Low Phase Error Research Articles

Calibration of Dual-Polarised Antennas for Air-Coupled Ground Penetrating Radar Applications

Radar polarimetry is a technique that can be used to enhance target detection, identification and classification; however, the quality of these measurements can be significantly influenced by the characteristics of the radar antenna. For an accurate and reliable system, the calibration of the antenna is vitally important to mitigate these effects. This study presents a methodology to calibrate Ultra-Wideband (UWB) dual-polarised antennas in the near-field using a thin elongated metallic cylinder as the calibration object. The calibration process involves measuring the scattering matrix of the metallic cylinder as it is rotated, in this case producing 100 distinct scattering matrices from which the calibration parameters are derived, facilitating a robust and stable solution. The calibration procedure was tested and validated using a Vector Network Analyser (VNA) and two quad-ridged antennas, which presented different performance levels. The calibration methodology demonstrated notable improvements, aligning the performance of both functioning and under-performing antennas to equivalent specifications. Mid-band validation measurements indicated minimal co-polar channel imbalance (<0.3 dB), low phase error (<0.8°) and improved cross-polar isolation (≈48 dB).

A Hybrid Architecture 360° Phase Shifter With Continuously Tunable Phase Shift and Low In-Band Phase Error

A Hybrid Architecture 360° Phase Shifter With Continuously Tunable Phase Shift and Low In-Band Phase Error

High-performance thin-film lithium niobate optical 90° hybrid with a novel CMRR assessment method

Ultra-Compact 90° Hybrid DesignThe optical 90° hybrid uses a 4 × 4 MMI coupler with an ultra-compact footprint of ~9 μm × 107 μm, which is 3 times shorter than previous work. Novel CMRR Calculation MethodA new method to assess the CMRR using a single unequal Mach-Zehnder interferometer (MZI), reducing fabrication complexity and measurement errors. Excellent PerformanceThe device features low excess loss (0.55 to 1.4 dB), low phase errors (< ±4.5°), and high CMRR (< −17.8 dBe) over a wide wavelength range (1530 to 1605 nm).

A novel 6.5-13.5GHz 6-bit digital phase shifter with ultra low RMS phase error in 0.25-µm GaAs p-HEMT technology

A novel 6.5-13.5GHz 6-bit digital phase shifter with ultra low RMS phase error in 0.25-µm GaAs p-HEMT technology

A 22.5–33.5-GHz Hybrid Phase Shifter With Low Phase and Amplitude Error for 5G and Satellite Communication

A 22.5–33.5-GHz Hybrid Phase Shifter With Low Phase and Amplitude Error for 5G and Satellite Communication

Direct synthesis method of wideband tunable filtering phase shifter based on complex matched transversal multiple resonances

In this article, a wideband filtering phase shifter (FPS) based on transversal multiple resonances is proposed. By utilizing transversal resonances with complex impedance, a wide operation band is achieved with compact circuit size. By doubly loading the tunable external coupling networks (ECNs) with complex impedance, the FPS obtains continuous phase tuning with stable filtering performance. In addition to the structural construction, a set of analytical formulas and guidelines for the direct synthesis of the FPS are provided, rather than tedious optimization. Finally, an FPS using transversal three resonances with complex impedance is designed, fabricated, and measured to validate the concept. The example showcases a wide 10-dB RL bandwidth of 32.5% with high selectivity, a compact size of 0.068 λg2, a phase shift range (PSR) of 105°, and a low phase error of ±5.4∘.

Design of a novel wide-angle Rotman lens beamformer for 5G mmWave applications

The attachment of 5G with millimeter wave (mmWave) frequencies offers massive capacity and low latency to reveal the full 5G experiences. High directive gain and beamforming are considered essential for mmWave 5G systems. The main requirements of the beamforming network for 5G mmWave applications are the scanning coverage of ± 60° and SLL > 10 dB in a wide operational bandwidth over the standard 5G frequency bands. In this paper, a novel PCB-based wide-angle Rotman lens beamformer is designed, simulated, and successfully measured to meet the mentioned requirements for 5G mmWave applications. A comprehensive improved design methodology is provided for all components of the Rotman lens to reach a wide scanning angle, enhanced sidelobe level, and low scan loss. The end-fire Vivaldi antenna is selected as an array element for easy integration to the beamforming network as well as its capability to use in dual-polarization configuration. The proposed Rotman lens is operational in the 24–30 GHz frequency band covering 5G n257, n258, and n261 frequency bands. The results show a nearly constant 8 beams across the whole bandwidth steering from − 53° to 53° in 15° increments to provide ± 60° coverage with the SLL > 10 dB and scan loss < 1.9 dB. The retrieved novelties from this work contain an effective design methodology for an optimized Rotman lens with wide-scan angle and low phase and amplitude error, non-uniform distribution based array ports, and integration with end-fire antenna for possible dual polarization and 2-D beamforming capabilities. The comparison of the proposed beamformer with the most recent works shows several advantages in terms of integrated structure and performances including bandwidth, wide scanning angle, SLL, and scan loss. With such performances, this beamformer can be used for various mmWave and 5G applications such as advanced antenna systems, massive MIMO systems, and hybrid beamforming systems.

A New Synthesis Method to Design Broadband Continuously Tunable Phase Shifters Based on Coupled Line With Low Phase Error

A New Synthesis Method to Design Broadband Continuously Tunable Phase Shifters Based on Coupled Line With Low Phase Error

A 4.5–5.5-GHz Compact 6-bit Phase Shifter With Low RMS Phase and Amplitude Errors Based on Bandpass Structure for High-Power Applications

A 4.5–5.5-GHz Compact 6-bit Phase Shifter With Low RMS Phase and Amplitude Errors Based on Bandpass Structure for High-Power Applications

A 10-20 GHz 6-Bit High-Accuracy Digital Step Attenuator with Low Insertion Loss in 0.15 µm GaAs p-HEMT Technology.

In a beamforming circuit for a modern broadband phased-array system, high accuracy and compactness have received sufficient attention as they are directly related to side lobe level and fabrication cost, respectively. In order to meet the low phase error required, this paper proposed an ultra-broadband 6-bit digital step switched-type attenuator (STA) with capacitive/inductive compensation networks. Compared to the conventional methods, the proposed technique employs an improved simplified T-structure with capacitive compensation networks, which simultaneously achieves low insertion loss and high-accuracy amplitude/phase control. In addition, on-chip level shifting circuit is integrated to avoid complex control schemes. The strategy of prioritizing return loss is adopted to alleviate the performance degradation caused by impedance mismatch after cascade. As a proof-of-principle demonstration, a wideband 6-bit STA with core area of only 0.5 mm × 1.8 mm was designed via 0.15-micrometer GaAs pHEMT technology. It exhibits ultra-broadband operation with a 31.5 dB amplitude tuning range and a 0.5 dB tuning step. The insertion loss of the reference state is 4-5.3 dB. The return loss is better than 15 dB for all the 64 states. The RMS amplitude and phase errors are less than 0.2 dB and 2° over the 10 to 20 GHz.

Variable-Gain Phase Shifter with Phase Compensation Using Varactors

This paper demonstrates a phase compensation technique using varactors for variable-gain phase shifters (VGPSs). The VGPS consists of an I/Q generator and I/Q variable gain amplifiers (I/Q VGAs). I/Q VGAs based on common-emitter stages are enabled to control the gain by adjusting the collector current of the transistor. However, the phase control performance degenerates because the input capacitance varies with the collector current. The proposed phase compensation technique reduces the variation in the insertion phase of the I/Q VGA by adjusting the voltage of the varactor provided at its input and maintaining the input capacitance constant in any gain state. As a result, the VGPS can provide a low phase and amplitude error under phase control. A Ka-band VGPS with the proposed phase compensation technique, fabricated in a 130-nm SiGe BiCMOS process, demonstrates a 0.73° and 0.06 dB improvement in the RMS phase and amplitude error compared with the case without the compensation technique. The VGPS achieves measured RMS amplitude and phase errors of less than 0.19 dB and 0.75°, respectively, in an amplitude control range of more than 20 dB with a frequency range of 28 to 32 GHz.

A wearable EEG system for closed-loop neuromodulation of sleep-related oscillations

Objective. Healthy sleep plays a critical role in general well-being. Enhancement of slow-wave sleep by targeting acoustic stimuli to particular phases of delta (0.5–2 Hz) waves has shown promise as a non-invasive approach to improve sleep quality. Closed-loop stimulation during other sleep phases targeting oscillations at higher frequencies such as theta (4–7 Hz) or alpha (8–12 Hz) could be another approach to realize additional health benefits. However, systems to track and deliver stimulation relative to the instantaneous phase of electroencephalogram (EEG) signals at these higher frequencies have yet to be demonstrated outside of controlled laboratory settings. Approach. Here we examine the feasibility of using an endpoint-corrected version of the Hilbert transform (ecHT) algorithm implemented on a headband wearable device to measure alpha phase and deliver phase-locked auditory stimulation during the transition from wakefulness to sleep, during which alpha power is greatest. First, the ecHT algorithm is implemented in silico to evaluate the performance characteristics of this algorithm across a range of sleep-related oscillatory frequencies. Secondly, a pilot sleep study tests feasibility to use the wearable device by users in the home setting for measurement of EEG activity during sleep and delivery of real-time phase-locked stimulation. Main results. The ecHT is capable of computing the instantaneous phase of oscillating signals with high precision, allowing auditory stimulation to be delivered at the intended phases of neural oscillations with low phase error. The wearable system was capable of measuring sleep-related neural activity with sufficient fidelity for sleep stage scoring during the at-home study, and phase-tracking performance matched simulated results. Users were able to successfully operate the system independently using the companion smartphone app to collect data and administer stimulation, and presentation of auditory stimuli during sleep initiation did not negatively impact sleep onset. Significance. This study demonstrates the feasibility of closed-loop real-time tracking and neuromodulation of a range of sleep-related oscillations using a wearable EEG device. Preliminary results suggest that this approach could be used to deliver non-invasive neuromodulation across all phases of sleep.

DESIGN OF FIRST ORDER DIFFERENTIATOR WITH PARALLEL ALL-PASS STRUCTURE

In this paper a new method for design of the first order differentiator is presented. The proposed differentiator consists of two parallel branches, i.e. direct path and IIR all-pass filter. The described design method allows one to obtain solution with minimum mean relative error at the desired region by controlling the ratio of phase response extremes. A small relative magnitude error, as well as a low phase error, at low frequencies is condition for good time domain behaviour. The obtained differentiator can be realized by means of only two multipliers, hence being a good choice for real time applications. The proposed solution provides a lower magnitude error than several known differentiators with similar phase error.

Source Switched Charge-Pump PLLs for High-Dose Radiation Environments

This paper presents a radiation tolerant charge-pump Phase-Locked Loop (PLL) with low static phase error variability suitable for high-performance clock systems in high-dose radiation environments. We investigate the use of source switching charge-pump architectures to minimize any voltage-or dose-dependent charge injection and address the limitations of Enclosed Layout Transistors (ELTs) in the conventional drain switched charge-pump. The circuit has been processed in a 65nm Complementary Metal Oxide Semiconductor (CMOS) technology and has been experimentally verified with X-rays up to a total ionizing dose of 180 Mrad.

Bandwidth‐reconfigurable filtering phase shifters with phase‐slope alignment for different bandwidth states

AbstractIn this article, filtering phase shifters with the capability to reconfigure their operating bandwidth are proposed for the first time. The proposed phase shifter is based on a triple‐mode half‐wavelength microstrip‐line resonator with two loaded stubs. The operating bandwidth of proposed phase shifters can be adjusted by changing the frequency ratio (Rf) between the third (fp3) and the first (fp1) resonant frequencies, which can be flexibly controlled by changing the length of loaded stubs. Meanwhile, phase slopes also can be aligned by further studying Rf to achieve low phase errors. For validation, 90° phase filtering phase shifters centered at 2.5 GHz are designed, and measured. Measured results indicate that the fractional bandwidth of this phase shifter can be flexibly tuned from 16% to 36% with good filtering performance. Meanwhile, the phase error and magnitude imbalance of the proposed 90° phase shifters are less than ±5° and 0.3 dB, respectively.

A Composite Right/Left-Handed Phase Shifter-Based Cylindrical Phased Array with Reinforced Particles Responsive to Magneto-Static Fields

A conformal cylindrical phased array antenna excited with composite right/left-handed (CRLH) phase shifters is proposed. The phase tuning of the CRLH phase shifter is achieved by embedding novel magneto-static field-responsive micron-sized particles in its structure. It is shown that through the tiny magnet activation of these novel magneto-static particles at appropriate locations along the length of CRLH stub and inter-digital fingers, variable phase shifts are obtained. The proposed particle-based CRLH phase shifter operates in C-band (5–6) GHz with a low insertion loss and phase error. The 1 × 4 cylindrical phased array is excited with the four unit cells of the proposed particle-embedded CRLH transmission line phase shifters to scan the main beam at desired scan angles. A prototype of a 1 × 4 cylindrical phased array excited with the particle-based CRLH phase shifters was fabricated, and the results show that the simulated results are in close agreement with the measured results. The conformal cylindrical array with the proposed particle-based CRLH phase shifters has great potential for use in printed and flexible electronics design where commercially available phase shifters have a definite drawback.

Polarization-insensitive 90° optical hybrid using silica-based PLC.

A 90° optical hybrid (OH) based on a 4×4 multimode interference (MMI) coupler is characterized and analyzed using the silica-based planar light circuit. The OH is designed to be polarization-insensitive with an extremely low polarization-dependent loss (<0.18d B) and phase error (w i t h i n±1.3∘). The fabricated chip exhibits an excess loss of 3.4dB and 3.8dB for TE and TM polarizations at 1550nm. The measured phase error is w i t h i n±7.2∘ over 50nm in the C+L band with a polarization-dependent error w i t h i n±3.5∘. The fabrication tolerance of the MMI width and waveguide sidewall angle is analyzed, which can well explain the deviation from the theoretical calculation.

Design and Synthesis of Reconfigurable Filtering Phase Shifter Using Optimization of Coupling Matrix

In this article, a design and synthesis method to realize filtering phase shifter with tunable insertion phase and passband center frequency is proposed. The filtering phase shifter is based on a circuit consisting of three resonators in a triplet topology. Coupling matrix analysis is employed to obtain the detailed relationship between the insertion phase and the amplitude response of the filter. Then, differential evolution (DE) algorithm-based optimization method is proposed to obtain the coupling matrix with an arbitrary prespecified insertion phase. The proposed optimization method can not only obtain the coupling matrix with desired insertion phase but also can align the phase slope of different phase states, resulting in a low-phase error over the filter passband. Furthermore, a method is proposed to extend the phase shift range to full 360° by switching the signs of specific terms in the coupling matrix, significantly simplifying the required optimization procedure. Finally, a filtering phase shifter using lumped elements is designed, fabricated, and measured to validate the design concept. The phase-shifting range of the circuit can achieve 360° with continuously reconfigurable center frequency covering from 650 to 860 MHz.

Wideband Continuously Tunable Phase Shifter With Phase Slope Tunability and Low Phase Error

In this article, a type of a wideband continuously tunable phase shifter (PS) with phase slope tunability is proposed. It is designed based on the theory of the wideband multimode filter. By drawing the phase performance design graphs, phase performance with a specific insertion phase and a phase slope is mapped into the corresponding magnitude filtering performance. Proper magnitude states are then chosen to construct the required phase performance. By virtue of the tunable phase, tunable phase slope, and wideband operation, the proposed PS constructs a continuously tunable PS with a wide operation band, large phase shift range (PSR), and low in-band phase error by cascading switched-line PSs. From measurement, this structure is exhibited to obtain 0&#x00B0;&#x2013;360&#x00B0; phase shift in a wide fractional bandwidth of 26.1&#x0025;, while maintaining a low in-band phase error smaller than &#x00B1;5.5&#x00B0;.

Ultra wideband CMOS digital T-type attenuator with low phase errors

A proposed inductive-phase-compensation ultra wideband CMOS digital T-type attenuator design based on an analysis of minimising phase errors is presented in this letter. In a standard CMOS technology, the proposed attenuator is analytically demonstrated to have low phase errors due to the inductive-phase-compensation network. A design equation is inferred and a wide-band 4dB attenuation bit digital attenuator with low phase errors is designed as a test vehicle for the proposed approach.