On the Calibration of mm-Wave MIMO Radars Using Sparse Antenna Arrays for DoA Estimation

Dürr, André; Schwarz, Dominik; Roos, Fabian; Hügler, Philipp; Bucher, Stephan; Gruner, Patrik; Waldschmidt, Christian

doi:10.23919/eumc.2019.8910838

Cited by 19 publications

(29 citation statements)

References 8 publications

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“…It is determined using a Fourier transform of the signals along the virtual antenna positions. The virtual antenna positions are extracted by the measured relative phase progressions [21]. The measurement matches well with the simulated angular spectrum.…”

Section: B Verification Of the Quasi-coherent Phase Correctionmentioning

confidence: 60%

Calibration-Based Phase Coherence of Incoherent and Quasi-Coherent 160-GHz MIMO Radars

Dürr¹,

Kramer²,

Schwarz³

et al. 2020

IEEE Trans. Microwave Theory Techn.

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Imaging radars are usually realized fully coherently. However, the distribution of one common radio frequency signal to all transmit and receive paths requires a high degree of hardware complexity. In order to reduce the hardware effort significantly, a novel phase synchronization method for incoherent and quasi-coherent frequency-modulated continuous-wave (FMCW) imaging radars with individual signal synthesis per channel is presented. The quasi-coherent setup uses one common oscillator for all frequency synthesizers. It is shown that in the case of the quasi-coherent system, only a phase difference between the calibration and the measurement has to be corrected to achieve coherence. In comparison, an incoherent system causes additional time, frequency, and FMCW ramp slope errors due to the different behavior of the oscillators. In order to achieve phase coherence and to correct the error sources, a calibration-based method using a defined signal path as part of the radar system is proposed. The imaging radar used for verification of the theory consists of individual single-channel radar monolithic microwave integrated circuits (MMICs) at 160 GHz; each MMIC fed by an individual frequency synthesizer. As shown by measurements, it is possible to achieve phase coherence for both system approaches and to perform angle estimation.

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Section: B Verification Of the Quasi-coherent Phase Correctionmentioning

confidence: 60%

Calibration-Based Phase Coherence of Incoherent and Quasi-Coherent 160-GHz MIMO Radars

Dürr¹,

Kramer²,

Schwarz³

et al. 2020

IEEE Trans. Microwave Theory Techn.

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“…According to (3), the frequency shift depends on the unknown DoA ϑ and the VX location x VX k,φ . The latter is known from the manufacturing data or can be derived from the calibration [25]. The determination of the unknown DoA is discussed in Section V. Due to the digitization of the measurement data and a subsequent fast Fourier transform (FFT) processing, the error caused by the range-angle coupling can be efficiently corrected by a shift of the range spectra in multiples of the size of a range cell after range-Doppler processing.…”

Section: B Error Correction Methodsmentioning

confidence: 99%

“…Since the phase progression between the antennas only depends on the incident angle and not on the target distance (FF condition is fulfilled), the resulting VX position is constant. According to (1), the VX position is alternatively given by the slope of the angle-dependent phase progression [25]. However, if the NF influence applies, the VXs that hold in the FF, see (8), are no longer valid, which can be interpreted by a displacement of the VX locations, i.e.,…”

Section: A Description Of the Phase Errors Due To An Ff Violationmentioning

confidence: 99%

“…6 shows the positioning error between the VX positions in the FF and the equivalent VX positions in case of a FF violation as a function of target distance R Target and incident angle ϑ. It is derived from the phase progression [25] and shown for an exemplary antenna configuration violating the FF condition. It shows that for antennas far apart from the array center C and at short ranges, the VX positions highly depend on target distance and incident angle.…”

Section: E J 2πmentioning

confidence: 99%

See 1 more Smart Citation

Range-Angle Coupling and Near-Field Effects of Very Large Arrays in mm-Wave Imaging Radars

Dürr¹,

Schneele²,

Schwarz³

et al. 2021

IEEE Trans. Microwave Theory Techn.

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In order to improve the resolution of imaging radars, electrically large arrays and a high absolute modulation bandwidth are needed. For radar systems with simultaneously high range resolution and very large aperture, the difference in path length at the receiving antennas is a multiple of the range resolution of the radar, in particular for off-boresight angles of the incident wave. Therefore, the radar response of a target measured at the different receiving antennas is distributed over a large number of range cells. This behavior depends on the unknown incident angle of the wave and is, thus, denoted as range-angle coupling. Furthermore, the far-field (FF) condition is no longer fulfilled in short-range applications. Applying conventional signal processing and radar calibration techniques leads to a significant reduction of the resolution capabilities of the array. In this article, the key aspects of radar imaging are discussed when radars with both large aperture size and high absolute bandwidth are employed in short-range applications. Based on an initial mathematical formulation of the physical effects, a correction method and an efficient signal processing chain are proposed, which compensate for errors that occur with conventional beamforming techniques. It is shown by measurements that with an appropriate error correction an improvement of the angular resolution up to a factor of 2.5 is achieved, resulting in an angular resolution below 0.4 • with an overall aperture size of nearly 200 λ 0 .

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“…The theoretical spatial resolutions are shown in (23) and (24), where B represents the bandwidth of the transmitted signal. With a fixed system frequency and detection range, the resolution of the array direction (x-direction) is related to the transmitting and receiving arrays aperture [23].…”

Section: Sampling Criteria and Spatial Resolutionmentioning

confidence: 99%

Phase Shift Migration With SIMO Superposition for MIMO-Sidelooking Imaging at Terahertz Band

Yang

Gao

et al. 2020

IEEE Access

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In this paper, the enhanced phase shift migration (PSM) algorithm for multi-input-multioutput (MIMO) side-looking (SL) scheme was proposed for the 2-dimension (2D) fast image reconstruction in the terahertz (THz) band. By decomposing the MIMO imaging problem into a superposition of several single-input-multiple-output (SIMO) sub-arrays, the proposed algorithm can be applied to systems with randomly distributed transmitting array. By deriving and applying the modified phase shift factor and necessary phase compensation, zero-padding in the transmitting array and data reorganization in the spatialfrequency domain of the conventional wavenumber domain MIMO algorithm can be totally avoided, which will hopefully further reduce the amount of calculation. A comprehensive MIMO-SL-EPSM algorithm was established in the wavenumber domain. Proof-of-principle experiments in the 0.1-THz band were performed based on a MIMO-SL prototype system. The reconstructed images for different targets with high efficiency and quality demonstrate the theoretical results and the effectiveness of the proposed algorithm. INDEX TERMS multiple-input-multiple-output (MIMO), phase shift migration (PSM), terahertz (THz), image reconstruction algorithm.

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On the Calibration of mm-Wave MIMO Radars Using Sparse Antenna Arrays for DoA Estimation

Cited by 19 publications

References 8 publications

Calibration-Based Phase Coherence of Incoherent and Quasi-Coherent 160-GHz MIMO Radars

Calibration-Based Phase Coherence of Incoherent and Quasi-Coherent 160-GHz MIMO Radars

Range-Angle Coupling and Near-Field Effects of Very Large Arrays in mm-Wave Imaging Radars

Phase Shift Migration With SIMO Superposition for MIMO-Sidelooking Imaging at Terahertz Band

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