基于DSPSL 的电可重构平面带通滤波器

提出基于新型平衡传输线——双面平行带线(DSPSL)结构的电容加载电可重构平面带通滤波器,并以梳状线 和磁耦合谐振环带通滤波器为例验证该方案的可行性。相对于常见的微带线结构,双面平行带线具有对称性以及较高 的功率使用容量。这些特性使得滤波器在没有无限大金属地板的情况下,仍然获得了良好的性能。采用DSPSL 结构 进行微波电路设计不但可以减小电路的尺寸,同时还增加了电路设计的灵活性。     

Compact microstrip lowpass filter using shunt open stubs and coupled slots on ground plane

A compact microstrip lowpass filter with prominent cutoff sharpness and very wide stopband is presented. The microstrip lowpass filter is composed of a transmission line with shunt open stubs on the topside of the microstrip structure and coupled slots on the ground plane. The shunt open stub microstrip filter with slots on the ground plane has a wide stopband at high frequency, and the coupled slot on the ground plane has sharp cutoff response at low frequency. The combined characteristics of these structures make for an excellent lowpass filter performance.     

Open- and short-circuit terminated series stubs in finite-widthcoplanar waveguide on silicon

Open- and short-circuit terminated series stubs in finite-width coplanar waveguide (FCPW) fabricated on high-resistivity Si are experimentally characterized over the frequency range of 2-40 GHz. In coplanar waveguide (CPW), these stubs are typically placed in the center conductor, but in FCPW, the stubs may also be placed in the ground planes resulting in novel circuit elements with characteristics that make the stubs useful for matching circuits and filters. Equivalent circuit models for the stubs are presented, and it is shown that when the stub is in the ground plane the resonant frequency is equal, the inductance and resistance is halved, and the capacitance is double the values of the same stub in the center conductor. Furthermore, it is shown that by varying the stub position in the ground plane, higher Q stubs can be obtained     

Experimental and theoretical characterization of miniature coplanar waveguide shunt stubs patterned on the centre conductor

Several new designs are presented for coplanar waveguide (CPW) open- and short-ended shunt stubs patterned on the centre conductor. Unlike conventional stubs which are patterned on the ground plane, the new designs are more compact and less radiative. They also provide more flexibility to the design of CPW circuits. The performance of the new stubs is verified by experiment and simulation and is found to be very satisfactory over the large frequency band 0–50GHz. Experimental results obtained for a conventional and new stub show that the new stub is less radiative.     

The current distribution and AC resistance of a microstripstructure

The AC resistance of the strip in a microstrip structure is compared with that of an isolated strip for better understanding of the conductor loss mechanism. An analysis is presented of the AC resistance in a microstrip structure for any metallization thickness by deriving the current distribution over the strip cross section. The analysis uses the separation of variables technique and the Green's function method. It shows that the skin current of the strip is concentrated toward the ground plane in a microstrip structure. In the extreme case, the AC resistance of the strip can be twice as high as the AC resistance of the same isolated strip. The imperfect ground plane also adds to the total conductor loss of a microstrip line. For a wide strip over a lossy ground plane at high frequency, the ground plane surface current distribution is concentrated directly under the strip, and the ground plane AC resistance can be as large as the strip AC resistance. Therefore, the total AC resistance at the microstrip line can be four times as high as that of an isolated strip conductor     

Characterization of buried microstrip lines for constructinghigh-density microwave integrated circuits

This paper describes the characterization of a guided wave structure, buried microstrip line (BMSL), which is considered to be promising for constructing high-density microwave and millimeter-wave integrated circuits because of its high isolation characteristics. The BMSL includes a dielectric medium surrounded by ground conductor walls and a strip conductor on the top of the dielectric. The BMSL structure is characterized by the two methods, the rectangular boundary division (RBD) method and the finite-difference time-domain (FDTD) method. The RBD method is employed to obtain basic parameters of the BMSL such as characteristic impedances and coupling coefficients over a wide range of line sizes taking advantages of its high calculation efficiency. On the other hand, the FDTD method has been used for more detailed characterization such as the frequency performances of stub matching circuits. The FDTD method is also used to confirm the validity of the quasi-TEM wave approximation which the RBD is based on. The analysis results reveal that the BMSL structure possesses much lower coupling coefficients than a conventional microstrip line does, from -15 dB to -100 dB depending on their burial depths     

A Differential Voltage-Controlled Integrated Antenna Oscillator Based on Double-Sided Parallel-Strip Line

A voltage-controlled integrated antenna oscillator (VCIAO) integrating a differential voltage-controlled oscillator (VCO) with a double-sided parallel-strip line (DSPSL)-fed quasi-Yagi antenna based on the DSPSL is presented in this paper. The quasi-Yagi antenna is used not only as the radiating element, but also as the output power combiner and the resonating load of the differential VCO without any matching circuits or transition between them. The two sub-oscillators of the VCO on the opposite sides of the substrate share a common quarter-wavelength DSPSL resonator and a common inserted ground plane, which also works as the reflecting element for the quasi-Yagi antenna. The common DSPSL resonator terminated by a series varactor can not only help to synchronize the two sub-oscillators, but also realize tunable oscillating frequency. Due to the differential output of the proposed VCO, the cross polarization of the proposed VCIAO is suppressed to a great extent in the entire tunable frequency range.     

Compact microstrip bandpass filter with two transmission zeros using a stub-tapped half-wavelength line resonator

A compact microstrip bandpass filter is developed using a half-wavelength (/spl lambda//2) transmission line resonator with a pair of tap-connected open-ended stubs. Such paired stubs with total length of about /spl lambda//2 constructs an equivalent line resonator. Together with two separated /spl lambda//4 line resonators, the three transmission poles can be achieved inside the passband. Meanwhile, two stub lengths are adjusted slightly longer and shorter than /spl lambda//4 to realize the two transmission zeros at both low and high rejection bands. Further, the long tapped-stub is kept wider than its short counterpart to improve the low rejection behavior. A filter sample is designed and fabricated to provide an experimental verification on the proposed filter.     

Novel Microstrip Photonic Bandgap Cell Structures

In general, a planar microstrip photonic bandgap (PBG) structure os a periodic array of holes etched in the ground plane of a microstrip line. To use a circuit with a PBG, the PBG structure cannot be fixed on a metal base and needs to be shielded. In this paper, two kinds of novel microstrip PBG unit cells with special patterns etched in the strip line, which can be used as the conventional microstrip circuits, are proposed and analyzed in detail. The results show that the transmission line theory is valid for the theoretic analysis of PBG circuits.     

Miniaturized Dual-Mode Ring Bandpass Filters With Patterned Ground Plane

Miniaturized dual-mode ring bandpass filters with a patterned ground plane are proposed. By loading the resonator periodically with the butterfly radial slot cells on the ground plane, the size of a ring filter is reduced along with an extended upper stopband. Based on the equivalent circuits, the mode-splitting characteristics and impact of the patterned ground plane on the electrical performances of the filter are investigated. A slotline ring filter with a patterned ground plane is also proposed. The miniaturization is achieved by loading the periphery of the slotline ring with the butterfly radial stubs at the backside. The filter has a higher first spurious response and deeper stopband rejection than a conventional microstrip ring filter. Measured results validate the analysis and theoretical prediction with good agreement.     

A small dielectric TEM mode resonator with a crossing slot and itsapplication to a cellular radio VCO

A small TEM-mode dielectric resonator which features a crossing slot on the outer ground conductor plane is presented. The slot, functioning as a short-ended stub line serially inserted into the transmission line, can tune the resonant frequency down. The resonant frequency in a stripline resonator structure is rigorously analyzed by a method based on the spectral domain approach and the equivalent circuit is derived. This resonator is used in a cellular radio VCO with a varactor connected across the slot. The performance of the VCO in the 900-MHZ cellular band is described     

Compact Wide-Band Bandpass Filter Using Microstrip to Slotline Broadside-Coupling

In this letter, two quarter wavelength microstrip stubs with a shorted slot line resonator etched in the ground plane is used to design a compact wideband bandpass filter (BPF). Wideband characteristics are obtained using broadside-coupling between the stubs and the slot line. 3-dB fractional bandwidth (FBW) is varied by changing coupled line widths. The filter has the advantages of compactness, wide bandwidth, low passband insertion loss (IL), low group delay variation and ease of fabrication. One prototype fabricated filter has a FBW of 60.0% with a maximum passband IL of 0.9 dB and group delay variation of 0.40 nS. BPF occupying area is less than 0.19lambdagtimes0.20lambdag, where lambdag is the guided wavelength at midband frequency 2.5 GHz. Good agreement between measurements and simulations are obtained.     

Lowpass filter using offset double-sided parallel-strip lines

A novel lowpass filter using offset double-sided parallel-strip lines (DSPSL) is proposed. The proposed lowpass filter has the advantages of enhanced stopband and high power-handling capability compared with the conventional microstrip lowpass filter, because the high impedance is realised by offsetting the top and bottom strips of DSPSL without decreasing the width of strips. The theoretical and measured results are presented.     

Wideband Parallel-Strip Bandpass Filter Using Phase Inverter

A new wideband parallel-strip bandpass filter using phase inverter with stubs is proposed. With the wideband phase inverter in the parallel-strip line structure, the measured fractional passband bandwidth is 123% with a flat group delay response. Also, over 90% impedance bandwidth is obtained for the return loss higher than 20 dB. The theoretical simulation, electromagnetic simulation, and measured results show good agreement with this proposed design.      

High-Pass Filtering Characteristics of Transmission-Line Combs

The filtering characteristics of a transmission line loaded at regular intervals with closely spaced shorted stubs are investigated theoretically, experimentally, and by means of rigorous electromagnetic simulations. It is shown that this periodic structure exhibits waveguide-like behavior with a first passband whose width is a function of the characteristic impedance and pitch of the stubs. It is also shown that when the stub pitch vanishes, the structure degenerates into a waveguide whose mode-cutoff frequencies correspond to a shorted-stub length that is an odd multiple of the wavelength. These features enable the design of compact high-pass filters, and make possible cutoff-frequency hopping and tuning. Implementations in microstrip are shown that demonstrate desirable characteristics such as wide bandwidth, low insertion loss, reduced size, easy integration with planar circuits, as well as common and differential-mode filtering, making such structures attractive for use in low-cost microwave and millimeter-wave applications.      

Coupled TEM Microstrip Impedance Transformer for S-Band TRAPATT Amplifiers

A coupled TEM microstrip line circuit suitable for use in S-band TRAPATT amplifiers has been investigated. An analytical model of the coupled-line structure has been developed which properly accounts for diode positioning on the line. This model has been used to calculate the fundamental and harmonic impedances at the device terminals for various stub terminations and device locations. Measurements made with a Hewlett-Packard network analyzer are in good agreement with the calculated results. The use of this circuit for the development of a fixed-tuned MIC circuit for the TRAPATT amplifier on Duroid Substrate is discussed. The complete circuit incorporates a bias line filter with this coupled microstrip line and appropiate harmonic tuning stubs at two of its ports. It is capable of providing at least 6-percent 1-dB bandwith with high efficiency and high peak power output over pulsewidths up to 50 mu s and up to 1-percent duty cycle.     

Design of 10 dB 90° branch line coupler using microstrip linewith defected ground structure

The authors present a 10 dB 90° branch line coupler operating at 1.8 GHz and having a defected ground structure (DGS), a type of periodic structure realised by etching on the ground plane under the microstrip line. Owing to the additional effective inductance of the DGS, the characteristic impedance of the microstrip line is increased for the same width of conductor. A microstrip line of 150 Ω of characteristic impedance with 1 mm conductor width is realised by adding the DGS, while 1 mm corresponds to 82 Ω of conventional microstrip line on the RT/Duroid 5880 substrate with 2.2 dielectric constant and 31 mils of thickness. It is shown that a 90° branch-line 10 dB coupler can be fabricated using the 150 Ω line with DGS. Its measured performances are in good agreement with the predicted results     

一种结构新颖的小型化微带分支线定向耦合器

提出一种通过小型化而制作出的具有新型结构的微带分支线定向耦合器,其中小型化运用了将传统的传输线等效为传输线两端接终端开路线达到缩短目的,得到的主线与分支线之间的终端开路线可继而等效为传输线两边接短截线形式以避免终端开路线的重叠,从而最终得到一种新的结构。与传统耦合器相比面积缩小了64%。通过理论计算得到的频率特性与ADS仿真得到的频率特性基本一致,从而验证了可行性。     

Asymmetric Parallel-Coupled Lines for Notch Implementation in UWB Filters

In this letter, a novel microstrip parallel-coupled line structure with two asymmetric loading stubs is proposed for notched band implementation in ultra-wideband (UWB) bandpass filter (BPF). The rejection band is introduced by adding asymmetric loading stubs to the two outer arms of three parallel-coupled lines. The lengths and the widths of the stubs can control the bandwidth of the notched filter and can set the notched band at a desired frequency. This structure has been applied to a single-stage UWB BPF in order to produce a narrow notched band inside its passband. The design is successfully realized in theory and verified by full-wave electromagnetic simulation and the experiment.     

A Double-Sided Parallel-Strip Line Push–Pull Oscillator

A novel double-sided parallel-strip line (DSPSL) push-pull oscillator using two identical sub-oscillators on the opposite sides of a dielectric substrate is proposed. The two sub-oscillators, sharing a common DSPSL resonator and common ground in the middle of the substrate, generate out-of-phase fundamental signals and in-phase second harmonics. At the common DSPSL output, the second harmonics are cancelled out while the fundamental signals are well combined. By this design, an additional combiner at the output, as required by the conventional push-pull circuits, is not needed, which greatly reduces the circuit size and simplifies the design procedures of the proposed push-pull oscillator.