Microstrip Hybrid Coupler with a Wide Stop-Band Using Symmetric Structure for Wireless Applications

Abstract

In this paper, a wide stop-band microstrip coupler is presented. The proposed structure consists of coupled lines and step impedance cells, which are integrated to operate at 2.82 GHz for wireless applications. This coupler is formed by a symmetric structure so that the locations of the output ports relative to input are quite similar. Accordingly, the magnitudes (also phases) of S 21 and S 31 overlap each other so that input signal can be selected through the output ports equally. There are little differences between the magnitudes and phases of S 21 and S 31 so that 0.97˚ phase shift is obtained. In comparison with previous works, the performance of the introduced coupler is improved. To get a better isolation, return loss and harmonic attenuation the frequency response is optimized without significant increase in circuit size. Moreover, the first, second and third harmonics of S 21 and S 31 are well attenuated as well as a wide stop-band is obtained up to 15.1 GHz. The realized coupler is fabricated and measured. There is a good agreement between simulated and measured results, which confirms the design process.

A Review on the Structure, Application and Performance of the Passive Microstrip Devices

“…The designed structure in [39] is a 90º coupler. The novel structure is the advantage of the reported couplers in [39] and [42] . We can see that any signal cannot pass from port 4.…”

“…M odern wireless communication systems widely need to microstrip passive devices such as filters, [1][2][3][4][5][6] diplexers, [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] multiplexers (triplexers [23][24][25][26][27][28][29][30] and quadruplexers, [31][32][33][34][35][36][37] five-channel multiplexer [38] ), and couplers. [39][40][41][42][43][44][45][46][47][48][49] For all of these passive devices, it is very necessary to have small dimensions, low insertion loss (IL), low return loss (RL), suppressed undesired harmonics, sharp roll-off at the edge of passbands (high frequency selectivity), etc. The number of re...…”

“…Microstrip couplers have four ports, which they should create two passing channels and an isolation channel. [39][40][41][42][43][44][45][46][47][48][49] In addition to losses and selectivity, the phase shift is an important factor. In 90° couplers, the phase difference between the two passing channels should be close ± 90° [39][40][41].…”

“…In zero-degree couplers, the phase difference between the two passing channels should be close to zero. [42] In this work, we will study the structure advantages and disadvantages of these passive microstrip devices. Since filter design is the basis of other designs, several filters will be studied first.…”

Microstrip hybrid wideband 10 dB coupler

“…A standard coupler (Figure 1) has four ports and they are usually defined as follows: [11] The microstrip technology utilizes 3 layers, a solid dielectric below, a metallization layer and air abovemaking it an inhomogeneous system [12]. Microstrip devices are the most usable ones because of their low cost, planar structure and their easiness of integration [13]. Hybrid couplers are very popular in literature [14].…”