Automatic Gain Control Circuit Research Articles

Automatic amplitude control for phasemeter of spaceborne laser interferometry

Laser interferometry of the space gravitational wave antenna needs to demodulate the gravitational wave signal by a phasemeter with high phase readout precision. A phasemeter in digital phase locking loop structure was proved to be sensitive to the amplitude fluctuation of the input signal experimentally in previous studies. In this work, we have carried out theoretical analysis on the influence of amplitude fluctuation on phase readout precision. The results show that amplitude noise belongs to multiplicative noise, which cannot be eliminated by differential measurement. We used the automatic gain control (AGC) circuit to suppress the fluctuation of amplitude. Contrast experiments were performed to verify that the AGC circuit could promote the performance of the phasemeter system for gravitational wave detection.

Intelligent MRI Room Design Using Visible Light Communication with Range Augmentation

Radio waves and strong magnetic fields are used by Magnetic Resonance Imaging (MRI) scanners to detect tumours, wounds and visualize detailed images of the human body. Wi-Fi and other medical devices placed in the MRI procedure room produces RF noise in MRI Images. The RF noise is the result of electromagnetic emissions produced by Wi-Fi and other medical devices that interfere with the operation of the MRI scanner. Existing techniques for RF noise mitigation involve RF shielding techniques which induce eddy currents that affect the MRI image quality. RF shielding techniques are complex and lead to RF leakage. VLC (Visible light Communication) is an emerging and efficient technology to avoid RF interference near MRI scanners. Range augmentation with power conservation of the LED is a big challenge in existing VLC systems. The major objective of the proposed work is to develop an intelligent-MRI room design without RF interference using visible light communication and enhance the distance between VLC transmitter and VLC receiver. In this paper, it is proposed to implement VLC using On-Off keying modulation and enhance distance using large active area photodiodes with Automatic Gain Control Circuit (AGC) using software and hardware. The performance of the proposed intelligent MRI-VLC system is analyzed by calculating Bit Error Rate at an inclined distance of 50 cm away from line of sight of the LED. The Experimental results showed that the maximum distance achieved was 400 cm at Bit Error Rate (BER) of 1.5 × 10−5.

Microwave Power Detectors in Different CMOS Design Architectures: A Review

Transmitted and received power must be controlled quickly and accurately to comply with government regulations, minimize interference, and optimize power consumption. Microwave power detectors (PDs) are critical building blocks employed in applications such as integrated circuit tests and measurements, wireless communication, and automatic-gain-control (AGC) circuits to monitor signal power level. PDs are utilized as received signal strength indicators (RSSIs) to adjust the gain of the intermediate frequency/RF signal via an AGC circuit <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> . They are also used in mobile terminals to monitor the transmitted power, thereby optimizing power consumption. Two popular methods employed to measure the power signal level are root mean square (RMS) value and peak value. Peak detectors capture the input’s peak power to provide power information, whereas the RMS PD provides information about the average power <xref ref-type="bibr" rid="ref2" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[2]</xref> . <xref ref-type="fig" rid="fig1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Figure 1</xref> shows a conventional block diagram of a microwave PD employed in an RF transmitter. The directional coupler is used to couple the output signal from the power amplifier to a PD. The signal is then converted to a dc voltage that the power controller utilizes to change the power amplifier’s gain, thereby improving the transmitter’s linearity.

Phase noise modelling of MEMS resonant accelerometer with non-AGC-driven circuit

Phase noise is an essential performance indicator for microelectromechanical system (MEMS) resonant accelerometers. The optimal resolution achievable is limited by the close-to-the carrier phase noise resulting from the modulation of noise sources by the mechanical resonator and driving circuit. Compared with the frequently used automatic gain control (AGC) circuit, the non-AGC scheme is more concise and can avoid the additional frequency flicker noise and 1/f 5 phase noise introduced by the AGC module. Although the mechanisms of these two kind of control loops are well-known by the communities, the phase noise modelling study on the non-AGC loop, especially compared with that of AGC loop is insufficient. This paper established a phase noise model for the AGC and non-AGC closed loop circuit of MEMS resonant accelerometer. The model includes the effects of resonator thermal noise, random loading noise of proof masses, front-circuit noise, comparator noise, AGC noise and amplitude stiffness coupling on the output noise spectrum of the resonant accelerometer. This paper carries the noise analysis through a behaviour level simulation with Simulink. The measured frequency power spectral density and Allan variance are very close to the theoretical predictions, which verifies the effectiveness of the phase noise model. The test results show that the white noise and the bias instability of the silicon resonant accelerometer are 837 ng (√Hz)−1 and 140 ng respectively, which are in good agreement with the model prediction results.

Real-time Signal-to-Noise Ratio Optimization of Bio-Impedance Signal for Cuffless Blood Pressure Monitoring.

Continuous and unobtrusive blood pressure (BP) monitoring provides significant advantages in predicting the onset of cardiovascular disease. Bio-impedance sensing is a prominent method for continuous BP monitoring in a wearable form factor that can effectively measure blood pulsations from the arteries and translate them into BP. However, assessing the quality of the bio-impedance signal captured from small electrodes placed on the skin is required to determine the accuracy of BP estimation. In wearable devices, frequent movements of the electrodes on the skin are expected which cause non-optimal contact quality between the electrodes and the skin. This can lead to high skin-electrode impedance which can cause saturation of the current injection module of the bio-impedance device. This phenomenon degrades the signal quality In this paper, we present an automatic gain control (AGC) circuit that controls the amplitude of the current injection into the body based on sensing the skin-electrode impedance to ensure injection of maximum current to maximize the signal-to-noise ratio (SNR) while avoiding saturation of the current injection module. In this work, the proposed AGC method shows higher quality of blood pulsation from bio-impedance signal measured from a human subject with 1.59 dB improvement in SNR which leads to a better estimation of blood pressure.Clinical Relevance- The proposed automatic gain control (AGC) circuit establishes a more accurate method of continuous blood pressure monitoring using bio-impedance.

A novel amplitude and frequency demodulation algorithm for frequency-modulation atomic force microscope

Frequency-modulation atomic force microscope (FM-AFM) has been a widely-used instrument to achieve atomic or subatomic resolution imaging. However, the low bandwidth of automatic gain control circuit for amplitude control loop and the low setting rate of frequency demodulation loop have been a big stumbling block for FM-AFM to realize fast measurement. In this article, a novel demodulation algorithm for FM-AFM is proposed. The Kalman filter approach is proposed to realize amplitude demodulation, and the FM signal is processed as a phase modulation signal (indirect FM signal). The performance of the algorithm is verified through experiment on field-programmable gate array, and compared with existing methods. Through the proposed method, the tracking performance of FM-AFM can be improved and the response rate can be increased without loss of precision.

Increasing the accuracy of the automatic control system of unmanned aircraft under conditions of non-stationary interference

An approach to solving the problem of improving the accuracy of an automatic control system for unmanned aerial vehicles (UAVs) in conditions of non-stationary interference is considered. Such interference is caused by random changes in the noise of the measuring sensors, which are installed in the UAV, when changing the yaw, roll and flight altitude of the UAV due to restructuring or transformation of the operating mode of the propulsion system of the UAV. Non-stationary noises do not allow obtaining the maximum effect of applying the theory of optimal filtration based on the classical Kalman filter. The authors proposed a method of stabilizing sensor noise by using a noise automatic gain control circuit installed in front of the Kalman filter. For its quantitative assessment, a team of authors developed a computer model and carried out dynamic modeling based on test signals, which showed the applicability of the classical Kalman filter in non-stationary conditions and a decrease in the filtering errors of the automatic control system.

A 20-Gb/s wideband AGC amplifier with 26-dB dynamic range in 0.18-μm SiGe BiCMOS

This paper presents a 20-Gb/s automatic gain control (AGC) amplifier in a 0.18-μm SiGe BiCMOS for high-speed applications. The proposed AGC amplifier compactly consists of a folded Gilbert variable-gain amplifier (VGA), a post amplifier (PA), a 50-Ω output buffer, and AGC loop including an open-loop peak detector (PD), a RC low-pass filter (LPF), and an error amplifier (EA). The AGC amplifier achieves the broadband characteristic by utilizing inductive peaking and capacitive degeneration as well as fT-doubler techniques to overcome the large parasitic capacitances. The proposed AGC circuits together with a linear VGA exhibits a wide gain control range of 45 dB for the received signal strength indication (RSSI). The measured AGC amplifier achieves a maximum gain of 21 dB and a -3-dB bandwidth (BW) of 20.6 GHz, which can support up to 25.4-Gb/s data rate. For the pseudorandom bit sequence (PRBS) length 231–1 with a bit-error rate (BER) of 10−12 at 20 Gb/s, the measured input dynamic range is 26 dB (20–400mVpp) and the peak-to-peak data jitter is less than 8 ps. The AGC amplifier consumes a power of 160 mW from a 3.3-V supply voltage and occupies an area of 850 μm × 850 μm.

Design of Programmable Gain Amplifier Module in Dynamic Liquid Level Tester

Oil and gas wells need to perform dynamic liquid level detection during the development to prevent inaccurate detection during drilling and damage the oil and gas field. The Program Controlled Gain Amplifier (PGA) module designed in this paper is used in the dynamic liquid level test instrument. Using STM32F4O7ZGT6 as a microcontroller (MCU), the MCU, a multi-stage variable gain amplifier and a peak detection circuit form a closed loop control, forming an automatic gain control (AGC) circuit. First, the signal output by the peak detection circuit is collected by AD, and then the entire module is in a dynamic balance state through DA feedback. This AGC system can accurately control the gain and output signal. Finally, the ratio-average filtering algorithm is used to test the experimental data. Experimental results show that the module can achieve gain control of-20∼60dB in the frequency range of 1kHz∼20MHz; the relative error of the output voltage is within 3%. This module achieves the performance indicators of broadband, high precision and high gain. Compared with the traditional module, its advantage is that it takes into account and optimizes the three performance indicators at the same time, and has better stability.

Фотоприймальний пристрій, стійкий до фонової засвітки, з розширеним динамічним діапазоном вхідних сигналів

Measurement of periodic optical information signals in the background light noise with a photodetector with extended dynamic range is an urgent task of modern electronics and thus has become the aim of this study. To increase the dynamic range of the photodetector, a new version of the automatic gain control (AGC) circuit has been developed, which consists of an AGC controller, an output photodetector amplifier and an AGC detector. The authors measured the dynamic range of the photodetector when receiving optical radiation with a wavelength of 1064 nm in the power range from 2.10–8 to 2.10–5 W at a modulation frequency of 20 kHz with the AGC on. Under these conditions, the dynamic range of the photodetector was found to be up to 67 dB. If the AGC was off, the dynamic range did not exceed 30 dB. Thus, the study made it possible to create a photodetector with an extended dynamic range up to 67 dB based on a new version of the AGC circuit. The design of the photodetector allowed choosing a useful signal of a particular modulation frequency in the frequency range from 3 to 45 kHz and effectively suppresses the frequencies caused by optical interference in the low frequency range from the frequency of the input signal of constant amplitude up to 3 kHz inclusive. This compensates the current up to 15 mA, which is equivalent to the power of light interference of about 15 mW. Further research should address the issues of reliability of the proposed photodetector design and optimization of its optical system. The photodetector can be used in geodesy and ambient air quality monitoring.

Simulation of Steady‐State Temperature Rise of Electric Heating Field of Wireless Sensor Circuit Fault Current Trigger

This article analyzes the structure of the wireless sensor circuit, considering the balance of power consumption, integration, area, noise, etc., and adopts a radio frequency wireless sensor circuit with a low‐IF structure. Through the analysis and comparison of traditional analog current trigger and digital current trigger structure, the feed‐forward current trigger structure is selected, which is composed of received signal strength indicator (RSSI) and variable gain amplifier (VGA), which achieves low power consumption, fast stabilization time, and wide dynamic range design. The received signal strength indicator adopts the form of approximate logarithmic amplifier, five‐stage double feedback loop structure, and realizes lower power consumption. In order to prevent the load current trigger from entering the speed saturation zone, a gain unit structure in which the superimposed current trigger is connected to the NMOS tube as the load is proposed. The test results show that the circuit has a good power consumption performance (1 mW) and at the same time 56.8 dB/m sensitivity. In this paper, through the analysis of the current trigger system and the analysis and comparison of the existing variable gain amplifiers, the variable gain amplifier structure composed of the folded wireless sensing unit and the index control unit is adopted. In order to reduce the power consumption of the circuit and increase the output swing, a structure in which the two‐stage folding wireless sensor unit shares the controlled voltage‐to‐current part of the circuit is proposed. Aiming at the design requirements of the system, this article discussed in detail the architecture of the entire temperature measurement node and the design parameters of the chip and completed the overall architecture design of the chip. The simulation results of the steady‐state temperature rise of the electric heating field show that the circuit has achieved an input dynamic adjustment range of more than 60 dB, the maximum power consumption is 1 mW, and the linearity error is less than 0.5 dB. The designed automatic gain control circuit is implemented in SMIC 0.18 cape CMOS process. The simulation results of the steady‐state temperature rise of the electric heating field show that the circuit has a 56 dB input dynamic adjustment range within a linear error of 1.25 dB, and the time constant is 7.55 ms, and power consumption is 2.84 mW. Through the steady‐state temperature rise simulation and test results of the electric heating field, the correctness of the design is verified and it meets the system requirements.

An Automatic Gain Control Circuits for the Microphone Read-out Integrated Circuit

An Automatic Gain Control Circuits for the Microphone Read-out Integrated Circuit

Design of weak optical signal detection system for measuring eye axial length

Since the reflectivity of two reflective surfaces of the corneal surface and the retinal pigment cortex is greatly different when measuring the axial length of eye, the intensity of the reflected optical signal belonges to the weak signal category under the premise of the incident light safety in the eye. In order to remove the noise and quickly extract the peak value of the signal for the calculation of the starting and ending point of the eye axial length, a weak optical signal detection system was designed. This system used PIN photodiode to receive weak optical signal and a weak light signal detection system was built coordinated with the I-V conversion circuit, automatic gain control circuit as well as the post-processing circuit. The experiment used ZIESS simulation eye to test. The results show that the designed detection system can detect the weak optical signal of about 0.77 nW at least, the maximum photoelectric conversion capacity can reach 4.5×108 V/W, the signal-to-noise ratio is more than 9 dB, and the maximum error between the measured eye length and the actual value can reach 0.05%. This system is characterized by low noise, high gain and large dynamic range, which provides an effective solution for accurate measurement of the eye axial length.

Fractional-Order Phase Shifters with Constant Magnitude Frequency Responses

This contribution presents and experimentally analyzes the idea how to reach the constant magnitude as well as the phase response in the fractional-order (FO) phase when shifting two-ports. The straightforward method employing the automatic gain control circuit (AGC) in a cascade after so-called constant phase block approximating FO integrator or differentiator is studied. The variable gain amplifier utilized in AGC and simple RC-based FO constant phase elements (approximating capacitors with order alpha = 1/4 and alpha = 1/2 as an example) connected in the feedback of operational amplifier-based integrator are established in the experimental setup. The operation indicated in three decades (between 100 Hz and 100 kHz) is evaluated. The known solutions of the standard FO phase shifting circuits are discussed and generally compared with the features obtained in this paper, together with the supposed effects of AGC on their performances.

Analysis and Design of Ultra-Large Dynamic Range CMOS Transimpedance Amplifier With Automatically-Controlled Multi-Current-Bleeding Paths

In this paper, a fully-integrated transimpedance amplifier with ultra-large dynamic range and automatic gain control function is presented. By first deploying three AGC-controlled current paths in the low noise pre-amplifier, the transimpedance amplifier (TIA) can accommodate a significantly enlarged input current. Meanwhile, the range of automatic transimpedance adjustment is enhanced utilizing the automatic gain control (AGC) circuit, tunable pre-amplifier (PrA), and variable gain amplifier (VGA). Besides the above blocks, the TIA with a size of 1.26 × 1.33 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> also integrates level shifter, post-amplifier, buffer, DC offset cancellation (DCOC), bandgap reference (BGR), and low-dropout regulator (LDO). With a single 3.3-V external supply voltage, the fully integrated TIA in 0.11 μm CMOS achieves a measured input dynamic range up to 7.4 mA@2.5 Gb/s, an input referred noise as low as 137.3 nA and a differential trans-impedance gain of 10 kQ. Taking the bandwidth, dynamic range, and trans-impedance gain into account, the fabricated CMOS TIA demonstrates the largest input dynamic range with maintaining competitive comprehensive performance.

A 65nm CMOS Ka-band AGC Design

A CMOS Ka-band AGC based on 65nm CMOS process is presented in this paper, the Chebyshev band-pass filter is used for filtering the input signal, the Gilbert structure with extended bandwidth technology is selected to for voltage gain amplifier, the current mirror structure composed of MOS tubes is employed for the voltage detector, and the control voltage generator circuit is designed based on the exponential relationship between the voltage and the current of the transistors. The simulation shows with the 1.0V supply voltage, the AGC working frequency range is between 27.5GHz and 31.3GHz, the input range of the automatic gain control circuit is between -20dB ~ 20dB, The overall layout area is around 1.15mm2.

CMOS Amplifier Receiver with AGC Bandwidth Circuit

This research work focuses on the concept of wireless optical communication system. A „CMOS Amplifier Receiver with Gain and Bandwidth Adjustment Capabilities‟ has been designed to detect the gain and bandwidth of the transmitted signal. Configurations of receivers had been designed using LMH6624 as the front-end transimpedance amplifier and the LMH6504 amplifier as the Automatic Gain Control (AGC) circuit. Furthermore, this research work also use LMH6732 amplifier at the output in order to have the capability of controlling the bandwidth. The output frequency response achieved by transimpedance amplifier using LMH6624 is 180.44 MHz and 144.61 MHz cut-off frequency after the AGC circuit while the controllable bandwidth amplifier by using LMH6732 produced is 75.32 MHz.

2.5 Gbit/s Optical Receiver Front-End Circuit with High Sensitivity and Wide Dynamic Range

AbstractAn optical receiver front-end circuit is designed for passive optical network and fabricated in a 0.18 um CMOS technology. The whole circuit consists of a transimpedance amplifier (TIA), a single-ended to differential amplifier and an output driver. The TIA employs a cascode stage as the input stage and auxiliary amplifier to reduce the miller effect. Current injecting technique is employed to enlarge the input transistor’s transconductance, optimize the noise performance and overcome the lack of voltage headroom. To achieve a wide dynamic range, an automatic gain control circuit with self-adaptive function is proposed. Experiment results show an optical sensitivity of –28 dBm for a bit error rate of 10

Application of automatic gain control for radiometer diagnostic in SST-1 tokamak.

This paper describes the characterisation of a negative feedback type of automatic gain control (AGC) circuit that will be an integral part of the heterodyne radiometer system operating at a frequency range of 75-86 GHz at SST-1 tokamak. The developed AGC circuit is a combination of variable gain amplifier and log amplifier which provides both gain and attenuation typically up to 15 dB and 45 dB, respectively, at a fixed set point voltage and it has been explored for the first time in tokamak radiometry application. The other important characteristics are that it exhibits a very fast response time of 390 ns to understand the fast dynamics of electron cyclotron emission and can operate at very wide input RF power dynamic range of around 60 dB that ensures signal level within the dynamic range of the detection system.

An automatic gain control circuit to improve ECG acquisition

Abstract Introduction Long-term electrocardiogram (ECG) recordings are widely employed to assist the diagnosis of cardiac and sleep disorders. However, variability of ECG amplitude during the recordings hampers the detection of QRS complexes by algorithms. This work presents a simple electronic circuit to automatically normalize the ECG amplitude, improving its sampling by analog to digital converters (ADCs). Methods The proposed circuit consists of an analog divider that normalizes the ECG amplitude using its absolute peak value as reference. The reference value is obtained by means of a full-wave rectifier and a peak voltage detector. The circuit and tasks of its different stages are described. Results Example of the circuit performance for a bradycardia ECG signal (40bpm) is presented; the signal has its amplitude suddenly halved, and later, restored. The signal is automatically normalized after 5 heart beats for the amplitude drop. For the amplitude increase, the signal is promptly normalized. Conclusion The proposed circuit adjusts the ECG amplitude to the input voltage range of ADC, avoiding signal to noise ratio degradation of the sampled waveform in order to allow a better performance of processing algorithms.