Spectrum analyzer

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

A frequency doubling electro-optic modulation system for Pockels effect measurements: Application in LiNbO3

Abstract: A novel system is presented which is capable of measuring with high accuracy the linear (Pockels) electro-optic effect by means of a new dynamic (ac) method. This method is based on the observation of the photodetected output obtained from a Senarmont-type ellipsometric system with an ac (modulating) voltage being applied onto the electro-optic sample under test. This observation is made on a high sensitivity oscilloscope and allows us to determine accurately the null point of the system by locating the position of the analyzer that produces in the output a characteristic and abrupt doubling of the (modulation) frequency. By locating this frequency doubling position without and with electric field one can finally determine the corresponding electro-optic coefficients. Theoretical analysis and considerations of practical interest are presented in the article and show that the system in question can ensure reduced errors and increased sensitivity. Also, experimental evidence in support of the expected performance is obtained by implementing and applying the system for the measurement of the composite electro-optic coefficient rc of LiNbO3 for various temperatures in the range of 17–20 °C.

RF Spectrum analyzer

Abstract: Apparatus is provided comprising a laser source, a collimating lens, a focussing lens and a detector array disposed along an optical path. A surface acoustic wave transducer is disposed between the collimating and focussing lenses and is adapted to modulate laser light provided by the laser source as a function of the amplitude and frequency of energy applied to the transducer. In accordance with the invention, a 90° Bragg diffraction grating disposed between the collimating lens and the transducer, is adapted for transmitting light of a predetermined frequency and predetermined polarization along the optical path. A specific embodiment incorporates the components on an integrated circuit chip.

Identification of sampled data systems at frequencies beyond the Nyquist rate

Abstract: A practical algorithm is presented for identifying the dynamics of a continuous-time, linear, time-invariant system, embedded in a sampled feedback loop with fixed sample time, T It is shown that if the closed-loop configuration is stable, it is rather straightforward to design a set of experiments using a spectrum analyzer that will identify the plant transfer function to frequencies well beyond the Nyquist frequency Experimental results are included >

Real-time absolute frequency measurement of continuous-wave terahertz radiation based on dual terahertz combs of photocarriers with different frequency spacings

Abstract: Real-time measurement of the absolute frequency of continuous-wave terahertz (CW-THz) radiation is required for characterization and frequency calibration of practical CW-THz sources. We proposed a method for real-time monitoring of the absolute frequency of CW-THz radiation involving temporally parallel, i.e., simultaneous, measurement of two pairs of beat frequencies and laser repetition frequencies based on dual THz combs of photocarriers (PC-THz combs) with different frequency spacings. To demonstrate the method, THz-comb-referenced spectrum analyzers were constructed with a dual configuration based on dual femtosecond lasers. Regardless of the presence or absence of frequency control in the PC-THz combs, a frequency precision of 10−11 was achieved at a measurement rate of 100 Hz. Furthermore, large fluctuation of the CW-THz frequencies, crossing several modes of the PC-THz combs, was correctly monitored in real time. The proposed method will be a powerful tool for the research and development of practical CW-THz sources, and other applications.

Simple photonics-based system for Doppler frequency shift and angle of arrival measurement.

Abstract: A novel photonic approach for simultaneously measuring both the Doppler frequency shift (DFS) and the angle of arrival (AOA) of a microwave signal in a radar system is presented. It has the same structure as a fiber optic link consisting of a laser, an optical modulator and a photodetector. The incoming microwave signal and a reference signal are applied to the optical modulator. Beating of the echo and reference signal sidebands at the photodetector generates a low-frequency electrical signal. The DFS and the AOA can be determined from the frequency and the power of the low-frequency electrical signal measured on an electrical spectrum analyzer. The system has a very simple structure and is low-cost. It has a wide operating frequency range and a robust performance. Experimental results demonstrate a DFS measurement at around 15 GHz with errors of less than ±0.2 Hz, and a 0° to 90° AOA measurement with less than ±1° errors.