Distributed Transmission Line Negative Group Delay Circuit With Improved Signal Attenuation

Chaudhary, Girdhari,Yongchae Jeong IEEE 2014 IEEE microwave and wireless components letters Vol.24 No.1

<P>In this letter, a novel design and implementation of a distributed negative group delay circuit (NGDC) with reduced signal attenuation is demonstrated. By inserting an additional transmission line Z2 into the conventional NGDC, the proposed NGDC provides further design parameters in order to obtain the required differential-phase group delay (GD) time and help to reduce the signal attenuation. As a result, the number of gain compensating amplifiers can be reduced, which can contribute to the efficiency enhancement as well as the stable operation when integrated into the RF system. Both theory and experiment are provided to validate the proposed structure. From the experiment, for the same GD time of -7.9 ns, the signal attenuation of the proposed circuit is 16.5 dB, an improvement signal attenuation of the conventional circuit of 19.2 dB.</P>

A Design of Power Divider With Negative Group Delay Characteristics

Chaudhary, Girdhari,Yongchae Jeong IEEE 2015 IEEE microwave and wireless components letters Vol.25 No.6

<P>In this letter, the design of power divider with negative group delay (NGD) characteristics is presented. From an analysis, the NGD associated with different transmission paths is found to be identical and obtained by loading resistor connected short-circuited coupled lines with an open-circuited isolation port. The proposed structure is validated by constructing a two-way microstrip line power divider with equal power division ratio, which is centered at 2.14 GHz. The measured results show excellent agreement with simulations and theoretically predicated results. From the measurement, the group delays and magnitudes of S-parameters between the different transmission paths are determined as -1.16 ns, -9.29 dB, -1.17 ns, and -9.30 dB. The measured input/output return losses and isolation at center frequency are higher than 28.92 dB, 26.76 dB, and 42.2 dB.</P>

Microstrip Line Negative Group Delay Filters for Microwave Circuits

Chaudhary, Girdhari,Yongchae Jeong,Jongsik Lim IEEE 2014 IEEE transactions on microwave theory and techniqu Vol.62 No.2

<P>This paper presents a novel approach to the design and implementation of a distributed transmission line negative group delay filter (NGDF) with a predefined negative group delay (NGD) time. The newly proposed filter is based on a simple frequency transformation from a low-pass filter to a bandstop filter. The NGD time can be purely controlled by the resistors inserted into the resonators. The performance degradation of the NGD time and signal attenuation (SA) of the proposed NGDF according to the temperature dependent resistance variation is also analyzed. From this analysis, it is shown that the NGD time and SA variations are less sensitive to the resistance variation compared to those of the conventional NGD circuit. For an experimental validation of the proposed NGDF, a two-stage distributed microstrip line NGDF is designed, simulated, and measured at an operating center frequency of 1.962 GHz. These results show a group delay time of -7.3 ns with an SA of 22.65 dB at the center frequency and have good agreement with the simulations. The cascaded response of two NGDFs operating at different center frequencies is also presented in order to obtain broader NGD bandwidth. NGDFs with good reflection characteristics at the operating frequencies are also designed and experimentally verified.</P>

Transmission-Line Negative Group Delay Networks With Improved Signal Attenuation

Chaudhary, Girdhari,Yongchae Jeong IEEE 2014 IEEE antennas and wireless propagation letters Vol.13 No.-

<P>This letter presents a novel design and implementation of a transmission-line negative group delay (NGD) network with improved signal attenuation (SA). Theoretical analysis shows that the NGD time can be controlled by characteristic impedance of the coupled line, coupling coefficients, and resistor, respectively. The low SA characteristic in the proposed structure is obtained due to high characteristic impedance of the coupled line. To validate the proposed structure, the transmission-line NGD networks are fabricated and measured at 2.14 GHz. From the experiment, the differential-phase group delay (GD) time and SA for a single stage are -6.16 ns and 8.65 dB over bandwidth of 15 MHz, respectively. For bandwidth enhancement, two-stage NGD networks with slightly different center frequencies are designed and fabricated, where GD of -7.48 ±0.84 ns and SA of 17.45 dB were obtained over a bandwidth of 28 MHz.</P>

A Design of Reconfigurable Negative Group Delay Circuit Without External Resonators

Chaudhary, Girdhari,Yongchae Jeong,Jaejoong Im IEEE 2015 IEEE antennas and wireless propagation letters Vol.14 No.-

<P>In this letter, we present the novel design and implementation of a microstirp line reconfigurable negative group delay circuit (NGDC) using a branch-line. Theoretical analysis shows that reconfigurable characteristics in the proposed circuit can be obtained by properly choosing the characteristic impedances of the branch-line and tuning only the termination resistance. Therefore, the proposed reconfigurable NGDC does not require any extra resonators. For experimental validation, the proposed circuit was designed and fabricated for a wideband code division multiple access downlink frequency operating at a center frequency ( f<SUB>0</SUB>) of 2.14 GHz. Measurement results show the group delays variation of -2 ns to -10 ns with signal attenuation variation of -25 dB to -36.6 dB at f<SUB>0</SUB>. For enhancement of the negative group delay bandwidth, two NGDCs operating at slightly different center frequencies are cascaded and measured.</P>

APMC 2023 참가기

Girdhari Chaudhary 한국전자파학회 2024 전자파기술 Vol.35 No.1

Arbitrary Power Division Ratio Rat-Race Coupler With Negative Group Delay Characteristics

Chaudhary, Girdhari,Jeong, Yongchae THE INSTITUTE OF ELECTRICAL ENGINEERS 2016 IEEE Microwave and Wireless Components Letters Vol. No.

<P>In this letter, we present theoretical and experimental investigations of a rat-race coupler with negative group delay (NGD) characteristics and an arbitrary power division ratio. From the theoretical analysis, the NGD characteristics can be obtained through various transmission paths and have small variations with the power division ratio. The power division ratio is controlled by only the characteristic impedance of the transmission lines. Ideal port isolation and return loss characteristics are obtained at a center frequency for any arbitrary power division ratio. For experimental demonstration, a microstrip line rat-race coupler is implemented with center frequency of 2.14 GHz. The measurement results agree well with simulation results and theoretically predicated values.</P>

Low Signal-Attenuation Negative Group-Delay Network Topologies Using Coupled Lines

Chaudhary, Girdhari,Yongchae Jeong IEEE 2014 IEEE transactions on microwave theory and techniqu Vol.62 No.10

<P>This paper presents the design and analysis of novel topologies of reflective-type negative-group-delay (NGD) networks with very small signal attenuation (SA). The proposed topologies are based on short-circuited coupled lines. Theoretical analysis shows that predefined group-delay (GD) time with very small SA can be obtained due to the high characteristic impedance of a coupled line and the small coupling coefficient. Due to the very low SA characteristics of the proposed networks, the burden of compensating general-purpose gain amplifiers can be reduced and provide stable operations while integrated to RF systems. This paper also analyses performance degradation of the GD time and SA of the proposed NGD networks according to the temperature-dependent resistance variation. For an experimental validation of the proposed topologies, distributed microstrip line NGD networks (type-I and type-II) are designed, simulated, and measured for a wideband code division multiple access (WCDMA) downlink frequency operating at a center frequency of 2.14 GHz. These results show a GD time of -7.27 ns with an SA of 7.43 dB for the type-I NGD network, and -6.3 and 9.23 dB for the type II- NGD network at the center frequency, and agree closely with the simulations. To enhance the NGD bandwidth, two NGD networks with slightly different center frequencies are connected in parallel, which provides wider bandwidth than the single stage case and shows practical applicability.</P>

Negative Group Delay Phenomenon Analysis in Power Divider: Coupling Matrix Approach

Chaudhary, Girdhari,Yongchae Jeong IEEE 2017 IEEE transactions on components, packaging, and ma Vol.7 No.9

<P>This paper presents a negative group delay (NGD) phenomenon analysis of a power divider using the coupling matrix approach. The proposed power divider can provide an arbitrary power division ratio with a minimal effect on group delay variations. From the analysis, it is found that the proposed circuit can provide positive group delay (PGD) and NGD through different transmission paths. The NGD can be generated without a lumped resistor and can be controlled by source-resonator coupling and unloaded-quality factor (Qu) of resonators. For experimental validation, power dividers with PGD and NGD of 0.3 and -1 ns, respectively, were designed and fabricated. The measurement results agreed well with the simulation and the predicated values. The proposed power divider topology is useful for the performance improvement of microwave circuits and systems.</P>

Tunable Center Frequency Negative Group Delay Filter Using Coupling Matrix Approach

Chaudhary, Girdhari,Jeong, Yongchae IEEE 2017 IEEE microwave and wireless components letters Vol.27 No.1

<P>In this letter, a negative group delay filter (NGDF) with tunable center frequencies is presented. The proposed filter is designed using finite unloaded-Qu resonators based on the coupling matrix approach. The proposed NGDF does not require a lumped resistor to generate a negative group delay and has source-load and inter-resonator couplings. The center frequency of the filter is tuned by varying the bias voltage of the varactor diodes. The design theory for the proposed filter is validated experimentally through fabrication of a second-order NGDF at a center frequency of 2.14 GHz.</P>