Showing papers on "Phase noise published in 1987"

An Analysis of the Output Spectrum of Direct Digital Frequency Synthesizers in the Presence of Phase-Accumulator Truncation

Abstract: An algorithm is presented for the calculation of the spectrum of direct digital frequency synthesizers (DDFS's) as a result of phase accumulator truncation. This algorithm, which is derived using number theoretic methods, includes a closed form expression relating the magnitude, number, and position of the spurious noise lines in the output spectrum of a DDFS to the read-only memory (ROM) look-up table size, the amount of phase accumulator truncation and the input frequency control command. The combined finite word length effects of the ROM and the Digital-to-Analog converter (DAC) nonlinearities are also examined in the light of these new results and new design guidelines are developed. The spectrums predicted by these closed form expresslons are compared against spectrums generated by a discrete Fourier transform (DFT) and are shown to have comparable accuracy. As a result of obtaining an expression for the magnitude of the spurious the input frequency command word and the ROM table size, the phase noise frequencies, a relationship between the greatest common divisor of accumulator word lengths, and the magnitude of the worst case spur is obtained. This relationship is used as the basis for a novel modification to the conventional phase accumulator structure which results in a 3.922dB reduction in the magnitude of the worst case spurious response. This hardware modification is also shown to average out the error effects of DAC nonlinearities and roundoff in the stored sine ROM samples.

Local oscillator induced instabilities in trapped ion frequency standards

Abstract: The trapped ion frequency source is one of a class of passive atomic frequency standards that necessarily use an ancillary frequency source to interrogate the atomic transition. For passive atomic sources such as Rubidium standards, ultimate long term performance of the source is not dependent on this local oscillator, except to the extent limited by feedback gain. For the trapped ion source this immunity to local oscillator phase noise is lost. In contrast to the Rubidium source, a sequential measurement procedure is used in which the signal from the local oscillator is sensed only some of the time. Since the local oscillator is only periodically sampled, certain short term fluctuations in the local oscillator frequency will give rise to long term fluctuations in the difference between the stabilized local oscillator frequency and that of the atomic absorption. We have performed calculations of the influence of such phase noise fluctuations in the reference oscillator on the performance of the standard as a function of duty cycle for a local oscillator with frequency fluctuations showing a 1/f spectral density, as is typically shown by crystal Quartz oscillators for long measuring times (1-100 seconds). Expressions are generated for the limiting trapped ion -1/2 variance due to the local Oscillator for various values for the duty factor d. Explicitly treated are the cases d<1, d=1-6, (6 < 1) and d = 1/2. It is seen that for a duty factor < 90%, local Oscillator performance equal to that of the ion standard (for a measuring timer equal to the period te of the sampling cycle) will significantly degrade the characteristic 1-1/2 passive atomic standard performance. For d near 1, (6 = (1-d) < 1) an approximately linear dependence of this degradation on 6 is found.

Characteristics and Sources of Phase Noise in Stable Oscillators

Abstract: The frequency stability of an oscillator is a very important characteristic for many applications. Yet the causes and sources of some basic types of noise are poorly understood, particularly for close-to-carrier noise. A review is presented in this paper of the present state of knowledge about the sources and characteristics of frequency fluctuations in stable oscillators using quartz acoustic resonators (BAW and SAW) or dielectric resonators as the high Q frequency stabilizing element. A brief discussion of the various parameters used to quantify random frequency fluctuations is presented along with the relative merits of open- and closed-loop phase noise measurements. Phase noise in stable oscillators usually arises from additive voltage fluctuations and direct parameter modulation processes. Additive

The Acceleration Sensitivity of Quartz Crystal Oscillators: A Review

Abstract: A tutorial on navigation, radar, and identification systems is presented. The topics discussed are the consequences of acceleration sensitivity in crystal oscillators on the Allan variance, including the effects of sinusoidal and random vibration, phase noise and integrated phase jitter; the vector nature of quartz resonator sensitivity; the theoretical description of the cause of the acceleration sensitivity of quartz resonators; techniques for the measurement of acceleration sensitivity; and the effect of frequency multiplication on acceleration effect. Various techniques currently being used or developed for reducing the effective acceleration sensitivity are considered. The techniques fall into three general categories: reduction of the acceleration sensitivity of the resonator; passive techniques that use compensating elements in the oscillator feedback loop, e.g. a second resonator or an acceleration sensitivity capacitor; and active acceleration compensation schemes that sense the acceleration and feedback a compensating signal to a tuning network. >

The performance of optical phase-locked loops in the presence of nonnegligible loop propagation delay

Abstract: The optical phase-locked loop is analyzed taking into account shot noise, phase noise, and loop propagation delay. The degradation of loop phase error due to propagation delay is evaluated in terms of the delay bandwidth product \omega_{n} \cdot \tau_{D} . This product was found to have a maximum value of 0.736 for absolute loop stability. The resulting effect on a Costas loop system optimized for zero time delay is discussed. It is found that in order to maintain a 10-9BER system performance with \xi = 1/2^{0.5}, R = 0.85 A/W, P_{DATA} = -59.2 dBm, and a 1-MHz beat linewidth, the delay time must be kept below 1.8 ns. If the beat linewidth increases to 15 MHz this figure drops to 0.12 ns.

ASK multiport optical homodyne receivers

Abstract: Several types of ASK multiport homodyne receivers are investigated, and the impact of the phase noise and of the shot noise on these receivers is analyzed. The simplest structure is the conventional multiport receiver with a matched filter in each branch. This structure can tolerate \DeltavT [ \deltav is the laser finewidth and T is the bit duration) of several percent with a small power penalty (3.6 percent for 1-dB penalty and 5.2 percent for 2-dB penalty). Optimization of branch filters of conventional multiport receivers does not help when the linewidth (and the penalty) is small but does improve the receiver performance for larger linewidths. The most important point of the paper is the novel wide-band filter-rectifier-narrow-band filter (WIRNA) structure, proposed and investigated here for the first time for optical communication systems. It is shown that the optimized WIRNA homodyne receivers are extremely robust with respect to the phase noise: the WIRNA tolerable value of \DeltavT is 3.6 percent for 1-dB penalty and more than 50 percent for 2-dB penalty. Thus, the WIRNA structure opens, for the first time, the possibility of constructing homodyne receivers operating at several hundred megabits per second with conventional DFB lasers without complicated external cavities. Under no-phase-noise conditions, all the multiport receivers investigated here have the same performance, which is identical to that of heterodyne ASK receivers. In addition, the optimized WIRNA receivers can tolerate tapproximately) the same laser linewidth as the heterodyne ASK receivers. Thus, the main difference between the WIRNA multiport homodyne and heterodyne receivers is that the former shifts the processing to a lower frequency range, in return for a more complicated implementation. This difference makes the WIRNA multiport homodyne receivers particularly attractive at high (say, several gigabit per second) bit rates.

Modulation and detection characteristics of optical continuous phase FSK transmission system

Abstract: The modulation and differential detection characteristics of optical CPFSK transmission systems are investigated both theoretically and experimentally. The error rate expressions of differentially detected CPFSK are derived by considering phase noise of LD's. It is clear that the linewidth requirement is less than 0.68 m percent of the bit rate, where m is modulation index. The performances of CPFSK are then experimentally presented at 400 Mbit/s using external optical feedback DFB LD's as the optical source. A beat spectral linewidth of less than 200 kHz for the transmitter and local oscillator LD's is achieved. The frequency response nonuniformity of frequency modulation efficiency is compensated by electrical circuits within 3 dB and 60°. To reduce IF thermal noise, a resonance-type preamplifier is used, with a 4.8 pA/ \sqrt{Hz} average input noise current density, and a receiver sensitivity 1.3 dB better than the conventional preamplifier. Differential detection of the 400-Mbit/s CPFSK modulation is performed. The generation of CPFSK is confirmed by good correlation between the output spectrum and theory. The average received optical power at a 10-9bit error rate is -49.9 dBm which improves direct detection by 10.3 dB. No additional power penalties due to 290-km transmission exist.

Phase and frequency detector circuits

Abstract: A Phase/Frequency Locked Loop comprises a controllable oscillator which is phase locked with the clock of an incoming non-return-to-zero digital data signal. The controllable oscillator may be a voltage-controlled oscillator (VCO) or may be purely digital. The circuitry includes a novel digital phase and frequency detector which detects both frequency and phase error by sampling the incoming data stream at multiple phases of the output of the VCO (or the digital equivalent thereof). One of two binary disagreement signals are produced depending on the sense of the phase error. During periods of frequency error, the circuit automatically selects the proper type of disagreement signal (the leading-edge disagreement) required to achieve frequency lock.

Theory for optical heterodyne DPSK receivers with post-detection filtering

Abstract: We present a general theoretical model for optical heterodyne DPSK receivers for optical communications systems where transmitter and local oscillator lasers have significant linewidths. Quantum phase noise in the lasers is treated as such, but in contrast with previous models for DPSK, receiver noise and local oscillator shot noise are treated as additive noise on the receiver output voltage, as this allows a straightforward description of the effects of post-detection filtering. As a consequence of the detection scheme, a key issue is to account for the non-Gaussian statistics of the output voltage, and this is done using a Chernov bound formulation. Detailed numerical results for a typical 140 Mbit/s p-i-n-FET front end are presented. It is found that heterodyne DPSK gives improved receiver sensitivity compared to other heterodyne detection schemes for IF linewidths below 0.7 percent of the data rate.

The Relationship Between Resonator and Oscillator Noise, and Resonator Noise Measurement Techniques

Abstract: Flicker, or l/f noise in just one component, the acoustic resonator, is the dominant source of frequency fluctuations in a well designed oscillator using a bulk acoustic wave or surface acoustic wave device. Measurement of resonator noise allows prediction of oscillator noise and performance improvements through selection of devices. Leesons model for oscillator noise is reviewed, then modified to incorporate the effect of resonator noise. Typical oscillator spectra are examined using the model. Two models for resonator noise are discussed, and data presented demonstrating that the cause of resonator instability is center frequency fluctuations, not phase fluctuations. The effect of loaded Q on oscillator and resonator noise is discussed. Three means to measure resonator noise are reviewed, these being, installing the resonator in an oscillator, a dual resonator bridge, and a single resonator bridge. Calibration of each method is discussed and a simple calibration method for the single resonator bridge, which lends itself to automated testing, is proposed. Noise floor limitations of the three methods are analyzed, and typical levels to be expected are given. A correlation technique to further improve the noise floor is suggested. An improved single resonator bridge which automatically sets and holds quadrature for fast, temperature stable measurements is presented. Use of a commercial phase noise measurement system to improve accuracy and ease calibration is discussed.

Extremely Low Phase Noise SAW Resonator Oscillator Design and Performance

Abstract: SAW resonator designs with overnioded cavities. very wide apertures. dual apertures, etc.. as well as modified fabrication techniques. have been used to realize an overall reduction in an oscillator's phase noise spectrum. i.e.. white +M. flicker FM. and random walk FM. The incident RF power handling capability of these SAW resonator designs is in excess of +20 dBm. a key requirement to achieving an extremely low oscillator phase noise floor. A new processing technique was also employed to reduce both the flicker FM and random walk FM phase noise levels. Using these various techniques a 5 to 15 dB improvement in the overall phase noise spectrum for several prototype oscillators was demonstrated. Specifically. a white OM noise floor of -182 dBclHz. and a flicker FM noise level of -1 10 dBc/Hz at fm = 100 Hz carrier offset were measured on several 500 MHz SAW resonator oscillators. A 42s MHz SAW resonator oscillator exhibited a fractional frequency stability. w (T). of 1~10-~' for T = lx104 seconds. This exceptionally go2d time domain stahility corresponds to a random walk FM noise process for which S,,(fm) = 6 Hz2lHz at fm = l~lO-~ Hz. This data

Phase Noise Reduction in FET Oscillators by Low-Frequency Loading and Feedback Circuitry Optimization

Abstract: Optimization of low-frequency Ioading allows reduction of 1/f converted noise in FET oscillators. Moreover, an appropriate low-frequency feedback between drain and gate gives an improvement over previous results. This improvement is explained by taking into account the properties of the noise autocorrelation function.

The Multiplex Disadvantage and Excess Low-Frequency Noise

Abstract: Analysis of the performance of a Fourier transform spectrometer with respect to source shot and flicker noises is presented. It was found that source shot noise uniformly distributes throughout the baseline, whereas source flicker noise remains localized about the generating spectral region(s).

Noise and the Solid State

Abstract: Thermal Noise 1/f Noise and Burst Noise Noise in Ferromagnetic and Ferroelectric Materials Hot Carriers and Ballistic Transport Avalanche Devices and the Gunn Effect Cryogenic Devices Oscillator Noise Noise in Radiation Detectors Fluctuations in Charge Appendices References Index

A thin-film bulk-acoustic-wave resonator-controlled oscillator on silicon

Abstract: A composite ZnO bulk-acoustic-wave thin-film resonator (TFR) has been fabricated on a silicon substrate with a double-diffused BJT. Fabrication techniques unique to the integration of the TFR are discussed. The integrated TFR-BJT structure was configured as a VHF Pierce oscillator circuit with a fundamental frequency of 257 MHz. Phase noise is better than -90 dBc/Hz at a 1-kHz offset. Temperature stability is - 8.5 ppm/°C from 5°C to 65°C and - 3.75 ppm/°C from 55°C to 5°C. The integration of the TFR with active components is viewed as a development toward large-scale RF circuit integration.

Generation of noise by electronic iteration of the logistic map

Abstract: A new circuit that generates low-frequency noise is presented. This circuit is based upon an electronic realization of the logistic map system. The noise power density spectrum of the output was measured and confirmed to be approximately white. We also note the operation of the circuit as a voltage-programmable 2-, 3-, or 4-valued oscillator.

Reducing phase fluctuations in a coherent radiation beam using feedforward control

Abstract: A method and apparatus for reducing fluctuations such as phase noise in a characteristic of a coherent beam of radiation. The apparatus includes an interferometer for sensing the fluctuation at the first position to generate an interference beam. The interference beam is incident on a radiation detector such as a photodiode which generates an electrical output signal responsive to the intensity of the incident beam. This signal is amplified by an amplifier and fed to a phase modulator. Another portion of the original laser beam is also fed to the phase modulator. The arrangement is such that the phase modulations applied to the beam by the phase modulator under the control of the signal from the detector reduce or cancel the phase noise in the original beam.

Carrier recovery of modulated signals

Abstract: A method and apparatus are described for phase and frequency locking a reference oscillator to an incoming modulated signal. The method and apparatus enable the carrier recovery of the incoming modulated signal. Phase and frequency locking devices are connected in feedback loops (20, 30) with a coherent detector (10) that determine the amount of phase and frequency error between the reference oscillator of the coherent detector and the incoming modulated signal. The feedback loops correct such frequency and phase error so as to enable the reference oscillator to be in phase and frequency step with the modulated signal.

Jitter vs. additive noise in magnetic recording: Effects on detection

Abstract: Noise on thin-film magnetic recording media is often modeled as a transition jitter, whereas particulate media noise is taken to be additive. Although these two noise mechanisms can produce similar spectra their effects on detection can be markedly different. This paper analyzes these differences for several signaling/detection schemes and concludes that where transition jitter dominates, peak detection of

System design and long-span transmission experiments on an optical FSK heterodyne single filter detection system

Abstract: The influence of LD phase noise on a heterodyne noncoherent detection system was evaluated. Based on the evaluation, an optical FSK heterodyne single filter detection system with large frequency deviation and wide-band IF filter has been developed to allow use of stand-alone DFB LD's. In the system, a phase tunable DFB LD was used as an FSK transmitter light source to improve the FSK modulation characteristics. An IF filter with appropriate bandwidth evaded the influence of LD phase noise. With these configurations, long-span (243 km at 140 Mbit/s and 204 km at 280 Mhit/s) transmission experiments have been successfully carried out on this single filter detection system. To the contrary, influence of LD phase noise appeared in a limited IF bandwidth case, which agrees well with the theoretical evaluation.

Adaptive noise cancellation in a closed loop control system

Abstract: An adaptive noise cancellation system reduces undesired noise in a closed loop control system by injecting an adaptively constructed noise cancellation signal at an appropriate point in the closed control loop. The generation of a compensation filter N for adaptive noise cancellation loop error signal is disclosed by two methods. A first method is an inverse error rejection response (IERR) method. A second method optimally matches spectrums of a noise signal and a noise reference signal at the adaptive noise cancellation system. This second method is referred to as a spectral matching (SM) method.

Trellis-Coded MPSK with Reference Phase Errors

Abstract: With trellis-coded MPSK schemes, reference phase errors have a major impact on the system performance. This paper analyzes the interrelation among the coded-modulation format, the reference phase tracker, and the carrier phase noise. A tight upper bound to the error probability of a maximum likelihood decoder is introduced. This bound reveals eight new distance-type functions which, along with the wellknown minimum Euclidean distance, characterize the coded-modulation scheme. Relationships between the new distance-type functions and the various system parameters as well as the irreducible probability of error are pointed out. Numerical results for uncoded QPSK and three Ungerboeck encoded 8-PSK schemes showy that excessive smoothing of the reference phase in presence of carder phase noise can degrade the performance of coded 8-PSK modulation considerably.

A release from masking by continuous, random, notched noise.

Abstract: Thresholds for 10‐ms sinusoids simultaneously masked by bursts of bandpass noise centered on the signal frequency were measured for a wide range of signal frequencies and noise levels Thresholds were defined as the signal power relative to the masker power at the output of an auditory filter centered on the signal frequency It was found that the presentation of a continuous random noise, with a spectral notch centered on the signal frequency, produced a reduction in signal thresholds of up to 11 dB A notched noise spectrum level of 0–5 dB above that of the masker proved most effective in producing a masking release, as measured by a reduction in masked threshold A release from masking of up to 7 dB could be obtained with a continuous bandpass noise The most effective spectrum level of this noise was 5 dB below that of the masker The effect of the continuous notched noise was to reduce signal‐to‐masker ratios at threshold to about 0 dB, regardless of the threshold in the absence of continuous noise

Phase-induced intensity noise in an incoherent Fabry-Perot interferometer and other recirculating devices

Abstract: Laser phase-induced intensity noise limits the dynamic range of all kinds of recirculating structures under short coherence illumination. The shape of the power spectrum of this noise, while it is always periodic, depends on the device type. Recirculating delay lines and the reflecting Fabry–Perot interferometer (F–P) exhibit minimum noise at integer multiples of 1/(round-trip time), whereas the transmitting F–P shows maximum noise at exactly these frequencies. This phenomenon is theoretically analyzed, and expressions are given for the standard deviation, the autocovariance, and the power spectrum of that noise for a general recirculating structure. The important problem of laser phase-induced intensity noise for the F–P structure is studied in detail, theoretically and experimentally, in both reflecting and transmitting modes.

Development of a 1.5-tonne niobium gravitational radiational antenna

Abstract: A 1.5‐tonne Nb gravitational radiation antenna is described. Problems associated with a noncontacting magnetically levitated parametric upconverter transducer are discussed, and a system using a bonded microwave reentrant cavity and bonded mechanical impedance transformer is described and analyzed in detail. It is shown that such an antenna can be expected to achieve a noise temperature of ∼1 mK. An ultralow phase noise tunable microwave source for the transducer pump signal is described, as well as precision bonding techniques which yield a mechanical positioning accuracy of 10−6 m, and a reproducibility of 10−8 m.

Reduction of Close-to-Carrier Phase Noise in Surface Acoustic Wave Resonators

Abstract: A technique is presented which consistently reduces the close-to-carrier phase noise inherent to SAW resonators. By the application of a high power RF drive signal at the SAWR resonant frequency, phase noise reductions ranging from 0 to 26 dB have been achieved in over 40 resonators of various designs. Using this process. the resulting average SAW resonator close-to-carrier phase noise levels are now comparable to those of the other electronic components used in the construction of SAW resonator stabilized oscillators. The noise reduction technique, its ramifications, and the results of some experiments which were performed in order to characterize this process, are presented. INTRODUCTION Surface acoustic wave resonator (SAWR) oscillators are now accepted as reliable, low-noise signal sources for use in modern radar and communication systems. Recent research indicates that the SAWR is usually the dominant source of close-tocarrier phase noise in both the flicker frequency [1,2] and random walk [31 sections of the noise spectrum, for oscillators utilizing high performance, commercially available silicon bipolar transistor based electronics. This paper presents a technique which has consistently reduced the close-bcarrier phase noise levels in SAW resonators. It involves driving the SAWR with a higher than normal incident RF power level for a short time period. This procedure has produced flicker noise reductions ranging from 0 to 26 dB in over forty SAW resonators of various frequencies, acoustic apertures, and metallization types, with an average noise reduction of 8 dB. Additionally, three 425 MHz SAW resonators exhibited 3 to 15 dB reductions in random walk FM noise, with an average decrease of 10 dB. All noise reductions occur without any significant changes in resonator parameters such as frequency, insertion loss, and quality factor. The measured SAWR open-loop flicker noise levels after this "burn-in'' procedure are now comparable to, or less than the typical close-to-carrier phase noise levels observed in state-of-the-art, commercial silicon bipolar transistor amplifiers. PROCEDURE The typical SAWRs discussed here are 350 to 810 MHz two-port resonators, fabricated on quartz with either aluminum or coppcr-doped aluminum transducers, and acoustic apertures ranging from 130 to 400 wavelengths. Standard in these device designs are 1 to 1.5 pm thick busbar metallizations and long effective cavity lengths (approximately 300-350 wavelengths) [4]. An important parameter to minimize is the phase noise noise inherent to the SAWR device. Due to varations during the fabrication process, there will always be a distribution of SAWR phase noise among like devices. The phase noise of these devices can be evaluated using a Hewlett-Packard 11740A Phase Noise Measurement System in an open-loop, or two-port measurement mode [l]. The distribution of resonator noise levels can be narrowed and the average level reduced significantly by the application of a "burn-in" process to each device. This involves applying a high power RF signal, usually in the range of +24 to +33 dBm, to the device for time periods ranging from 0090-560718710000-0043 $ I .OO 0 I987 IEEE several minutes to hours. The output side of the SAWR is terminated in 50 ohms during the "bum-in" period. The signal frequency is set to the resonant frequency of the device under the incident power conditions. This frequency was determined by connecting a power meter to the output side of the device and adjusting the frequency of the high power signal source for maximum transmission at the burn-in power level. These power levels will produce peak compressional stress levels of 1 to 4x108 N/m2 resulting in non-linear elastic effects within the device [5] and the power dissipated in the device can substantially raise the SAWR substrate temperature. Both of these power induced effects result in a shift of the resonant frequency, and a short time period will occur before this frequency will reach equilibrium. As will be discussed later, maximum noise reduction will only occur when the device is driven as close as possible (well within the 1 dB bandwidth) to its resonant frequency, so that the signal source should be carefully adjusted during the early stages of the run. The choice of maximum incident power is determined by the size of the acoustic aperture and the effective cavity length of the S A W . The level of stress developed within the device is inversely proportional to these parameters [61, and irreversible damage may occur (e.g., increased loss, permanent frequency shifts. and the increase of transverse modes) if the stress levels are set too high. Observations indicate that the minimum power level that can induce noise reduction is that which establishes a peak compressional stress level of about 1x108 N/m2. Stress levels below this value do not generally induce noise reduction in SAWRs whose initial open-loop phase noise levels at 1 Hz offset are in the range of -120 to -130 dBc/Hz, which are typical S A W phase noise levels. We do note that unusually noisy devices have shown improvement at slightly lower strcss levels (-5x10' N/m2). Overall Change in Flicker Noise

A novel modulation technique for 1/f noise reduction in dc SQUIDs

Abstract: We describe a novel modulation scheme for dc SQUIDs in flux locked loop applications that cancels the effects of Josephson junction critical current fluctuations. The scheme involves switching the SQUID between three states and detecting the output at the second harmonic of the modulation frequency. With this scheme we have achieved a ten fold reduction of the low frequency flux noise spectral density over that obtained with a conventional flux locked loop readout. A dc SQUID with a 20 pH inductance had a resultant noise spectral density of 10-12 \Phi\min{0}\max{2} /Hz at 0.1 Hz, three times lower than the lowest flux noise previously reported for any SQUID system at this frequency.

Squeezed-state enhanced two-frequency interferometry

Abstract: Here an experiment is proposed to demonstrate squeezed-state enhanced interferometry. An interferometer employing differenced detection, in which the photodetectors have less than a unit quantum efficiency, is analyzed. In order to avoid low-frequency noise, a readout signal at frequency 2νs is generated at the detector by injecting coherent light having two frequency components ν0 + νs and ν0 − νs into one input port of the interferometer. In order to realize a significant sensitivity enhancement, squeezed light fed into the other input port must be squeezed at frequencies ν0 ± νs and ν0 + 3νs.