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Through the Lens of Color: An Interview with Gareth Doherty, Author of Paradoxes of Green: Landscapes of a City-State
No full textThis interview by Mark Tirpak with Gareth Doherty of Harvard University Graduate School of Design, focuses on his Paradoxes of Green: Landscapes of a City-State (University of California Press, 2017). With Paradoxes of Green (2017) and via the interview, Doherty recounts some of the findings of his ethnographic fieldwork in the Kingdom of Bahrain and describes tensions arising from differing conceptions of what ‘green’ means or signifies within this growing and predominantly arid region. An argument that Doherty makes in Paradoxes of Green (2017) is that color and form are interlinked, and that color deserves deeper consideration by policy-makers and other formal shapers of cities. The interview draws from Paradoxes of Green (2017) to discuss some of Doherty’s findings as well as his latest work on the intersections between landscape architecture and anthropology.Version of Recor
Through the Lens of Color: An Interview with Gareth Doherty, Author of Paradoxes of Green: Landscapes of a City-State
No full textThis interview by Mark Tirpak with Gareth Doherty of Harvard University Graduate School of Design, focuses on his Paradoxes of Green: Landscapes of a City-State (University of California Press, 2017). With Paradoxes of Green (2017) and via the interview, Doherty recounts some of the findings of his ethnographic fieldwork in the Kingdom of Bahrain and describes tensions arising from differing conceptions of what ‘green’ means or signifies within this growing and predominantly arid region. An argument that Doherty makes in Paradoxes of Green (2017) is that color and form are interlinked, and that color deserves deeper consideration by policy-makers and other formal shapers of cities. The interview draws from Paradoxes of Green (2017) to discuss some of Doherty’s findings as well as his latest work on the intersections between landscape architecture and anthropology
Helping children think: Gaze aversion and teaching
No full textLooking away from an interlocutor's face during demanding cognitive activity can help adults answer challenging arithmetic and verbal-reasoning questions (Glenberg, Schroeder, & Robertson, 1998). However, such `gaze aversion' (GA) is poorly applied by 5-year-old school children (Doherty-Sneddon, Bruce, Bonner, Longbotham, & Doyle, 2002). In Experiment 1 we trained ten 5-year-old children to use GA while thinking about answers to questions. This trained group performed significantly better on challenging questions compared with 10 controls given no GA training. In Experiment 2 we found significant and monotonic age-related increments in spontaneous use of GA across three cohorts of ten 5-year-old school children (mean ages: 5;02, 5;06 and 5;08). Teaching and encouraging GA during challenging cognitive activity promises to be invaluable in promoting learning, particularly during early primary years
Wideband Digital Intensive Doherty Concepts
No full textMany applications require wide bandwidth transmitters, but unfortunately, they usually have way less than 50% average drain efficiency for their modulated signals. This low efficiency is a significant drawback in all wireless applications, both for battery power devices and base stations. The Doherty radio frequency (RF) power amplifier architecture is widely used to enhance the average efficiency for modulated signals in base stations. Its popularity is due to its relatively cheap and simple hardware and its suitability to handle high-power wideband modulated signals. However, even Doherty amplifiers often have less than 50% average efficiency and are restricted in their RF bandwidth.This thesis reviews recent research on the Doherty power amplifier (DPA) topology and discusses possible power and bandwidth efficiency improvements. In the second part of the thesis, another topology is introduced, which also provides Doherty-like behavior. That topology is called a Pseudo Doherty Load Modulated Balanced Amplifier (PD-LMBA). The performance of PD-LMBA is compared with “conventional” DPAs. Circuit design examples of DPA and PD-LMBA are given. The thesis concludes with a PD-LMBA prototype design, which appears to be very promising in its wideband performance.Electrical Engineering | Microelectronic
A Wideband Two-Way Digital Doherty Transmitter in 40nm CMOS
No full textA 40nm CMOS wideband digital Cartesian push-pull inverted Doherty operating in class-E is presented. Wideband Doherty operation is achieved over a 1.9-to-3GHz frequency band, using an off-chip power combining network. The fully digital transmitter (DTX) provides 25.3dBm peak power with a drain/DTX line-up efficiency (DE/SE) of 58.7%/44.9%, respectively, at 2.4GHz. When operated with a 160MHz 256-QAM OFDM signal, it achieves 46.1%/32.7% average DE/SE, with an ACLR and EVM better than −40.6dBc and −33.9dB, respectively, using a simple memory-less digital pre-distortion (DPD).Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic
A Highly Linear Wideband Polar Class-E CMOS Digital Doherty Power Amplifier
No full textThis article presents the first application of a digital-intensive intrinsically linear digitally controlled class-E technique in a Doherty configuration. By careful nonlinear segmentation and multiphase RF-clocking along with overdrive-voltage control and automatic duty-cycle correction, it is shown that even the nonlinearities related to Doherty operation can be fully handled by the underlying design such that digital predistorion (DPD) can be, in principle, omitted. The nonlinearity behavior of the whole digital Doherty power amplifier (PA) is analyzed, and closed-form equations are given to predict the AM-AM and AM-phase modulation (PM) curves. In addition, time/phase mismatch between the peak and main branches and the AM and PM signals is accurately compensated. In order to achieve the maximum intrinsic linearity, two separate chips with the same architecture, but different design parameters, are fabricated as the main and peak amplifiers in 40-nm bulk CMOS. To achieve a large RF bandwidth and high passive combiner efficiency, a differential low-loss, wideband Marchand balun-based Doherty power combiner, implemented using reentrant coupled lines with independent second-harmonic control is proposed, and together with the matching network is fabricated on a two-layer PCB. The measured peak/6-dB power backoff P OUT, drain efficiency/power-added efficiency at 2.4 GHz are 17.5 dBm/12.2 dBm, 57%/52% and 36%/25% with VDD main/peak = 0.6 V/0.7 V. Measured results without using DPD show -41-dBc adjacent channel power ratio (ACPR) and -36-dB error vector magnitude (EVM) for a 16-MHz OFDM signal at 2.5 GHz. By using DPD, the measured ACPR and EVM of a 16-MHz/32-MHz OFDM signals are -52 dBc/-48 dBc and -50 dB/-48 dB, respectively.Accepted author manuscriptElectronic
A Millimeter-Wave CMOS Series-Doherty Power Amplifier With Post-Silicon Inter-Stage Passive Validation
No full textThis article presents a wideband series-Doherty power amplifier (SDPA) for millimeter-wave (mm-wave) fifth-generation (5G) applications. It features a compact two-step impedance inverting-based series-Doherty power combiner that provides broadband close-to-perfect power back-off (PBO) efficiency enhancement. The amplitude-to-amplitude (AM-AM)/amplitude-to-phase (AM-PM) performance of the load-modulated Doherty power amplifier for broadband operation is analyzed. We also devise a post-silicon inter-stage passive validation (PSIV) approach to evaluate the mm-wave chip prototype utilizing the embedded voltage root mean square detectors. The proposed SDPA is realized in a 40-nm bulk CMOS, and it delivers 20.4 dBm PSAT with 39.1%/34% PAE at 0-/6-dB PBO. Over a 23.5-30 GHz band, its PAE is >24% at 6-dB PBO. At 27 GHz, applying a '2 GHz 16-quadratic-amplitude modulation (QAM) orthogonal frequency-division multiplexing (OFDM)' signal, the proposed SDPA generates 10.2 dBm average power with 18.9% average PAE. The average error vector magnitude is better than -24.5 dB without digital predistortion for a '400-MHz 64-QAM OFDM' signal while generating an average output power of 8.8 dBm with 15% PAE. The AM-AM/AM-PM of the realized SDPA is investigated by employing a '50-MHz 64-QAM OFDM' signal, validating our analysis and showing that the linearity limitation of DPAs is systematic and predictable. Utilizing the proposed PSIV approach, the frequency response of the input/inter-stage passive circuits is measured, indicating an excellent agreement with 3-D electromagnetic (EM) simulation results.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic
A 39 W Fully Digital Wideband Inverted Doherty Transmitter
No full textA high-power fully-digital Doherty transmitter (DDTX) is proposed. It features two segmented LDMOS output switch banks implemented in a custom V T -down-shifted LDMOS technology. A 40 nm CMOS controller digitally activates the individual LDMOS gate segments of the output stage at RF speed. An inverted Doherty power combiner is proposed that features non-short circuited 2 nd harmonic conditions for the main and peak switch banks to boost the RF bandwidth. To guarantee smooth output power and efficiency vs. frequency, a 2 nd harmonic trap is introduced in the power combiner, yielding an RF bandwidth of > 400 MHz. The realized demonstrator can achieve over 39 W peak output power. Its highest drain and system efficiencies, respectively 60 % and 57 %, were found at 34.2 W of output power, while in power back-off its peak drain and system efficiencies are 52 % and 48 % respectively. Over a 25 dB output range, the system efficiency is within 4 percent points of the drain efficiency.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic
A Wideband Four-Way Doherty Bits-In RF-Out CMOS Transmitter
No full textWe present a wideband, 12-bit four-way Doherty Cartesian digital transmitter (DTX) featuring an innovative 50%-LO signed I/Q interleaved up-conversion technique that enables close to perfect orthogonal I/Q summation. The DTX incorporates a compact four-way lumped-element Doherty power combining network to enhance its average efficiency at deep power back-off (DPBO). It comprises a signed second-order hold (SOH) interpolation filter to suppress the sampling spectral replicas significantly. The proposed DTX is realized in a 40-nm bulk CMOS and delivers a peak output power of 27.54 dBm with drain and system efficiencies of 46.35% and 30.77%, respectively, at 5.3 GHz. At 12 dB DPBO, the realized DTX demonstrates a drain efficiency (DE) of 41.74%-39.27% in a 5.2-5.5 GHz band, respectively. Its intrinsic I/Q image, LO leakage, and C-IMD3/H 3BB for a 200 MHz tone spacing over a 4.8-6.2 GHz band are-64,-65, and-69 dBc, respectively, without calibration. Applying a simple memoryless 2× 1-D digital pre-distortion, its error vector magnitude and adjacent channel leakage ratio are lower than-31 dB and-39 dBc, respectively, for a six-carrier '40 MHz 256-QAM OFDM' signal with 18 dBm average output power and a 41% average DE. The signed SOH functionality is verified employing a four-carrier '80 MHz 512-QAM OFDM' signal with spectral purity of better than-35 dBc, while its baseband sampling frequency is 675 MHz.Accepted author manuscriptElectronic
A 26GHz Balun-First Three-Way Doherty PA in 40nm CMOS with 20.7 dBm Psat and 20dB Power Gain
No full textThis paper presents a 40nm CMOS mm-wave 3-way Doherty power amplifier (PA) suitable for 5G mm-wave transmitters. It features a bandwidth-enhanced technique using a compact single-supply balun-first 3-way Doherty combiner. The realized front-end with a core area of 0.77 mm2delivers a peak power/gain of more than 20 dBm/16 dB and a drain efficiency (DE) of better than 15 %/22 %/33 % at 9.5 dB/6 dB/0 dB power back-off across a 24-to-30 GHz band. At 26 GHz, it achieves an EVM/ACLR of -23.5 dB/-29.5 dBc for an 800MHz 64-OFDM signal with 9.8 dBm average output power and a 15 % average DE.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic
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