Annual Symposium on Frequency Control 

About: Annual Symposium on Frequency Control is an academic conference. The conference publishes majorly in the area(s): Resonator & Crystal oscillator. Over the lifetime, 1850 publications have been published by the conference receiving 16516 citations.

Accurate Time and Frequency Transfer During Common-View of a GPS Satellite

Abstract: Summary First, Clock A and a GPS receiver are used to Even though the GPS is primarily a navigation deduce from a GPS sate1 1 ite' s ephemeris, from system, if two clocks at known coordinates A and B clock .A's location, and from received GPS time are in common-view of a single GPS satellite, receivers at these two clock sites may coinciden- decoded from the same satellite, the time differtally receive transmitted GPS clock times. By ence (Clock A - GPS time). This method is the subtracting the received times of arrivals as measured by clocks A and B at the two sites while simplest and least accurate (estimated to be compensating for the propagation delays, one has better than about 100 ns with respect to GPS an accurate measure of the time difference between time),2 but has global coverage, is in the receiveclock A and clock B. When all of the error contributions are only mode, requires no other data, yields receiver

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.

A multiple modulator fractional divider

Abstract: Based on oversampling A/D conversion technology which allows the spectrum of error energy to be shaped so that fractional synthesis error energy is pushed away from the carrier, a CMOS integrated fractional-N divider is presented. A complete fractional-N phase locked loop (PLL) which was constructed utilizing only the CMOS divider, a dual modulus prescaler, a simple loop filter, and a voltage controlled oscillator is discussed. The resulting PLL is shown to exhibit no fractional spurs. >

Micromachined thin film bulk acoustic resonators

Abstract: We have fabricated thin film bulk acoustic resonators (FBARS) with measured Q's of over 1000 and resonant frequencies as low as 1.5 GHz and as high as 7.5 GHz. The device, as currently fabricated, consists of the piezoelectric material aluminum nitride (AlN) sandwiched between electrodes all of which lie on a thin low-stress silicon nitride (Si/sub x/N/sub y/) membrane. Integrated on the membrane are small microheaters for frequency tuning and/or temperature stabilization. We have observed frequency shifts of 50 to 80 ppm per degree C depending on relative material thicknesses. Maximum temperature excursions over 580 C could be achieved using the microheaters. We have also observed frequency shifts of 5 to 10 ppm per volt depending on harmonic. >

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