In this article we introduce an exact backprojection filtered (BPF) type reconstruction algorithm for cone-beam scans based on Zou and Pan’s work. The algorithm can reconstruct images using only the projection data p...In this article we introduce an exact backprojection filtered (BPF) type reconstruction algorithm for cone-beam scans based on Zou and Pan’s work. The algorithm can reconstruct images using only the projection data passing through the parallel PI-line segments in reduced scans. Computer simulations and practical experiments are carried out to evaluate this algorithm. The BPF algorithm has a higher computational efficiency than the famous FDK algorithm. The BPF algorithm is evaluated using the practical CT projection data on a 450 keV X-ray CT system with a flat-panel detector (FPD). From the practical experiments, we get the spatial resolution of this CT system. The algo- rithm could achieve the spatial resolution of 2.4 lp/mm and satisfies the practical applications in industrial CT inspec- tion.展开更多
This paper presents a planar microstrip wideband dual mode Band-Pass Filter(BPF) from 2 GHz to 3.4 GHz with a notched band at 2.62 GHz.The dual mode band-pass filter consists of a ring resonator with two quarter-wavel...This paper presents a planar microstrip wideband dual mode Band-Pass Filter(BPF) from 2 GHz to 3.4 GHz with a notched band at 2.62 GHz.The dual mode band-pass filter consists of a ring resonator with two quarter-wavelength open-circuited stubs at =90o and =0o,respectively.A square perturbation stub has been put at the corner of the ring resonator to increase the narrow stopbands and improve the performance of selectivity.By using a parallel-coupled feed line,a narrow notched band is introduced at the required frequency and its Fractional BandWidth(FBW) is about 5%.The proposed filter has a narrow notched band and a wide pass-band with a sharp cutoff frequency characteristic,the attenuation rate for the sharp cutoff frequency responses is 297.17 dB/GHz(cal-culated from 1.959 GHz with-34.43 dB to 2.065 GHz with-2.93 dB) and 228.10 dB/GHz(calculated from 3.395 GHz with-2.873 dB to 3.507 GHz with-28.42 dB).This filter has the advantages of good insertion loss in both operating bands and two rejections of greater than 16 dB in the range of 1.59 GHz to 1.99 GHz and 3.49 GHz to 3.98 GHz.Having been presented in this article,the measurement results agree well with the simulation results,which validates our idea.展开更多
A high performance Balun BandPass Filter (BPF) with capacitively loaded multiple coupled lines with very simple structure is proposed in this paper, this structure realizes simultaneous size reduction and superior har...A high performance Balun BandPass Filter (BPF) with capacitively loaded multiple coupled lines with very simple structure is proposed in this paper, this structure realizes simultaneous size reduction and superior harmonic response suppression performance in bandpass filtering meanwhile good differential performance of the Balun. The theory of this structure for unbalanced input into balanced output has been studied in this paper and a proper Balun and BPF characteristic by the symmetric feeding and skew symmetric feeding have been obtained to prove the theory. The enter frequency of the fabricated Balun-BPF is operated at 2.45 GHz with 6.93% Fractional Band Width (FBW), and this frequency is used for Bluetooth and some other communication systems. The differences between the two outputs are 180°± 1.92° in phase and within 0.33 dB in magnitude. At f0, the amplitude imbalance and phase difference are within 0.25 dB and 180.86°, respectively. The measured frequency responses agree well with the simulated ones. With the theoretical analyses and practical results, it is shown that the proposed one has the advantages of simple structure, convenient analysis and good performance of both BPF and Balun.展开更多
In this paper,a Slotted Stepped-Impedance Resonator (SSIR) is proposed.Due to the slots in the low-impedance section of the conventional SIR,the new resonator has a lower fundamental resonance f0 and can provide a pot...In this paper,a Slotted Stepped-Impedance Resonator (SSIR) is proposed.Due to the slots in the low-impedance section of the conventional SIR,the new resonator has a lower fundamental resonance f0 and can provide a potential finite transmission zero fz close to f0.Based on the proposed SSIR,a fourth-order Chebychev BandPass Filter (BPF) is designed at f0=1 GHz.The measured results show that a better than-65 dB rejection is achieved on both the lower and the upper stopband.Moreover,the new filter has a wide-30 dB rejection upper stopband from 1.13f0 to 6.52f0.The fabricated filter exhibits a size of The new filter has a planar topology and is easily integrated with modern portable communication systems.展开更多
An Electromagnetic Band Gap (EBG) loaded square waveguide Band-Pass Filter (BPF) is proposed in this paper. It’s simply composed by symmetrically loading periodical metal diaphragms on each wall of a square waveguide...An Electromagnetic Band Gap (EBG) loaded square waveguide Band-Pass Filter (BPF) is proposed in this paper. It’s simply composed by symmetrically loading periodical metal diaphragms on each wall of a square waveguide. The influences of insert sizes and loading periods on the overall BPF performances are analyzed. Experimental results agree well with those predicted. 6 GHz pass-band with insert loss less than 1 dB, 2.5 GHz stop-band and larger than 25 dB polarization isolation can be obtained. The BPF can be applied in dual-polarized waveguide-based antenna-feed systems.展开更多
基金Supported by a grant from the Ph.D. Programs Foundation of Ministry of Education of China (No. 20030003074) and the National Natural Science Founda-tion of China (No. 10575059).
文摘In this article we introduce an exact backprojection filtered (BPF) type reconstruction algorithm for cone-beam scans based on Zou and Pan’s work. The algorithm can reconstruct images using only the projection data passing through the parallel PI-line segments in reduced scans. Computer simulations and practical experiments are carried out to evaluate this algorithm. The BPF algorithm has a higher computational efficiency than the famous FDK algorithm. The BPF algorithm is evaluated using the practical CT projection data on a 450 keV X-ray CT system with a flat-panel detector (FPD). From the practical experiments, we get the spatial resolution of this CT system. The algo- rithm could achieve the spatial resolution of 2.4 lp/mm and satisfies the practical applications in industrial CT inspec- tion.
基金Supported by the National Natural Science Foundation of China (No. 51007040)
文摘This paper presents a planar microstrip wideband dual mode Band-Pass Filter(BPF) from 2 GHz to 3.4 GHz with a notched band at 2.62 GHz.The dual mode band-pass filter consists of a ring resonator with two quarter-wavelength open-circuited stubs at =90o and =0o,respectively.A square perturbation stub has been put at the corner of the ring resonator to increase the narrow stopbands and improve the performance of selectivity.By using a parallel-coupled feed line,a narrow notched band is introduced at the required frequency and its Fractional BandWidth(FBW) is about 5%.The proposed filter has a narrow notched band and a wide pass-band with a sharp cutoff frequency characteristic,the attenuation rate for the sharp cutoff frequency responses is 297.17 dB/GHz(cal-culated from 1.959 GHz with-34.43 dB to 2.065 GHz with-2.93 dB) and 228.10 dB/GHz(calculated from 3.395 GHz with-2.873 dB to 3.507 GHz with-28.42 dB).This filter has the advantages of good insertion loss in both operating bands and two rejections of greater than 16 dB in the range of 1.59 GHz to 1.99 GHz and 3.49 GHz to 3.98 GHz.Having been presented in this article,the measurement results agree well with the simulation results,which validates our idea.
文摘A high performance Balun BandPass Filter (BPF) with capacitively loaded multiple coupled lines with very simple structure is proposed in this paper, this structure realizes simultaneous size reduction and superior harmonic response suppression performance in bandpass filtering meanwhile good differential performance of the Balun. The theory of this structure for unbalanced input into balanced output has been studied in this paper and a proper Balun and BPF characteristic by the symmetric feeding and skew symmetric feeding have been obtained to prove the theory. The enter frequency of the fabricated Balun-BPF is operated at 2.45 GHz with 6.93% Fractional Band Width (FBW), and this frequency is used for Bluetooth and some other communication systems. The differences between the two outputs are 180°± 1.92° in phase and within 0.33 dB in magnitude. At f0, the amplitude imbalance and phase difference are within 0.25 dB and 180.86°, respectively. The measured frequency responses agree well with the simulated ones. With the theoretical analyses and practical results, it is shown that the proposed one has the advantages of simple structure, convenient analysis and good performance of both BPF and Balun.
文摘In this paper,a Slotted Stepped-Impedance Resonator (SSIR) is proposed.Due to the slots in the low-impedance section of the conventional SIR,the new resonator has a lower fundamental resonance f0 and can provide a potential finite transmission zero fz close to f0.Based on the proposed SSIR,a fourth-order Chebychev BandPass Filter (BPF) is designed at f0=1 GHz.The measured results show that a better than-65 dB rejection is achieved on both the lower and the upper stopband.Moreover,the new filter has a wide-30 dB rejection upper stopband from 1.13f0 to 6.52f0.The fabricated filter exhibits a size of The new filter has a planar topology and is easily integrated with modern portable communication systems.
文摘An Electromagnetic Band Gap (EBG) loaded square waveguide Band-Pass Filter (BPF) is proposed in this paper. It’s simply composed by symmetrically loading periodical metal diaphragms on each wall of a square waveguide. The influences of insert sizes and loading periods on the overall BPF performances are analyzed. Experimental results agree well with those predicted. 6 GHz pass-band with insert loss less than 1 dB, 2.5 GHz stop-band and larger than 25 dB polarization isolation can be obtained. The BPF can be applied in dual-polarized waveguide-based antenna-feed systems.
