Design and realization of high directivity microstrip coupler

Abstract

A method to improve the directivity of the microstrip coupler is presented. The structure of the coupler is modified for variable coupling coefficient. Using this structure, the power coupled to the isolated port can be controlled which results in high directivity. Using this procedure, 15‐dB couplers are designed and fabricated at 0.9 GHz. A high directivity of 43 dB is measured. The validity of the design concept is verified by simulations and measurements. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1078–1081, 2015

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

“…Moreover, it has a large phase imbalance. The problem of phase imbalance can be observed in Chi, 1 Tian et al, 4 Barik et al 5 and Maheswari and Jayanthy 7 while there are large return losses in Chi 1 and Maheswari and Jayanthy 7 . Also, most of the mentioned couplers have high values of S 21 or S 31 .…”

“…[1][2][3][4] In Chi, 1 interdigital radial cells, in Rezaei et al 2 and Salehi and Noori 3 high-and low-impedance resonators and in Tian et al 4 meandrous transmission lines are used to achieve various types of microstrip couplers. Meanwhile, the introduced microstrip couplers in Chi, 1 Rezaei et al, 2 Salehi et al 3 and Barik et al, 5 Lai and Ma, 6 Maheswari and Jayanthy 7 have relatively large sizes. The proposed coupler in Tian et al 4 has a compact size with a good common port return loss.…”

Polyester‐based wearable bandpass microstrip filter

“…In wearable systems and devices, microstrip filters are essential components to select desired frequency bands or reject unwanted frequency bands. Different types of microstrip filter have been proposed in the literature 7–16 . Bindu and Mohanan 7 reported an ultra‐wideband (UWB) filter using stepped‐impedance resonators (SIRs) to control lower cut‐off frequency and interdigital linked lines with control of upper cut‐off frequency.…”

“…Singh et al 8 present use of three interdigital edges coupled microstrip lines, SIR open stub, and a RO4003C substrate to create a planar UWB bandpass filter from 3.1 to 10.6 GHz. Maheswari and Jayanthy 9 demonstrate a compact low‐pass filter consisting of hairpin resonator is designed using FR4 substrate for cut off frequency 2.45 GHz. Liu et al 10 present a single half‐wavelength resonator loaded with three sets of short‐circuit step impedance stubs (BPF) is used to create a UWB FR4 substrate‐based bandpass filter with a range of 2.5–10.5 GHz and a notched band about 5.1 GHz.…”

Weakly coupled directional coupler with simultaneous wide bandwidth and high directivity

“…These include equalization of even and odd mode effective permittivity by addition of dielectric overlay, pseudo suspended substrate couplers, and anisotropic substrate couplers . Reactive compensation techniques have also been developed including the addition of lumped or interdigital compensating capacitors between coupled lines, use of asymmetrical delay lines, modification of the coupler into symmetrical and asymmetrical sections, reactive feedback elements, and series and shunt inductor loading . Another method is to provide external matching to the intrinsic impedance of the coupler …”