A self‐matched negative group delay circuit with tunable center frequency and group delay

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 .…”

“…18 To obtain the reconfigurable NGDCs, several circuits have been designed. [19][20][21][22][23][24][25][26][27] In the early stages of the research, the tunable NGDCs were mainly designed using series or parallel RLC resonance circuits. [19][20][21] With the variable resistor, the variable NGD time can be obtained.…”

“…But these NGDCs are reflection-type and need extra hybrid couplers to realize port matching. In order to achieve transmission-type, a self-matched tunable NGDC 22 and a reconfigurable NGDC based on branch-line 23 were proposed. In References [22,23], the minimum available NGD time is À10 ns and suffers from a great insertion loss (IL) of about 35 dB.…”

“…In order to achieve transmission-type, a self-matched tunable NGDC 22 and a reconfigurable NGDC based on branch-line 23 were proposed. In References [22,23], the minimum available NGD time is À10 ns and suffers from a great insertion loss (IL) of about 35 dB. Therefore, two methods were proposed to reduce the attenuation.…”

“…For the applications of broadband phase shifters, 28 the flatness of the NGD time is critical. Except Reference [23], all of the tunable NGDCs in References [19][20][21][22][23][24][25][26][27] cannot achieve a flat NGD time. In Reference [23], two branchline couplers operating at different center frequencies have been cascaded and the NGD time tuning range À2.23 to À6.94 ns was achieved.…”