RF co-designed bandpass filters/isolators (BPFIs) are based on series-cascaded non-reciprocal resonant stages, microwave resonators and multi-resonant cells. The non-reciprocal stages are shaped by an in-parallel cascaded transistor-based path and a transmission line (TL) that result in a zero-phase resonance in the forward direction and high isolation in the reversed one. This includes coupling routing diagrams (CRDs) of BPFs that result in low- and high-order transfer functions with and without transmission zeros in their forward direction and high levels of isolation in the reverse one. BPFIs provide alternative-type of filtering responses (e.g., flat-passband, quasi-elliptic) with and without gain in the forward direction and high levels of isolation in the reversed one. BPFIs include five planar microstrip/lumped element (LE) prototypes using hybrid combinations of non-reciprocal resonant stages, microwave resonators and multi-resonant cells.

A filter circuit includes a branch line coupler and a balun circuit having an input terminal connected to the branch line coupler to receive a signal, a first line connected to the input terminal and having a length comparable to a quarter of an electrical length of one wavelength at a frequency of the signal, a second line connected to the input terminal and having a length comparable to the quarter, a third line connected to the second line and having a length comparable to the quarter, and a fourth line connected to the third line and electromagnetically coupled to the first line, the fourth line having a length comparable to the quarter, wherein an end of the first line and an end of the fourth line are both connected to a ground or open-circuited, or are connected to two respective terminating resistors whose resistance values are equal.

This disclosure describes systems and methods for use with the design and implementation of bandpass filters for millimeter-wave applications. The filters can include an input port for receiving a signal from a signal generator, an output port, and a resonator. The resonator can be coupled between the input port and the output port. The resonator can have a T-shaped design.

A feeding structure is provided. The feeding structure includes a feeding unit, which includes: a reference electrode, first and second substrates opposite to each other, and a dielectric layer between the first and second substrates. The first substrate includes a first base plate and a first electrode thereon. The first electrode includes a first main body and a plurality of first branches connected to the first main body and spaced apart from each other. The second substrate includes a second base plate and a second electrode thereon. The second electrode includes a second main body and a plurality of second branches, which are connected to the second main body, spaced apart from each other, and in one-to-one correspondence with the plurality of first branches. Orthographic projections of each second branch and a corresponding first branch on the first base plate partially overlap each other.

Disclosed herein are multi-layer metal circuits, such as printed circuit boards (PCBs), with single-sided, partially-shielded, or fully-shielded via-less common-mode filters. The multi-layer metal circuits comprise at least one shield layer, at least one signal trace, and at least one reference layer (e.g., ground). The reference layer comprises a pattern of the via-less common-mode filter. The pattern may comprise, for example, a single piece-wise linear segment, or two or more disjoint and non-intersecting segments (which may be strictly linear or piece-wise linear). The reference layer is electrically isolated from the shield layer, and thus the via-less common-mode filters do not require vias. In addition to being used in PCBs, the disclosed multi-layer metal circuits may also be used in other applications, such as integrated circuits (e.g., implemented in semiconductor chips).

An electrically controllable RF-circuit element that includes at least one layer of an electrochromic material sandwiched between two corresponding layers of a solid-electrolyte material and placed adjacent and along a length of RF transmission line. In one example embodiment, the electrically controllable RF-circuit element operates as a tunable band-stop (e.g., notch) filter whose stop band can be spectrally moved by changing one or more dc-bias voltages applied across the corresponding layer stack(s). In another example embodiment, the electrically controllable RF-circuit element operates as a tunable phase shifter whose phase-shifting characteristics can be changed by changing one or more dc-bias voltages applied across the corresponding layer stack(s).

A tunable filter for adjustable filtering between a minimum frequency and a maximum frequency includes a transmission line designed to transmit a signal and having longitudinal axis. The tunable filter further includes a two-dimensional capacitor array including step-tunable capacitors located along the transmission line, a first dimension of the two-dimensional capacitor array being along the longitudinal axis and a second dimension of the two-dimensional capacitor array being located perpendicular to the longitudinal axis. The tunable filter further includes a controller coupled to each of the step-tunable capacitors and designed to control each of the step-tunable capacitors independently to be in a biased mode or in an unbiased mode based on a desired frequency response of the tunable filter.

Length matching and phase matching between circuit paths of differing lengths is disclosed. Two signals are specified to arrive at respective path destinations at a predetermined time and with a predetermined phase. An IC provides a first electronic signal over a first conductive path to a first destination and a second electronic signal over a second conductive path to a second destination. A first slow wave structure comprises the first conductive path and a second slow wave structure comprises the second conductive path. The effective relative permittivity of the first slow wave structure is tuned such that the first electronic signal arrives at its destination at a first time and at a first phase, and the effective relative permittivity of the second slow wave structure is tuned such that the second electronic signal arrives at its destination at a second time and at a second phase.

A filter circuit may include a transmission line, a quarter wave resonator, and an electrical component coupled in series with the quarter wave resonator at a first end and to the transmission line at a second end. The electrical component may be have a frequency dependent impedance. The electrical component may be an inductor, a capacitor, or an inductor in series with a capacitor. In another aspect, a filter circuit may include a transmission line, a first quarter wave resonator coupled to a first electrical component and a second quarter wave resonator coupled to a second electrical component. Each of the first and second electrical components may be coupled to the transmission line in parallel with each other. The first and the second electrical components may have a frequency dependent impedance. The first electrical component may be the same as or different from the second electrical component.

An interconnection system is described including a first printed circuit board, the first printed circuit board including a first portion of a filter, the filter used to communicate a signal between the first printed circuit board and a second printed circuit board, and a mechanical structure for coupling the signal between the first printed circuit board and the second printed circuit board, the second printed circuit board being oriented at an angle with respect to the first printed circuit board.