This paper proposes a new multi-port amplifier configuration that employs feed-forward techniques. In general, a multi-port amplifier is used as a transponder in a satellite transmitter. A multi-port amplifier comprises an N-in N-out input-side matrix network, N amplifiers, and an N-in N-out output-side matrix network. Based on this configuration, other undesired ports leak power to the desired port in a multi-port amplifier. If the power amplifier of a cellular base station uses a multi-port amplifier, the power leakage from the other ports causes degradation in the error vector magnitude. The proposed configuration employs N-parallel feed-forward amplifiers with a multi-port amplifier as the main amplifier. The proposed configuration drastically reduces the power leakage using the employed feed-forward techniques. An experimental 2-GHz band four-in four-out multi-port amplifier is constructed and tested. It achieves the leakage power level of -58 dB, a gain deviation of less than 0.05 dB, and a phase deviation of less than 0.45 deg. with the maximum power of 35 dBm over a 20-MHz bandwidth with the center frequency 2.14 GHz at room temperature. The experimental multi-port amplifier reduces the leakage power level by approximately 30 dB compared to that for a multi-port amplifier without the feed-forward techniques. The proposed configuration can be applied to power amplifiers in cellular base stations.

This paper presents improvement of port-to-port isolation characteristics of a linearly dual-polarized dual-band and wideband multi-ring microstrip antenna (MR-MSA) fed by two L-probes. The linearly dual-polarized dual-band and wideband MR-MSA consists of two circular ring patches and two L-probes arranged in a multi-layered dielectric substrate. By using a thick substrate for the L-probe and arranging two ring patches as radiation elements, the proposed antenna operates wideband and dual-band characteristics. Furthermore, by arranging two L-probes at the orthogonal positions, the proposed antenna can radiate dual linear polarizations. In this paper, for improving port-to-port isolation characteristics of the linearly dual-polarized dual-band and wideband MR-MSA fed by two L-probes, a via connected to the ground plane at the center of the radiation elements is arranged. The fractional bandwidths below -10dB reflection obtained by the simulation of the MR-MSA with the via were 17.0% and 14.4%. Furthermore, the simulated isolation characteristics were more than 21.0dB and 17.0dB in the two bands. Improvement of the isolation characteristics between two ports as well as the dual-band and wideband performance of the proposed MR-MSA with the via were confirmed by the simulation and the measurement.

This work proposes a design methodology that saves the power dissipation under voltage over-scaling (VOS) operation. The key idea of the proposed design methodology is to combine critical path isolation (CPI) and bit-width scaling (BWS) under the constraint of computational quality, e.g., Peak Signal-to-Noise Ratio (PSNR) in the image processing domain. Conventional CPI inherently cannot reduce the delay of intrinsic critical paths (CPs), which may significantly restrict the power saving effect. On the other hand, the proposed methodology tries to reduce both intrinsic and non-intrinsic CPs. Therefore, our design dramatically reduces the supply voltage and power dissipation while satisfying the quality constraint. Moreover, for reducing co-design exploration space, the proposed methodology utilizes the exclusiveness of the paths targeted by CPI and BWS, where CPI aims at reducing the minimum supply voltage of non-intrinsic CP, and BWS focuses on intrinsic CPs in arithmetic units. From this key exclusiveness, the proposed design splits the simultaneous optimization problem into three sub-problems; (1) the determination of bit-width reduction, (2) the timing optimization for non-intrinsic CPs, and (3) investigating the minimum supply voltage of the BWS and CPI-applied circuit under quality constraint, for reducing power dissipation. Thanks to the problem splitting, the proposed methodology can efficiently find quality-constrained minimum-power design. Evaluation results show that CPI and BWS are highly compatible, and they significantly enhance the efficacy of VOS. In a case study of a GPGPU processor, the proposed design saves the power dissipation by 42.7% with an image processing workload and by 51.2% with a neural network inference workload.

With the arrival of 5G and the popularity of smart devices, indoor localization technical feasibility has been verified, and its market demands is huge. The channel state information (CSI) extracted from Wi-Fi is physical layer information which is more fine-grained than the received signal strength indication (RSSI). This paper proposes a CSI correction localization algorithm using DenseNet, which is termed CorFi. This method first uses isolation forest to eliminate abnormal CSI, and then constructs a CSI amplitude fingerprint containing time, frequency and antenna pair information. In an offline stage, the densely connected convolutional networks (DenseNet) are trained to establish correspondence between CSI and spatial position, and generalized extended interpolation is applied to construct the interpolated fingerprint database. In an online stage, DenseNet is used for position estimation, and the interpolated fingerprint database and K-nearest neighbor (KNN) are combined to correct the position of the prediction results with low maximum probability. In an indoor corridor environment, the average localization error is 0.536m.

This paper presents an X-band power-combined pulsed high power amplifier (HPA) based on the low insertion loss waveguide combiner. Relationships between the return loss and isolation of the magic Tee (MT) have been analyzed and the accurate design technique is given. The combination network is validated by the measurement of a single MT and a four-way passive network, and the characterization of the combined HPA module is designed, fabricated and discussed. The HPA delivers 200W output power with an associated power-added efficiency close to 40% within the frequency range of 7.8 GHz to 12.3 GHz. The combination efficiency is higher than 93%.

Long-range radars (LRRs) for higher level autonomous driving (AD) will require more antennas than simple driving assistance. The point at issue here is 50-60% of the LRR module area is used for antennas. To miniaturize LRR modules, we use horn and lens antenna with highly efficient gain. In this paper, we propose two high-density implementation techniques for radio-frequency (RF) front-end using horn and lens antennas. In the first technique, the gap between antennas was eliminated by taking advantage of the high isolation performance of horn and lens antennas. In the second technique, the RF front-end including micro-strip-lines, monolithic microwave integrated circuits, and peripheral parts is placed in the valley area of each horn. We fabricated a prototype LRR operating at 77 GHz with only one printed circuit board (PCB). To detect vehicles horizontally and vertically, this LRR has a minimum antenna configuration of one Tx antenna and four Rx antennas placed in 2×2 array, and 30 mm thickness. Evaluation results revealed that vehicles could be detected up to 320 m away and that the horizontal and vertical angle error was less than +/- 0.2 degrees, which is equivalent to the vehicle width over 280 m. Thus, horn and lens antennas implemented using the proposed techniques are very suitable for higher level AD LRRs.

There are enlarged requirements of millimeter-wave beamforming phased-array transceivers and high-order modulation multi-input multi-output (MIMO) transceivers. High-performance integrated RF switches are regarded as one of the most critical components for those transceivers to support signal channel distribution and path redundancy. This paper introduces a CMOS high-isolation and low-loss RF switch with a novel switched parallel LC resonance network. The proposed single-pole double-throw (SPDT) RF switch realizes 68dB port isolation and 1.0dB insertion loss with an active area of 0.034mm2. The SPDT RF switch is composed of two series-shunt transistor pairs with body-floating technology and a switched parallel LC network. The network uses a turned-off series transistor to resonate out off-capacitance Coff. The measured output third-order intercept (OIP3) is higher than 21dBm. The proposed SPDT RF switch maintains return losses of all working ports less than 10dB from 8GHz to 20GHz. The high-performance SPDT RF switch is fabricated in standard 65-nm CMOS technology.

In this paper, we propose four optimization methods during the Register Transfer Level (RTL) conversion from synchronous RTL models into asynchronous RTL models. The modularization of data-path resources and the use of appropriate D flip-flops reduce the circuit area. Fixing the control signal of the multiplexers and inserting latches for the data-path resources reduce the dynamic power consumption. In the experiment, we evaluated the effect of the proposed optimization methods. The combination of all optimization methods could reduce the energy consumption by 21.9% on average compared to the ones without the proposed optimization methods.

This paper describes the theoretical analysis and experimental verification of a new type high-isolation surface-acoustic-wave (SAW) duplexer by using a SAW on-chip compensation circuit designed to cancel the signal of the main SAW filter at an attenuation frequency band. First, a numerical analysis based on the interference of waves propagating parallel waveguides is applied to clarify the relation between the absolute improvement value of the filter's attenuation level and cancel conditions. Then, the feasibility of the SAW compensation circuit using the double mode SAW (DMS) resonator filter are studied in both a circuit simulation and experiment. As a result, a 10-30 dB attenuation improvement was achieved within a band range of several tens of MHz using electrical characteristics of the lower side slope in the DMS resonator filter, and that it agrees well with the result obtained by numerical analysis. These results are expected to be useful for current and future mobile systems wants higher receiver sensitivity.

In the context of resource isolation for network slicing, this paper introduces two resource allocation methods especially for the radio access network (RAN) part. Both methods can be implemented by slight modification of the ordinary packet scheduling algorithm such as the proportional fairness algorithm, and guarantee resource isolation by limiting the maximum number of resource blocks (RBs) allocated to each slice. Moreover, since both methods flexibly allocate RBs to the entire system bandwidth, there are cases in which the throughput performance is improved compared to when the system bandwidth is divided in a static manner, especially in a frequency selective channel environment. Numerical results show the superiority of these methods to dividing simply the system bandwidth in a static manner, and show the difference between the features of the methods in terms of the throughput performance of each slice.

This study presents the design of a phase correlator for a digital frequency discriminator (DFD) that operates in the 2.0-6.0GHz frequency range. The accuracy of frequency discrimination as determined by the isolation of the correlator mixer was analyzed, and LO-RF isolation was found to have a significant effect on the frequency discrimination error by deriving various analytic equations related to the LO-RF isolation and phase performance. We propose a novel technique (phase sector compensation) to improve the accuracy of frequency discrimination. The phase sector compensation technique improved phase error by canceling the DC offset of the I and Q signals for only the frequency bands where the mixer's LO-RF isolation was below a specified limit. In the 2.0-6.0GHz range, the phase error of the designed phase correlator was decreased from 4.57° to 4.23° (RMS), and the frequency accuracy was improved from 1.02MHz to 0.95MHz (RMS). In the 4.8-6.0GHz range, the RMS phase error was improved from 5.59° to 4.12°, the frequency accuracy was improved from 1.24MHz to 0.92MHz, and the performance of the DFD correlator was improved by 26.3% in the frequency sector where LO-RF isolation was poor. Overall, the DFD correlator performance was improved by LO leakage compensation.

This paper proposes a multiway power divider for wideband (4:1) beamforming arrays. The divider's input reflection characteristic (S11) is achieved using a multisection stepped-impedance transformer. Moreover, the divider's isolation (S32) bandwidth is increased by incorporating inductors and capacitors in addition to the conventional resistor only isolation networks of the divider. The analysis of the proposed divider and comparison with the previous research model was conducted with four-way configuration. A prototype of a wideband eight-way power divider is fabricated and measured. The measured fractional bandwidth is about 137% from 1.3 to 6.8GHz with the -10dB criteria of input reflection (S11), output reflection (S22) and isolation (S32) simultaneously.

We introduce the design and deployment of the latest version of the VNode infrastructure, VNode-i. We present new extended VNode-i functions that offer high performance and provide convenient deep programmability to network developers. We extend resource abstraction to the transport network and achieve highly precise slice measurement for resource elasticity. We achieve precise resource isolation for VNode-i. We achieve coexistence of high performance and programmability. We also enhance AGW functions. In addition, we extend network virtualization from the core network to edge networks and terminals. In evaluation experiments, we deploy the enhanced VNode-i on the JGN-X testbed and evaluate its performance. We successfully create international federation slices across VNode-i, GENI, and Fed4FIRE. We also present experimental results on video streaming on a federated slice across VNode-i and GENI. Testbed experiments confirm the practicality of the enhanced VNode-i.

Even though cloud users want to keep their data on clouds secure, it is not easy to protect the data because cloud administrators could be malicious and hypervisor could be compromised. To solve this problem, hardware-based memory isolation schemes have been proposed. However, the data in virtual storage are not protected by the memory isolation schemes, and thus, a guest OS should encrypt the data. In this paper, we address the problems of the previous schemes and propose a hardware-based storage isolation scheme. The proposed scheme enables to protect user data securely and to achieve performance improvement.

In recent years, real-time streaming has become widespread as a major service on the Internet. However, real-time streaming has a strict playback deadline. Application level multicasts using multiple distribution trees, which are known as forests, are an effective approach for reducing delay and jitter. However, the failure or departure of nodes during forest-based multicast transfer can severely affect the performance of other nodes. Thus, the multimedia data quality is degraded until the distribution trees are repaired. This means that increasing the speed of recovery from isolation is very important, especially in real-time streaming services. In this paper, we propose three methods for resolving this problem. The first method is a random-based proactive method that achieves rapid recovery from isolation and gives efficient “Randomized Forwarding” via cooperation among distribution trees. Each node forwards the data it receives to child nodes in its tree, and then, the node randomly transferring it to other trees with a predetermined probability. The second method is a reactive method, which provides a reliable isolation recovery method with low overheads. In this method, an isolated node requests “Continuous Forwarding” from other nodes if it detects a problem with a parent node. Forwarding to the nearest nodes in the IP network ensures that this method is efficient. The third method is a hybrid method that combines these two methods to achieve further performance improvements. We evaluated the performances of these proposed methods using computer simulations. The simulation results demonstrated that our proposed methods delivered isolation recovery and that the hybrid method was the most suitable for real-time streaming.

One key requirement for achieving network virtualization is resource isolation among slices (virtual networks), that is, to avoid interferences between slices of resources. This paper proposes two methods, per-slice shaping and per-link policing for network-resource isolation (NRI) in terms of bandwidth and delay. These methods use traffic shaping and traffic policing, which are widely-used traffic control methods for guaranteeing QoS. Per-slice shaping utilizes weighted fair queuing (WFQ) usually applied to a fine-grained flow such as a flow from a specific server application to a user. Since the WFQ for fine-grained flows requires many queues, it may not scale to a large number of slices with a large number of virtual nodes. Considering that the purpose of NRI is not thoroughly guaranteeing QoS but avoiding interferences between slices, we believe per-slice (not per virtual link) shaping satisfies our objective. In contrast, per-link policing uses traffic policing per virtual link. It requires less resource and achieves less-strict but more-scalable isolation between hundreds of slices (500 to 700 slices in estimation). Our results show that both methods perform NRI well but the performance of the former is better in terms of delay. Accordingly, per-slice shaping (with/without policing) is effective for delay-sensitive services while per-link policing may be sufficiently used for the other types of services.

The authors propose a new method of controlling the isolation of an RF splitter. In the proposed method, a bias current is superimposed on an RF signal to change the permeability of the ferrite core used in the splitter's transformer. By doing this, the splitter isolation can be controlled. Experimental results have shown that superimposing a bias current of 500 mA improves device isolation by about 5 dB without affecting the loss characteristics.

A high directivity microstrip coupler suppressing leak coupling with a cancellation circuit of a Wilkinson divider is presented. The presented coupler utilizes a cancellation circuit between a coupling port and an isolation port of the conventional microstrip coupler to enhance the isolation. The cancellation circuit consists of the Wilkinson divider, the multistage attenuator, and the phase offset line. The frequency to enhance the isolation is controlled by the attenuators. As the directivity is improved without the modification of the conventional coupler, the cancellation circuit can be applied to the fabricated conventional couplers. The measured directivity of the presented 1/18 λ coupler is improved from 4.8 dB to 43.0 dB at 2.6 GHz, compared with the conventional 1/4 λ coupler with -20 dB coupling. Simultaneously, the 27.4% relative bandwidth with the 20 dB directivity is achieved.

In this paper, an indoor repeater antenna with high isolation for WCDMA application is proposed. The designed repeater has very small separation of 20 mm between the donor and server antennas. The antenna has two resonance frequencies to cover the WCDMA band from 1.92 GHz to 2.17 GHz. The fabricated antenna has VSWR below 1.5, gain over 8 dBi, and isolation between server and donor antennas less than -80 dB in the WCDMA band.

This paper presents the dual-band bandpass filters (BPFs) design composed of λ/2 and symmetrically/asymmetrically paired λ/4 stepped impedance resonators (SIRs) for the WLAN applications. The filters cover both the operating frequencies of 2.45 and 5.2 GHz. The dual-coupling mechanism is used in the filter design to provide alternative routes for signals of selected frequencies. A prototype filter is composed of λ/2 and symmetrical λ/4 SIRs. The enhanced wide-stopband filter is then developed from the filter with the symmetrical λ/4 SIRs replaced by the asymmetrical ones. The asymmetrical λ/4 SIRs have their higher resonances frequencies isolated from the adjacent I/O SIRs and extend the enhanced filter an upper stopband limit beyond ten time the fundamental frequency. Also, the filter might possess a cross-coupling structure which introduces transmission zeros by the passband edges to improve the signal selectivity. The tapped-line feed is adopted in this circuit to create additional attenuation poles for improving the stopband rejection levels. Experiments are conducted to verify the circuit performance.