Topic
Spectrum analyzer
About: Spectrum analyzer is a research topic. Over the lifetime, 12217 publications have been published within this topic receiving 101851 citations.
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TL;DR: In this article, the 1/f level is found to be highly dependent on the oscillation amplitude-frequency non-linearity and the vicinity of unexcited oscillation modes.
Abstract: The nano-scale spin torque oscillator (STO) is a compelling device for on-chip, highly tunable microwave frequency signal generation. Currently, one of the most important challenges for the STO is to increase its longer-time frequency stability by decreasing the 1/f frequency noise, but its high level makes even its measurement impossible using the phase noise mode of spectrum analyzers. Here, we present a custom made time-domain measurement system with 150 MHz measurement bandwidth making possible the investigation of the variation of the 1/f as well as the white frequency noise in a STO over a large set of operating points covering 18–25 GHz. The 1/f level is found to be highly dependent on the oscillation amplitude-frequency non-linearity and the vicinity of unexcited oscillation modes. These findings elucidate the need for a quantitative theoretical treatment of the low-frequency, colored frequency noise in STOs. Based on the results, we suggest that the 1/f frequency noise possibly can be decreased by improving the microstructural quality of the metallic thin films.
36 citations
TL;DR: In this paper, the magnetic search coil (MSC) was used for magnetic field observations in a few kHz frequency range, which may cause local acceleration and/or rapid loss of radiation belt electrons.
Abstract: This paper presents detailed performance values of the Magnetic Search Coil (MSC) that is part of the Plasma Wave Experiment on board the Arase (ERG) satellite. The MSC consists of a three-axis search coil magnetometer with a 200-mm-long magnetic core. The MSC plays a central role in the magnetic field observations, particularly for whistler mode chorus and hiss waves in a few kHz frequency range, which may cause local acceleration and/or rapid loss of radiation belt electrons. Accordingly, the MSC was carefully designed and developed to operate well in harsh radiation environments. To ascertain the wave-normal vectors, polarizations, and refractive indices of the plasma waves in a wide frequency band, the output signals detected by the MSC are fed into the two different wave receivers: one is the WaveForm Capture/Onboard Frequency Analyzer for waveform and spectrum observations in the frequency range from a few Hz up to 20 kHz, and the other is the High Frequency Analyzer for spectrum observations in the frequency range from 10 to 100 kHz. The noise equivalent magnetic induction of the MSC is $$20\,{\hbox {fT/Hz}}^{1/2}$$
at a frequency of 2 kHz, and the null depth of directionality is − 40 dB, which is equivalent to an angular error less than $$1^{\circ }$$
. The MSC on board the Arase satellite is the first experiment using a current-sensitive preamplifier for probing the plasma waves in the radiation belts.
36 citations
15 Feb 1998
TL;DR: The proposed filter characterization method makes it useful to predict EMI filter performance when the filter is used in a practical power supply.
Abstract: The proposed filter characterization method makes it useful to predict EMI filter performance when the filter is used in a practical power supply. High frequency parasitic effects can also be predicted using this method. An impedance/gain-phase analyzer is needed for this approach.
36 citations
TL;DR: In this paper, a varying correction voltage is applied to the target which cancels beam energy fluctuations, and the energy spread is reduced to 250±120 ev and is probably due only to the ion source.
Abstract: A varying correction voltage is applied to the target which cancels beam energy fluctuations. This correction voltage is a known, constant multiple of a small, variable voltage which must be applied to the outer plate of an electrostatic analyzer to keep the beam centered at the analyzer image slits. The beam current at the analyzer image slits provides the signal which, when amplified by an electronic device called the Homogenizer, drives both the outer analyzer plate and the target. The energy spread is reduced to 250±120 ev and is probably due only to the ion source. If the HH+ beam is put through the analyzer, the unlimited H+ beam also has an energy spread of 250 ev. The 1.76‐Mev C13(p,γ) and 0.992‐Mev Al27(p,γ) resonances were used to test performance. Our data are consistent with Γ(C13) = 75 ev and Γ(Al27) = 100 ev. The upper limit for the C13 width is 150 ev.
36 citations
TL;DR: In this paper, an experimental study of E. coli sensing based on surface-skimming-bulk-wave delay line device fabricated on ST-cut quartz was performed for testing of water potability.
Abstract: This paper reports an experimental study of E. coli sensing based on surface-skimming-bulk-wave delay line device fabricated on ST-cut quartz. The sensor configuration consisted of an 87.7 MHz oscillator with the delay line as control element in its feedback loop. The antigen–antibody immunochemical reaction was employed on the acoustic wave device surface to generate mass loading and frequency shift. The sensor output was monitored by an RF spectrum analyzer. Highly specific sensing is demonstrated for E. coli cells up to 0.4 cells/μl in water. The methodology offers possibility for developing highly sensitive and fast E. coli sensors for testing of water potability.
36 citations