In this study, the authors present three different metamaterial absorbers (MMAs) namely, T, split-I (SI) and split-Jerusalem cross (SJC) with different dimensions and geometrical configurations. The ...absorption rates of T-, SI- and SJC-shaped absorbers are studied at microwave frequencies. T-shaped absorber demonstrates perfect absorption at 10.19 GHz, making it suitable for single band operation, whereas SI-shaped absorber exhibits two perfect absorption peaks at 9.32 and 10.75 GHz finding its application in dual band operation. However, novel SJC-shaped absorber demonstrates multiple absorption peaks at 9.92, 10.42, 10.93, 11.75 and 13.25 GHz with absorption of 99.5, 91, 99.9, 91.8 and 99.6%, respectively, making it suitable for X- and Ku-band operations. The proposed MMAs have a thickness of around 0.8 mm (i.e. <λ/37) with respect to the lowest frequency of operation. Furthermore, the absorbers are analysed for different angles of polarisation and incidence for transverse electric polarised wave with a step size of 15°. The proposed absorbers have been fabricated and experimentally demonstrated at X-band verifying the results obtained from simulations and implementing an equivalent circuit method. Further, SJC-shaped absorber is demonstrated for multi-and wide-band terahertz applications exhibiting four perfect absorption peaks at 2.76, 2.89, 3.02 and 3.31 THz.
The high penetration of renewable energy (RE) significantly impacts the power system frequency stability for the following reasons: first, the replacement of conventional thermal generator by RE such ...as wind and solar degrades the frequency control capability; second, the variability of wind and solar imposes more challenges on the frequency stability. The current unit commitment (UC) program in the industrial practice cannot fully provide frequency reserve requirement to maintain the satisfactory frequency performance and the frequency reserves are not fully compensated through the existing market scheme. In this paper, a security constrained unit commitment (SCUC) model with primary and secondary frequency reserve is proposed to co-optimize the energy and frequency reserve to provide satisfactory frequency performance. Post-contingency transmission constraints are enforced to account for the deliverability of the frequency reserve. The locational based reserve pricing is proposed to differentiate the compensating prices for reserves procured at various locations. A five-bus system and a 118-bus system are used to test the proposed model. Frequency dynamic simulation is also implemented to illustrate the frequency performance improvement based on the proposed method in terms of various frequency metrics.
Voltage source converter-based multi-terminal HVDC (VSC-MTDC) system has been considered for interconnecting asynchronous power grids for improved system operation efficiency and reliability. In this ...study, a frequency response control strategy is proposed for the VSC-MTDC systems that can enable operating reserves sharing among the interconnected asynchronous grids. The proposed control strategy consists of three frequency control components: MTDC primary frequency control, corrective frequency control, and MTDC secondary frequency control. The MTDC primary frequency control could keep the frequency of a disturbed power grid stable and avoid the frequency dropping into an unacceptable level when a sudden power imbalance event occurs. The corrective frequency control strives to guarantee the settled frequency can be within the predefined secure frequency range. The MTDC secondary frequency control provides a novel optimal allocation strategy for considering the participation of MTDC system for restoring system frequency back to the nominal frequency with the lowest cost. The simulation results, based on a modified IEEE New England 39-bus system modelled in PSCAD/EMTDC, show the effectiveness of the proposed frequency response control strategies.
In this article, a photonic microwave signals generation scheme for background-free phase-coded (PC) radar pulse with multioctave tuning is experimentally demonstrated. Firstly, an optical frequency ...comb (OFC) demultiplexing technology based on optical injection locking (OIL) provides a power-equalized coherent optical local oscillator (LO) with ultra-broadband tuning capability. Then, a phase-modulated optical signal is produced based on the conversion intensity modulation to phase modulation. Finally, a background-free phase-coded signal can be obtained by beating the optical signal with LO at a balanced photodetector (BPD). The proposed scheme features a flat frequency response over an ultra-wideband frequency range without needing a broadband modulator and radio frequency (RF) synthesizer. A proof-of-concept experiment demonstrates that the power fluctuation of 0.5 Gbps background-free PC pulses is lower than 3.12 dB within 3∼24 GHz carrier frequency. Furthermore, the pulse compression performance and system stability are investigated, respectively.
The frequency responses of a power system following a generator outage are closely related to the commitment states of generators, which describe the droop and inertial characteristics and system ...pre-contingency power dispatch. This study presents a new model to estimate the transient and steady state frequency responses of two-area power systems at any moment following the loss of an online generator. In the proposed model, the deviations of tie-flow, area frequencies and rate of change of area frequencies as well as the extreme values of these functions and their associated time of occurrence following the outage of a generation unit are derived as modified analytical functions. A new approach is also proposed to linearise the modified extreme deviations based on pseudo-Boolean function theorem. In addition, a frequency-constrained unit commitment model with modified frequency-dependent constraints incorporating primary frequency regulation reserve is presented as a mixed-integer linear programming problem. The results indicate that the proposed method gives acceptable approximations for post-contingency responses and can ensure power system security from frequency viewpoint.
A fully integrated single-chip transceiver (TRX) with on-chip antennas for transmitting and receiving signals within a continues frequency range from 305 to 375 GHz is presented. The radio-frequency ...(RF) and local oscillator signals are generated using a wideband push-push voltage-controlled oscillator, a threestage power amplifier, and a frequency doubler. A heterodyne receiver using a fundamental mixer converts the received RF signal to an intermediate frequency (IF) signal, which drives an IF amplifier. Additionally, a divide-by-64 frequency divider is integrated to provide a low-frequency output for measurement purposes and to enable later the addition of a phase-locked loop for frequency stabilization and synthesis. A 130-nm silicon-germanium BiCMOS process with f t /f max = 250 GHz/370 GHz is used. The TRX chip is wire bonded to a printed circuit board and a TPX (Polymethylpentene) lens is placed on top of the chip for focusing the radiation. At a frequency of 343 GHz, the measurements show an effective isotropic radiated power of 18.4 dBm, a phase noise of -79 dBc/Hz@1 MHz, and an IF conversion gain of 28 dB. The obtained tuning bandwidth of 70 GHz is the highest reported so far for fully integrated TRXs.
This article introduces a novel, binary version of wind driven optimisation (WDO) called binary WDO (BWDO), which can be specifically used for solving binary valued problems such as antenna array and ...metasurface synthesis. Validation of proposed algorithm is done with standard benchmark functions. To demonstrate the efficiency of BWDO, examples of thinned antenna array and metasurface synthesis are considered. Thinned antenna array problem is solved by formulating single and multi-objective optimisation problems which achieve minimum SLL of −22.30 dB and −20.28 dB respectively, as compared to −13.2 dB by periodic array. Further, the proposed BWDO algorithm is interface with Ansys-HFSS and three design examples of metasurfaces such as MPA and AMC are further considered to exemplify the proficiency of BWDO. Simulation of optimised MPA exhibits five discrete bands of high absorptions at 8.7, 9.7, 14.6, 15.3 and 16.5 GHz with simulation reflection co-efficient value of −11.46, −10.00, −12.17, −16.19 and −20.58 dB which is less than −10 dB reflection under normal incidence of wave. Synthesised single and dual band AMC has in-phase reflection bandwidth of 0.58 and 0.34, 0.16 GHz at central frequency of 5.21 and 5.07, 6.49 GHz respectively. The measured results almost matched with the respective simulated results with slight variation due to fabrication tolerance.
In this article, a new microwave frequency-locked-loop (FLL)-based sensor is proposed for complex permittivity measurement of liquid solutions. An interdigitated electrode split-ring resonator ...(IDESRR) is embedded in the FLL and used as a sensing device to distribute electric field in the near-field region and sense the permittivities of the liquid solutions with different concentrations. When the test liquid is placed on the IDESRR, a deviation will be introduced to the resonance frequency based on the perturbation theory. This frequency deviation accompanies a corresponding phase shift in the FLL operating frequency. The phase-shifted signal then leads the FLL to output a frequency-modulated (FM) signal, whose frequency deviation depends on the concentration level of the test liquid. The quadrature frequency discriminator is used to demodulate this FM signal and transfer it into dc voltages, <inline-formula> <tex-math notation="LaTeX">V_{I} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">V_{Q} </tex-math></inline-formula>. Reference liquids with known permittivities are used to calibrate the proposed sensor and relate the measured voltages to the dielectric constant and loss tangent. In this article, the water-ethanol mixtures and water-glucose solutions are used as the test liquids to evaluate the measurement performance of the proposed FLL-based permittivity sensor. The measured results obtained using the proposed sensor agree very well with those obtained using the commercial dielectric probe. Moreover, since the proposed permittivity sensor has the benefits of a simple system architecture, high sensitivity, and not requiring a vector network analyzer (VNA), it has great potential to be developed as a new type of biomedical sample sensor.
This article proposed a microwave (MW) detection method by utilizing the effect of the dual MW on nitrogen-vacancy (NV) centers in diamond. We established a theoretical model of dual MW superposition ...and experimentally discovered the unusual peak in the optically detected magnetic resonance (ODMR) spectrum. The peak frequency and the full-width at half-maximum of the unusual peak, as well as fluorescence intensity in the nonresonant frequency range of the ODMR spectrum, were systematically analyzed to obtain the frequency and amplitude of the measured MW signals. The broadband MW detection was realized in a wide range of 2240-4512 MHz by utilizing the linear relation between the magnetic field and the resonant frequency in the Zeeman splitting. The experiments showed that the minimum detection power was up to <inline-formula> <tex-math notation="LaTeX">1~\mu \text{W} </tex-math></inline-formula>. The proposed approach can greatly improve the practicability of detecting MW fields on chip surfaces by quantum engineering techniques.
This study presents a metamaterial-based antenna using the concept of composite right–left-handed transmission-lines. The radiation-cells layouts are based on L/F-shaped slits, so these slits are ...engraved on the radiation-patches for establishing a series-capacitor effect. Moreover, the radiation cells including the spirals and via-holes for the shunt-inductors implementation. By cascading the proper number of cells, the desired antennas for very/ultra-high frequency-bands are designed. The first-antenna with four L-shaped cells isconstructed on the Rogers_RO4003 substrate with thickness of 0.8 mm, so that each of cells occupies the size of 2.3 mm × 4.9 mm. This antenna covers the experimental-bandwidth of 0.2–1.8 GHz, which corresponds to 160% feasible-bandwidth. This antenna resonates at frequencies of 600–850–1200–1550 MHz, so highest gain and efficiency, happened at 1550 MHz, are 3.4 dBi and 88%. For improving the antenna performances, the second-antenna is modelled with one-cell more than first-antenna and with changing in the slit configuration to F-shape and increasing in the same substrate thickness to 1.6 mm. F-shaped antenna has size of 14.5 mm × 4.4 mm × 1.6 mm, covering a measured-bandwidth of 0.11–2.1 GHz with five resonance frequencies at 450–725–1150–1670–1900 MHz, which corresponds to 180.1% practical-bandwidth. Maximum of the measured gain and efficiency of antenna are 4.5 dBi and 95%, which occur at 1900 MHz.
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