This study presents a simple yet ingenious transmit diversity technique (so-called hybrid codes) for phased array radar. Its main property is the capability of digital beamforming on transmit just like with a set of orthogonal signals employed by coherent multiple-input–multiple-output radar and simplicity (only one waveform has to be generated in time). The performance of the hybrid codes is examined by analysing the transmit ambiguity functions containing beampatterns and range profile for all angular directions of interest.@en

This paper outlines the work on the design of a reconfigurable receiver for the PARSAX radar. The FPGA based digital receiver samples incoming signals at intermediate frequency (IF) and processes signals digitally instead of using more conventional analog approaches. In this way it offers more robust system stability and avoids unnecessary multi-channel calibrations of analog circuits. The processing algorithms implemented in the FPGA chips can be reconfigured adaptively regarding to different transmitted waveforms, and without changing of hardware. The successful development of reconfigurable receiver has been verified by experiment and yields maximum flexibility for the whole radar system.@en

This paper describes a new type of sounding signals for polarimetric FMCW radar and the corresponding signal processing technique. The inter-period compensation (IPC) algorithm is proposed for isolation increase in radar channels. The novelty concerns the use of orthogonal polarizations of two bi-cyclic LFM-signals having an additional phase shift every second sweep. Summation units proposed for use in the receiver channels allows for reducing the effects of interfering signals due to the specified phase of received signals over two consecutive sweep times.@en

The article describes the IRCTR PARSAX radar system. It is an S-band high-resolution Doppler polarimetric FMCW radar utilizing dual-orthogonal sounding signals. The signals allow for measuring in one sweep all elements of the radar targets polarization scattering matrix simultaneously. PARSAX characteristics are: modular system set-up, highly-optimised linearity and sensitivity of the RF front-end receiver, use of a flexible multi-channel arbitrary waveform generator as sounding waveforms source, high-resolution analogue to digital conversion of the received signals at sufficiently high intermediate frequency and FPGA-based programmable digital multi-channel receiver. The paper shows that PARSAX is a unique radar research platform for studying arbitrary sounding waveforms with bandwidth up to 50 MHz and processing algorithms in Doppler-polarimetric radar.@en

This paper presents design and practical implementation of the method for cross-channel interference suppression in polarimetric LFM-CW radar with dual-orthogonal sounding signals. Simultaneously transmitted and received signals have limited orthogonality, what results in the interfering signals in the processing channels of the radar receiver. The suppression of the interfering signals is implemented in real time, characterized by simplicity and low increase of computational resources. The efficiency of the cross-channel interference suppression is demonstrated experimentally.@en

This paper describes a new type of sounding signals for polarimetric FMCW radar and the corresponding signal processing technique. This technique coordinates continuous transmission of two bi-cyclic LFM-signals on orthogonal polarizations and applies an advanced de-ramping processing on receive. The first signal consists of two identical LFM-signals; the second one has time shift relatively first and is composed by the same LFM-signal and its copy having negative sign. The time between the components of sounding signal prevents the frequency overlap between polarimetric components of scattered signal in the branches of every polarimetric radar channel. Thanks to this frequency gap between the signals in every time instant, a high-isolation level in polarimetric FMCW radar channels can be provided. However, the use of two LFM-signals having the same form but a relative time shift can decrease the unambiguity range, because the delayed signals scattered by far-located objects (interfering signals) can be determined as useful signals scattered by close-located objects in a cross branch in a polarimetric radar channel. The use of the proposed bi-cyclic LFM-signals and the additional summation units in the de-ramping filter allows the suppression of these interfering signals due to the phase sign change of the beat signals. As result, the developed de-ramping processing technique can be used in polarimetric FMCW radar receiver providing high-level cross-channels isolation without unambiguity range degradation for estimation of all elements of the radar target scattering matrix.@en