Development of horn antenna mixer array with internal local oscillator module for microwave imaging diagnosticsa) D. Kuwahara, N. Ito, Y. Nagayama, T. Yoshinaga, S. Yamaguchi, M. Yoshikawa, J. Kohagura, S. Sugito, Y. Kogi , and A. Mase Citation: Review of Scientific Instruments 85, 11D805 (2014); doi: 10.1063/1.4885471 View online: http://dx.doi.org/10.1063/1.4885471 View Table of Contents: http://scitation.aip.org/content/aip/journal/rsi/85/11?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Development of microwave imaging reflectometry on the HL-2A tokamaka) Rev. Sci. Instrum. 85, 11D816 (2014); 10.1063/1.4889741 Development of 3D microwave imaging reflectometry in LHD (invited)a) Rev. Sci. Instrum. 83, 10E305 (2012); 10.1063/1.4729259 Microwave imaging reflectometry studies for turbulence diagnostics on KSTARa) Rev. Sci. Instrum. 81, 10D933 (2010); 10.1063/1.3499606 Development of microwave imaging reflectometry in large helical devicea) Rev. Sci. Instrum. 79, 10F111 (2008); 10.1063/1.2993741 Synchronization of Oscillating Systems for Microwave Antennas and RF Electronics AIP Conf. Proc. 676, 15 (2003); 10.1063/1.1612192
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REVIEW OF SCIENTIFIC INSTRUMENTS 85, 11D805 (2014)
Development of horn antenna mixer array with internal local oscillator module for microwave imaging diagnosticsa) D. Kuwahara,1,b) N. Ito,2 Y. Nagayama,3 T. Yoshinaga,4 S. Yamaguchi,5 M. Yoshikawa,6 J. Kohagura,6 S. Sugito,7 Y. Kogi,8 and A. Mase9 1 Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan 2 Department of Intelligent System Engineering, Ube National College of Technology, Ube, Yamaguchi 755-8555, Japan 3 Department of Helical Plasma Research, National Institute for Fusion Science, Toki, Gifu 509-5292, Japan 4 Department of Applied Physics, National Defense Academy, Yokosuka, Kanagawa 239-0811, Japan 5 Department of Pure and Applied Physics, Kansai University, Suita, Osaka 564-8680, Japan 6 Graduate School of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan 7 Equipment Development Center, Institute for Molecular Science, Okazaki, Aichi 444-8585, Japan 8 Department of Information Electronics, Fukuoka Institute of Technology, Fukuoka, Fukuoka 811-0295, Japan 9 Art, Science and Technology Center for Cooperative Research, Kyusyu University, Kasuga, Fukuoka 816-8580, Japan
(Presented 2 June 2014; received 29 May 2014; accepted 13 June 2014; published online 8 July 2014) A new antenna array is proposed in order to improve the sensitivity and complexity of microwave imaging diagnostics systems such as a microwave imaging reflectometry, a microwave imaging interferometer, and an electron cyclotron emission imaging. The antenna array consists of five elements: a horn antenna, a waveguide-to-microstrip line transition, a mixer, a local oscillation (LO) module, and an intermediate frequency amplifier. By using an LO module, the LO optics can be removed, and the supplied LO power to each element can be equalized. We report details of the antenna array and characteristics of a prototype antenna array. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4885471] I. INTRODUCTION
Microwave imaging diagnostics can be potentially used to observe fluctuations in the electron density and electron temperature profiles in magnetically confined high temperature plasmas.1, 2 Moreover, medical imaging measurements have been used to observe tissues that are difficult to detect in an X-ray computed tomography, such as a breast tumor.3 Figure 1 shows a schematic diagram of a microwave imaging interferometer for a magnetically confined plasma device. In order to ensure compatibility with the observation of a high-density plasma and the use of a phase detection method, this system employs both heterodyne and frequency multiplication methods. An intermediate frequency (IF) signal is utilized to detect signals from the plasma, and a radio frequency (RF) is utilized as a probe beam. A mixer generates a pre-RF signal (15.0375 GHz) from a pre-local-oscillation frequency (pre-LO, 15 GHz) and an IF signal (37.5 MHz). An RF wave (60.150 GHz) and LO wave (60 GHz) are generated by quadruplers from the pre-RF and pre-LO signals. The RF wave is emitted by a horn antenna, and it enters a horn-antenna mixer array (HMA)4 via the plasma and a beam splitter. The LO wave is also emitted by a horn antenna and enters the HMA after reflection from the beam splitter. The HMA generates the IF signal (150 MHz), which contains the a) Contributed paper, published as part of the Proceedings of the 20th
Topical Conference on High-Temperature Plasma Diagnostics, Atlanta, Georgia, USA, June 2014. b) [email protected] 0034-6748/2014/85(11)/11D805/4/$30.00
electron-density fluctuation signals from the plasma by an internal mixer. Fluctuations are detected by phase and power detectors from the fluctuation of the IF signal. This system has problems related to the LO optics.5 First, the beam splitter, which is utilized as a beam combiner of the RF and LO waves, attenuates its intensities. Second, there is difference in the conversion losses of the internal mixer between a center channel and an edge channel of the HMA because of a deformed LO beam pattern. Third, the LO supplied by irradiation requires an expensive high-power amplifier owing to low coupling efficiency between the irradiation horn antenna and each HMA element. To overcome these problems, a new antenna system is designed. II. CONCEPT
Figure 2 shows schematic diagrams of the former and new HMAs. The former HMA consists of four important elements: horn antennas, waveguides, mixers, and IF circuits. The mixer, which is mounted on a high-frequency printed circuit board (PCB), is contained inside of a rectangular waveguide. The IF circuit is also mounted on the same PCB. The microwave is received on one side and the IF signal output is on the other; thus the antenna, mixer, and IF circuits are aligned. By placing this unit in parallel on the same PCB, a 1D microwave detector array can be formed. The horn and waveguide sections consist of a sandwich with the PCB placed between the upper and lower aluminum frames. Two halves of horns and waveguides are engraved on the two
85, 11D805-1
© 2014 AIP Publishing LLC
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11D805-2
Kuwahara et al.
Rev. Sci. Instrum. 85, 11D805 (2014)
FIG. 1. Schematic diagram of the microwave imaging interferometer.
frames by electrical discharge machining. Each horn antenna receives both RF and LO waves, whereas the mixer generates IF signals. However, various problems are caused by the LO supplied by irradiation. In contrast, the new HMA is designed such that LO irradiation is not necessary, and employs a microwave monolithic IC (MMIC) frequency quadrupler. The quadrupler converts an LO wave to a pre-LO signal having 1/4 of the frequency. By using the quadrupler, the mixer can receive the LO wave on the same PCB. When the frequencies of the RF and LO waves are 60.150 GHz and 60 GHz, respectively, 1/4 of the frequency of the LO wave is 15 GHz. The signal at the frequency of 15 GHz is easily divided, transmitted, and amplified on the PCB. In addition, signals in this frequency band can be transmitted with low loss by a coaxial connector. Therefore, the new HMA can provide LO waves to each mixer inside the antenna housing, without the LO optics. III. CIRCUIT ELEMENTS
A two-channel test module was fabricated to demonstrate the new HMA. In this module, frequencies of the RF, LO, and IF signals are designed to be 60.150 GHz, 60 GHz, and 150 MHz, respectively. The new elements in the new HMA are as follows: a waveguide-to-microstrip line transition, a mixer, a power divider, and an LO module. These elements are mounted on a high-frequency PCB with a thickness of 0.127 mm. A. Waveguide-to-microstrip line transition
The former HMA uses a converter that combines a single-probe-type waveguide-to-microstrip line transition and
FIG. 3. Finline waveguide-to-microstrip line transmission.
a single diode mixer. In contrast, the new HMA has to use a discrete waveguide-to-microstrip line transition. Figure 3(a) shows an outline of a finline waveguide-to-microstrip line transition.6 The size of the waveguide is 1.9 × 3.8 mm, which is equivalent to a V-band (50–75 GHz) waveguide. Figure 3(b) shows the transmission characteristic of a test module, where the transmission loss is −1.7 dB at a frequency of 60 GHz.
B. Mixer
A schematic view of the mixer module and the characteristics of the conversion loss are shown in Fig. 4. The mixer consists of a surface-mounted-type Schottky diode (Alpha Industries, DMK-2783-000), an LO coupling line and a bias circuit. Figure 4(b) shows the conversion losses as a function of RF power at a frequency of 60.150 GHz using four LO powers at a frequency of 60 GHz. According to the characteristics of the conversion loss, the saturation level is greater than ∼0 dBm.
FIG. 2. Schematics of the former and new HMAs.
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Rev. Sci. Instrum. 85, 11D805 (2014)
FIG. 4. Single diode mixer.
FIG. 5. Power divider.
FIG. 6. Quadrupler.
C. Power divider
Figure 5 shows a schematic diagram of a power divider and the transmission characteristics. The power divider employs a three-stage Wilkinson power divider as a broad-band power divider. The transmission losses are ∼4 dB, and isolation between the two channels is ∼13 dB at a frequency of 15 GHz (1/4 of the LO frequency). When the number of channels of the HMA is increased by more than two, the power dividers have to be connected by multiple stages. D. LO module
Figure 6 shows a schematic diagram of a V-band quadrupler and its output characteristics. The quadrupler MMIC is manufactured by Sumitomo Electric Device Innovations, Inc., model FMM5125X. The output frequency range of the quadrupler is 57–64 GHz. To decrease the contact resistances and parasitic capacitances, the quadrupler is mounted on the PCB using a conductive epoxy, and wire bonding is used to connect the MMIC and PCB pads. At an output frequency of 60 GHz, the output power is greater than 10 dBm above 10 dBm of the 1/4 LO input power. This is enough power to drive the above-mentioned mixer with low conversion loss.
FIG. 7. Two channels test module: (a) top view of the main PCB, (b) bottom view of the main PCB and IF transmission PCBs, (c) bird eye views of the test module, and (d) conversion losses.
E. Two-channel test module
Figure 7 shows a schematic view of the PCBs, photographs of the two-channel test module, and its conversion losses. In this module, SMA connectors are used with the IF outputs and a 1/4 LO input, and WR-15 flanges are used with the RF inputs. Figure 7(d) shows the results of the conversionloss test. In this test, the frequency and power of the 1/4 LO are 15 GHz and 10 dBm. Further, the frequency and power of the RF are 60.150 GHz and −10 to −35 dBm, respectively. According to Fig. 7(d), the conversion losses of channels 1 and 2 exhibit similar characteristics. These values are better than the former HMA.5 IV. CONCLUSION
On the basis of former HMA, a new HMA, which has an internal LO module, was proposed for microwave imaging diagnostics. The finline waveguide-to-microstrip line transmission, single-diode mixer, power divider, and LO module have been newly developed. In order to demonstrate the new HMA,
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 137.207.120.173 On: Fri, 21 Nov 2014 19:10:32
11D805-4
Kuwahara et al.
a two-channel test module was manufactured. From an evaluation of the conversion losses, the proposed method can be installed as the detector array of a microwave imaging diagnostic system.
Rev. Sci. Instrum. 85, 11D805 (2014)
ciety and the NIFS collaboration research program (NIFS13KUGM078). 1 B.
Tobias et al., Plasma Fusion Res. 6, 2106042 (2012). Nagayama et al., Rev. Sci. Instrum. 83, 10E305 (2012). 3 D. Zhang and A. Mase, Biomed. Eng. Appl. Basis Commun. 26, 1450004 (2014). 4 D. Kuwahara et al., Rev. Sci. Instrum. 81, 10D919 (2010). 5 D. Kuwahara et al., J. Plasma Fusion Res. SERIES 8, 649 (2009). 6 G. E. Ponchak et al., NASA Tech. Memo. 88905 (1986). 2 Y.
ACKNOWLEDGMENTS
This work was supported by the Sasakawa Scientific Research Grant from the Japan Science So-
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 137.207.120.173 On: Fri, 21 Nov 2014 19:10:32
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 137.207.120.173 On: Fri, 21 Nov 2014 19:10:32
REVIEW OF SCIENTIFIC INSTRUMENTS 85, 11D805 (2014)
Development of horn antenna mixer array with internal local oscillator module for microwave imaging diagnosticsa) D. Kuwahara,1,b) N. Ito,2 Y. Nagayama,3 T. Yoshinaga,4 S. Yamaguchi,5 M. Yoshikawa,6 J. Kohagura,6 S. Sugito,7 Y. Kogi,8 and A. Mase9 1 Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan 2 Department of Intelligent System Engineering, Ube National College of Technology, Ube, Yamaguchi 755-8555, Japan 3 Department of Helical Plasma Research, National Institute for Fusion Science, Toki, Gifu 509-5292, Japan 4 Department of Applied Physics, National Defense Academy, Yokosuka, Kanagawa 239-0811, Japan 5 Department of Pure and Applied Physics, Kansai University, Suita, Osaka 564-8680, Japan 6 Graduate School of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan 7 Equipment Development Center, Institute for Molecular Science, Okazaki, Aichi 444-8585, Japan 8 Department of Information Electronics, Fukuoka Institute of Technology, Fukuoka, Fukuoka 811-0295, Japan 9 Art, Science and Technology Center for Cooperative Research, Kyusyu University, Kasuga, Fukuoka 816-8580, Japan
(Presented 2 June 2014; received 29 May 2014; accepted 13 June 2014; published online 8 July 2014) A new antenna array is proposed in order to improve the sensitivity and complexity of microwave imaging diagnostics systems such as a microwave imaging reflectometry, a microwave imaging interferometer, and an electron cyclotron emission imaging. The antenna array consists of five elements: a horn antenna, a waveguide-to-microstrip line transition, a mixer, a local oscillation (LO) module, and an intermediate frequency amplifier. By using an LO module, the LO optics can be removed, and the supplied LO power to each element can be equalized. We report details of the antenna array and characteristics of a prototype antenna array. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4885471] I. INTRODUCTION
Microwave imaging diagnostics can be potentially used to observe fluctuations in the electron density and electron temperature profiles in magnetically confined high temperature plasmas.1, 2 Moreover, medical imaging measurements have been used to observe tissues that are difficult to detect in an X-ray computed tomography, such as a breast tumor.3 Figure 1 shows a schematic diagram of a microwave imaging interferometer for a magnetically confined plasma device. In order to ensure compatibility with the observation of a high-density plasma and the use of a phase detection method, this system employs both heterodyne and frequency multiplication methods. An intermediate frequency (IF) signal is utilized to detect signals from the plasma, and a radio frequency (RF) is utilized as a probe beam. A mixer generates a pre-RF signal (15.0375 GHz) from a pre-local-oscillation frequency (pre-LO, 15 GHz) and an IF signal (37.5 MHz). An RF wave (60.150 GHz) and LO wave (60 GHz) are generated by quadruplers from the pre-RF and pre-LO signals. The RF wave is emitted by a horn antenna, and it enters a horn-antenna mixer array (HMA)4 via the plasma and a beam splitter. The LO wave is also emitted by a horn antenna and enters the HMA after reflection from the beam splitter. The HMA generates the IF signal (150 MHz), which contains the a) Contributed paper, published as part of the Proceedings of the 20th
Topical Conference on High-Temperature Plasma Diagnostics, Atlanta, Georgia, USA, June 2014. b) [email protected] 0034-6748/2014/85(11)/11D805/4/$30.00
electron-density fluctuation signals from the plasma by an internal mixer. Fluctuations are detected by phase and power detectors from the fluctuation of the IF signal. This system has problems related to the LO optics.5 First, the beam splitter, which is utilized as a beam combiner of the RF and LO waves, attenuates its intensities. Second, there is difference in the conversion losses of the internal mixer between a center channel and an edge channel of the HMA because of a deformed LO beam pattern. Third, the LO supplied by irradiation requires an expensive high-power amplifier owing to low coupling efficiency between the irradiation horn antenna and each HMA element. To overcome these problems, a new antenna system is designed. II. CONCEPT
Figure 2 shows schematic diagrams of the former and new HMAs. The former HMA consists of four important elements: horn antennas, waveguides, mixers, and IF circuits. The mixer, which is mounted on a high-frequency printed circuit board (PCB), is contained inside of a rectangular waveguide. The IF circuit is also mounted on the same PCB. The microwave is received on one side and the IF signal output is on the other; thus the antenna, mixer, and IF circuits are aligned. By placing this unit in parallel on the same PCB, a 1D microwave detector array can be formed. The horn and waveguide sections consist of a sandwich with the PCB placed between the upper and lower aluminum frames. Two halves of horns and waveguides are engraved on the two
85, 11D805-1
© 2014 AIP Publishing LLC
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 137.207.120.173 On: Fri, 21 Nov 2014 19:10:32
11D805-2
Kuwahara et al.
Rev. Sci. Instrum. 85, 11D805 (2014)
FIG. 1. Schematic diagram of the microwave imaging interferometer.
frames by electrical discharge machining. Each horn antenna receives both RF and LO waves, whereas the mixer generates IF signals. However, various problems are caused by the LO supplied by irradiation. In contrast, the new HMA is designed such that LO irradiation is not necessary, and employs a microwave monolithic IC (MMIC) frequency quadrupler. The quadrupler converts an LO wave to a pre-LO signal having 1/4 of the frequency. By using the quadrupler, the mixer can receive the LO wave on the same PCB. When the frequencies of the RF and LO waves are 60.150 GHz and 60 GHz, respectively, 1/4 of the frequency of the LO wave is 15 GHz. The signal at the frequency of 15 GHz is easily divided, transmitted, and amplified on the PCB. In addition, signals in this frequency band can be transmitted with low loss by a coaxial connector. Therefore, the new HMA can provide LO waves to each mixer inside the antenna housing, without the LO optics. III. CIRCUIT ELEMENTS
A two-channel test module was fabricated to demonstrate the new HMA. In this module, frequencies of the RF, LO, and IF signals are designed to be 60.150 GHz, 60 GHz, and 150 MHz, respectively. The new elements in the new HMA are as follows: a waveguide-to-microstrip line transition, a mixer, a power divider, and an LO module. These elements are mounted on a high-frequency PCB with a thickness of 0.127 mm. A. Waveguide-to-microstrip line transition
The former HMA uses a converter that combines a single-probe-type waveguide-to-microstrip line transition and
FIG. 3. Finline waveguide-to-microstrip line transmission.
a single diode mixer. In contrast, the new HMA has to use a discrete waveguide-to-microstrip line transition. Figure 3(a) shows an outline of a finline waveguide-to-microstrip line transition.6 The size of the waveguide is 1.9 × 3.8 mm, which is equivalent to a V-band (50–75 GHz) waveguide. Figure 3(b) shows the transmission characteristic of a test module, where the transmission loss is −1.7 dB at a frequency of 60 GHz.
B. Mixer
A schematic view of the mixer module and the characteristics of the conversion loss are shown in Fig. 4. The mixer consists of a surface-mounted-type Schottky diode (Alpha Industries, DMK-2783-000), an LO coupling line and a bias circuit. Figure 4(b) shows the conversion losses as a function of RF power at a frequency of 60.150 GHz using four LO powers at a frequency of 60 GHz. According to the characteristics of the conversion loss, the saturation level is greater than ∼0 dBm.
FIG. 2. Schematics of the former and new HMAs.
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11D805-3
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Rev. Sci. Instrum. 85, 11D805 (2014)
FIG. 4. Single diode mixer.
FIG. 5. Power divider.
FIG. 6. Quadrupler.
C. Power divider
Figure 5 shows a schematic diagram of a power divider and the transmission characteristics. The power divider employs a three-stage Wilkinson power divider as a broad-band power divider. The transmission losses are ∼4 dB, and isolation between the two channels is ∼13 dB at a frequency of 15 GHz (1/4 of the LO frequency). When the number of channels of the HMA is increased by more than two, the power dividers have to be connected by multiple stages. D. LO module
Figure 6 shows a schematic diagram of a V-band quadrupler and its output characteristics. The quadrupler MMIC is manufactured by Sumitomo Electric Device Innovations, Inc., model FMM5125X. The output frequency range of the quadrupler is 57–64 GHz. To decrease the contact resistances and parasitic capacitances, the quadrupler is mounted on the PCB using a conductive epoxy, and wire bonding is used to connect the MMIC and PCB pads. At an output frequency of 60 GHz, the output power is greater than 10 dBm above 10 dBm of the 1/4 LO input power. This is enough power to drive the above-mentioned mixer with low conversion loss.
FIG. 7. Two channels test module: (a) top view of the main PCB, (b) bottom view of the main PCB and IF transmission PCBs, (c) bird eye views of the test module, and (d) conversion losses.
E. Two-channel test module
Figure 7 shows a schematic view of the PCBs, photographs of the two-channel test module, and its conversion losses. In this module, SMA connectors are used with the IF outputs and a 1/4 LO input, and WR-15 flanges are used with the RF inputs. Figure 7(d) shows the results of the conversionloss test. In this test, the frequency and power of the 1/4 LO are 15 GHz and 10 dBm. Further, the frequency and power of the RF are 60.150 GHz and −10 to −35 dBm, respectively. According to Fig. 7(d), the conversion losses of channels 1 and 2 exhibit similar characteristics. These values are better than the former HMA.5 IV. CONCLUSION
On the basis of former HMA, a new HMA, which has an internal LO module, was proposed for microwave imaging diagnostics. The finline waveguide-to-microstrip line transmission, single-diode mixer, power divider, and LO module have been newly developed. In order to demonstrate the new HMA,
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 137.207.120.173 On: Fri, 21 Nov 2014 19:10:32
11D805-4
Kuwahara et al.
a two-channel test module was manufactured. From an evaluation of the conversion losses, the proposed method can be installed as the detector array of a microwave imaging diagnostic system.
Rev. Sci. Instrum. 85, 11D805 (2014)
ciety and the NIFS collaboration research program (NIFS13KUGM078). 1 B.
Tobias et al., Plasma Fusion Res. 6, 2106042 (2012). Nagayama et al., Rev. Sci. Instrum. 83, 10E305 (2012). 3 D. Zhang and A. Mase, Biomed. Eng. Appl. Basis Commun. 26, 1450004 (2014). 4 D. Kuwahara et al., Rev. Sci. Instrum. 81, 10D919 (2010). 5 D. Kuwahara et al., J. Plasma Fusion Res. SERIES 8, 649 (2009). 6 G. E. Ponchak et al., NASA Tech. Memo. 88905 (1986). 2 Y.
ACKNOWLEDGMENTS
This work was supported by the Sasakawa Scientific Research Grant from the Japan Science So-
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 137.207.120.173 On: Fri, 21 Nov 2014 19:10:32
