A high‐performance microstrip bandpass filtering coupler with low‐loss and compact size

Abstract

In this letter, novel spiral‐coupled transmission lines are used to obtain a high‐performance microstrip coupler. The advantages of the proposed microstrip coupler are novel structure, filtering frequency response, suppressed harmonics up to second harmonics, transmission poles, low losses, compact size, and good phase balance. The proposed structure is novel and different from the previous coupler designs such as rate‐races, rings, and branch‐lines types. It is presented for the first time in this work with a very small size and good performance. The size of this coupler is only 82.6 mm2 (0.004 λg2). The common port return loss is 33 dB and the insertion losses at port 2 and port 3 are 2.2 and 2.7 dB, respectively. To prove the accuracy of the design method and simulation results, the proposed coupler is fabricated and measured where the measurement results confirm the simulation results and the proposed design method.

Design and Optimization of a Compact Microstrip Filtering Coupler With Low Losses and Improved Group Delay for High-Performance RF Communication Systems

“…As shown in this Table, the proposed coupler is compact with the balanced phase, balanced magnitude and high isolation. Only the introduced coupler in [13] and [20] are smaller than ours. However, [13] has not a filtering frequency response which is a major problem.…”

“…However, [13] has not a filtering frequency response which is a major problem. Meanwhile, our coupling factor, magnitude balance and isolation are better than [13] and [20].…”

“…Also, at 1.92 GHz, the phases of S 21 and S 31 are -148.278º and -58.307º respectively. To prove the advantages of our coupler, we compared it with previously reported works ( [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]) in Table 1. As shown in this Table, the proposed coupler is compact with the balanced phase, balanced magnitude and high isolation.…”

“…A microstrip coupler is a passive component used to split or combine microwave signals in wireless communication systems. Microstrip couplers have many applications in power splitting, frequency sensing, and impedance matching [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. They are commonly used in microwave components, radar systems, and in satellite and cellular communications networks.…”

“…However, a new type of internal shunt stub is used in [13], which leads to a lowpass filtering coupler. In [20][21], the problem of large size is solved. However, both of them has imbalanced magnitudes.…”