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 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

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>

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>

Miniaturized Dual-Band Negative Group Delay Circuit Using Dual-Plane Defected Structures

Chaudhary, Girdhari,Yongchae Jeong,Jongsik Lim IEEE 2014 IEEE microwave and wireless components letters Vol.24 No.8

<P>In this letter, a design for a dual-band negative group delay circuit (NGDC) using dual-plane U-shaped defected structures is presented. The center frequency and group delay (GD) time of each band are separately controlled by a defected microstrip structure (DMS) and a defected ground structure (DGS) with resistors connected across the DMS and DGS slots. To verify the design concept, the NGDC is designed, fabricated, and compared with the circuit simulation. To get a wideband bandwidth, two NGDCs with different center frequencies are connected in a cascade design. From the measurements, the GD times of -4.54 ±0.6 ns and -4.20 ±0.5 ns are obtained at 3.46-3.58 GHz and 5.10-5.20 GHz, respectively.</P>

Synthesis of Reflection-Type Coupled Line All-Pass Circuit With Arbitrary Prescribed Wideband Flat Group Delay

Chaudhary, Girdhari,Jeong, Yongchae THE INSTITUTE OF ELECTRICAL ENGINEERS 2017 IEEE Microwave and Wireless Components Letters Vol. No.

<P>In this letter, the analytical design method of a reflection-type coupled line all-pass circuit with arbitrary predefined wideband flat group delay (GD) is presented. The proposed circuit consists of 90 degrees hybrid and coupled lines with a short-circuited load. The proposed structure is simple and does not require any iterative process to obtain optimum circuit parameters. Theoretical and experimental results are provided for validation of the proposed structure. The prototype circuits were fabricated at a center frequency of 2.5 GHz with 2 and 4 ns flat GD responses. The measurement results agreed well with the simulation and theoretical predicted results.</P>

Harmonic Suppressed Dual-Band Bandpass Filter with Independently Tunable Center Frequencies and Bandwidths

Girdhari Chaudhary,Yongchae Jeong,Jongsik Lim 한국전자파학회JEES 2013 Journal of Electromagnetic Engineering and Science Vol.13 No.2

This paper presented a novel approach for the design of a tunable dual-band bandpass filter (BPF) with independently tunable passband center frequencies and bandwidths. The newly proposed dual-band filter principally comprised two dual-mode single band filters using common input/output lines. Each single BPF was realized using a varactorloaded transmission line resonator. To suppress the harmonics over a broad bandwidth, a defected ground structure was used at the input/output feeding lines. From the experimental results, it was found that the proposed filter exhibited the first passband center frequency tunable range from 1.48 to 1.8 ㎓ with a 3-㏈ fractional bandwidth (FBW) variation from 5.76% to 8.55%, while the second passband center’s frequency tunable range was 2.40 to 2.88 ㎓ with a 3-㏈ FBW variation from 8.28% to 12.42%. The measured results of the proposed filters showed a rejection level of 19 ㏈ up to more than 10 times the highest center frequency of the first passband.

Reconfigurable Negative Group Delay Circuit with a Low Insertion Loss Using a Coupled Line

Girdhari Chaudhary,Yongchae Jeong 한국전자파학회JEES 2020 Journal of Electromagnetic Engineering and Science Vol.20 No.1

This paper presents a design of a transmissive-type, low insertion loss (IL) negative group delay (NGD) circuit with a reconfigurable NGD. The proposed circuit consists of a series transmission lines (TLs) and shunt short-circuited coupled lines where an isolation port is terminated with a parasitic compensated PIN diode. Analytical design equations are derived to obtain the circuit parameters for the predefined NGD and IL. The low IL can be achieved because of the very high characteristic impedance of the short-circuited coupled lines. The TL terminated with a PIN diode is used to achieve the constant center frequency of reconfigurable NGD circuit. For experimental validation, the NGD circuit is designed and fabricated at a center frequency (f0) of 2.14 GHz. In the measurement, the NGD varies from -0.5 ns to -2 ns with an IL variation of 2.08 to 3.60 dB at f0 = 2.14 GHz. The NGD bandwidth (bandwidth of GD less than 0 ns) varies from 90 MHz to 50 MHz. The minimum input/output return losses are higher than 10 dB for the overall tuning range.

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>