dB Gain Research Articles

A 5-W GaN Doherty Amplifier for Ka-Band Satellite Downlink With 4-GHz Bandwidth and 17-dB NPR

This letter presents the design and experimental characterization of a GaN–Si monolithic Doherty power amplifier (PA) for the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Ka$ </tex-math></inline-formula> -band satellite downlink. The fabricated amplifier favorably compares with the current state of the art, achieving from 16.3 to 20.3 GHz (4 GHz, 22% relative bandwidth), a record band to date, 36.6–37.7-dBm output power, 23%–31% power-added efficiency, 18–22-dB gain at saturation, and around 20% power-added efficiency at 6-dB output back-off. At 18.8 GHz, the amplifier shows a noise-to-power ratio higher than 17 dB at all power levels, making it suitable for satellite applications where additional linearization is usually unfeasible.

A self-biased GaN LNA with 30 dB gain and 21 dBm P1dB for 5G communications

Abstract We present a self-biased three-stage GaN-based monolithic microwave integrated circuit low-noise amplifier (LNA) operating between 26 and 29 GHz for 5G mobile communications. The self-biasing circuit, common-source topology with inductive source feedback, and RLC negative feedback loops between gate and drain of the third transistor were implemented to achieve low noise, good port match, high stability, high gain, and compact size. Measurement results show that the LNA has a high and flat gain of 30.5 ± 0.4 dB with noise figure (NF) of 1.65–1.8 dB across the band. The three-stage topology also achieves high linearity, providing the 1 dB compression point output power (P1dB) of 21 dBm in the band. To our knowledge, this combination of NF, gain, and linearity performance represents the state of art of self-biased LNA in this frequency band.

A D-Band Corporate-Feed Gap-Cavity Slot Array Antenna Using Virtual PEC Method

A D-band corporate-feed gap-cavity slot array is proposed with wide bandwidth and high aperture efficiency. The cavity with higher order modes is implemented by using the gap waveguide (WG) technology, namely, a gap cavity. To ensure that the gap cavity is operating with the desired higher order mode over a wide bandwidth, the corporate-feed architecture is applied for uniform excitation and with alternating-phase between adjacent slots. The gap cavity is split into multiple elements by using zero-thickness virtual perfect electric conductor (PEC) walls. With this unique approach, the design, fabrication, and assembly complexities are reduced. For experimental verification, a gap cavity with an 8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 8 slot array is designed in the 120 GHz band, and an E-plane WG feeding network is proposed to excite the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">880</sub> -mode. Two metal fences are introduced on either side of the radiating slot, and an inductive metal pin is introduced below the radiating slot to improve the radiation performance and broaden the bandwidth. The measured impedance matching bandwidth is around 110–144.8 GHz (27.3%). The measured peak gain is 26.22 dBi at 137.64 GHz, and the measured peak aperture efficiency is 86.2% at 115.325 GHz. The 3 dB gain bandwidth is the same as the impedance matching bandwidth.

A Shared-Aperture Dual-Band High-Efficiency Antenna Based on Groove Gap Waveguide

A shared-aperture dual-band antenna at 2.4 GHz Wi-Fi and Ku-bands is proposed in this letter. The antenna in the high-frequency band is featured by a slotted cavity configuration based on the gap waveguide technology. The slotted antenna consists of 3 × 3 slots incorporated into the top metal of the cavity. The periodic structure is loaded into the proposed antenna, which reduces the resonant frequency of the cavity. The top metal of the cavity is enlarged and four shorted screws are loaded, which achieve four half-mode cavities operated in the Wi-Fi band. Two antennas (slotted cavity antenna and dual-band antenna) are designed, fabricated, and tested. Measured results show that a −10 dB impedance bandwidth of 18.3% (13.15–15.8 GHz), a 3 dB gain bandwidth of 17.7% (13.1–15.65 GHz), and a peak gain of 14.8 dBi are realized for the cavity antenna. The impedance bandwidth of the proposed dual-band antenna covers 2.4–2.5 and 13.4–16.2 GHz. A 2 dB gain bandwidth of 16.4% (13.4–15.8 GHz) is realized. Owing to an all-metal structure that exhibits no dielectric loss, the radiation efficiency of the antenna is better than −1 dB in the whole working band. The proposed antenna shows the characteristics of high gain, high efficiency, and low cost, which is suitable for simultaneous satellite communication and Internet of Things applications.

Dual-physical layer high-security encryption scheme for seven-core fiber FPS-OFDM-PON.

This paper proposes an encryption scheme for floating probabilistic shaping orthogonal frequency division multiplexing passive optical networks (FPS-OFDM-PON). Four chaotic sequences are generated by the 4D hyperchaotic model for floating probabilistic shaping (FPS) and bubble sort encryption scheme. An experiment is conducted to demonstrate the transmission of a 70Gb/s (7×10Gb/s) FPS-OFDM-PON signal across a 2km weakly coupled 7-core fiber. The keyspace of the 4D hyperchaotic model reaches 10120. The results show that a 1.82 dB gain in receiver sensitivity compared with the conventional uniform 16QAM-OFDM due to the introduction of FPS. When the system is assaulted by an unlawful receiver, the bit error rate (BER) can still remain at 0.49, successfully assuring the system's security. Due to its good transmission and security performance, the scheme has important application prospects in the future optical access network.

A 1–3 GHz CMOS mixer-first receiver frontend with dual-feedback OTA achieving 306 MHz IF bandwidth, 2.1 dB NF, and 33 dB gain

In this paper, a mixer-first receiver frontend with dual-feedback baseband is proposed. The negative resistive and positive capacitive feedback paths are both applied to single-stage inverter-based operational transconductance amplifier (OTA) with fewer poles, to cover a wide BB frequency range. The [Formula: see text]-path filtering at the RF side and second-order filtering at the BB side inhibit out-of-band blocker interferences. The receiver frontend is designed in 65 nm CMOS. Simulation results display an NF of 2.1 dB across 306 MHz IF bandwidth, and a maximum gain of 33 dB from 1 to 3 GHz LO frequency range. The in-band and out-of-band IIP3 are -13 and 16 dBm, respectively. The receiver core draws 40 mW at 1 GHz LO frequency.

Temperature-Dependent Study on L-Band EDFA Characteristics Pumped at 980 nm and 1480 nm in Phosphorus and Aluminum-Rich Erbium-Doped Silica Fibers

In this paper, wepresent a comparative study on temperature-dependent spectroscopic characteristics and L-band amplifier performance for aluminum-rich erbium-doped fiber (EDF) and in-house fabricated phosphorus co-doped EDF. Different pumping configurations were studied to conclude that the pump wavelength of 980 nm with unequal forward/backward pump powers exhibited better temperature stability. Phosphorus EDF provided 19.4±1.4 dB gain and 4.6±0.2 dB noise figure (NF) from 1575–1615 nm at room temperature (RT), for a multi-channel input signal of −25 dBm in each channel, whereas the aluminum-rich EDF provided 20.3±5.1 dB gain and 5.3±0.8 dB NF. Using a single-channel input signal of −25 dBm at 1625 nm, phosphorus EDF maintained >10 dB gain with a 9.6 dB and 12 dB gain increment than aluminum-rich EDF at RT and −60 °C, respectively. The temperature-dependent gain (TDG) coefficient from 1575–1615 nm was in the range −0.006 to −0.044 dB/°C for phosphorus EDF and 0.011 to −0.023 dB/°C for aluminum-rich EDF, over the temperature range −60 to +80 °C. We propose a hybrid L-band amplifier concatenating aluminum-rich EDF with phosphorus EDF, to suppress the temperature dependence of phosphorus EDF and improve the gain bandwidth restriction of aluminum-rich EDF. The hybrid EDF exhibited multi-channel 20.9±3.9 dB gain and 3.7±0.6 dB NF from 1575–1615 nm at RT. The TDG coefficient of the hybrid EDF remained almost constant from 1585–1615 nm, contributing to a temperature-insensitive gain flatness.

Design of compact highly matched broadband balanced low‐noise amplifier at X‐band using CRLH transmission lines

This article presents broadband balanced low-noise amplifier (LNA) operating at X-band, which uses composite right/left-handed (CRLH) transmission lines as input–output matching networks. Proposed LNA eliminates lumped DC-blocking capacitors and is combined with a hybrid coupler to achieve better stability and matching. Presented CRLH matching technique enhances the matching quality, reduces the overall size and considerably improves the bandwidth and noise performance. The matrix analysis of the CRLH structure is provided to determine the exact dimension of microstrip lines for the highest stable gain and the lowest noise figure (NF). The LNA structure uses a HJFET technology as an active device, which is simulated using an ADS momentum and small-signal scattering parameters provided by the manufacturer. This LNA offers an improved impedance matching and measured the 20 dB S11 band-width of 16% (8.3–9.7GHz), which is in good agreement with simulation. Total area occupied by the fabricated LNA is only 1.7 λ 0 × 0.9 λ 0 @ 8.3GHz. The LNA also provides <1.8 dB NF based on the IEEE standard temperature (16.85 Celsius), and 1 dB gain flatness throughout the entire band along with a 1 dB compression point of −1 dBm and an output third point intercept point of 19.5 dBm. The proposed CRLH-based LNA can be a good candidate for compact receivers and sensors.

The Performance of Orbital Angular Momentum Mode (|l| = 1~3) Amplification Based on Ring-Core Erbium-Doped Fibers

We demonstrated that a ring-core erbium-doped fiber amplifier (RC-EDFA) can support orbital angular momentum (OAM) modes with topological charges (|l| = 1~3). The dependence of the characteristics on the length of the RC-EDF was investigated experimentally, including an investigation of gain and 3 dB gain bandwidth over the whole C band (i.e., 1530~1565 nm). The 3 dB gain bandwidth was improved to 21 nm. At a signal wavelength of 1550 nm, the maximum gain of all signal modes was up to 30.1 dB. Differential modal gain was maintained below approximately 1.3 dB.

Inverse regular perturbation with ML-assisted phasor correction for fiber nonlinearity compensation.

We improve an inverse regular perturbation (RP) model using a machine learning (ML) technique. The proposed learned RP (LRP) model jointly optimizes step-size, gain and phase rotation for individual RP branches. We demonstrate that the proposed LRP can outperform the corresponding learned digital back-propagation (DBP) method based on a split-step Fourier method (SSFM), with up to 0.75 dB gain in a 800 km standard single mode fiber link. Our LRP also allows a fractional step-per-span (SPS) modeling to reduce complexity while maintaining superior performance over a 1-SPS SSFM-DBP.

Reconstruction of a Synchronous Scrambler Based on Average Check Conformity

Channel coding technology is indispensable in digital communication systems. In noncooperative contexts, the identification of the channel codes of the synchronous scrambler is essential. In this paper, a new algorithm that directly uses a soft decision sequence for blind reconstruction of the synchronous scrambler is proposed. First, considering imbalanced signal sources and the principle of scrambling and descrambling the synchronous scrambler, the error-containing equation of the synchronous scrambler is established. Second, the average check conformity is introduced to complete the check relationship detection. Then, based on the statistical characteristics of the average check conformity, the corresponding discrimination threshold is established, and the reconstruction of the feedback polynomial of the synchronous scrambler is completed by traversing the possible primitive polynomials. Finally, the verification equation is determined by the method of subsection optimization, which greatly reduces the number of initial states that need to be traversed; this is critical for scramblers with high-order feedback polynomials (i.e., when the order of the feedback polynomial is greater than 15). Simulations show that the algorithm can effectively reconstruct the synchronous scrambler under imbalanced signal sources. Moreover, the proposed algorithm offers improved performance with about 1–2 dB gain at low signal-to-noise ratios compared with existing methods, and its computational complexity is reasonable.

DESIGN OF MIMO ANTENNA FOR WIRELESS COMMUNICATION APPLICATIONS

The development of a new compact Ultra Wideband (UWB) antenna. The main advantages of the proposed array configuration are that it requires no isolation/decoupling circuit between the elements of the MIMO array. The suggested antenna has an impedance bandwidth of (3.1_10.6) GHz. The antenna dimension (25×58×1.6) mm3. It is based on a simple patch antenna configuration with a simple hexagonal radiator and partial ground. The partial ground is used to improve the reflection coefficient and isolation. A 16.54mm x 9mm ground plane is used. Each element was fed through a 50Ω microstrip transmission line (MTL). The suggested antenna is polarized linearly. It performs admirably at 10.46 GHz, with a gain of 1.77dB, a reflection coefficient of 28.42dB, VSWR approx 1, an envelope correlation coefficient very close to 0 dB, a diversity gain of 10dB, and isolation of 50.44dB, respectively, and suggested antenna's diversity characteristics, such as ECC and diversity gain, are also modeled.

Dual Circularly Polarized 3-D Printed Broadband Dielectric Reflectarray With a Linearly Polarized Feed

A broadband dual circularly polarized (dual-CP) reflectarray based on 3-D printed dielectric materials is proposed in this article. A novel 3-D dielectric array element that enables the broadband linearly polarization (LP) to CP transformation is proposed. The unit cell consists of two orthogonal dielectric cuboids that adjust the phases of the two orthogonal LP waves independently and then combine them into a CP wave. The innovative unit cell design provides an extra degree of freedom in varying the geometries of the array elements in all three dimensions, which enables us to independently control the phases of the two LP waves. This maintains an equal amplitude and 90° phase difference condition across the entire reflectarray surface, realizing a broadband and high gain LP–CP reflectarray. The placement of the feed is also optimized to achieve the highest aperture efficiency. Finally, an off-set reflectarray was designed and fabricated using lost-cost 3-D printing. The reflectarray is able to provide both left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP), with just an LP feed. The measurements agree well with simulated results where the maximum realized gain and directivity at 34 GHz are measured as 27.9 and 28.1 dBi, respectively. The measured 3 dB gain bandwidth and aperture efficiency are 30% and up to 38%, respectively. More importantly, a broad 3 dB axial ratio (AR) bandwidth greater than 40% has been achieved for both LHCP and RHCP, covering almost the entire frequency band of interest, ranging from 26 to 40 GHz.

High Gain Planar Segmented Antenna for mmWave Phased Array Applications

A new high-gain antenna structure is proposed for mmWave 5G and potentially for B5G and 6G applications. The proposed antenna is configured by a planar segmented patch structure that has a radiator size comparable to the conventional patch but achieves more than 3 dB gain enhancement without a help of superstrate stack-up layer. The proposed planar segmented antenna (PSA) induces multiple magnetic currents through multiple segmented conductors, resulting in a strong magnetic field circulation around the conductors. Only one conductor requires an excitation port and each segmented conductor has a shorting pin to synchronize resonance currents. To verify the PSA operation, several prototypes were fabricated at 28 GHz with the identical volume of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.213\,\,\lambda _{0} \times 1.213\,\,\lambda _{0} \times 0.113\,\,\lambda _{0}$ </tex-math></inline-formula> , including the ground plane. The maximum measured impedance bandwidth of the single PSA was 23.1%. Furthermore, the measured maximum antenna gain was 11.5 dBi, whereas the same sized reference patch antenna showed only 6.3 dBi.

Low-Scattering-Cross Section Thinned Phased Array Antenna Based on Active Cancellation Technique

In this article, a novel approach to simultaneously reduce the scattering cross section (SCS) and lower sidelobe level (SLL) as well as the cost of a phased array is proposed, which is a combination of active cancellation and array thinning techniques. Two 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times\,\,10$ </tex-math></inline-formula> planar microstrip phased arrays are designed to validate the proposed concept, including a full array and a thinned array with 20 passive elements. In the thinned array, the passive elements are made use of and terminated at an optimized position with short-circuited loads to generate scattering fields with the required magnitude and phase for cancellation of the scattering fields from the active elements. Furthermore, the positions of the passive elements are optimized by a multiple dimensional discrete particle swarm optimization (MDDPSO) algorithm to achieve a low SLL. It is theoretically predicted that the thinned array features a low SLL below −18 dB in a scan range of ±45°, and SCS reductions of 21 and 9.1 dB in 7.3–10.1 GHz compared to an equal-sized metallic plate and a full array, respectively, which are further verified in simulations and measurements. It is also remarkable that the array cost is reduced due to array thinning, at the cost of an approximately 1 dB gain drop.

Dynamic power allocation algorithm for non-orthogonal multiple access visible light communication system based on polar codes

Visible light communication (VLC) with non-orthogonal multiple access (NOMA) is one of the most promising technologies in wireless optical communication. To improve the system’s performance, we first proposed a NOMA-VLC system based on polar codes. Second, to evaluate the effect of power allocation algorithm on the transmission quality of the NOMA-VLC system based on polar codes, the performance of the NOMA-VLC system under a fixed power allocation algorithm was studied. Finally, considering the time-varying characteristics of wireless channels and users’ service quality, a quality of service (QoS)-based dynamic power allocation algorithm was proposed. In the dynamic power allocation algorithm, we prioritized the QoS of user1 (the user with a lower channel gain) by ensuring that the transmission rate of user1 was always greater than or equal to the minimum transmission rate, and the remaining power was allocated to users with higher channel gains to maximize the total transmission rate. Compared with the NOMA-VLC system without polar codes, simulation results show that user1 obtained 4.1 dB gain for the polar-coded NOMA-VLC system, when the bit error rate was 10 − 4 and α = 1 / 9. And the total transmission rate of the proposed dynamic power allocation algorithm improved by 38.2% compared with the fixed power allocation algorithm with α = 1 / 9 and improved by 48.1% compared with the gain ration power allocation (GRPA) algorithm, when the signal-to-noise ratio was 10 dB. In addition, compared with the fixed power allocation algorithm with α = 1 / 9 and the GRPA algorithm, the outage probability performance of user2 (the user with a higher channel gain) was significantly improved, whereas the outage probability of user1 was basically unchanged under the dynamic power allocation algorithm.

Prior-Knowledge-Guided Deep-Learning-Enabled Synthesis for Broadband and Large Phase Shift Range Metacells in Metalens Antenna

A prior-knowledge-guided deep-learning-enabled (PK-DL) synthesis method is proposed for enhancing the transmission bandwidth and phase shift range of metacells used for the design of metalens antennas. The algorithm of conditional deep convolutional generative adversarial network (cDCGAN) is utilized in the proposed deep-learning (DL) method. Prior knowledge, including well-known fundamental electromagnetic theorems and experience in antenna design, is purposely applied at the early stage of the proposed method to strategically guide and speed up the synthesis. The proposed intelligent method provides the design of pixelated metacells with high degrees of freedom so that the key performance of the synthesized metacells exceeds the existing limit of conventional design methods by generating a rich profusion of cell patterns. For example, the synthesized triple-layer metacell achieves the −1 dB phase shift range of 330° breaking the limit of 308° derived by existing techniques. The proposed synthesis method also provides the additional capability to flexibly control the phase shift not only at the center frequency but also over a frequency range of interest. A Ku-band metalens antenna formed with the synthesized metacells demonstrates the achieved 1 and 3 dB gain bandwidths increase by 52.2% and 42.6%, respectively, compared to the metalens antenna using the well-known Jerusalem cross (JC) metacells. The proposed method extends the capability for the synthesis of metacells and metalens antennas with enhanced performance.

A broadband Fabry–Perot resonator antenna using partially reflecting surface with positive reflection phase gradient

A novel Fabry–Perot resonator antenna with a wide impedance- and gain-bandwidth is proposed in this paper. A wideband aperture-coupled microstrip antenna is used as the primary source, and a single-layer frequency selective surface with a positive reflection phase gradient is designed as a partially reflective surface. To validate the proposed approach, a prototype antenna operating in the X-band is designed, fabricated, and measured. Both simulation and measured results indicate that the proposed antenna exhibits wideband characteristics. The measured impedance bandwidth (|S11| &amp;lt; −10 dB) is 64.4%, ranging from 8.68 to 15.12 GHz. The experiments demonstrate that a 3 dB gain bandwidth of 31.9% from 8.61 to 11.80 GHz with a peak gain of 14.0 dBi at 10 GHz is achieved. In addition, the proposed antenna reveals good directional radiation patterns, low side-lobe level, and low cross-polarization over the whole working band.

Wideband Polarization Rotation Transmitarray Using Arrow-Shaped FSS at W-Band

Based on the passband characteristics of frequency selective surface (FSS), a wideband transmitarray (TA) with linear polarization rotation at W-band is proposed. The middle layer of the unit cell is a pattern of arrow-shaped structure, which can rotate the incoming wave by 90°. A pair of parallel strip polarizers is employed to enhance the polarization conversion efficiency. The prototype of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$25\times 25$ </tex-math></inline-formula> -element TA is fabricated by the standard PCB technology. Within the 3 dB gain bandwidth of 20%, the measured peak gain of 28.7 dB with the corresponding aperture efficiency of 38.2% is achieved. The error analysis is also conducted by comparing the simulation and measurement. The performance of the proposed TA demonstrates that it is a suitable solution for wideband and low-cost applications in the millimeter-wave spectrum.

Phased Antenna Array Synthesis Technique Employing Special Directional Patterns and Demonstrating Improved Performance

Antenna arrays with special, in particular, cosecant directional patterns are widely applied in the current radio engineering systems. When synthesizing antenna array using well-proven techniques, the expected directional pattern is set, with rare exceptions, to the zero values outside the cosecant sector. At the same time, this approach to the directional pattern development is not optimal. It is proposed to supplement the template of the expected directional pattern with the two linear slopes and a constant level area equal to the pattern maximum. A technique for optimizing geometric parameters of the template according to the criterion of the minimum standard deviation of the synthesized directional pattern from the ideal cosecant pattern has been developed. For this deviation, certain restrictions are presupposed: on the magnitude of the maximum pattern deviation in the cosecant sector or/and on the level of side lobes. The method for synthesizing an antenna array by decomposing the directional pattern into Nyquist-Shannon-Kotelnikov series is used while optimization technique is implemented based on the genetic algorithm. The results of the technique approbation show that the use of the optimized template makes it possible to improve the quantitative characteristics of the antenna array directivity. In particular, for the 70° cosecant sector and the 12-element array, a 4 dB gain in maximum pattern deviation is achieved with a simultaneous decrease in the maximum side lobe level by 3 dB. The developed technique can be used for synthesizing a phased antenna array with the directional pattern different from the cosecant one.