Mirko Palomba

A novel hybrid active quasi-circulator for L-band applications

In this contribution a hybrid active quasi-circulator operating in L-Band is presented. E-pHEMT active devices mounted on ceramic substrate with copper metallization have been used. The proposed quasi-circulator is composed by active non-reciprocal phase shifters and classical passive combining structures to get the desired functionality. Insertion losses better than 2.1 dB, isolation higher than 20 dB in the 1.35 ÷ 1.65 GHz frequency band is obtained, while an isolation better than 30 dB over a 15% bandwidth. Port matching is better than 15 dB on couplers ports, while the splitter one reaches 10 dB. The overall quasi-circulator exhibits a 22 % operating bandwidth.

High-density mixed signal RF front-end electronics for T-R modules

In this contribution, several Multi-Functional Chips featuring different functionalities and integration levels are presented. A X-Band Core-Chip integrating a 6-bit attenuator, a 6-bit phase shifter, a T/R switch and a digital serial-to-parallel converter has been fabricated with 0.18 μm OMMIC ED02AH process. The MMIC exhibits 6 dB and 8 dB average insertion gain for transmit and receive mode respectively, full 360° phase coverage with 5.6° phase steps and 31.5 dB attenuation dynamic range with 0.5 dB amplitude resolution in less than 16 mm2. Two C-Band Multi-Functional Chips, one consisting of a bidirectional 6-bit phase shifter with on-board digital controls and the other integrating a 6-bit phase shifter, a buffer amplifier and a 5-bit attenuator have been fabricated with the 0.4 μm E/D GaAs process developed by SELEX Sistemi Integrati. The former exhibits full 360 degree phase coverage with 5.6° phase resolution in less than 18 mm2. The latter is an unidirectional MMIC featuring 8 dB average gain, full 360 degree phase coverage with 5.6° phase steps and 31 dB attenuation range with 1 dB amplitude resolution in less than 26 mm2.

Novel broadband nonreciprocal 180° phase-shifter

In this contribution, a novel broadband 180° phase shifter, realized in 0.5 μm GaN HEMT technology developed by SELEX Sistemi Integrati, is presented. This new topology is based on the combination of two directive three-port elements with a four-port phase-shifting network: the proposed MMIC is featured by an average zero insertion loss, 180°±2° differential phase-shift and good port matching over the 3-7GHz operating bandwidth. The MMIC size is 3.5×3.4 mm².

Automated extraction of device noise parameters based on multi-frequency, source-pull data

In this paper a novel approach for determining the four noise parameters of FET devices over frequency is presented. Such methodology is made of two parts: the first one allows to straightforwardly extract single-frequency noise parameters from source-pull data; the second one extends this capability to multi-frequency, source-pull data to obtain a full description of device noise behavior over frequency by means of at most 10 constant parameters (depending on the required accuracy). The whole process is automated via a software routine and does not need a previous knowledge of the FET equivalent circuits topology, or the values of its elements. This peculiarity makes the proposed method very well suited to quick characterization campaigns of active devices, avoiding the burden of a whole set of prior, different measurements and the relevant, critical extraction procedures, which are strongly dependent on the device.

An ultra-broadband 2–8 GHz GaN HEMT MMIC active combiner

In this contribution, a broadband active out-of-phase combiner designed in 0.5 μm GaN-HEMT technology developed by SELEX Sistemi Integrati is presented. The proposed MMIC is based on a distributed approach: exploiting the Drain line sharing, a dummy section and a single stage distributed amplifier, a 13.5 dB average differential gain, together with better than 10 dB input and output return losses and a CMRR better than 30 dB over the 2-8 GHz operating bandwidth are attained. The MMIC size is 2.9×3.3 mm2.

Verifying Rollett’s Proviso on Active Devices Under Arbitrary Passive Embeddings

Some results implicit in Ohtomo’s original paper are reappraised and built upon to help high-frequency circuit designers avoid common misconceptions. An analysis of the small-signal stability of an intrinsic device is presented, based on a closed-form evaluation of the network determinant in admittance representation and on the relevant Nyquist plot. Since the intrinsic is studied as a three-port, the proposed method represents a rigorous tool for checking the fulfillment of the inherent-stability proviso under arbitrary passive embeddings. Conversely, the proviso is often simply assumed to hold, which can in principle lead to mistakenly predicted circuit stability, or even unconditional stability. Examples of the proposed graphical analysis are provided both for the intrinsic circuit of an actual device and for a modified version thereof, i.e., suitably tweaked for illustrative purposes. The latter example is then expanded to give the reader a full picture of the small-signal stability analysis process, both in a flawed and a correct form.

Resistive bias network for optimized isolation in SPDT switches

Classical Series-Shunt and T-shape SPDTs provide an isolation degrading in frequency which, to be adequately counteracted, may require high-value (and, therefore, large-size) resonating inductors. In this contribution, a resistive bias network is added to a T-shape SPDT instead of introducing inductors. A derived analytical description evidences that the maximum isolation can be shifted in frequency by selecting the proper resistive values. Such an architecture offers high isolation values and, at the same time, considerable area savings as compared to the inductor-based approach. A test circuit operating in S-Band was designed and a 72 dB isolation was achieved, as well as a return loss of about 20 dB.

Reconfigurable matching network for RF energy harvesting circuits

This work is aimed to acquire knowledge on the RF/DC conversion process, based on hybrid technology and using a reconfigurable matching network. For this purpose, a test circuit operating at UHF TV broadcasting frequencies is designed, realized and measured for different frequencies, input power levels and load values.

High spectral purity X- to W-band active GaAs monolithic frequency multiplier

In this contribution, an active high harmonic suppression x8 frequency multiplier using depletion-mode mHEMT devices and its design procedure are presented. The realized circuit exhibits 3 dB conversion gain in the 86.4 - 91.2 GHz output frequency range, with 6 dBm output power. An harmonic suppression higher than 32 dBc has been achieved. The whole chip current consumption is 125 mA, occupying an area of 2.05 × 3.45 mm2.

A novel current-reuse architecture demonstrated on a two-stage GaN-on-SiC LNA

An original implementation of the current-reuse concept is presented, specifically conceived to be applied to microwave cascaded single-ended amplifiers and, unlike most examples from the literature, not requiring that the inter-stage networks be implemented in specific topologies. To demonstrate the viability of the proposed architecture, two X-band two-stage 0.5 μm GaN-on-SiC amplifiers are designed, namely a baseline version, featured by a standard DC network, and a current-reuse version, only differing in that it adopts the presented architecture. Comparing the two designs shows that this current-reuse approach can be applied to a generic cascaded single-ended amplifier with negligible impact on chip size and RF performance. Measurements on realized prototypes are in line with what achievable in the technology at hand over the whole X-band.