High frequency absorptive switch architecture
View Patent ↗An absorptive switch architecture suitable for use in high frequency RF applications. A switching circuit includes a common terminal and one or more ports, any of which may be selectively coupled to the common terminal by closing an associated path switch; non-selected, unused ports are isolated from the common terminal by opening an associated path switch. Between each path switch and a port are associated shunt switches for selectively coupling an associated signal path to circuit ground. Between each path switch and a port is an associated absorptive switch module. Each absorptive switch module includes a resistor coupled in parallel with a switch. The combination of the resistor and the switch of the absorptive switch module is placed in series with a corresponding signal path from each port to the common terminal, rather than in a shunt configuration.
1. A switching circuit including:
(a) a common terminal;
(b) one or more signal paths, wherein at least one signal path includes:
(1) a path switch connected in series with the common terminal and the signal path, for selectively coupling the signal path to the common terminal;
(2) at least one shunt switch connected between the signal path and circuit ground, for selectively coupling the signal path to the circuit ground;
(3) an absorptive switch module coupled in series with the path switch and a port, the absorptive switch module including a switch and a resistor coupled in parallel;
wherein the switch of the absorptive switch module has the characteristics of a resistor in a first state and of a capacitor in a second state, such that the absorptive switch module behaves as a resistor-capacitor network when the switch is in the second state, and the at least one shunt switch has the characteristics of an inductor-resistor network in a shunt switch first state and
wherein the resistor-capacitor network behavior of the absorptive switch module functions as a negative inductance that substantially offsets a positive inductive reactance behavior of the inductor-resistor network characteristics of the at least one shunt switch for signal frequencies within the range of about 1 to about 40 GHz.
2. An RF signal switching circuit, including:
(a) a common terminal;
(b) one or more signal paths for conducting RF signals, wherein at least one signal path includes:
(1) a path switch connected in series with the common terminal and the signal path, for selectively coupling the signal path to the common terminal;
(2) at least one shunt switch connected between the signal path and circuit ground, for selectively coupling the signal path to the circuit ground, wherein the at least one shunt switch has the characteristics of increasing imaginary inductive impedance and increasing real resistive impedance with increasing frequency;
(3) an absorptive switch module coupled in series with the path switch and a port, the absorptive switch module including a switch and a resistor coupled in parallel, wherein the absorptive switch module has the characteristics of a negative imaginary impedance with increasing magnitude with increasing frequency and a decreasing real impedance with increasing frequency;
wherein the negative imaginary impedance with increasing magnitude and the decreasing real impedance of the absorptive switch module respectively substantially offset the increasing imaginary inductive impedance and increasing real resistive impedance of the at least one shunt switch for signal frequencies within the range of about 1 to about 40 GHz.
3. An RF signal switching circuit embodied in an integrated circuit, including:
(a) a common terminal;
(b) one or more signal paths for conducting RF signals, wherein at least one signal path includes:
(1) a path switch connected in series with the common terminal and the signal path, for selectively coupling the signal path to the common terminal;
(2) at least one shunt switch connected between the signal path and circuit ground, for selectively coupling the signal path to the circuit ground, wherein the at least one shunt switch has the characteristics of increasing inductive impedance and increasing real resistive impedance with increasing frequency;
(3) an absorptive switch module coupled in series with the path switch and a port, the absorptive switch module including a FET switch and a resistor coupled in parallel, wherein the absorptive switch module has the characteristics of a negative imaginary impedance with increasing magnitude with increasing frequency and a decreasing real impedance with increasing frequency;
wherein the negative imaginary impedance with increasing magnitude and the decreasing real impedance of the absorptive switch module respectively substantially offset the increasing inductive impedance and increasing real resistive impedance of the at least one shunt switch for signal frequencies within the range of about 1 to about 40 GHz.
4. An RF signal switching circuit embodied in an integrated circuit, including:
(a) a common terminal;
(b) one or more signal paths for conducting RF signals, wherein at least one signal path includes:
(1) a path switch connected in series with the common terminal and the signal path, for selectively coupling the signal path to the common terminal;
(2) at least one shunt switch connected between the signal path and circuit ground, for selectively coupling the signal path to the circuit ground, wherein the at least one shunt switch has the characteristics of an inductor-resistor network in a shunt switch first state;
(3) an absorptive switch module coupled in series with the path switch and a port, the absorptive switch module including a FET switch and a resistor coupled in parallel, wherein the switch of the absorptive switch module has the characteristics of a resistor in a first state and of a capacitor in a second state, such that the absorptive switch module behaves as a resistor-capacitor network when the FET switch is in the second state;
wherein the resistor-capacitor network behavior of the absorptive switch module functions as a negative imaginary impedance that substantially offsets a positive imaginary impedance behavior of the inductor-resistor network characteristics of the at least one shunt switch for signal frequencies within the range of about 1 to about 40 GHz.
5. An absorptive switch module, configured to be coupled in series between a port and a path switch of an RF switching circuit, the RF switching circuit further including at least one shunt switch having the characteristics of increasing inductive impedance and increasing real resistive impedance with increasing frequency, the absorptive switch module including a FET switch and a resistor coupled in parallel, wherein the absorptive switch module has the characteristics of a negative imaginary impedance with increasing magnitude with increasing frequency and a decreasing real impedance with increasing frequency, and wherein the negative imaginary impedance with increasing magnitude and the decreasing real impedance of the absorptive switch module respectively substantially offset the increasing inductive impedance and increasing real resistive impedance of the at least one shunt switch for signal frequencies within the range of about 1 to about 40 GHz.
6. An absorptive switch module, configured to be coupled in series between a port and a path switch of an RF switching circuit, the RF switching circuit further including at least one shunt switch having the characteristics of an inductor-resistor network in a shunt switch first state, the absorptive switch module including a FET switch and a resistor coupled in parallel, wherein the absorptive switch module has the characteristics of a resistor in a first state and of a capacitor in a second state, such that the absorptive switch module behaves as a resistor-capacitor network when the FET switch is in the second state, and wherein the resistor-capacitor network behavior of the absorptive switch module functions as a negative imaginary impedance that substantially offsets a positive imaginary impedance behavior of the inductor-resistor network characteristics of the at least one shunt switch for signal frequencies within the range of about 1 to about 40 GHz.
7. A method for terminating one or more unused ports of an RF signal switching circuit embodied in an integrated circuit, including:
(a) providing a common terminal;
(b) providing one or more signal paths for conducting RF signals, wherein at least one signal path includes:
(1) a path switch connected in series with the common terminal and the signal path, for selectively coupling the signal path to the common terminal;
(2) at least one shunt switch connected between the signal path and circuit ground, for selectively coupling the signal path to the circuit ground, wherein the at least one shunt switch has the characteristics of increasing inductive impedance and increasing real resistive impedance with increasing frequency;
(3) an absorptive switch module coupled in series with the path switch and a port, the absorptive switch module including a FET switch and a resistor coupled in parallel, wherein the absorptive switch module has the characteristics of a negative imaginary impedance with increasing magnitude with increasing frequency and a decreasing real impedance with increasing frequency;
wherein the negative imaginary impedance with increasing magnitude and the decreasing real impedance of the absorptive switch module respectively substantially offset the increasing inductive impedance and increasing real resistive impedance of the at least one shunt switch for signal frequencies within the range of about 1 to about 40 GHz.
8. A method for terminating one or more unused ports of an RF signal switching circuit embodied in an integrated circuit, including:
(a) providing a common terminal;
(b) providing one or more signal paths for conducting RF signals, wherein at least one signal path includes:
(1) a path switch connected in series with the common terminal and the signal path, for selectively coupling the signal path to the common terminal;
(2) at least one shunt switch connected between the signal path and circuit ground, for selectively coupling the signal path to the circuit ground, wherein the at least one shunt switch has the characteristics of an inductor-resistor network in a shunt switch first state;
(3) an absorptive switch module coupled in series with the path switch and a port, the absorptive switch module including a FET switch and a resistor coupled in parallel, wherein the switch of the absorptive switch module has the characteristics of a resistor in a first state and of a capacitor in a second state, such that the absorptive switch module behaves as a resistor-capacitor network when the FET switch is in the second state;
wherein the resistor-capacitor network behavior of the absorptive switch module functions as a negative imaginary impedance that substantially offsets a positive imaginary impedance behavior of the inductor-resistor network characteristics of the at least one shunt switch for signal frequencies within the range of about 1 to about 40 GHz.
9. An RF signal switching circuit embodied in an integrated circuit, including:
(a) a common terminal means for communicating a signal to or from one or more signal paths;
(b) at least one path switch means, each connected in series with the common terminal and a corresponding signal path, for selectively coupling the corresponding signal path to the common terminal;
(c) a shunt switch means connected to an associated one of the at least one path switch means between the corresponding signal path of such path switch means and circuit ground, for selectively coupling the corresponding signal path to the circuit ground, wherein the shunt switch means has the characteristics of increasing imaginary inductive impedance and increasing real resistive impedance with increasing frequency;
(d) an absorptive switch means coupled in series between a port and at least one path switch means having a connected shunt switch means, the absorptive switch means including a resistor coupled in parallel with a FET switch, for providing a negative imaginary impedance with increasing magnitude with increasing frequency and a decreasing real impedance with increasing frequency;
wherein the negative imaginary impedance with increasing magnitude and the decreasing real impedance of the absorptive switch module respectively substantially offset the increasing inductive impedance and increasing real resistive impedance of the associated at least one shunt switch for RF signal frequencies within the range of about 1 to about 40 GHz.
10. An RF signal switching circuit embodied in an integrated circuit, including:
(a) a common terminal means for communicating a signal to or from one or more signal paths;
(b) at least one path switch means, each connected in series with the common terminal and a corresponding signal path, for selectively coupling the corresponding signal path to the common terminal;
(c) a shunt switch means connected to an associated one of the at least one path switch means between the corresponding signal path of such path switch means and circuit ground, for selectively coupling the corresponding signal path to the circuit ground and having the characteristics of an inductor-resistor network in a shunt switch means first state;
(d) an absorptive switch means coupled in series between a port and at least one path switch means having a connected shunt switch means, the absorptive switch means including a resistor coupled in parallel with a FET switch, wherein the FET switch of the absorptive switch means has the characteristics of a resistor in a first state and of a capacitor in a second state, for behaving as a resistor-capacitor network when the FET switch is in the second state;
wherein the resistor-capacitor network behavior of the absorptive switch means functions as a negative imaginary impedance that substantially offsets a positive imaginary impedance behavior of the inductor-resistor network characteristics of the associated at least one shunt switch for RF signal frequencies within the range of about 1 to about 40 GHz.