Self-Matched Method And Application Research Of Negative Group Delay Microwave Circuits

As an important technical index to describe the linearity of the phase-frequency characteristic,the group delay has drawn wide attention in the modern high-quality and broadband wireless communication systems.The distortion of the group delay will lead to the inter-symbol interference which will cause a series of problems such as rising bit error rate,worsening the signal-to-noise ratio and so on.The traditional technique to equalize the group delay will result in an increase of the total delay of the system.As a new method to compensate for the group delay,the negative group delay(NGD)circuit has shown strong competitiveness in satisfying the low delay requirements of 5G and realizing the high-quality and broadband wireless communication systems.Meanwhile,the NGD circuit has shown anenormous application potentiality in many fields such as the performance improvement of the microwave devices,the analysis of the signal integrity,the applications in the antenna array and so on.Therefore,the NGD microwave circuit has great research significances and applicable values.However,the traditional NGD microwave circuits are based on the single-terminal reflection type RLC resonator or the series two-terminal paralleled RLC resonator,which needs the extra input and output port matching circuits to apply in the microwave band.To solve this question,the self-matched method of the NGD microwave circuit is researched in this dissertation.The dual-band and tunable NGD microwave circuits with self-matched characteristic and the novel linear phase bandpass filter based on NGD microwave circuit are studied and designed.The main innovation achievements are as follows:(1)A miniaturized self-matched NGD microwave circuit based on the modified RLC resonantor was presented.The proposed NGD microwave circuit realized the input and output ports impedance matching by loading a paralleled branch composed of the series resistor and inductor on the series RLC paralleled resonator.The lumped parameter elements are not suitable to apply in the microwave band.So the lumped inductors and capacitors were replaced by the distributed parameter transmission lines to achieve the self-matched NGD microwave circuit.In addition,a transmission-line type self-matched NGD microwave circuit was presented.The proposed transmission-line type self-matched NGD circuit was composed of an open-circuited coupled line,a high-impedance short-circuited transmission line,the chip resistors and those connecting lines.The transmission-line type NGD circuit could be directly analyzed and designed by the circuit theory of the distributed parameters that avoided the approximate errors during the lumped parameter elements transformed into the distributed parameter transmission lines.The tested results showed that the proposed NGD circuits realized the self-matched characteristic without the extra matching circuits.(2)A compact self-matched dual-band NGD microwave circuit was presented.The proposed dual-band NGD circuit had the same group delay responses in the two operating bands.Theoretically,the proposed dual-band'NGD circuit could realize an arbitrary frequency ratio.Two dual-band NGD circuits with different frequency ratios were designed and realized.The first one had a frequency ratio of 2.06 that obtained the dual-band NGD characteristic(The NGD time of-1.19ns were both obtained at the frequencies of 0.667GHz and 1.377GHz.And the return losses were greater than 24dB).The second one had a frequency ratio of 1.16 that obtained the broadband NGD characteristic(The GD was-1.58ns±0.13ns within the frequency range of 0.903?1.101GHz and the return losses were better than 23dB).The measured results had a good consistency with the theoretical designs and the self-matched characteristic of the dual-band NGD microwave circuit was realized.(3)A self-matched NGD microwave circuit with tunable operating frequency and group delay was presented.The electronically tunable operating frequency and group delay were implemented by utilizing the variable resistor and the varactors.At the same time,the varactors were utilized to realize the impedance matching of the input and output ports.A tunable NGD microwave circuit with a group delay tuning range of-1?-10ns and a frequency tuning range of 0.8?1.3GHz was designed and realized.In the whole process of tuning the operating frequency and group delay,the return losses of the input and output ports were better than 30dB,which realized the self-matched characteristic of the tunable NGD microwave circuit.(4)A design approach of the external-equalied linear phase bandpass filter based on the NGD microwave circuit was presented.The NGD circuit units were added at the input and output ports of the traditional bandpass filter,which realized the low group delay fluctuation in the whole passband.The tested results had a good consistency with the theoretical designs.Besides,a design approach of the self-equalized linear phase bandpass filter based on the novel admittance inverter was presented.The novel admittance inverter was utilized to realize the self-equalization of the group delay which could realize the low group delay fluctuation in the whole passband.To verify the validity of this design method,the proposed filter based on the novel admittance inverter was tested and compared with the bandpass filter based on the traditional admittance inverter.The measured results showed that the group delay fluctuation of the proposed filter based on the novel admittance inverter was reduced 50%of that of the bandpass filter based on the traditional admittance inverter,which realized the low group delay fluctuation in the whole passband.And the novel filter kept the same frequency selectivity compared to the traditional bandpass filter.