Study On Millimeter-wave Antenna Based On Low Temperature Co-fired Ceramic Technology

To meet the urgent requirement of radio frequency spectrum for the current information society, the operation frequency of modern communication, radar, guidance and navigation systems has exteneded from microwave band to millimeter-wave(MM-wave) band, futhuremore, their integration level becomes higher and higher, and their volume becomes smaller and smaller, which brings forward higher reqirements on the miniaturization of the antenna. Low temperature co-fired ceramic(LTCC), which has the advantage of multilayer structure, provides the technical support for the miniaturization and high performance of the MM-wave antenna. The MM-wave antenna fabricated with LTCC technology has the advantages of high integration level, compact size, light weight, low cost, wide application, etc. Nowadays LTCC antenna has become one of the research hotspot in the world. The specific research contents of this dissertation are concluded as follows: 1. Study on horn-like antenna based on LTCC technologyThe radiation mechanism of the aperture-coupled microstrip antenna in LTCC substrate is analyzed with transmission line model, and the effects of the design parameters on antenna’s performance are also presented. In order to overcome the microstrip antenna’s disadvantage of low gain, the method of using stacked rectangular rings to imitate the radiation of the horn antenna, and then improving its gain is proposed. A horn-like microstrip antenna is designed by using LTCC technology; stacked rectangular rings are added above the radiation patch in traditional microstrip antenna, which flare gradually to direct the antenna radiation at broadside direction as directors. The analysis shows the electromagnetic energy is enhanced at broadside direction and weakened at backside direction when the dimensions of the stacked rectangular rings are chosen appropriately, and then the gain of the antenna is improved. The measured result shows that the proposed antenna achieves a high gain of 8.1 dBi(including the loss of the feeding parts), which is about 3 dB higher than a single patch antenna without using stacked rectangular rings. This approach can improve the gain of the microstrip antenna without increasing its size obviously as compared with the traditional method of employing planar array antenna. 2. Study on multilayer parasitic patch antenna based on LTCC technologyTo overcome the shortcomings of the narrow band and low gain of microstrip antenna, the method of employing V-type or E-type parasitic patches to enhance its gain and bandwidth simultaneously is proposed. A V-type and an E-type parasitic patch antenna are designed with LTCC multilayer technology, respectively. In V-type parasitic patch antenna, flared stacked strips are employed as directors to guide the electromagnetic wave radiating toward broadside direction, thus improving antenna’s gain; at the same time, the stacked strips also form resonant cavities with the ground plane, the bandwidth of the antenna is broadened when the resonant frequency of these resonant cavities moves close to that of the main patch. In E-type parasitic patch antenna, four E-shaped patches are added above the four corners of the main patch, which not only play the role of directors to guide the antenna radiation toward broadside direction, but also increase the length of the current path which introduces a lower resonant frequency.When this frequency is close to the resonant frequency of the main patch, the bandwidth of the antenna will be widened. The measured results show that the V-type parasitic patch antenna achieves a relatively wide bandwidth of 16%, and high gain of 8 dBi at center frequency of 35 GHz; the E-type parasitic patch antenna obtains an extremely large bandwidth of 28%, an average gain over 6 dBi within the operation bandwidth and peak gain of 7.1 dBi at 36 GHz. By using these two antennas as elements, a two-element E-type parasitic patch array, a four-element V-type parasitic patch array and a eight-element beam scanning array with low sidelobes are designed, and all these arrarys achieve wide bandwidth and good radiation performance. 3. Study on multilayer quasi-Yagi antenna based on LTCC technologySince the traditional Yagi-Uda antenna has narrow bandwidth, also it is difficult to be integrated and applied in microwave and millimeter-wave frequencies, two methods of using multilayer directors to improve the performance of the quasi-Yagi antenna are propsed. A quasi-Yagi dipole antenna and quasi-Yagi loop antenna are designed at millimeter-wave band with LTCC multilayer technology, respectively. Due to the multilayer structure of the directors, these two quasi-Yagi antennas obtain better director effect than planar quasi-Yagi antenna, so higher gain can be achieved at end-fire direction. 4. Study on coplanar transition based on LTCC technologyTo overcome the shortcoming of introducing high transmission loss by using vertical transition due to the misalignment of the via holes, two novel coplanar transition structures are proposed to feed the antennas, then the reliability of the antenna design is improved. The horn-like microstrip antenna is fed by a microstrip-to-strip line transition, while the multilayer quasi-Yagi antenna is fed by a microstrip-to-CPS(coplanar strips) transition, which also plays the balun role. These two transitions have advantages of compact size, simple structure,wide operation bandwidth and low losses, which are very conducive to design compact and high performance antenna on LTCC substrate.