Digital Predistortion of Millimeter-Wave Phased Array Transmitter With Over-the-air Calibrated Simplified Conductive Feedback Architecture

Tervo, Nuutti; Khan, Bilal; Kursu, Olli; Aikio, Janne; Jokinen, Markku; Leinonen, Marko E.; Juntti, Markku; Rahkonen, Timo; Pärssinen, Aarno

doi:10.1109/ims30576.2020.9224083

Cited by 6 publications

(16 citation statements)

References 15 publications

(18 reference statements)

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“…This can be also utilized when designing the FB approach. The FB architecture presented in this paper contains a FB line shared by multiple transmit paths and was originally presented in [21]. The basic concept is depicted in Fig.…”

Section: B Proposed Feedback Concept and Contributionsmentioning

confidence: 99%

“…In [21], the same modulated signal is used for both feedback calibration and DPD training. This compromises the calibration performance by focusing mostly on the main signal band (i.e.…”

Section: B Proposed Feedback Concept and Contributionsmentioning

confidence: 99%

“…This extents the calibration to cover also the adjacent bands. Furthermore, as an extension to [21] we analyze and review different feedback approaches, present three different DPD strategies that use the measurements through the proposed FB, show detailed analysis on the feedback calibration, and present the results of spatially distributed ACPR, total radiated ACPR, and the main lobe EVM, together with azimuth domain beamsteering.…”

Section: B Proposed Feedback Concept and Contributionsmentioning

confidence: 99%

“…However, DPD will be direction dependent taking into account the impacts of phase and amplitude control of each Tx path altogether. 1) Waveform Considerations for Feedback Calibration: In [21], the same 5GNR signal (100 MHz wide 256-QAM cyclic prefix (CP)-OFDM) was used for the FB calibration and DPD training. Hence, in [21] the selected training signal contains very little power on the adjacent channels.…”

Section: On-site Feedback Calibration By Ota-measurementsmentioning

confidence: 99%

“…1) Waveform Considerations for Feedback Calibration: In [21], the same 5GNR signal (100 MHz wide 256-QAM cyclic prefix (CP)-OFDM) was used for the FB calibration and DPD training. Hence, in [21] the selected training signal contains very little power on the adjacent channels. This means that when the feedback calibration coefficients were trained in [21], the calibration was not able to model the entire bandwidth of the feedback versus the OTA response.…”

Section: On-site Feedback Calibration By Ota-measurementsmentioning

confidence: 99%

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Digital Predistortion of Phased-Array Transmitter With Shared Feedback and Far-Field Calibration

Tervo¹,

Khan²,

Kursu³

et al. 2021

IEEE Trans. Microwave Theory Techn.

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Digital predistortion (DPD) of a phased array requires that multiple transmit paths must be measured by a feedback (FB) receiver (Rx). In this paper, we propose a FB concept for DPD in a time-division-duplex (TDD) phased arrays. We use a single FB line to collect the waveform samples from the parallel transmit paths to the FB Rx. The TDD switches are used to enable and disable individual transmit paths. The feedback is calibrated by comparing the FB outputs from individual PAs to over-the-air (OTA) measurement reference performed with a frequency modulated continuous wave (FMCW) signal. The individual PA measurements are post-equalized before the DPD training to model the far-field signal. Three alternative strategies are considered for training the DPD through the calibrated FB line and compared with the OTA DPD. The performance is verified by OTA measurements of a 28 GHz phased array transmitter and with fifth generation New Radio waveform in terms of total radiated (TR) adjacent channel power ratio (ACPR), cumulative absolute ACP (CACP), and main lobe error vector magnitude (EVM). The best EVM and ACPR performance is achieved by the strategy where the individual PA responses are treated independently. The methods were comparable to the OTA DPD performance, achieving all < 37 dB TRACPR, −29 dBm/MHz CACP, and ≤ 7 % EVM.

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Section: B Proposed Feedback Concept and Contributionsmentioning

confidence: 99%

“…In [21], the same modulated signal is used for both feedback calibration and DPD training. This compromises the calibration performance by focusing mostly on the main signal band (i.e.…”

Section: B Proposed Feedback Concept and Contributionsmentioning

confidence: 99%

Section: B Proposed Feedback Concept and Contributionsmentioning

confidence: 99%

Section: On-site Feedback Calibration By Ota-measurementsmentioning

confidence: 99%

Section: On-site Feedback Calibration By Ota-measurementsmentioning

confidence: 99%

See 3 more Smart Citations

Digital Predistortion of Phased-Array Transmitter With Shared Feedback and Far-Field Calibration

Tervo¹,

Khan²,

Kursu³

et al. 2021

IEEE Trans. Microwave Theory Techn.

Self Cite

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Over-the-Air Phase Calibration Methods for 5G mmW Antenna Array Transceivers

Jokinen,

Kursu,

Tervo

et al. 2024

IEEE Access

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Calibration is essential to optimize the performance of any radio transceiver during its development and manufacturing processes. This paper proposes over-the-air (OTA) calibration methods based on measuring and calibrating the phases of phased array transceiver paths. The phase responses of each signal path with all phase shifter states were characterized using an OTA radio link in the transmission and reception modes. Scattering parameter measurements give amplitude and phase responses over the frequency range, which can be converted to the delay domain with the Fourier transform. In this paper, two new delay domain phase calibration methods are presented and compared with a previously presented frequency domain method. The best performance was achieved with the relative phase calibration method in the delay domain which uses all measurement data to find the calibration values. The other two methods, i.e., the absolute phase calibration method in the delay domain and in the frequency domain, use the average phase as the calibration value. OTA radiation pattern measurements from two prototype 5G millimeter wave transceivers were used to compare the RF performances of the calibration methods, and measurements were performed with a 100 MHz 5G new radio waveform. The radiation patterns were analyzed based on direction accuracy, power level, and side lobe level, to give a few examples. The transceiver units were calibrated using the three studied methods, and while having significantly different uncalibrated performances, after calibration, both transceivers were tuned to similar performance levels.

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Embedded Near-Field Probing Antenna for Enhancing the Performance of 37–41-GHz Linear and Dual-Polarized Phased Antenna Arrays

Jin

Ayed

et al. 2023

IEEE Microw. Wireless Tech. Lett.

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Digital Predistortion of Millimeter-Wave Phased Array Transmitter With Over-the-air Calibrated Simplified Conductive Feedback Architecture

Cited by 6 publications

References 15 publications

Digital Predistortion of Phased-Array Transmitter With Shared Feedback and Far-Field Calibration

Digital Predistortion of Phased-Array Transmitter With Shared Feedback and Far-Field Calibration

Over-the-Air Phase Calibration Methods for 5G mmW Antenna Array Transceivers

Embedded Near-Field Probing Antenna for Enhancing the Performance of 37–41-GHz Linear and Dual-Polarized Phased Antenna Arrays

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