The DR is a type D88 provided by Morgan Electro Ceramics, and has a diameter (Dr) of 7.05 mm, length (L r) of 2.65 mm, frequency range of 5.462 GHz 200 MHz, temperature coefficient of t f = 5.4 ppm/C, dielectric constant of 88, and minimum unloaded Q of 6000. The results were also verified by the other software tools to optimize the reasonable coupling coefficient and Q factor of the DR at a 5.5-GHz operating frequency. The practical model of the DR coupled to a microstrip line inside a cavity enclosure with tuning screw was modeled using Dr. Rez Design Software,6 and Temax software were used. Several CAD tools such as the Advanced Design System (ADS) software from Agilent Technologies, 4 Computer Aided Resonator Design (CARD) 5 from Krell Engineering, Dr. The oscillation conditions and design of DRO were based on using two-port scattering parameters (S-parameters), then stability and the tenability of the DRO were examined, followed by the measurement of DRO characteristics. The present work starts with the activation of the dielectric resonator at its TE 01d resonance mode, and then the required instability region of the low-noise active device. Compared to the authors' previous work of developing a DRO for use at 3.65 GHz, 3 the effects of cavity walls on the prediction of resonance frequency are included here. The ultimate aim of the present work is to produce a free-running DRO operating at 5.5 GHz for WLAN applications. Recalling, the dielectric geometry and immediate surroundings, this resonance frequency can be calculated to an accuracy of about 1 percent or less. Furthermore, the discs are mostly operated in the transverse electromagnetic TE 01d mode, which represents the lowest possible resonance- mode frequency. Disc or puck-shaped DRs are most frequently used in microwave circuits since they can be easily manufactured. 2 Moreover, with the advent of temperature-stable materials, the DRO has emerged as a high quality factor (Qs of typically 9000 at 10 GHz), low loss, low-temperaturecoefficient (typically 6 ppm/C), and conveniently sized element for microwave integrated circuits (MICs) as well as in discrete circuit designs.ĭRs are available in different configurations. DROs represent an interesting solution as a quality oscillator for fixed frequency or narrowband tunable oscillators. Emphasis has been on low noise, small size, low cost, high efficiency, high temperature stability, and reliability. 1 With the rapid advancement of technology there has been an increasing need for better oscillator performance in support of more complex modulation formats. Microwave oscillators form an important part of many microwave systems, including in radar, communication links, navigation, and electronic warfare (EW) systems. But with the advanced development of improved dielectric materials, and the growth of requirements in cellular communications and satellite communications (satcom) systems, it is possible to produce DROs with excellent spectral purity. The performance of DROs has been limited for some time by the poor quality of ceramic materials. By applying a number of different CAE tools, including a harmonic-balance simulator as well as linear and nonlinear models, a prototype was developed with low phase noise, high output power, and low harmonic content. Computer- aided-engineering (CAE) tools can be invaluable in designing and optimizing the performance of these oscillators, as will be shown with the design for a prototype oscillator in support of wireless-localarea- network (WLAN) applications at 5.5 GHz. The dielectric resonator is placed λ/4 from the open end of the microstrip line the line length ℓ_| decreases rapidly with a change in frequency as small as a few hundredths of a percent, demonstrating the sharp selectivity that can be obtained with a dielectric resonator.Dielectric-resonator oscillators (DROs) provide low-noise signals for a variety of wireless and other applications. The DRO circuit is shown in Figure 13.12a.
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