Search Results (94)

A broadband, efficient monolithic microwave integrated circuit power amplifier (MMIC PA) in OMMIC’s 0.1 μm GaN-on-Si technology for 5G millimeter-wave communication is presented. This study concentrates on the output matching design, which has an important influence on the PA’s performance. A compact one-order synthesized transformer network (STN) is adopted to match the 50 Ω load to the extracted large-signal output model of the transistor. A dual-objective strategy is developed for parameter optimization, incorporating the impedance transformation trajectory inside the predefined optimal impedance domain (OID) that satisfies the required specifications, with approximation to selected optimal load impedances. By introducing a custom adjustment factor β into the error function, coupled with an automated iterative tuning process based on S-parameter simulations, desired broadband matching results can be rapidly achieved. The proposed two-stage PA occupies a small chip area of only 1.23 mm² and demonstrates good frequency consistency over the 24–31 GHz band. Continuous-wave characterization shows a flat small-signal gain of 19.7 ± 0.5 dB; both the output power (P_out) and the power-added efficiency (PAE) at the 4 dB compression point remain smooth, ranging from 32.3 to 32.7 dBm and 35.5% to 37.8%, respectively. The peak PAE reaches up to nearly 40% at the center frequency. Full article

Compact, broadband, multi-channel RF chips with low loss and high integration are required for high-performance phased-array systems. Presented in this paper is a four-channel, multifunction RF chip operating in the 5–18 GHz frequency range that integrates broadband phase shifting, amplitude control, power amplification, and switching functions. The chip is designed to have flip-chip bonding and stacked gold bumps to enable the compact 3D integration of the GaAs pHEMT and Si-CMOS. To ensure high-density interconnects with minimal parasitic effects, a fan-in redistribution process is implemented. The RF front-end part of this chip, fabricated through a 0.15 µm GaAs pHEMT process, integrates 6-bit digital phase shifters, 6-bit digital attenuators, low-noise amplifiers (LNAs), power amplifiers (PAs), and single-pole double-throw (SPDT) switches. To enhance multi-channel isolation and reduce crosstalk between RF chips and digital circuits, high isolation techniques, including a ground-coupled shield layer in the fan-in process and on-chip shield cavities, are utilized, which achieve isolation levels greater than 41 dB between adjacent RF channels. The measurement results demonstrate a reception gain of 0 dB with ±0.6 dB flatness, an NF below 11 dB, and transmit gain of more than 10 dB, with a VSWR of below 1.6 over the entire 5–18 GHz frequency band. The 6-bit phase shifter achieves a root mean square (RMS) phase error below 2.5° with an amplitude variation of less than 0.8 dB, while the 6-bit attenuator exhibits an RMS attenuation error of below 0.5 dB and a phase variation of less than 7°. The RF and digital chips are heterogeneously integrated using flip-chip and fan-in technology, resulting in a compact chip size of 6.2 × 6.2 × 0.33 mm³. These results validate that this is a compact, high-performance solution for advanced phased-array radar applications. Full article

This paper presents a class-D outphasing power amplifier (PA) that incorporates a non-isolating balun combiner employing a 180° phase shift. Both isolating and non-isolating outphasing combiners are analyzed for signal restoration and combining efficiency. The proposed non-isolating balun combiner employing the 180° phase shift was experimentally evaluated and compared with a commercial isolating Wilkinson combiner. When two constant-envelope signals derived from a 10 MHz long-term evolution (LTE) signal are applied to the inputs of the outphasing combiners, both combiners demonstrate successful signal reconstruction. The measured adjacent channel leakage ratios (ACLRs) are −47 dBc for the Wilkinson combiner and −46 dBc for the proposed balun combiner. At 6 dB power back-off (PBO), the proposed balun combiner achieves a combining efficiency of 85.1%, representing an improvement of nearly 60% over the Wilkinson combiner. With a center frequency of 650 MHz, targeting 5G FR1 applications, a class-D outphasing PA was designed in a 28 nm CMOS process using the measured S-parameter data from both outphasing combiners. Simulation results show that the class-D outphasing PA incorporating the proposed balun combiner achieves a peak drain efficiency (DE) of 82.9% with an output power of 17.7 dBm. At 6 dB PBO, the DE reaches 61%, which is approximately 37% higher than that of the outphasing PA using the Wilkinson combiner. Moreover, the designed outphasing PA supports broadband operation over the 360–860 MHz range. Full article

To expand the operating frequency bands of the Doherty power amplifier (DPA), this paper proposes a dual-mode multi-band DPA design method employing impedance-and-phase constrained optimization based on reciprocal gate bias. By introducing the concept of reciprocal gate bias, the operating mode is switched by swapping the gate biases of the carrier and peaking amplifiers of the DPA, which effectively extend the operating frequency band without modifying the load modulation network. Furthermore, multiple impedance constraint circles are used to cover the optimum load impedance region obtained from the load-pull simulation. And, the phases required for impedance transformation network (ITN) across the multi-band are determined based on the impedance transformation requirements when the DPA operates in power back-off (PBO) state and saturation state. Then, the ITNs that satisfy the impedance and phase constraints can be optimized and designed. For verification, a dual-mode multi-band DPA, operating in Mode I at 1.96–2.10 GHz and 2.75–2.86 GHz, and in Mode II at 2.49–2.61 GHz and 3.20–3.36 GHz, is designed and fabricated. Measured results show that the output power of the DPA exceeds 43 dBm with corresponding saturated drain efficiencies (DEs) higher than 50% in both modes. For 6 dB PBO, the DEs are 49.4–55.7% and 49.8–51.7% in Mode I, whereas in Mode II, they range from 51.2% to 52.4% and from 50.4% to 53.5%. Moreover, good linearity can be achieved after linearization for 20 MHz modulated signals. Full article

A polarization-maintaining all-fiber laser source based on a nonlinear amplifying loop mirror with broadband operation (64 nm) around 1920 nm is demonstrated. The oscillator can generate 66 pJ up-chirped dissipative soliton pulses at a repetition rate of 22.8 MHz with a high polarization extinction ratio of 17 dB. By adding a polarization controller to the polarization-maintaining dispersion-compensating fiber, the filter behavior can be adjusted allowing for the tuning of the emission to a center wavelength of 1878 nm, 1907 nm, and 1926 nm. Using an all-polarization-maintaining single-mode fiber amplifier with anomalous dispersion, the pulses are amplified to 0.9 nJ and compressed to a near Fourier-limited pulse duration of 170 fs with a peak power of 4.3 kW. Such all-fiber-based sources are attractive due to their compact size, high beam quality, and good environment stability. Full article

The core-division-multiplexed (CDM) transmission technique utilizing uncoupled multi-core fiber (MCF) is considered a promising candidate for next-generation long-haul optical transport networks (OTNs) due to its high-capacity potential. For the field implementation of MCF, it is of great significance to explore its long-haul transmission capability using high-speed OTN transceivers over deployed MCF cable. In this paper, we investigate the real-time long-haul transmission capability of a deployed seven-core MCF cable using commercial 138-Gbaud 400 Gb/s backbone OTN transceivers with a dual-polarization quadrature phase shift keying (DP-QPSK) modulation format. Thanks to the highly noise-tolerant DP-QPSK modulation format enabled by the high baud rate, a real-time 256 Tb/s transmission over a 990.64 km (14 × 70.76 km) deployed seven-core fiber cable with more than 600 fusion splices is field demonstrated for the first time, which achieves a real-time capacity–distance product of 221.9 Pb/s∙km. Specifically, the long-haul CDM transmission is simulated by cascading the fiber cores of two segments of 70.76 km seven-core fibers. And dynamic gain equalizers (DGEs) are utilized to mitigate the impacts of stimulated Raman scattering (SRS) and the uneven gain spectra of amplifiers in broadband transmissions by equalizing the power of signals with different wavelengths. This field trial demonstrates the feasibility of applying uncoupled MCF in long-haul OTN transmission systems and will contribute to its field implementation in terrestrial fiber cable systems. Full article

The ASE (Amplified Spontaneous Emission) light source, based on erbium-doped fiber (EDF), is a broadband light source with advantages such as high power, excellent temperature stability, and low coherent light generation. It is widely used in the field of fiber optic sensing. However, traditional ASE sources suffer from temperature sensitivity and low efficiency, which can compromise the accuracy and stability of the output light’s average wavelength. This study focuses on optimizing the erbium-doped fiber (EDF) to improve the temperature stability and efficiency of the ASE light source. Through simulations, we found that the appropriate doping concentration and length of the EDF are key factors in enhancing the stability and efficiency of the ASE source. Inorganic metal chloride vapor-phase doping combined with an improved chemical vapor deposition process was used to fabricate the erbium-doped fiber, ensuring low background loss, minimal OH⁻ absorption, and uniform distribution of the erbium ions in the core of the fiber. The optimized EDFs were integrated into the ASE source, achieving a power conversion efficiency of 53.6% and a temperature stability of 0.118 ppm/°C within the temperature range of −50 °C to 70 °C. This study offers a practical approach for improving the performance of ASE light sources and advancing the development of high-precision fiber optic sensing technologies. Full article

Multi-band optical communication presents a promising avenue for the significant enhancement of fiber-optic transmission capacity without incurring additional costs related to new cable deployment via the utilization of the bandwidth beyond the established C&L bands. However, a big challenge in its field implementation lies in the high cost and suboptimal performance of optical amplifiers, stemming from the underdeveloped state of rare-earth-doped fiber-optic amplifier technologies for these bands. Fiber-optic parametric amplifiers provide an alternative for wideband optical amplification, yet their low power efficiency limits their practical use in the field. In this paper, we study a hybrid optical amplifier that combines the excellent power efficiency of rare-earth-doped amplifiers with broadband wavelength conversion capability of parametric amplifiers. It uses wavelength converters to shift signals between the S- and L-bands, amplifying them with an L-band erbium-doped fiber amplifier, and converting them back to the S-band. We experimentally demonstrate such a hybrid S-band amplifier, characterize its performance with 16-QAM input signals, and evaluate its power efficiency and four-wave-mixing-induced crosstalk. This hybrid approach paves the way for scalable expansion of optical communication bands without waiting for advancements in rare-earth-doped amplifier technology. Full article

A tunable high-power 60 MHz ultraviolet pulse laser directly produced by the extra-cavity fourth-order harmonic generation of a self-similar amplification infrared pulse laser is reported in this study. Utilizing the self-similar pulse evolution and the self-phase modulation in a self-similar amplifier, the system generates a 58.9 W pulse train with a spectral half-width of 85.4 nm, corresponding to a pulse duration of 36 fs. To obtain the ultraviolet pulses from the infrared pulses, a single-pass frequency quadrupling system comprising two cascaded β-BBOs was used. The ultraviolet spectra can be tuned within a spectral range of 253.6 to 275 nm owing to the broadband infrared seed spectra. The maximum ultraviolet average power of 1.44 W was achieved at 275 nm with spectral half-width and an infrared-to-ultraviolet efficiency of 1.1 nm and 2.44%, respectively. To the best of our knowledge, this is the first demonstration of tunable high-power ultraviolet pulse generation from a self-similar amplification Yb-fiber laser. Full article

This paper uses the non-integer ratio coaxial line impedance transform matching method to design a wideband RF power amplifier. The motivation for the research stems from the limitations of the fixed conversion ratio of traditional impedance converters at RF frequencies and the challenges of low-frequency performance degradation. A fixed conversion ratio and low-frequency performance often limit traditional impedance matching methods. The model enables flexible and efficient wideband impedance matching, covering a wide frequency range of 2–650 MHz. The results show that the power amplifier has an output power of more than 48.5 dBm, a gain of more than 16 dB, and a drain efficiency (DE) of more than 55% in the frequency band range of 2–650 MHz, which is superior to similar designs in terms of low-frequency performance and bandwidth. Full article

Millimeter-wave (mm-Wave) phased array systems need to meet the transmitter (Tx) equivalent isotropic radiated power (EIRP) requirement, and that depends mainly on the design of two key sub-components: (1) the antenna array and (2) the Tx power amplifier (PA) in the front-end-modules (FEMs). Simulations using an electromagnetic (EM) solver carried out in Cadence AWR with AXIEM suggest that for two uniform square patch antenna arrays at 24 GHz, the 4 element array has ~6 dB lower antenna gain and twice the half power beam width (HPBW) compared to the 16 element array. We also present measurements and post-layout parasitic-extracted (PEX) EM simulation data taken on two broadband mm-Wave PAs designed in our lab that cover the key portions of the fifth-generation (5G) FR2-band (i.e., 24.25–52.6 GHz) that lies between the super-high-frequency (SHF, i.e., 3–30 GHz) band and the extremely-high-frequency (EHF, i.e., 30–300 GHz) band: one designed in a 22 nm fully depleted silicon on insulator (FD-SOI) CMOS process, and the other in an advanced 40 nm Gallium Nitride (GaN) high-electron-mobility transistor (HEMT) process. The FD-SOI PA achieves saturated output power (P_OUT,SAT) of ~14 dBm and peak power-added efficiency (PAE) of ~20% with ~14 dB of gain and 3 dB bandwidth (BW) from ~19.1 to 46.5 GHz in measurement, while the GaN PA achieves measured P_OUT,SAT of ~24 dBm and peak PAE of ~20% with ~20 dB gain and 3 dB BW from ~19.9 to 35.2 GHz. The PAs’ measured data are in good agreement with the PEX EM simulated data, and 3rd Watt-level GaN PA design data are also presented, but with simulated PEX EM data only. Assuming each antenna element will be driven by one FEM and each phased array targets the same 65 dBm EIRP, millimeter wave (mm-Wave) antenna arrays using the Watt-level GaN PAs and FEMs are expected to achieve roughly 2× wider HPBW with 4× reduction in the array size compared with the arrays using Si FEMs, which shall alleviate the thorny mm-Wave line-of-sight (LOS)-blocking problems significantly. Full article

A broadband 28 nm complementary metal–oxide–semiconductor (CMOS) power amplifier was implemented using a distributed amplification design. To develop a model library for high-frequency design, various test patterns for active and passive elements were fabricated and compared through measurements. As a result, a symmetrical n-channel field-effect transistor (NFET) was used as the active device, and a co-planar waveguide (CPW) with floating bottom metal layers was chosen as the transmission line for the passive element. These choices demonstrated superior radio frequency (RF) characteristics at high frequencies compared to other device candidates. Furthermore, to address the low breakdown voltage of CMOS, a triple-stacked FET structure was designed as the gain cell of the distributed power amplifier (DPA). The fabricated DPA showed a maximum small-signal gain of 22 dB and a minimum of 10 dB from DC to 56 GHz, with a maximum saturated output power of 20 dBm and a minimum of 13 dBm from 1 to 39 GHz. Notably, these results were achieved on the first attempt by designing solely based on measurement data from the test patterns. Full article

This paper presents a comprehensive study on the design and performance of a high-power amplifier (PA) covering a broad frequency band from 0.1 to 4.8 GHz. Leveraging a 10 W GaN device, the amplifier achieves output power levels surpassing 10 W across the entire frequency band. Furthermore, the power-added efficiency (PAE) of the amplifier ranges from 47% to 59%, indicating its energy-efficient operation. With consistent gain characteristics varying between 7 and 15 dB, the design ensures reliable signal amplification for diverse applications. Notably, the approach introduces a simplified output matching network based on an LC network, prioritizing practicality without sacrificing performance. Additionally, comprehensive guidance is provided on utilizing the Smith chart for streamlined amplifier design, enabling engineers with an accessible methodology. Through a meticulous analysis, this work contributes to advancing the field of high-power amplification, offering enhanced performance and usability for next-generation wireless communication systems. Full article

Polymer fibers are considered ideal transmission media for all-optical networks, but their high intrinsic loss significantly limits their practical use. Quantum dot-doped polymer fiber amplifiers are emerging as a promising solution to this issue and are becoming a significant focus of research in both academia and industry. Based on the properties of CdSe/ZnS quantum dots and PMMA material, this study experimentally explores three fabrication methods for CdSe/ZnS quantum dots-doped PMMA fibers: hollow fiber filling, melt-drawing, and melt extrusion. The advantages and disadvantages of each method and key issues in fiber fabrication are analyzed. Utilizing the CdSe/ZnS quantum dots-doped PMMA fibers that were fabricated, we theoretically analyzed the key factors affecting gain performance, including fiber length, quantum dots doping concentration, and signal light intensity. Under the conditions of 1.5 W power and 445 nm laser pumping, a maximum on-off gain of 16.2 dB was experimentally achieved at 635 nm. Additionally, using a white light LED as the signal source, a broadband on-off gain with a bandwidth exceeding 70 nm and a maximum gain of 12.4 dB was observed in the 580–650 nm range. This research will contribute to the development of quantum dots-doped fiber devices and broadband optical communication technology, providing more efficient solutions for future optical communication networks. Full article

A 30~60 GHz broadband down-conversion mixer driven by low local oscillator (LO) power is presented. The down-conversion mixer utilizes an input signal coupling technique based on the Marchand balun to achieve broadband operation and achieves low LO power drive and low DC power consumption through the use of a weak inversion bias with Gilbert switching devices. The broadband conversion of single-ended to differential signals is achieved using the Marchand balun with compensation lines, and an equivalent circuit analysis is performed. For the intermediate frequency (IF) output, a self-biased IF trans-impedance amplifier with current reusing and an active IF balun structure are used to achieve signal amplification and single-ended signal output. Test results show that the proposed mixer achieves a conversion gain of −1.2 to 6.4 dB in an IF output bandwidth of 0.1 to 5 GHz at radio frequency (RF) input frequencies of 30 to 60 GHz and LO driving power of −10 dBm. The DC power consumption of the core mixing unit of the proposed mixer is 4.8 mW, and the DC power consumption including the IF amplifier is 28.3 mW. The proposed mixer uses a 65 nm CMOS technology with a chip area of 0.26 mm². Full article