Mang He

A Frequency Selective Surface radome using a coupled resonator filter

In this paper, a Frequency Selective Surface (FSS) radome with a horn system was analyzed. A new coupled resonator spatial filter (CRSF) consisting of hexagon patch and circular aperture was firstly used in W-band. The FSS element shows stable performance with the polarization state and angle of incident wave. The horn composed of the FSS radome placed in its near-field region was designed. The antenna patterns shows that the FSS radome keeps good insertion loss, radiation patterns of horn within the designed pass-band, and reflects signal within the stop-band. The design of FSS radome shows performance advantage in reducing RCS at stop-band for its planar shape. The results provide the basis for our later studies of conformal shape radome.

Analysis of cassegrain antenna by using a dichroic sub-reflector

This paper presents a Cassegrain reflector system consisted of a curved frequency selective surface (CFSS) for a sub-reflector. The CFSS, a conformal hyperboloid with circular ring elements, reflects W-band and transmits infrared region. We designed three CFSS models using different methods. The results not only showed that antenna patterns for the system of CFSS coincided very well with the system of PEC sub-reflector but also the circular ring element was insensitivity to the grid structure in W-band.

A dual-band U-slot microstrip antenna with dual-feed and double-layer

A dual-band circularly-polarized double-layer U-slot microstrip patch antenna is proposed. The antenna is fed by a two-way Wilkinson power divider with different phase. The feed points are carefully chose to achieve a wide bandwidth. The antenna is printed on the substrate with high dielectric constant and simulated by HFSS and the simulation results are discussed. The impedance bandwidth (VSWR<;1.5) of the lower band and higher band is 24.2% between 1.08 GHz to 1.31 GHz, and 5.7% between 1.52 GHz to 1.61 GHz, respectively. The AR bandwidth (AR<;6 dB) is 45% between 1.07 GHz to 1.71 GHz. The simulated results are in good agreement with the requirement of GPS applications.

Hybrid PMM-MOM method for analyzing the RCS of finite array

In this paper, a hybrid method (hybrid PMM-MOM method) is presented for effectively and accurately analyzing the RCS of finite array. This method divides finite array into two parts. The inner part of an approximate infinite periodic structure is analyzed by periodic method of moment (PMM); the outer part is then analyzed by method of moments (MOM). The accuracy of new method is much better than that of the pure PMM, and is almost as same as that of pure MOM. As for the memory, because pure PMM uses the periodic conditions, it takes up much less memory resources. For hybrid PMM-MOM method, because the inner part is calculated by PMM, calculation work concentrated in outer part. Consequently, compared to the exact MOM, the new method saves much more memory resources and computation time.

Modeling and analysis of doubly-curved frequency selective surface

As a spatial filter, frequency selective surface (FSS) has been intensively investigated for many years. The applications of FSS are always needed to be conformal. So modeling and analysis conformal FSS (CFSS) is particularly important. In this paper, three projection methods for modeling the doubly-curved frequency selective surfaces (DCFSS) are investigated. We compare the different effects of these methods on the performance of FSS. Then, a hyperboloid, as a sub-reflector in 93GHz Cassegrain system, is designed as an example. We find that the projection methods all could be successfully applied in the design if the curved surface within electrically large size and small curvature.

A compact circularly polarized cavity-backed antenna with I-type crossed slots

A design of the compact cavity-backed antenna with I-type crossed-slot for circular polarization is presented. Parametric study is carried out to numerically investigate the effects of various dimensions of the antenna, including the length and width of the main arm of the crossed-slot, the size of the folded part at the end of the slot, and the finite ground plane, on the performance of the antenna. Numerical results show that good circular polarization can be achieved within the 4.8% impedance bandwidth as the size of the cavity is only 42mm (0.31λ0 at the central frequency).

Analysis and design of dual-feed circularly polarized U-slot microstrip antennas

The dual feed circularly polarized (CP) U-slot microstrip antenna (MSA) has recently been proposed to provide more than 20% bandwidth that VSWR ≤ 1.5 and AR ≤ 3 dB overlapped, even with very small size. However, the working principles of the antenna and the design rules for it have not been yet presented. In this paper, simple formulations to estimate the resonant frequencies of the dual feed antenna are derived, and an iterative design procedure to determine the initial geometric sizes of the antenna is also given. Compared to the final dimensions of the antenna obtained by numerical simulations, the accuracy of the proposed approximate computer-aided-design (CAD) formulas is within 5.3%.

Characterization of multilayer graphene surface impedance at W-band

The characterization of multilayer graphene surface impedance at W-band frequency is addressed for the basic application at W-band. On the Cu foil substrate, small area and continuous graphene films are prepared by chemical vapor deposition method using methane as the catalyst. We have got the once and twice transferred samples, corresponding to 6, 12 layers and they are successfully transferred to the polycarbonate substrates. Based on the reflection coefficient and transmission line model, the surface impedance of the graphene at W-band is extracted. The results show that, the approach has been successfully applied to characterize graphene samples at W-band. The extracted surface impedances provide a wideband frequency independent resistance less than 0.5 KΩ level and a weak capacitive behavior which fit with the Drude conductivity model. The approach is successfully applied to characterize multilayer graphene surface impedance. The resistance decreases and the conductivity increased with the more layers graphene.

Simulation of the electric field Shielding Effectiveness in the range of 10kHz–1GHz

Experimental tests for SE (Shielding Effectiveness) of cylindrical copper shield and braided-wire shield in the range of 10kHz-1GHz have been taken. To reproduce the phenomenon of the tests, we create the simulate model. A new model of braided-wire shield is presented in this paper. SE of cylindrical surface shield and braided-wire shield are compared. The influence on SE of badly grounded cylindrical surface shield is also studied. Meanwhile, Comparison of SE of the braided-wire shield in different fraction of coverage is made. The results are well matched experimental test. The SE is bad as the frequency is relatively low. Shielding function is disabled if the shield is not well grounded. To go a step further, holes on the braided-wire shield are rotated along the radial direction of signal line, and SE are compared correspondingly. The results show that it influences the SE in 10kHz-100kHz region.

The parametric analysis of H-shaped patch antenna

The parametric analysis of H-shaped patch antenna is proposed. Double L-probe feed structure, introducing capacitive effect on the horizontal monopole, allows for compensation to the feed inductance due to long-probe. Using double feed technology achieves the symmetry of the radiation pattern. In this paper, the antenna performances with different parameters have been proposed. Compared to a conventional H-shaped patch antenna, the proposed configuration shows as much as 60% increment in beam width in y-z plane and 20.75% impedance bandwidth.