Spurious Phase Modulation Research Articles

Operation algorithms and application of functional converters modulating voltage for generation of precision radio signals with angular modulation

The article presents a synthesis of algorithms and structures of functional converters modulating voltage for their use as part of quadrature radio signal generators with angular modulation. The study is an alternative method for suppressing spurious amplitude modulation and spurious phase modulation, using controlled spectrum expansion using functional converters modulating voltage. The main requirement for functional converters is the accuracy of representation of the modulating voltage in nonlinear converters by a limited number of terms of Taylor series decompositions that depend on the implemented modulation index. Functional conversion accuracy analysis, spectral analysis and technical implementation of functional converters by table method on the basis of analogue-to-digital converter, permanent memory device and digital-to-analog converter in mode of generation of phase modulation index equal to π are performed.

Hybrid Stripmap–ScanSAR Interferometry: Extension to the X-Band COSMO-SkyMed Data

This letter aims to investigate the applicability of the hybrid stripmap–ScanSAR differential synthetic aperture radar interferometry to data collected by the X-band RADAR sensors of the Italian COSMO-SkyMed (CSK) constellation. The presented analysis relies on the experiments carried out on two sets of stripmap and ScanSAR CSK images collected over the Chuquicamata copper mine in Chile and the Mojave Desert in Southern California, respectively. As a result of our investigation, a spurious phase modulation has been recognized in the generated hybrid stripmap–ScanSAR interferograms along the azimuth direction. This effect is due to the specific staggered topology of the used active phased array antennas that introduces half-wavelength residuals during the electronic antenna steering in the elevation plane. A straightforward solution to compensate for such spurious phase modulation effects has been provided, and the achieved results demonstrate its effectiveness. The outcomes of our analysis may be relevant in the perspective of the future CSK Second Generation Program.

The Effects of Transponder Imperfections on the Error Probability Performance of a Satellite Communication System

The bit error rate (BER) performance analysis of a data communication system is generally based on the assumption that signal waveforms are ideal and hardware-induced distortion is absent. In a satellite communication system, such distortion arises in the satellite repeater, as well as in the transmitter and receiver portions. NASA, which is in the process of developing its Tracking and Data Relay Satellite System (TDRSS), is very much interested in understanding the impact of numerous hardware constraints, that have been identified, on BER performance. The present paper, which treats one segment of this broad problem area, examines the cumulative impact of nine forms of distortion induced by the repeater on BPSK and QPSK signals. These include frequency offset, filter amplitude and phase ripple, phase noise, spurious phase modulation (PM), AM/AM and AM/PM conversion, incidental AM, and spurious outputs. For the present analysis, the transmitter and receiver are assumed to operate in essentially ideal fashions and thermal noise is introduced at the receiver front end only. Computed results indicate that BPSK and QPSK performances are impacted in substantially different manners, with QPSK generally more sensitive to a given form of distortion. One noteworthy example is the combined impact of the phase noise and spurious PM parameters which affect BPSK only slightly, but lead to very rapid QPSK performance degradation as the parameter values increase. This and the other distortion effects are illustrated via computed parametric performance curves. Results also demonstrate the need to account for interactions among distortion parameters.