Ernesto Limiti | Università di Roma Tor Vergata (original) (raw)
Papers by Ernesto Limiti
The present contribution summarizes the activities performed towards the realization of a Single-... more The present contribution summarizes the activities performed towards the realization of a Single-Chip Front-End (SCFE) operating in C Band, integrating the High Power, Low Noise amplification and switching functionalities to be provided in modern T/R modules’ Front-Ends for space SAR applications. The technologies adopted in this project are provided by United Monolithic Semiconductors (UMS) and Selex Electronic Systems (SLX), the GH25-10 0.25 μm gate length and the GaN technology featured by 0.5 μm gate length for UMS and SLX respectively. At the completion of the design phase two SCFEs have been designed in the two technologies, each in two slightly different versions, featured by state-of-the-art performance. In particular, in Tx-mode, both are featured by approximately 40 W power output, with 36 dB large-signal gain and 38 % / 27 % PAE for UMS and SLX versions respectively, while in Rx-mode 2.5 dB noise figure resulted, with robust operation. The two dies are featured by 6.9 x 5.4 mm2 and 7.28 x 5.40 mm2 for UMS and SLX versions respectively.
2022 17th European Microwave Integrated Circuits Conference (EuMIC)
2017 12th European Microwave Integrated Circuits Conference (EuMIC)
A D-band LNA is reported serving as a test vehicle of an under-development 40 nm GaAs HEMT techno... more A D-band LNA is reported serving as a test vehicle of an under-development 40 nm GaAs HEMT technology developed by OMMIC foundry. The amplifier, designed on the basis of custom small-signal equivalent-circuit models, is featured by state-of-the-art performance, and in particular has a noise figure as low as 4 dB at 140 GHz and a gain higher than 20 dB approximately from 115 GHz to 160 GHz. The main steps of the non-standard design flow are also illustrated, hinged on two main ideas: a closed-form analysis of the input/output matching bounds of the active devices, on the one hand, and an efficient optimization approach to shift the reference planes of EM-simulated networks, on the other.
IEEE Transactions on Circuits and Systems I: Regular Papers, 2021
The stability criteria based on the Rollett parameter (<inline-formula> <tex-math notati... more The stability criteria based on the Rollett parameter (<inline-formula> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula>) plus one auxiliary condition is yet the most popular method used by designers to evaluate the stability of a two-port network although other criteria are available. In this paper, novel analytical proofs of the criteria utilizing <inline-formula> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> and a new geometrical proof of the relationship between the stability of the ports of a circuit are proposed. They are obtained by making use of relationships between the reflection coefficients at the ports of the network and novel expressions that bind stability circles and unit mapping circles. The developed relations make the proposed proofs easier and more immediate than the traditional ones. Moreover, a new auxiliary condition having the same complexity and a greater geometrical insight with respect to the traditional ones is used.
IEEE Transactions on Circuits and Systems I: Regular Papers, 2021
This work is focused on the design of broadband amplifiers by exploiting dissipative reciprocal m... more This work is focused on the design of broadband amplifiers by exploiting dissipative reciprocal matching networks. Unlike the classical approach, which makes use of lossless reciprocal matching networks, there is no need to trade-off the gain flatness with the input/output matching levels. In this contribution the flat gain condition is obtained partially by exploiting the mismatch loss at a certain section and partially by leveraging on ohmic losses. In particular, two different matching schemes have been analytically studied. Taking advantage of the more promising scheme of the two presented, the design of a linear power amplifier operating over the 4–40 GHz decade, is illustrated. The amplifier showed measured input/output return loss better than 9/10 dB respectively, a gain of 8 ± 0.6 dB and an output power level of 25.5 ± 0.5 dBm at 1 dB compression point. Incidentally, unconditional stability is obtained without considering additional stabilization networks or components devot...
Energies, 2021
This paper is focused on the extraction of the noise parameters of a linear active device by expl... more This paper is focused on the extraction of the noise parameters of a linear active device by exploiting both forward and reverse noise power measurements associated with different terminations. In order for load-pull measurements to yield a significant marginal improvement (as compared to forward measurements only) it is expected that the device under test should appreciably deviate from unidirectionality. For this reason, the source/load-pull technique is applied to frequencies at which the considered devices are still usable but their reverse noise factor exhibits a measurable dependence on the output terminations. Details on the test bench set up to the purpose, covering the 20–40 GHz frequency range, are provided. A characterization campaign on a 60 nm gate length, 4×35 µm GaN-on-Si HEMT fabricated by OMMIC is illustrated.
IEEE Transactions on Microwave Theory and Techniques, 2020
This article addresses the classical problem of determining the extrinsic resistances (<inline... more This article addresses the classical problem of determining the extrinsic resistances (<inline-formula> <tex-math notation="LaTeX">$R_{G}$ </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">$R_{S}$ </tex-math></inline-formula>, and <inline-formula> <tex-math notation="LaTeX">$R_{D}$ </tex-math></inline-formula>) of field-effect transistors (FETs) and, in particular, of high-electron-mobility transistors (HEMTs). The presented approach relies on small-signal measurements of open-channel transistors, as often proposed both for traditional metal–semiconductor FETs (MESFETs) and HEMTs. Unlike what is common practice with HEMTs, the method proposed here does not oversimplify the model of the active channel. On the contrary, we retrieve from the literature a possible analytical model for the open-channel HEMT and use it to determine the triplet of extrinsic resistances without the need of stressing the gate junction with too high currents. Another result of the approach, valid both for MESFETs and HEMTs, is a deterministic way to remove the contribution of the gate junction from the small-signal parameters of the measured devices. All extractions process data that are available on suitable ranges in frequency or in bias voltage, without taking to the limit the sweep parameters or seeking specific resonances. Also, optimizations are only allowed to refine the nominal values, not as the main technique of extraction. These goals are achieved by setting up different subproblems in the form of overdetermined linear systems and then solving by pseudoinversion. The validity of the approach is demonstrated on the measurements of devices from advanced HEMT technologies realized by OMMIC, both GaAs-based (40-nm gate length) and GaN-based (100 and 60 nm).
IEEE Transactions on Microwave Theory and Techniques, 2018
2015 10th European Microwave Integrated Circuits Conference (EuMIC), 2015
An extensive measurement campaign, including DC curves, S-parameters and noise factor has been ca... more An extensive measurement campaign, including DC curves, S-parameters and noise factor has been carried out on a 70 nm mHEMT technology (OMMIC's D007IH), both at ambient (300 K) and cryogenic (30 K) temperatures. For the first time, to the Authors' knowledge, the feasibility of the cold-source technique for on-wafer, cryogenic noise measurements is demonstrated. A scalable equivalent-circuit model, also equipped with noise parameters according to Pospieszalski's approach, has been extracted for the cryo-cooled devices. Comparisons between ambient and cryogenic operation are provided and discussed.
International Journal of Numerical Modelling: Electronic Networks, Devices and Fields, 2015
2015 10th European Microwave Integrated Circuits Conference (EuMIC), 2015
A novel, analytical treatment of noise factor in ideal transmission lines subjected to thermal gr... more A novel, analytical treatment of noise factor in ideal transmission lines subjected to thermal gradients is presented. Temperature dependence on the propagation direction is assumed linear, whereas line loss is considered uniform. Original formulae are presented allowing to compute line noise factor for arbitrary source terminations. A novel numerical implementation of the underlying theory is also presented both as an introduction to the Reader and as a test bench of the closed-form results.
2015 IEEE 16th Annual Wireless and Microwave Technology Conference (WAMICON), 2015
The present contribution summarizes the activities performed towards the realization of a Single-... more The present contribution summarizes the activities performed towards the realization of a Single-Chip Front-End (SCFE) operating in C Band, integrating the High Power, Low Noise amplification and switching functionalities to be provided in modern T/R modules' Front-Ends for space SAR applications. The technologies adopted in this project are provided by United Monolithic Semiconductors (UMS) and Selex Electronic Systems (SLX), the GH25-10 0.25 μm gate length and the GaN technology featured by 0.5 μm gate length for UMS and SLX respectively. At the completion of the design phase two SCFEs have been designed in the two technologies, each in two slightly different versions, featured by state-of-the-art performance. In particular, in Tx-mode, both are featured by approximately 40 W power output, with 36 dB large-signal gain and 38 % / 27 % PAE for UMS and SLX versions respectively, while in Rx-mode 2.5 dB noise figure resulted, with robust operation. The two dies are featured by 6.9 × 5.4 mm2 and 7.28 × 5.40 mm2 for UMS and SLX versions respectively.
2015 German Microwave Conference, 2015
A new active balun topology is introduced allowing to overcome gain and bandwidth limitations of ... more A new active balun topology is introduced allowing to overcome gain and bandwidth limitations of traditional out-of-phase power dividers. Proposed architecture employs distributed circuits as Artificial Transmission Line Pair (ATLP) and Split Drain Distributed Amplifier (SDDA) for achieving a broadband signal balancing and featuring a positive insertion gain too. In this contribution a complete theoretical analysis for the ATLP and SDDA principle of operation is provided together with the description of the actual design flow. MMIC test vehicle operating on the multi-octave frequency range 2-18 GHz proves the effectiveness of presented topology.
The present contribution summarizes the activities performed towards the realization of a Single-... more The present contribution summarizes the activities performed towards the realization of a Single-Chip Front-End (SCFE) operating in C Band, integrating the High Power, Low Noise amplification and switching functionalities to be provided in modern T/R modules’ Front-Ends for space SAR applications. The technologies adopted in this project are provided by United Monolithic Semiconductors (UMS) and Selex Electronic Systems (SLX), the GH25-10 0.25 μm gate length and the GaN technology featured by 0.5 μm gate length for UMS and SLX respectively. At the completion of the design phase two SCFEs have been designed in the two technologies, each in two slightly different versions, featured by state-of-the-art performance. In particular, in Tx-mode, both are featured by approximately 40 W power output, with 36 dB large-signal gain and 38 % / 27 % PAE for UMS and SLX versions respectively, while in Rx-mode 2.5 dB noise figure resulted, with robust operation. The two dies are featured by 6.9 x 5.4 mm2 and 7.28 x 5.40 mm2 for UMS and SLX versions respectively.
2022 17th European Microwave Integrated Circuits Conference (EuMIC)
2017 12th European Microwave Integrated Circuits Conference (EuMIC)
A D-band LNA is reported serving as a test vehicle of an under-development 40 nm GaAs HEMT techno... more A D-band LNA is reported serving as a test vehicle of an under-development 40 nm GaAs HEMT technology developed by OMMIC foundry. The amplifier, designed on the basis of custom small-signal equivalent-circuit models, is featured by state-of-the-art performance, and in particular has a noise figure as low as 4 dB at 140 GHz and a gain higher than 20 dB approximately from 115 GHz to 160 GHz. The main steps of the non-standard design flow are also illustrated, hinged on two main ideas: a closed-form analysis of the input/output matching bounds of the active devices, on the one hand, and an efficient optimization approach to shift the reference planes of EM-simulated networks, on the other.
IEEE Transactions on Circuits and Systems I: Regular Papers, 2021
The stability criteria based on the Rollett parameter (<inline-formula> <tex-math notati... more The stability criteria based on the Rollett parameter (<inline-formula> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula>) plus one auxiliary condition is yet the most popular method used by designers to evaluate the stability of a two-port network although other criteria are available. In this paper, novel analytical proofs of the criteria utilizing <inline-formula> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> and a new geometrical proof of the relationship between the stability of the ports of a circuit are proposed. They are obtained by making use of relationships between the reflection coefficients at the ports of the network and novel expressions that bind stability circles and unit mapping circles. The developed relations make the proposed proofs easier and more immediate than the traditional ones. Moreover, a new auxiliary condition having the same complexity and a greater geometrical insight with respect to the traditional ones is used.
IEEE Transactions on Circuits and Systems I: Regular Papers, 2021
This work is focused on the design of broadband amplifiers by exploiting dissipative reciprocal m... more This work is focused on the design of broadband amplifiers by exploiting dissipative reciprocal matching networks. Unlike the classical approach, which makes use of lossless reciprocal matching networks, there is no need to trade-off the gain flatness with the input/output matching levels. In this contribution the flat gain condition is obtained partially by exploiting the mismatch loss at a certain section and partially by leveraging on ohmic losses. In particular, two different matching schemes have been analytically studied. Taking advantage of the more promising scheme of the two presented, the design of a linear power amplifier operating over the 4–40 GHz decade, is illustrated. The amplifier showed measured input/output return loss better than 9/10 dB respectively, a gain of 8 ± 0.6 dB and an output power level of 25.5 ± 0.5 dBm at 1 dB compression point. Incidentally, unconditional stability is obtained without considering additional stabilization networks or components devot...
Energies, 2021
This paper is focused on the extraction of the noise parameters of a linear active device by expl... more This paper is focused on the extraction of the noise parameters of a linear active device by exploiting both forward and reverse noise power measurements associated with different terminations. In order for load-pull measurements to yield a significant marginal improvement (as compared to forward measurements only) it is expected that the device under test should appreciably deviate from unidirectionality. For this reason, the source/load-pull technique is applied to frequencies at which the considered devices are still usable but their reverse noise factor exhibits a measurable dependence on the output terminations. Details on the test bench set up to the purpose, covering the 20–40 GHz frequency range, are provided. A characterization campaign on a 60 nm gate length, 4×35 µm GaN-on-Si HEMT fabricated by OMMIC is illustrated.
IEEE Transactions on Microwave Theory and Techniques, 2020
This article addresses the classical problem of determining the extrinsic resistances (<inline... more This article addresses the classical problem of determining the extrinsic resistances (<inline-formula> <tex-math notation="LaTeX">$R_{G}$ </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">$R_{S}$ </tex-math></inline-formula>, and <inline-formula> <tex-math notation="LaTeX">$R_{D}$ </tex-math></inline-formula>) of field-effect transistors (FETs) and, in particular, of high-electron-mobility transistors (HEMTs). The presented approach relies on small-signal measurements of open-channel transistors, as often proposed both for traditional metal–semiconductor FETs (MESFETs) and HEMTs. Unlike what is common practice with HEMTs, the method proposed here does not oversimplify the model of the active channel. On the contrary, we retrieve from the literature a possible analytical model for the open-channel HEMT and use it to determine the triplet of extrinsic resistances without the need of stressing the gate junction with too high currents. Another result of the approach, valid both for MESFETs and HEMTs, is a deterministic way to remove the contribution of the gate junction from the small-signal parameters of the measured devices. All extractions process data that are available on suitable ranges in frequency or in bias voltage, without taking to the limit the sweep parameters or seeking specific resonances. Also, optimizations are only allowed to refine the nominal values, not as the main technique of extraction. These goals are achieved by setting up different subproblems in the form of overdetermined linear systems and then solving by pseudoinversion. The validity of the approach is demonstrated on the measurements of devices from advanced HEMT technologies realized by OMMIC, both GaAs-based (40-nm gate length) and GaN-based (100 and 60 nm).
IEEE Transactions on Microwave Theory and Techniques, 2018
2015 10th European Microwave Integrated Circuits Conference (EuMIC), 2015
An extensive measurement campaign, including DC curves, S-parameters and noise factor has been ca... more An extensive measurement campaign, including DC curves, S-parameters and noise factor has been carried out on a 70 nm mHEMT technology (OMMIC's D007IH), both at ambient (300 K) and cryogenic (30 K) temperatures. For the first time, to the Authors' knowledge, the feasibility of the cold-source technique for on-wafer, cryogenic noise measurements is demonstrated. A scalable equivalent-circuit model, also equipped with noise parameters according to Pospieszalski's approach, has been extracted for the cryo-cooled devices. Comparisons between ambient and cryogenic operation are provided and discussed.
International Journal of Numerical Modelling: Electronic Networks, Devices and Fields, 2015
2015 10th European Microwave Integrated Circuits Conference (EuMIC), 2015
A novel, analytical treatment of noise factor in ideal transmission lines subjected to thermal gr... more A novel, analytical treatment of noise factor in ideal transmission lines subjected to thermal gradients is presented. Temperature dependence on the propagation direction is assumed linear, whereas line loss is considered uniform. Original formulae are presented allowing to compute line noise factor for arbitrary source terminations. A novel numerical implementation of the underlying theory is also presented both as an introduction to the Reader and as a test bench of the closed-form results.
2015 IEEE 16th Annual Wireless and Microwave Technology Conference (WAMICON), 2015
The present contribution summarizes the activities performed towards the realization of a Single-... more The present contribution summarizes the activities performed towards the realization of a Single-Chip Front-End (SCFE) operating in C Band, integrating the High Power, Low Noise amplification and switching functionalities to be provided in modern T/R modules' Front-Ends for space SAR applications. The technologies adopted in this project are provided by United Monolithic Semiconductors (UMS) and Selex Electronic Systems (SLX), the GH25-10 0.25 μm gate length and the GaN technology featured by 0.5 μm gate length for UMS and SLX respectively. At the completion of the design phase two SCFEs have been designed in the two technologies, each in two slightly different versions, featured by state-of-the-art performance. In particular, in Tx-mode, both are featured by approximately 40 W power output, with 36 dB large-signal gain and 38 % / 27 % PAE for UMS and SLX versions respectively, while in Rx-mode 2.5 dB noise figure resulted, with robust operation. The two dies are featured by 6.9 × 5.4 mm2 and 7.28 × 5.40 mm2 for UMS and SLX versions respectively.
2015 German Microwave Conference, 2015
A new active balun topology is introduced allowing to overcome gain and bandwidth limitations of ... more A new active balun topology is introduced allowing to overcome gain and bandwidth limitations of traditional out-of-phase power dividers. Proposed architecture employs distributed circuits as Artificial Transmission Line Pair (ATLP) and Split Drain Distributed Amplifier (SDDA) for achieving a broadband signal balancing and featuring a positive insertion gain too. In this contribution a complete theoretical analysis for the ATLP and SDDA principle of operation is provided together with the description of the actual design flow. MMIC test vehicle operating on the multi-octave frequency range 2-18 GHz proves the effectiveness of presented topology.