Group Delay Variation Research Articles

Absolute antenna group delay variations: estimation, single station repeatability and their influence on coordinate and float ambiguity estimation in baseline positioning

Phase center offsets and variations (PCV) are common corrections applied to global navigation satellite system (GNSS) phase observations in the context of precise point positioning. Similar to PCV are group delay variations (GDV), which affect code observations. In this paper, absolute GDVs, which are independent of a reference antenna, are estimated as antenna- and frequency-specific for the frequencies 1575.42 MHz and 1176.45 MHz, where separation of receiving and transmitting antenna GDV is possible with non-rotating antennas. Nineteen receiving and transmitting antennas of GPS, Galileo, BeiDou, and QZSS satellites, using observations from static reference stations, are considered. The single station repeatability of the receiver antenna GDV i.e., the estimation of the GDV using only one station, is evaluated for all antenna-frequency combinations. The repeatability ranges from 1.1 to 7.6 cm at a zenith angle of 80°, showing significant differences between antennas and frequencies. The estimated GDV corrections are applied to multi-GNSS baseline positioning using a total of 116 baselines. Receiver antenna GDV corrections exhibit a significant non-zero mean effect on the code-based vertical coordinate estimate. Float ambiguities are estimated using observation periods of up to 20 min. The 0.95-quantile effect of the GDV corrections on narrow lane ambiguity estimates is 2.02 cycles at the first epoch and 0.54 cycles after 5 min using 30 s observation sampling. The effect on wide lane ambiguities is constant over the 20-min period considered, with the 0.95-quantile being around 0.1 cycles for the GNSS considered.

Mobile-integrated SRR-based four-port MIMO antenna for broadband mm-wave 5G applications

ABSTRACT A low-profile, single-layered, compact-size, highly-isolated four-port MIMO antenna integrated within a 5 G smartphone has been proposed for a futuristic mm-wave broadband communication system. The proposed MIMO antenna configuration has been derived from a conventional inset-fed rectangular microstrip patch by introducing two parallel I-shaped slots on the patch surface for operating over a wide bandwidth of 4.91 GHz, that is, from 26.78 to 31.69 GHz. The antenna geometry has an overall dimension of 20.9 mm x 20.9 mm x 0.787 mm. The proposed configuration attained a maximum gain of 8.11 dBi and radiation efficiency of 90% at 28 GHz resonating frequency. The integration of the square-shaped SRR structure among closely packed antenna elements has significantly enhanced the overall isolation by 13 dB without compromising the antenna’s physical dimensions. The realisation of the S-parameters has also been carried out from the equivalent circuit model to agree with the results obtained from the electromagnetic simulation through CST software. The measured radiation patterns assured the minimal variation with simulated characteristics along the E and H planes. A comprehensive safety investigation of the proposed MIMO antenna has been carried out to assess power densities (<10 W/ m 2 ) across different usage modes, including data, reading, and talking in a mobile application perspective. Several diversity parameters, including ECC (<0.0001), DG (>9.999 dB), CCL (<0.12 bits/sec/Hz), MEG, and TARC, have also been evaluated as performance metrics. Furthermore, the linear transmission property of the proposed MIMO antenna has been validated through the variation of group delay (<0.5 ns) over operating frequency bands in the far-field region.

Ultra-wideband high gain low group delay variation amplifier for phased-array radar system

This paper describes a ultra-wideband (UWB) three-stage cascaded high gain amplifier with low group delay variation for phased-array radar system. The shunt inductor at the input not only provides an electrostatic discharge (ESD) path to ground, but also introduces a new notch for S11, thus extending the matching bandwidth. Staggered tuning of load impedance peaks at each stage facilitates a balance between flat gain and low group delay variation. The output stage further enhances the overall gain while reinforcing bandwidth and stability through resistive feedback, and employs an adaptive bias circuit for linearity improvement. Implemented in SMIC 40-nm CMOS technology, the proposed amplifier achieves good input impedance matching, flat gain and low group delay variation of ±73.5 ps over 4.7–16 GHz. The whole power consumption is 198.3 mW and the output 1 dB compression point (OP1dB) is greater than 9 dBm. After careful design, the chip size is 0.64 mm2.

Effect of User Antenna Group Delay Variation Error on Advanced RAIM

Effect of User Antenna Group Delay Variation Error on Advanced RAIM

165–220-GHz Broadband Amplifier With $\pm$0.75-dB Gain Variation and Minimum Group Delay Variation in SiGe BiCMOS

165–220-GHz Broadband Amplifier With $\pm$0.75-dB Gain Variation and Minimum Group Delay Variation in SiGe BiCMOS

Application of the Tianwen-1 DOR Signals Observed by Very Long Baseline Interferometry Radio Telescopes in the Study of Solar Wind Plasma and a Coronal Mass Ejection

The Tianwen-1 (TW1) Mars probe experienced solar conjunction for the first time in 2021. The China VLBI Network (CVN) observes the differential one-way ranging (DOR) signals of TW1 throughout its phase. This paper explores the application of CVN observation data to study the solar wind plasma. First, the frequency and phase of the DOR carrier and sidetones at each station are calculated using the Doppler method. Then, the variations in both the differential phase delays (DPD) and the total electron content (TEC) are calculated using the phase of the sidetones. We also statistically analyze the fluctuations in the Delta-DOR (ΔDOR) group delay. The results indicate that the fluctuations of the frequency, phase, ΔDOR group delay, delay rate, and TEC variations of the TW1 signals increase with the decrease of the heliocentric distance. On 2021 November 2, a coronal mass ejection (CME) passed across the ray paths of the telescope beams, when the heliocentric distance and heliographic latitude of the projected position of Mars were 30.6 Rs and 3°, respectively. Our data catch the impact of the CME on the DOR signals. The change of the DPD reaches 170 ps, which is equivalent to 986 TECU. We utilize the cross correlation to analyze the frequency fluctuations at multiple stations, and obtain the propagation direction and velocity variations of the CME. Our analysis indicates that multifrequency DOR signals observed by very long baseline interferometry stations have great application to characterize the electron density variations and propagation of the solar wind plasma.

Analytical modelling of ultra‐small group delay variation of ultra‐broadband RF power amplifier using NSGA‐II algorithm

AbstractThis paper proposes a ± 9.4 ps ultra‐small group delay (GD) variation of fully integrated 65 nm complementary metal oxide semiconductor (CMOS) power amplifier (PA) over 6.5–17 GHz broadband for wireless application. The proposed CMOS PA is realised by using broadband stage, RLC inter‐stage and power stage topologies. The non‐dominated sorting genetic algorithm (NSGA‐II) is employed for PA parameter optimisation to ensure a small GD variation of ±9.4 ps over broadband with an excellent small signal gain flatness of 23.65 ± 1.85 for 6.5–17 GHz. The small GD variation of ±9.4 ps and ± 11.05 ps are attained under two cases of DC supply voltages of 2.4/1.2 V and 1.2/1.2 V, respectively. To the best of author's knowledge, the achieved GD variations are lowest among all CMOS PAs as reported so far. In addition, an analytical modelling of GD is derived to validating the minimum GD variation using zero‐pole compensation. With supply voltages of 2.4/1.2 V at 6.5 GHz, the large signal power gain, Psat and OP1dB are 26 dB, 19.3 dBm and 17.94 dBm, respectively, while peak power added efficiency (PAE) is 38.196%. At reduced supply voltages of 1.2/1.2 V, the PA achieves maximum power gain of 17.7 dB and peak PAE of 35% at 6.5 GHz. The CMOS PA occupies an area of 0.206 mm2.

A Compact Fully-Differential Distributed Amplifier with Coupled Inductors in 0.18-µm CMOS Technology

This paper presents a compact fully-differential distributed amplifier using a coupled inductor. Differential distributed amplifiers are widely required in optical communication systems. Most of the distributed amplifiers reported in the past are single-ended or pseudo-differential topologies. In addition, the differential distributed amplifiers require many inductors, which increases the silicon cost. In this study, we use differentially coupled inductors to reduce the chip area to less than half and eliminate the difficulties in layout design. The challenge in using coupled inductors is the capacitive parasitic coupling that degrades the flatness of frequency response. To address this challenge, the odd-mode image parameters of a differential artificial transmission line are derived using a simple loss-less model. Based on the analytical results, we optimize the dimensions of the inductor with the gradient descent algorithm to achieve accurate impedance matching and phase matching. The amplifier was fabricated in 0.18-μm CMOS technology. The core area of the amplifier is 0.27 mm2, which is 57% smaller than the previous work. Besides, we demonstrated a small group delay variation of ±2.7 ps thanks to the optimization. the amplifier successfully performed 30-Gbps NRZ and PAM4 transmissions with superior jitter performance. The proposed technique will promote the high-density integration of differential traveling wave devices.

Design of 3.1-10.6 GHz UWB CMOS Power Amplifier using Cascade Topology

Power amplifier is an important component in the wireless communication system. Design of the power amplifier in UWB transceiver is challenging as the signal need to be transmitted over a wide bandwidth. Several criteria need to be fulfilled such as good linearity, good wideband matching, high efficiency and low power consumption. This paper presents the design of a power amplifier with 3.1-10.6 GHz using 0.18 μm CMOS technology for ultra-wide band application. The proposed power amplifier used three cascaded amplifier stages in order to achieve good gain and wide-band width. The results show that the proposed power amplifier design has an average gain of 7.28 dB, an input return loss less than -7.48 dB, an output return loss less than -4.782 dB, and group delay variation of ±151.9 ps is achieved over the entire band. A good input 1dB-compression point of 6.67 dBm and input third order intercept point of 0 dBm is achieved at 5 GHz.

Tunable slow light device based on a graphene metasurface.

Slow light devices have significant applications in memory, switching, and quantum optics. However, the design and fabrication of slow light devices with large tunable group delay are still challenging. Here, a graphene-based slow light device that can electrically modulate the group delay of terahertz (THz) waves is proposed and experimentally demonstrated. The unit cell of the device consists of a U-shaped metal resonator and an Ω-shaped metal resonator, with three graphene ribbons embedded between the two resonators. Under electrical stimuli, a relatively high amplitude modulation depth of 74% is achieved and the maximum transmission amplitude is as high as 0.7 at the transmission peak of 0.6 THz. Most importantly, the maximum group delay variation reaches 5 ps at 0.76 THz and the maximum group delay amplitude is as high as 8.8 ps. The experiment shows good agreement with simulation. This study paves a new way for developing novel switchable nanophotonic devices and slow light devices.

A highly robust RF 65 nm CMOS power amplifier design using Quasi-Newton control algorithm for wireless system

This article reports a novel robust approach towards CMOS power amplifier (PA) using Quasi-newton (QN) control algorithm in 65 nm CMOS process which provides best performance parameters over redundant wide bandwidth ranging from 2.4 to 16.4 GHz frequency band. Each stage are designed and optimized using QN algorithm to get desired goals such as high linearity, small group delay variations and high PAE across the entire frequency band of interest. Moreover, pole-zeros compensation technique is adopted and derived to get better stability of the proposed PA. The simulation and measurement results of PA achieved a small signal power gain of 10.5–16.8 dB with input return loss of better than 10 dB over the frequency band of 2.4 GHz to 16.4 GHz. A small group delay variation of ±58 ps over full frequency band of operation is achieved by optimizing the design parametric analysis. It is also observed that within the frequency of 6.5 to 14.6 GHz, an excellent small group delay variation of only ±11 ps is achieved and this is due to stage-2 tuning compensation technique. It also demonstrates the achieved input power in 1 dB compression points are −3.1 to 4.3 dBm, leading to maximum power added efficiency of 36.3%, respectively. The proposed PA consumes a lower DC power of 20.5 mW under supply voltage of 1.5. In addition, Process, voltage and temperature (PVT) analysis is executed at different conditions in order to achieve a robustness of the proposed PA over the entire band of operation.

Cascaded Reflection-Type Group Delay Controller With a Wideband Flat Group Delay

This letter presents a wideband group delay controller (GDC) based on cascaded reflection-type phase shifters (RTPSs). Frequency tunable resonators are used as the reflective loads of each phase shifter so that the phase shifter has a variable group delay resulting in a reflection-type GDC (RTGDC). Two RTGDCs with different types of reflective loads are cascaded to compensate for their group delay variation over frequency. The first and the second stage of the cascaded RTGDC are respectively in charge of the delay in low and high-frequency bands and the cascaded delay is flat over a wide bandwidth. The proposed cascaded RTGDC operates at 3.7 GHz over 200-MHz bandwidth. The measured group delay varies from 0.67 to 2.18 ns, which is a 1.51-ns group delay variation under 9.1% normalized group delay variation over the bandwidth. The return loss is over 18 dB and the insertion loss is 2.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 1.3 dB at 3.7 GHz.

Design and Analysis of a Wideband K/Ka-Band CMOS LNA Using Coupled-TL Feedback

We demonstrate a low power (PD) 22-33 GHz CMOS low-noise amplifier (LNA) with low noise-figure (NF) and small group-delay (GD) variation for 28 GHz 5G system. Body-selfforward-bias (BSFB) technique, i.e., connection of transistor’s body to drain via body resistance, is used for threshold and supply voltage reduction, and substrate leakage suppression. Gain and NF enhancement at the same PD is achieved because lower VDD and higher transconductance (due to larger bias current) are used. Current-reused topology is used for low PD. Coupled transmission -line (TL) feedback neutralization technique is proposed for further gain and NF enhancement. The feedback from output (drain) to input (gate) via gate-drain capacitance (Cgd) can be cancelled by the feedback from drain (through source) to gate via the coupled TL and gate-source capacitance (Cgs). The LNA consumes 12.2 mW and achieves S21 of 16 dB, 3 dB bandwidth (f3dB) of 11 GHz (22-33 GHz), minimum NF (NFmin) of 2.5 dB, average NF (NFavg) of 3.1 dB, and GD variation of ±6 ps for 22-33 GHz, and figure-of-merit (FOM) of 91.7 GHz. Moreover, the LNA achieves input third-order intercept point (IIP3) of -3 dBm. The NF and FOM are one of the best results ever reported for LNAs with f3dB greater than 7 GHz and PD lower than 15 mW.

Design of a highly-isolated, high-gain, compact 4-port MIMO antenna loaded with CSRR and DGS for millimeter wave 5G communications

In this paper, a low-profile, compact, high-gain antenna solution for four-port mm-wave broadband MIMO communication in a 5G environment is presented. The proposed antenna design consists of two rectangular patches connected through a corporate feed network and two quarter-wavelength square-shaped CSRRs on the ground plane. The overall size of the proposed four-port orthogonal MIMO configuration is 28.3 mm × 28.3 mm × 0.508 mm. The antenna operates on the 5G frequency bands of n257, n258, and n261 with an effective bandwidth of 3.9 GHz covering the range of 26.5 GHz to 30.4 GHz. The suggested MIMO antenna attained a peak gain of 11 dBi and radiation efficiency of 96% at 28 GHz resonating frequency. The MIMO configuration utilized DGS to minimize near-field coupling current at the ground plane, resulting in high port-to-port isolation of >40 dB, and co-pol to X-pol isolation improvements of >9 dB and >19 dB in the boresight direction of E-plane and H-plane at 28 GHz resonating frequency. The antenna’s superior diversity performance is supported by several performance metrics, including ECC(<0.0001), DG(>9.999 dB), CCL(<0.12 bits/s/Hz), MEG (< −3 dB), and TARC. Moreover, the linear transmission property of the proposed MIMO antenna is also validated through the variation of group delay (<0.6 ns) over operating frequency bands in the far-field region.

32-channel wide-bandwidth massive RF photonic combiner based on distributed groups of arrayed photodetectors.

We propose and experimentally demonstrate a low-loss, radio frequency (RF) photonic signal combiner with flat response from 1 GHz to 15 GHz and low group delay variation of 9 ps. The distributed group array photodetector combiner (GAPC) is implemented in a scalable Si photonics platform and has applications in RF photonic systems that rely on combining massive numbers of photonic signals.

RF Multi-Functional Input-Reflectionless Dispersive-Delay Structure With Sharp-Rejection Filtering Using Channelization Techniques

A class of RF multi-functional input-reflectionless dispersive-delay structure (DDS) with linear-type in-band group-delay variation and sharp-rejection bandpass-filtering capability is reported. It exploits a two-branch-channelized/balanced-type circuit with similar low-order reflective DDS units inside its channels, which are connected through input/output 3-dB quadrature wideband couplers. The adopted DDS unit is based on a coupled-resonator network with a frequency-dependent cross-coupling. It introduces a pair of complex transmission zeros (TZs) to shape the intended in-band group-delay profile. Unequal transmission-line-based phase-shifting sections are also inserted at the outputs of both channels. In this manner, an input-absorptive behavior and selectivity enhancement with TZ generation are attained by means of transversal signal-interference techniques at the overall input and output nodes, respectively. Moreover, as the transfer-function phase term of the interference action in transmission is linear with frequency, the total group-delay pattern is defined by the DDS unit of the channels. As practical validation, a 1.5-GHz proof-of-concept microstrip prototype is constructed and tested.

A 120 MHz fast automatic tuning CMOS active-RC lowpass filter

In this paper, a fast automatic cutoff frequency calibrating, CMOS lowpass filter with linear-in-dB tunable gain and constant in-band group delay is presented. The automatic frequency tuning (AFT) circuit can successfully tune the cutoff frequency to 120 MHz with less than 4.7% error. In-band group delay variation is handled using a capacitor process variation detection circuit (CPVD), and the overall tuning time is less than 700 ns. The design is done using STM PD-SOI 130 nm CMOS process, and the supply voltage is 1.2 V with a total power consumption of 21.7 mW. The overall filter provides a programmable linear-in-dB gain of 0.5 dB to 17.6 dB range with a cutoff tuning range of 80 to 180 MHz. The in-band group delay variation is below 500 ps with an adjacent channel ratio (ACR) of 85 dB. The spurious free dynamic range (SFDR) is over 66.6 dBc. The active area of the filter with tuning is 0.171 mm2.

Ultrafast Modulation of THz Waves Based on MoTe2-Covered Metasurface.

The sixth generation (6G) communication will use the terahertz (THz) frequency band, which requires flexible regulation of THz waves. For the conventional metallic metasurface, its electromagnetic properties are hard to be changed once after being fabricated. To enrich the modulation of THz waves, we report an all-optically controlled reconfigurable electromagnetically induced transparency (EIT) effect in the hybrid metasurface integrated with a 10-nm thick MoTe2 film. The experimental results demonstrate that under the excitation of the 800 nm femtosecond laser pulse with pump fluence of 3200 μJ/cm2, the modulation depth of THz transmission amplitude at the EIT window can reach 77%. Moreover, a group delay variation up to 4.6 ps is observed to indicate an actively tunable slow light behavior. The suppression and recovery of the EIT resonance can be accomplished within sub-nanoseconds, enabling an ultrafast THz photo-switching and providing a promising candidate for the on-chip devices of the upcoming 6G communication.

The Design of a Novel 2-42 GHz MEMS True-Time Delay Network for Wideband Phased Array Systems.

This article presents the design method of a compact MEMS switched-line true-time delay line (TTDL) network over a wide frequency range extending from 2 to 42 GHz using TTDL units. The TTDL units, namely the cascading radio frequency micro-electromechanical system (RF MEMS) switches and GCPW, were employed in the proposed TTDL network to improve the delay-bandwidth product (DBW) while maintaining its compact size and low delay variation (DV). For comparison, a theoretical analysis of the RF MEMS switch was performed while observing the switch performance with various top electrodes. The MEMS TTDL network has a compact size of 5 mm × 5 mm, with a maximum delay of 200 ps and a minimum of 30 ps. The maximum insertion loss of 9 states is 10 dB, and the in/out return loss is better than 20 dB across 2-42 GHz. The group delay variations are within ±2.5% for all the delay states over the operating frequency range. To the best of our knowledge, the proposed TTDL network obtains the most control bits among the TTDL networks offered to date.

Design and analysis of novel DGS-loaded low-pass filter with wide stopband

Abstract This article deals with design and development of a novel 7th order low-pass filter with defected ground structures for S-band applications. The proposed LPF structure was comprised of dumbbell shaped interdigital defected ground structures and open stubs as series inductor and shunt capacitor in the pass band. In addition, an equivalent circuit model was derived and optimized to achieve a 3-dB cut off frequency about 4 GHz with a reflection coefficient of better than −20 dB. Moreover, proposed low-pass filter was manufactured on a Rogers RO4003C substrate with a dielectric constant of 3.38, the dissipation factor of 0.0027. The developed LPF has a very flat pass-band with a transmission coefficient less than −0.5 dB and the measured transmission coefficient better than −18 dB in the passband (DC-3.6 GHz). Meanwhile, the prototype has a 20 dB harmonic suppression level in the frequency range from 5.54 GHz up to 43.5 GHz. Furthermore, the measured peak to peak group delay variation was less than 170 ps in the passband. The proposed filter has a very compact size of 195.3 mm2.