Integrated and combined phase shifter and isolation switch
A phase shifter unit cell or a connected set of such cells that can be well isolated from external circuitry and which do not introduce insertion loss into an RF signal path, exhibit good return loss, and further provides additional advantages when combined with bracketing attenuator circuits. More particularly, embodiments integrate a high-isolation function within a phase shifter circuit by breaking the complimentary nature of the control signals to a phase shifter cell to provide greater control of switch states internal to the phase shifter cell and thus enable a distinct high-isolation state, and by including a switchable shunt termination resistor for use in the high-isolation state. Some embodiments are serially coupled to attenuator circuits to enable synergistic interaction that reduces overall die size and/or increases isolation. One such embodiment positions a high-isolation phase shifter cell in accordance with the present invention between bracketing programmable attenuators.
1. A digitally-controlled multi-path phase shifter, including:
(a) a plurality of phase shift signal paths, each phase shift signal path coupled at a first end to a first port and at a second end to a second port, configured to provide a phase shift to a signal applied to at least one of the first port and the second port, and responsive to a corresponding independent path selection control signal to selectively independently enable communication of the applied signal between the first port and the second port through the corresponding phase shift signal path when not in an isolation mode, and disable communication of the applied signal between the first port and the second port through the corresponding phase shift signal path when in the isolation mode; and
(b) at least one selectable termination circuit, each operatively coupled to a corresponding one of the first port or the second port, and responsive to a distinct isolation circuit control signal to isolate the first port and the second port from each other in the isolation mode.
2. The phase shifter of claim 1 , wherein the at least one selectable termination circuit includes a first selectable termination circuit coupled between circuit ground and the first port, and a second selectable termination circuit coupled between circuit ground and the second port.
3. The phase shifter of claim 1 , wherein at least one phase shift signal path of the plurality of phase shift signal paths includes at least one isolation switch serially coupled to one of the first port or the second port, and at least one phase shifter element serially coupled to the at least one isolation switch.
4. The phase shifter of claim 3 , wherein at least one selectable termination circuit of the at least one selectable termination circuit is coupled between circuit ground and a corresponding one of the first port or the second port through at least one corresponding isolation switch.
5. The phase shifter of claim 3 , wherein at least one selectable termination circuit of the at least one selectable termination circuit is coupled between circuit ground and a corresponding one of the first port or the second port through a corresponding phase shifter element.
6. The phase shifter of claim 1 , wherein the applied signal is a radio frequency signal.
7. The phase shifter of claim 1 , wherein the distinct isolation circuit control signal is derived from a logical combination of the independent path selection control signals.
8. A digitally-controlled multi-path phase shifter, including:
(a) a plurality of phase shift signal paths, each phase shift signal path coupled at a first end to a first port and at a second end to a second port, and configured to provide a phase shift to a signal applied to at least one of the first port and the second port;
(b) at least one selectable termination circuit, each operatively coupled to a corresponding one of the first port or the second port, and responsive to a distinct isolation circuit control signal to isolate the first port and the second port from each other in an isolation mode; and
(c) a plurality of independent path selection control signals, each independent path selection control signal coupled to a corresponding one of the plurality of phase shift signal paths, each independent path selection control signal selectively independently enabling communication of the applied signal between the first port and the second port through the corresponding phase shift signal path when not in the isolation mode, and each independent path selection control signal disabling communication of the applied signal between the first port and the second port through the corresponding phase shift signal path when in the isolation mode.
9. The phase shifter of claim 8 , wherein the at least one selectable termination circuit includes a first selectable termination circuit coupled between circuit ground and the first port, and a second selectable termination circuit coupled between circuit ground and the second port.
10. The phase shifter of claim 8 , wherein at least one phase shift signal path of the plurality of phase shift signal paths includes at least one isolation switch serially coupled to one of the first port or the second port, and at least one phase shifter element serially coupled to the at least one isolation switch.
11. The phase shifter of claim 10 , wherein at least one selectable termination circuit of the at least one selectable termination circuit is coupled between circuit ground and a corresponding one of the first port or the second port through at least one isolation switch.
12. The phase shifter of claim 10 , wherein at least one selectable termination circuit of the at least one selectable termination circuit is coupled between circuit ground and a corresponding one of the first or second ports through a corresponding phase shifter element.
13. The phase shifter of claim 8 , wherein the applied signal is a radio frequency signal.
14. The phase shifter of claim 8 , wherein the distinct isolation circuit control signal is derived from a logical combination of the independent path selection control signals.
15. A phase shifter including at least one phase shifter unit cell, the at least one phase shifter unit cell including:
(a) a plurality of phase shift signal paths, each phase shift signal path including at least one phase shifter element serially coupled through at least one isolation switch to a first port and a second port, and configured to provide a selectable degree of phase shift to a radio frequency signal applied to at least one of the first port or the second port;
(b) a plurality of independent path selection control signals, each independent path selection control signal coupled to a corresponding one of the plurality of phase shift signal paths, and configured to selectively couple the corresponding phase shift signal path to the first port and the second port;
(c) at least one selectable termination circuit, each coupled between circuit ground and a corresponding one of the first port or the second port; and
(d) a distinct isolation circuit control signal, coupled to each selectable termination circuit, configured to switch the at least one termination circuit to an isolation mode to operationally couple the corresponding one of the first port or the second port to circuit ground, and to switch the at least one termination circuit to a phase shifting mode by de-coupling the corresponding one of the first port or the second port from circuit ground;
wherein, in the isolation mode, the plurality of independent path selection control signals are set to states that effect isolation of the corresponding phase shift signal path from the first port and the second port.
16. The phase shifter of claim 15 , wherein the at least one selectable termination circuit includes a first selectable termination circuit coupled between circuit ground and the first port, and a second selectable termination circuit coupled between circuit ground and the second port.
17. The phase shifter of claim 15 , wherein at least one phase shift signal path of the plurality of phase shift signal paths includes a first isolation switch serially coupled to one of the first port or the second port, at least one phase shifter element serially coupled to the first isolation switch, and a second isolation switch serially coupled to the at least one phase shifter element and to the other of the first port or the second port.
18. The phase shifter of claim 15 , wherein at least one selectable termination circuit of the at least one selectable termination circuit is coupled between circuit ground and a corresponding one of the first port or the second port through at least one isolation switch.
19. The phase shifter of claim 15 , wherein at least one selectable termination circuit of the at least one selectable termination circuit is coupled between circuit ground and a corresponding one of the first port or the second port through a corresponding phase shifter element.
20. The phase shifter of claim 15 , wherein the distinct isolation circuit control signal is derived from a logical combination of the at least two independent path selection control signals.