ANALYTICAL DESIGN OF A MICROSTRIP UWB BPF WITH SHARP REJECTION

This paper presents a new Ultra-WideBand (UWB) BandPass Filter (BPF) using half-wavelength Stepped-Impedance Stub-Loaded Resonator (SISLR). Analytical equations derived by the even-odd mode analysis show the new filter has two tunable transmission zeros at both sides of the passband to provide a sharp rejection and seven transmission poles inside the passband to achieve U.S. UWB performance. For verification, a UWB BPF is designed, fabricated and measured. The measured results show that the fabricated filter has a -3 dB fractional bandwidth from 3.0 GHz to 10.9 GHz and its insertion loss less than 0.9 dB over the whole passband. Furthermore, the new filter exhibits a simple topology, sharp rejection, and deep stopband suppression.

SIMULTANEOUS MULTIPLE TARGET RECOGNITION USING POLARIZATION AGILE WAVES

A novel matching method for simultaneous multi-target recognition is proposed by jointly considering target's prior scattering knowledge and the polarization parameters of radar echoes. The matching coefficients are calculated for the judgment. MATLAB simulations show that several targets can be accurately recognized simultaneously, and a high recognition probability can be achieved in Monte Carlo simulations. The total execution time can be remarkably reduced in the Field Programmable Gate Array (FPGA) implementation of the matching procedure.

MINIATURIZED MICROSTRIP BRANCH-LINE COUPLER WITH GOOD HARMONIC SUPPRESSION PERFORMANCE

This paper presents a miniaturized microstrip branch-line coupler with good harmonic suppression performance. The proposed coupler consists of four branch-line sections, each of which is loaded by open-circuit stubs both at the center and the two ends. This type of loading can realize size reduction and harmonic suppression. As an example, a proposed branch-line coupler operating at 1.0 GHz is designed, fabricated and measured. The results show that the proposed branch-line coupler occupies 67% size of a conventional one and has better than 20 dB suppression from 1.9 to 5.8 GHz. Furthermore, the high slop of the transition band ensures good selectivity of the coupler.

Novel Balun Structure for Dipole Antenna

A novel balun structure for dipole antenna,which is based on the current distribution on parallel microstrip lines and the emission cancellation characteristic of close equal and opposite currents,is proposed.The principle of the balun structure is first elaborated and verified.Then,a dipole antenna with resonance at 2.45 GHz is constructed using the balun and its radiation pattern is measured.The simulated and measured reflection coefficients(S_(11))of the antenna are in good agreement 2—3 GHz.The relative bandwidth with an S_(11) of below-10 dB is more than 25%.The antenna also shows a good radiation pattern at 2.45 GHz.The proposed structure can provide a new balun design method for dipole antennas.

A BALUN-BANDPASS FILTER WITH GOOD IN-BAND PERFORMANCE AND WIDE STOPBAND

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.

DUAL MODE WIDEBAND BAND-PASS FILTER WITH NOTCHED BAND FOR COMMUNICATION SYSTEM

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.

COMPACT INTERLOCKED-COUPLED FILTER USING FOLDED STEPPED-IMPEDANCE RESONATORS

A microstrip interlocked-coupled bandpass filter is proposed with a markedly compact structure. The low-impedance open-end line of the quarter-wavelength Stepped-Impedance Resonator (SIR) is replaced by two open-end high-impedance lines, which not only facilitate the coupling mechanism but also provide the strong electric coupling between resonators. With the proper utilization of folded SIRs, the occupied area of coupled-resonator pair can be reduced. By applying the proposed coupled-resonator pair, the passband filter with the compact size can be realized. Good agreement between measured and simulated results is observed. The proposed filter is desirable for compact and high-performance microwave circuit applications.