Millimeter-Wave Microstrip to Waveguide Transition for use in Gap-Waveguide-Integrated Grid Amplifiers and Antenna Arrays

Scriptie/masterproef: Master


To realize next generation mm-wave wireless systems it is vitally important to utilize cost effective manufacturing technologies and to develop low-loss waveguides and transmission lines. Furthermore, being able to interface system components through contactless transitions is another key objective. In fact, recently, optical connections between chips through fibers is being researched heavily in the photonics science field, while the quasi-optical connection as proposed in this MSc thesis between chips through waveguides presents a similar breakthrough, albeit in the mm-wave range. The proposed contactless connection between a waveguide and chip obviates the need to use RF bond wires. Furthermore, the proposed solution is also compatible with the gap waveguide technology enabling the resonance-free electromagnetic packaging of the entire RF front end.
There are numerous challenges to overcome to realize future mm-wave antenna systems. Standard waveguide components are rather low loss but are manufactured in split blocks which may lead to power leakage. Mechanical assembly of the two split blocks requires a very good electrical contact as well as precise alignment of the two blocks to achieve good electrical performance. Furthermore, the physical dimensions of the waveguide components decrease as the frequency of operation increases. This renders the manufacturing of conventional waveguide components more costly and time consuming, particularly at mm-wave frequencies.
The gap waveguide structure has the advantage of reducing the manufacturing cost and time, because the gap waveguide structure can be realized without requiring any metal contact between the upper and the lower metal surfaces of the structure. Also, the Perfect Magnetic Conductor (PMC) condition realized by the lid of nails, parallel to a PEC surface, has the ability of suppressing unwanted parallel-plate modes between the two metal blocks and allows for the resonance-free packaging of RF electronics, thereby high isolation between the RF components can be achieved.
At the same time a low-loss transition between the gap waveguide components and the active ICs, such as Monolithic Microwave/Millimeter Integrated circuits (MMIC), is necessary in order to integrate active components with passive waveguide components together with antennas in a single module. It is common practice to establish a connection between a transmission line and a chip through RF bondwiring. However, the large impedance mismatch between the inductive bond wire and the MMIC requires a matching capacitor. But impedance matching can only be achieved over a certain bandwidth, depending on the Q-factor of the LC circuit. Furthermore, the matching network takes up the space, and may excite cavity modes when packaged resulting in device oscillations and cross talk effects. It is therefore the objective of this thesis to provide a novel, low-loss and broadband contactless microstrip line to groove gap waveguide transition.
An MMIC-to-waveguide transition has been designed at W-band and in such a way that it can be integrated easily in a groove gap waveguide structure, for example by using a pick-and-place technique. Both the PCB and the gap waveguide were designed and manufactured. Tolerances are allowed up to ± 10 microns. The simulation results of a back-to-back transition are excellent; the S11 is below -21 dB, while S21 is better than -0.35 dB over the entire W-band (75-110 GHz). Unfortunately the experimental validation of the transition is not as expected. A thorough error analysis revealed that the dimensions of the PCB were not within the tolerances as specified by the manufacturer, which is the main reason for the performance degradation. Future steps are recommended to resolve these issues.
Datum Prijs17 mrt 2016
BegeleiderRob Maaskant (Afstudeerdocent 1) & A. Uz Zaman (Afstudeerdocent 1)

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Millimeter-Wave Microstrip to Waveguide Transition for use in Gap-Waveguide-Integrated Grid Amplifiers and Antenna Arrays
Aljarosha, A. (Auteur). 17 mrt 2016

Scriptie/masterproef: Master