Research On Micro - Barron Filter

With the rapid development of modern wireless networks and communication technology, a variety of network equipment and electronic products can access the network via wireless communication. All these could be achieved must rely on the vital RF front-end modules and microwave components. Commonly used military wireless systems and equipment such as radar, satellite communications, satellite navigation, remote telemetry, remote control etc. and various civil electronic products such as smart phones, tablet PCs, wearable devices, smart appliances, instruments, medical equipment, automotive electronic devices etc. are constantly towarding the development direction of miniaturization, multifunction, and high performance. In order to achieve miniaturization of various wireless systems and electronic products, the RF front-end modules and microwave components which occupy a lage volume in circuits need to be miniaturized.Miniaturization of balun filter is studied in this paper. In traditional method of balun filter design, at first, balun and filter is designed separately, then a matching network is used to connect them together to form one component. In this paper, multilayer coupled shorted-striplines were used to form a resonator, the resonator is small in size, and can achieve balun and filter function simultaneously, which avoids the complex process to design balun and filter separately. In addition, it is easy to achieve multi-stage cascade, also can introduce couplings of non-neighboring resonators to produce transmission zeros for a shape sideband and high stopband suppression. So, comparing to traditional balun filters, balun filters with these resonetors can obtain better filtering performance. In this paper, Six LTCC (Low Temperature Co-fired Ceramic) balun filters were designed, all of them have small size, simple structure, good phase imbalance, good amplitude imbalance and good filtering properties. The integration and miniaturization method used in this paper could be used as a reference in other RF passive components integration design as well.The main properties of the six balun filters are shown as follows. The L-band first-order balun filter with a passband of 1.6GHz-1.9GHz utilized capacitance loads to achieve good filter characteristics, its total size is smaller than 1.lmm×2.1mm×1.1mm, the phase imbalance is less than ±2 degree. The S-band second-order balun filter with a pass band from 3.15GHz to 3.75GHz have a size smaller than 2.1mm×l.6mm×1.2mm, its phase imbalance is less than ±2 degree. The S-band third-order balun filter with a pass band from 3.9GHz to 4.3GHz have a size smaller than 2.1mm×2.3mm×1.2mm, its phase imbalance is less than ±3 degree. The C-band fourth-order balun filter with a pass band from 4.8GHz to 5.2GHz have a size smaller than 2.6mm×2.9mm×1.2mm, its phase imbalance is less than ±4 degree. The S-band fifth-order balun filter with a pass band from 2.1 GHz to 2.3 GHz have a size smaller than 2.1mm×3.8mm×1.2mm, its phase imbalance is less than ±3 degree. The S-band sixth-order balun filter with a pass band from 2.7GHz to 2.9GHz have a size smaller than 4.3mm×4.9mm× 1.6mm, its phase imbalance is less than ±4 degree. Comparing with lower order balun filters, thanks to the additional number of orders and transmission zeros produced by cross coupling, the fourth-order, fifth-order and sixth-order balun filters get steeper sidebands and higher stopband rejection. The simulation results of the all six balun filters are better than required specifications, they are miniaturized, high-performance and high-reliability.