Design of the LTCC Balanced Bandpass Filter with 2.45GHz Center Frequency
|School||Zhejiang University of Technology|
|Course||Communication and Information System|
|Keywords||Balun LTCC Stepped impedance resonators Transversal filter Balanced bandpass filter|
In the radio communication, especially in the front end of the RF circuit, the balanced filter is very important device. With the rapid development of wireless communication, the increasing miniaturization of microwave devices. Balancing filter based on low-temperature co-fired ceramic (LTCC) technology to meet the miniaturization and cost requirements. This paper studies the center frequency for Bluetooth and wireless LAN for the the 2.45GHz the LTCC balance of the band-pass filter design and simulation. This project is a cooperation with the Shenzhen sunlord Limited, through field-circuit method assisted with the electromagnetic field simulation software to design a balanced filter based on LTCC process. Paper mainly contains the contents of the three parts of the filter design, the design of the balun and the interconnection of the balanced filter, the specific contents are as follows: 1. Filter design. Mainly includes two filter design, one is implemented in the form of the coupling of the strip line microstrip filter, one is a microstrip filter designed using the principles of the transversal filter. Two types of filters are starting from the lumped circuit size calculated according to the relationship between the lumped circuit stripline stripline, then the initial model simulation with the electromagnetic field simulation software (HFSS), adjusted by the Centre frequency at 2.45GHz, a bandwidth of 100MHz the LTCC bandpass filter. Is different, the lumped circuit designing a first filter is obtained in parallel from normalized cut starting Chebyshev low pass filter, by the frequency and the impedance converting circuit changes to obtain a band-pass filter, and then through the J converter transform lumped circuit form of the resonant cell structure, and finally get the the two SIR the folding wire bandpass filter. Lumped circuit of the second band-pass filter is obtained by the low-pass filter and high pass filter in series, and then combined with the classic distributed parameter transmission line theory, instead of a lumped circuit of each of an inductor with a strip line, the capacitance . 2 balun design. First, the use of the odd mode analysis method to draw parity mode impedance of the coupled lines, the specific parameters of the coupled line Transmission line software reuse. The spiral linear structure due to the size constraints of the device, to achieve three line balun, and finally obtained in the pass band of the amplitude of the balanced terminals differ by less than 2dB, the opposite phase balun. Filter modeling 3.LTCC balance. In RF circuits, when the through hole is used as an interconnect element between the filter and balun will be interested in the characteristics of the filter and balun impact, so it is necessary to adjust the model after interconnection. This article using HFSS simulation software, and finally get a center frequency of 2.45GHz, bandwidth of 100MHz, the external dimensions of 2.5 × 2.0 × 0.9mm ~ 3, and the resistance with a transmission zero balancing filter.