Flicker noise in GaAs MESFET X-band amplifiers in the temperature range 300 K to 2 K

We report measurements of the noise temperature of small-signal, low-noise X-band GaAs MESFET amplifiers from room temperature down to 2 K, at offset frequencies of several hundred hertz from the carrier and for input carrier powers from -40 to -20dBm. We observe a dramatic increase in the level of flicker noise as these devices are cooled to liquid helium temperatures, in marked contrast to the normally observed decrease in noise temperature of an unsaturated GaAs MESFET amplifier as it is cooled.     

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.     

Nonlinear analysis of a cross-coupled quadrature harmonic oscillator

The dynamic equations governing the cross-coupled quadrature harmonic oscillator are derived assuming quasi-sinusoidal operation. This allows for an investigation of the previously reported tradeoff between close-to-carrier phase noise and quadrature precision. The results explain how nonlinearity in the coupling transconductances, in conjunction with a finite amplitude relaxation time and de-tuning of the individual oscillators, cause close-to-carrier AM-to-PM noise conversion. A discussion is presented of how the theoretic results translate into design rules for quadrature oscillator ICs. SPECTRE RF simulations verify the developed theory.     

A New Look at Noise in Transferred Electron Oscillators

Low-frequency current and voltage fluctuations have been measured, and it has been confirmed that noise in packaged transferred electron devices (TED's) is due to three distinct noise mechanisms: flicker, generation-recombination, antd thermal noise. For transferred electron oscillators (TEO's), this low-frequency noise is upconverted into the microwave frequency range and adds to the intrinsic RF noise. We have found that between 1 kHz and 1 MHz off the carrier, temperature-dependent generation-recombination noise is the main contributor to the total noise. A model of a noisy TEO is presented. This model permits the calculation of AM and FM noise spectra from device and circuit parameters for measured low-frequency noise or the derivation of device characteristics from noise and circuit parameter measurements.     

RF Spectrum of Thermal Noise and Frequency Stability of a Microwave Cavity-Oscillator

The spectral distribution of the themal noise within a microwave cavity equipped with an extemal feedback loop has been calculated and measured. An equivalent electrical model is established from which the noise spectral density can be calculated at any post in the system, The effect of the gain and phase of the loop on the spectral distribution is measured with a spectrum analyzer through a heterodyne technique and comparison with theoretical calculations shows good agreement. Also, the modified cavity Q and resonant frequency is measured for various loop parameters. An experimental setup allowing precise measurement of frequency stability and FM noise close to carrier of microwave oscillators is presented and discussed. preliminary measurements of the short-term frequency stability of the system when operated as a microwave cavity-oscillator show a predominant flicker frequency noise. The measured FM noise close to carrier is related to time-domain measurements of frequency stabitity and to RF spectrum of the cavity-oscillator.     

GaAs FET's with a flicker-noise corner below 1 MHz

GaAs MESFET's with significantly reduced low-frequency noise are demonstrated through application of an understanding that the dominant noise source is generation-recombination (g-r) noise from deep level traps in the gate and backside depletion layers. A 1/f noise spectrum measured from 100 Hz to 10 MHz is modeled as the sum of Lorentzian noise spectra from a few traps subject to the temperature distribution inherent in a GaAs MESFET. The noise associated with a single mid-bandgap trapping level does not appear as an ideal Lorentzian, but rather as 1/f over nearly a decade frequency range by virtue of a time constant that is a strong function of temperature ( exp[Ea/ kT]) and an estimated temperature distribution of 22°C across the active region. The major g-r trap was characterized as having an activation energy of 0.75 eV. By reducing the g-r noise, flicker noise was decreased by more than 15 dB compared to our conventional GaAs MESFET's and the noise corner was reduced to less than 1 MHz from a typical 40 MHz. This significant reduction was achieved by using MBE layers designed to have lower trap concentrations and high channel doping. These results are within 10 dB of the estimated 1/f noise limit due to the quantum mechanics of carrier scattering [5], [14].     

Multiloop optoelectronic oscillator

We describe and demonstrate a multiloop technique for single-mode selection in an optoelectronic oscillator (OEO). We present experimental results of a dual loop OEO, free running at 10 GHz, that has the lowest phase noise (-140 dBc/Hz at 10 kHz from carrier) of all free-running room-temperature oscillators to date. Finally, we demonstrate the first fiber-optic implementation of the carrier suppression technique to further reduce the close-to-carrier phase noise of the oscillator by at least 20 dB     

AM and FM Noise of BARITT Oscillators

AM, FM, and baseband noise of a BARITT diode oscillator in the range 100 Hz-50 kHz off the carrier has been measured under various operating conditions. A simple calculation has been made, relating the baseband noise to the oscillator AM and FM noise via measured amplitude and frequency modulation sensitivities and the results have been compared with the noise measured. It is shown that, depending on the bias current applied, both AM and FM noise performance can be degraded by up-conversion. Complete removal of up-converted noise requires a high-impedance low-noise bias supply since both the diode noise and bias supply noise at baseband frequencies may be significant when up-converted. Even with all modulation suppressed, the AM and FM noise has a flicker component almost completely correlated with the diode flicker noise at baseband frequencies. The RF power dependence of the AM and FM noise has also been investigated. It is shown that the BARITT oscillator noise compares very favorably with that of IMPATT's and TEO's. Values of -142 dB/100 Hz (AM noise) and 3.5 Hz/(100 Hz)/sup 1/2/ for Q/sub ext/ = 200 (FM noise) have been measured at 30 kHz off the carrier.     

A 1.2-V RF front-end with on-chip VCO for PCS 1900 direct conversion receiver in 0.13-/spl mu/m CMOS

In this paper, a 1.2-V RF front-end realized for the personal communications services (PCS) direct conversion receiver is presented. The RF front-end comprises a low-noise amplifier (LNA), quadrature mixers, and active RC low-pass filters with gain control. Quadrature local oscillator (LO) signals are generated on chip by a double-frequency voltage-controlled oscillator (VCO) and frequency divider. A current-mode interface between the downconversion mixer output and analog baseband input together with a dynamic matching technique simultaneously improves the mixer linearity, allows the reduction of flicker noise due to the mixer switches, and minimizes the noise contribution of the analog baseband. The dynamic matching technique is employed to suppress the flicker noise of the common-mode feedback (CMFB) circuit utilized at the mixer output, which otherwise would dominate the low-frequency noise of the mixer. Various low-voltage circuit techniques are employed to enhance both the mixer second- and third-order linearity, and to lower the flicker noise. The RF front-end is fabricated in a 0.13-/spl mu/m CMOS process utilizing only standard process options. The RF front-end achieves a voltage gain of 50 dB, noise figure of 3.9 dB when integrated from 100 Hz to 135 kHz, IIP3 of -9 dBm, and at least IIP2 of +30dBm without calibration. The 4-GHz VCO meets the PCS 1900 phase noise specifications and has a phase noise of -132dBc/Hz at 3-MHz offset.     

Analytical modeling of flicker and thermal noise in n-channel DG FinFETs

A compact physics-based thermal and flicker noise model has been developed for n-channel Double Gate FinFETs with varying structural parameters. The effects of mobility degradation due to velocity saturation, carrier heating and channel length modulation have been incorporated for an accurate modeling of noise. The mobility fluctuations dependent on the inversion carrier density have been considered and a characteristic of the flicker noise different from that of Bulk MOSFETs was observed. This has been validated by the experimental results. Based on the proposed thermal and flicker noise model, a compact expression of the corner frequency has been derived and the effects of the structural parameters such as the length and the thickness of the channel have been analyzed. Finally, the model has been applied for p-channel devices and noise behavior in accordance with experimental data has been obtained.     

Compact Channel Noise Models for Deep-Submicron MOSFETs

In this paper, compact channel noise models valid in all regions of operation for deep-submicron MOSFETs have been developed and experimentally verified. The physics-based expressions for thermal noise and flicker noise and corner frequency constitute compact channel noise models. The carrier heating, channel-length modulation, and mobility degradation due to the lateral electric field have been incorporated in the models. The effect of the mobility and carrier number fluctuations on the flicker noise, as well as the dependence of the mobility limited by Coulomb scattering on the inversion carrier density, have been considered in the flicker noise model. The measurement results validate the proposed models.      

A micropower CMOS, direct-conversion, VLF receiver chip formagnetic-field wireless applications

A micropower CMOS, direct-conversion very low frequency (VLF) receiver is described for receiving low-level magnetic fields from resonant sensors. The single-chip, phase locked loop (PLL)-synthesized receiver covers a frequency range of 10-82 kHz and provides both analog and 9-b digital baseband I and Q outputs. Digital I and Q outputs are accumulated in a companion digital chip which provides baseband signal processing. Emphasis is plated on the receiver micropower RF preamplifier which uses a lateral bipolar input device because of the significant increase in flicker noise illustrated for PMOS devices in weak inversion. Lateral bipolar transistors are also utilized in the mixer and IF stages for low flicker noise and low dc offsets. Special attention is given to isolating the internal local oscillator signals from the low-level RF input (0.3 μV noise floor in 300 Hz BW), and local oscillator feedthrough is indiscernible in the RF preamplifier output noise spectrum. The 100% duty-cycle receiver, intended for miniature, battery-operated wireless applications, operates approximately four months at 80 μA from a 6-V, 220-mA-hr battery     

Oxide thickness dependent compact model of channel noise for E-mode AlGaN/GaN MOS-HEMT

In this paper, a compact channel noise model for gate recessed enhancement mode GaN based MOS-HEMT which is valid for all regions of operation is proposed. The compact noise model consists of high frequency thermal noise and low frequency flicker noise. The drain current, which is one of the most important parameters for compact noise model is developed by incorporating interface and oxide traps, mobility degradation due to vertical electric field, velocity saturation effect and self-heating effect. The flicker noise model is derived by considering mobility and carrier fluctuation due to traps present in both oxide and interface layer. The thermal noise and flicker noise models are validated by comparing the results with TCAD simulation and experimental results from literature respectively. Effect of thermal and flicker noise power spectral density (PSD) variation with different oxide thickness has also been analyzed.     

A New RF CMOS Gilbert Mixer With Improved Noise Figure and Linearity

The noise figure of an RF CMOS mixer is strongly affected by flicker noise. The noise figure can be improved using pMOS switch circuits, which insert current at the on/off crossing instants of the local oscillator switch stage because the circuits reduce the flicker noise injection. When it is applied to a conventional Gilbert mixer, the injection efficiency and linearity are degraded by the nonlinear parasitic capacitances of the pMOS switch circuits and the leakage through the parasitic path. We propose the pMOS switch circuits with an inductor, which tunes out the parasitic components at 2f_o and closes out the leakage path. The mixer fabricated in 0.13-mum CMOS at 2.4-GHz center frequency has provided improved characteristics for linearity and noise figure.     

Effects of Si3N4, SiO, and polyimide surface passivations on GaAs MESFET amplifier RF stability

The effects of silicon nitride, silicon monoxide, and polyimide MESFET passivations on amplifier RF stability have been examined. GaAs MESFET amplifiers subjected to biased life tests show a time dependent "drift" in RF performance from turn on to hundreds of hours. These short- and long-term instabilities in performance have been correlated with surface effects. It was found that passivation with a surface dielectric such as Si3N4can eliminate this drift mechanism, while other dielectrics either delayed the onset of drift or had no desirable effects. Methods for deposition of these dielectrics and the relative merits of these methods are discussed.     

Determination of Equivalent Circuit Parameters Describing Noise from a Gunn Oscillator

The AM and FM fluctuations in an oscillator output are originated from impedance fluctuation in low frequencies (baseband noise) and voltage or current fluctuation in the vicinity of the carrier frequency (RF noise). In this paper, from newly defined "complex correlation coefficient between AM and FM noises," contributions of baseband and RF noises to the AM and FM noises are determined. Examples of data for X-band Gunn oscillators show that both the AM and FM noises are mainly caused by the baseband noise in the vicinity of the carrier frequency (within 1-kHz band), whereas they are mainly due to the RF noise at frequencies further than 10 kHz from the carrier frequency.     

Dual carrier suppression interferometer for measurement of phasenoise

A new scheme for phase noise measurement is presented, based on dual stage suppression of the carrier and synchronous detection of the noise sidebands of the device being tested. This scheme features real time output and intrinsically low instrument flicker. A prototype shows a residual flicker as low as -160 dBrad²/Hz at 1 Hz off the 100 MHz carrier. Other implementations are possible, from 1 MHz to several gigahertz. Applications include the noise characterisation of components and the design of innovative ultrastable oscillators     

Noise in distributed MESFET preamplifiers

The theory of noise in a distributed MESFET preamplifier is developed. From this, it is shown that the equivalent input noise current density of a distributed preamplifier of an optical receiver can be improved by using large gate line matching impedance and appropriate scaling of the MESFET width. A front-end tuning circuit was designed using filter theory to further improve the noise performance of the preamplifier. A monolithic GaAs MESFET distributed preamplifier was fabricated with on chip front-end tuning components. Using a 35 μm InGaAs p-i-n photodiode, the preamplifier was shown to have an equivalent input noise current density of 8 pA/√Hz and an 8 GHz bandwidth. To date, this is the best known result for a 0.8 μm GaAs MESFET process     

Equal-gain loci and stability of a microwave GaAs MESFET gate mixer

The performance of a microwave GaAs MESFET gate mixer is theoretically investigated to clarify the existence of a conditionally stable RF frequency range as well as an unconditionally stable frequency range in which maximum available conversion gain (MACG) can be defined. For the unconditionally stable range, the MACG and load and source impedances are calculated as functions of RF frequency. For the conditionally stable range, the stability circle and equal gain loci are shown for source RF and load IF impedances. The conditionally stable region of the GaAs MESFET mixer appears around F_T of the MESFET. Higher conversion gain is easily obtained by choosing a MESFET for which the F_T is close to the RF frequency     

Random telegraph noise of deep-submicrometer MOSFETs

The random telegraph noise exhibited by deep-submicrometer MOSFETs with very small channel area (⩽1 μm²) at room temperature is studied. Analysis of the amplitude of the current fluctuations reveals that the trapped charges generate noise through modulation of the carrier mobility in addition to the carrier number. Parameters needed for modeling the carrier mobility fluctuation effect on the flicker noise in conventional MOSFETs are extracted directly from the random telegraph noise data