This paper presents tunable 2- and 4-pole bandpass filters with a wide tuning range based on dual zero-value couplings. The zero-value coupling is achieved using a coupled line with two coupling paths. The proposed filter also has bandwidth tunability. Frequency and bandwidth tunings are achieved using silicon varactor diodes. Three types of tunable filters are designed and built on a substrate with ε r = 3.55 and h = 25 mil, two filters with two separate frequency bands (2- and 4-pole: Filter A) and one filter with contiguous frequency tuning (4-pole: Filter B). The 2-pole filter results in an insertion loss of 2.9-4.7 dB with a tuning range of 0.75-1.09 and 1.70-2.18 GHz. Filter A with a 4-pole response results in an insertion loss 3.7-7.9 dB and a -1-dB bandwidth of 68-87 MHz with a tuning ranges of 0.77-1.10 and 1.70-2.10 GHz. Filter B shows an insertion loss of 4.4-6.6 dB and a -1-dB bandwidth of 39-68 MHz with a tuning range of 0.70-1.44 GHz. The application areas are in wideband tunable filters requiring contiguous and noncontiguous frequency coverage with bandwidth tunability in separate bands.

Cognitive radios require tunable band-switchable bandpass filters to respond to the dynamically changing operating frequencies in cognitive systems. This study presents a novel switchable dual-/single-band tunable bandpass filter using a single switchable J -inverter. The proposed filter configuration can be easily converted from a two-pole dual-passband mode to a four-pole single-passband mode using the single J-inverter with switches. This is achieved through a novel dual-band bandpass filter configuration using hybrid resonators that consist of two parallel resonators and one J-inverter. In addition, two bandwidths and two center frequencies of the dual-passband mode are designed, and a high stopband attenuation level is achieved due to a transmission zero between the two passbands. The proposed filter is built on a Duroid substrate with a dielectric constant of 3.48 and a thickness of 30 mil. The tuning of the center frequency and the passband number change are carried out using silicon varactors and PIN diodes. In the four-pole single-passband mode, a center frequency tuning of 0.75-1.08 GHz is achieved with 1-dB bandwidths of 105-158 MHz. The two-pole dual-band bandpass filter mode has a center frequency tuning of 0.69-0.9 GHz (low-band) and 0.85-1.07 GHz (high-band). It has potential for application in wideband cognitive radios.

In this letter, we present a simple design method for dual-band bandpass filters (BPFs) with two independently controllable bandwidths. The proposed design is based on hybrid resonators which have both series and shunt resonances. For compact size, an interdigital BPF type is utilized. The simple design procedures are established based on an equivalent lumped circuit of the proposed dual-band BPF. Moreover, the proposed BPF has good skirt characteristics through transmission zeros created by the series resonance in the hybrid resonator and the cross-coupling. The third-order dual-band BPF is designed at center frequencies of 1.85 and 2.85 GHz with fractional bandwidths of 11% and 7.3%.

This study investigates a novel approach to robotic arm control through integrating spiking neural networks with the twin delayed deep deterministic policy gradient reinforcement learning algorithm. Specifically, it presents the first application of spiking neural networks-based twin delayed deep deterministic policy gradient in 3D robotic manipulation, demonstrating its extension from traditional 2D tasks to complex 3D target-reaching scenarios with improved energy efficiency and stability. Additionally, with the inertial measurement unit data the system successfully mimics human arm movements, achieving a success rate of 0.95 among 50 trials and enabling an intuitive and accurate human–robot interaction system. This pioneering attempt highlights the feasibility of combining the biologically inspired spiking neural networks with the reinforcement learning algorithm to address the real-time challenges in high-dimensional robotic environments and advance the field of human–robot interaction systems.

The ever-growing field of wireless communication requires efficient radio frequency transceivers with tunable absorptive bandstop filters that can prevent the interference of out-of-band and reflected signals. This paper presents 4-pole tunable absorptive bandstop filters using folded coupled-lines with an inductor. A 4-pole filter transfer function is achieved to obtain an absorptive bandstop filter coupling diagram with 45° electrical-length transmission-line source/load coupling. The folded-loaded coupled-lines with an inductor are proposed to obtain the control for the required coupling coefficients based on the filter transfer functions. The required quality factor extracted through the transfer function is accomplished using a distributed resonator loaded with asymmetrical varactors without auxiliary circuits, such as an impedance-matching network. Two types of filters were designed and built on a substrate with ε _r = 3.42 and h = 30 mil. The center frequency tuning was performed using silicon varactors. The first filter shows a return loss of 16.2–38 dB and a rejection level of 41–48 dB in the tuning range 0.83–1.09 GHz. The second filter results in a measured return loss of 14–34 dB and a rejection level of 40.1–51 dB at 1.16–1.47 GHz. 4-pole tunable absorptive bandstop filters with high attenuation and reflectionless responses were achieved which have applications in cognitive radios and carrier aggregation systems.