Compact and Broadband-Balanced Amplifier for a Monolithic Microwave Integrated Circuit Using Lumped Elements Only

Han, Heeje; Kim, Hongjoon

doi:https://doi.org/10.1155/2023/5592459

International Journal of Antennas and Propagation

On this page

Abstract Introduction Conclusions Data Availability Conflicts of Interest Acknowledgments References Copyright Related Articles

Research Article | Open Access

Volume 2023 | Article ID 5592459 | https://doi.org/10.1155/2023/5592459

Compact and Broadband-Balanced Amplifier for a Monolithic Microwave Integrated Circuit Using Lumped Elements Only

Heeje Han¹and Hongjoon Kim²

Academic Editor: Trushit Upadhyaya

Received24 May 2023

Revised02 Aug 2023

Accepted05 Aug 2023

Published14 Aug 2023

Abstract

A flat phase difference across a broad bandwidth is achieved by appropriately combining the positive and negative phase propagation of right-handed (RH) and left-handed (LH) transmission lines (TLs), respectively. Employment of lumped elements provides easy realization of both TLs with the desired frequency passband, characteristic impedance, and phase propagation. The proposed quadrature power divider (QPD) was fabricated in a compact size by only using lumped elements instead of general TLs with a large area and a narrow bandwidth. The fabricated QPD maintains a flat phase difference of 90° ± 8.7° over a frequency range of 1.19–2.96 GHz while its circuit size is 0.036 . Owing to drastic size reduction of the QPD, the proposed balanced amplifier (BA) also could be realized with an extremely compact size of 0.044 and broad bandwidth unlike in other BAs reported in the literature and maintains a return loss of less than −10 dB at each port over the bandwidth of the QPD.

1. Introduction

Compactness and broadbandness are essential in modern radio-frequency and microwave components. However, conventional transmission line (TL)-type circuits for impedance matching, power splitting/combining, or feeding networks occupy a large area on the circuit board or have a narrow bandwidth [1–5]. To overcome such limitations, several compact and broadband microwave components have been introduced in [6–10], where compactness in size was achieved by replacing conventional TLs with lumped elements.

A left-handed (LH) TL, which is well known as one-dimensional metamaterials, has a negative phase constant, opposite to a right-handed (RH) TL. Recently, various applications of LH metamaterials have been demonstrated for microwave components. Some previous studies achieved an improvement of a wide bandwidth or size reduction using an advantageous property of composite right- and left-handed (CRLH) structures such as the phase propagation, resonance, and filtering. In [11–16], the authors suggested power dividers with in-phase or quadrature phase differences, and the authors in [9] introduced a balun with a 180° phase difference for a broadband frequency. Moreover, the authors in [17] realized a compact filtering antenna using a LH property.

A quadrature power divider (QPD) splits an input signal into two equal-magnitude outputs with a 90° phase difference. In [11, 12], conventional 90° hybrid couplers were substituted by a QPD, indicating that QPDs can be used in balanced amplifiers (BAs). The main purpose of BAs is to minimize the input and output reflections by incorporating two identical amplifiers with a 90° hybrid coupler at the input and output, respectively. As a result, both the couplers cancel the reflections at the input and output of the two amplifiers by combining them with a phase difference of 180° [18]. However, because of the narrow bandwidth of the hybrid coupler, the bandwidth of the general BA is narrow. Furthermore, because the hybrid coupler occupies a large area, the size of the whole BA circuit must be very large. In [11], the authors demonstrated a broadband BA using composite right- and left-handed (CRLH) TLs; however, it still occupies a large area and is not appropriate for a modern microwave system where a compact IC style module is required.

Our main idea in this study is a considerable size reduction and broadband impedance matching of BA by replacing 90° hybrid couplers with compact QPDs integrating RHTLs and LHTLs with lumped elements only. The QPDs in many articles consist of complicated patterns or TLs with a large area on their circuit boards although some studies employ lumped elements for the LH structures. As lumped elements can be easily implemented with a standard monolithic microwave integrated circuit (MMIC) process, the whole circuit can be further minimized. In this paper, we demonstrate our main idea by presenting the theories and experimental results of the fabricated BA. Particularly, for a low-frequency band, our work can contribute to an extreme size reduction.

2. Broadband and Constant Phase Difference between an RHTL and an LHTL

Because there are numerous studies discussing the structures and analysis of an RHTL and an LHTL, we will provide a brief overview of the theories used to explain the broadband 90° phase difference.

Figure 1(a) depicts an RHTL equivalent unit cell which is a low-pass filter structure comprising two series inductors and a shunt capacitor. Conversely, an LHTL unit cell (Figure 1(b)) works as a high-pass filter, which consists of two series capacitors and a shunt inductor. By cascading several identical unit cells of each TL, a periodic cutoff frequency (Bragg cutoff frequency) emerges, and each cutoff frequency can be computed using the following equations [9]:where the superscripts R and L denote the RHTL and LHTL, respectively.

(a)

(b)

For the passbands of both TLs, the characteristic impedances can be approximated using equations (2) and (3) , respectively [9].

Also, the phase constants of an RHTL and an LHTL are given by equations (4) and (5), respectively [9].

Unlike that of an RHTL, the phase constant of an LHTL is negative, indicating that the phase propagation is in the direction opposite to that of the Poynting vector. Figure 2 illustrates the theoretical phase propagation of each TL with one section and their phase difference based on equations (4) and (5) when L_R = 1 nH, C_R = 2.5 pF, L_L = 2 nH, and C_L = 5 pF. Therefore, the calculated cutoff frequencies of both the TLs, and , are 6.37 and 0.79 GHz, respectively. As shown in Figure 2, the bandwidth maintaining a phase difference of 90° ± 5° is broad from 1.26 to 4.02 GHz. These theoretical results are based on simple calculations using the constant values of the lumped elements without considering the tolerance and self-resonant frequency of each element and any parameters from a realization. By carefully selecting the appropriate element values of the RHTL and LHTL after considering their characteristic impedances, cutoff frequencies, and phase constants, the desired flat phase difference can be achieved for the broad bandwidth (Figure 2).

3. Realization and Measurement of the Compact and Broadband BA

Figure 3 illustrates the TL model of the proposed BA. Two QPDs are connected at the input and output ports. The QPD at the input port equally splits the input power with a 90° phase difference, while the QPD at the output port combines the two amplified signals in phases. Thus, the two QPDs effectively cancel the reflected signals at the input and output of the amplifier by combining them with a 180° phase difference. As explained in the previous section and shown in Figure 3, an RHTL and an LHTL are used after a Wilkinson power divider to have a broadband 90° phase difference for the QPD at the input. As the Wilkinson power divider and both the TLs in the QPD can be realized with lumped elements, the whole circuit can be made compact, facilitating drastic size reduction when the circuit is an IC type.

Figure 4 shows the compact and broadband BA fabricated on an RO4003 board whose thickness is 0.5 mm and relative permittivity is 2.3. Each QPD consists of a synthetic LHTL and RHTL to have a wideband 90° phase differentiation and a Wilkinson power divider with a synthetic RHTL. For the broadband amplifier, NLB-300 from RF Micro Devices, Inc., was used. Because the QPD employs only chip lumped elements (1608 size in mm), its occupied area on the circuit board is 0.07×0.11 , making the size of the whole fabricated BA very compact. To design the Wilkinson divider using lumped elements, a synthetic RHTL with a phase propagation of a quarter wavelength with a characteristic impedance of is required as shown in equations (2) and (4).

We implemented EM simulation using ANSYS HFSS. Each lumped element on the RH and LH TLs is assigned by the boundary condition, and input/output ports are connected to each TL through the microstrip lines. The simulation and measurement results of the proposed QPD are shown in Figure 5. The measurement results of the fabricated QPD show a good agreement with the simulation as can be seen in both results. From the measured results, we set the bandwidth at 1.77 GHz (between 1.19 and 2.96 GHz) so that the return losses at all the ports (, , and ) and the isolation between the output ports () are over 10 dB. For the same frequency range, the insertion losses of and vary from 3.33 to 4.14 dB and from 3.4 to 3.94 dB, respectively. Moreover, the absolute values of the magnitude imbalance () are less than 0.32 dB. In addition, the QPD maintains a phase difference of 90° ± 8.7° within the bandwidth. Table 1 shows the comparison of the proposed QPD and other quadrature power-dividing components in some literatures. The size of our QPD in Table 1 is the whole board size (0.24 × 0.15 ) including the microstrip lines at the input/output ports for measurement. The authors in [20, 22] have excellent characteristics with a very wide bandwidth (the relative bandwidth is over 100%), but each circuit size is much larger than our work.

(a)

(b)

To verify the return loss improvement, we compared the fabricated BA with a single amplifier without any impedance matching, as can be seen in Figure 6. The gain of the BA varies from 8.44 to 11.84 dB for the −10 dB bandwidth between 1.19 and 2.96 GHz. The small decrease in the gain of the BA compared to the single amplifier is mainly due to the insertion loss, magnitude imbalance, and phase error of the QPD fabricated with the lumped elements only. The proposed compact BA could noticeably enhance the indistinct return loss of a single amplifier. The measured noise figures of the single amplifier and the BA are shown in Figure 7. The noise figure of the compact BA is from 2.13 to 3.76 dB within the bandwidth which is slightly higher than the single amplifier. Nevertheless, the size of the whole BA circuit is 0.37 × 0.12 . This is possible by replacing all the general TLs required to construct the BA with lumped elements based on synthetic RHTLs and LHTLs. Table 2 shows a comparison of the fabricated BA and other previous works. It is appropriate to mention here that the written sizes of [11, 25] are deduced from the size of both used QPDs in each BA because the precise sizes are not provided in each paper. The BA in [11] suggests that its design method is very similar with our work using LH materials. However, the circuit size of [11] is significantly larger than ours although the relative bandwidth is 12.6% wider than ours.

(a)

(b)

4. Conclusions

Herein, we present a broadband BA that uses a compact and broadband QPD based on synthetic RHTLs and LHTLs. The use of the phase propagation difference between the RHTL and LHTL enables achieving a flat phase difference over a broad bandwidth. The compact design of the QPD, which employs only chip-lumped elements, results in a compact size for the fabricated BA. By using the proposed theories, a desired phase difference, not limited to 90°, can be achieved for a broadband range. For example, a broadband balun can also be made compact. Particularly, for a lower frequency band with a long wavelength, our main idea can lead to an extremely compact realization. By incorporating the presented theories and results, the circuit can be made MMIC, which can further minimize the losses and size, and extended to promise modern microwave applications that require compactness and broadbandness.

Data Availability

The data used to support the findings of this study are available from the corresponding author upon request.

Conflicts of Interest

The authors declare that they have no conflicts of interest regarding the publication of this paper.

Acknowledgments

This work was supported by the National Research Foundation of Korea (NRF) and funded by the Ministry of Science and ICT (grant no. NRF-2022R1A2C1012526) and the Ministry of Education (grant no. NRF-2022R1I1A1A01072512).

References

D. Betancourt and C. del RioBocio, “A novel methodology to feed phased array antennas,” IEEE Transactions on Antennas and Propagation, vol. 55, no. 9, pp. 2489–2494, 2007.
View at: Publisher Site | Google Scholar
K. X. Wang, X. Y. Zhang, and B. J. Hu, “Gysel power divider with arbitrary power ratios and filtering responses using coupling Structure,” IEEE Transactions on Microwave Theory and Techniques, vol. 62, no. 3, pp. 431–440, 2014.
View at: Publisher Site | Google Scholar
Z. S. Sun, L. J. Zhang, Y. P. Yan, and H. W. Yang, “Design of unequal dual-band Gysel power divider with arbitrary termination resistance,” IEEE Transactions on Microwave Theory and Techniques, vol. 59, no. 8, pp. 1955–1962, 2011.
View at: Publisher Site | Google Scholar
S. D. Joseph, Y. Huang, and S. S. H. Hsu, “Transmission lines-based impedance matching technique for broadband rectifier,” IEEE Access, vol. 9, pp. 4665–4672, 2021.
View at: Publisher Site | Google Scholar
L. H. Zhou, X. Y. Zhou, and W. S. Chan, “A compact and broadband Doherty power amplifier without post-matching network,” IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 70, no. 3, pp. 919–923, 2023.
View at: Publisher Site | Google Scholar
M. Elsbury, P. Dresselhaus, N. Bergren, C. Burroughs, S. Benz, and Z. Popovic, “Broadband lumped-element integrated $N$-Way power dividers for voltage standards,” IEEE Transactions on Microwave Theory and Techniques, vol. 57, no. 8, pp. 2055–2063, 2009.
View at: Publisher Site | Google Scholar
V. Iyer, S. N. Makarov, D. D. Harty, F. Nekoogar, and R. Ludwig, “A lumped circuit for wideband impedance matching of a non-resonant, short dipole or monopole antenna,” IEEE Transactions on Antennas and Propagation, vol. 58, no. 1, pp. 18–26, 2010.
View at: Publisher Site | Google Scholar
Z. Chen, Y. Wu, Y. Yang, and W. Wang, “‘A novel unequal lumped element coupler with arbitrary phase differences and arbitrary impedance matching,” IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 69, no. 2, pp. 369–373, 2022.
View at: Publisher Site | Google Scholar
H. Yoo, S. Lee, and H. Kim, “Broadband balun for monolithic microwave integrated circuit application,” Microwave and Optical Technology Letters, vol. 54, no. 1, pp. 203–206, 2012.
View at: Publisher Site | Google Scholar
T. Kawai, H. Mizuno, I. Ohta, and A. Enokihara, “Lumped-element quadrature Wilkinson power divider,” in Proceedings of the 2009 Asia Pacific Microwave Conference, pp. 1012–1015, Singapore, December 2009.
View at: Google Scholar
C. Tseng and C. Chang, “Improvement of return loss bandwidth of balanced amplifier using metamaterial-based quadrature power splitters,” IEEE Microwave and Wireless Components Letters, vol. 18, no. 4, pp. 269–271, 2008.
View at: Publisher Site | Google Scholar
Y.-C. Tsai, J.-L. Kuo, J.-H. Tsai, K.-Y. Lin, and H. Wang, “A 50–70 GHz I/Q modulator with improved sideband suppression using HPF/LPF based quadrature power splitter,” in Proceedings of the 2011 IEEE MTT-S International Microwave Symposium, pp. 1–4, Baltimore, MD, USA, June 2011.
View at: Google Scholar
S. Park, H. Han, C. Kim, J. Bae, Y. Cho, and H. Kim, “Compact band-selective power divider using one-dimensional metamaterial structure,” International Journal of Antennas and Propagation, vol. 2019, Article ID 3869812, 4 pages, 2019.
View at: Publisher Site | Google Scholar
D. K. Choudhary, N. Mishra, P. K. Singh, and A. Sharma, “Miniaturized power divider with triple-band filtering response using coupled line,” IEEE Access, vol. 11, Article ID 27602, 27608 pages, 2023.
View at: Publisher Site | Google Scholar
D. K. Choudhary and R. K. Chaudhary, “Compact D-CRLH structure for filtering power divider,” Progress In Electromagnetics Research Letters, vol. 94, pp. 93–101, 2020.
View at: Publisher Site | Google Scholar
C. H. Tseng and C. L. Chang, “A broadband quadrature power splitter using metamaterial transmission line,” IEEE Microwave and Wireless Components Letters, vol. 18, no. 1, pp. 25–27, 2008.
View at: Publisher Site | Google Scholar
D. Kumar Choudhary and R. Kumar Chaudhary, “Compact filtering antenna using asymmetric CPW-fed based CRLH structure,” AEU-International Journal of Electronics and Communications, vol. 126, Article ID 153462, 2020.
View at: Publisher Site | Google Scholar
D. M. Pozar, Microwave Engineering, Wiley, New York, NY, USA, 3 edition, 2005.
S. Z. Ibrahim, M. E. Bialkowski, and A. M. Abbosh, “Ultrawideband quadrature power divider employing double wireless via,” Microwave and Optical Technology Letters, vol. 54, no. 2, pp. 300–305, 2012.
View at: Publisher Site | Google Scholar
Q. Liu and Y. Liu, “A compact ultra‐wideband quadrature hybrid based on coupled-line phase shifter and power divider,” Microwave and Optical Technology Letters, vol. 57, no. 2, pp. 432–434, 2015.
View at: Publisher Site | Google Scholar
M. Lucarelli, S. Maddio, G. Collodi, and A. Cidronali, “A wideband quadrature power splitter covering 81.75% fractional bandwidth in single layer via‐less technology,” Microwave and Optical Technology Letters, vol. 59, no. 1, pp. 142–145, 2017.
View at: Publisher Site | Google Scholar
P. S. Huang and H. C. Lu, “Improvement of the phase shifter in 90$^{\circ}$ power splitter for UWB applications,” IEEE Microwave and Wireless Components Letters, vol. 22, no. 12, pp. 621–623, 2012.
View at: Publisher Site | Google Scholar
U. Dilshad, C. Chen, A. Altaf, A. Hu, and J. Miao, “A wide-band compact quadrature coupler on multi-layer package substrate,” Progress In Electromagnetics Research Letters, vol. 88, pp. 1–8, 2020.
View at: Publisher Site | Google Scholar
L. El Abdellaoui, A. Errkik, A. Tajmouati, and M. Latrach, “Design of a microstrip balanced amplifier using the Wilkinson power divider,” in Proceedings of the Third International Conference on Computing and Wireless Communication Systems, ICCWCS, Jersey, NJ, USA, April 2019.
View at: Google Scholar
J. Song, C. Huang, and G. Wen, “A novel balanced amplifier based on HMSIW coupler,” Frequenz, vol. 66, no. 3-4, pp. 75–78, 2012.
View at: Publisher Site | Google Scholar
S. Mojtaba, S. N. Hoseini, and R. Zaker, “Design of compact highly matched broadband balanced low-noise amplifier at X-band using CRLH transmission lines,” International Journal of RF and Microwave Computer-Aided Engineering, vol. 32, no. 10, Article ID e23315, 2022.
View at: Publisher Site | Google Scholar
P. Akkaraekthalin, S. Jongjitaree, and V. Vivek, “Coplanar waveguide balanced amplifier using bipolar junction transistors and backed ground-plane hybrids,” in Proceedings of IEEE Region 10 International Conference on Electrical and Electronic Technology, vol. 2, pp. 732–735, Singapore, August 2001.
View at: Google Scholar
R. Smolarz, K. Staszek, K. Wincza, and S. Gruszczynski, “Reduced-length tandem directional couplers designed in microstrip technique for use in balanced amplifiers,” in Proceedings of the 2022 24th International Microwave and Radar Conference (MIKON), pp. 1–4, Gdansk, Poland, September 2022.
View at: Google Scholar

Copyright

Copyright © 2023 Heeje Han and Hongjoon Kim. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

PDF Download Citation

Download other formats

Order printed copies

Views

184

Downloads

230

Citations