Design and Analysis of Multi-Band Filtering Circuits

Table of Contents

1. Frontmatter

2. Chapter 1. Background of Multi-band Filtering Circuit

   Xiaojun Bi, Qiang Ma, Zilan Cao, Qinfen Xu

   Abstract

   Since the radio signal firstly crossed the Atlantic over 100 years ago, RF technology was born and became one of the fastest-growing branches in the electronic information industry. The brilliance of RF technology owes much to the contributions of many scientists and engineers. The filtering circuit, an important component of the RF transceiver, is applied for the spectrum division, noise suppression, and impedance matching. With the development of the communication technology, the conventional single-band filtering circuit is insufficient to meet the needs of multi-mode/multi-band systems due to its large size. Hence, the multi-band filtering circuit is introduced as a better solution, which can greatly reduce circuit size and cost.

3. Chapter 2. Analysis of Multi-Mode Resonator

   Xiaojun Bi, Qiang Ma, Zilan Cao, Qinfen Xu

   Abstract

   Before we introduce the multi-band filter design technologies, many readers will find it helpful if basic structures of the multi-mode resonator (MMR) in multi-band filters are presented. To this end, we analyze several typical multi-mode resonator structures in this chapter, including step-impedance resonator (SIR), ring resonator, multi-stub resonator.

4. Chapter 3. Multi-band Bandpass Filter with High Selectivity

   Xiaojun Bi, Qiang Ma, Zilan Cao, Qinfen Xu

   Abstract

   Multi-band bandpass filter (BPF) is a system that allows the passing of signals with frequency in multiple specific frequency bands, while attenuating those with frequency in the remaining frequency range. As an important component in the multi-band wireless communication systems, the multi-band BPF is required to have the characteristics of high selectivity, low insertion loss, small size, and controllable center frequency & bandwidth.

5. Chapter 4. Reflectionless Multi-band Bandpass Filter

   Xiaojun Bi, Qiang Ma, Zilan Cao, Qinfen Xu

   Abstract

   The rapid development of multi-standard microwave communication systems demands reflectionless multi-band filters as indispensable components to eliminate inter-stage reflected signals between active RF blocks, instead of adding isolators or attenuators. In this chapter, state-of-arts reflectionless filter design technologies are briefly introduced and analyzed at the first. Secondly, a novel reflectionless architecture with reused resonances is proposed to address the existing issues. Based on this proposed reused architecture, a triple-band reflectionless filter prototype and a tunable reflectionless dual-band passband filter prototype have been implemented. Measurement results indicate the obvious advantages of absorptive bandwidth, compact size, and frequency controllability of our proposed structures.

6. Chapter 5. Balanced Filter with High Suppression

   Xiaojun Bi, Qiang Ma, Zilan Cao, Qinfen Xu

   Abstract

   With the rapid development of radio frequency (RF) communication systems, more and more research has been done on balanced circuits for common-mode interference suppression, including environmental noise, electromagnetic interference, etc.

7. Chapter 6. Slotline Based Multi-band Balun Filter

   Xiaojun Bi, Qiang Ma, Zilan Cao, Qinfen Xu

   Abstract

   Benefited from the inherent wideband and differential characteristics, the slotline is suitable for the design of differential circuits. As pointed out in Chap. 5, utilizing the microstrip-to-slotline transition with π-type shorted slotline stub and SRSR structure, a balanced filter with high suppression is proposed, which lays the foundation for the design of multi-band balun filter in this chapter. The balun filter, as an essential passive RF component, converts the signal between the balanced port and the unbalanced ports in the desired frequency range.

8. Chapter 7. Switchable Filtering Diplexer Based on Reused L-shape Resonator

   Xiaojun Bi, Qiang Ma, Zilan Cao, Qinfen Xu

   Abstract

   In the multi-band communication system, besides the multi-band filtering circuits in the above chapters, the switchable filtering diplexer is also significant for the frequency division duplexing (FDD) systems and RF systems with multi-signal-paths.

9. Chapter 8. Miniaturized 55-/95-GHz On-Chip Dual-Band Bandpass Filter

   Xiaojun Bi, Qiang Ma, Zilan Cao, Qinfen Xu

   Abstract

   On-chip bandpass filter (BPF) as a key component of millimeter-wave communication systems, has obtained more and more attention. Recently, some on-chip BPFs have achieved remarkable performance.

10. Chapter 9. Summary and Conclusions

    Xiaojun Bi, Qiang Ma, Zilan Cao, Qinfen Xu

    Abstract

    Compared with the traditional system architecture, the multi-band communication system can be applied to different frequency bands simultaneously, which greatly reduces the circuit size and cost of communication systems. To sum up, this book has described the theory, analysis and design of the multi-band filtering circuits, which are bandpass filter (BPF), reflectionless filter, balun filter, switchable filtering diplexer and on-chip BPF.