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Showing papers on "Phase noise published in 1993"


Journal ArticleDOI
TL;DR: In this article, a delta-sigma (Delta-Sigma) modulation and fractional-N frequency division technique for indirect digital frequency synthesis using a phase-locked loop (PLL) is described.
Abstract: A description is given of a delta-sigma ( Delta - Sigma ) modulation and fractional-N frequency division technique for performing indirect digital frequency synthesis using a phase-locked loop (PLL). The use of Delta - Sigma modulation concepts results in beneficial shaping of the phase noise (jitter) introduced by fractional-N division. The technique has the potential to provide low phase noise, fast settling time, and reduced impact of spurious frequencies when compared with existing fractional-N PLL techniques. >

604 citations


Proceedings ArticleDOI
20 Apr 1993
TL;DR: In this article, the effects of range correlation and local oscillator phase noise on the intermediate frequency spectrum in a coherent, continuous wave or pulsed Doppler radar are investigated.
Abstract: The problem of characterizing the effects of range correlation and local oscillator phase noise on the intermediate frequency spectrum in a coherent, continuous wave or pulsed Doppler radar is addressed. Since the phase noise is a stochastic process, the problem is defined in a stochastic processes context and a reasonable set of assumptions is imposed to produce a general, straightforward and easily understandable solution. The solution clearly indicates how the natural spectrum of the scatterer, the phase noise spectrum, and range correlation combine to produce the intermediate frequency spectrum. A specific example is provided for the case of a pulsed Doppler radar. The results are compared to the formulation based on the assumption that the phase noise is deterministic. >

117 citations


Journal ArticleDOI
TL;DR: In this article, the dependence of the range for accurate measurements on particular parameters of the optical system is discussed in the general case and for three specific laser sources, and the limitations imposed on measurements of discrete reflections and of Rayleigh backscattering due to phase noise originating in the finite coherence length of an optical source.
Abstract: An analysis of coherent optical FMCW is presented. It shows the limitations imposed on measurements of discrete reflections and of Rayleigh backscattering due to phase noise originating in the finite coherence length of the optical source. The dependence of the range for accurate measurements on particular parameters of the optical system is discussed in the general case and for three specific laser sources. >

116 citations


Journal ArticleDOI
Dejan Mijuskovic1, M. Bayer1, T. Chomicz1, N. Garg1, F. James1, Philip W. Mcentarfer1, J. Porter1 
09 May 1993
TL;DR: In this paper, a family of standard cells for phase-locked loop (PLL) applications is presented, which are processed using a 1.5 /spl mu/m, n-well, double-polysilicon, double layer metal CMOS process.
Abstract: A family of standard cells for phase-locked loop (PLL) applications is presented. The applications are processed using a 1.5 /spl mu/m, n-well, double-polysilicon, double-layer metal CMOS process. Applications include frequency synthesis for computer clock generation, disk drives, and pixel clock generators for computer monitors, with maximum frequencies up to 80 MHz. The synthesizers require no external components since the loop filter and oscillator are on chip with the phase frequency detector and the charge pump. Special voltage and current reference cells are discussed. Analysis of noise sources in the PLL demonstrates the need for reducing the phase noise of the system. A low phase noise is achieved through supply rejection techniques and by placing the oscillator in a high-gain feedback loop to minimize its noise contributions. Laboratory measurements of completed silicon show synthesizers with exceptionally linear gain, as well as transient responses and phase noise similar to predicted results. >

110 citations


Proceedings ArticleDOI
13 Oct 1993
TL;DR: The voice activity detector designed for vehicular noise is an improvement upon the VAD adopted for the discontinuous transmission (DTX) mode of the GSM standard, and performs significantly better at low SNR levels.
Abstract: Algorithms for voice activity detection in the presence of vehicular noise and babble noise are presented. The voice activity detector (VAD) designed for vehicular noise is an improvement upon the VAD adopted for the discontinuous transmission (DTX) mode of the GSM standard, and performs significantly better at low SNR levels. Work on a VAD that is suited for the babble noise environment is also briefly mentioned, and a scheme for combining the two VADs is proposed.

108 citations


Proceedings ArticleDOI
05 Dec 1993
TL;DR: In this paper, a monolithic high-Q oscillator, fabricated via a combined CMOS plus surface micromachining technology, is described, for which the oscillation frequency is controlled by a polysilicon micromechanical resonator to achieve stability and phase noise performance comparable to those of quartz crystal oscillators.
Abstract: A completely monolithic high-Q oscillator, fabricated via a combined CMOS plus surface micromachining technology, is described, for which the oscillation frequency is controlled by a polysilicon micromechanical resonator to achieve stability and phase noise performance comparable to those of quartz crystal oscillators. It is shown that the closed-loop, steady-state oscillation amplitude of this oscillator can be controlled through the DC-bias voltage applied to the capacitively driven and sensed /spl mu/resonator. Measurements indicate a phase noise density level of -168 dBm/Hz at 5 kHz offset frequency for an oscillator carrier power of -14.5 dBm. >

94 citations


Proceedings ArticleDOI
04 Apr 1993
TL;DR: In this article, the effects of range correlation and local oscillator amplitude and phase noise on the intermediate frequency (IF) spectrum of a coherent, continuous wave or pulsed Doppler radar are investigated.
Abstract: The authors address the problem of characterizing the effects of range correlation and local oscillator amplitude and phase noise on the intermediate-frequency (IF) spectrum of a coherent, continuous wave or pulsed Doppler radar. Since the amplitude and phase noises are stochastic processes, the problem is defined in a stochastic processes context, and a reasonable set of assumptions is imposed to produce a general, straightforward, and easily understood solution. The solution clearly indicates how the natural spectrum of the scatterer, the amplitude and phase noise spectra, and range correlation combine to produce the IF spectrum. A specific example is provided for the case of a pulsed Doppler radar. The results presented indicate that range correlation can have a significant impact on the IF spectrum and thus should be considered in radar analysis and design activities. >

66 citations


Proceedings ArticleDOI
W.K. Lam1, K.W. Wan1, J. Austin1, Enric Vilar, D.F. Bacon 
02 Jun 1993
TL;DR: In this paper, the phase noise stability measurement using complex demodulation and the approach to an unlocked spread spectrum communications probe is discussed, where the phase jitter and the frequency drift are small enough during the channel measurement period to obtain an accurate channel transmittance estimate.
Abstract: The authors review the technique of phase noise stability measurement using complex demodulation and the approach to an unlocked spread spectrum communications probe. This system has recently been developed to characterize a transhorizon communications channel at 11.6 GHz under both tropospheric scatter and anomalous propagation conditions. The receiver has a bandwidth of 31.25 MHz but has no carrier recovery and therefore no absolute phase reference. However, provided that the phase jitter and the frequency drift are small enough during the channel measurement period, it is possible to obtain an accurate channel transmittance estimate. The system has the capability of implementing time-domain signal averaging "on the fly", thus permitting high-speed channel identification under low SNR regimes. As the averaging period is increased (to improve the SNR), low phase jitter in the oscillators becomes imperative. The SNR improvement achieved is thus controlled by the maximum averaging period, which is a direct reflection of the stability of the oscillators. >

65 citations


Journal ArticleDOI
TL;DR: In this article, a 59.1 GHz train of 2.2 ps solitons with low phase noise was generated by a novel, passive, all optical fiber source, based on transformation of a dual frequency beat signal generated by 16 kHz line width erbium fiber DBR laser having a selectable and highly stable frequency separation, into a soliton train in a comblike dispersion profiled fiber, a novel fibre design which uses conventional optical fibres.
Abstract: A 59.1 GHz train of 2.2 ps solitons with low phase noise (<5×10−5) is generated by a novel, passive, all optical fibre source. The technique is based on transformation of a dual frequency beat signal generated by a 16 kHz line width erbium fibre DBR laser having a selectable and highly stable frequency separation, into a soliton train in a comblike dispersion profiled fibre, a novel fibre design which uses conventional optical fibres.

60 citations


Proceedings Article
08 Sep 1993
TL;DR: In this article, the results of an extensive study into the production of acoustic noise and vibration in the switched reluctance motor drive have been presented, and the results can be used to derive control laws for the power electronic controller to reduce the acoustic noises and vibration produced by the motor.
Abstract: This paper describes the results of an extensive study into the production of acoustic noise and vibration in the switched reluctance motor drive. Time domain analysis has been used to draw conclusions about the effects of changing the operating parameters of the power electronic controller on the vibration and acoustic noise. Experimental results have been taken from a four phase switched reluctance motor drive with one, two or four phase excitation. The results of this time domain study reveal important information which would not be apparent from frequency spectra. The results can be used to derive control laws for the power electronic controller to reduce the acoustic noise and vibration produced by the motor.

57 citations


Patent
Ilkka Niva1, Mika Tuutijarvi1
11 Feb 1993
TL;DR: In this paper, the power of the spectral components that are located close to a carrier frequency is modulated to reduce the DC component of a base band signal and correspondingly reduce the charging of AC coupling capacitors in the base band circuitry.
Abstract: A method, and apparatus for accomplishing the method, that causes the power of a narrow bandwidth signal to be spread to a wider bandwidth. The method operates by modulating the power of the spectral components that are located close to a carrier frequency. This reduces the DC component of a base band signal and correspondingly reduces the charging of a AC coupling capacitors in the base band circuitry. As a result, receiver recovery time is increased, and a more accurate signal strength estimate is made by a mobile telephone. In one embodiment of the invention a local oscillator signal (LO1) for an IF stage is first offset from a nominal frequency for an RF channel to be measured, and is then subsequently made equal to the nominal frequency. The variation in LO1 introduces phase noise which results in the modulation of the base band signal.

Journal ArticleDOI
TL;DR: In this article, the noise properties of pseudomorphic HEMTs were investigated in the low and intermediate frequency range (10 Hz to 150 MHz) and in the microwave range (4 to 18 GHz).
Abstract: Noise properties of AlGaAs/InGaAs/GaAs pseudomorphic HEMTs (PHEMTs) have been investigated simultaneously in the low and intermediate frequency range (10 Hz to 150 MHz) and in the microwave range (4 to 18 GHz) and compared to the noise of more classical devices such as MESFETs and GaAlAs/GaAs HEMTs. Unlike the other commercially available devices, PHEMTs exhibit the unique capability of providing simultaneously state-of-the-art microwave noise performance and a reasonable low-frequency excess noise. >

Journal ArticleDOI
TL;DR: In this paper, the frequency tuning and stabilization of a type-II phase-matched KTP doubly resonant optical parametric oscillator was performed using temperature and electro-optic tuning of the KTP crystal.
Abstract: We present experimental results of frequency tuning and stabilization of a type-II phase-matched potassium titanyl phosphate (KTP) doubly resonant optical parametric oscillator. Four tuning elements were employed to control the stability and tuning of the parametric oscillator. Discrete frequency tuning of a nearly degenerate optical parametric oscillator over a range of ~3 THz was obtained by crystal angle tuning and cavity-length scanning. We achieved continuous frequency tuning over a 0.5-GHz range through the use of temperature and electro-optic tuning of the KTP crystal. Using these frequency-control techniques, we phase locked the signal–idler beat frequency to an external microwave frequency source, thus demonstrating tunable optical frequency division. The power spectral density of the residual phase noise of the phase-locked signal–idler beat note was measured to be 0.3mrad/Hz. Characteristics of two different cavity designs, their operations, tuning behavior, and stability issues are examined.

Journal ArticleDOI
TL;DR: The dual-pulse-excited fiber ring is used to generate squeezed vacuum that, when injected into a measuring Mach–Zehnder interferometer, improves its sensitivity by 3 dB beyond the shot-noise limit.
Abstract: A novel scheme employing two pulses separated by a short time delay is used to cancel the phase noise from guided-acoustic-wave Brillouin scattering in a fiber ring interferometer. The dual-pulse-excited fiber ring is used to generate squeezed vacuum that, when injected into a measuring Mach–Zehnder interferometer, improves its sensitivity by 3 dB beyond the shot-noise limit.

Patent
24 Nov 1993
TL;DR: In this article, a noise reducer for reducing the results in the system output signal of optical noise introduced into an optical subsystem therein, having a phase modulator, by obtaining a noise representation signal used to offset the noise components in the signal obtained from the output of the optical subsystem.
Abstract: A noise reducer for reducing the results in the system output signal of optical noise introduced into an optical subsystem therein, having a phase modulator, by a source through obtaining a noise representation signal used to offset the noise components in the signal obtained from the output of the optical subsystem. This noise representation signal is not delayed in the obtaining thereof by any more than half the delays of the waves emitted from the source in reaching the optical subsystem output. The noise reducer may incorporate a device for adjusting the amplitude of the noise representation signal. It may also include another device for adjusting the phase of the noise representation signal, which may be used to affect the amplitude of the noise representation signal. These adjustments can result in an optimization of the noise representation signal so as to better effectively cancel the optical noise signal at the output of the fiber optic gyro having the noise reducer. The phase adjustment may be accomplished by affecting the phase of the bias modulation signal that goes to demodulate the fiber optic gyroscope system output signal or to demodulate both the fiber optic gyroscope system output signal and the noise representation signal, before the two latter signals are combined. A generator may be used for constructing a periodic signal, such as a triangular wave, having an appropriate amplitude and phase, to be a noise representation signal that is used to offset or cancel the noise components in the output signal from the fiber optic gyroscope system.

Journal ArticleDOI
01 Apr 1993
TL;DR: In this paper, a multivariance method consisting of obtaining the noise-type contributions with different variances and different integration time values is proposed. But the method is not suitable for the measurement of the level of each power law noise.
Abstract: Since the noise altering the output signal of oscillators may be modeled as power laws in the spectral density of frequency deviation, oscillator noise analysis is the measurement of the level of each power law noise. The principle of this new multivariance method consists of obtaining the noise-type contributions with different variances and different integration time values. All the data obtained from the different variances with the different integration times are then operated simultaneously. Thus, the most probable measurement, in the sense of least squares, is obtained for each type of noise. This method lends itself to an estimation of the uncertainty of the noise-type contribution measurement, taking into account the dispersion of the variance results. >

Journal ArticleDOI
TL;DR: Experimental spectra obtained by measuring the laser intensity noise after a broad-bandwidth diode-laser beam passes through a rubidium vapor cell are reported on and numerically calculated spectra based on a phase-diffusion model of the laser field are compared.
Abstract: We report on spectra obtained by measuring the laser intensity noise after a broad-bandwidth diode-laser beam passes through a rubidium vapor cell. The atomic resonance converts laser frequency fluctuations into intensity fluctuations. We compare our experimental spectra with numerically calculated spectra based on a phase-diffusion model of the laser field and find good agreement.

PatentDOI
TL;DR: In this article, an aircraft engine active noise cancellation system is described, in which the resonant frequency of the noise radiating structure is tuned to permit noise cancellation over a wide range of frequencies.
Abstract: A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of noise radiating structure is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating structure is tuned by a plurality of drivers arranged to contact the noise radiating structure. Excitation of the drivers causes expansion or contraction of the drivers, thereby varying the edge loading applied to the noise radiating structure. The drivers are actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the drivers, causing them to expand or contract. The noise radiating structure may be either the outer shroud of the engine or a ring mounted flush with an inner wall of the shroud or disposed in the interior of the shroud.

PatentDOI
TL;DR: In this paper, an aircraft engine active noise cancellation system is described, in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies.
Abstract: A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by a plurality of force transmitting mechanisms which contact the noise radiating element. Each one of the force transmitting mechanisms includes an expandable element and a spring in contact with the noise radiating element so that excitation of the element varies the spring force applied to the noise radiating element. The elements are actuated by a controller which receives input of a signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the elements and causes the spring force applied to the noise radiating element to be varied. The force transmitting mechanisms can be arranged to either produce bending or linear stiffness variations in the noise radiating element.

Patent
14 Oct 1993
TL;DR: In this article, a low phase noise third-order phase lock loop (PLL) is proposed to track and eliminate microphonic disturbances and phase hits in the frequency domain.
Abstract: A low phase noise third order phase lock loop which can track and eliminate microphonic disturbances and phase hits. The PLL utilizes a third order loop filter which incorporates two integrators. These two integrators, when coupled with the integration which occurs at the voltage control input of the voltage controlled oscillator within the PLL yield an open loop transfer function with a --18 dB/octave rolloff over a band of frequencies which at least encompasses the spectral content of the microphonic or phase hit phase noise disturbance to be eliminated. The open loop gain of the phase lock loop must be set high enough such that the phase lock loop does not oscillate and such that the loop converges and locks. The integrators are implemented with operational amplifiers with RC feedback networks. The values of the components in the RC feedback networks set the frequencies of two zeroes in the transfer function. The frequencies of these zeroes are set by proper selection of the R and C values to cause a change in slope of the open loop gain frequency response curve at the frequency of the zeroes from the -18 dB/octave rollof to a -6 dB/octave rolloff at the frequency of the zeroes. This causes the phase angle of the open loop PLL transfer function to be more positive than -180 degrees at the frequency at which the open loop gain magnitude frequency response curve falls to unity gain thereby achieving conditional stability. The open loop gain of the PLL is set such that the -18 dB/octave rolloff of the frequency response does not result in a gain of unity until a frequency is reached which is above the highest expected frequency deviation of the carrier caused by microphonic disturbances or phase hits. In the preferred embodiment, the gain is set high enough that the -18 dB/octave rolloff of the open loop gain frequency response extends over at least two decades and extends up to 10 kHz which encompasses substantially all the spectral content of the microphonic disturbance caused by package resonance which sources the phase noise to be eliminated.

Journal ArticleDOI
TL;DR: In this paper, a Schmitt trigger-driven stochastic resonator system with 1/f noise with white noise (thermal excitation) at the input of the resonators was investigated.
Abstract: Stochastic resonator systems with input and/or output 1/f noise have been studied. Disordered magnets/dielectrics serve as examples for the case of output 1/f noise with white noise (thermal excitation) at the input of the resonators. Due to the fluctuation-dissipation theorem, the output noise is related to the out-of-phase component of the periodic peak of the output spectrum. Spin glasses and ferromagnets serve as interesting examples of coupled stochastic resonators. A proper coupling can lead to an extremely large signal-to-noise ratio. As a model system, a l/f-noise-driven Schmitt trigger has been investigated experimentally to study stochastic resonance with input 1/f noise. Under proper conditions, we have found several new nonlinearity effects, such as peaks at even harmonics, holes at even harmonics, and 1/f noise also in the output spectrum.

Journal ArticleDOI
01 Apr 1993
TL;DR: In this paper, the main noise sources that affect the clock signal detection in an optically pumped cesium beam resonator are determined and their influence on the clock S/N ratio is evaluated.
Abstract: The main noise sources that affect the clock signal detection in an optically pumped cesium beam resonator are determined and their influence on the clock S/N ratio is evaluated. The following noise sources are taken into account: atomic shot noise, fluorescence photon noise, laser frequency noise, and clock signal detection noise. A theoretical model that predicts the variations of the S/N ratio as a function of different parameters characterizing the atom-laser interaction is developed. The main conclusion concerns the saturation of S/N value for high atomic flux due to laser frequency fluctuations. All the theoretical predictions were experimentally verified. >

Journal ArticleDOI
TL;DR: Two schemes for interferometric optical phase measurement, with sensitivity limited only by quantum noise in the light, are analyzed and subkilohertz signals are extracted from classical noise 67 dB greater with sensitivity approaching the quantum noise limit.
Abstract: Two schemes for interferometric optical phase measurement, with sensitivity limited only by quantum noise in the light, are analyzed. Direct detection is applicable to signals at modulation frequencies away from the technical noise of the light, so that quantum noise dominates the measurement. Alternatively signals otherwise obscured by classical optical noise may be recovered with a phase-modulation technique that shifts the signals to a quantum-noise-limited region of the photocurrent spectrum. The analysis is tested experimentally by using a polarimetric electric-field sensor. In the direct-detection scheme quantum-noise-limited performance produced a phase sensitivity of 0.25 μrad. The indirect scheme allowed subkilohertz signals to be extracted from classical noise 67 dB greater with sensitivity approaching the quantum noise limit.

Journal ArticleDOI
01 Apr 1993
TL;DR: In this article, a portable secondary standard for phase modulation (PM) and amplitude modulation (AM) noise at 5, 10, and 100 MHz is described, and the accuracy of the standard for both PM and AM noise is +0.14 dB.
Abstract: A practical implementation of a portable secondary standard for phase modulation (PM) and amplitude modulation (AM) noise at 5, 10, and 100 MHz is described. The accuracy of the standard for both PM and AM noise is +0.14 dB, and the temperature coefficient is less than 0.02 dB/K. The noise floor S/sub phi / (10 kHz) of the standard for PM noise measurements is less than -190 dBC relative to 1 rad/sup 2//Hz at 5, 10, and 100 MHz. The noise floor for AM measurements depends on the configuration. A calibrated level of PM and AM noise of approximately -130+or-0.2 dB relative to 1 rad/sup 2//Hz (for Fourier frequencies from approximately 1 Hz to 10% of the carrier frequency) is used to evaluate the accuracy versus Fourier frequency. Similar PM/AM noise standards are under test at 10 GHz. This new standard can also be used as an alternative to the normal method of calibrating the conversion sensitivity of the PM/AM detector for PM/AM measurements. Some types of time-domain measurement equipment can also be calibrated. >

Proceedings ArticleDOI
02 Jun 1993
TL;DR: In this article, a cryogenic sapphire phase stabilizer (SPS) was developed to meet microwave oscillator phase noise requirements at an untuned frequency of 7.9449 GHz with a loaded Q of 6 million.
Abstract: A cryogenic sapphire phase stabilizer (SPS) has been developed to meet microwave oscillator phase noise requirements. The SPS uses a high-Q, X-band sapphire dielectric whispering-gallery mode resonator as a discriminator to stabilize a quartz crystal oscillator. At an untuned frequency of 7.9449 GHz with a loaded Q of 6 million, an "open loop" discriminator noise floor (referred to 100 MHz) of approximately S/sub phi/(f) = -110 dB/f/sup 3/(/Hz) was previously reported for offset frequencies from 1 Hz to 1 kHz. Precise tuning of the sapphire resonant frequency now allows implementation of simplified control loops together with suppressed-carrier phase sensing circuitry. These improvements make possible an ultralow-noise demonstration of closed-loop SPS performance. From 1 Hz to 1 kHz a comparison of the SPS with a quartz crystal reference oscillator of the highest quality showed only the noise of the reference oscillator. These results appear to represent the lowest phase noise in a closed-loop or active sapphire oscillator to date at temperatures achievable with liquid nitrogen (77 K or higher). >

Journal ArticleDOI
TL;DR: In this paper, an approach using perturbation theory to simulate the noise behavior of free-running microwave oscillators based on a piecewise harmonic balance technique is outlined and applied to a planar integrated microwave oscillator at 14 GHz.
Abstract: An approach using perturbation theory to simulate the noise behavior of free-running microwave oscillators based on a piecewise harmonic balance technique is outlined and applied to a planar integrated microwave oscillator at 14 GHz. A single-sideband phase noise of -90 dBc/Hz at an offset frequency of 100 kHz was measured. Simulated and measured single-sideband phase noise values agree within the accuracy of measurements. >

Patent
Klaus Linhard1
23 Dec 1993
TL;DR: In this paper, the phases of at least two noise-affected signals are estimated in the frequency domain and the phase estimate and phase compensation required for the noise reduction are performed in the amplitude domain.
Abstract: The present invention relates to a method of reducing noise in a speech detection system. The phases of at least two noise-affected signals are estimated. The phase estimate and the phase compensation required for the noise reduction are performed in the frequency domain. The background noise and the transient behavior of the enclosed space are simultaneously estimated.

Patent
Nguyen Nhat M1
28 Jun 1993
TL;DR: In this paper, the authors proposed to use a series inductive element and an optional parallel capacitive element in line with the radio frequency input to reduce the thermal noise in a conventional Gilbert-cell active mixer.
Abstract: In a conventional Gilbert-cell active mixer, two local oscillator matched pairs of transistors receive a local oscillator input signal and are coupled to a radio frequency matched pair of transistors which receive a radio frequency input signal. The circuit generates an intermodulated output signal at the collectors of the local oscillator matched pairs. Noise degradation is reduced over the conventional mixer by replacing the standard radio frequency emitter degeneration resistor with a reactive element, thereby reducing thermal noise. Narrow-band input matching is achieved by insertion of a series inductive element and optional parallel capacitive element in line with the radio frequency input. Thermal noise contributed to the circuit is thereby minimized while circuit linearity is preserved in the narrow frequency band of interest.

Patent
07 Sep 1993
TL;DR: In this paper, a frequency and phase-locked synthesizer is used to recover a reference signal virtually free of phase noise, and generate a quadrature-phase reference signal for complex demodulation of the angular rate signal.
Abstract: For use with a quartz angular rate sensor, a frequency and phase-locked synthesizer recovers a reference signal virtually free of phase noise, and generates a quadrature-phase reference signal for complex demodulation of the angular rate signal. The synthesizer also ensures a precisely adjusted phase shift of approximately zero across the drive tines of the sensor. Moreover, the digital synthesizer provides a precise numerical indication of the drive frequency, which can be used for compensation and automatic tuning of filters, such as a tracking filter, a filter in an automatic gain control, and notch filters in the phase and/or frequency detectors in the digital synthesizer. The tracking filter is used as a pre-filter for the synthesizer, and is responsive to a passband-width control signal generated from the magnitude of the frequency and phase error signal controlling the frequency generated by the synthesizer. Preferably the synthesizer has an oscillator controller for producing a pair of frequency control signals that are the sine and cosine of a frequency control parameter (φ), and one of these control signals is generated from the other by a polynomial approximation. To compensate for roundoff error, when one of the in-phase or quadrature-phase outputs has a magnitude less than a limit value, a compensated value for the other output is computed from an even polynomial of the magnitude.

Journal ArticleDOI
TL;DR: In this paper, a technique for high frequency (up to 100 GHz), narrowband ( approximately GHz) optical modulation by encoding the millimeter-wave signal onto a beat note produced by photomixing of radiation from two 1.3 mu m DFB lasers is described.
Abstract: A technique is described for high frequency (up to 100 GHz), narrowband ( approximately GHz) optical modulation by encoding the millimeter-wave signal onto a beat note produced by photomixing of radiation from two 1.3 mu m DFB lasers. The phase noise on the beat note is compensated by a feedforward technique, using a low-frequency external optical modulator which simultaneously encodes the information to be transmitted. The modulation band can be tuned by varying the lasing frequency of one or both of the lasers. The fundamental performance limit of this technique is investigated, and the transmission of a pulsed RF signal at 40 GHz is demonstrated. >