Radio Frequency Receiver Research Articles

Noise Analysis of Phase-Demodulating Receivers Employing Super-Regenerative Amplification

Growing interest in ultralow-power radio frequency receivers has reinvigorated research in super-regenerative amplifier (SRA) architectures, in part due to their ability to achieve enormous gain at very low power. Conventionally, SRAs have been paired with envelop detectors that demodulate amplitude-modulated signals (e.g., ON–OFF keying); mathematical models have been developed to predict the performance of such systems. Since modern communication applications require more spectrally efficiency modulation schemes, this paper develops a mathematical model that predicts the stochastic behavior of SRAs when used in phase-demodulating receivers. This stochastic model is then used to predict the sensitivity of a phase-demodulating receiver employing a Colpitts-based SRA. Results from the developed model are validated with measurements of a discrete prototype, illustrating that SRAs can be used with $I/Q$ mixing to demodulate quadrature phase-shift keying signals with −88-dBm sensitivity when the SRA consumes 1.2 mA at 1.5 V at 45 MHz.

Underwater radio frequency image sensor using progressive image compression and region of interest

The increasing demand for underwater robotic intervention systems around the world in several application domains requires more versatile and inexpensive systems. By using a wireless communication system, supervised semi-autonomous robots have freedom of movement; however, the limited and varying bandwidth of underwater radio frequency (RF) channels is a major obstacle for the operator to get camera feedback and supervise the intervention. This paper proposes the use of progressive (embedded) image compression and region of interest (ROI) for the design of an underwater image sensor to be installed in an autonomous underwater vehicle, specially when there are constraints on the available bandwidth, allowing a more agile data exchange between the vehicle and a human operator supervising the underwater intervention. The operator can dynamically decide the size, quality, frame rate, or resolution of the received images so that the available bandwidth is utilized to its fullest potential and with the required minimum latency. The paper focuses first on the description of the system, which uses a camera, an embedded Linux system, and an RF emitter installed in an OpenROV housing cylinder. The RF receiver is connected to a computer on the user side, which controls the camera monitoring parameters, including the compression inputs, such as region of interest (ROI), size of the image, and frame rate. The paper focuses on the compression subsystem and does not attempt to improve the communications physical media for better underwater RF links. Instead, it proposes a unified system that uses well-integrated modules (compression and transmission) to provide the scientific community with a higher-level protocol for image compression and transmission in sub-sea robotic interventions.

Ultra-low-loss high-pass filter with air-core short-circuit coaxial cable

This paper presents a novel ultra-low-loss high-pass filter with 3 dB cutoff frequency of 890 MHz for astronomical receiver radio frequency interference mitigation application. The filter consists of three series capacitors, four shunt inductors, and microstrip circuit board. Specially, 4 shunt inductors are actualized by fabricating air-core short-circuit coaxial cable inductors in the filter box body, and the quality factor of these cable inductors is up to 762.2 and 1046, respectively, at 1.4 GHz. In the expected passband of 1.1–1.9 GHz, S parameters measurement show that insertion loss is lower than 0.16 dB and two-port return loss is larger than 20 dB; noise measurement show that filter noise temperature is lower than 8 at 300 K ambient temperature. Noise sources of this filter are analyzed by simulation and measurement.

Performance Analysis and Compensation of Joint TX/RX I/Q Imbalance in Differential STBC-OFDM

Differential space time block coding (STBC) achieves full spatial diversity and avoids channel estimation overhead. Over highly frequency-selective channels, STBC is integrated with orthogonal frequency division multiplexing (OFDM) to efficiently mitigate intersymbol interference effects. However, low-cost implementation of STBC-OFDM with direct-conversion transceivers is sensitive to In-phase/Quadrature-phase imbalance (IQI). In this paper, we quantify the performance impact of IQI at both the transmitter and receiver radio frequency front-ends on differential STBC-OFDM systems which has not been investigated before in the literature. In addition, we propose a widely-linear compensation algorithm at the receiver to mitigate the performance degradation caused by the IQI at the transmitter and receiver ends. Moreover, a parameter-based generalized algorithm is proposed to extract the IQI parameters and improve the performance under high-mobility. The adaptive compensation algorithms are blind and work in a decision-directed manner without using known pilots or training sequences. Numerical results show that our proposed compensation algorithms can effectively mitigate IQI in differential STBC-OFDM.

The influence of microwave pulse width on the thermal burnout effect of a PIN diode limiting-amplifying system

This paper analyzes the influence of the microwave pulse width on the thermal burnout effect of a PIN diode limiting-amplifying system. Based on theoretical analyses and simulation, the relationship of the burnout effect on a PIN diode limiter and a PIN diode limiting-amplifying system is obtained first. By adopting an absorption efficiency factor, the theoretical model of the relationship between the microwave pulse width and the burnout power threshold for the PIN diode limiting-amplifying system is obtained. The proposed theoretical formulas can be determined by using at least two sets of simulation or measurement results to fit the constant coefficients, which can greatly reduce the simulation or experimental costs. The results obtained by the theoretical formulas are in good agreement with the numerical simulation results obtained by our self-designed device–circuit joint simulator, which verifies the correction of the theoretical analyses and modeling. The available microwave pulse width range for the proposed theoretical formulas is from 10ns to 10μs. In consideration of the potential threat of microwave pulses, the system-level study results obtained in this paper will be helpful for the design of the radio frequency receivers.

On the Application of Inverse-Mode SiGe HBTs in RF Receivers for the Mitigation of Single-Event Transients

Best practice in mitigation strategies for single-event transients (SETs) in radio-frequency (RF) receiver modules is investigated using a variety of integrated receivers utilizing inverse-mode silicon–germanium (SiGe) heterojunction bipolar transistors (HBTs). The receivers were designed and implemented in a 130-nm SiGe BiCMOS technology platform. In general, RF switches, low-noise amplifiers (LNAs), and downconversion mixers utilizing inverse-mode SiGe HBTs exhibit less susceptibility to SETs than conventional RF designs, in terms of transient peaks and duration, at the cost of RF performance. Under normal RF operation, the SET-hardened switch is mainly effective in peak reduction, while the LNA and the mixer exhibit reductions in transient peaks as well as transient duration.

Assessment of Integrated Circuits Emissions With an Equivalent Dipole-Moment Method

An appropriate integrated circuit (IC) evaluation early in the design stage is essential to ensure timely development of mobile devices with a satisfactory total isotropic sensitivity (TIS), a figure of merit to measure radio-frequency receiver sensitivity. An IC evaluation method based on equivalent dipole-moment source using the transverse electromagnetic mode (TEM) cell is proposed and experimentally investigated in terms of correlation of measured TIS with two existing IC emission measurement methods: the TEM cell method (IEC 61967-2) and the near-field scan method (IEC 61967-3). In addition, a cost-effective and reliable test scheme is introduced so the three approaches can share a single common test board to avoid potential hardware-to-hardware deviation. Measurement results on three software-controlled operation states are compared with respective TIS measured in an anechoic chamber. The best correlation was obtained in the proposed equivalent dipole-moment-based evaluation method and the limitations of the two previous methods are discussed.

Secure Communication via a Wireless Energy Harvesting Untrusted Relay

The broadcast nature of the wireless medium allows unintended users to eavesdrop on confidential information transmission. In this regard, we investigate the problem of secure communication between a source and a destination via a wireless energy harvesting untrusted node that acts as a helper to relay the information; however, the source and destination nodes wish to keep the information confidential from the relay node. To realize the positive secrecy rate, we use destination-assisted jamming. Being an energy-starved node, the untrusted relay harvests energy from the received radio-frequency (RF) signals, which include the source's information signal and the destination's jamming signal. Thus, we utilize the jamming signal efficiently by leveraging it as a useful energy source. At the relay, to enable energy harvesting and information processing, we adopt power splitting (PS) and time switching (TS) policies. To evaluate the secrecy performance of this proposed scenario, we derive analytical expressions for two important metrics, viz., the secrecy outage probability and the ergodic secrecy rate. The numerical analysis reveals design insights into the effects of different system parameters such as PS ratio, energy harvesting time, target secrecy rate, transmit signal-to-noise ratio (SNR), relay location, and energy conversion efficiency factor, on secrecy performance. Specifically, the PS policy achieves better optimal secrecy outage probability and optimal ergodic secrecy rate than that of the TS policy at higher target secrecy rate and transmit SNR, respectively.

Considerations for using personal Wi-Fi enabled devices as “clickers” in a large university class

Interactive student response systems, commonly referred to as clickers, have increased in popularity in higher education classrooms as a means to improve engagement and enhance learning. Clicker systems come with handheld devices as well as a radio frequency receiver. A Wi-Fi connection to the receiver is possible, enabling students to use their personal smartphones, tablets, or laptops instead of the handheld device. The objective of this study was to determine the feasibility of students using their personal Wi-Fi enabled devices as clickers in a large university class. In addition, we sought to elicit student perceptions of clicker use in general. Overall, the majority of students preferred using their personal devices, thus saving several minutes of class time in distribution and collection. Students gave very positive feedback on the use of clickers; however, they did not like that clickers could be used to track attendance and participation.

Design of a CMOS integrated on-chip oscilloscope for spin wave characterization

Spin waves can perform some optically-inspired computing algorithms, e.g. the Fourier transform, directly than it is done with the CMOS logic. This article describes a new approach for on-chip characterization of spin wave based devices. The readout circuitry for the spin waves is simulated with 65-nm CMOS technology models. Commonly used circuits for Radio Frequency (RF) receivers are implemented to detect a sinusoidal ultra-wideband (5-50 GHz) signal with an amplitude of at least 15 μV picked up by a loop antenna. First, the RF signal is amplified by a Low Noise Amplifier (LNA). Then, it is down-converted by a mixer to Intermediate Frequency (IF). Finally, an Operational Amplifier (OpAmp) brings the IF signal to higher voltages (50-300 mV). The estimated power consumption and the required area of the readout circuit is approximately 55.5 mW and 0.168 mm2, respectively. The proposed On-Chip Oscilloscope (OCO) is highly suitable for on-chip spin wave characterization regarding the frequency, amplitude change and phase information. It offers an integrated low power alternative to current spin wave detecting systems.

Self-Learning RF Receiver Systems: Process Aware Real-Time Adaptation to Channel Conditions for Low Power Operation

Prior research has established that dynamically trading-off the performance of the radio-frequency (RF) front-end for reduced power consumption across changing channel conditions, using a feedback control system that modulates circuit and algorithmic level “tuning knobs” in real-time based on received signal quality, leads to significant power savings. It is also known that the optimal power control strategy depends on the process conditions corresponding to the RF devices concerned. This leads to an explosion in the search space needed to find the best feedback control strategy, across all combinations of channel conditions and receiver process corners, making simulation driven optimal control law design impractical and computationally infeasible. Since this problem is largely intractable due to the above complexity of simulation, we propose a self-learning strategy for adaptive RF systems. In this approach, RF devices learn their own performance vs. power consumption vs. tuning knob relationships “on-the-fly” and formulate the most power-optimal control strategy for real-time adaptation of the RF system using neural-network based learning techniques during real-time operation. The methodology is demonstrated using SISO and MIMO RF receiver front-ends as test vehicles and is supported by hardware validation leading to 2.5X-3X power savings with minimal overhead.

Monitored Laser Grinding Using Real Time Nanobots Data: A Novel Mudcake Removal Approach

For ensuring casing and cementing quality, mud cake removal is essential. Various problems like stuck pipe take place because of the presence of mud cake. Mechanical methods of water jetting and chemical methods by means of acids, oxidizers, chelating agents, etc., are currently employed for mud cake removal. However, water jetting can cause water blockage problems and has detrimental effects on well productivity. Also, mud cakes of different permeability will not be removed by same intensity water jets. Acids and oxidizers are very reactive but nonspecific species, imposing several post perforation problems and formation damage. As an alternative, we propose a new method in this study with the usage of nanobots and laser grinding. The nanobots, placed in carrier, can be deployed in all directions into the targeted zone. These non-adherent and self-propelled nanobots will move through the vertical permeability of the mud filtrate and would interpret the petro physical properties of the mud filtrate. The sensors would then send this data to molecular processor and with the help of radio frequency transmitter and receiver, we could immediately interpret the real time data from every point in the zone of interest. This data would be used to change the intensity of the lasers in accordance with the petro physical properties. Lasers, lowered through wireline, would then vaporise the mud cake through spallation according to its thickness and will grind the mud cake by creating popped holes. This novel idea of real time laser grinding with the help of nanobots holds great potential in removing mud cake precisely and efficiently and could also be useful in multilateral and horizontal wells.

RF Receiver Characterization and Spurious-Free Dynamic Range Enhancement for PIM/Weakly Nonlinear Device Measurements

This paper proposes a technique to characterize and postcompensate for the dynamic nonlinearity exhibited by radio frequency (RF) receivers employed in passive intermodulation (PIM) and weakly nonlinear devices characterization (low gain compression of the order of 0.1 dB). The proposed technique begins by accurately characterizing the RF receiver’s nonlinearity using two-tone and multitone stimuli with swept frequency spacing and input power level. Then, a pruned Volterra series-based postcompensation model is devised to mitigate the dynamic weak nonlinear distortions exhibited by the receiver. The technique was validated in two steps. First, the capacity of the postcompensation technique to separate the RF receiver’s intermodulation from the device under test’s intermodulation was assessed. Second, its capacity to postcompensate for the dynamic nonlinearity exhibited by the RF receiver and to enhance its spurious-free dynamic range (SFDR) was assessed using digitally modulated stimuli. The application of the proposed technique reduced the third-order intermodulation (IMD3) of the RF receiver by an average of 10 dB. This technique can significantly relax the requirements on duplexers and tone injection techniques used to enhance the accuracy of PIM measurements. Furthermore, the receiver’s SFDR was extended by up to 15 dB.

Hybrid Positron Emission Tomography/Magnetic Resonance Imaging: Challenges, Methods, and State of the Art of Hardware Component Attenuation Correction.

Attenuation correction (AC) is an essential step in the positron emission tomography (PET) data reconstruction process to provide accurate and quantitative PET images. The introduction of PET/magnetic resonance (MR) hybrid systems has raised new challenges but also possibilities regarding PET AC. While in PET/computed tomography (CT) imaging, CT images can be converted to attenuation maps, MR images in PET/MR do not provide a direct relation to attenuation. For the AC of patient tissues, new methods have been suggested, for example, based on image segmentation, atlas registration, or ultrashort echo time MR sequences. Another challenge in PET/MR hybrid imaging is AC of hardware components that are placed in the PET/MR field of view, such as the patient table or various radiofrequency (RF) coils covering the body of the patient for MR signal detection. Hardware components can be categorized into 4 different groups: (1) patient table, (2) RF receiver coils, (3) radiation therapy equipment, and (4) PET and MR imaging phantoms. For rigid and stationary objects, such as the patient table and some RF coils like the head/neck coil, predefined CT-based attenuation maps stored on the system can be used for automatic AC. Flexible RF coils are not included into the AC process till now because they can vary in position as well as in shape and are not accurately detectable with the PET/MR system.This work summarizes challenges, established methods, new concepts, and the state of art in hardware component AC in the context of PET/MR hybrid imaging. The work also gives an overview of PET/MR hardware devices, their attenuation properties, and their effect on PET quantification.

Time Switching for Wireless Communications with Full-Duplex Relaying in Imperfect CSI Condition

In this paper, we consider an amplify-and-forward (AF) full-duplex relay network (FDRN) using simultaneous wireless information and power transfer, where a battery-free relay node harvests energy from the received radio frequency (RF) signals from a source node and uses the harvested energy to forward the source information to destination node. The time-switching relaying (TSR) protocol is studied, with the assumption that the channel state information (CSI) at the relay node is imperfect. We deliver a rigorous analysis of the outage probability of the proposed system. Based on the outage probability expressions, the optimal time switching factor are obtained via the numerical search method. The simulation and numerical results provide practical insights into the effect of various system parameters, such as the time switching factor, the noise power, the energy harvesting efficiency, and the channel estimation error on the performance of this network. It is also observed that for the imperfect CSI case, the proposed scheme still can provide acceptable outage performance given that the channel estimation error is bounded in a permissible interval.

Throughput analysis of two-way relay networks with wireless energy harvesting capabilities

Wireless energy harvesting is an efficient way to prolong the lifetime of energy constrained networks. This paper considers a two-way amplify-and-forward (AF) based relay network, where two communicating nodes concurrently transmit their information signals to a relay node. The relay node is energy constrained, and it therefore first harvests energy from the received radio frequency (RF) signals. For energy harvesting at a relay node, we have analyzed the performance of two energy harvesting protocols: the time switching based relaying protocol (TSR), and the hybrid power-time switching based relaying protocol (HPTSR). Once the energy is harvested using one of these protocols, the relay then amplifies and forwards the received information signal towards its destination. We derive analytical expressions for the outage probability and achievable throughput for the aforementioned protocols. Our numerical results verify the analytical derivation, and show the effect of different system parameters on achievable throughput.

In vivo MR imaging with simultaneous RF transmission and reception.

To present a practical scheme of a simultaneous radiofrequency (RF) transmit (Tx) and receive (Rx) (STAR) system for MRI, discuss the challenges and solutions, and show preliminary in vivo MR images obtained with this new technique. A remotely controlled STAR system was built and tested with a transverse electromagnetic head coil on a 4T (Oxford, 90 cm-bore) MRI scanner equipped with an Agilent DirectDrive console (Agilent, Santa Clara, CA). In vivo head images have been acquired using continuous sweep excitation and acquisition. The bench test and MR experimental results show our STAR system to have high isolation (60 dB) between Tx and Rx, with insensitivity to load swings created by head motion. To acquire in vivo head images, ultralow RF peak power of 50 mW was used. A novel motion-insensitive STAR MRI technique was developed and experimentally tested. The first in vivo MR images using this method were acquired. Magn Reson Med 76:1932-1938, 2016. © 2016 International Society for Magnetic Resonance in Medicine.

Development of a Radio Frequency Remote-Controlled Amphibious Solid Waste Collecting Mobot

Robots in general are used to aid people in different tasks from simple activities to activities that prevent also people from harm. In fields of Robotics it is important that these robots are not complete replacements of humanity but mere tools that will improve human lives and more so save lives if possible. In this paper, the group presented a remote-controlled mobot with amphibious capabilities. The system is accessible through a radio frequency transmitter and receiver which there is an executable file that allows the mobot to be controlled. The characterization of the system and its performance are presented here as well.

2.7–4.0 GHz PLL with dual-mode auto frequency calibration for navigation system on chip

A 2.7–4.0 GHz dual-mode auto frequency calibration (AFC) fast locking PLL was designed for navigation system on chip (SoC). The SoC was composed of one radio frequency (RF) receiver, one baseband and several system control parts. In the proposed AFC block, both analog and digital modes were designed to complete the AFC process. In analog mode, the analog part sampled and detected the charge pump output tuning voltage, which would give the indicator to digital part to adjust the voltage control oscillator (VCO) capacitor bank. In digital mode, the digital part counted the phase lock loop (PLL) divided clock to judge whether VCO frequency was fast or slow. The analog and digital modes completed the auto frequency calibration function independently by internal switch. By designing a special switching algorithm, the switch of the digital and analog mode could be realized anytime during the lock and unlock detecting process for faster and more stable locking. This chip is fabricated in 0.13 μm RF complementary metal oxide semiconductor (CMOS) process, and the VCO supports the frequency range from 2.7 to 4.0 GHz. Tested 3.96 GHz frequency phase noise is −90 dBc/Hz@100 kHz frequency offset and −120 dBc/Hz@1 MHz frequency offset. By using the analog mode in lock detection and digital mode in unlock detection, tested AFC time is less than 9 μs and the total PLL lock time is less than 19 μs. The SoC acquisition and tracking sensitivity are about −142 dBm and −155 dBm, respectively. The area of the proposed PLL is 0.35 mm2 and the total SoC area is about 9.6 mm2.

Theoretical Comparison of Direct-Sampling Versus Heterodyne RF Receivers

An intuitive high-level argument is presented suggesting that direct-sampling radio frequency (RF) receivers using Nyquist analog–digital converters can be as power-efficient as analog heterodyne receivers for equal dynamic range specifications, at least at lower RF frequencies well below the $f_{t}$ of the IC process. System planning for direct-sampling receivers is reviewed, highlighting dBFS/Hz as an intrinsic measure of dynamic range, independent of channel and Nyquist bandwidths. Power dissipation versus dynamic range for recently reported heterodyne and direct-sampling receivers is examined.