Micromachined Millimetre-Wave Passive Components at 38 and 77 GHz

A precision micro-fabrication technique has been developed for millimetre-wave components of air-filled three-dimensional structures, such as rectangular coaxial lines or waveguides. The devices are formed by bonding several layers of micromachining defined slices with a thickness of a few hundred micrometres. The slices are thickphotoresist SU8 defined by photolithography, or silicon with a pattern defined by deep reactive ion etching; both are coated with gold by evaporation. The process is simple, and low-cost, as compared with conventional precision metal machining, but yields mm-wave components with good performance. The components are light weight and truly airfilled with no dielectric support. This paper reviews several of these micromachined mm-wave components at 38 and 77 GHz for communications and radar applications

The Design and Implementation of an Interdigitated Directional Coupler for Use in Microwave Mixers

The purpose of this thesis is to present a design for a balanced microwave mixer, operating in the X-band region(S-12 GHZ). The major emphasis of this work is on the coupling structure of the mixer. A 3-db interdigitated Lange coupler is designed, fabricated, and tested. The design obtained through numerical procedures is compared with that obtained with the TOUCHSTONE CAD package. A brief comparison between this coupler and other commonly used couplers is also presented. The diode circuitry of the mixer is discussed in detail, focusing mainly on the operation of the Schottky barrier diode, and finally a total layout of the mixer is discussed

A Review on the Structure, Application and Performance of the Passive Microstrip Devices

Microstrip technology is widely applied for design and implementation of several communication devices such as filters, diplexers, triplexers, multiplexers, couplers, etc. They are utilized to isolate desired signals and remove disturbing signals. The layout of filters, diplexers and triplexers have two, three and four ports, respectively. Passive filters have at least one pass channel, whereas diplexers have at least two channels to transmit the desired signal, and multiplexers have more passbands with more channels. In order to implement the passive components, first a cell called resonator must be designed. Creativity is very important in resonator design. It must be small and novel to get a better device than previous works. Therefore, the layout of previous reported resonator, used in passive microstrip devices, are studied in this work. There is a fierce competition among designers to miniaturize and increase the device performance. Hence we will investigate them, from the point of view size and performance, in this work. Some diplexers are multi-channel, which are more difficult to design than two-channel diplexers. Therefore, the multi-channel diplexers are less reported than the two-channel diplexers. The design of multiplexers is also very difficult because several channels must be controlled. Hence, they are less designed than filters and diplexers. The diplexers can be bandpass-bandpass or lowpass-bandpass, where the latest is less designed. This is because designing a lowpass-bandpass diplexer needs lowpass and bandpass resonators, whereas the design of a bandpass-bandpass diplexer needs only a bandpass resonator

Design and implementation of a non-contact microwave level measument instrument

Includes abstract.Includes bibliographical references (leaves 104-110).This dissertation describes the design and implementation of a microwave level measurement instrument for sensing the level of a substance inside a tank up to 10 m in height. A radar transceiver had to be designed to replace an acoustic sensor on an existing 4-20 mA loop powered ultrasonic instrument and had to be compatible with its on-board acoustic signal processing hardware. Specifications are developed for a pulsed radar architecture operating at 5.8 GHz with a bandwidth around 1 GHz and at a repetition frequency of 3.58 MHz

SERIES APERTURE COUPLED FED PHASED ARRAY ANTENNA

Phased arrays are employed in a wide range of civil and Military contexts, including RADAR, cellular communications, and satellite communications. However, modern phased-array antennas require complex design and bulky structure at high costs, hindering their implementation in many applications. The critical aspect of a phased array design lies in power splitting with a proper phase to each radiating element. Conventional power splitters such as quarter-wavelength or Wilkinson power splitters suffer problems associated with complex array network and high power dissipation. Furthermore, popular phase shifters such as MEMS switch, ferrite-based or PIN diode have drawbacks of low power-handling capability, expensive packaging, and difficult fabrication process. The presented work introduces an innovative approach to phased array antenna design, centered around a quadrature hybrid phase shifter and a novel feeding technique known as series aperture coupling. The essence of this design lies in its ability to harness electronic components that are not only cost-effective but also highly efficient, serving the same purpose as existing methods while significantly reducing overall expenses. Unlike conventional methods that rely on control mechanisms such as magnetic fields to alter the properties of specific materials like ferrites, thereby achieving phase shifting of the signal, this invention takes a different route. It leverages signal reflection through the utilization of variable capacitors to attain the same goal. This approach offers a more accessible and economical means of achieving the desired phase shifts in the signal. One of the key innovations lies in the implementation of a cascade phase shifter connection. This configuration proves instrumental in establishing a highly responsive phased array structure. By linking phase shifters in a cascade arrangement, it becomes possible to fine-tune the phase relationships of individual radiating elements, resulting in a highly adaptable and sensitive phased array. Furthermore, the series aperture coupled feeding method presents a unique advantage in terms of optimizing the available material space. This approach streamlines the design process, minimizing the need for external devices and bulky materials. The result is an antenna design that operates with enhanced efficiency and reduced interference from external components. Additionally, the use of power splitters based on quadrature hybrids between each 1-D subarray further streamlines the design and enhances the ease of expanding the array system. In summary, this work represents a significant departure from traditional phased array antenna design, offering a more cost-effective, versatile, and streamlined solution. By harnessing the capabilities of quadrature hybrid coupler, variable capacitors, and cascade phase shifter configurations, the proposed design holds the potential to advance the field of phased array antennas, making them more accessible and efficient for a range of applications

AlGaN/GaN-HEMT power amplifiers with optimized power-added efficiency for X-band applications

This work has arisen out of the strong demand for a superior power-added efficiency (PAE) of AlGaN/GaN high electron mobility transistor (HEMT) high-power amplifiers (HPAs) that are part of any advanced wireless multifunctional RF-system with limited prime energy. Different concepts and approaches on device and design level for PAE improvements are analyzed, e.g. structural and layout changes of the GaN transistor and advanced circuit design techniques for PAE improvements of GaN HEMT HPAs