Microwave devices, components

It has a high melting point of 240°C (15, p. 219). Due to the high melting point and good temperature stability, TPX is used for au-toclavable medical equipment, components in microwave devices, and as cookware. 

Figure 29.9 shows a comparison between the components of a rudimentary EPR spectrometer and the corresponding elements of a more familiar apparatus for visible spectrometry. In EPR, the source of excitation radiation is a microwave device called a klystron. The microwaves would disperse in free space and must therefore be conducted to the sample by waveguide or coaxial cable. The sample, contained in the sample tube, is held in a microwave cavity between the poles of a magnet. The detector is usually a diode that produces a dc output propor-... 

The discussion so far has been concerned with dielectrics in steady electric fields more commonly they are in fields that change with time, usually sinusoidally. This is clearly the case for capacitors in most ordinary circuit applications, but there are less obvious instances. For example, because electromagnetic waves have an electric field component it would be the case for dielectric resonators in microwave devices and also for fight passing through a transparent material. Fortunately, no matter how the field may vary with time, the variation can be... 

To understand the principle of operation of important non-reciprocal (see below) microwave devices, consider what occurs when a plane-polarized microwave is propagated through a ferrite in the direction of a saturating field Ht. The wave can be resolved into two components of equal amplitude but circularly polarized in opposite senses, i.e. into a right-polarized and a left-polarized component. These two components interact very differently with the material, leading to different complex relative permeabilities H r+ = n r+ - j/r" i and /r - = /T- — j/r"-, as shown in Fig. 9.40. Because of the... 

J.A. Seeger, Microwave Theory, Components and Devices, Prentice-Hall, New Jersey, 1986. 

With the progress in microwave telecommunication technology, dielectric materials have come to play an important role in the miniaturization and compactness of microwave passive components. The dielectric materials available for micro-wave devices are required to have predictable properties with respect to a high dielectric constant (K), high quality factor (Qf), and small temperature coefficient of resonant frequency (TCP). Numerous microwave dielectric materials have been prepared and investigated for their microwave dielectric properties and for satisfying these requirements. In particular, complex perovskite compounds A(B,B )03... 

Both multi-mode and focused microwave devices consist of four major components,... 

Ceramic interconnect technologies are capable of integrating various components, such as passive components, RF/microwave devices, ICs, and transmission lines on and/or in a ceramic substrate, forming electronic modules that provide certain functions. Recently, millions of such functional modules have been commercialized in the automotive industry, consumer... 

Telecommunication industry today requires high volume efficiency without the degradation of electrical performance of the devices. In order to reduce the size of microwave devices in communication systems, the dielectric component must also be miniaturized. The... 

Polysulfones also offer desirable properties for cookware appHcations, eg, microwave transparency and environmental resistance to most common detergents. Resistance to various sterilizing media (eg, steam, disinfectants, and gamma radiation) makes polysulfones the resin family of choice for many medical devices. Uses in the electrical and electronic industry include printed circuit boards, circuit breaker components, connectors, sockets, and business machine parts, to mention a few. The good clarity of PSF makes it attractive for food service and food processing uses. Examples of appHcations in this area include coffee decanters and automated dairy processing components. 

However, the key components to provide the power generating functionality are based on semiconductors. Novel materials and transistor structures based on InP, SiGe and GaN represent an area of extensive R D activities with emphasis on high power, low noise and high operation frequencies. The performance of a real device such as the phase noise of a microwave oscillator depends both on the noise properties of the transistor and on the loss tangent of the oxide material which forms the stabilising resonator. Therefore, material and device related R D activities both on semiconductors and on oxides are essential to open new horizons for microwave communication and sensor applications. 

Major polymer applications microwave cookware, fiber optic connectors, capsules for electronic devices, watches, cameras, audiovisual equipment, under-bonnet automotive components, aerospace structures... 

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