| 1. |
- Andersson, Daniel, et al.
(författare)
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Radar Images of Leaks in Building Elements
- 2015
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 78, s. 1726-1731
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Tidskriftsartikel (refereegranskat)abstract
- Through leakage in the building envelope there is a penetration of air, water vapor and particles. The degree of leakage of air can be quantified by existing methods. However, the location of adventitious openings is often not known. In order to overcome the limitations in existing methods, a non-contact and non-destructive method based on ultra-wide bandwidth radar technology is suggested. A test-bed is designed that can measure with different polarization to be able to detect flaws in different directions. Initial measurements shows promising results for further development of the method of using radar images to find leaks in building elements.
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| 2. |
- Ottosson, Patrik, et al.
(författare)
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An ultra-wideband system for measuring the dielectric properties of mineral compounds in a heat-reaction chamber at high temperatures
- 2023
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Ingår i: IEEE Transactions on Instrumentation and Measurement. - : IEEE. - 0018-9456 .- 1557-9662. ; 72
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Tidskriftsartikel (refereegranskat)abstract
- A measurement system for the measurement of microwave dielectric properties of mineral compounds at temperatures up to +1000°C is presented. It includes the simultaneous measurement of mass and temperature. Samples volumes in the range 0.01 to 0.1 m 3 can be studied. The system comprises a heat reaction chamber on a mass scale with mounted ultra-wideband (UWB) radio sensors and temperature probes. The complex refractive index is determined from the UWB signals using a technique with windowing to suppress interference and fitting of a modelled signal to the experimental ones. The developed method is validated by measuring the complex refractive index of water from +82°C down to +23°C and comparing with literature values. The systems is used to study calcination of limestone, i.e. the chemical decomposition of CaCO 3 to CaO and CO 2 when heated up to +1000°C. The chemical decomposition is clearly seen as a decrease in mass and as significant changes in the complex refractive index. The system could be used also for other mineral compounds and other types of materials.
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| 3. |
- Ottosson, Patrik, et al.
(författare)
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UWB Radio Measurement and Time-Domain Analysis of Anisotropy in Wood Chips
- 2018
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 18:22, s. 9112-9119
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Tidskriftsartikel (refereegranskat)abstract
- Ultra-wideband (UWB) radio transmission measurements have been used to determine the moisture content of wood chips using a time domain technique. Wood chips have been found to have birefringent dielectric properties acting as an anisotropic dielectric effective medium. Birefringence in wood chips occurs because of the orientation and the shape of wood chips, and microscopic structures of these objects, like wood fibers. The birefringence gives rise to two different wavefronts along the principal axes that have different dielectric properties. Each wavefront has a specific time-domain signal, that can be used to determine the moisture content. In industrial applications, for example in measurement on wood chips in trucks, the vertical polarization direction is the preferable polarization because this signal has higher signal-to-noise ratio (SNR), which makes the signal more identifiable at longer distance (2-3 m). Thus, UWB radio transmission measurement and time-domain analysis is a robust technology to investigate larger containers of wood chips and to determine the moisture content with high accuracy.
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| 4. |
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3-D band-stop FSS for X-band and Ku-band
- 2017
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Ingår i: 2017 Progress In Electromagnetics Research Symposium - Fall (PIERS - FALL). - : Electromagnetics Academy. - 9781538612118 - 9781538612125 ; , s. 671-675
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Konferensbidrag (refereegranskat)abstract
- A 3-D Frequency Selective Surface (FSS) with band-stop characteristics for X-band and Ku-band is proposed. A 3-D FSS unit cell is constructed by analyzing two 2-D FSS's. The size of the 3-D FSS unit cell is 5 mm × 5 mm wherein two layers of FR4 substrate with respective widths of 0.762 mm and 0.5 mm are used. Dual stop bands are obtained with this FSS unit cell around 10 GHz and 17.4 GHz; where a wide stop-band of 5.2 GHz is obtained. The parametric study carried out on the proposed design in terms change in nature of substrate, alternate use of different substrates and variation in angle of incidence. The 3-D FSS shows its band rejection property X-band and Ku-band respectively. Ansoft HFSS commercial EM solver software is used to carry out the simulation work.
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| 5. |
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A wideband frequency selective surface reflector for 4G/X-Band/Ku-Band
- 2018
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Ingår i: Progress In Electromagnetics Research C. - : Electromagnetics Academy. - 1937-8718. ; 81, s. 151-159
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Tidskriftsartikel (refereegranskat)abstract
- A Frequency Selective Surface (FSS) reflector with wideband response for 4G/X-band/Ku-band is proposed. The wideband FSS reflector consists of cascaded dual-layer patch FSS which is etched on separate layers of FR4 substrate. The targeted frequency range is 5–16 GHz. A wide stopband of 10.4 GHz (100% percent bandwidth) is obtained with two layers in cascade. The Equivalent Circuit (EC) method is used to approximate the simulated results. An extensive parametric study is also carried out to understand the effect of various combinations of FSS layers and their disposition. A panel of final FSS is fabricated where measured and simulated results agree well.
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| 6. |
- Alizadeh, Mahmoud, et al.
(författare)
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A new Block-Structure Modeling Technique for RF Power Amplifiers in a 2×2 MIMO System
- 2017
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Ingår i: 2017 13th International Conference on Advanced Technologies, Systems and Services in Telecommunications, TELSIKS 2017 - Proceeding. - Nis, Serbia : IEEE. - 9781538618004 ; , s. 224-227
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Konferensbidrag (refereegranskat)abstract
- A new block-structure behavioral model is proposed for radio frequency power amplifiers in a 2×2 multiple-input multiple-output system including input cross-talk. The proposed model forms kernels of blocks of different nonlinear order that correspond to the significant frequency response of measured frequency domain Volterra kernels. The model can therefore well describe the input-output relationships of the nonlinear dynamic behavior of PAs. The proposed model outperforms conventional models in terms of model errors.
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| 7. |
- Alizadeh, Mahmoud, et al.
(författare)
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A two-tone test for characterizing nonlinear dynamic effects of radio frequency amplifiers in different amplitude regions
- 2016
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Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 89, s. 273-279
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Tidskriftsartikel (refereegranskat)abstract
- A new two-tone test method for radio frequency power amplifiers is presented. The test signal is a two-tone probing-signal superimposed on large-signals of different amplitude. The amplifier is, thus, excited in different amplitude regions. The amplitude and phase of the 3rd order intermodulation (IM) products are measured vs. frequency spacing and probing-signal amplitude in each region. The IM magnitude is a measure of the nonlinearity, while the frequency dependence and asymmetry are measures of the memory effects in the different regions. A Doherty and a class-AB amplifier were tested. For both amplifiers the IM magnitude increased by ∼15 dB from the lowest to the highest amplitude region. For the Doherty amplifier the behavior of the IM products vs. frequency spacing was similar in all regions, indicating similar memory effects. For the class-AB amplifier the IM vs. frequency spacing was significantly different in the different regions, which indicates different memory effects.
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| 8. |
- Alizadeh, Mahmoud, et al.
(författare)
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Basis Function Decomposition Approach in Piece-Wise Modeling for RF Power Amplifiers
- 2018
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Ingår i: 6th Telecommunications forum TELFOR 2018. - Belgrade, Serbia : Telecommunications society. - 9781538671719 - 9781538671726 - 9781538671702
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Konferensbidrag (refereegranskat)abstract
- In this paper, a new approach is proposed to decompose the basis functions in a piece-wise modeling technique for nonlinear radio frequency (RF) power amplifiers. The proposed technique treats the discontinuity problem of the model output at the joint points between different operating points, whereas preserves the linear and nonlinear properties of the original model within each region. Experimental results show that the proposed technique outperforms the conventional piece-wise model in terms of model errors.
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| 9. |
- Alizadeh, Mahmoud, et al.
(författare)
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Behavioral modeling and digital pre-distortion techniques for RF PAs in a 3 x 3 MIMO system
- 2019
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Ingår i: International journal of microwave and wireless technologies. - : Cambridge University Press. - 1759-0795 .- 1759-0787. ; 11:10, s. 989-999
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Tidskriftsartikel (refereegranskat)abstract
- Modern telecommunications are moving towards (massive) multi-input multi-output (MIMO) systems in 5th generation (5G) technology, increasing the dimensionality of the systems dramatically. In this paper, the impairments of radio frequency (RF) power amplifiers (PAs) in a 3 x 3 MIMO system are compensated in both the time and the frequency domains. A three-dimensional (3D) time-domain memory polynomial-type model is proposed as an extension of conventional 2D models. Furthermore, a 3D frequency-domain technique is formulated based on the proposed time-domain model to reduce the dimensionality of the model, while preserving the performance in terms of model errors. In the 3D frequency-domain technique, the bandwidth of the system is split into several narrow sub-bands, and the parameters of the model are estimated for each sub-band. This approach requires less computational complexity, and also the procedure of the parameters estimation for each sub-band can be implemented independently. The device-under-test consists of three RF PAs including input and output cross-talk channels. The proposed techniques are evaluated in both behavioral modeling and digital pre-distortion (DPD) perspectives. The experimental results show that the proposed DPD technique can compensate the errors of non-linearity and memory effects in the both time and frequency domains.
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| 10. |
- Alizadeh, Mahmoud, et al.
(författare)
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Behavioural modelling and digital pre-distortion techniques for RF PAs in a 3x3 MIMO system
- 2018
-
Ingår i: International journal of microwave and wireless technologies. - 1759-0795 .- 1759-0787.
-
Tidskriftsartikel (refereegranskat)abstract
- Modern telecommunications are moving towards (massive) multi-input multi-output systems in 5th generation (5G) technology, increasing the dimensionality of the system dramatically. In this paper, the impairments of radio frequency (RF)power amplifiers (PAs) in a 3x3 MIMO system are compensated in both time and frequency domains. A three-dimensional(3D) time-domain memory polynomial-type model is proposed as an extension of conventional 2D models. Furthermore, a 3D frequency-domain technique is formulated based on the proposed time-domain model to reduce the dimensionality of the model, while preserving the performance in terms of model errors. In the 3D frequency-domain technique, the bandwidth of a system is split into several narrow sub-bands, and the parameters of the system are estimated for each subband. This approach requires less computational complexity, and also the procedure of the parameters estimation for each sub-band can be implemented independently. The device-under-test (DUT) consists of three RF PAs including input and output cross-talk channels. The proposed techniques are evaluated in both behavioural modelling and digital pre-distortion(DPD) perspectives. The results show that the proposed DPD technique can compensate the errors of non-linearity and memory effects by about 23.5 dB and 7 dB in terms of the normalized mean square error and adjacent channel leakage ratio, respectively.
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