S-band Signal Research Articles

Hypothesis Test-based Detection of Wi-Fi Interference on NavIC/IRNSS S-band Signal

The Navigation with Indian Constellation (NavIC)/Indian Regional Navigation Satellite System (IRNSS) is an emerging satellite navigation system that provides an independent navigation system for positioning and timing services in India and up to 1,500 km from its borderline. The dual frequency NavIC system uses the L5 frequency and S-band for navigation. These navigation signals are extremely weak and susceptible to interference when they are received on Earth's surface. Moreover, the performance of these bands may be degraded by other band or out-of-band communication systems, which can become the major threat to the performance of a NavIC receiver. The main focus of this paper is to detect real-time interference of Wi-Fi signals in the S-band of the NavIC receiver. The results are prepared with respect to the Power Spectral Density (PSD), execution of acquisition stage and the detection of Wi-Fi interference with two sample hypothesis testing methods including the Kolmogorov-Smirnov (KS)-test, the t-test and the Variance (var)-test. A performance analysis of the p-value is used to measure the evidence of interference existence for hypothesis testing, decision hypothesis and probability of detection are evaluated for each hypothesis method. The results show the severity of the Wi-Fi signal as a potential source of interference for future NavIC applications.

Perception and reduction of Wi‐Fi interference on NavIC signals

The NAVigation with Indian Constellation (NavIC) system contributes navigation solution all time during all weather conditions, anywhere within India and a region extending about 1500 km around India. The dual-band NavIC system uses the L5 and S bands for navigation. The existence of real-time Wi-Fi signal generates out of band radio frequency interference (RFI) to the S-band signal of NavIC. This interference has been perceived at particular frequencies of the S-band signal of NavIC and the reduction algorithm is proposed for this kind of interference which is based on wavelet packet decomposition. The exact spectral location of the RFI is identified and only affected interfered wavelet coefficients are processed to achieve interference reduction. The results have proven a significant amount of reduction of Wi-Fi interference in the S-band signal.

Two-pump optical parametric amplification in the S-band using a tellurite microstructured optical fiber

In this paper, two-pump optical parametric amplification (OPA) of S-band signals based on a tellurite microstructured optical fiber (MOF) is proposed and simulated. Since the length required to obtain high parametric gain reduces dramatically since, tellurite-based MOFs possess higher nonlinear parameters than those of standard silica fibers. Simulation results showing a wide and flat band with a very high gain over the S-band region which implies that tellurite-based fiber OPAs are comparable with the conventional thulium-doped fiber amplifiers. This unique feature may be used in diverse fields including satellite communication, microwave, and wireless network devices.

Ionospheric Gradients Estimation and Analysis of S-Band Navigation Signals for NAVIC System

Navigation with Indian constellation (NAVIC) is the operational name given to the Indian Regional Navigation Satellite System developed by the Indian Space Research Organisation, India. The most influential factor is ionospheric gradients that can degrade the positional accuracy of the global navigation satellite system users especially in low-latitude regions. The main aim of this paper is to estimate the ionospheric gradient variations obtained from the NAVIC receiver located at Guntur, India (16.23° N, 80.44° E). Code and carrier phase measurements of S-band (2492.028 MHz) signals are used to derive ionospheric time delays and total electron content (TEC) values. In this paper, S-band signals of NAVIC are used for the first time to investigate ionospheric gradients over low-latitude region. The recursive least squares (RLS) algorithm is implemented as a single frequency ionospheric model for estimating the absolute TEC, and longitudinal (E–W) and latitudinal (N–S) ionospheric gradients. Ionospheric gradient analysis has been carried for three consecutive days during September equinox, December solstice in 2016, and for a geomagnetic disturbed event observed during May 2017. The annual statistical analysis in the periodic structure of spatial ionospheric gradients from NAVIC S-band signals during June 2016–May 2017 is also discussed. It is evident that RLS model can estimate ionospheric gradients for a single NAVIC station. The outcome of this work would be useful for understanding ionospheric irregularities climatology over low-latitude region.

Разработка и исследование SiGe интегральных формирователей квадратурных сигналов L- и S-диапазонов

Разработка и исследование SiGe интегральных формирователей квадратурных сигналов L- и S-диапазонов

Exploring strong lunar ionosphere successfully with the service module of Chinese circumlunar return and reentry spacecraft

The existence of lunar ionosphere has been under debate for a long time. In Apollo 14 mission, the electron density detected by the charged particle lunar environment experiment (CPLEE) was 104 el/cm3 at several hundred meters high during lunar day time. In Luna-19/22 mission, the electron density profiles were detect and the peak densities were about 103 el/cm3. In the last decade, European mission SMART-1 and Japanese mission SELENE also performed radio occultation experiment for lunar ionosphere. The results of these missions don’t well-matched. In order to explore the lunar ionosphere, a very low frequency radio astronomical payload has been suggested to be sent to the surface of lunar far-side by the Chinese Chang’E-4 lunar lander mission in 2019. The payload will record the Type II solar burst, which may cover the frequency of electro-magnetic wave as low as several dozen kilo-Herz. The possible lunar ionosphere above the payload with certain electron density may truncate or block the solar burst signal as corresponding plasma frequency. To estimate the possible truncate frequencies for these observations by the new kind of payload, and to determine the lunar ionospheric distribution, an lunar radio occultation experiment with the service module of Chinese circumlunar return and reentry spacecraft has been performing. The circumlunar return and reentry spacecraft is a Chinese precursor mission for the Chinese lunar sample return mission. It was launched on 23 October 2014. After the return and reentry experiments, the service module went back into a Lunar Orbit on 11 January 2015 to image the target landing zone for the Chinese lunar sample return mission which has not yet been disclosed. During this period, the radio occultation experiments have been performed to detect the lunar ionosphere. The service module provides a stable and reliable frequency source, whose short-term stability is n ´ 10–9, for both X-band and S-band signal. The signals transmitted from the spacecraft in S and X band passed through lunar ionosphere, interplanetary plasma, Earth ionosphere and atmosphere, finally received by the ground tracking stations. According to the coherent ratio of the S/X signal, we convert the phase information of S-band signal to the frequency of X-band signal and calculate the difference of these two signal. Then, the extrapolation algorithm was used here to deduct the interference error of the earth ionosphere and the interplanetary plasma. Based on the above work, the electron column concentrations of lunar ionosphere was explored preliminary. The maximums of electron column concentrations are between 0.4 ´ 1016–0.5 ´ 1016 el/m2, are two times of the maximum result from Luna 19/22, are 1–2 orders higher than the SELENE result, but well-matched with the result from CPLEE. These results show that the lunar ionosphere is clearly exist and much stronger than we expected. The result here gives a positive support and some dynamical constrains for the scientific objective of the very low frequency radio astronomical payload onboard the Chang’E-4 lander mission. But it also raises a new question that the characteristics and formation mechanism of a stronger lunar ionosphere is remain unknown. More observations will be performed for further scientific targets.

강우 레이더 전파간섭 분석

The interference among the rain radars and interference in the adjacent wireless station due to the spurious signals from the rain radar were analyzed in this paper. The rain radar measures the rain intensity using S-band signal. The measured data are utilized in forecasting the rainfall. The interference among the rain radars or in the adjacent wireless stations may be caused by the operation with low elevation angle and the high output power. Based on the propagation analysis of S band signal and the deduced interference protection ratio of rain radar, the interference due to the rain radar are analyzed. Also, the radiation spectrum characteristics of a rain radar are deduced from the caused interference effects by the spurious signals of the rain radar. To minimize the interference effects for adjacent wireless stations, it is required to get the rejection characteristics of spurious signals above 105 dB. In viewpoints of interference for rain radars, it is necessary to operate the rain radar with a different PRF and operation time opposite to adjacent rain radars.

항공기를 이용한 텔레메트리 신호의 공중 중계시스템 개발

A telemetry signal occurs the line-of-sight problem by the effect of geography in flight test. A fixed relay system or a mobile relay system is used to solve that problem in general but we propose an airborne telemetry relay system using aircraft in this paper. An airborne telemetry relay system receives the telemetry signal of the test vehicle and then retransmits it to the ground system. The receiving antenna which is a phased array antenna can be tilted to beam direction by beam-forming and track the rapidly moving test vehicle in effect. The relay pod which is mounted to an aircraft consists of the front antenna and the side antenna. It receives S-band signal and then down-converts the frequency to L-band signal. As a result, that can remove the frequency interference on an aircraft while retransmitting.

Signal amplification in rare-earth doped heavy metal germanium tellurite glass fiber

Rare-earth doped heavy metal germanium tellurite (NZPGT) glass fibers with lower maximum phonon energy of 793 cm−1 and UV-sensitivity property have been designed and fabricated. Bright and compact upconversion traces have been observed in Er3+/Yb3+ and Tm3+/Yb3+ codoped NZPGT glass fibers, which exhibit favorable flexibility and excellent thermal stability, indicating that the NZPGT glasses are a desirable candidate for fiber amplifiers. The Er3+/Yb3+ codoped NZPGT glasses present a broad emission at ~1.5 μm with the FWHM of 72.7 nm, and the maximum internal gain of 12.59 dB with a remarkable gain coefficient of 2.38 dB/cm in the C-band were achieved in a Er3+/Yb3+ codoped NZPGT glass fiber. The efficient three-photon blue and two-photon near-IR upconversion emissions of a Tm3+/Yb3+ codoped NZPGT glass fiber demonstrate that low phonon energy NZPGT glasses have promising potential applications in Tm3+ single-doped glass fibers for S-band signal amplification, and the further development of O- and U-band fiber amplifiers and lasers in Pr3+ and Ho3+ doped NZPGT glass fibers.

High-accuracy same-beam VLBI observations using Shanghai and Urumqi telescopes

The same-beam VLBI observations of Rstar and Vstar, which were two small satellites of Japanese lunar mission, SELENE, were successfully performed by using Shanghai and Urumqi 25-m telescopes. When the separation angle between Rstar and Vstar was less than 0.1 deg, the differential phase delay of the X-band signals between Rstar and Vstar on Shanghai-Urumqi baseline was obtained with a very small error of 0.15 mm rms, which was reduced by 1–2 order compared with the former VLBI results. When the separation angle was less than 0.56 deg, the differential phase delay of the S-band signals was also obtained with a very small error of several mm rms. The orbit determination for Rstar and Vstar was performed, and the accuracy was improved to a level of several meters by using VLBI and Doppler data. The high-accuracy same-beam differential VLBI technique is very useful in orbit determination for a spacecraft, and will be used in orbit determination for Mars missions of China Yinghuo-1 and Russia Phobos-grunt.

Tm 3 + -doped ion-exchanged aluminum germanate glass waveguide for S-band amplification

K + – Na + ion-exchanged channel waveguide amplifiers have been fabricated in Tm3+-doped acid-resistant aluminum germanate glasses. The optical and relative gains of a 3.15-cm-long waveguide channel were achieved to be 4.05 and 2.29 dB at 1.482 μm wavelength under 110 mW 793 nm laser excitation, respectively. After compensating the propagation loss, an internal gain of 1.50 dB and a remarkable gain coefficient of 0.48 dB/cm were obtained, which reveals a definite S-band signal amplification in the low phonon energy glass waveguide. As an expectation, UV-radiation-sensitive glass waveguide should promote the developments of gain-flatten S-band waveguide amplifiers, infrared UV-writing grating waveguide lasers, and compact multifunctional integrated optical devices.

Double-pass high-gain low-noise EDFA over S- and C+L-bands by tunable fundamental-mode leakage loss

We demonstrate a high-gain low-noise double-pass tunable EDFA over S- and C+L-bands by discretely introducing fundamental-mode leakage loss in a 16-m-long standard C-band Er(3+)-doped fiber. The amplified spontaneous emission at the wavelengths of longer than 1530 nm can be substantially attenuated by the ASE suppressing filters to maintain high population inversion and to squeeze out the optical gain for S-band signals. When the filters are disabled, the gain bandwidth immediately returns back to the C+L-bands. Under S-band operation, a 37 dB small signal gain and a minimum 4.84 dB noise figure at 1486.9 nm are achieved with a 980 nm pump power of 154 mW.

Turbulence in the inner solar wind determined from frequency fluctuations of the downlink signals from the ULYSSES and GALILEO spacecraft

The results of several sets of measurements of the frequency of radio signals during coronal-sounding experiments carried out from 1991 to 2000 using the ULYSSES and GALILEO spacecraft are presented and analyzed. The S-band signals (carrier frequency f = 2295 MHz) were received at the three 70-m widely spaced ground stations of the NASA Deep Space Network. As a rule, the frequency-fluctuation spectra at frequencies above 1 mHz are power-laws. At small heliocentric distances, R < 10R ⊙ (R ⊙ is the solar radius), the spectral index is close to zero; this corresponds to a spectral index for the one-dimensional turbulence spectrum p 1 = 1. The index of the frequency-fluctuation spectra in the region of the supersonic solar wind at distances R > 30 R ⊙ is between 0.5 and 0.7 (p 1 = 1.5–1.7). The results demonstrate a substantial difference between the turbulence regimes in these regions: in the region of the established solar wind, the power-law spectra are determined by nonlinear cascade processes that pump energy from the outer turbulence scale to the small-scale part of the spectrum, whereas such cascade processes are absent in the solar wind acceleration region. Near the solar minimum, the change in the turbulence regime of the fast, high-latitude solar wind occurs at greater distances than for the slow, low-latitude solar wind. Spectra with a sharp cutoff at high frequencies have been detected for the first time. Such spectra are observed only at R < 10 R ⊙ and at sufficiently low levels of the electron density fluctuations. The measured cutoff frequencies are between 10 and 30 mHz; the cutoff frequency tends to increase with heliocentric distance. The variance of the plasma-density fluctuations has been estimated for the slow, low-latitude solar wind. These estimates suggest that the relative fluctuation level at distances 7 R ⊙ < R < 30 R ⊙ does not depend on heliocentric distance. The cross correlation of the frequency fluctuations recorded at widely spaced ground stations increases with the index of the frequency-fluctuation spectrum. At distances R ≈ 10 R ⊙, the rate of temporal changes in irregularities on the scale of several thousand kilometers is less than or comparable to the solar wind velocity.

Turbulence of the inner solar wind at solar maximum: Coronal radio sounding with Galileo in 1999/2000

Coronal sounding experiments were carried out using the S-band signals of the Galileo spacecraft during the period of high solar activity in 1999–2000. The parameter studied in this work is the frequency of the downlink carrier signal, which was recorded at the widely spaced ground stations of the NASA Deep Space Network. The measurements apply to both the initial thermal acceleration region of the solar wind at heliocentric distances R in the range from 5 to 10 R ⊙ ( R ⊙ = solar radius) and the extended acceleration region (10 R ⊙ < R < 50 R ⊙). Temporal spectra of the frequency measurements yield values for the intensity of the frequency fluctuations σ f, and the spectral index α f of the temporal spectra. It is found that the spectral index tends to be low ( α f ∼ 0.2–0.3) at heliocentric distances less than 10 R ⊙. The spectra steepen ( α f ∼ 0.5–0.7) at distances beyond 20 R ⊙. Furthermore, temporal spectra at solar distances R ≲ 10 R ⊙ sometimes display a sharp decrease in spectral density at fluctuation frequencies ν ∼ 0.04–0.06 Hz. The change in the plasma turbulence regime in the region of 10–20 R ⊙ evidently occurs not only during the solar activity minimum, as detected in earlier experiments, but also during times of high solar activity.

Energy Transfer and Population Inversion in Heavy Metal Oxide Glasses Doped with Tm3+ and Tb3+

Emission properties and energy transfer of PbO–Bi2O3–Ga2O3–GeO2 glasses codoped with Tm3+ and Tb3+ ions were investigated. The 1.48‐μm emission due to the Tm3+:3H4→3F4 transition can be used to amplify the S‐band (1460–1530‐nm) signal light. With Tb3+ addition, the lifetime and emission intensity of the Tm3+:3F4 level decreased sharply via the Tm3+:3F4→Tb3+:7F0,1,2 energy transfer. Population densities of the 3F4 and 3H4 levels in Tm3+ calculated from rate equations clearly verified that population inversion in Tm3+ ions became possible with as little as 0.1 mol% of Tb3+ addition.

The outer scale of solar-wind turbulence from GALILEO coronal-sounding data

Radio sounding experiments on of the solar plasma were carried out by the GALILEO spacecraft using S-band (2295 MHz) signals in 1995–1996 a period of minimum solar activity. Equatorial regions at heliocentric distances of 7–80 solar radii were studied. The frequency of the received signal was detected by three ground stations. By carrying out continuous observations of unprecedented duration and processing the data using spectral and correlation methods, we have obtained reliable information on large-scale inhomogeneities of the solar-wind density for the first time. The outer turbulence scale increases with heliocentric distance, the dependence being close to linear. We estimate the outer turbulence scale and analyze its dependence on distance from the Sun and local plasma parameters for a model in which the outer scale is formed due to competition between the linear amplification of Alfven waves in the irregular, moving solar-wind plasma and the nonlinear transfer of turbulent energy to higher frequencies. A comparison of predictions for various specific cases of this model with the observational data suggests that the main nonlinear processes responsible for the formation of the inertial range of the spectrum on the investigated scales are three-wave decay processes involving Alfven and magnetoacoustic waves.

Solar array electromagnetic scattering characteristics at S-band frequencies

Solar panel blockage is a major concern to the International Space Station S-band communication link assessment. Solar array electromagnetic scattering characteristics at S-band frequencies (2-2.3 GHz) are investigated. Both experimental and computational results indicate the solar array can be modelled as a conducting plate for S-band communication link signal strength predictions.

Efficient optoelectronic mixing at Ka-band using a mode-locked laser

The authors present optoelectronic mixing of data signals with a carrier signal in a mode-locked semiconductor laser diode. A long Fabry-Perot (FP) laser at 1.5 μm, which is monolithically integrated with an electro-absorption modulator, is mode-locked at 19.3 GHz through loss modulation. The gain section of the mode-locked laser is modulated by S-band signals. Modulation sidebands are observed in the optical domain as a result of mixing between the mode-locking and S-band communication signals. Optical up-conversion loss of 2.7 and 1.4 dB is measured for the LSB and USB. The measured spurious-free dynamic range is as high as 89 dB.Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> 3/.

A tunable microwave signal generator using magnetostatic surface wave modulation instability

A type of tunable microwave signal generator is described that utilizes the sideband induced by the modulation instability of magnetostatic surface waves propagating in yttrium iron garnet (YIG) films. Using an epitaxial 28-μm-thick and 0.4-cm-wide YIG film and a pair of identical 50-μm-wide microstrip transducers in a delay-line configuration, S-band signals are generated. The generated microwave frequency is tunable by adjustment of external biasing magnetic field. The determination of the device bandwidth is introduced.

The structure of Jupiter's Io plasma torus inferred from Ulysses radio occultation observations

The radio downlinks from Ulysses were monitored during the passage of the spacecraft through the Io plasma torus shortly after closest approach to Jupiter. The electron content of the Io torus was derived from the dispersive phase shift of the S-band (2.3 GHz) signal with respect to the X-band (8.4 GHz) signal. Corrections were applied for non-Jovian contributions to the change in electron content arising from the interplanetary medium and the terrestrial ionosphere. Ulysses' unusual North-to-South encounter trajectory was well suited for investigating the global structure of the Jovian plasma environment near Io's orbit, especially its latitudinal extent and azimuthal variations. The Io torus was found to have the same peak electron density (to within about ±20%) during the Ulysses flyby at Jupiter, as predicted by the Voyager-based models. The latitudinal scale height, however, was significantly smaller, indicating a reduction in the ion plasma temperature by a factor of 0.5 ± 0.2 with respect to the value inferred from Voyager measurements. The signal ray path sliced through bounded sectors of the Io plasma torus in front of and behind Jupiter, respectively, at different times and at different speeds. Model parameters derived from the best-fit electron content profiles for the sector restricted to Jovian System III longitudes 35° < λ III < 110° (front) differ significantly from those for the sector at 230° <λ III < 370° (rear), thereby implying longitudinal asymmetry of the Io torus.