 73% of link efficiency. The modified rectifier with self-threshold voltage cancellation techniques and voltage regulator without thermal protection circuit and without passive elements occupies small area that is modified to generate adequate and stable DC voltages of 1.8 V. A new ASK demodulator structure based on two comparators is developed to extract a synchronized demodulated signal with minimum error. Thereby no need for clock recovery circuit and delay-locked loops (DLL) circuits for data synchronization at 1 Mb/s and 1.250 Mb/s of speed. The system designed using OrCAD Pspice 16.2 is based on 0.35 μm technologies.

EFFICIENT DATA AND POWER TRANSFER FOR BIO-IMPLANTED DEVICES BASED ON ASK MODULATION TECHNIQUES

This paper presents a fully integrated system for implanted micro-system devices with efficient power and data transfer based on amplitude shift keying (ASK) modulation techniques. A proposed efficient class-E power amplifier is presented. The design presents a full transcutaneous inductive powering system to transfer power and data from an outside human body to implanted devices such as implanted microsystems to stimulate and monitor the nerves and muscles with low band frequency of 13.56 MHz according to the industrial–scientific–medical (ISM) band to avoid the tissue damage. A novel ASK demodulator powered with 1.9 V is proposed with a power recovery system. The modulation index is 13% and the modulation rate 7.3% with data rate 1 Mbit/s, and with power efficiency 66%. The system has been designed using 0.35-μm fabricated CMOS technology. The mathematical model is given and the design is simulated using OrCAD PSpice 16.2 software tool and for real-time simulation, the electronic workbench MULISIM 11 has been used to simulate the class-E power amplifier.

An ultra-low power RF interface for wireless-implantable microsystems

This paper presents an efficient radio frequency (RF) front-end for power and data telemetry in biomedical implantable devices. The fully integrated system includes amplitude shift keying (ASK) demodulator, low drop out (LDO) power regulator, full wave voltage rectifier and limiter circuit. The demodulator utilizes a new ultra low power envelope amplifier that removes the need for any voltage comparator or Schmitt trigger circuit. With a carrier frequency of 12MHz and 1Mbps data rate, the proposed ASK demodulator achieves a modulation index range from 5% up to 100% while consuming less than 35μW from induced power. The regulator can provide a maximum stimulation current of 1.2mA under a ripple suppressed 3.3V supply. Designed in a 0.18μm CMOS process, the system totally draws about 35μA excluding the stimulation current.

Investigation of efficient ASK demodulation for wirelessly powered biodevices

A new hardware architecture of amplitude shift keying (ASK) demodulation for portable wirelessly data-combined power transfer, especially those biomedical applications requiring permanently harvested power through radio frequency, is proposed. The architecture along with its circuit details provides dramatically enhanced energy efficiency in the system while at the same time achieving cost-effective data demodulation under a real challenging condition at the ASK modulation index. Experimental results in a 0.18 µm technology demonstrate the advantages of the proposed design.

A low power automatic gain control loop for a receiver

This paper proposes a new structure to lower the power consumption of a variable gain amplifier (VGA) and keep the linearity of the VGA unchanged. The structure is used in a high rate amplitude-shift keying (ASK) based IF-stage. It includes an automatic gain control (AGC) loop and ASK demodulator. The AGC mainly consists of six-stage VGAs. The IF-stage is realized in 0.18 μm CMOS technology. The measurement results show that the power consumption of the whole system is very low. The system consumes 730 μA while operating at 1.8 V. The minimum ASK signal the system could detect is 0.7 mV (peak to peak amplitude).

Basic study of a transcutaneous information transmission system using intra-body communication

The transcutaneous communication system (TCS) is one of the key technologies for monitoring and controling artificial hearts and other artificial organs in the body. In this study, we have developed a new TCS that uses the human body as a conductive medium. Having no energy conversion from electric currents into electromagnetic waves and light provides energy-saving data transmission with a simple electrical circuit. Each unit of the TCS mainly consists of two electrodes, an amplitude shift keying (ASK) modulator and an ASK demodulator (carrier frequency: 4 and 10 MHz). A resonant frequency of an L-C tank circuit including the capacitance component of the body is tuned into each carrier frequency in order to apply the data current effectively into the body. Performance of the TCS was evaluated by a communication test on the surface of a human body. The TCS was able to transmit 3,315 bytes of data bi-directionally at a transmission rate of 115 kbps from a left wrist to a right forearm, to an abdomen and to a left calf without communication error. The power consumption of each TCS unit was 125 mW with an ASK modulated current of 7 mA (RMS). While further study is required to secure its safety, the TCS promises to be a next-generation transcutaneous communication device.

An LTPS TFT Demodulator for RFID Tags Embeddable on Panel Displays

This paper presents an amplitude-shift-keying (ASK) demodulator for RF identification tags, which can be embedded on panel displays. The ASK demodulator was implemented in 3-mum low-temperature polycrystalline silicon (LTPS) thin-film transistor (TFT) technology. Since the threshold voltages of LTPS TFTs are higher than CMOS transistors, the conventional demodulator implementation will degrade the demodulator sensitivity significantly. The novel full-wave demodulator circuit was proposed to resolve the issue of high threshold voltage and reduce the ripples of the demodulated envelope. Operated at 8 V, the demodulator consumes 1.6 mW of power. The input carrier frequency was tested up to 13.56 MHz, and the highest ASK modulated data rate is 100 kb/s. The circuit size of the LTPS TFT demodulator is 500 mum times 450 mum.

A compensability RF CMOS mixed-signal interface for implantable system

The implantable microsystem requires the hybrid circuit technology for a brain-machine interface. The paper described a compensability mixed-signal implantable receiver including an analog front-end and a digital processing circuit. The analog circuit consists of mainly an amplifier, an amplitude shift keying (ASK) demodulator, a clock extraction and a power recovery. In this paper, the amplifier and the ASK demodulator are described and provided without the capacitor and the resistor, fully integrated low-power circuit. The processing circuit is designed with the digital technology, so that implementing the correct synchronous signal. The carrier frequency of the circuit is applied in the 10 MHz range; the data rates up to 1 M bit/s are supported, suitable for complex implants such as the brain neural stimulating and so on. The compensability low-power and the high-performance implantable interface using a CMOS technology has been designed, fabricated and verified. All of circuits were implemented in a standard 0.18-μm CMOS process.

A Truly Low-Cost High-Efficiency ASK Demodulator Based on Self-Sampling Scheme for Bioimplantable Applications

In the fields of wireless bioelectronics implants and sensor network systems, amplitude shift keying (ASK) is one of the most commonly used schemes employed to modulate the baseband signal with reference to the intermediate or even the carrier frequency. In this study, a demodulator architecture capable of dealing with most of the previous limitations in an ASK-utilized medical implant, especially in want of being powered through wireless delivering, is proposed. It features the abilities of working on a very small modulation index and being provided without any R/C component(s) inside by means of a self-sampling scheme. The design has been implemented in an 18-mum CMOS process. The demodulator circuit occupies a die size of merely 32.3 times 14.5 mu m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Analytic results from both simulated gradation and fabricated chips show that the proposed circuit can operate at a carrier of 2 MHz and achieve a modulation rate of up to 50%. The results also demonstrate that the presented work can still perform a proper demodulation even with a modulation index beneath 5.5%. An average power of approximately 336 muW was confirmed in return for the remarkable advantages. All aspects regarding the design, including a review of the prior arts, system consideration, circuit description, and analyses from simulation phase to actual measurement, are presented in detail.

All-MOS ASK Demodulator for Low-Frequency Applications

A miniature amplitude-shift-keying (ASK) demodulator without any passive elements, i.e., R or C, for low-frequency applications is presented in the paper. The noise margin of the envelope detector in the proposed ASK demodulator is enlarged such that any Schmitt trigger or current limiting resistor is no longer needed. It results in the number of transistors required for the ASK demodulator circuit is reduced to 12, while the area is merely 0.003025 mm2 using 0.35-mum 2P4M CMOS process. The power consumption is found to be 1.01 mW by physical measurement on silicon. The data rate is measured to be 250 kbps for 2-MHz carrier frequency and 27% modulation index.

A 570-kbps ASK demodulator without external capacitors for low-frequency wireless bio-implants

This paper proposes a novel structure of ASK (amplitude shift keying) demodulators, which requires no external capacitors, for implantable micro-stimulators. By using a traditional β multiplier reference to detect the signal envelope, followed by a Schmitt trigger and a load driver, the large off-chip capacitor in traditional ASK demodulators is not required any more. Therefore, the proposed circuit possesses small area to be integrated in an SOC (system-on-chip). Besides, due to the lack of the large capacitor, the proposed circuit can operate with a higher data rate using lower frequency carriers. The proposed circuit is integrated in an implantable micro-stimulator on silicon using 0.35μm 2P4M CMOS process. The area of the proposed circuit occupies merely 0.039mm2 with a maximum power dissipation of less than 12mW (including the power consumption of the analog circuits of the micro-stimulator) by measurement results on silicon. Moreover, the measurement results verify that the proposed ASK demodulator can detect the ASK modulated signal up to 570kbps data rate at 2MHz carrier frequency when the modulation index is 10%.