This paper focuses on the time-domain analysis of bandpass (BP) negative group delay (NGD) function. The innovative NGD investigation is based on the time-domain experimentation of an innovative topology of “lill”-shape passive microstrip circuit. The design principle of the proof of concept (POC) constituted by particular microstrip shapes is described. The NGD circuit is inspired from a recent fully distributed “li”-topology. Before the time-domain investigation, the BP NGD specifications of the circuit under study are academically defined. As practical application of the basic definition, a frequency domain validation of “lill”-circuit is presented in the first section of the paper. The POC circuit is specified by a -8 ns NGD value at 2.31 GHz NGD center frequency and a 27 MHz NGD bandwidth. The “lill”-circuit exhibits an attenuation loss of about -6.2 dB at the NGD center frequency. Then, the two-port black box model of “lill”-NGD-circuit represented by touchstone data of the measured S-parameters is exploited for the transient simulation. The measured group delay (GD) illustrates that the tested “lill”-circuit operates as a BP function regarding the NGD with NGD equal to -8.1 ns at the NGD center frequency. The time-domain demonstration of the BP NGD function was performed using a gaussian pulse modulating sine carrier. The innovative experimental setup with the possibility to plot simultaneously well synchronized input and output signals is explained. The BP NGD time-domain response is understood from commercial tool simulation using the touchstone S-parameters of the measured “lill”-circuit by using a Gaussian up-converted pulse having a 27 MHz frequency bandwidth. It was observed that the output signals are delayed when the sine carrier is out of NGD-band. However, the output signal envelope is in advanced of about -8 ns when the carrier is tuned to be approximately equal to the 2.31 GHz NGD center frequency. To confirm the time-domain typical behavior of BP NGD response, an input pulse signal having Gaussian waveform were considered during the test. However, the input signal spectrum must be determined in function of the NGD bandwidth. After tests, measured output signal envelopes presenting leading edge, trailing edge and peak in time-advance compared to the input ones are observed experimentally. The results of the present feasibility study open a potential microwave communication application of BP NGD function notably for systems operating with ISM and IEEE 802.11 standards.

The miniaturization and application development are the expected challenges on the today engineering design research on bandpass (BP) type negative group delay (NGD) circuit. To overcome this technical limit, an innovative contribution on integrated circuit (IC) design method of BP-NGD application to design constant phase shifter (PS) in 130-nm BiCMOS technology is developed in the present paper. The BP-NGD PS microwave passive IC is topologically consisted of cascade of CLC- and RLC-resonant networks. After the S-matrix modelling, the synthesis design equations enabling to calculate each lumped component values constituting the BP-NGD PS BiCMOS are established. The design equations are expressed knowing the targeted specifications as phase shift and operating frequency. The BiCMOS design methodology including the key steps as design rule checking (DRC), layout versus schematic (LVS) and post-layout simulation (PLS) is described. The miniaturized BP-NGD PS design feasibility is verified with schematic and layout simulations with IC CMOS standard commercial software tool. A proof-of-concept (POC) of 130-nm BiCMOS BP-NGD PS operating at the center frequency $f_{0}=1.9$ GHz and bandwidth $\Delta f=0.1$ GHz is designed and simulated. After DRC, the chip layout of miniaturized BP-NGD PS POC presents 0.407 mm ² size. The BP-NGD PS POC exhibits constant phase shift notable value of about $\varphi _{0}= - 90^{\circ }+$ /−0.4° under $S_{21}(f_{0})= -6$ +/−1 dB transmission coefficient with good flatness and reflection coefficients ( $S_{21}(f_{0})$ and $S_{21}(f_{0})$ ) widely better than −10 dB. The design robustness is confirmed by 1000-trial Monte Carlo uncertainty analyses with PLS results. Because of the potential integration in wireless sensor networks (WSNs), the BP-NGD PS under study is a promising candidate for the improvement of the future 5G and 6G transceiver design.

This article studies a new resistive-capacitive (RC) topology of low-pass (LP) negative group delay (NGD) circuit. The innovative circuit theory includes the LP-NGD analysis and characterization from transfer function canonical form versus the targeted time-advance and the attenuation specifications. The new topology LP-NGD properties in both the frequency-and time-domains are introduced. The NGD value (or time-advance) and cut-off frequency in function of RC parameters, and synthesis formulas are established. The LP-NGD characterization is graphically illustrated by cartography analyses of counter-intuitive time-advance effect and NGD cut-off frequency versus RC-parameters. The LP-NGD circuit theory is transiently validated by good agreement between theory, simulation with LTspice® VXII tool and experimentation of active circuit prototype with arbitrary waveform test signal. Time-advance of some micro-seconds is demonstrated with pulse and arbitrary waveform test signals.