Figure 3 Measured insertion loss of waveguide E-plane resonator at 36.80 GHz

Figure 4 Photograph of the waveguide E-plane resonator

be easily realized with a single metal insert within a rectangular waveguide. Measured frequency responses of a rectangular waveguide E-plane bandpass filter which used quarterwavelength metallic septa shows 30 dB rejection at 36 GHz. The central resonator was resonant at 36.8 GHz. This kind of resonator is expected to find application, particularly, in the millimeter-wave, submillimeter-wave, and terahertz range circuits, e.g., in low-phase-noise oscillators and highly selective filters, diplexers and multiplexers, frequency-selective surfaces, and antennas.

REFERENCES

1.D. Budimir, Generalized filter design by computer optimization, Artech House, Norwood, MA, 1998.

2.H. Contopanagos, N.G. Alexopoulos, and E. Yablonvitch, High-Q rectangular cavities and waveguide filters using periodic metalodielectric slabs, IEEE MTT-S Dig, 1998, pp. 1539]1542.

3.F.R. Yang, Y. Qian, and T. Itoh, A novel high-Q image guide resonator using band-gap structures, IEEE MTT-S Dig, 1998, pp. 1803]1806.

4.T. Yoneyama and S. Nishida, Nonradiative dielectric waveguide for millimeter-wave integrated circuits, IEEE Trans Microwave Theory Tech MTT-29 1981., 1188]1192.

5.G.J. Cunningham, P.A. Blenkinsop, and J.H. Palmer, Microstrip end-coupled filter design at mm-wave frequencies, European Microwave Conf, Sept. 1989, pp. 1210]1213.

6.R.B. Bricout, R.G. Bosiso, and L. Kaliouby, Hi-Q transmission lines for millimetre-wave space applications, ESArESTEC Workshop, 1990, pp. 267]269.

7.D.G. Swanson, Jr., An HTS end-coupled CPW filter at 35 GHz, IEEE MTT-S Dig, 1994, pp. 199]202.

8.D. Budimir and C.W. Turner, Novel planar filter structures for millimetre-wave applications, Asia Pacific Microwave ConfAMPC’98., Yokohama, Japan, Dec. 1998.

9.D. Budimir and C.W. Turner, Extremely narrow band microstrip bandpass filters using periodic couplers, Microwave Opt Technol Lett accepted..

10.D. Budimir, EPFIL}Waveguide E-plane filter design, Software and User’s Manual, Artech House, Norwood, MA, 1999 accepted..

Q 1999 John Wiley & Sons, Inc.

CCC 0895-2477r99

CAPACITANCE – VOLTAGE CHARACTERISTICS AND CUTOFF FREQUENCY OF PSEUDOMORPHIC

(AlGaAs/InGaAs) MODULATION-DOPED FIELD-EFFECT TRANSISTOR FOR MICROWAVE AND HIGH-SPEED CIRCUIT APPLICATIONS

Anju Agrawal,1 Anisha Goswami,2 Sujata Sen,2 and R. S. Gupta2

1Department of Electronics Acharya Narendra Dev College Kalkaji, New Delhi 110 019, India

2Semiconductor Devices Research Laboratory Department of Electronic Science

University of Delhi, South Campus New Delhi 110 021, India

Recei¨ed 23 June 1999

ABSTRACT: A two-dimensional analytical model for the capacitance]¨oltage characteristics of a pseudomorphic AlGaAsr InGaAs modulation-doped field-effect transistor is de¨eloped using charge-control analysis for its microwa¨e frequency applications. The model includes the effect of ¨arious fringing field capacitances, and a cutoff frequency of 94.8 GHz is obtained for an L s 0.25 mm de¨ice. The effect of traps has been included, which decreases the cutoff fre- quency. The results so obtained are compared with experimental data, and show excellent agreement, thereby pro¨ing the ¨alidity of the model.

Q 1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 312]318, 1999.

Key words: pseudomorphic MODFET; gate]source capacitance; gate]drain capacitance; cutoff frequency

INTRODUCTION

The high-electron-mobility transistor HEMT. is a very promising device for low-noise microwave and high-speed applications. Due to the potential significance of HEMTs in a multitude of applications, their operation and optimization have been the subject of intense study w1]3x ever since their initial conception. The superior performance of HEMTs over comparable conventional MESFET structures has been demonstrated in both analog w4x and digital w5x integrated circuits. The inherent performance advantages of the HEMT stem from its use for modulation doping. In this way, the device, without sacrificing speed, delivers significant current by spatially separating the donor atoms from the current-car- rying channel. Electrons transfer from the highly doped wide

312 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 23, No. 5, December 5 1999