Early results from the DNA Wideband satellite experiment—Complex‐signal scintillation

Abstract

A multifrequency (ten spectral lines between VHF and S band) coherent radio beacon is presently transmitting continuously from a 1000‐km, high‐inclination orbit for the purpose of characterizing the transionospheric communication channel. Its high phase‐reference frequency (2891 MHz) permits direct observation of complex‐signal scintillation, and its very stable, sun‐synchronous orbit allows repeated pre‐midnight observations at low latitudes and near‐midnight observations at auroral latitudes. We present here early results of the observations; salient points include the following. First, most of the data are consistent with phase‐screen modeling of the production of ionospheric scintillation, including an ƒ−2 frequency dependence for phase variance. Second, propagation theories invoking weak, single scatter seldom are adequate, because even moderate intensity scintillation usually is accompanied by phase fluctuations comparable to or greater than a radian. Third, under conditions producing GHz scintillation (near the geomagnetic equator), lower frequencies show marked diffraction effects, including breakdown of the simple ƒ−2 behavior of phase variance and loss of signal coherenceacross a band as narrow as 11.5 MHz at UHF.

Investigating high‐latitude ionospheric turbulence using global positioning system data

“…Ever since, there have been a large number of power spectral studies of amplitude scintillations monitored in different parts of the globe [Singleton, 1974;Crane, 1976;Umeki et al, 1977;Fremouw et al, 1978;Franke and Liu, 1983;Bhattacharyya and Rastogi, 1985;Basu et al, 1988].…”

On the Interpretation of Ionospheric Scintillation Data Using a Power-Law Phase Screen Model--Weak Scatter

“…Indeed, the potential of differential phase measurements has been recognized for some time as an accurate means of medsuring relative and absolute total (integrated) electron content (TEC) (Leitinger et al, 1975). (Fremouw et al, 1978). We conclude that under conditions of weak scattering the diffruction effects in the phase data :an be largely ignored.…”

A USRP2-based reconfigurable multi-constellation multi-frequency GNSS software receiver front end

“…A practical way to estimate the GPS carrier phase fluctuation caused by the oscillator, and the VCO is to measure the detrended phase output of the receiver. Fremouw et al (1978) reported weak phase scintillations with magnitude around 0.086 radians. Recent studies of high-latitude scintillations have shown many scintillation activities with phase scintillations with magnitude in similar or even smaller values (Vikram 2011).…”