Noise Figure Degradation Research Articles

Comparison of hot carrier-induced RF performance degradation in H-gate and T-gate SOI MOSFETs

The RF performance degradation of silicon-on-insulator (SOI) MOSFETs with H-gate and T-gate structures after hot carrier stressing has been investigated. Our experimental results show that the RF performance degradation is more significant than the dc performance degradation after hot carrier stressing. Also, the degradation of the H-gate device is more significant than that of the T-gate device due to the higher drain current. Since the degradation of minimum noise figure is the most significant, the hot carrier effects should be taken into account in the design of LNA using the H-gate device although its RF performance is better than that of the T-gate device.

An ultra-wideband CMOS low noise amplifier for 3-5-GHz UWB system

An ultra-wideband (UWB) CMOS low noise amplifier (LNA) topology that combines a narrowband LNA with a resistive shunt-feedback is proposed. The resistive shunt-feedback provides wideband input matching with small noise figure (NF) degradation by reducing the Q-factor of the narrowband LNA input and flattens the passband gain. The proposed UWB amplifier is implemented in 0.18-/spl mu/m CMOS technology for a 3.1-5-GHz UWB system. Measurements show a -3-dB gain bandwidth of 2-4.6GHz, a minimum NF of 2.3 dB, a power gain of 9.8 dB, better than -9 dB of input matching, and an input IP3 of -7dBm, while consuming only 12.6 mW of power.

Gain clamping in double‐pass L‐band EDFA using a ring resonator

AbstractA gain‐clamped long‐wavelength‐band erbium‐doped fiber amplifier (L‐band EDFA) based on a ring‐laser cavity is demonstrated using two C/L‐band wavelength‐selective couplers. This new design provides improved gain characteristics and high tuneability. The gain is clamped at 11.5 dB with a gain variation of less than 0.1 dB from an input‐signal power of −40 to −6 dBm by setting the variable attenuation setting (VOA) at 8 dB. Also, the clamped‐gain level can be controlled to be in the range from 4.7 to 21.3 dB by varying the VOA settings from 0 to 24 dB. However, the proposed gain‐clamped amplifier suffers from noise‐figure degradation, as compared to the open‐ring amplifier, due to the intense ring‐laser light, which counter‐propagates through the EDF. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 484–486, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20509

Effects of hot carrier stress on the RF performance in SOI MOSFETs

This paper presents new experimental results on the DC hot carrier stress effects on the RF performance of SOI MOSFETs. The RF performance degradation in terms of cut-off frequency, minimum noise figure, and RF power has been measured and analyzed. The reduction of transconductance is turned out to be one of the major causes of the RF performance degradation. The measurement also shows that the RF performance degradation is more significant than the DC performance degradation. Especially, the degradation of minimum noise figure is the most significant.

Gain-clamped thulium-doped fibre amplifier with single pump at 1050 nm

The large homogeneous bandwidth of a thulium-doped fibre amplifier makes it suitable for optical gain clamping. This has been demonstrated experimentally. Gain variation of 1.2 dB for 15 dB input dynamic range has been achieved, with less than 1 dB gain ripple over 20 nm, and no noise figure degradation, while pumped at 1050 nm.

Two-stage L-band EDFA applying C/L-band wavelength-division multiplexer with the counterpropagating partial gain-clamping

A simple ring laser technique of two-stage gain-clamped long-wavelength band erbium-doped fiber amplifier is investigated. The ring laser light is excluded at the output end and noise-figure degradation can be reduced due to the counterpropagating partial gain-clamping in the second stage. The laser mechanism is achieved by the C/L-band wavelength-division multiplexer instead of a tunable bandpass filter and an optical circulator at the output end, which were often used in the previous counterpropagating ring laser architectures, and thus, this design is cost-effective. The gain-clamping of long-wavelength band (1559-1606.2 nm) in our configuration is demonstrated experimentally for the saturating tone (1587.6 nm) power up to -2 dBm.

New pump wavelength of 1540-nm band for long-wavelength-band erbium-doped fiber amplifier (l-band edfa)

A long-wavelength-band erbium-doped fiber amplifier (L-band EDFA) using a pump wavelength source of 1540-nm band has been extensively investigated from a small single channel input signal to high-power wavelength division multiplexing (WDM) signals. The small-signal gain coefficient of 1545-nm pumping among the 1540-nm band is 2.25 times higher compared to the conventional 1480-nm pumping. This improvement in gain coefficient is not limited by the pumping direction. The cause for this high coefficient is explained by analyzing forward- and backward-amplified spontaneous emission spectra. The gain spectra as a function of a pump wavelength suggest that a broadband pump source as well as a single wavelength pump can be used as a 1540-nm-band pump. In the experiment for high-power WDM signals, the power conversion efficiency for 256 WDM channel input is 48.5% with 1545-nm pumping. This result shows more than 20% improvement compared with the previous highest value for the L-band EDFA. Finally, the 1545-nm bidirectionally pumped EDFA is applied as a second stage amplifier in an in-line amplifier of an optical communication link with a 1480-nm pumped first stage EDFA, in which the input power of the second-stage EDFA is +2.2 dBm. The power conversion efficiency yields a 38% improvement without noise figure degradation compared with the case of 1480-nm pumping.

Gain-clamping in two-stage L-band EDFA using an unwanted backward ase from second stage

A gain clamping technique for the long wavelength band erbium-doped fiber amplifier (L-band EDFA) is presented. It uses two circulators and a broad band fiber Bragg grating to route wasted backward C-band ASE from the second stage and launch it back into the input end of the first stage of a two-stage amplifier. The two-stage L-band EDFA has shown a small signal gain improvement of 5.7 dB compared to a single-stage amplifier with a slight noise figure degradation. By utilizing the wasted backward ASE, a L-band gain-clamped EDFA with high gain can be realized. Compared to the unclamped case, this gain-clamping technique is effective in reducing the total gain variation as small as 0.3 dB .

A fully integrated low-IF CMOS GPS radio with on-chip analog image rejection

A fully integrated Global Positioning System (GPS) radio is presented. Low-IF architecture was used for a high level of integration and low power consumption. An on-chip analog image-reject filter provides 18 dB of image-noise rejection to prevent noise figure (NF) degradation. With image rejection performed in the analog radio, a single-path (nonquadrature) output was used. The integrated synthesizer only requires an off-chip phase-locked loop-filter to function. Implemented in a 0.35-/spl mu/m 2P4M CMOS process, the integrated radio has a chip area of 9.5 mm/sup 2/. The radio operates over a wide range of voltage and temperature, from 2.2 to 3.6 V and from -40/spl deg/C to +85/spl deg/C and consumes 27 mW from a 2.2-V supply. The receiver has 4 dB NF.

Frequency-scalable SiGe bipolar RF front-end design

The optimum collector current density, at the global minimum noise figure (NF) point for a bipolar transistor, scales linearly with frequency. The optimum source impedance, on the other hand, remains constant if the device area is scaled inversely with frequency. As a result, transforming the design from one frequency to another can be achieved by simple circuit scaling. Taking advantage of the shallow nature of the NF/sub min/ global minima, it is possible to increase the linearity of the low-noise amplifier (LNA) or decrease its power consumption, which is required for multimode designs, with little degradation in NF. These theoretical results have been applied to LNA and active mixer designs, and verified by constructing a 1.8-GHz frequency-scaled SiGe bipolar test chip. The measured LNA NF is 1.3 dB at 4.5 mA, while the double-balanced mixer achieves a single-sideband (SSB) NF of 6.1 dB for the low-linearity mode and an IIP3 and an SSB NF of +3 dBm and 6.6 dB, respectively, for the high-linearity mode.

RF performance degradation in nMOS transistors due to hot carrier effects

This paper reports the hot electron induced RF performance degradation in multifinger gate nMOS transistors within the general framework of the degradation mechanism. The RF performance degradation of hot-carrier stressed nMOS transistors can be explained by the transconductance degradation, which resulted from the interface state generation. It has been found that the RF performance degradation, especially minimum noise figure degradation, is more significant than dc performance degradation. From the experimental correlation between RF and dc performance degradation, RF performance degradation can be predicted just by the measurement of dc performance degradation or the initial substrate current. From our experimental results, hot electron induced RF performance degradation should be taken into consideration in the design of the CMOS RF integrated circuits.

Gain-clamped fiber amplifier with a short length of preamplification fiber

Although gain-clamping an erbium-doped fiber amplifier (EDFA) by a counterpropagating ring resonator prevents oscillation light from being output, it degrades the amplifier's noise figure. The noise figure degradation can be reduced by using a length of EDF, that is short enough not to cause any gain saturation, for preamplification. Experiments confirm that the prestage EDFA reduces the noise figure degradation under constant gain operation.

0.15-μm RF CMOS technology compatible with logic CMOS for low-voltage operation

Radio Frequency (RF) CMOS is expected to replace bipolar and GaAs MESFETs in RF front-end ICs for mobile telecommunications devices in the near future. In order for the RF CMOS to be popularly used in this application, compatibility of its process for high-speed logic CMOS and low supply voltage operation are important for low fabrication cost and low power consumption. In this paper, a 0.15-/spl mu/m RF CMOS technology compatible with logic CMOS for low-voltage operation is described. Because the fabrication process is the same as the high-speed logic CMOS, manufacturability of this technology is excellent. Some of the passive elements can be integrated without changing the process and others can be integrated with the addition of a few optional processes. Mixed RF and logic CMOS devices in a one-chip LSI can be realized with relatively low cost. Excellent high-frequency characteristics of small geometry silicon MOSFETs with low-power supply voltage are demonstrated. Cutoff frequency of 42 GHz of n-MOSFETs, which is almost the same level at that of general high-performance silicon bipolar transistors, was obtained. N-MOSFET's maintained enough high cutoff frequency of 32 GHz even at extremely low supply voltage of 0.5 V. Moreover, it was confirmed that degradation of minimum noise figure for deep submicron MOSFETs with 0.5 V operation is sufficiently small compared with 2.0 V operation. These excellent high-frequency characteristics of small geometry silicon MOSFETs under low-voltage operation are suitable for mobile telecommunications applications.

1.58 µm band fluoride-basedEr 3+ -doped fibre amplifier for WDMtransmission systems

An Er3+-doped fluoride-based fibre amplifier (F-EDFA) with flat amplification characteristics in the range 1565–1600 nm was constructed for the first time. This provided a 5 nm wider flat amplification range than a silica-based Er3+-doped fibre amplifier (S-EDFA). A flattened signal gain of 30 dB was achieved with a gain excursion of 0.9 dB for a WDM signal in this wavelength range. The Er3+-doped fluoride fibre (F-EDF) which achieved a signal gain of over 30 dB without any noise figure degradation had a shorter optimum length than Er3+-doped silica fibre (S-EDF). Furthermore, F-EDF extended the amplification wavelength in the longer wavelength range by 2 nm compared with S-EDF.

Noise figure of saturated 1310-nm polarization insensitive multiple-quantum-well optical amplifiers

The noise figure degradation due to saturation by amplified spontaneous emission of high-gain 1310-nm polarization insensitive multiple-quantum-well optical amplifiers has been investigated systematically by studying amplifiers of different lengths. It is found that the intrinsic noise figure of 4 dB of a device with 20-dB single-pass gain is degraded to about 5 dB for a device having 36-dB single-pass gain. This degradation in noise figure is very modest, compared to results reported earlier for semiconductor optical amplifiers with bulk-gain media, illustrating the benefits of using a quantum-well gain medium in semiconductor optical amplifiers.

EDFA noise figure degradation caused by amplifiedsignal double Rayleigh scattering in erbium dopedfibres

For the first time, an EDFA noise figure increase caused by amplified signal double Rayleigh scattering in erbium doped fibres has been measured. The results can be explained by a model that takes into account incoherent and coherent mixing of the directly and doubly backscattered fraction of the signal light.

Beam scanning microstrip arrays using diodes

The feasibility of using diodes in linear microstrip antenna arrays to facilitate electronic beam scanning is investigated. The first concept concerns a microstrip line loaded with varactor diodes serving the dual purpose of phase shifter and feeder for a linear travelling wave array. Theoretical and practical results provide antenna design data on the number and type of diodes, optimisation of the radiating elements and temperature effects. Likely noise figure degradation, transient beam scanning response, and the antenna construction are other design aspects discussed. An array at 7.5 GHz containing 24 varactor diodes demonstrates that some 20° of beam scan is achievable before the travelling wave action is disrupted, and confirms the usefulness of the concept for applications demanding modest beam scan range and a simple low cost construction. The second concept introduced is a novel microstrip patch element with embedded diode and polariser enabling mixer action to take place. The theoretical and practical design of this antenna mixer element, and its deployment in an eight element linear beam scanning array at 2.92 GHz, is presented. Other mixer configurations, using additional diodes offering superior suppression of spectral products, are noted and the possible influence of the polariser on interelement mutual coupling investigated. Computations and measurements show that coupling effects are not significantly increased and confirm the usefulness of the antenna mixer element concept in beam forming array applications where no premixer low noise amplification is demanded.

Modeling the gain degradation of high concentration erbium-doped fiber amplifiers by introducing inhomogeneous cooperative up-conversion

The gain degradation of erbium-doped fiber amplifiers (EDFAs) with high erbium ion (Er/sup 3+/) concentration at 1.48- and 0.98- mu m pump wavelengths is modeled by introducing inhomogeneous cooperative up-conversion (IhCU). General formulas describing the gain degradation as a function of IhCU rate are obtained by solving rate equations for population probabilities in the relevant Er/sup 3+/ energy levels. The experimental results, such as low gain for high Er/sup 3+/ concentration, and higher saturated gain with counterpropagation than with copropagation pumping, which have not yet been explained theoretically, are qualitatively explained by this model. Good agreement between the measured and calculated gain is obtained. The gain degradation characteristics at 1.48- and 0.98- mu m pump wavelengths are analyzed with this model. The advantage of counterpropagation pumping is determined qualitatively. The noise figure degradation is also evaluated. >

Influence of reflected light on erbium-doped fiber amplifiers for optical AM video signal transmission systems

Investigates experimentally the influence of reflected light on an erbium-doped fiber amplifier for use in optical AM frequency-division multiplexing (FDM) video distribution systems when reflection points exist before and after the amplifier. It is found that amplifier distortion is not affected by reflected light but that the signal gain and the noise figure of the fiber amplifier degrade with increased reflectivity. Gain was decreased by 3 dB when reflectivity after the amplifier was -12 dB. It was theoretically and experimentally clarified that the noise figure degradation was related to the internal reflection of the erbium-doped fiber, in addition to the reflection before and after the fiber amplifier. This internal reflection is caused by input signal light scattered within the erbium-doped fiber.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optical amplifier noise figure in a coherent optical transmission system

Two important aspects of optical amplifier noise figure as measured with a heterodyne detection receiver are investigated. First, differential mode gain will result in polarization-dependent degradation of the perceived amplifier noise figure, even when the noise figures for the TE and TM modes of the amplifier are the same. For a differential mode gain of 7.5 dB the noise figure degradation can be as large as 3 dB, and experimental data is reported in good agreement with theoretical predictions. Secondly, the first experimental demonstration of the use of image-rejection techniques to improve the sensitivity of a heterodyne receiver limited by beat noise between the local oscillator and amplified spontaneous emission is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>