Folded Transmission Line Research Articles

Miniaturized composite band pass filter using folded transmission lines for wideband radar

A composite design of Band Pass Filter (BPF) is developed with 3-dB fractional bandwidth (FBW) of more than 140%. This BPF is suitable for the development of wideband radar, communication and EW system in 1 to 6 GHz. Composite BPF design utilizes stepped impedance Low Pass Filter (LPF) along with the quarter wavelength (λg/4) short circuited stub. λg/4 short circuited stubs incorporated High Pass Filter (HPF) response which transforms overall design into BPF. Four cases of filter have been discussed. In case-I, the proposed BPF is developed with a size of 32.6 mm X 7.0 mm. Further in case-II, design has been realized with improved roll-off at the lower edge of the bandwidth (i.e., 1GHz). In case-III, developed design is 75% length-wise miniaturized that of case-I. Further in case-IV, about 55% length-wise miniaturization is done. Case-III and IV have their response similar to that of the case-I with miniaturized design. All designs are simulated, optimized and fabricated over RT-Duroid 5880 substrate. For case-I, III and IV fabrication has been done on 20 mil thick substrate, whereas for case-II 31 mil thick substrate is used. Comparisons between all the cases have been presented in tables and S-parameter plots.

Miniaturized narrow band‐pass filter with quarter‐wavelength short stubs using U‐shaped folded transmission line

ABSTRACTIn this article, the miniaturized narrow band‐pass filter (BPF) with 90° short stubs using a U‐shaped folded transmission line is suggested. A U‐shaped transmission line is adopted instead of a conventional transmission line to reduce the size of the BPF on the low dielectric substrate. The size of the conventional narrow BPF is reduced by more than 70% due to the reduction of the length of the transmission line within the inverter. The experimental results show that the insertion loss and return loss are 1.61 dB and 15.4 dB, respectively, with bandwidth of 5% at the center frequency of 5.8 GHz. The designed BPF shows a harmonics rejection up to third (3f0) and fifth (5f0), with more than 18 dB rejection level in the simulation and experimental results. The size of the filter is 19 × 8.6 mm2. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2862–2865, 2015

Analysis of folded pulse forming line operation.

A compact pulse forming line (CPFL) concept based on a folded transmission line and high-breakdown strength dielectric was explored through an effort combining proof-of-principle experiments with electromagnetic modeling. A small-scale folded CPFL was fabricated using surface-mount ceramic multilayer capacitors. The line consisted of 150 capacitors close-packed in parallel and delivered a 300 ns flat-top pulse. The concept was carried to a 10 kV class device using a polymer-ceramic nanocomposite dielectric with a permittivity of 37.6. The line was designed for a 161 ns FWHM length pulse into a matched load. The line delivered a 110 ns FWHM pulse, and the pulse peak amplitude exceeded the matched load ideal. Transient electromagnetic analysis using the particle-in-cell code ICEPIC was conducted to examine the nature of the unexpected pulse shortening and distortion. Two-dimensional analysis failed to capture the anomalous behavior. Three-dimensional analysis replicated the pulse shape and revealed that the bends were largely responsible for the pulse shortening. The bends not only create the expected reflection of the incident TEM wave but also produce a non-zero component of the Poynting vector perpendicular to the propagation direction of the dominant electromagnetic wave, resulting in power flow largely external to the PFL. This analysis explains both the pulse shortening and the amplitude of the pulse.

CMOS Distributed Amplifiers Using Gate–Drain Transformer Feedback Technique

This paper presents CMOS distributed amplifiers (DAs) using the proposed gate-drain transformer feedback technique. The feedback allows reuse of the traveling signal to achieve a high gain-bandwidth product while maintaining low power consumption of DAs. With the folded transmission lines and patterned ground shield, the miniaturized transformer has high quality factors and a well-controlled feedback coupling coefficient. Two DAs are realized using the proposed technique in both 0.18-μm and 90-nm CMOS technologies, respectively. The 0.18-μm CMOS DA achieves a gain of 9.5 dB with a 3-dB bandwidth of 32 GHz, and the noise figure (NF) ranges from 4.1 to 7.6 dB under a power consumption of 71 mW. Under a power consumption of 60 mW, the 90-nm DA demonstrates a gain of 7 dB, a bandwidth of 61.3 GHz, and an NF below 6.2 dB up to 40 GHz. The core areas of the 0.18-μm and 90-nm designs are only 0.58 and 0.41 mm2, respectively.

공통 DGS를 이용한 발진기의 소형화 설계

본 논문에서는 공통 결함접지구조(common defected ground structure, CDGS)를 이용하여 설계한 초고주파 발진기에 대하여 기술한다. 먼저 일반적인 스터브 공진기를 사용하여 발진기를 설계하고, 이를 종래처럼 DGS를 삽입하여 소형화하는 방법을 이용하였다. 최종적으로 DGS 공진기 부분을 반으로 접은 공통 DGS 구조를 이용하여 크기를 대폭 줄인 발진기를 설계하였다. 종래의 DGS를 이용한 경우보다 더욱 소형화된 회로를 얻기 위하여 공통 DGS 구조를 삽입하였다. 공통 DGS 구조를 이용하기 위하여 접혀진 신호선로는 3차원적인 신호선 비어홀(signal via-hole)로 서로 연결된다. 한 설계예로 2.1GHz대에서 소신호 트랜지스터와 공통 DGS 구조를 이용하여 소형화한 발진기를 설계하였다. 설계한 발진기는 표준형 회로에 비하여 11mm만큼 감소한 크기를 가졌다. 제작한 회로를 실제로 측정한 결과 6.7dBm의 출력과 -133dBc/Hz@1MHz의 위상잡음 특성을 얻었다. 출력의 크기는 소형화 이전과 유사한데, 이로써 제안한 발진기 구조의 타당성이 검증된다. In this paper, a design of size-reduced microwave oscillator using common defected ground structure (common DGS) is described. At first, an oscillator is designed using the normal stub resonator, and the conventional DGS patterns are inserted for the first trial of size-reduction. Finally, the DGS resonator section is folded by half size in order to adopt the common DGS, and this produces the proposed size-reduced oscillator. Common DGS pattern is inserted for a better size-reduction than when conventional DGSs are used. The folded transmission line is connected using the 3-dimensional signal via-holes. For an example of design, a 2.1GHz oscillator is designed and fabricated using a small signal transistor and common DGS, which shows the size-reduction of 11 mm. The measurement shows 6.7dBm of output power and -133dBc/Hz@1MHz of phase noise. The measured performances are so similar to those of the oscillators before size-reduction and prove the proposed size-reduction method of oscillators using common DGS.

A reduced size branch‐line hybrid‐ring using coupled lines

AbstractTo miniaturize the hybrid‐ring, a design method is presented herein for the circuit in which there is an electromagnetic coupling between the transmission lines in folded transmission lines. A 3‐dB branch‐line hybrid‐ring is treated. Analysis is carried out for the two cases of homogeneous and inhomogeneous circuit configurations in which each section has only one coupled line. It is found that in the circuit with a homogeneous configuration, perfect match and complete isolation hold at the center frequency as in the conventional type; additionally, the bandwidth becomes narrower as the coupling becomes stronger. In the inhomogeneous structure where the phase velocities of the even and odd modes are different, there is a shift in characteristics. An equal power division can still be accomplished if the degree of coupling and the phase shift in the coupled lines are appropriately chosen. The overall characteristics differ little from the conventional type. To confirm these findings, an inhomogeneous circuit is constructed and the results are found to agree with the theory.