To address the practical challenges of satellite-assisted mobile communication for Internet-of-Things (IoT) devices—such as the needs for low-profile antennas, wide-angle beam steering under strict size and power constraints, and the limited tuning flexibility of conventional reconfigurable structures—this work proposes a compact dual-polarized antenna with digitally controlled pattern steering. The method combines mirror-image theory with transmission-optics-based phase regulation, enabling beam steering through a reconfigurable digital meta-surface that replaces the conventional ground plane. A planar dual-polarized dipole is positioned above the meta-surface, and beam steering is achieved by digitally switching the PIN-diode states to alter the discrete reflection-phase distribution. The prototype, fabricated and characterized at 12–14 GHz, demonstrates wide-angle beam steering with stable gain, low cross-polarization, and FPGA-based real-time digital control. The proposed approach provides a compact and energy-efficient solution for next-generation satellite-assisted IoT terminals requiring flexible and robust beam steering.

paper reports on the design and practical development of RF co-designed low-noise amplifiers (LNAs) with multi-band RF filter and diplexer capabilities. Split-type multi-resonant stages are used as complex-terminated matching networks to functionalize new classes of multi-band filtering LNAs (MBF-LNAs) and multi-band diplexer LNAs (MBD-LNAs). In this manner, the need for conventional matching networks or additional RF filtering is eliminated in the RF front-end, thus reducing its size. Miniaturization is further enhanced using split-type multi-resonant stages that are smaller than conventional transversal resonator arrays or filter-banks of in-line coupled resonators. The MBF-LNA and the MBD-LNA concepts are validated in S-band through the realization of two dual-band MBF-LNAs (MBF-LNA I and MBF-LNA II) and a quad-band MBD-LNA. Specifically, the MBF-LNA I exhibited a low noise figure (NF) of 0.65/0.9 dB and a gain of 19.1/16.5 dB for its passbands centered at 2.5/3.29 GHz. The MBFLNA II exhibited significantly higher isolation between the two passbands of 79.5 dB while having a NF of 1/1.5 dB and gain of 18.3/15.9 dB at 2.57/3.26 GHz. The MBD-LNA demonstrated two dual-band output channels with Channel 1 having a NF of 0.92/0.93 dB and gain of 17.2/15.2 dB at 2.38/3.29 GHz and Channel 2 having a NF of 0.82/1.02 dB and gain of 16.8/14.2 dB at 2.82/3.8 GHz.

This manuscript introduces a novel RF co-design methodology that allows to co-integrate the functionality of a single-/multi-band bandpass filter (BPF), an RF switch, a variable phase shifter (VP), a variable attenuator (VA), and an RF isolator within a single multi-functional RF component. It is based on a power reconfigurable rat-race coupler (RFRC), spatiotemporally modulated (STM) resonators and a switchable phase coupling element that controls three modes of operation. These include: 1) a co-designed single/multi-band reflectionless BPF, an RF isolator (enabled/disabled by turning ON/OFF STM) and a 360$^{\circ}$-variable phase shifter (BPF/BPFI-VP), 2) an RF switching mode and 3) a single/multi-band BPF, an RF isolator (enabled/disabled by turning ON/OFF STM) and a variable attenuator (BPF/BPFI-VA). A detailed theoretical framework is provided alongside a variety of single-band and multi-band design examples. The methodology is validated through the implementation of a single-band prototype (Prototype 1) and a dual-band prototype (Prototype 2) at 700 MHz. Specifically, Prototype 1 features a single-band BPF/BPFI-VP mode with continuously tunable phase shift of 360$^{\circ}$while having constant transfer function (TF), a wide reflectionless bandwidth (RBW) from 375 to 1093 MHz as well as uni-directional transmission with over 20 dB directivity ($D)$. When reconfigured in its BPF/BPFI-VA mode, a wide attenuation tuning range of 15.8 dB can be obtained with a well-preserved TF, low phase imbalance ($<$5$^{\circ})$and D$>$20 dB. Furthermore, it can be intrinsically switched-off with an isolation$>$30 dB. Prototype 2 supports a third order dual-band TF with 360$^{\circ}$tunable phase shift capability for both of its bands. Furthermore, it exhibits a RBW between 370-1200 MHz, switching-off capability with$>$30 dB of IS and with D$>$10 dB.

This paper introduces a detailed methodology for the realization of multi-functional transversal resonator-based non-reciprocal bandpass filters (NR-BPFs) that combine the functionality of a single-/multi-band BPF and an RF isolator. Directionality is achieved through spatiotemporal modulation (STM) whereas transfer function reconfigurability is obtained by only tuning the resonant frequency of its constituent resonators. A detailed design methodology to synthesize the response of transversal resonator-based STM arrays is introduced in this work for the first time, facilitating the synthesis of advanced RF filtering transfer functions based of transversal resonator arrays with incorporated directionality. The operating principles and scalability of the design method are demonstrated through the analysis of four distinct transversal resonator-based STM filtering topologies that facilitate the realization of high-order and highly-modular single-band and multi-band transfer functions with multiple levels of RF tuning including frequency tuning, bandwidth tuning, band controllability, and intrinsic switch-off capabilities. The concept has been validated at UHF band through the manufacturing and testing of four lumped-element NR-BPFs.

Two classes of frequency-reconfigurable multi-band negative-group-delay (NGD) circuit networks that feature low-input-power-reflection capabilities are reported. They consist of lossy-complementary-diplexer architectures, in which the NGD properties are obtained within the stopband regions of their lossy multi-band bandstop-filter (BSF) channel. Their complementary lossy multi-band bandpass-filter (BPF) branch absorbs in its terminating resistor the RF-input-signal energy that is not transmitted by the lossy multi-band BSF channel within its stopbands. In this manner, the input-reflectionless/absorptive behavior is realized. The theoretical foundations of the devised lossy-multi-band-BSF-based NGD structures using a coupling-routing-diagram formalism and single-to-multi-band admittance transformations are described. For the first-order case as illustration, guidelines for the synthesis in the bandpass frequency domain are provided. Furthermore, the extension of these multi-band NGD approaches to higher-order and in-series-cascade multi-stage realizations for more-general and wider-band NGD patterning, as well as to two-port/symmetrical designs, is shown. In addition, the conception of multi-functional passive components with NGD characteristics, such as wide-band BPFs and power directional couplers with embedded NGD regions, is also addressed. For experimental-demonstration purposes, an electronically-reconfigurable microstrip prototype of a two-stage-in-series-cascade dual-band NGD circuit is manufactured and measured.

A technique to design analog signal-interference narrow-band bandpass filters by merging transmission lines and surface-acoustic-wave (SAW) resonators is reported in this work. By inserting one-/two-port SAW resonators into the transversal filtering sections (TFSs) of the signal-interference filter, narrowband filtering actions with remarkable electrical properties can be synthesized. The latter particularly refers to the untypically-high effective unloaded quality factor (Qu) associated with the generated bandpass filtering response given its fully-planar realization. This leads to perceptible benefits in terms of in-band transmission loss and occupied physical area when compared to a classic pure signal-interference filter design. Moreover, for a given type of SAW resonator, adjustable bandwidth and transmission zeros (TZs) can be produced to attain a large variety of high-selectivity filtering functions. For practical validation, a three-stage microstrip narrow-band bandpass filter with measured S-parameters of a 433.9-MHz one-port SAW resonator is shown. The spurious-mode effect of the measured SAW resonator, as a limiting factor in the overall filter performance, is also discussed.