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- PublicationA 0.5ps 1.4mW 50MS/s Nyquist bandwidth time amplifier based two-step flash-ΔΣ time-to-digital converterWe propose a 50-MS/s two-step flash-ΔΣ time-todigital converter (TDC) using stable time amplifiers (TAs).The TDC demonstrates low-levels of shaped quantization noise. The system is simulated in 40-nm CMOS and consumes 1.3 mA from a 1.1 V supply. The bandwidth is broadened to Nyquist rate. At frequencies below 25 MHz, the integrated TDC error is as low as 143 fsrms, which is equal to an equivalent TDC resolution of 0.5 ps.
374Scopus© Citations 2 - PublicationA 0.5V 0.5mW switching current source oscillatorThis paper proposes a new RF oscillator topology that is suitable for ultra-low voltage and power applications. By employing alternating current source transistors, the structure combines the benefits of low supply voltage operation of conventional NMOS cross-coupled oscillators together with high current efficiency of the complementary push-pull oscillators. In addition, the 1/f noise upconversion is also reduced. The 40nm CMOS prototype exhibits an average FoM of 189.5 dBc/Hz over 4–5 GHz tuning range, dissipating 0.5mW from 0.5V power supply, while abiding by the technology manufacturing rules.
493Scopus© Citations 14 - Publication1-b Observation for Direct-Learning-Based Digital Predistortion of RF Power AmplifiersIn this paper, we propose a low-cost data acquisition approach for model extraction of digital predistortion (DPD) of RF power amplifiers. The proposed approach utilizes only 1-bit resolution analog-to-digital converters (ADCs) in the observation path to digitize the error signal between the input and output signals. The DPD coefficients are then estimated based on the direct learning architecture using the measured signs of the error signal. The proposed solution is proved to be feasible in theory and the experimental results show that the proposed algorithm achieves equivalent performance as that using the conventional method. Replacing high resolution ADCs with 1- bit comparators in the feedback path can dramatically reduce the power consumption and cost of the DPD system. The 1-bit solution also makes DPD become practically implementable in future broadband systems since it is relatively straightforward to achieve an ultra-high sampling speed in data conversion by using only simple comparators.
547Scopus© Citations 14 - PublicationA 1.8–2.3 GHz broadband Doherty power amplifier with a minimized impedance transformation ratioIn this paper, the design and measurement results of a 1.8 GHz to 2.3 GHz broadband Doherty power amplifier (DPA) are reported. A modified load modulation network is designed to minimize impedance transformation ratio over the entire dynamic range for the purpose of extending the operating bandwidth. Experimental results show that the drain efficiency of the proposed DPA maintains above 50% and 63% with continuous wave input signal powers of 26 dBm and 34 dBm, respectively, from 1.8 GHz to 2.3 GHz. When stimulated by a 60-MHz, 12- carrier UMTS signal at 2.14 GHz, the proposed DPA achieved an average efficiency of 53% at 7.6 dB back-off, while the corresponding adjacent channel leakage ratio is linearized to -48.4 dBc with digital predistortion.
387Scopus© Citations 4 - PublicationA 1/f noise up-conversion reduction technique for voltage-biased RF CMOS oscillatorsIn this paper, we propose a method to reduce a flicker (1/f) noise upconversion in voltage-biased RF oscillators. Excited by a harmonically rich tank current, a typical oscillation voltage waveform is observed to have asymmetric rise and fall times due to even-order current harmonics flowing into the capacitive part, as it presents the lowest impedance path. The asymmetric oscillation waveform results in an effective impulse sensitivity function of a nonzero dc value, which facilitates the 1/f noise upconversion into the oscillator's 1/f3 phase noise. We demonstrate that if the ω0 tank exhibits an auxiliary resonance at 2ω0, thereby forcing this current harmonic to flow into the equivalent resistance of the 2ω0 resonance, then the oscillation waveform would be symmetric and the flicker noise upconversion would be largely suppressed. The auxiliary resonance is realized at no extra silicon area in both inductor-and transformer-based tanks by exploiting different behaviors of inductors and transformers in differential-and common-mode excitations. These tanks are ultimately employed in designing modified class-D and class-F oscillators in 40 nm CMOS technology. They exhibit an average flicker noise corner of less than 100 kHz.
672Scopus© Citations 105 - PublicationA 1/f noise upconversion reduction technique applied to class-D and class-F oscillatorsThe 1/f (flicker) noise upconversion degrades the close-in spectrum of CMOS RF oscillators. The resulting 1/f3 phase noise (PN) can be an issue in PLLs with a loop bandwidth of <;1MHz, which practically implies all cellular phones. A previously published noise-filtering technique [1] and adding resistors in series with gm-device drains [2] have shown significant reduction of the 1/f3 oscillator PN corner. However, the former needs an additional tunable inductor and the latter degrades PN in the 20dB/dec region.
1059Scopus© Citations 38 - Publication100% Converter-Interfaced generation using virtual synchronous generator control: A case study based on the irish systemThe increase in the use of Converter-Interfaced Generation (CIG) in the power system will require these generators to not only feed the power but also establish the voltage and maintain the grid stability. Virtual Synchronous Generator (VSG) control of the CIG is proposed to fulfill this requirement since it mimics the dynamics of synchronous generation. This paper takes the all-Island Irish transmission system as an example to investigate the frequency stability of the system as it migrates towards 100% CIG under VSG control and quantifies the minimum conditions for frequency support to sustain the system under 100% CIG. Simulations are carried out considering the worst contingency in the Irish grid which is the loss of largest infeed, namely, the disconnection of the HVDC interconnector to the UK. The results are compared and discussed considering other scenarios that include primary frequency control of conventional power plants.
91Scopus© Citations 22 - PublicationA 13C-NMR study of azacryptand complexes(Royal Society of Chemistry, 2014-07-29)
; ; ; ; An azacryptand has been solubilised in aqueous media containing 50% (v/v) dimethyl sulphoxide. 13C-NMR has been used to determine how the azacryptand is affected by zinc binding at pH 10. Using 13C-NMR and 13C-enriched bicarbonate we have been able to observe the formation of 4 different carbamate derivatives of the azacryptand at pH 10. The azacryptand was shown to solubilise zinc or cadmium at alkaline pHs. Two moles of zinc are bound per mole of azacryptand and this complex binds 1 mole of carbonate. By replacing the zinc with cadmium-113 we have shown that the 13C-NMR signal of the 13C-enriched carbon of the bound carbonate is split into two triplets at 2.2 °C. This shows that two cadmium complexes are formed and in each of these complexes the carbonate group is bound by two magnetically equivalent metal ions. It also demonstrates that these cadmium complexes are not in fast exchange. From temperature studies we show that in the zinc complexes both complexes are in fast exchange with each other but are in slow exchange with free bicarbonate. HOESY is used to determine the position of the carbonate carbon in the complex. The solution and crystal structures of the zinc–carbonate–azacryptand complexes are compared.549Scopus© Citations 4 - PublicationA 15-μW, 103-fs step, 5-bit capacitor-DAC-based constant-slope digital-to-time converter in 28nm CMOS(IEEE, 2017-12-26)
; ; ; ; ; This paper proposes a power-efficient capacitor-array-based digital-to-time converter (DTC) using a constant-slope approach. Fringe-capacitor-based digital-to-analog converter (C-DAC) array is used to regulate starting supply voltage of the constant slope fed to a fixed threshold comparator. The proposed DTC consumes only 15 μW from a 1V supply, while achieving fine resolution of 103 fs when running at 40 MHz. The measured INL and DNL are 0.73/0.35 LSB within a 5-bit range. The DTC achieves the best figure-of-merit of 8.5 fJ among state-of-the-art when normalizing the product of power and INL to the product of input frequency and range.641Scopus© Citations 12 - Publication1916 then and now: reflections on the spatiality of the Rising's urban legaciesConcerns about destruction and the shaping of the urban environment, so evident in 1916, manifested themselves in a very different way a century later. In the immediate aftermath of the Rising, many buildings were entirely or partially destroyed, congregational spaces in the city such as the General Post Office and Clery’s Department Store were badly damaged, and livelihoods were jeopardised as many workplaces and tools of work were damaged or looted. The most pressing concern a century ago was restitution to repair the damage and erase the material and visual legacy of the Rising so that the O’Connell Street area could be reopened for business as swiftly as possible. A campaign to this end transcended all political divisions as the British government underwrote the property losses occasioned by the Rising. In 2016, ‘destruction’ is still an important motif as heritage campaigners vigorously oppose redevelopment plans for the greater O’Connell Street area – including Moore Street, Moore Lane, and Henry Lane – lest they imperil buildings that they claim are central to the history and commemoration of the 1916 Rising.
180 - PublicationA 19S proteasomal subunit cooperates with an ERK MAPK-regulated degron to regulate accumulation of Fra-1 in tumour cellsFos-related antigen-1 (Fra-1) is a member of the Activator Protein-1 (AP-1) transcription factor superfamily that is overexpressed in a variety of cancers, including colon, breast, lung, bladder and brain. High Fra-1 levels are associated with enhanced cell proliferation, survival, migration and invasion. Despite its frequent overexpression, the molecular mechanisms that regulate the accumulation of Fra-1 proteins in tumour cells are not well understood. Here, we show that turnover of Fra-1, which does not require ubiquitylation, is cooperatively regulated by two distinct mechanisms—association with the 19S proteasomal subunit, TBP-1, and by a C-terminal degron, which acts independently of TBP-1, but is regulated by RAS–ERK (extracellular signal-regulated kinase) signalling. TBP-1 depletion stabilized Fra-1 and further increased its levels in tumour cells expressing RAS–ERK pathway oncogenes. These effects correlated with increased AP-1 transcriptional activity. We suggest that during Fra-1 degradation, association with TBP-1 provides a mechanism for ubiquitin-independent proteasomal recognition, while the C terminus of the protein regulates its subsequent proteolytic processing.
366Scopus© Citations 21 - PublicationA 2.0–2.5 GHz frequency-selectable oscillator for digital predistortion model identification of RF power amplifiersThis paper presents the design of a frequency selectable oscillator used as part of a new data acquisition architecture for digital predistortion (DPD) of RF power amplifiers (PAs). The proposed architecture aims to alleviate the requirement of high sampling rate analog-to-digital-converters (ADCs) in the data acquisition loop. The oscillator utilizes switchable capacitors with a digital control scheme and is capable of operating between 2.0 GHz and 2.5 GHz with an approximate frequency step size of 512 kHz.
322Scopus© Citations 1 - Publication2.7 Ga plume associated VMS mineralization in the Eastern Goldfields Superterrane: insights from the Ag-Zn-(Au) Nimbus depositEconomic volcanic - hosted massive sulfide (VHMS) deposits of the Archean Yilgarn Craton, Western Australia, are restricted to zones of juvenile crust as revealed through regional Nd, Pb and Hf isotopic variations and the geochemistry of felsic volcanic rocks. Interpreted as Archean paleo - rift zones, one of these runs N - S through the Eastern Goldfields Superterrane (broadly coincident with the Kurnalpi Terrane) and is associated with the high grade ca. 2690 Ma Teutonic Bore, Jaguar and Bentley deposits, plus sub - economic VHMS mineralization further south. To date, only small, historic Cu deposits (e.g. Anaconda) and barren pyritic lenses have been recognised in the older 2.7 Ga plume - dominated lower stratigraphy of the Eastern Goldfields.
169 - Publication2010 EFFoST Annual Meeting, DublinThe 2010 Annual Meeting of the European Federation of Food Science and Technology (EFFoST) took place in Dublin, Ireland on 10-12 November. Twenty four papers and 275 posters were presented, and there were 290 attendees. The theme of the Conference was 'Food and Health'. There were five oral sessions: (i) Nutrition and Health; (ii) Functional Foods [a]; (iii) Functional Foods [b]; (iv) Processing for Healthy Foods, and (v) Food Safety and Health. The poster sessions corresponded to these themes.
311 - Publication2011 EFFoST Annual Meeting, BerlinThe 2011 European Federation of Food Science and Technology (EFFoST) conference took place in Berlin, Germany on 9-11 November. The conference programme centred on food process-structure-function relationships and the content was closely allied to the research agenda of the European Technology Platform: Food for Life. There were 16 keynote/review lectures, 38 other oral presentations, 260 posters, and close to 300 attendees. The oral sessions corresponded to the process-structure-function themes as did the poster sessions.
319 - Publication20|20 Centenary: How the compromise of the ‘Partition Act’ created a long legacy for Ireland, north and southLegal and historical analysis of the Government of Ireland Act 1920.
44 - PublicationA 28-GHz Switched-Filter Phase Shifter with Fine Phase-Tuning Capability Using Back-Gate Biasing in 22-nm FD-SOI CMOSThis paper introduces a phase shifter based on switched filters for mm-wave 5G MIMO transmitters. It is realized in 22 nm FD-SOI CMOS and exploits the use of back-gate biasing. The new approach features strong tolerance to process, voltage and temperature (PVT) variations and thus can maintain low phase error with fine phase tuning capability supporting a large bandwidth. Measurement results show that the 4-bit phase shifter achieves 3.5° rms phase error at 28 GHz. The proposed phase shifter can maintain <5° of the worst-case rms phase error when operating across 24 to 29.5 GHz resulting in 20.56% fractional bandwidth which is the largest among the published switched-filter phase shifters to date.
128Scopus© Citations 1 - Publication28/38 GHz Dual-band Dual-polarized Highly Isolated Antenna for 5G Phased Array ApplicationsThis paper proposed a new dual-band dual-polarized array antenna operating at 28 GHz and 38 GHz for 5G communication applications. Three stacked patches are adopted to achieve the dual-band operation. The lower band from 27.48 to 28.50 GHz is achieved by using the lower large patch, which is couple-fed by the middle patch. While the upper band from 36.94 to 40.43 GHz is achieved by using the middle and upper patches. The two patches resonant at 38 and 40 GHz respectively and the two resonant modes coupled together, which greatly enhances the upper band. To increase the polarization isolation in the lower band, a shorting pin connecting the lower patch and ground is utilized. Taking advantages of the multi-layer technology, the position of the vertical feeding probe between the middle patch and lower patch is slightly shifted to ensure the good impedance matching in both lower band and upper band. For the antenna element, the simulated -12 dB bandwidths are 27.48-28.50 GHz and 36.94-40.43 GHz for the two bands, respectively. The in-band gains are over 6 dBi in the lower band, and over 4 dBi in the upper band. For the 2×2 antenna array, the isolations are better than 20 dB in both bands.
1431Scopus© Citations 11 - Publication2D distinct element modeling of the structure and growth of normal faults in multilayer sequences : 2. Impact of confining pressure and strength contrast on fault zone growth and geometryThe growth of normal faults in periodically layered sequences with varying strength contrast and at varying confining pressure is modeled using the Distinct Element Method. The normal faulting models are comprised of strong layers (bonded particles) and weak layers (non-bonded particles) that are deformed using a predefined fault at the base of the sequence. The model results suggest that faults in sequences with high strength contrast at low confining pressure are highly segmented due to different types of failure (extension vs. shear failure) in the different layers. The degree of segmentation decreases as the strength contrast decreases and confining pressure increases. Faults at low confining pressure localize as extension (Mode I) fractures within the strong layers and are later linked via shallow dipping faults in the weak ones. This leads to initial staircase geometries that, with increasing displacement, cause space problems that are later resolved by splaying and segmentation. As confining pressure increases the modeled faults show a transition from extension to hybrid and to shear fracture and an associated decrease in fault refraction, with a consequent decrease in fault surface irregularities. Therefore the mode of fracture, which is active in the strong layers of a mechanical multilayer at a particular confining pressure, exerts an important control on the final fault geometry.
430Scopus© Citations 51 - Publication2D distinct element modeling of the structure and growth of normal faults in multilayer sequences : 1. Model calibration, boundary conditions, and selected resultsThe distinct element method is used for modeling the growth of normal faults in layered sequences. The models consist of circular particles that can be bonded together with breakable cement. Size effects of the model mechanical properties were studied for a constant average particle size and various sample widths. The study revealed that the bulk strength of the model material decreases with increasing sample size. Consequently, numerical lab tests and the associated construction of failure envelopes were performed for the specific layer width to particle diameter ratios used in the multilayer models. The normal faulting models are composed of strong layers (bonded particles) and weak layers (nonbonded particles) that are deformed in response to movement on a predefined fault at the base of the sequence. The modeling reproduces many of the geometries observed in natural faults, including (1) changes in fault dip due to different modes of failure in the strong and weak layers, (2) fault bifurcation (splaying), (3) the flexure of strong layers and the rotation of associated blocks to form normal drag, and (4) the progressive linkage of fault segments. The model fault zone geometries and their growth are compared to natural faults from Kilve foreshore (Somerset, United Kingdom). Both the model and natural faults provide support for the well-known general trend that fault zone width increases with increasing displacement.
828Scopus© Citations 62