A GSM900/DCS1800 Dual-Band MMIC Power ... - Semantic Scholar

IEICE TRANS. ELECTRON., VOL.E82–C, NO.11 NOVEMBER 1999

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PAPER

Special Issue on High Frequency/Speed Devices in the 21st Century

A GSM900/DCS1800 Dual-Band MMIC Power Amplifier Using Outside-Base/Center-Via-Hole Layout Multifinger HBT Kazutomi MORI†a) , Kenichiro CHOUMEI†† , Teruyuki SHIMURA†† , Tadashi TAKAGI† , Yukio IKEDA† , and Osami ISHIDA† , Members

SUMMARY A GSM900/DCS1800 dual-band AlGaAs/GaAs HBT (heterojunction bipolar transistor) MMIC (monolithic microwave integrated circuit) power amplifier has been developed. It includes power amplifiers for GSM900 and DCS1800, constant voltage bias circuits and a d.c. switch. In order to achieve high efficiency, the outside-base/center-via-hole layout is applied to the final-stage HBT of the MMIC amplifier. The layout can realize uniform output load impedance and thermal distribution of each HBT finger. The developed MMIC amplifier could provided output power of 34.5 dBm and power-added efficiency of 53.4% for GSM900, and output power of 32.0 dBm and power-added efficiency of 41.8% for DCS1800. key words: microwave, ampli er, eÆciency, layout, hetero-

junction bipolar transistor, multi nger

1.

Introduction

In recent years, low cost and single power supply are required for power amplifiers used in mobile and satellite communications systems, in addition to high efficiency [1]–[6]. An HBT (heterojunction bipolar transistor) is a good candidate for low-cost and single-powersupply power amplifiers. A multifinger HBT must be used for the final-stage amplifier to achieve the required power at a low supplied voltage of 3.2 V. The fish-bone layout multifinger HBT is conventionally used in several HBT power amplifiers [7]–[9]. In a multi-finger HBT, uniform operation of each HBT finger is necessary to achieve high efficiency. However, unbalanced operation of each HBT finger occurs because of its unequal input/output impedance and thermal distribution. Several personal communications services are provided, such as GSM and DCS, and multimode handsets which can be switched automatically across the different services are necessary [10], [11]. Therefore, a small multimode power amplifier in one package, which can be used for several personal communication services, is required. Manuscript received March 24, 1999. Manuscript revised June 14, 1999. † The authors are with Information Technology R&D Center, Mitsubishi Electric Corporation, Kamakura-shi, 247-8501 Japan. †† The authors are with High Frequency & Optical Semiconductor Division, Mitsubishi Electric Corporation, Itamishi, 664-8641 Japan. a) E-mail: [email protected]

In this paper, we propose a novel multifinger HBT layout which can realize uniform output load impedance and thermal distribution of each HBT finger to achieve high efficiency, and we present a GSM900/DCS1800 dual-band AlGaAs/GaAs HBT MMIC (monolithic microwave integrated circuit) power amplifier which employs the outside-base/center-viahole layout multifinger HBT in the final-stage amplifier. The dual-band amplifier incorporates a GSM900 power amplifier, a DCS1800 power amplifier, their bias circuits, and a d.c. switch for switching GSM900/DCS1800, and is fabricated in a plastic molded package of 7.0 mm×6.4 mm×1.0 mm. Output power of 34.5 dBm and power-added efficiency of 53.4% have been obtained for GSM900, while output power of 32.0 dBm and power-added efficiency of 41.8% have been obtained for DCS1800. 2.

Multifinger HBT Device Layout

We use an AlGaAs/GaAs HBT device [8] in the power amplifier to achieve a single positive power supply and low cost. In order to provide high output power of over 30 dBm, multifinger HBT must be used. Figure 1 shows the fish-bone multifinger layout for the 3rd-stage HBT. Figure 1(a) presents the conventional outsidecollector/side-via-hole layout of the multifinger HBT [8] which consists of n HBT cells comprised of m HBT fingers (m, n: integer). In Fig. 1, the load impedances (Zout C1 · · · Zout CN ) of all collector pads are the same, and the source impedances (Zin B1 · · · Zin BM ) of all base pads are also the same and expressed as follows. Zout Zin

C1

B1

= Zout = Zin

C2

B2

= · · · = Zout

= · · · = Zin

CN

BM

= Zout · N (1)

= Zin · M,

(2)

where Zout and Zin are the load and source impedances of the multifinger HBT, respectively. The outside collector pads (C1 , CN ) are connected to m HBT fingers and the inside collector pads (C2 · · · CN −1 ) are connected to 2×m HBT fingers. Therefore, the output load impedance (Zout 1j , Zout nj : j = 1 · · · m) of the HBT fingers (HBT1j , HBTnj : j = 1 · · · m) located in


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Fig. 2

Fig. 1 Multifinger layout for the 3rd-stage HBT, (a) Outsidecollector/side-via-hole layout (conventional), (b) Outsidebase/center-via-hole layout (proposed).

outside cells and the output load impedance (Zout ij : i = 2 · · · n − 1, j = 1 · · · m) of the HBT fingers (HBTij : i = 2 · · · n − 1, j = 1 · · · m) located in inside cells are given as follows. Zout

1j

Zout

ij

= Zout

nj

= Zout · N · m,

j = 1 · · · m (3)

= Zout ·N ·2 · m, i = 2 · · · n−1, j = 1 · · · m(4)

Therefore, it is clear that the output load impedance of the HBT fingers located in outside cells is half of the output load impedance of the HBT fingers located in inside cells, while all input source impedances (Zin ij : i = 1 · · · n, j = 1 · · · m) are the same values, as shown in the following equation. Zin

ij

= Zin ·M · 2 · m,

i = 1 · · · n, j = 1 · · · m

(5)

This results in a low efficiency of the multifinger HBT because of unbalanced operation between the HBT fingers located in outside and inside cells. Figure 1(b) shows the proposed layout (outsidebase/center-via-hole layout) of the multifinger HBT which can achieve uniform output load impedance (Zout ij : i = 1 · · · n, j = 1 · · · m) of each HBT finger, while the input source impedance (Zin 1j , Zin (n/2)j , Zin (n/2+1)j , Zin nj : j = 1 · · · m) of the HBT fingers (HBT1j , HBT(n/2)j , HBT(n/2 + 1)j , HBTnj : j = 1 · · · m) located in outside cells is half the input source impedance (Zin ij : i = 2 · · · n/2 − 1 and i = n/2 + 2 · · · n − 1, j = 1 · · · m) of the HBT fingers (HBTij : i = 2 · · · n/2 − 1 and n/2 + 2 · · · n − 1, j = 1 · · · m) located in inside cells. The output load impedance has significant effects on the output power

Circuit for calculation of multifinger HBTs.

and efficiency of amplifiers, compared with input source impedance. Therefore, it is considered that the HBT with the proposed layout (outside-base/center-via-hole layout) can achieve a more uniform operation of each HBT finger and higher efficiency performance than the conventional-layout HBT (outside-collector/sidevia-hole). In the proposed layout, the emitter via hole is located in the center of the multifinger HBT, while it is located outside of the HBT in the conventional layout. This is because the temperature of the HBT finger located in the center of the HBT is higher than that located outside of the HBT [8]. It is considered that the proposed center-via-hole layout can provide a more uniform thermal distribution than the conventional sidevia-hole layout. 3.

Efficiency of Multifinger HBT

We calculate the output power and power-added efficiency of the multifinger HBTs in both conventional and proposed layouts. The circuit used for the calculation of multifinger HBTs is shown in Fig. 2. We calculate the output power and power-added efficiency for the HBT, the emitter size of which is 4 × 20 µm2 × 80 fingers. An HBT cell consists of 10 HBT fingers. A Gummel-Poon large-signal model [12] and harmonic balance method [13] are used to calculate large signal characteristics of the HBT. We cannot calculate the large signal characteristics of a parallel combined 80finger HBT by using 80 large-signal HBT models because of computational memory limitation. Therefore, we use the following method. First, we calculate the output power, poweradded efficiency, and phase deviation at the optimum source impedance (Γin opt ) and optimum load impedance (Γout opt ) where the maximum power-added efficiency is obtained for an HBT cell (10 fingers). Next, we calculate the characteristics at the optimum source impedance (Γin opt ) and half the optimum load impedance (Γout opt /2) for the outside HBT cell of the conventional-layout multifinger HBT shown in Fig. 1(a). We also calculate the characteristics at half the optimum source impedance (Γin opt /2) and the optimum load impedance (Γout opt ) for the outside

MORI et al: A GSM900/DCS1800 DUAL-BAND MMIC POWER AMPLIFIER

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Fig. 3 Calculated output power and power-added efficiency for the outside-collector/outside-base multifinger HBT.

Fig. 4 Measured output power and power-added efficiency for the outside-collector/side-via-hole layout and outsidebase/center-via-hole layout multifinger HBTs.

HBT cell of the proposed multifinger layout shown in Fig. 1(b). Finally, we combine the output power characteristics of 8 HBT cells, taking account of the phase deviation characteristics. Figure 3 shows calculated output power and power-added efficiency for the conventional outsidecollector/side-via-hole layout and the proposed outsidebase/center-via-hole layout multifinger HBT (4 × 20 µm2 × 80 fingers) at 1.75 GHz. The ideally combined characteristics are also presented in Fig. 3. In Fig. 3, the solid and the broken lines represent characteristics for the proposed- and conventional-layout HBTs, respectively and the dotted line represents characteristics for the ideal layout. It is clearly shown that the proposed multi-finger HBT layout achieves the same performance as the ideal-layout HBT; moreover, the power-added efficiency of the conventional-layout HBT is 4.3% lower than the proposed-layout HBT. This indicates that the uniformity of the output load impedance is more important than that of the input source impedance. In Fig. 3, the output power of the conventional-layout HBT is slightly higher than that of the ideal-layout. In general, the optimum load impedance for output power is lower than that for efficiency. In the conventionallayout HBT, the load impedance of the outside HBT cell is lower than the load impedance of the inside HBT cell, that is, the optimum load impedance for efficiency. Therefore, the output power of the outside HBT cell is higher than that of the inside HBT cell, while the efficiency of the outside HBT cell is lower than that of the inside HBT cell. In the ideal-layout HBT, the load impedances of all HBT cells are optimized for efficiency. This indicates that the conventional-layout HBT achieves higher output power and lower efficiency than the ideal-layout HBT. It also indicates that the load impedance of inside HBT cells of the conventionallayout HBT is optimized for efficiency, but the load impedance of outside HBT cells of the conventionallayout multifinger HBT is slightly different from the

Table 1 Measured thermal conductivity of the conventionaland proposed-layout HBTs.

optimum load impedance in the calculation. Figure 4 shows measured output power and power-added efficiency for the conventional outsidecollector/side-via-hole layout and the proposed outsidebase/center-via-hole layout multifinger HBT (4 × 20 µm2 × 80 fingers) at 1.75 GHz. In Fig. 4, the solid and broken lines represent the characteristics for the proposed- and conventional-layout HBTs. It is clear that the outside-base/center-via-hole layout HBT achieved 3.1% higher efficiency than the outsidecollector/side-via-hole layout HBT. It is clear that the proposed layout can provide higher efficiency than the conventional layout without increasing the chip size. In Fig. 4, the output power of the proposed-layout HBT is slightly higher than that of the conventional-layout HBT, while the output power of the proposed-layout HBT is slightly lower than that of the conventionallayout HBT in Fig. 3. This is because the load impedance of the conventional-layout HBT is slightly different from the optimum load impedance in the calculation as mentioned in the previous paragraph, while it is completely optimized for efficiency in the measurement. Therefore, we use the outside-base/centervia-hole layout HBT (Fig. 1.(b)) in the GSM900 and DCS1800 MMICs. We obtained the thermal conductivity of the conventional- and proposed-layout HBTs to investigate the thermal effects of the proposed center-via-hole lay-


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out. Table 1 shows the measured thermal conductivity of the conventional- and proposed-layout HBTs. It is clear in Table 1 that the thermal conductivity of the proposed center-via-hole layout HBT is about 3.9◦ C/W (20%) lower than that of the conventional-layout HBT. Thermal paths of the multifinger HBT in this paper are the emitter air bridge, the emitter via hole and the GaAs substrate. The emitter via hole is considered to play a significant role, while the main thermal path is considered to be the emitter air bridge. Therefore, it is considered that there is a slight increase in output power and efficiency when the center-via-hole layout is employed. According to the calculation results shown in Fig. 3, however, the outside-base layout is considered to be the dominant factor in the improvement of efficiency in Fig. 4. 4.

GSM900/DCS1800 Design

Dual-Band

Amplifier

Figures 5 and 6 show a block diagram and a photograph of the GSM900/DCS1800 dual-band MMIC amplifier, respectively. The IC incorporates GSM900/DCS1800 three-stage power amplifiers, their constant voltage bias circuit, and a d.c. power control voltage (Vpc ) switch for GSM900/DCS1800. These functions are integrated in a 26-lead, surface-mount-type plastic package (7.0 mm×6.4 mm×1.0 mm). Figure 7 shows a schematic diagram of the threestage HBT MMIC amplifier for GSM900/DCS1800. The emitter sizes of the 1st-, 2nd-, and 3rd-stage HBTs for the GSM900 amplifier are 4, 24, and 120 fingers (unit HBT finger: 4×20 µm2 ), respectively. The output-base/center-via-hole layout multifinger HBT proposed in Sect. 2 is used for the final-stage HBT. A negative feedback circuit, series base resistance and series base bias resistance are employed for the stability of HBT at each stage. In constant-current operation, the drain current and output power cannot increase near the saturation region with an increase of input power because of the limitation of the constant base current. There-

Fig. 7

fore, constant voltage operation is required to achieve high power and high efficiency for HBTs. A low control current is also required because the drive current of the power control voltage source (usually D/A converter) is limited. Figure 8 shows a schematic diagram of the constant voltage bias circuit. Constant base voltage is supplied to HBT at each stage through this bias

Fig. 5 Block diagram of GSM900/DCS1800 dual-band HBT MMIC amplifier.

Fig. 6 Photograph of GSM900/DCS1800 dual-band HBT MMIC amplifier.

Schematic diagram of the three-stage HBT MMIC amplifiers for GSM900/DCS1800.


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Fig. 8

Schematic diagram of constant voltage base bias circuit. Fig. 10 Photographs of MMIC chips of GSM900/DCS1800 dual-band HBT power amplifiers.

Fig. 9 Calculated d.c. characteristics of the constant voltage bias circuit of the 3rd-stage HBT for GSM900.

circuit. Rpc and Rcc are used to stabilize the bias circuit, and Rb bias represents isolation between the bias circuit and RF HBT. Figure 9 shows calculated d.c. characteristics of the bias circuit of the 3rd-stage HBT for GSM900. In Fig. 9, the voltage drop of base bias Vb is suppressed within 0.15 V when the base current increases to 100 mA. The 1st-, 2nd- and 3rd-stage HBTs, bias circuits, stability circuits, input and 2-3 interstage matching circuits are fabricated on a single GaAs MMIC chip. The 1-2 interstage matching circuits and output matching circuits are mounted outside of the MMIC chip to reduce the chip size. The 2-3 interstage matching circuits are comprised of a parallel capacitance and a series micro-strip line providing interstage matching since the impedance between the 2nd- and 3rd-stage HBTs is very low (; 1 Ω) and 2-3 interstage matching is difficult. The 1-2 interstage matching circuits consist of a parallel inductance (bias feed line) and series capacitance, thereby reducing the GaAs chip size. The circuit configuration of DCS1800 amplifier is the same as that of GSM900 amplifier except for the emitter size of each HBT stage. The emitter sizes of the 1st-, 2nd-, and 3rd-stage HBTs are 2, 10, and 80 fingers (unit HBT finger: 4×20 µm2 ), respectively. Figure 10 shows photographs of the GSM900 and

Fig. 11 Measured output power and power-added efficiency of the three-stage amplifier for GSM900 (outside-base/center-viahole layout).

DCS1800 MMICs whose chip sizes are 1.38×1.60 mm2 and 1.38×1.28 mm2 , respectively. 5.

Measurement Results

5.1 Power Amplifier for GSM900 We developed an HBT MMIC power amplifier for GSM900 where the final-stage HBT employs the proposed outside-base/center-via-hole layout in realizing uniform output load impedance and thermal distribution of each HBT finger. Figure 11 shows the measured output power and power-added efficiency of the three-stage amplifier for GSM900 at 900 MHz and Pin =5 dBm. An output power of 34.5 dBm and poweradded efficiency of 53.4% were obtained. It is shown in Fig. 11 that we can control the output power of the amplifier in the dynamic range of about 80 dB by adjusting the power control voltage (Vpc ). Figure 12 presents the measured total collector current (Ic total ) and total power control current (Ipc total ) of the three-stage


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Fig. 12 Measured total collector current and total power control current of the three-stage amplifier for GSM900 (outsidebase/center-via-hole layout).

Fig. 13 Measured output power and power-added efficiency of the three-stage amplifier for DCS1800 (outside-base/center-viahole layout).

Table 2 Measured characteristics of the two types of threestage amplifiers for GSM900.

amplifier for GSM900. Ipc total is suppressed to below 4 mA by the base bias circuits shown in Fig. 8. No unexpected oscillation is obtained within the output VSWR= 6. Two types of three-stage amplifiers are manufactured and tested to confirm the effects of novel multifinger layout. The AMP 1 employs the proposed outsidecollector/side-via-hole layout in the final-stage HBT, and the AMP 2 employs the conventional outsidecollector/side-via-hole layout in the final-stage HBT. Table 2 shows the measured characteristics of the two types of three-stage amplifiers for GSM900. It is clear that the power-added efficiency of the amplifier AMP 1 is about 3% higher than that of AMP 2. It is confirmed that the efficiency can be improved by applying the proposed outside-base/center-via-hole layout to multifinger HBTs.

Fig. 14 Measured total collector current and total power control current of the three-stage amplifier for DCS1800 (outsidebase/center-via-hole layout).

Table 3 Measured characteristics of the three-stage amplifier for DCS1800.

5.2 Power Amplifier for DCS1800 We developed an HBT MMIC power amplifier for DCS1800 which employs the outside-base/center-viahole layout. Figure 13 shows the measured output power and power-added efficiency of the three-stage amplifier for DCS1800 at 1747.5 MHz and Pin = 5 dBm. Figure 14 presents the measured total collector current

(Ic total ) and total power control current (Ipc total ) of the three-stage amplifier for DCS1800. Table 3 summarizes the measured characteristics of the DCS1800 power amplifier for DCS1800. An output power of 32.0 dBm and power-added efficiency of 41.8% were obtained. Ipc total is suppressed to below 4 mA. No unexpected oscillation is obtained within the output


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VSWR= 6. 6.

Conclusion

We developed a GSM900/DCS1800 dual-band AlGaAs/GaAs HBT MMIC power amplifier with a single positive power supply. It employs an HBT device which provides a single positive power supply and low cost. The amplifier includes power amplifiers for GSM900 and DCS1800, constant voltage bias circuits and a d.c. switch. In order to achieve high efficiency, it utilizes a novel outside-base/center-via-hole layout which realizes uniform output load impedance and uniform thermal distribution of each HBT finger. An output power of 34.5 dBm and power-added efficiency of 53.4% were obtained for GSM900, while an output power of 32.0 dBm and power-added efficiency of 41.8% were obtained for DCS1800. References [1] K. Sakuno, M. Akagi, H. Sato, M. Miyauchi, M. Hasegawa, T. Yoshimasu, and S. Hara, “A 3.5 W HBT MMIC power amplifier module for mobile communications,” IEEE 1994 Microwave and Millimeter-Wave Monolithic Circuits Symposium Dig., pp.63–66, 1994. [2] W. Abey, T. Kawai, I. Okamoto, M. Suzuki, C. Khandavalli, W. Kennan, Y. Tateno, M. Nagahara, and M. Takikawa, “An E-mode GaAs FET power amplifier MMIC for GSM phones,” IEEE MTT-S Dig., pp.1315– 1318, 1997. [3] I. Yoshida, “A 3.6 V 4 W 0.2 cc Si power-MOS-amplifier module for GSM handset phone,” IEEE ISSCC Dig., pp.50– 51, 1998. [4] T. Iwai, S. Ohara, T. Miyashita, and K. Joshin, “63.2% high efficiency and high linearity two-stage InGaP/GaAs HBT power amplifier for personal digital cellular phone system,” IEEE MTT-S Dig., pp.435–438, 1998. [5] H. Asano, S. Hara, and S. Komai, “A 900 MHz HBT power amplifier MMICs with 55% efficiency, at 3.3 V operation,” IEEE MTT-S Dig., pp.205–208, 1998. [6] M. Nishida, S. Murai, H. Uda, H. Tominaga, T. Sawai, and A. Ibaraki, “A high efficiency GaAs power amplifier module with a single voltage for digital cellular phone systems,” IEEE MTT-S, Dig., pp.443–446, 1998. [7] W. Liu, S. Nelson, D.G. Hill, and A. Khatibzadeh, “Current gain collapse in microwave multifinger heterojunction bipolar transistors operated at very high power density,” IEEE Trans. Electron. Devices, vol.40, no.11, pp.1917–1927, Nov. 1993. [8] T. Shimura, T. Miura, Y. Uneme, H. Nakano, R. Hattori, M. Otsubo, K. Mori, A. Inoue, and N. Tanino, “High efficiency AlGaAs/GaAs power HBTs at a low supply voltage for digital cellular phones,” IEICE Trans. Electron., vol.E80-C, no.6, pp.740–745, June 1997. [9] U. Shaper and P. Zwicknagl, “Physical scaling rules for AlGaAs/GaAs power HBT’s based on a small-signal equivalent circuit,” IEEE Trans. Microwave Theory & Tech., vol.46, no.7, pp.1006–1009, July 1998. [10] S. Maeng, S. Chun, J. Lee, C. Lee, K. Youn, and H. Park, “A GaAs power amplifier for 3.3 V CDMA/AMPS dualmode cellular phones,” IEEE Trans. Microwave Theory & Tech., vol.43, no.12, pp.2839–2844, Dec. 1995.

[11] A. Adar, “A high efficiency single chain GaAs MESFET MMIC dual band power amplifier for GSM/DCS handsets,” IEEE GaAs IC Symp. Dig., pp.69–72, 1998. [12] Hewlett Packard Company, HP Microwave & RF Circuit Design, Component Catalog. [13] M.S. Nakhla and J. Valch, “A piecewise harmonic balance technique for determination of periodic response of nonlinear systems,” IEEE Trans. Circuits & Syst., vol.CAS-23, no.2, pp.85–91, Feb. 1976.

Kazutomi Mori received his B.E. and M.E. degrees in electronic engineering from Waseda University in 1990 and 1992, respectively. In 1992, he joined the Mitsubishi Electric Corporation, where he has been engaged in the research and development of microwave and millimeter-wave monolithic integrated circuits (MMICs) and solid-state power amplifiers (SSPAs). Mr. Mori is a member of the IEEE.

Kenichiro Choumei was born in Japan, on July 15, 1968. He received the B.S. and M.S. degrees in electronic engineering from Doshisha University, Kyoto, Japan, in 1992 and 1994, respectively. He joined the Optoelectronic and Microwave Devices Laboratory, Mitsubishi Electric Corporation, Itami, Japan, in 1994. Since then, he has been engaged in the research and development of GaAs devices for mobile communication systems. He is a Technical Staff Member in the High Frequency & Optical Semiconductor Division, Itami, Japan.

Teruyuki Shimura was born in Tokyo, Japan, in 1960. He received the B.S. degree in applied physics from the University of Tokyo in 1983. In 1983, he joined the LSI research and development laboratory, Mitsubishi Electric Corporation, Hyogo, Japan. He has been engaged in the research and development of GaAs devices including a GaAs low-noise MESFET and a GaAs SAGFET for digital integrated circuits. His present research interests center on AlGaAs/GaAs high power HBTs and their monolithic integrated circuits. Mr. Shimura is a member of the Japan Society of Applied Physics.


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Tadashi Takagi received his B.S. degree in physics from Tokyo Institute of Technology and the Ph.D. degree in electronic engineering from Shizuoka University, in 1973 and 1995, respectively. He joined the Mitsubishi Electric Corporation in 1973, where he has been engaged in the research and development of microwave and millimeter-wave monolithic integrated circuits (MMICs) and solid state power amplifiers (SSPAs). Dr. Takagi is a member of the IEEE.

Yukio Ikeda received his B.S. and M.E. degrees in electrical engineering from Keio University in 1979 and 1981, respectively. In 1981, he joined the Mitsubishi Electric Corporation, where he has been engaged in the research and development of microwave and millimeter-wave monolithic integrated circuits (MMICs) and solid-state power amplifiers (SSPAs). Mr. Ikeda is a member of the IEEE.

Osami Ishida was born in Shizuoka, Japan, on August 25, 1948. He received the B.S. and M.S. degrees in electronic engineering, and Dr.Eng. degree from the Shizuoka University, Hamamatsu, Japan, in 1971, 1973, and 1992, respectively. In 1973, he joined Mitsubishi Electric Corporation, where he has been engaged in research and development of microwave circuit technologies in antenna feeds for satellite communication and phased array radars, and in devices for mobile communication. He is currently the Manager in the Microwave Electronics Department at the Information Technology R & D Center, Kamakura, Japan. Dr. Ishida is a member of the Institute of Electrical and Electronics Engineering (IEEE).