A resonator circuit, a filter with improved tunability, and a duplexer with improved tunability are disclosed. In an embodiment, the resonator circuit includes a resonator, a Z transformer and an impedance circuit, wherein the impedance circuit has an impedance Z and includes an impedance element, wherein the Z transformer is interconnected between the resonator and the impedance circuit, and wherein the Z transformer transforms the impedance Z to a new impedance ZZ and comprises a transformation circuit selected from: a generalized impedance converter (GIC), an negative impedance converter (NIC), a generalized impedance inverter (GII) and an negative impedance inverter (NII).

A resonator circuit, a filter with improved tunability, and a duplexer with improved tunability are disclosed. In an embodiment, the resonator circuit includes a resonator, a Z transformer and an impedance circuit, wherein the impedance circuit has an impedance Z and includes an impedance element, wherein the Z transformer is interconnected between the resonator and the impedance circuit, and wherein the Z transformer transforms the impedance Z to a new impedance ZZ and comprises a transformation circuit selected from: a generalized impedance converter (GIC), an negative impedance converter (NIC), a generalized impedance inverter (GII) and an negative impedance inverter (NII).

Reflectionless low-pass, high-pass, band-pass, band-stop, all-pass, all-stop, and multi-band filters, as well as a method for designing such filters is disclosed, along with a method of enhancing the performance of such filters through the use of unmatched sub-networks to realize an optimal frequency response, such as the Chebyshev equal-ripple response. These filters preferably function by absorbing the stop-band portion of the spectrum rather than reflecting it back to the source, which has significant advantages in many different applications. The unmatched sub-networks preferably offer additional degrees of freedom by which element values can be assigned to realize improved cutoff sharpness, stop-band rejection, or other measures of performance. The elements of the filter may be physical passive elements, or synthesized with active circuits, potentially realizing even negative element-values for improved performance.

Reflectionless low-pass, high-pass, band-pass, band-stop, all-pass, all-stop, and multi-band filters, as well as a method for designing such filters is disclosed, along with a method of enhancing the performance of such filters through the use of unmatched sub-networks to realize an optimal frequency response, such as the Chebyshev equal-ripple response. These filters preferably function by absorbing the stop-band portion of the spectrum rather than reflecting it back to the source, which has significant advantages in many different applications. The unmatched sub-networks preferably offer additional degrees of freedom by which element values can be assigned to realize improved cutoff sharpness, stop-band rejection, or other measures of performance. The elements of the filter may be physical passive elements, or synthesized with active circuits, potentially realizing even negative element-values for improved performance.

A switched mode negative inductance circuit includes an input node responsive to a voltage signal. The circuit also includes first and second voltage sources, first and second controlled switches having first poles coupled to the first and second voltage sources, respectively and an inductor having a first electrode coupled to second poles of the first and second controlled switches and a second electrode coupled to the input node. The input node is coupled to a control electrode of the first controlled switch, and to a control electrode of the second controlled switch through a voltage inverting circuit. The disclosure also illustrates balanced negative inductance circuits and implementation approaches using NMOS transistors.

There is disclosed a matching network for connecting an electrically small antenna to an RF source or load. The matching network includes a negative impedance converter, a pre-matching network for connecting the negative impedance converter to the antenna and a post-matching network for connecting the negative impedance converter to the RF source or load. The pre-matching network comprises a combination of capacitors and/or inductors to transform both a real part and an imaginary part of an impedance of the antenna. The negative impedance converter is configured to cancel the transformed imaginary part of the impedance of the antenna. The post-matching network comprises a combination of capacitors and/or inductors to transform a residual real part of the impedance of the antenna to match an impedance of the RF source or load. There is also disclosed an antenna system comprising a plurality of antenna radiating elements each having an associated feed, at least one of the feeds being connected to an RF source or load by way of an active matching circuit comprising a pre-matching network, a negative impedance converter and a post-matching network.

There is disclosed a matching network for connecting an electrically small antenna to an RF source or load. The matching network includes a negative impedance converter, a pre-matching network for connecting the negative impedance converter to the antenna and a post-matching network for connecting the negative impedance converter to the RF source or load. The pre-matching network comprises a combination of capacitors and/or inductors to transform both a real part and an imaginary part of an impedance of the antenna. The negative impedance converter is configured to cancel the transformed imaginary part of the impedance of the antenna. The post-matching network comprises a combination of capacitors and/or inductors to transform a residual real part of the impedance of the antenna to match an impedance of the RF source or load. There is also disclosed an antenna system comprising a plurality of antenna radiating elements each having an associated feed, at least one of the feeds being connected to an RF source or load by way of an active matching circuit comprising a pre-matching network, a negative impedance converter and a post-matching network.

A negative impedance circuit including: a first and a second bipolar transistors having a common collector, a base of the first transistor being connected to an emitter of the second transistor; a third and a fourth bipolar transistors having a common collector, a base of the third transistor being connected with an emitter of the fourth transistor; and at least one first impedance formed of one or of a plurality of passive components coupling the common collector of the first and second transistors to the common collector of the third and fourth transistors, a base of the second transistor being coupled to the collector of the third and fourth transistors and a base of the fourth transistor being coupled to the collector of the first and second transistors.

A negative impedance circuit including: a first and a second bipolar transistors having a common collector, a base of the first transistor being connected to an emitter of the second transistor; a third and a fourth bipolar transistors having a common collector, a base of the third transistor being connected with an emitter of the fourth transistor; and at least one first impedance formed of one or of a plurality of passive components coupling the common collector of the first and second transistors to the common collector of the third and fourth transistors, a base of the second transistor being coupled to the collector of the third and fourth transistors and a base of the fourth transistor being coupled to the collector of the first and second transistors.

A negative impedance circuit including: a first and a second bipolar transistors having a common collector, a base of the first transistor being connected to an emitter of the second transistor; a third and a fourth bipolar transistors having a common collector, a base of the third transistor being connected with an emitter of the fourth transistor, and at least one first impedance formed of one or of a plurality of passive components coupling the common collector of the first and second transistors to the common collector of the third and fourth transistors, a base of the second transistor being coupled to the collector of the third and fourth transistors and a base of the fourth transistor being coupled to the collector of the first and second transistors.