The effects of polarization rotation and phase delay with frequency on ionospherically propagated signals

Epstein, M.

doi:10.1109/tap.1968.1139242

Cited by 8 publications

(5 citation statements)

References 4 publications

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“…To analyze the effect of the dielectric constant to the cavity dimensions, we varied the dielectric constant from 4.4 to 30 and observed that the optimum cavity depth can be reduced as the value of the relative permittivity increases. After 70 years of define behavior of antennas using analytical methods, nowadays the analysis became easier than before due the actual available numerical methods for electromagnetic analysis and antenna modeling, such as Method of Moments (MoM) [1], and others used in commercial software as Computer Simulation Technology (CST) whose performance is based on the Finite Integral Technique (FIT) [2]. Pocklington equation is also used for antenna analysis which solution is obtained thru MoM; Pocklington equation is an integral which is solved using MoM, but we have changed it into a discrete equation, to define virtual currents, after measurement or calculation of field in the conductor surface.…”

Section: Resultsmentioning

confidence: 99%

“…Global positioning systems (GPSs) are widely used in various mobile system applications using signals received from GPS satellites located at an altitude of about 20,183 km. Thus, to compensate for the significant path loss with polarization mismatch in the ionosphere, these systems usually require high-gain antennas over the upper hemisphere with dual-band circular polarization (CP) characteristics [1]. To obtain high directivity in the upper hemisphere, there have been a lot of efforts made by adding a cavity structure at the bottom of the antennas, as presented in Refs.…”

Section: Introductionmentioning

confidence: 99%

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Design of a miniaturized dual-band antenna for improved directivity using a dielectric-loaded cavity

Kang

Byun

Choo

2016

Microw. Opt. Technol. Lett.

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This article proposes the design of a dual-band global positioning system (GPS) antenna using a high-permittivity dielectricloaded cavity. The cavity structure is filled with a dielectric material to miniaturize the size, and its width and depth are adjusted to maximize the front-to-back ratio for high directivity. Dual-band circular polarization characteristics are achieved by placing two radiating polygon loops at the aperture of the cavity, and the loops are electromagnetically coupled to a microstrip line for a coupled feeding network. The proposed antenna is fabricated, and its antenna characteristics are measured in a full anechoic chamber. The results demonstrate that the antenna is suitable for dual-band GPS applications with high bore-sight gain values of 3.4 dBic at 1.2276 GHz and 3.7 dBic at 1.5754 GHz.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Design of a miniaturized dual-band antenna for improved directivity using a dielectric-loaded cavity

Kang

Byun

Choo

2016

Microw. Opt. Technol. Lett.

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“…The effect can be assessed by measuring the amplitude versus frequency function, which in turn can be used to calculate the polarization bandwidth, defined as half the frequency separation between minima for a specified minimum fade depth [Salous, 1985a]. This is a modification of the earlier definition [Epstein, 1968] 4. The presence of irregularities: this induces further ordinary and extraordinary wave couplets which might cause faster fading than point 1 above.…”

Section: Single Mode Coherencementioning

confidence: 99%

Wideband measurements of coherence over an HF skywave link and implication for spread‐spectrum communication

Salous¹,

Shearman²

1986

Radio Science

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A wideband frequency-modulated, continuous-wave (FMCW) oblique incidence sounder was used in an experiment to measure the coherent bandwidth of a one-hop F 2 layer propagated ionospheric path. The experimental data were collected over a 234-km link in the United Kingdom by using frequency sweeps of up to 5 MHz repeated at 10-s intervals. The path had the characteristics of quasi-longitudinal propagation. The results indicated that the limiting factors to the coherent bandwidth are mainly polarization interference and frequency dispersion. Data on the coherent bandwidth and fade depth as a function of frequency and the time variation of the amplitude frequency response are presented.

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“…The incoming wave polarization of signals traveling over one-hop paths may vary with changes in radio frequency, the ionospheric electron density profile, and the earth's magnetic field [Breit, 1927;Nichols and Schelleng, 1925]. Variations in the incoming wave polarization with time may produce undesirable signal strength variations with time; polarization variations with radio frequency (at an instant of time) may impose a bandwidth limitation on pulsed signals where waveform preservation is important [Epstein, 1968a]. The purpose of the • The author is now with Page Communications Engineers, Inc., 7726 Old Springhouse Road, McLean, Virginia 22101. research reported here was to explore, both theoretically and experimentally, the effects of incoming wave polarization variations as a function of time, radio frequency, and path azimuth, so that the advantages of erecting specially polarized HF antennas to reduce signal distortion cotfid be weighed against the increased cost.…”

Section: Introductionmentioning

confidence: 99%

“…A possible explanation for the nearly fixed location in the spectrum of this crossing is that the ratio of MOF (F) and MOF (E) remains approximately constant a high percentage of the time.An indication of signal bandwidths beyond which signal waveshape might be distorted owing to the effects of polarization variation with frequency (at an instant of time) can be determined from the above results. This bandwidth limitation may be expessed in terms of a polarization bandwidth equal to one half the polarization-induced signal strength minimum-tominimum spacing in frequency[Epstein, 1968a]. Very small polarization bandwidths, as low as 25 kHz, occur many times during the day and night.…”

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confidence: 99%

Polarization of Ionospherically Propagated HF Radio Waves with Applications to Radio Communication

Epstein¹

1969

Radio Science

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Sweep-frequency CW radio signals transmitted over 1300-kin north-south and 1900-km east-west temperate-zone paths were received 24 hours per day for 2•-day periods. Measurements of the incoming one-hop F-layer polarization, as a function of time-of-day and radio frequency, indicate that daytime rates of change of polarization rotation with frequency (at an instant of time) average 1 turn/MI-Iz over the north-south path and 0.25 turn/MHz over the east-west path. These values are in good agreement with computer raytracing predictions of the rates of change of polarization rotation with frequency over similarly disposed paths. It was observed that nighttime polarization rotation rates are about 1 to 4 times as high as those measured during the day. It was also experimentally found that the rate of change of the incoming polarization with frequency first decreased and then increased with incoming radio frequency, the minimum rate occurring near 0.8 MOF0. Daytime rates of polarization rotation with time (at a given frequency) average 0.25 turn/min. The polarization rotation rates with time do not appear to vary either with path azimuth or transmitted radio frequency. Near-zero rates of polarization rotation with time occur for much of the nighttime period. Large fluctuations in the polarization variations occur with both time and frequency throughout the day.Polarization measurements made with signals that were reflected from a nonblanketing, nighttime sporadic E layer of about two hours duration indicate that, for this layer, circumstances other than polarization effects, probably multipath, determine much of the observed signal strength variations with frequency and time.The results suggest that for round-the-clock temperate zone propagation, when linearly polarized antennas are employed, a qualitative threshold for envelope distortion of broadband signals (due to variation in the incoming polarization with frequency) occurs when signal bandwidths exceed appro,rAmately 100 kHz for north-south paths and 400 kHz for east-west paths. The effects of such distortion may be reduced either by operating near 0.8 MOF0 or by the use of circularly polarized antennas.

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The effects of polarization rotation and phase delay with frequency on ionospherically propagated signals

Cited by 8 publications

References 4 publications

Design of a miniaturized dual-band antenna for improved directivity using a dielectric-loaded cavity

Design of a miniaturized dual-band antenna for improved directivity using a dielectric-loaded cavity

Wideband measurements of coherence over an HF skywave link and implication for spread‐spectrum communication

Polarization of Ionospherically Propagated HF Radio Waves with Applications to Radio Communication

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