Methods and devices for overcoming insertion loss in RF systems
Methods and devices are described for overcoming insertion loss notches in RF systems. In one case programmable impedances are used to move an insertion loss notch outside a frequency band of interest.
1. A radio frequency (RF) circuital arrangement comprising:
a first RF path comprising one or more RF devices;
a second RF path comprising a configurable impedance network and one or more RF devices;
an antenna; and
an antenna switch connected to a first node of the first RF path and to a second node of the second RF path, the antenna switch configured to selectively couple the first node and the second node to the antenna,
wherein in a first mode of operation of the RF circuital arrangement:
(i) the antenna switch provides a low impedance resistive coupling between the first node and the antenna,
(ii) the antenna switch provides a high impedance capacitive coupling between the second node and the antenna, so that an impedance of the second RF path seen at the second node is capacitively coupled to the first node, and
(iii) the configurable impedance network of the second RF path is configured to affect the impedance seen at the second node so as to shift a resonance frequency of a resonance effect at the first node due to the capacitive coupling of the impedance seen at the second node to the first node.
2. The RF circuital arrangement according to claim 1 , wherein the resonance frequency of the resonance effect at the first node due to the capacitive coupling of the impedance seen at the second node to the first node is within a frequency band of the RF signal.
3. The RF circuital arrangement according to claim 2 , wherein the configurable impedance network of the second RF path is configured to shift the resonance frequency outside the frequency band of the RF signal.
4. The RF circuital arrangement according to claim 2 or claim 3 , wherein the resonance effect affects an insertion loss of the RF signal within the frequency band of the RF signal.
5. The RF circuital arrangement according to claim 4 , wherein the resonance effect increases the insertion loss of the RF signal within the frequency band of the RF signal.
6. The RF circuital arrangement according to claim 4 , wherein the configurable impedance network of the second RF path is configured to reduce the insertion loss of the RF signal within the frequency band of the RF signal.
7. The RF circuital arrangement according to claim 4 , wherein the frequency band is approximately 0.2 GHz wide and the reduction of the insertion loss is equal to or larger than 2 dB in magnitude.
8. The RF circuital arrangement according to claim 1 , wherein the configurable impedance network comprises a combination of one or more of: a) an RF switch, b) a resistor, and c) a reactive impedance.
9. The RF circuital arrangement according to claim 8 , wherein the RF switch is a stacked transistor switch comprising one or more stacked FET transistors.
10. The RF circuital arrangement according to claim 9 , wherein a number of the one or more stacked FET transistors of the stacked transistor switch is based on a desired voltage handling capability of the stacked transistor switch.
11. The RF circuital arrangement according to claim 9 , wherein a size of a transistor of the one or more stacked FET transistors is based on a desired current handling capability of the stacked transistor switch.
12. The RF circuital arrangement according to claim 8 , wherein the resistor is a variable resistor or a digitally tunable resistor.
13. The RF circuital arrangement according to claim 8 , wherein the reactive impedance is a digitally tunable capacitor (DTC) or a digitally tunable inductor (DTL).
14. The RF circuital arrangement according to claim 8 , wherein the arrangement is monolithically integrated on a same integrated circuit.
15. The RF circuital arrangement according to claim 1 , wherein an RF device of the one or more RF devices comprises one of a) a duplexer, b) a diplexer, c) a switch, d) a low noise amplifier, e) a power amplifier, f) a reactive element, and g) a resistive element.
16. The RF circuital arrangement according to claim 1 , wherein the second RF path further comprises one or more additional configurable impedance networks coupled to the one or more RF devices and configured to further affect the impedance seen at the second node.
17. The RF circuital arrangement according to claim 1 , wherein the first RF path further comprises a configurable impedance network,
wherein in a second mode of operation of the RF circuital arrangement:
the antenna switch provides a low impedance resistive coupling between the second node and the antenna,
the antenna switch provides a high impedance capacitive coupling between the first node and the antenna, so that an impedance of the first RF path seen at the first node is capacitively coupled to the second node, and
the configurable impedance network of the first RF path is configured to affect the impedance seen at the first node so as to shift a resonance frequency of a resonance effect at the second node due to the capacitive coupling of the impedance seen at the first node to the second node.
18. The RF circuital arrangement according to claim 17 , wherein in the first mode of operation:
the configurable impedance network of the first RF path provides a capacitive coupling between the first node and a reference ground, and
the configurable impedance network of the second RF path provides a resistive coupling between the second node and the reference ground.
19. The RF circuital arrangement according to claim 18 , wherein in the second mode of operation:
the configurable impedance network of the first RF path provides a resistive coupling between the first node and a reference ground, and
the configurable impedance network of the second RF path provides a capacitive coupling between the second node and the reference ground.
20. The RF circuital arrangement according to claim 1 , further comprising a third RF path comprising a configurable impedance network, wherein:
the antenna switch is further connected to a third node of the third RF path,
the antenna switch is further configured to selectively couple the third node to the antenna, and
the first mode of operation of the RF circuital arrangement further comprises:
the antenna switch provides a high impedance capacitive coupling between the third node and the antenna, so that an impedance of the third RF path seen at the third node is capacitively coupled to the first node; and
the configurable impedance network of the third RF path is configured to further affect the impedance seen at the third node so as to further affect the resonance frequency of the resonance affect at the first node due to the further capacitive coupling of the impedance seen at the third node to the first node.
21. The RF circuital arrangement according to claim 20 , wherein in the first mode of operation:
the configurable impedance network of the second RF path provides a resistive coupling between the second node and the reference ground, and
the configurable impedance network of the third RF path provides a resistive coupling between the third node and the reference ground.