Aintzane Lujambio

This letter presents the design and characterization of a Ka-band low-noise-amplifier (LNA) monolithic microwave integrated circuit (MMIC) implemented on a 70-nm gallium nitride (GaN)-on-SiC high-electron-mobility transistor (HEMT) process. The three-stage LNA combines microstrip and coplanar technologies to minimize the losses before the first transistor and shows an average small-signal gain of $25~\pm ~2.5$ dB and an average noise figure (NF) of 1.3 dB from 27 to 40 GHz, with a dc power consumption of 0.311 W. The MMIC was also subject to large signal testing, exhibiting an output power at 1-dB gain compression of 9.9 dBm at 35 GHz and surviving an overdrive continuous wave signal at 26 GHz with a power of up to +25 dBm with no significant S-parameter performance degradation. To the best of our knowledge, this is the first demonstration of a Ka-band MMIC LNA in GaN with average NF 1.3 dB from 27 to 40 GHz.

A new dual-band balanced bandpass filter based on magnetically coupled open-loop resonators in multilayer technology is proposed in this paper. The lower differential passband, centered at the Global Positioning System (GPS) L1 frequency, 1.575 GHz, was created by means of two coupled resonators etched in the middle layer of the structure, while the upper differential passband, centered at a Wi-Fi frequency of 2.4 GHz, was generated by coupling two resonators on the top layer. Magnetic coupling was used to design both passbands, leading to an intrinsic common-mode rejection of 39 dB within the lower passband and 33 dB within the upper passband. Simulation and measurement results are provided to verify the usefulness of the proposed dual-band differential bandpass filter.

A compact, balanced, dual‐band bandpass filter with flexible and independent control of the differential‐mode response is presented in this study. The filtering mechanism relies on the use of magnetically coupled embedded resonators. This provides two clear advantages: high level of miniaturisation and two differential‐mode passbands that can be independently tuned. The response of the differential‐mode is controlled by the external quality factor and coupling coefficients, whereas the common‐mode is inherently rejected thanks to the use of a magnetic coupling mechanism. In order to illustrate the benefits of this structure, a prototype example is designed, fabricated and measured. Good differential‐ and common‐mode performance has been obtained.

Two balanced-to-balanced planar diplexers based on magnetically coupled microstrip resonators are proposed in this paper. For the first prototype, each channel/differential-output is composed of a second order single-band balanced bandpass filter based on open-loop resonators. For the second diplexer example, the filters composing the differential outputs are fourth order and are implemented by means of folded stepped-impedance resonators. The design procedure for the differential response is quite straightforward, since it is based on the use of the well-known external quality factor and coupling coefficients concepts. Common-mode is inherently rejected thanks to the benefits of magnetic coupling, which precludes common-mode transmission over a wide frequency range. The proposed structure also offers a high level of channel-to-channel isolation. To demonstrate the usefulness of the proposed idea, the two prototypes are simulated, fabricated, and measured. Good differential-mode and common-mode performance is observed in both examples. Simulations and measurements show good agreement.

A compact balanced-to-balanced diplexer composed of two balanced bandpass filters is proposed in this letter. The balanced filters are implemented using compact edge-coupled square split-ring resonators. The design methodology is based on the standard coupled-resonators filter synthesis procedure. First, each filter is independently designed. Then, they are connected to a common differential input port in order to achieve the desired diplexing operation, with the pertinent adjustments to take into account the loading effect of the second filter. Magnetic coupling inherently prevents common-mode transmission. An illustrative prototype example is provided with simulations and measurements to demonstrate the benefits of the proposed topology.

A new differential periodic transmission line with broad common-mode suppression is presented. The unit cell consists of a hybrid microstrip-coplanar waveguide structure involving two symmetrical edge-coupled microstrip lines coupled to a coplanar waveguide resonator etched in the ground plane. Transmission-line models have been used to analyze the structure response in both the differential and common modes. The device exhibits all-pass characteristics under differential-mode operation and a bandstop response for the common-mode signal. A Bloch-Floquet analysis allows for the prediction of the required common-mode rejection band. Good agreement has been found between measurements, electromagnetic simulations and analytical results.

From our first proposals of periodic Photonic Bandgap (PBG) structures in microstrip to the complex Inverse Scattering synthesis methods that we use nowadays and that give rise to synthesized structures with smooth profiles in microwave planar or waveguide technology, the UPNA Microwave Components Group (MCG-UPNA) has made significant contributions to the microwave theory (partially related to previous optical developments) and has also made several proposals of applications that will be reviewed in this paper from an historical perspective. Our group is a multidisciplinary group, focused also on the industry needs.

A symmetrical pair of differential microstrip lines implemented in hybrid microstrip/coplanar waveguide (CPW) technology is proposed. Transmission-line models are used to analyze differential- and common-mode responses, allowing efficient design with minimal optimization effort. The structure behaves as a conventional transmission line pair under differential-mode excitation, whereas asymmetrical coupled transmission line theory has to be applied to characterize common-mode operation. The common mode is strongly suppressed thanks to the introduction of a controllable transmission zero. A two-stage version of the structure is used to increase the common-mode rejection bandwidth. All the electrical parameters of the transmission lines have been obtained using an in-house fast quasi-TEM code. The good agreement between transmission-line models, full-wave simulations and measurements confirms the benefits of the structure and the design procedure.

A new compact balanced dual-band bandpass filter based on coupled-embedded resonators with modified ground plane is presented in this work. Common-mode is rejected within the two differential passbands by symmetrically introducing four coupled U-shaped defected ground structures below the resonators. Common-mode rejection is significantly improved when compared with the standard (solid ground plane) filter with similar geometry thanks to the introduction of four extra transmission zeros. Due to the symmetry, the differential mode is not significantly affected by the presence of the U-shaped resonators. Circuit-model data, full-wave simulations and measurements are provided to verify the benefits of the proposed dual-band filter.