The problem of designing a digital frontend (DFE) was considered which can dynamically access or sense dual bands in any radio frequency (RF) regions without requiring hardware changes. In particular, second-order ban...The problem of designing a digital frontend (DFE) was considered which can dynamically access or sense dual bands in any radio frequency (RF) regions without requiring hardware changes. In particular, second-order bandpass sampling (BPS) as a technique that enables to realize the multiband reception function was discussed. In a second-order BPS system, digital reconstruction filters were utilized to eliminate the interferences generated while down converting arbitrarily positioned RF-band signals by using the direct digitization method. However, the inaccuracy in the phase shift or the amplitude mismatch between the two sample streams may cause insufficient rejection of interference. Practical problems were studied, such as performance degradation in signal-to-interference ratio (SIR) and compensation methods to overcome them. In order to demonstrate the second- order BPS as a flexible DFE suitable for software-defined radio (SDR) or cognitive radio (CR), a DFE testbed with a reconfigurable structure was implemented. Moreover, with a view to further demonstrate the proposed compensation algorithms, experimental results show that dual bands are received simultaneously.展开更多
In this paper, the variational method combined with Green's function is used to analyze the characteristics of suspended, stripline. The result is in good agreement with references. The design of mm-wave end-coupl...In this paper, the variational method combined with Green's function is used to analyze the characteristics of suspended, stripline. The result is in good agreement with references. The design of mm-wave end-coupled bandpass filter with suspended substrate is discussed. The computer programs for design of suspended stripline and bandpass filter are established.展开更多
A miniaturized periodic element for constructing bandpass frequency selective surface(FSS)independent of incident angles and polarizations is presented.An interdigital resonator(IR)with one extending finger to connect...A miniaturized periodic element for constructing bandpass frequency selective surface(FSS)independent of incident angles and polarizations is presented.An interdigital resonator(IR)with one extending finger to connect the two separate parts of the interdigital capacitor is explored to achieve parallel resonance.The equivalent circuit model(ECM)and electric field distributions are introduced to explain frequency performance of FSS.The whole structure has only one layer and possesses a low profile(a thickness of 0.0015λ,where λ represents the resonant wavelength in free space)as well as a small size(0.03λ×0.03λ).This FSS performs as a spatial bandpass filter which exhibits a great angular stability with incident angles ranging from 0° to 80° for both transverse electric(TE)and transverse magnetic(TM)polarizations.As an example,a prototype of one proposed FSS is fabricated and tested.The measured results show a good angular stability.展开更多
为解决软件无线电(Software Defined Radio,SDR)中采样后信号混叠问题,提出了一种改进的相位调整滤波算法。依托具备可调时间延迟的二阶射频带通采样前端,设计了一种支持多分点分段滤波的抗混叠滤波器,可以根据实际需求灵活设置多个频...为解决软件无线电(Software Defined Radio,SDR)中采样后信号混叠问题,提出了一种改进的相位调整滤波算法。依托具备可调时间延迟的二阶射频带通采样前端,设计了一种支持多分点分段滤波的抗混叠滤波器,可以根据实际需求灵活设置多个频率分点,从而实现针对不同频段的精确滤波。通过在MATLAB SIMULINK中进行仿真验证,该方法相比同类方法的滤波器抑制效果更佳,达到38 dB以上,并能有效滤除所需信号而不影响其他信号的完整性,简化了接收前端,具备较强的灵活性和适应性,能够更好地支持未来的通信技术和高密度通信连接。展开更多
基金Research financially supported by Changwon National University in 2009-2010the Second Stage of Brain Korea 21 Projects
文摘The problem of designing a digital frontend (DFE) was considered which can dynamically access or sense dual bands in any radio frequency (RF) regions without requiring hardware changes. In particular, second-order bandpass sampling (BPS) as a technique that enables to realize the multiband reception function was discussed. In a second-order BPS system, digital reconstruction filters were utilized to eliminate the interferences generated while down converting arbitrarily positioned RF-band signals by using the direct digitization method. However, the inaccuracy in the phase shift or the amplitude mismatch between the two sample streams may cause insufficient rejection of interference. Practical problems were studied, such as performance degradation in signal-to-interference ratio (SIR) and compensation methods to overcome them. In order to demonstrate the second- order BPS as a flexible DFE suitable for software-defined radio (SDR) or cognitive radio (CR), a DFE testbed with a reconfigurable structure was implemented. Moreover, with a view to further demonstrate the proposed compensation algorithms, experimental results show that dual bands are received simultaneously.
文摘In this paper, the variational method combined with Green's function is used to analyze the characteristics of suspended, stripline. The result is in good agreement with references. The design of mm-wave end-coupled bandpass filter with suspended substrate is discussed. The computer programs for design of suspended stripline and bandpass filter are established.
基金supported by the Aeronautical Science Foundation of China(2017ZF37005)the National Natural Science Foundation of China(62001389).
文摘A miniaturized periodic element for constructing bandpass frequency selective surface(FSS)independent of incident angles and polarizations is presented.An interdigital resonator(IR)with one extending finger to connect the two separate parts of the interdigital capacitor is explored to achieve parallel resonance.The equivalent circuit model(ECM)and electric field distributions are introduced to explain frequency performance of FSS.The whole structure has only one layer and possesses a low profile(a thickness of 0.0015λ,where λ represents the resonant wavelength in free space)as well as a small size(0.03λ×0.03λ).This FSS performs as a spatial bandpass filter which exhibits a great angular stability with incident angles ranging from 0° to 80° for both transverse electric(TE)and transverse magnetic(TM)polarizations.As an example,a prototype of one proposed FSS is fabricated and tested.The measured results show a good angular stability.
文摘为解决软件无线电(Software Defined Radio,SDR)中采样后信号混叠问题,提出了一种改进的相位调整滤波算法。依托具备可调时间延迟的二阶射频带通采样前端,设计了一种支持多分点分段滤波的抗混叠滤波器,可以根据实际需求灵活设置多个频率分点,从而实现针对不同频段的精确滤波。通过在MATLAB SIMULINK中进行仿真验证,该方法相比同类方法的滤波器抑制效果更佳,达到38 dB以上,并能有效滤除所需信号而不影响其他信号的完整性,简化了接收前端,具备较强的灵活性和适应性,能够更好地支持未来的通信技术和高密度通信连接。
