Spectrum analyzer

About: Spectrum analyzer is a research topic. Over the lifetime, 12217 publications have been published within this topic receiving 101851 citations.

Observation of 200th harmonic with fractional linewidth of 10−10 in a microwave frequency comb generated in a tunneling junction

Abstract: A microwave frequency comb with up to 200th harmonic of a laser repetition rate is generated by nonlinear intermodal mixing of 15 fs laser pulses in the junction of a scanning tunneling microscope. The highest harmonic has an output power of −146 dBm at 14.85 GHz with a signal/noise ratio of 20 dB and a measured linewidth of 1.2 Hz, which is still larger than the actual linewidth due to phase noise of the spectrum analyzer. Theory suggests that the harmonics have comparable magnitude up to terahertz frequencies, while the observed roll-off is caused by a shunting capacitance in detection circuitry.

A multi-application FFT analyzer based on a DSP architecture

Abstract: A digital signal processor (DSP)-based FFT analyzer capable of adapting its behavior according to specific application requirements was set up. A suitably designed user-interface allows both the specific application to be chosen and its main parameters to be defined. An automatic optimization procedure then reorganizes the instrument configuration in order to meet user requirements. Multi-DSP architecture implementation ensures real-time behavior. The experimental test results indicate that the instrument is capable of optimally operating in a large number of typical applications.

Pulse-doppler signal processing with quadrature compressive sampling

Abstract: Quadrature compressive sampling (QuadCS) is a recently introduced sub-Nyquist sampling scheme for effective acquisition of inphase and quadrature (I/Q) components of sparse radio frequency signals. In applications to pulse-Doppler radars, the QuadCS outputs can be arranged into a two-dimensional data format, in terms of slow time and virtual fast time, similar to that by Nyquist sampling. This paper develops a compressive sampling pulse-Doppler (CoSaPD) processing scheme which performs Doppler estimation/detection and range estimation from the sub-Nyquist data without recovering the Nyquist samples. The Doppler estimation is realized through a spectrum analyzer as in classical processing, whereas the detection is performed using the Doppler bin data. The range estimation is performed using sparse recovery algorithms only for the detected targets to reduce the computational load. A low detection threshold is used to improve the detection probability and the introduced false targets are then removed in the range estimation stage by exploiting the inherent target detection capability of the recovery algorithms. Simulation results verify the effectiveness of the proposed CoSaPD scheme, which requires only one-eighth of the Nyquist rate to achieve similar performance to the classical processing with Nyquist samples, provided that the input signal-to-noise ratio (SNR) is above −25 dB.

Method of and apparatus for predicting vehicle interior noise

Abstract: A jig is successively mounted on each of the four wheels of a vehicle. The jig is struck in three orthogonal directions independently, and at the same time, a microphone inside the vehicle measures the sound pressure of noise generated due to the exciting force. An FFT analyzer operates a frequency response function from the exciting force to the sound pressure. In a drum testing machine, a tire to be subject to noise prediction is mounted on a shaft, the tire is rotated, and the axial force in the three orthogonal directions is measured. The axial force signal is input to the FFT analyzer and the auto power spectrum in the three orthogonal directions and the cross power spectrum between two different axial directions are operated. The frequency response functions are synthesized with the auto power and cross power spectrums, and the power spectrum of the road noise is operated.

Use of a Multichannel Analyzer for Corona Pulse-Height Distribution Measurements on Cables and Other Electrical Apparatus

Abstract: A method in which use is made of a multichannel analyzer to measure the distribution of the corona pulse heights of insulating systems of various electrical apparatus such as transformers, capacitors, and cables is described. Suitable pulse-shaping circuitry is used in conjunction with an RCL-type corona pulse detector to provide a basic sensitivity level of 1 pC and corona pulse resolution limit of about 10-15 ,?s. A calibration technique is described and particular attention is given to the interpretation of calibration results obtained under high ambient noise conditions normally prevalent in electrical apparatus production areas. It is shown that electrical interference may degrade the corona charge resolution of the analyzer display to as much as 4.0 pC as compared to the half-peak width value of about 0.5 pC in the near absence of noise. Typical corona pulse-height distribution spectra obtained on solid dielectric insulated power cables are presented.