диафрагмированные волноводные фильтры / da5070f5-8e51-4701-ad5e-0491a4d373e0

Abstract

In this Paper, directional coupler design in (0.5GHz3GHz) frequency band stripline with the purpose of improvement of signal isolation and diminution of return signal has been simulated. The proposed plan has a rectangular geometric form which, by use of CrossCoupling (CC) couple techniques, has been applied for making intersecting Step Impedance of Parallel Transmission Line (SIPTL) for the induction of magnetic coupling in signal coupling and Branch Line (BL) for the structure of the linear branch paths and linear impedance technique in the process of creation of substrate path and line impedance matching in couple design. A 0.6 mm thick Rogers.5880 sub-layer material with a thickness of 0.6 mm and permittivity coefficient of 2.2, with a structure consisting of guided intersecting parallel lines of the signal couple, has been designed. The dimensions of the coupler are 25 mm x 35 mm x 1.7 mm. the proposed design has been simulated in ADS software.

Keywords:

CC, Isolation, S11, (dB), SIPTL, BL

I.INTRODUCTION

In telecommunications circuits and microwave radars, passive coupler elements are used for signal coupling and frequency phase change in receiving and sensing circuits. Couplers have a significant role in narrow and wideband frequency signals proportional to transmission capacity in frequency phase degree, and, depending on signal type, coupler substrate in various models in the microstrip, stripline, and waveguide technologies have been designed in passive and active modes [1]. The lengths of strip lines between adjacent ports have diminished from λg/4 down to 5λg/4 in which λg is the guided wave in the central frequency, and the coupler structure with a directional technique based on stripline has advantages in the improvement of signal isolation [1][2]. On the basis of the stripline coupler principle, 90˚ couplers are designed with a length of λg/4 between the signal branches for the improvement of signal transmission function. Designing of coupler substrate geometry is used for decreasing the dimensions by

various methods and, for this purpose, the combined methods for directional technique and parallel intersecting combined techniques in the directional method are used for the improvement of signal values and decreasing its dimensions. The Dimensional technique is utilized, in the form of four ports in a signal coupler in parallel coupling technique of signal transmission line, or intersecting coupling technique of signal transmission line in different bandwidths [3][4]. In general, the phase-frequency changes coefficient changes in dB unit between 90 to 270 degrees. In this technique, four ports are used, of which port 1 is considered as the signal input, port 2, as the output (Signal Transmitter), port 3, as the signal coupler, and port 4, as the signal isolator [5]. The purpose of this technique in designing the couplers is signal power transmission with the least weakening compared to other techniques of designing couplers and full compatibility with microwave narrow and wide frequency bands and improvement of signal isolation coefficient in frequency phase degree change. In some techniques, this causes distortion in phase change and creates phase deviation. Considering intersecting and directional connection techniques, this problem has been solved [6].

In the research performed, designing coupler in microstrip technology is in Electro-Magnetic (EM) mode, which, by use of parallel coupler technique, signal transmission line, directional technique, and intersecting connection technique, has been designed in rectangular geometry, with dimensions of 25 mm x 35 mm x 1.7 mm, and in Rogers.5880 sub-layer material. The purpose of the proposed design is the improvement of signal isolation coefficient and frequency phase change in telecommunications radars, including the 4G protocol, which has been simulated in 0.5GHz-3GHz frequency bandwidth in ADS software.

II.COUPLER DESIGN

Measurement of scattering parameters values is determined according to IEEE standard rules. These values are considered as having determined quantities compared to (dB), and the values obtained are a result of simulation and construction. If the values of results are out of the range of determined values for each parameter, designing the coupler substrate will have problems, such

as high noise in signal exchange, non-compliance and isolation of signals in ports, increase of self, and capacitor values in coupler substrate [7]. In designing passive circuits, especially stripline couplers with multiple ports, their bandwidth is significant in magnetic coupling compared to the type of placement of the number of ports. Also, broad bandwidth and application of signal isolation and its coupling in the process of creation of standard bands in broad frequency amplitude are one of the most significant techniques for designing several bands in coupler design [8][9]. By rectangular designing for coupler geometry and determining the type of its placement in stripline substrate, one can discern signal isolation for each of the coupler ports and determine its bandwidth by creating geometric design models in the main coupler forms, by which bandwidth is discerned for each port and there will be no limitation. Now, considering the mentioned remarks, for improvement of signal isolation coefficient, S12, (dB) parameter value must be determined and return signal losses value compared to S11, (dB) is obtained; the values of both parameters, too, are improved proportionally to frequency bandwidth [8]. Considering the directional technique for rectangular geometry substrate in microstrip, stripline and waveguide technologies are utilized in designing coupler passive substrates, signal dividers, and signal trajectory separators from antennas; the 90˚ phase between the input and output of each port is the same, and the input impedance matching value in the signal division is determined for each port in coupler trajectory [10]. In the combined designing of this technique in couplers, the value of the signal is taken from the input port 1 and the output signal value is sent from port 2. Also, the coupled signal in Sigma function in the output port 3 and the isolated signal, as well, (in Delta function) in port 4 are determined in the isolation signal amplitude. Directional technique, intersecting connection technique, and line impedance are SIPTL. These techniques are for the creation of adjustability of each of the directional straight lines and creation of concordance between the lines and ports, and, also, creation of substrate balance for matching the tiny surface of coupler band, in which signal is transmitted from rectangular geometry as a branch from straight lines of each port. In the division of transmitted signal and the determination of coupler central frequency, 3dB value in-band frequency width should be determined proportionally to the signal power; this value is obtained proportional to the section substrate surface in signal transmission. If the substrate has signal losses, we will have a weakening of signal in the output and an increase of time delay of signal in the diminution of output power in each of the branches of the coupler. Also, in the functions of intersectional directional technique, calculation of impedance and admittance in equations 1 to 17 [11][12], in-coordination of impedance (Z) and admittance (Y) matrices has been determined proportionally to the substrate [13]. Also, in the output of each port, distortion is noted, which, in the signal division in the trajectories of couplers, is determined as a signal value proportional to noise [14]. Considering the

ICREDG icpconf.8-01080082, 23&24 February, 2022

directional technique in designing coupler substrate, the signal division is determined for each trajectory of coupler ports, and, in the curved substrate geometry, with branching parallel and straight lines, or in the form of a curve, we will have full signal power transmission with the determination of phase degree, which will be without any change in frequency phase deviation. The proposed coupler schematic, too, is shown in figure.1.

(A) : Schematic Model

(B) : Layout Model

(C) : Fabrication Model

Fig.1. Simulation, ((A). Schematic & (B). Layout) and

(C). Fabrication of the proposed coupler

III. The results of the Proposed Simulation Design

The purpose of this research is designing and simulation of the proposed coupler in 0.5GHz to 3GHz frequency band with 90˚ of phase frequency difference with

Rogers.8550 substrate material, with a thickness of 0.8 mm and permittivity constant of 2.2, in the form of stripline technology design in ADS software. The proposed coupler has four ports, and, for escalation of the frequency bandwidth in microwave radars protocol and diminution of dimensions, in designing intersecting

ICREDG icpconf.8-01080082, 23&24 February, 2022

substrates of couplers, stripline technology is utilized. The structure of the geometry of the proposed coupler is seen in figure.1, in which the coupler dimensions are 25 mm x 35 mm x 1.7 mm. The gap between these layers is 0.2 mm and the total thickness of the stripline is 1.9 mm. In determining the matching quantities of impedance and diminution of admittance coefficient in substrates, escalation of signal transmission quality in transmission line becomes a parallel couple, which is effective indifference (Isolated) and addition (Coupling) couples. Directional technique and SIPTL technique in the conjugate couple mode of electromagnetic waves in cruciform connection confluence by intersecting technique in stripline substrate technology cause improvement of adjustability quantity of each port in relation to another, and magnetic coupling value improves signal isolation quantity to about -3dB, which is seen in figure.2. This technique of Frequency Phase Difference (FPD) is significant, which has been determined for a phase difference of 90˚ in the proposed design, and its phase difference, too, compared to frequency bandwidth, is insignificant, as seen in figure.3. Also, the phase difference of the passing signal, compared to the determination of S31, (dB) and S21, (dB) parameters, has been demonstrated in figure.4. This quantity is a result of the division of the two mentioned parameters compared to the frequency bandwidth; the more the oscillatory changes are without stepwise and intersectional distortion, the more the phase quantity improves in the output port. SIPTL technique is utilized in the process of creation of diminution of impedance value in substrate dimensions and improvement of electromagnetic coupling. This technique, too, causes intersecting non-distortion and lack of weakening of converging currents in the confluence connection in intersectional coupler trajectory; and, reciprocally, the exchange signal quantity improves. Considering figure 5, the proposed schematic couple in the simulation of converging currents has been demonstrated in signal exchange on the substrate. Also, for decreasing the output to input signal losses value of each port and improving signal reflection coefficient between the ports, use has been made of integration of branch line substrate and directional technique in designing substrate, which causes improvement of return signal losses quantity, shown in figure 6. Table.1 shows the proposed coupler design technical structure. Table.2 contains the results of the simulation, therefore in the table.3, the comparison of modern research with the previous ones is expressed.

These techniques cause a diminution of the dimensions of the proposed design, and the thickness of stripline substrate in the sub-layer material decreases, which, reciprocally, causes diminution of substrate admittance and impedance quantities.

Table.1. Technical characteristics of the proposed design

Table.2. Simulation results in the proposed design

Scattering Parameter

Table.3. A comparison between previous research and the current research

Fig.2. The Isolation Parameter

Fig.3. FPD Parameter of the chart

ICREDG icpconf.8-01080082, 23&24 February, 2022

Fig.4. Phase Difference S31, (dB) and S21, (dB) parameters

Fig.5. TEM convergence radiation in the substrate surface

Fig.6. Signal Return Loess Parameter of the chart

IV. CONCLUSION

In the investigation conducted, designing couplers is for the purpose of decreasing signal return losses and improving of signal isolation coefficient. This structure has two geometric parts (intersecting connections and straight lines). In the technical design of this substrate, intersecting directional technique has been utilized for the cruciform connection part in coupler geometry, and the SIPTL technique has been used for the improvement of substrate impedance coefficient and escalation of signal coupling in parallel lines. Also, an intersecting connection technique for the creation of cruciform couple in the exchange of substrate trajectories is designed in relation to ports, which is significant in the determination of signal phase degree and improvement of isolation coefficient. In designing the proposed coupler geometry, the mentioned techniques have been utilized, which have been designed in the 0.5GHz-3GHz frequency bandwidth. Transmission power in the proposed 3dB design has been taken into account, which has a wide range of applications in short-range power and medium-range radars, plus telecommunications radars. One of the advantages of the proposed design compared to the previous research is that, in the design concerned, several techniques have been integrated for improvement of scattering parameters coefficients and diminution of geometric dimensions.

ACKNOWLEDGEMENT

The authors would like to acknowledge Pajooheshgaran Sanat Electronic Ariaye, (PSEA.co) for supporting this research. This work has been supported by PSEA.co Research group. The field of activity of the company in modern research is the design and construction of electronic circuits. The company’s field of activity is Research Modern in RF/Microwave Circuits, Design and Fabrication of Electronic circuits, wherein located in the province of Kermanshah, Iran.

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