Research Of Microwave And Millimeter Wave Frequency Synthesizers And Related Components

With the rapid advances of modern electronic science and technology and increasing crowdedness in use of low frequency spectrum,operation frequencies of communication and radar systems are moving to higher and higher frequency bands.In comparisons with microwave,millimeter waves have wider bandwidths,narrower radiation beam-width and higher resolution.As the heart of a communication system or a radar system,frequency synthesizer plays a critical role on performance,size,and power consumption of the systems.Therefore,a high-performance millimeter wave frequency synthesizer(MWFS)of compact size,low cost,and low power consumption is very much desired and of high practical value.Slow frequency hopping,low frequency resolution and bulky size are the main issues associated with a millimeter wave frequency synthesizer.In thesis,by conducting theoretical analyses,simulations and experiments,the above issues are addressed,the properties of a millimeter-wave synthesizer including frequency tunability,frequency resolution,spurs,harmonics and size miniaturization are analyzed,and the fundamental theory and key techniques of frequency synthesis are presented in a systematic way.A high-performance millimeter wave frequency synthesizer with low spurs,low harmonics,agile tunability,high frequency resolution and compact size is then proposed.At the same time,bandpass passive filters used in the millimeter wave frequency synthesizers are researched and two kinds of them are developed with high performance and small size.More specifically,the contributions of this thesis are summarized as follows:1.A continuous millimeter-wave frequency synthesis scheme with agile frequency tunability and high frequency resolution is proposed.It overcomes the problems of inadequate frequency resolution and slow frequency hopping time that exist in the current millimeter wave frequency synthesizer.It is based on direct digital frequency synthesizer(DDS).With it,a Ka-band continuous wave frequency synthesizer is developed: it has the bandwidth of 1GHz,good frequency agility,high frequency resolution,low spurs and low harmonics.It has the output power of more than 20 dBm,the phase noise of less than-85dBc/Hz@lkHz,frequency resolution of 1.87 Hz,suppression of spurs and harmonics over 45 dB,and minimum frequency hopping time of 4ns.2.A continuous millimeter wave frequency synthesis scheme with extended bandwidth based on DDS technology is proposed.It solves the issues of slow frequency hopping speed and low frequency resolution in a millimeter wave frequency synthesizer that is often caused by the phase-lock-loop(PLL).By applying the bandwidthexpansion technique with the use of DDS,without sacrificing the phase noise performance,a Ka-band continuous wave frequency synthesizer is proposed with agile frequency tunability,high frequency resolution,low spurs,low harmonics,and compact size.It has the output power of 20 d Bm,the phase noise of less than-80dBc/Hz@lkHz,the frequency resolution of 1.87 Hz,the suppression of spurs and harmonics over 45 dB,and minimum frequency hopping time of 4ns.3.A methodology to design compact high-performance microstrip bandpass filters based on folded stepped-impedance resonator(FSIR)is proposed.It reduces spurs and harmonics in a millimeter wave frequency synthesizer.It is built on the modification of FSIR and it has about half the size of the conventional stepped-impedance resonator(SIR).As a result,the microstrip filters are integrated with the modified FSIR and they achieve over 95% reduction in size in comparison with of the conventional filters.Further improvement is carried out to modify FSIR with the stepped-impedance theory,and the resultant compact microstrip filters have better performance and achieve over 99% reduction in size in comparison with of the conventional microstrip filters.The sizes of these filters are comparable with those of the surface acoustic wave(SAW)filters.Therefore,these filters can also be used to replace the SAW filters in practical applications.4.A methodology to design microstrip filters with compact transverse size,high selectivity and wide stopband is proposed.By utilizing the source-load coupled topology,two transmission zeros can be respectively generated at the upper and lower ends of the passband.By employing the open-stub-loaded transmission line,an extra transmission zero can be introduced into the stopband of the filter.By incorporating the two structures,a source-load coupled structure combined with the open-stub line is developed.The combined structure is then incorporated with a U-shape microstrip resonator and a T-shape dual-mode SIR respectively;they lead to a single-end filter,a differential filter and a single-end wideband filter.These filters all have compact transverse sizes,high selectivity and very good third-order harmonic suppressions.Their sizes are reduced by 83% as compared with the conventional ones and have the third-order harmonic suppression of more than 20 dB.