Research On Miniature Millimeter-wave Frequency Synthesis Technology

Frequency synthesizer is known as the heart of the electronic system, its performance has a direct impact on the overall system performance. With the rapid development of millimeter-wave theory, performances of device, new packaging technology and manufacturing process of circuits, the performance and integration of frequency synthesizer are constantly improved. On the other hand, with the urgent demanding in millimeter-wave wireless communications, radar, guidance and testing system, the demands on improving the performance of the frequency synthesizer is ever-increasing. Therefore, the research on the millimeter-wave frequency synthesis is of great significance and urgency, and it is also the focus of domestic and foreign researchers.The main content of this thesis include five aspects as follow:1. Based on the full planar integration circuit technology, the method of frequency synthesis in W-band is proposed, which adopts the frequency-extending scheme. The study begins with the analysis and experimental validation of theoretical and technical features of several frequency synthesis and phase-coherent frequency synthesis schemes. The frequency-extending scheme is a multi-stage cascaded multiplier chain, which can realize the W-band frequency synthesizer with properties of miniature, planar structure, low phase noise, low spurious level and wide bandwidth. This scheme solved the problem of the traditional and frequently-used method——phase locked waveguide Gunn oscillator which is with low integration, low stability and narrow bandwidth. This frequency-extending scheme provides a better way for the synthesis of the W-band frequency synthesizer.2. There are several schemes about frequency extending in W-band that are proposed in the section 3. The frequency triplers and doubler in multiplier-chain are studied in detail. The MMIC, balanced diode tripler and balanced diode tripler with self-bias circuit are analyzed, designed and fabricated, the measured results show that the balanced diode tripler with self-bias circuit has the lowest conversion loss in the three types tripler. A planar single diode doubler in W-band is also analyzed, designed and fabricated, the measured performances agree well with the simulation. In section 3, the W-band frequency synthesizer is realized by×4×3 multiplying the microwave source. and the W-band full phase coherent frequency synthesizer is realized by×2×2×2 scheme. These results validate the way of frequency extending scheme for W-band frequency synthesis.3. In the application of the W-band frequency synthesizer, a prototype of miniature 3mm radar front-end is proposed. A five ports rat-race ring with a multi-line tight-coupled DC/IF blocking and filtering structure is used as the basic unit of the W-band mixer to improve the sensitivity of the receiver. The measured results show that the novel mixer has a wider bandwidth, lower conversion loss and better VSWR when compared to the traditional mixer. Two types of the W-band SPDTs and detector are studied to protect the receiver and detecting the RF signal. A scheme of multi-stage inject lock pulse IMPATT amplifier is proposed to achieve 22W RF power in W-band, and it is realized and used in the prototype of the 3mm guidance radar successfully.4. LTCC has become one of the hot spots and trends as a high-density integration and packaging technology in microwave and millimeter-wave band. The idea of using LTCC to realize the millimeter wave frequency synthesizer is proposed in this thesis first. Based on the process characteristics and key technical problem of LTCC, study on the LTCC multilayer vertical via transition, the LTCC multilayer couple line transition, interconnection between LTCC sub-modules, and transitions between different transmission lines is carried out. A DC to 40GHz LTCC vertical via transition is proposed and validated. Three different CBCPW to waveguide transition are proposed, fabricated and measured. A new via-gate structure is designed for EM shielding, which reduced lots of ground via compared to the traditional structure. On the synthesis and design of the LTCC filter, detailed study is carried out in the last part of the section 4, and a LTCC filter is designed and measured as an example. These results provide a favorable of technical support on the combination of new packaging technology and millimeter-wave circuit.5. The idea of design a millimeter wave LTCC frequency synthesizer is proposed in this thesis. Firstly, the scheme of the microwave LTCC frequency synthesizer is researched and verified. Secondly, the Ka-band LTCC frequency synthesizer based on the mixing+PLL+multiplying scheme is researched, fabricated and measured. In the synthesizer, two microwave filters are buried in the multi-layer substrate. Power lines, signal lines and digital lines are in different layers. The measured performances of the synthesizer agree well with the simulation. At last, the Ka-band LTCC frequency synthesizer is redesigned for miniature, its size and weight are reduced by 56%. As far as I know, this is the first LTCC frequency synthesizers in Ka-band.