Compact Microstrip Balanced-to-Balanced Diplexer Using Stub-Loaded Triple-Mode Resonators

Abstract

In this paper, a new microstrip balanced-to-balanced diplexer is presented and investigated. The proposed diplexer primarily consists of two balanced bandpass filter paths, and each balanced filter path can be designed independently based on two identical stub-loaded triple-mode resonators. It should be mentioned that no extra matching networks are required at the common balanced input port in the design. For demonstration, a prototype balanced-to-balanced diplexer operating at 2.30 and 2.83 GHz is designed, fabricated and measured with 3-dB fractional bandwidths of 13.0% and 13.4%. Both simulated and measured results are provided in satisfactory agreement.

Design of a high–performance lowpass–bandpass diplexer using a novel microstrip structure for GSM and WiMAX applications

“…In Table 4, f o1 and f o2 are the first and second resonance frequencies of bandpass-bandpass diplexers. In the comparison Table, references [15][16][17][18] are bandpass-bandpass diplexers, which have larger dimensions and higher losses in comparison with authors' work while the authors could attenuate the harmonics better than them. However, because of their more comfortable designs, the channels of bandpass-bandpass diplexers are closer than lowpass-bandpass diplexers.…”

“…A matching circuit consisting of two coupled transmission lines with different widths are utilised to integrate the resonators. Several types of bandpass-bandpass diplexers are reported in [13][14][15][16]. Due to the decrease in insertion losses at both channels, the proposed diplexer in [13] is a suitable structure for RF energy harvesting.…”

“…However, it could not attenuate the harmonics, while it occupies a large area. Similar to this diplexer, the other bandpass–bandpass diplexers in [14–16] could not solve the problem of large physical dimensions. In [14], the magnetically coupled microstrip open–loop resonators are integrated to obtain two balanced–to–balanced planar diplexers.…”

“…Hence, it cannot attenuate the third harmonic, while it has high insertion losses. In [16], a microstrip diplexer consisting of two similar balanced bandpass filter paths with high insertion and return losses at both channels is designed and fabricated. Another disadvantage of this work is its undesired harmonics.…”

Design of a novel microstrip four-channel diplexer for multi-channel telecommunication systems

“…On the other hand, the gap between the channels of this diplexer is large. In [21], a microstrip dual-band diplexer is designed based on two similar bandpass filters. It has large size and large insertion losses.…”