Reconfigurable negative group delay circuit with low signal attenuation

Abstract

A novel circuit scheme is presented for the design of reconfigurable negative group delay circuit (RNGDC) with very low signal attenuation (SA), which is based on a lossy coupled‐line Microstrip (MS) resonator. Theoretical analysis indicates that reconfigurable characteristics in the proposed circuits can be obtained by tuning the resistance of the variable resistor, which is loaded at a specific point on the MS resonator. Based on the study of one‐stage RNGDC, a two‐stage RNGDC arranged in an anti‐symmetrical manner is designed to provide an extended reconfigurable negative group delay range. To validate the performance of the proposed circuit scheme, the prototypes of one‐stage and two‐stage RNGDC have been designed working at a center frequency of 1.73 GHz. Measured results of the two‐stage RNGDC exhibit a group delays variation of −2 ns to −10 ns with signal attenuation variation of −4.5 dB to −9.3 dB at the center frequency, which demonstrates much lower SA compared to the previously‐reported RNGDCs.

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

“…As shown in Table 1, the proposed work has an IL of 3.60 dB when the GD is equal to -2 ns. However, the ILs-28.60 dB in [18], 19.50 dB in [19], and 4.50 dB in [20]-are higher than that of the proposed work for the same GD (e.g., GD = -2 ns). Therefore, the proposed circuit provides a reconfigurable NGD with a low IL compared with the state-of-the-art [18][19][20].…”

“…However, these conventional circuits have a fixed NGD. Efforts have been made to design a reflective-type reconfigurable NGD circuit using a 3-dB hybrid and RLC resonator [18][19][20], which suffers from high insertion loss (IL). The IL in these works can be improved by increasing the characteristic impedance of the resonators and decreasing the value of R for the required NGD.…”

“…However, the improvement of IL is limited because practically, implementing a high characteristic impedance (>130 Ω) microstrip line in PCB technology is difficult. A transmissive-type reconfigurable NGD circuit based on an open radial stub patch and a short-circuited stub with PIN diode is presented in [20]. To make a symmetrical structure, two units of NGD circuits are cascaded back to back, which increasing overall size and IL.…”

Reconfigurable negative group delay circuit with tunable group delay flatness

“…All of these NGDCs in References [1–16] can provide only a fixed negative group delay (NGD) time and cannot satisfy the applications on tunable delay shifter 17 and reconfigurable non‐Foster elements for squint‐free beamforming networks 18 . To obtain the reconfigurable NGDCs, several circuits have been designed 19–27 . In the early stages of the research, the tunable NGDCs were mainly designed using series or parallel RLC resonance circuits 19–21 .…”

“…Therefore, two methods were proposed to reduce the attenuation. One is to introduce the amplifier, 24,25 and the other is to utilize the coupling line 26,27 . In Reference [19], a reconfigurable NGDC was designed based on distributed amplifiers.…”