Since the microstrip patch antenna has the advantages of small volume, light weight, low profile, easy processing, conformation, etc., there is a wide range of application prospects in military and civilian. It is well known that the substrate of the integrated circuit is some high dielectric constant materials, while the microstrip patterns can achieve optimal performance on the low dielectric constant basal. The patch antenna located in the high dielectric constant substrate is very low due to the loss of the surface wave, and the frequency bandwidth is narrow, and this situation is more prominent when the frequency of the application is high, resulting in a decrease in gain and efficiency of the patch antenna, and There is also a high cross-polarization level and mutual coupling in the array. In order to achieve integration of microstrip table antennas, it is necessary to avoid expensive substrate mixing techniques, high efficiency patch antennas must be achieved on high dielectric constant substrates. New photonic crystal patch antennas that have occurred in recent years can better improve the performance of a patch antenna with a high dielectric constant medium. Photonic crystal patch antenna refers to a patch antenna based on photonic crystals. The photonic crystal, or a PBG material refers to a manual electromagnetic crystal produced by a medium-based placing of a medium of a high dielectric constant. The surface wave syndrome of the electromagnetic crystal has a frequency ban in a certain frequency range. Band, referred to as a ban. By introducing photonic crystal structures in the patch antenna, the surface wave along the substrate is used to increase the electromagnetic waves radiated to the space along the surface wave of the substrate to the space, thereby improving the performance of the antenna. The high impedance surface type PBG structure adopted herein has the advantages of compact structure, good band gap performance, and can be integrated, and extensive applications in the design of the antenna.
1 PBG antenna design
The rectangular patch antenna designed herein is a rectangular microstrip antenna (radiation element) having a central frequency of 10 GHz (rectangular), and the feed mode is selected as the center side feed. The Roger 3010 material is used as a substrate, and the thickness H = 1.28 mm, the relative dielectric constant = 10.2. The size of the rectangular patch is L × W. The size of the patch unit can be calculated by the empirical formula:
The software LineCalc of the transfer line with the ADS comes with the ADS to calculate the width ω = 0.162 mm of the transmission line.
The design of the PBG material first uses the equivalent vehicle model to get the initial parameters, and more accurate parameters are obtained by full-wave numerical simulation. Since the cycle size of the high impedance surface PBG structure is much smaller than the working wavelength, its electromagnetic characteristics are described in parallel co-resonance circuits suitable for the set total circuit component (capacitor, inductor). Like a circuit filter, the current is prevented from being transmitted along the surface. As mentioned earlier, the capacitance effect of the mushroom-type high impedance surface adjacent patch (the medium substrate is both supported, and the effect of reinforcing the capacitance), the combined parameters of the metal via the equivalent inductive composition of the metallic parameters Circuit. Here is a high-resistance design formula:
Where: εr is the dielectric constant of the medium; T is the height of the highlast surface; G is a cycle pitch; ω is a unit side length; a is a cycle.
The final result result is that ω = 1.73 mm, g = 0.22 mm (as shown in Figure 2 (b)).
2 modeling and simulation
Modeling and simulating in HFSS based on the structure of the designed PBG antenna. The model map is shown in Figure 3.
The reflection coefficient map obtained by simulation is shown in Figures 4 and 5.
It can be seen that the bandwidth of the echo loss is about 600 MHz, and the reference antenna resonant frequency is 9.96 GHz, and the PBG microstrip antenna resonant frequency is 10.05 GHz. The resonant frequency of the PBG antenna is slightly higher than the reference antenna, because the coupling between the two is caused. The two have the same reflection coefficient of 9.99 GHz - 21.28 dB, and simulated on this frequency to obtain a direction map as shown in FIGS. 6 and 7. It can be seen that the PBG structure enhances the directionality, and the gain of the antenna will increase by 0.53 dB. The PBG patch antenna enhances the gain because the surface wave is suppressed to enhance the radiation amplitude of the main model.
3 knot
In this paper, the microstrip antenna of the high impedance PBG structure is designed and simulated, solving the microstrip patch antenna of the PBG structure and the radiation pattern of conventional microstrip patches. The simulation results show that the introduction of the PBG material can effectively suppress the propagation of the surface wave, improve the gain of the antenna, and optimize the direction of the antenna. It is proved that the photon band gap structure is indeed suppressed surface waves and improves radiation gain. The conclusions have a certain significance for the calculation and engineering design of the microstrip antenna. Read more
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