Phase-coded pulse aperiodic transmitter coding

Abstract

Abstract. Both ionospheric and weather radar communities have already adopted the method of transmitting radar pulses in an aperiodic manner when measuring moderately overspread targets. Among the users of the ionospheric radars, this method is called Aperiodic Transmitter Coding (ATC), whereas the weather radar users have adopted the term Simultaneous Multiple Pulse-Repetition Frequency (SMPRF). When probing the ionosphere at the carrier frequencies of the EISCAT Incoherent Scatter Radar facilities, the range extent of the detectable target is typically of the order of one thousand kilometers -about seven milliseconds -whereas the characteristic correlation time of the scattered signal varies from a few milliseconds in the D-region to only tens of microseconds in the F-region. If one is interested in estimating the scattering autocorrelation function (ACF) at time lags shorter than the F-region correlation time, the D-region must be considered as a moderately overspread target, whereas the F-region is a severely overspread one. Given the technical restrictions of the radar hardware, a combination of ATC and phase-coded long pulses is advantageous for this kind of target. We evaluate such an experiment under infinitely low signal-to-noise ratio (SNR) conditions using lag profile inversion. In addition, a qualitative evaluation under high-SNR conditions is performed by analysing simulated data. The results show that an acceptable estimation accuracy and a very good lag resolution in the D-region can be achieved with a pulse length long enough for simultaneous E-and Fregion measurements with a reasonable lag extent. The new experiment design is tested with the EISCAT Tromsø VHF (224 MHz) radar. An example of a full D/E/F-region ACF from the test run is shown at the end of the paper.

The science case for the EISCAT_3D radar

“…EISCAT has always been a test bed for new ideas in coding and data analysis, whose user community has pioneered many novel applications, including new coding strategies (e.g. Virtanen et al 2009;Lehtinen et al 1998Lehtinen et al , 2008, new types of data analysis (e.g. Lehtinen and Huuskonen 1996;Virtanen et al 2008), and other applications of fundamental mathematical and statistical theory to experiment design and data taking (e.g.…”

Bayesian filtering in incoherent scatter plasma parameter fits

“…A simpler approach is to use phase-coding, for example alternating codes (Lehtinen & Häggström, 1987), and to decode the autocorrelation function samples into high resolution before the plasma parameter fit . The two-stepped approach can be accomplished with arbitrary transmission modulations if the deconvolution is performed by statistical inversion (Virtanen et al, 2008(Virtanen et al, , 2009. It is technically possible to add prior information already in the lag profile inversion step, but expressing the prior in terms of the actual plasma parameters is difficult in this approach.…”

Low power software defined incoherent scatter radar system design concept for continuous sounding the earth's ionosphere

“…4) the multi-static radar structure will be adopted which includes a central transceiving station and www.ietdl.org [20,25,26], which can be set conveniently. Owing to its low peak transmitting power (about 200 kW), the system can work continuously to scan the scheduled ionospheric volume.…”

“…Only following regulations can SDISR realise various functions. SDISR can work under multiple modes and radar waveform [20, 25, 26], which can be set conveniently. Owing to its low peak transmitting power (about 200 kW), the system can work continuously to scan the scheduled ionospheric volume.…”