Article

Dual-Band Out-of-Phase Power Divider With Impedance Transformation and Wide Frequency Ratio

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Abstract

A novel dual-band out-of-phase power divider (PD) with impedance transformation and wide frequency ratio is proposed in this letter. This proposed circuit consists of four double-sided parallel-strip lines (DSPSLs) to obtain the out-of-phase and dual-band performance, mid-inserted conductor plane as a common ground, and two resistors to improve the output port isolation. A through ground via (TGV) is employed to realize the high power application. By using rigorous even- and odd-mode analysis, a set of closed-form equations and design procedures are obtained and the analysis indicates that this PD can operate at two arbitrary frequencies with wide frequency ratio $(2.44leq k leq 7.31)$ . Furthermore, an experimental circuit is designed, and fabricated. The simulated and measured results agree very well to verify our design theory.

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... Out-of-phase power dividers (PD) [1], which can convert one signal into two-way out-of-phase output signals with equal power division, can be widely used in the balanced circuits and systems, such as pushpull power amplifiers, balanced mixers, and the feeding network of balanced antennas. According to the open literatures, the research about out-of-phase PD can be classified into single-band equal PD [1], single-band PD with arbitrary power division ratio [2], dual-band application [3][4][5], and single-band PD with complex impedance transformation [6,7]. ...
... The rat-race couplers based on the planar microstrip lines in [22,23] realize equal power division with filtering function; however, the out-of-phase performance is only limited near the operating frequency. The three-layer out-of-phase PDs [1][2][3][4][5][6][7] possess better out-of-phase performance than the rat-race couplers because the double-sided parallel-strip lines (DSPSLs) belong to the balanced transmission lines. ...
... The top, middle, and bottom layers are shown in Figure 2. It can be seen that the microstrip lines on the top and bottom layers are symmetrical, except the two output ports, indicating that the evenand odd-mode analytical method can be used in this paper [3][4][5][6][7]. There is a hole in the middle layer to ensure that the copper cylinder (CC 2 ) cannot be connected to the conductor. ...
... One example of this type is shown in Fig. 1(a), and alongside are its simulated and measured performances. Another way for dual-band feature is finding the port-matching and output-isolation condition directly, then establishing design equations [3]- [11], [14]- [18]. This method could obtain closed-form design equations for circuit-parameter values. ...
... The other method is to design wideband components, operating under a wide and continuous band that covers the supporting frequency standards. Correspondingly, there are quantities of power dividers working under dual- [3]- [18], multiple- [19], [20], and wide-frequency [21]- [29] bands. ...
... The second method is manipulating the electromagnetic fields by employing microstrip-to-slotline transitions to get inversed fields at two outputs, as literatures [22], [24] ( [22] is shown in Fig. 5(b)). The last mean is based on the DSPSL-to-microstrip transitions [10], [18]. The two symmetric microstrip branches of the outputs are connected to the "+" and "-" conductors of the DSPSL respectively, thus they output "+" and "-" signals with equal magnitude. ...
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In this paper, massive state-of-the-art planar power dividers are presented and discussed. The innovations of these superiorly-performanced power dividers lie in the performance breakthrough, physical configurations and function integrations. Eventually, based on the trend presented, the future of the power dividers is predicted. This paper might have inspiration significance to illuminate the way for the development of power dividers.
... Recently, researches on the balun have been extensively conducted. For example, baluns or in-phase power divider with differential feeds [1], with dual-band operation [2][3][4][5][6], and with impedance transformation [4][5][6][7] are reported. Specially, if the function of filters is integrated into a balun, the co-design of baluns and filters would dramatically improve the system integration and facilitate the design process. ...
... Recently, researches on the balun have been extensively conducted. For example, baluns or in-phase power divider with differential feeds [1], with dual-band operation [2][3][4][5][6], and with impedance transformation [4][5][6][7] are reported. Specially, if the function of filters is integrated into a balun, the co-design of baluns and filters would dramatically improve the system integration and facilitate the design process. ...
... Operating band Filtering function Terminal impedances Isolation Phase difference at outputs [8] Single p Different p In-Phase [9] Single p Identical p In-Phase [10] Single p Identical p In-Phase [11] Single p Identical p In-Phase [2] Dual N/A Identical N/A Out-of-Phase [3] Dual N/A Different N/A Out-of-Phase [5] Dual N/A Different p Out-of-Phase [7] Dual N/A Different p Out-of-Phase [12] Dual ...
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A new planar dual-band balun with filtering response and output isolations is proposed in this letter. The balun is constructed on a three-layer PCB, whose out-of-phase operation is realized by antisymmetric output configuration. By introducing dual-band resonators and admittance inverters, the circuit is able to operate with designated filtering response, and the source/ load impedances could be different. Additionally, the output isolation is reserved by employing two isolation resistors. The experimental results prove that this new balun is a good candidate for muti-standard and muti-functional communications.
... However, the circuits presented in Refs. [15][16][17][18][19] presented in Ref. [15] has some drawbacks including: (1) frequency-dependent isolation resistors, resulting in inaccurate design implementation at some frequency ratios; (2) utilizing narrow transmission lines up to 150 ohm; (3) limited frequency band ratios (1:62 < f 2 /f 1 < 3) using 10-150 ohm transmission lines; (4) limited bandwidth. Although the circuits in Refs. ...
... [16] and [17] have wide bandwidth, they still use narrow transmission lines and frequency-dependent resistor values, whereas the frequency band ratios are limited to a range of 1 to 1.7, restricting the overall bandwidth of the system [18], utilizes a planar circuit with additional optimization and modifications on transmission line widths to improve the bandwidth of the circuit but it still has a limited bandwidth along with a high amplitude imbalance. A dualband out-of-phase is reported in Ref. [19] with wide frequency ratio. This power divider however operates over a narrow bandwidth and needs extra surface area to accommodate impedance transformers at the input and output ports. ...
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Based on the double-sided parallel-strip lines with an inserted conductor as a virtual ground, a high power divider with dual-band/broadband response and frequency-independent 180° phase difference between the output ports is implemented in this paper. The circuit topology employs a single commercially available external isolation resistor as well as moderate line impedances (15-100 ohm), making it suitable for high-power applications. Precise closed-form design equations on the basis of even- and odd-mode analysis are derived. In addition to the wide range of frequency band ratios from 1 to 2.65, broadband response is also obtained by selecting the proper value of frequency band ratios. To substantiate the design equations and theory, a circuit with 2:1 frequency ratio and 84.5% bandwidth referring to 16 dB isolation and 12 dB return loss values is developed. To the authors' knowledge, this is the widest bandwidth reported for out-of-phase high power dividers.
... Over the past few years, much effort has been focused on the implementation of various out-of-phase PDs. To achieve the required out-of-phase characteristic between output ports, a variety of out-of-phase PDs have been presented based on microstrip-line structures, 1-5 microstrip-toslotline transition structures, [6][7][8][9] double-sided parallelstrip lines (DSPSLs), [10][11][12] and so forth. Recently, to satisfy the increasing demand for compact and low-cost system, the out-of-phase filtering power divider (OFPD) has become research hotspot, which can simultaneously provide out-of-phase power splitting function and frequency band selection function. ...
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... A TL exhibits complex conjugate input impedances at two arbitrary frequencies, i.e., θ and rθ, if its electrical length (θ) follows Eq. (1). This property is commonly utilized for dual-band performances [13][14][15]. ...
... Many of these designs report innovative techniques that can achieve high impedance transformation ratio (k) and high frequency ratio (r) so that they can find usefulness in the design of modern wireless communication system components. Furthermore, inherent impedance transformation is an important feature for the wireless system components as they discard the need for additional impedance transformers [25]- [33]. ...
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... Moreover, the designs [4]- [7] have reported the inherent impedance transformation (i.e., k), an extremely important feature in a balun, with dual-band operation of baluns. In this context, two dual-band baluns were reported in [4] and [5] but either r or k was limited to a narrow range. Another report [6] provided a design with detailed analysis on the range of r and k, but its capability was untested due to the absence of experimental demonstration. ...
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... It is apparent from Table II that the design reported in [5] is terminated with 50Ω port impedances and hence not possible to understand impedance transformation ability. Another design [6] reports good performance at high r but is limited with k. A very recent balun architecture [7] demonstrates concurrent performance for k = 3 and r = 2.13 but at the expense of layout complexity considering the possibility of longer Tjunction coupled line. ...
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... It is apparent from Table II that the design reported in [5] is terminated with 50Ω port impedances and hence not possible to understand impedance transformation ability. Another design [6] reports good performance at high r but is limited with k. A very recent balun architecture [7] demonstrates concurrent performance for k = 3 and r = 2.13 but at the expense of layout complexity considering the possibility of longer Tjunction coupled line. ...
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... By utilizing the double-side parallel-strip line and mid-inserted conductor plane, the frequency ratio of 2.44 to 7.31 can be achieved. 20 With the help of coupled-lines and open stubs, 21 the range of frequency ratio could be from 1 to 7. In Reference 22, a multiband power divider is proposed based on a multisection stepped-impedance transformer, where the dual-band case has a maximum frequency ratio of 7.75. Furthermore, a dual-band two-section Wilkinson power divider with arbitrary frequency ratios was proposed in Reference 16. ...
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... Additional four open stubs would add the function of dualband operations to the previous design [4]. In [5], a structure comprising double-sided parallel-strip lines and a midinserted conductor plane was implemented to carry out dualband performance for baluns. A technique to determine the frequency ratio of dual-band operations at millimeter-wave frequencies is revealed in [6]. ...
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... Since using conventional transmission lines to design PDs is short of innovation, improved transmission lines such as non-uniform transmission lines and composite right-and left-handed transmission lines play important roles in PDs [25], [26]. In addition, some out-of-phase PDs with high frequency ratios can be widely used in many applications [27], [28]. ...
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... Here, Y 1 , Y 2 , Y 3 are the admittances of Z 1 , Z 2 , Z 3 . Using (6) in (8), the conditions between Y 2 and Y 3 can be expressed as: ...
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One of the most useful transmission-line constructs is the quarter-wave transformer that is used to impedance match a line at a single frequency f<sub>0</sub>. The feasibility of an electrically small transformer with two sections and capable of achieving ideal impedance matching at two arbitrary frequencies is demonstrated analytically. To achieve this, the exact solution to the resulting transcendental transmission-line equations for two sections is obtained with no restrictions. The parameters of the transformer are presented in explicit closed form, and are exact. The results of this study are useful for a number of practical design problems, including dual-band antennas and RF circuits in general. In particular, feasibility of ideal operation at the important first harmonic frequency 2f<sub>0</sub> is demonstrated.
  • Microw
Microw. Theory Tech., vol. 60, no. 8, pp. 2403–2409, Aug. 2012.