Recent studies have shown that interplanetary missions may be made possible using inflatable solar sails that employ solar-flux power, providing thrust for spacecraft while reducing onboard fuel requirements. These sails require a large surface area (i.e., 100 m in diameter) to capture enough solar flux for spacecraft navigation. In this paper, a novel communication antenna concept is proposed for future solar-sail missions, taking advantage of the large sail surface area via application of Fresnel-zone (FZ) antennas. This study focuses on utilizing a design/analysis methodology using physical optics (PO) and method of moments (MoM) for Fresnel-type antennas applicable to the solar-sail missions. Extensive parametric studies of Fresnel-zone antenna radiation characteristics have been performed, and the analytical methodologies were verified using a series of measurements. Fresnel-zone antenna gain is studied under different antenna configurations. Furthermore, a Fresnel-zone antenna under surface deformation is investigated to characterize Fresnel-zone antenna performance in the reflective mode. In addition, a new bandwidth-enhancement technique is introduced for Fresnel-zone antennas, to accommodate the dual-band operation ( X band uplink and downlink) of the antenna for the deep space network (DSN).

A novel antenna concept for future solar sails: application of Fresnel antennas

Nearly all interplanetary missions have solely been dependent on some kind of chemical propellant for spacecraft navigation. Recent studies have shown that interplanetary missions may be made possible using a deployable solar sails, which employ solar flux power providing thrust for spacecraft while reducing on board fuel requirements. These sails require a large surface area (i.e. 100 m diameter) to capture enough solar flux for spacecraft navigation. An interesting question could be asked if one would be able to use the sails for creating an effective means for communications. In this paper, a novel communication antenna concept is proposed for future solar sails missions by taking advantage of the large surface area of the solar sail via application of zone plate Fresnel antennas. This study focuses on utilizing a design/analysis methodology for the Fresnel antennas which may be applicable to solar sail missions.

A novel antenna concept for future solar sails missions

The hybrid metal–organic framework [(CH3)2NH2]Fe(HCOO)3 with a perovskite-like structure exhibits a variety of unusual magnetic behaviors at low temperatures. While the long-distance super-exchange through the Fe-O–CH-O–Fe exchange path leads to a canted antiferromagnetic ordering at TN ~ 19 K, a second transition of magnetic blocking develops at TB ~ 9 K. The stair-shaped magnetization hysteresis loops below TB resemble the behaviors of resonant quantum tunneling of magnetization in single-molecular quantum magnets. Moreover, the magnetic relaxation also exhibits several features of resonant quantum relaxation, such as the exponential law with a single characteristic relaxation time, and the nonmonotonic dependence of relaxation rate on the applied magnetic field with a much faster relaxation around the resonant fields. The origin of quantum tunneling behaviors in the [(CH3)2NH2]Fe(HCOO)3 metal–organic framework is discussed in terms of magnetic phase separation due to the modification of hydrogen bonding on the long-distance super-exchange interaction.

https://iopscience.iop.org/article/10.1088/1674-1056/25/1/017601/pdf

Long-distance super-exchange and quantum magnetic relaxation in a hybrid metal–organic framework*

We numerically investigate the magnetoelastic (ME) instability in spin 1/2 antiferromagnetic rings with nearest-next neighbor (NNN) coupling J2 and Dzyaloshinskii—Moriya (DM) interaction Dz. It is found that, for a given Dz, there exists a critical Jc2. As J2 = Jc2, the ME instability is irrelative to the DM interaction and NNN coupling. These results may come from the competition between the DM interaction and NNN coupling. The DM interaction does not affect the critical behavior at the point of J2 = 0.5, at which the systems always locate in the dimerized state.

Dzyaloshinskii–Moriya Interaction in Spin 1/2 Antiferromagnetic Rings with Nearest Next Neighbor Coupling

We use non-equilibrium Green's function method to analyze the shot noise spectrum of artificial single molecular magnets (ASMM) model in the strong spin–orbit coupling limit in sequential tunneling regime, mainly focusing on the effects of local large spin. In the linear response regime, the shot noise shows 2S + 1 peaks and is strongly spin-dependent. In the nonlinear response regime, one can observe 2S + 1 steps in shot noise and Fano factor. In these steps one can see the significant enhancement effect due to the spin-dependent multi-channel process of local large spin, which reduces electron correlations.

Multi-step shot noise spectrum induced by a local large spin

The phase Fresnel zone plate, whose diffraction efficiency is up 97%, has been made. Because of the advantages of thinner thickness, lighter weight and design flexibility, the phase Fresnel zone plate has been considered for use as a MM-wave antenna so as to increase the diffraction efficiency. However, zone plates with only four phase steps are generally made up to now, so the diffraction efficiency is only about 80%, and the highest gain is no more than 35 dB. To overcome this weakness, a new kind of Fresnel zone plate antenna with a continuous phase structure is designed, and the authors call it a diffraction antenna.

Design of MM-wave Fresnel zone plate reflector antenna with continuous phase structure

The quantum tunnelling of magnetization (QTM) in single crystals of the single molecule magnet (Mn1-xCrx)12-Ac (x=0, 0.03, 0.04, 0.05) has been investigated. In comparison with its parent Mn12-Ac, a greater rate of magnetization relaxation and a lower effective potential-energy barrier have been observed in Cr-doping samples. This modulation of QTM due to the Cr-doping could be attributed to the small change of Sz due to the smaller spin of Cr itself and additional intrinsic but distributed transverse and longitudinal anisotropy raised by a subtle change of the local environment in the magnetic Mn12 core.

Resonant tunnelling of the magnetization in molecular crystal of [(Mn1-xCrx)12O12 (CH3COO)16(H2O)4] ·2CH3COOH·4H2O (x=0,0.03,0.04,0.05)

This paper investigates the single-molecule magnets of pure and Cr/Fe-doped Mn12-Ac. The components of the mixed crystals are identified by AC susceptibility technique. The ground-state spin and anisotropy parameters of doped Mn12-Ac are obtained: (i) Mn11Cr-Ac (S = 19/2, D = 0.62K, B = 0.0009 K, Δ = 63K), and (ii) Mn11Fe-Ac (S = 21/2, D = 0.39K, B = 0.001 K, Δ = 55K). The single-ion origin of the magnetic anisotropy is discussed.

https://iopscience.iop.org/article/10.1088/1674-1056/17/11/059/pdf

The effect of doped ions on single-molecule magnets of the Mn-12-Ac family

Long term stability is the main factor that influences the minimum detectable signal of microwave radiometers. Two new types of microwave radiometer were studied: a computer gain compensative microwave radiometer and a real-time calibrated microwave radiometer. The long term stability of both designs was optimal because they were insensitive to system gain fluctuations. The continuous calibrated microwave radiometer was also insensitive to system noise fluctuations. The minimum detectable signals were 0.13 and 0.19K respectively under an integration time of 0.6s.

Two new types of microwave radiometer: A computer gain compensative design and a real-time calibrated design

Based on scalar diffraction optics theory, a new type of mm-wave antenna(diffraction antenna) phase-correcting Fresnel zone plate with continuous structure is described in this paper. It has the advantages of thinner thickness, lighter weight and design flexibility. The design theory and space shadow are discussed in details, and the measured results are presented. The results show that the properties of this kind of antenna is closed to paraboloid reflector.

Zhang Junrong

Papers

Design of MM-wave Fresnel zone plate reflector antenna with continuous phase structure

Resonant tunnelling of the magnetization in molecular crystal of [(Mn1-xCrx)12O12 (CH3COO)16(H2O)4] ·2CH3COOH·4H2O (x=0,0.03,0.04,0.05)

The effect of doped ions on single-molecule magnets of the Mn-12-Ac family

Two new types of microwave radiometer: A computer gain compensative design and a real-time calibrated design

DESIGN OF mm-WAVE PHASE-CORRECTING FRESNEL ZONE PLATE REFLECTOR ANTENNA WITH CONTINUOUS STRUCTURE