High Noise Figure Research Articles

Investigation of the high frequency noise figure reduction of SiGe heterojunction bipolar transistors using actualised physical models

High frequency noise figure reduction is one of the major requirements for analog circuits. The introduction of strained SiGe alloys as the base layer material in heterojunction bipolar transistors opens new possibilities to improve the (base resistance) −1 × current gain product. Hence, the use of SiGe as the base layer material instead of silicon can result in a major improvement of the high frequency noise. In this paper, the minimum noise figure reduction as a function of the germanium fraction is addressed, using actualized physical models for the bandgap and the mobility. Two limiting cases will be discussed: a heterojunction bipolar transistor with very low base resistance and still acceptable minimum noise figure and current gain, and a high gain heterojunction transistor with superior noise figure for acceptable base resistance values.

Amplification Characteristics of Polarization-Maintaining Erbium-Doped Optical Fiber.

A polarization-maintaining erbium-doped fiber (PM-EDF) based on the PANDA (Polarization-maintaining AND Absorption-reducing) type fiber technology has been developed as an amplification medium of a polarization-maintaining optical amplifier for 1550 nm band. Detail amplification and polarization characteristics of the PM-EDF have been evaluated for the first time. The carefully designed PM-EDF amplifies the optical signal with a high gain and low noise figure, keeping the state of polarization through the fiber. The amplification performance of the newly developed PM-EDF is the same as that of the conventional erbium doped amplifiers except the polarization characteristics. The achieved characteristics are 35 dB gain for small signal, 4.8 dB noise figure, 70% slope efficiency, 30 dB of polarization extinction ratio even in a fiber coil of 15 mm in diameter. Polarization hole burning is also reported.

Optimization of Tandem 980-nm Single-Pump Recycled Erbium Amplifier Configurations

In this paper we study the design and performance of 980-nm single-pumped tandem recycled erbium amplifier pump (REAP) configurations. These configurations feature high gain (>40 dB) and low noise figure (3 dB) using an isolator incorporated in the amplifier length to block backward-traveling amplified spontaneous emission from degrading the amplifier performance. In particular, we investigate theoretically the trade-offs between gain and noise figure and their dependency on fiber length, signal level, and pump power. First, using the ratio between first-stage length and total amplifier length as a figure of merit, we determine the optimum position of the isolator to achieve a combination of high gain and low noise figure, for constant levels of pump power in the small signal regime. Then, we calculate the amplifier performance for applications as power booster, in-line amplifier, and preamplifier. Since the REAP topology is especially attractive as a preamplifier, we further establish the dependency of gain and noise figure as a function of second-stage active fiber length and pump power level. Finally, we contrast the performance of two different REAP configurations and show good agreement between our experimental data and simulations.

REAP: recycled erbium amplifier pump

We report a novel erbium doped fiber preamplifier design with a combination of high gain (>40 dB) and low noise figure (3 dB) at 1556 nm for 80 mW of 980 nm pump power. The co-directional single pumped amplifier employs a composite two stage arrangement in which the second stage is pumped with recycled pump not used in the first stage. In addition, we contrast the amplifier performance trade-offs with the insertions of an isolator or a band pass filter or both in between the two amplifier sections. Finally, we demonstrate a receiver sensitivity of /spl minus/37 dBm (156 photons/bit) with a 10 Gb/s optical preamplifier regenerator. >

Erbium-doped fiber amplifier with 54 dB gain and 3.1 dB noise figures

It is shown that for practical pump powers (<100 mW) a combination of high gain (>33 dB) and low noise figure (3 dB) cannot simultaneously be achieved with a conventional codirectionally pumped EDFA. However, using a codirectionally pumped composite EDFA incorporating an isolator overcomes the problem, and an amplifier with 51 dB (54 dB) gain and 3.1 dB noise figure (NF) for only 45 mW (93 mW) of pump power is demonstrated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

GaAs Varactor Tuners for UHF TV

Recently, varactor tuners have become very popular in TV tuner, but the noise figure and selectivity of present day's varactor tuners are inferior to that of mechanical tuners. Series resistance, Rs, of Si tuning diodes manufactured is around 0.8?in mean value at 470 MHz and at diode capacitance of 9 pF. The value of 0.8?is so high that low resistance diodes, Rs < 0.8?, for instance, have been selected specifically for UHF tuners. Recently, low resistance diodes with Rs = 0.68?have been fabricated by ion implantation technique. 1) Even if these diodes are employed, the Q value of tuning circuit is still much lower than that of mechanical tuner in UHF region. Such high resistance diodes lead to a higher noise figure and lower gain in tuner performance.

Self-passivated GaAs/W mixer diode

GaAs/tungsten Schottky barrier mixer diodes have been fabricated in a self-passivated, grown guard layer configuration. These devices have exhibited 0.64 eV barrier voltages together with the ability to withstand nanosecond RF pulses in excess of 8 ergs with no resulting deterioration in noise figure performance. Such high burnout resistance properties are attributed to the absence of any significant metallurgical interaction between the GaAs and tungsten at temperatures as high as 600°C. The somewhat high noise figures exhibited by these devices are attributed to interface states, possibly arising from strain.

Performance of Dual-Gate GaAs MESFET's as Gain-Controlled Low-Noise Amplifiers and High-Speed Modulators

This paper describes the microwave performance of GaAs FET's with two 1-mu m Schottky-barrier gates (dual-gate MESFET). At 10 GHz the MESFET, with an inductive second-gate termination, exhibits an 18-dB gain with --26-dB reverse isolation. Variation of the second-gate potential yields a 44-dB gain-modulation range. The minimum noise figure is 4.0 dB with 12-dB associated gain at 10 GHz. Pulse modulation of an RF carrier with a 65-ps fall ad a 100-ps rise time is demonstrated. The dual-gate MESFET with high gain and low noise figure is especially suited for receiver amplifiers with automatic gain control (AGC) as an option. The MESFET is equally attractive for subnanosecond pulsed-amplitude modulation (PAM), phase-shift-keyed (PSK), and frequency-shift-keyed (FSK) carrier modulation.

Principles and methods of low-frequency electric and magnetic measurements using an rf-biased point-contact superconducting device

A comprehensive study has been made of some low-frequency electric and magnetic measurements which can be made using an rf-biased point-contact superconducting device of the symmetric two-hole type introduced by Zimmerman. Section 1 begins with a qualitative description of the phenomena which are observed and utilized in making the measurements. In Section 2 a semiquantitative and semiempirical analysis is made of the weakly superconducting system as it interacts with the rf field. Reasonable agreement between the analysis and experiment is obtained, thereby establishing a basis for optimization of conditions for measurement. Empirical data are also given as needed on coupling-coil characteristics. In Section 3 noise in the measuring system is discussed and the characteristics of the flux-locked loop used in the measurements introduced. It is shown that the total observed noise may be divided into at least three parts: one intrinsic to the sensor, one which reflects voltage noise in the amplifier, and one coupled into the instrument by the measuring circuit. The noise power spectra of the first two are shown to be comparable in an actual system. Below 100 Hz the spectrum, relative to the square of the flux quantum, is white and estimated by 10−8 Hz−1. In Section 4 the characteristics are discussed of a dc voltmeter using a flux-locked loop and having a relatively high input impedance and good noise figure. An experimental study of noise is presented. A particular case with subpicovolt sensitivity limited by Johnson noise is discussed. In Section 5 low-frequency ac measurements of resistance, self-inductance, and mutual inductance are discussed using a novel bridge circuit and the superconducting sensor in a flux-locked loop as null detector. The noise characteristics are described and studied experimentally. Extreme sensitivity is achieved, both in resistance and inductance. A 1 µω resistor may be measured with a precision of 1 part in 105 with subpicowatt power dissipation. Measurements of the mutual inductance due to a 1.6-mg crystal of CMN are described in which the crystal temperature was reduced to the millidegree region. In Section 6 measurements of static magnetization are discussed and the ideas applied to measurement of temperature using milligram quantities of CMN. Measurements using a pair of thermometers, one inside and the other outside the mixing chamber of a dilution refrigerator, are presented. In Section 7 the concept of a device-noise temperature is introduced and shown to be in the microdegree region. A very simple Johnson noise thermometer is then described. Measurements with this thermometer in the mixing chamber of a dilution refrigerator were carried out to 12 mK, the effective device temperature being measured to be +0.8±1.3mK. A qualitative experimental estimate places the actual device temperature well below 1 mdeg. In appendices a technical discussion of the flux-locked loop and of noise is given.

Noise of transistors in the Darlington circuit†

Measurements on Darlington and single common-emitter circuits show that the former displays a much higher noise figure in both the flat part of the frequency spectrum, and at low frequencies where I/f noise predominates. Theoretical analysis predicts the noise increase in the flat part of the frequency spectrum.

Factors Influencing Amplification using Parallel Pumped Magnetostatic Modes†

ABSTRACT The excitation of magnetostatic mode pairs by a pump magnetic field applied parallel to the static magnetic field, and the application of this phenomenon as a ferrimagnetic amplifier, are discussed. A description is given of an experimental study of magnetostatic mode pumping using a swept magnetic field display. An investigation of the behaviour of low frequency oscillations which accompany magnetostatic mode excitation is followed by a study of their effect on mode pumping. Results are given which differ from those previously reported. A method of obtaining further information on the origin of the high noise figure of ferrimagnetic amplifiers is proposed.

A new uhf/vhf silicon transistor for the consumer market

Within the past year, transistors have been used in increasing numbers in the oscillator stages of uhf television tuners. This application not only represents the introduction of the first transistors in television receivers; it also indicates that transistors capable of good uhf and vhf performance can be mass-produced at consumer prices. Both germanium and silicon devices which are suitable for use in the oscillator function are now commercially available. The question arises as to the relative merits of amplifier versions of these devices for uhf and vhf amplifier service. Until recently, silicon transistors had not been considered for use in rf amplifier stages in consumer applications because of high noise figures or high cost, the former not being particularly significant in oscillator service. (Although silicon n-p-n uhf low-noise amplifiers have been available for some time, their use in consumer products has been restricted by their high cost.) This paper describes a new n-p-n silicon uhf-vhf transistor, RCA Dev. No. TA2503, having electrical characteristics tailored for consumer amplifier applications at frequencies up to 900 megacycles. Gain and noise through the useful frequency range are discussed, and relative performance is given for various vhf and uhf applications.

High frequency noise figure — A function of fα or fT?

There has been some question in the past as to whether f α or f T should be used as the frequency criterion in determining transistor high frequency noise figure. This report is based on the following equation for noise figure as derived by Nielsen:1 $F = 1 + {r_{b}^{\prime} \over r_{g}} + {r_{e} \over 2r_{g}} + {{({r}_g+{r}_{b}^{\prime} + {r}_e)^2} \over {2r_{e}\, r_g \, \beta_o}} \left [1 + {(f/f_a)^2 \over 1-\alpha_o}\right]. \eqno{\hbox{(1)}}$ Results show rather conclusively that f α should be used and not f T , for the frequency range from approximately 40 to 300 mc. These results apply specifically to the diffused base 2N1742 transistor. Conclusions have been drawn by comparing (1) the degree to which theoretical f α -noise figure correlates with measured noise figure to (2) the degree to which theoretical f T -noise figure correlates with measured noise figure

Low-noise klystron amplifiers

The principles of low-noise guns have been applied to klystron amplifiers with good corroboration of the theory. In the past, many people thought that klystrons had inherently high noise figures, while others advanced the theory that low-noise guns might be used with klystrons as well as with wave tubes. The development to be described here shows that the former impression is not true and verifies that low-noise klystron amplifiers are possible. The most obvious difference between the guns for low-noise klystron amplifiers and those typical of low-noise traveling-wave tubes is the higher beam current which is required for adequate klystron gain. A byproduct of this higher current is a wide dynamic range. In addition to the development of the electrical parameters, a major effort went into klystron construction techniques somewhat peculiar to low-noise klystron amplifiers. The data taken show that alignment of the low-noise gun electrodes with the drift tube, alignment of the beam with the magnetic field, elimination of the collector's secondary electrons from the beam, and cleanliness of the tube are of primary importance in constructing a low-noise klystron amplifier. Several two-cavity, low-noise klystron amplifiers were built for operation in both S-band and C-band. The typical low-level gain was 11.5 db, and the saturated power output was 180 mw. Several tubes exhibited noise figures below 9 db; the lowest value obtained was 6.7. db.

Application of a Backward-Wave Amplifier to Microwave Autodyne Reception

A microwave receiver using a single-circuit backward-wave amplifier as a combination radio-frequency ampliier and homodyne local oscillator is described. The amplitler tube is operated at a value of beam current just above that required to maintain oscillation. It is shown that in this way, the high gain and narrow bandwidth of the single-circuit backward-wave amplifier may be utilized in an electronically tunable microwave receiver. The resultant sensitivity is 10 to 15 db worse than that obtainable from a good superheterodyne. The loss in sensitivity is due entirely to the high noise figure of the backward-wave amplifier, which can theoretically be reduced to a value comparable with that of a supereterodyne. The advantages of the receiver are its simplicity and its lack of image diffculties. Rejection of off-frequency signals is such that they are attenuated by at least 50 db.

Noise wave excitation at the cathode of a microwave beam amplifier

General equations are derived, giving the amplitudes of noise current and velocity for the many modes of space-charge wave propagation in an electron beam. The properties of the cathode taken into consideration are the current density and the emission velocity distribution as a function of position. Simplified cases are considered which show the order of magnitude of effects due to cathode nonuniformity and magnetic field strength. From present evidence, it can be shown that high noise figure in low noise tubes is almost certainly due to excess noise velocity, brought about by cathode nonuniformities. Suggestions are given for reducing these undesirable effects.

Spontaneous emission and the noise figure of maser amplifiers

The Nyquist-Johnson formulation of the noise in circuits arising from thermal agitation is applied to circuit elements equivalent to and representing simple resonant absorption, such as occurs in paramagnetic materials or others having r-f line spectra. Such a model for a circuit resistance directly demonstrates the origin of the noise as spontaneous emission by excited particles, in complete analogy to black body radiation in free space. Extension of the conventional theorem to the domain of negative resistances at negative temperatures, as encountered in Maser amplifiers, is valid under circumstances of practical significance. Amplifiers of small noise figure can be made for frequencies ν such that hν kT 0 , where T 0 is the effective temperature of the signal source, is not large compared to unity. For example, an amplifier of high gain and noise figure less than 2 can be built if use is made of a medium describable by a negative effective temperature smaller, in absolute value, than T 0.