Co-design Of Dual-band Planar Antenna And Dual-band Filter

In modern wireless communication systems, wireless communications terminal equipment has gradually evolved into personalized intelligent device, so the RF front-end needs to have the characteristics of multifunction and high performance. As the important components of RF front-end, filter and antenna have become the focus of research, and develop toward low loss, miniaturization, low cost, multiband. Generally, filter and antenna are designed independently, and then connected directly with each other through their ports with same impedance. However, direct connection often results in impedance mismatch, which worsen the performance of RF front-end, especially passband edge of the filter. Also the insertion loss of the circuit is increased. In order to avoid the problem of impedance mismatch, it is necessary to add additional matching network between the two components which will increase the size of circuit, and go against miniaturization. With the improvement integration of circuit, in order to realize miniaturization, we hope antenna and filter are integrated into one module. To this end, this paper presents a new method which designs miniaturized dual-band filter at first. In order to verify its validity, a dual-band filter has been designed for WLAN. Then, we propose a co-design method of dual-band antenna and filter. The main contents of this paper include the following several parts:1) The research status of the antenna and filter in the RF communication system is introduced, and the several key characterization parameters of the filter and antenna are introduced.2) For designing miniaturized dual-band filter, a new method is proposed. In order to verify the feasibility of the method, we design a dual-band filter based on step impedance resonator (SIR). The filter works at 2.4 GHz and 5.2 GHz. Its reflection coefficient is below-20 dB, insertion loss is less than ldB, and relative bandwidth is 20%. The size is 6mm × 15 mm (0.08 λg1 × 0.19 λg1, λg1 is the guide wavelength for the center frequency of the first passband).3) The co-design of the dual-band filter with the antenna is accomplished. According to the principle of impedance matching, we independently design the dual-band filter and antenna at the beginning, and then the proposed method is applied to accomplish the co-design. To verify the feasibility of this method, a co-design example of the dual-band filter based on (SIR) and monopole antenna working at 2.4 GHz and 5.2 GHz is illustrated. The final sample is simulated and measured, and its reflection coefficient is lower than-16 dB, relative bandwidth of two bands are 10% and 8%, and the size is 35 mm × 20 mm. (0.44 λg1 × 0.25 λg1, λg1 is the guide wavelength for the center frequency of the first passband).