| 1. |
- Sezgin, Ibrahim Can, 1992, et al.
(författare)
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A Flexible Multi-Gbps Transmitter Using Ultra-High Speed Sigma- Delta-over- Fiber
- 2018
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Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. ; 2018-June, s. 1195-1198
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Konferensbidrag (refereegranskat)abstract
- Sigma-delta-over-fiber (SDoF) using high speed-low cost optical components for datacom enables high speed transmission at X-band. This paper examines the limitations of SDoF in terms of maximum frequencies and highest bit rates. Different modulation formats, symbol rates and carrier frequencies are investigated. A high speed 850 nm vertical-cavity surface-emiting-laser (VCSEL) is used as an optical source to transmit the optical signal over a 50 meter, OM4, multimode fiber (MMF). Error vector magnitude (EVM) less than 6% is achieved at a 12-GHz center frequency for a 8-Gbps QAM256 modulated signal.
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| 2. |
- Sezgin, Ibrahim Can, 1992, et al.
(författare)
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A Low-Complexity Distributed-MIMO Testbed Based on High-Speed Sigma-Delta-Over-Fiber
- 2019
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 67:7, s. 2861-2872
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Tidskriftsartikel (refereegranskat)abstract
- Distributed multiple-input-multiple-output (D-MIMO) is a very promising technique to improve capacity and quality of service for emerging 5G systems. In this paper, we propose a flexible and low-cost testbed for D-MIMO systems, where a sigma-delta over fiber (SDoF) solution is proposed to address the fundamental challenge of phase-coherent transmission between multiple distributed access points (APs) from a central unit (CU). Employing low-cost standardized optical data interconnects, SDoF, brings a very flexible and software controlled transmission of RF signals over optical fiber. An SDoF-based D-MIMO testbed with a CU feeding 12 distributed APs has been realized and experimentally evaluated. Initial experiments of D-MIMO and conventional colocated MIMO systems at 2.365 GHz have been performed to demonstrate the flexibility and potential of the proposed testbed as a new powerful tool in the design and analysis of emerging communication system concepts.
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| 3. |
- Sezgin, Ibrahim Can, 1992, et al.
(författare)
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Effect of VCSEL Characteristics on Ultra-High Speed Sigma-Delta-Over-Fiber Communication Links
- 2019
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 37:9, s. 2109-2119
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Tidskriftsartikel (refereegranskat)abstract
- State-of-the-art high-speed multi-mode vertical-cavity surface-emitting-lasers (VCSELs) have a 3-dB analog bandwidth of ∼25 GHz and can operate up to 55 Gbps error-free, without need of equalization electronics. This makes them strong candidates as optical sources for ultra-high speed sigma-delta-over-fiber (SDoF) communication links. This paper examines the effects of VCSEL characteristics on a 32-Gbps SDoF communication link with a 50 m, OM4, multimode optical fiber. Three high-speed, 850-nm-wavelength VCSELs with oxide aperture sizes of 8.3, 6.6, and 4.6 μm were tested. The effects of different modulation voltage amplitudes and bias currents were also investigated. The link performance and VCSEL power consumption were used as figures-of-merits. By avoiding sub-laser threshold modulation for the VCSEL, each of three VCSELs could provide similar link performance. We show that, compared to conventional datacom links, eased bit-error-rate requirements enabled by bi-level nature of sigma-delta modulation makes it possible to use significantly lower VCSEL bias currents. This in turn enables a reduced VCSEL power consumption (50% lower heat-to-bit ratio) and a potential longer VCSEL lifespan. For a SDoF modulated, 160-Mbaud, QAM64 signal centered at 12 GHz an error vector magnitude of -28 dB was achieved with the VCSEL having oxide aperture size of 4.6 μm operating at only 2 mA bias current and 0.25 V modulation amplitude. This results in a heat-to-bit ratio of only 0.1 mW/Gb/s (or equivalently 0.1 pJ/b), and a current density in the VCSEL that is less than 10 kA/cm2.
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| 4. |
- Sezgin, Ibrahim Can, 1992, et al.
(författare)
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Evaluation of Distributed MIMO Communication Using a Low-Complexity Sigma-Delta-over-Fiber Testbed
- 2019
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Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. ; 2019-June, s. 754-757
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Konferensbidrag (refereegranskat)abstract
- Distributing the antennas of a base station is a method to increase the coverage and the capacity of a conventional, co-located MIMO communication system. However, physically separated antennas/access points (AP) creates a fundamental challenge of RF phase synchronization required for joint/coordinated transmission in distributed MIMO (D-MIMO) systems. In this paper we compare co-located-and distributed-MIMO wireless communication thru various measurements using a fully synchronized, low-complexity, twelve-channel testbed based on sigma-delta-over-fiber (SDoF). Single and multi-user measurements are performed in a laboratory environment and the error-vector-magnitude (EVM), the received power and signal-to-interference ratio (SIR) is calculated. We show that distributing the access points improves the received symbol EVM up to 1.6-dB and increases the coverage of the service area by delivering more uniform received power levels.
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| 5. |
- Abdulaziz, Mohammed, 1983, et al.
(författare)
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Improvement of AM-PM in a 33-GHz CMOS SOI Power Amplifier Using pMOS Neutralization
- 2019
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Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 29:12, s. 798-801
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Tidskriftsartikel (refereegranskat)abstract
- This letter presents two highly efficient two-stage power amplifiers (PAs) for 5G applications, implemented in a 22-nm slilicon on insulator (SOI) CMOS technology. High efficiency is achieved by carefully designing the power cells and optimizing the layout. Capacitive neutralization is used to improve the stability and the gain. Both PAs are similar except for the use of nMOS neutralization capacitors in the first one. In the second PA, we propose the use of pMOS capacitors instead to enhance significantly both stability and AM-PM linearity at the same time. For both PAs, the saturated output power is 12.7 dBm andP1 dB is 11.9 dBm from a 0.9-V supply at 33 GHz with a power-added efficiency (PAE) at P1 dB of more than 36%. The PAE at Psat is 38% and 40% for the PA with nMOS and pMOS neutralizations, respectively. The AM-PM up to P3 dB for the PA with nMOS neutralization is 7, and for the one with pMOS neutralization, it is less than 1.3 thanks to the proposed technique.
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| 6. |
- Baptista, Emanuel, 1993, et al.
(författare)
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Analysis of thermal coupling effects in integrated MIMO transmitters
- 2017
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Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781509063604 ; , s. 75-78
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Konferensbidrag (refereegranskat)abstract
- This paper presents a detailed analysis of thermal coupling and self-heating effects in highly integrated wireless transmitters. A MIMO transmitter prototype consisting of two closely integrated power amplifiers was built and modelled through microwave and thermal characterizations. The thermal behavior was extracted using FEM software and modelled with an equivalent RC network. The PA model was obtained experimentally using a pulsed setup. An RF-thermal simulator was developed and used with the models to predict joint thermal and electrical behavior. Measurements with modulated communication signals were done and compared with the simulator to demonstrate its feasibility for analysis of thermal effects in highly integrated transmitter applications.
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| 7. |
- Chagtmi, Nadia, et al.
(författare)
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Augmented Hammerstein model for the calibration of six-port based dual band wireless receivers
- 2019
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Ingår i: International Journal of RF and Microwave Computer-Aided Engineering. - : Hindawi Limited. - 1096-4290 .- 1099-047X. ; 29:2
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Tidskriftsartikel (refereegranskat)abstract
- Two architectures of concurrent dual-band six-port-based receiver (SPR), which are modeled and calibrated using the augmented Hammerstein model (AHM) are proposed for the first time in this article. The receivers are based on six-port junctions with one or two local oscillators (LO). The proposed single step calibration algorithms achieve the recovery of the two in-phase (I1 and I2) and quadrature (Q1 and Q2) components of an RF signal with two frequency components (RF1 and RF2). Experimental validations have been performed to verify the performance of the proposed concurrent dual-band receivers and to test the efficiency of the AHM based calibration algorithms. As a performance metric, the Error Vector Magnitude (EVM) has been measured to compare the transmitted and recovered baseband signals and to evaluate the performance and efficiency of the proposed calibration algorithms for the two receiver topologies. The IQ data has been recovered with EVMs no higher than 2% for the two LOs based receiver excited with a QAM modulated dual-band RF signal. The single LO based receiver has been tested with a dual-band LTE signal and the recovered IQ data exhibited EVMs no higher than 4%.
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| 8. |
- Chani Cahuana, Jessica, 1988, et al.
(författare)
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A new variant of the indirect learning architecture for the linearization of power amplifiers
- 2015
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Ingår i: 2015 European Microwave Conference (EuMIC). - 9782874870408 ; , s. 444-447
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Konferensbidrag (refereegranskat)abstract
- The indirect learning architecture (ILA) is the most commonly used technique for the identification of digital pre-distorters for power amplifiers (PA). A critical issue in ILA is the selection of the normalization gain used to synthesize the predistorter function. In this paper, we investigate the effects that the normalization gain has on the average output power and linearity of PAs. Moreover, we propose a new variant of the ILA that eliminates the need of a normalization gain inside the iterative loop. Experimental results show that the selection of the normalization gain affects the average output power and consequently the linearity performance of the linearized PA. If the normalization gain is not chosen correctly, the average output power of the linearized PA will differ from the average output power obtained before DPD. It is experimentally shown that the proposed ILA variant can maintain the same average output power before and after DPD. Consequently the proposed ILA variant simplifies the linearization process and allows proper evaluation of the DPD performance.
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| 9. |
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| 10. |
- Chani Cahuana, Jessica, 1988, et al.
(författare)
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Digital Predistortion Parameter Identification for RF Power Amplifiers Using Real-Valued Output Data
- 2017
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Ingår i: IEEE Transactions on Circuits and Systems II: Express Briefs. - 1549-7747 .- 1558-3791. ; 64:10, s. 1227-1231
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Tidskriftsartikel (refereegranskat)abstract
- This brief presents a novel digital predistortion (DPD) parameter identification technique that requires only the acquisition of either the in-phase (I) or the quadrature (Q) component of the power amplifier (PA) output signal. To this end, an approach that allows us to estimate the parameters of a model using only one of the IQ components of the model output is presented. Based on experimental results, it is shown that the proposed real-valued measurements based technique can offer similar linearization capabilities as its complex-valued counterparts. The experimental results also indicate that the proposed technique can be used in combination with other techniques that focus on reducing the speed of analog-to-digital converters (ADCs)
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