8/2/2019 Rectangular Dielectric Resonator

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series in eqn. 14 is asymptotically similar toS= X 2njcoe0acoskynh sm 4>n c o s (15)

For small gaps, when ng/B

8/2/2019 Rectangular Dielectric Resonator

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T M to 2 but also TE to >'. The a djustment consists of treatingthe resonator as a dielectric body inside rectangular magnetic-wall waveguide; the waveguide operates above cutoff insidethe dielectric boundaries and below cutoff outside. Resonantfrequencies found using this model were in better agreementwith experimental data. A typical measured impedance curveis shown in Fig. 2. The predicted res onan t frequency using theadjusted first-order model is 302 GHz .

20 0

100

probe length:1-50cm(1)1 27cm(2)1O2cm(3)076cm (4)

0 3 3 3-9 4-5frequency, GHz

5-1

Fig. 3 Measured impedance with different probe lengthsa = b = c = 1-5 cm, sr = 8-9The significance of feed probe length is illustrated in Fig. 3,where the real part of the impedance is shown for differentprobe lengths. Monopole resonances, occurring at frequencieswhere the probe length is equal to a half-wavelength in thedielectric, appear to dominate when the cavity resonance isnear the same frequency. A resonance for the 1-50 cm probeoccurs at 3-35 GH z; the peak shown at 3-6 GHz apparentlyrepresents this. (The higher-frequency experimental peak ispossibly due to the probe 'seeing' a permittivity slightly lowerthan that of the dielectric due to its position near the edge.)

For the 0-76 cm probe the monopole resonance is above 6-6G H z , and the peak shown at 4-2 GHz is due entirely to thecavity resonance.Radiated fields: Radiation patterns are found by consideringthe tangential electric fields on the resonator surfaces as equiv-alent current sources for the far-field radiation. This techniquegave good agreement between theory and experiment in thecylindrical case1 and is utilised once again.The calculated radiation patterns for square-base resonatorsof various heights are shown in Fig. 4. For maximum radi -ation normal to the ground plane, it is clear that the height ofthe resonator should be less than the width. However, from apractical viewpoint the height needs to be large enough sothat the probe length is greater than a quarter-wavelength inthe dielectric to avoid a highly reactive impedance. Iso-

0Fig. 4 Calculated radiation pa tterns for squ are-base resonator

c = 0-75 cm (outer), c = 2-25 cm (middle) and c = 4-50 cm (inner)for 90 and 0 curvese. = 8-9

tropicity in the 0-plane can also be improved by making th eantennas longer in the x-direction or by using higher dielectricconstants.Acknowledgment: This work was supported in part by USArmy Research Office Contract no. DAAG 20-82-K-0074.M . W. MCALLISTER 7th February 1983S. A. L O N GG . L. C O N W A YDepartment of Electrical EngineeringUniversity of HoustonHouston, TX 77004, USAReferences1 LONG, s. A., MCALLISTER, M. w., and SHEN, L. c : 'The cylindricalresonant dielectric cavity antenna', IEEE Trans., 1983, AP-312 YEE, H. Y.: 'Natu ral resonant frequencies of microwave dielectricresonators' , ibid., 1965, MTT-13, p. 2563 OKAYA, A., and BARASH, L. F. : Th e dielectric microwave resonator',Proc.IRE, 1962,50, p . 2081

0013-5194/83/060218-02S1.50/0

HIGH-EFFICIENCY Q-TO-W-BAND MICFREQUENCY DOUBLERIndexing terms: Integrated circuits, Microwave circuits andsystems, Frequency multipliersIntegrated-circuit phase-lock oscillators are extremely diffi-cult to develop above 60 GH z because of circuit losses. Aviable alternative is to use a frequency doubler. A Q-to-W-band (40 to 80 GHz) frequency doubler has been developedusing integrated-circuit suspended stripline. A conversionloss of less than 6-5 dB has been achieved with the outputfrequency at 80 GHz. This high efficiency was obtained by aninnovative input an d output matching circuit design. Th eadvantages over a waveguide doubler include largereductions in size, weight and cost.

Introduction: Integrated-circuit oscillators up to 60 GHz havebeen reported with a phase-lock capability to achieve highstability.1 However, the development of millimetre-wave MICphase-lock sources at W-band (80 GHz) and higher fre-quencies is extremely difficult because of circuit losses. The useof an efficient MIC doubler together with a Q-band MICoscillator provide a viable alternative for generating W-bandpower using integrated circuits.The frequency multiplier is a well proven frequency sourcewhich has been used in many system applications over anumber of years.2"7 Most of these multipliers are in wave-guide circuits. This letter reports a Q-to-W-band MIC doubler(40 to 80 GHz) using suspended stripline with a conversionloss of less than 6-5 dB. A multiple-section lowpass an dmatching circuit has been developed to achieve good inputmatching. The doubler can be combined with a Q-band MICY/. 80 GHzv/, output

varactor

lowpass matching^filter circuit 2 /Iinput

^ Duroid 5880' substrate

slidingshort

Fig. 1 Doubler circuit arrangementELECTRONICS LETTERS 17th March 1983 Vol. 19 No. 6 21 9