Switchable routing circuit and method for routing a signal

Abstract

The invention relates to a switchable routing circuit (2) comprising: - a plurality of ports including a common input (P1) port and two selection ports (P2, P3); - at least one resistor (R); - a plurality of switching elements (SW0, SW2, SW3), wherein each of the ports (P1, P2, P3) is connected to a respective one of the plurality of switching elements (SW0, SW2, SW3); and - a coupling element (C1), which is coupled between the plurality of ports (P1, P2, P3); wherein the switchable signal routing circuit (2) is configured to couple the common input port (P1) to one or both of the selection ports (P2, P3) by: - varying the even and odd characteristic impedances of the coupling element (C1); and - switching the respective one of the switching elements (SW0, SW2, SW3) between a short-circuit-state and an open-circuit-state.

Description

[0001] Switchable routing circuit and method for routing a signal

[0002] Description

[0003] The invention relates to a switchable routing circuit and a method for routing a signal from a common input port to at least one selection port.

[0004] It would be desirable to have a distributing network that is designed to send the signal of one input port to N output ports simultaneously, with the following additional requirements (or constraints):

[0005] 1. The distributing network should be broadband, ideally from arbitrary nonzero frequency to arbitrary finite high frequency.

[0006] 2. Each of the N output ports of the distributing network should be individually selectable as transmitting or not transmitting one.

[0007] 3. As minimum requirement, the input port and all the M (1<M<N) output ports of the distributing network selected to transmit should be impedance matched.

[0008] 4. As additional requirement, not only the M transmitting ports but also the remaining ones should be impedance matched, i.e. all the N+l ports of the distributing network should be impedance matched, independently on which port(s) is(are) transmitting.

[0009] 5. The insertion loss of the distributing network should be reduced (or even minimized).

[0010] 6. The temperature dependency of the distributing network should be reduced (or even minimized). 7. The linearity of the distributing network should be increased (or even maximized).

[0011] 8. The sensitivity of the distributing network to manufacturing process variations and the requirement of postproduction alignment should be reduced (or even minimized).

[0012] One possible structure that holds some - but not all - of the requirements listed above is the single pole N throw (SPNT) switch, wherein within this context, N is an integer multiple and stands for "multiple". A detailed description of the SPNT switch can be found in Roberto Sorrentino, Giovanni Bianchi: Microwave and RF Engineering, Ch. 10, pp. 363-389. The main drawback of the SPNT switch is that only one output port at the time can be selected among the available N output ports.

[0013] Thus, at least requirement 2 stating that each of the N output ports should be individually selectable as transmitting or not transmitting one is not satisfied.

[0014] In addition, according to US 9,712,133 B2 there is an inherently poor isolation among the selection ports, therefore the power transfer ratio between the common input port and one selection port depends on the load applied to the other selection ports.

[0015] Furthermore, if more than on selection port is selected, some power is lost inside the component, for example: If two selection ports are selected, half of the power is lost.

[0016] It is therefore an object of the invention to provide a switchable routing circuit which reduces or even eliminates the above-mentioned power loss.

[0017] The problem is solved by a switchable routing circuit according to claim 1. Further, the problem is solved by a method for routing a signal according to claim 11.

[0018] In detail, the switchable routing circuit comprises a plurality of ports including a common input port and two selection ports as well as at least one resistor. Moreover, the circuit comprises a plurality of switching elements, wherein each of the ports is connected to a respective one of the plurality of switching elements; and a coupling element, which is coupled between the plurality of ports.

[0019] The switchable signal routing circuit is configured to couple the common input port to one or both of the selection ports by varying the even and odd characteristic impedances of the coupling element and switching the respective one of the switching elements between a short-circuit-state and an open-circuit-state.

[0020] With this configuration, it is possible to route the signal from the common input port to one of the selection ports or to both of the selection ports without an increased power loss. This is possible by controlling the switching elements in order to present either low impedance (ideally 0 Q, or short circuit) or high impedance (ideally co Q, or open circuit).

[0021] In an embodiment, a transmission line is interposed between the coupling element and one of the selection ports.

[0022] According to an alternative embodiment, a transmission line is interposed between the coupling element and each one of the selection ports. In other words, there are two transmission lines, one between the coupling element and the first selection port and one between the coupling element and the second selection port.

[0023] In a further embodiment, a (further) transmission line is interposed between the coupling element and the common input port.

[0024] The electrical length of all the transmission lines remains close to 90° at the centre frequency. The embodiments with the transmission lines are also advantageous in terms of improvement against power dissipation. The transmission lines could be partially or totally replaced by passive 2-port networks, containing combination of lumped, semi-lumped and distributed elements.

[0025] According to a further embodiment, the coupling element comprises a directional coupler, which is of one of the following coupler types: microstrip, stripline or multilayer stripline. In addition, the couple can also be realized by coupled rods, coupled bars or by interdigital structures in any of the above-mentioned possibilities. In an embodiment, the coupling element is a Lange Coupler, wherein the main arrangement is "twisted". Alternatively, the coupling element comprises a nontwisted directional coupler having the same characteristic impedances and electrical length. Especially Lange Coupler have many advantages regarding such circuits.

[0026] According to a further embodiment, the at least one resistor comprises an impedance of 50Q. This value corresponds with the working or normalization impedance and is therefore advantageous.

[0027] In this context, according to an embodiment, an impedance of the transmission line(s) is adjusted around the impedance of the at least one resistor.

[0028] Moreover, a switchable routing device comprising a plurality of switchable routing circuits is disclosed herewith. The plurality of switchable routing circuits can be the above-mentioned circuits. Preferably, the plurality of routing circuits are cascaded.

[0029] The method for routing a signal, preferably by using the above-mentioned switchable routing circuit comprises the steps of: transmitting a signal to a common input port; routing the signal to a coupling element; selecting one or both selecting ports by varying the even and odd characteristic impedances of the coupling element and by switching the respective one of the switching elements between a short- circuit-state and an open-circuit-state; and transmitting the signal to the one or both selected ports.

[0030] The advantages and preferred embodiments listed with regard to the circuit are to be applied mutatis mutandis to the device and / or to the method and vice versa.

[0031] The above and further features and advantages of the invention will become more readily apparent from the following detailed description of preferred embodiments of the invention with reference to the accompanying drawings, in which like reference signs designate like features, and in which: Fig. 1 shows a switchable routing circuit according to a first embodiment of the invention;

[0032] Fig. 2 shows the switchable routing circuit according to a second embodiment of the invention;

[0033] Fig. 3 shows the switchable routing circuit according to a third embodiment of the invention; and

[0034] Fig. 4 shows the switchable routing circuit according to a fourth embodiment of the invention.

[0035] Fig. 1 shows a switchable routing circuit 2 (shortly "circuit" in the following) according to a first embodiment of the invention. The circuit 2 comprises a plurality of ports, namely a common input port Pl and two selection ports P2, P3. The ports Pl, P2, P3 are connected to each other via a coupling element Cl. The coupling element Cl enables the circuit to route a signal from the common input port Pl to one of or both selection ports P2, P3.

[0036] Furthermore, the circuit 2 comprises a resistor R that is in the shown embodiment referring to the common input port Pl.

[0037] Moreover, the circuit 2 also comprises a plurality of switching elements SWO, SW2, SW3, wherein one of the switching elements SWO, SW2, SW3 is assigned to one port Pl, P2, P3. In detail, the first switching element SWO belongs to the common input port Pl, the second switching element SW2 belongs to the first selection port P2 and the third switching element SW3 belongs to the second selection port P3. The switching elements SWO, SW2, SW3 could be any electronically controllable switch: field effect transistors (drain-source, control on the gate), bipolar transistors (emitter-collector, control on the base), semiconductor diodes like PIN, Schoktty, conventional junction diodes, (anode-cathode, control by means of anode-cathode DC current through a bias network), electromechanical o micro-electro-mechanical (MEMS) device with electromagnetic, electrostatic, or piezo-electric control. The switching elements SWO, SW2, SW3 can be controlled in order to present either low impedance (ideally 0 Q, or short circuit) or high impedance (ideally co Q, or open circuit).

[0038] The proposed circuit has 3 states, as per the following table

[0039] According to the invention, the coupling element Cl is a directional coupler, wherein the switchable signal routing circuit is configured to couple the common input port Pl to one or both of the selection ports by: varying the even and odd characteristic impedances of the coupling element; and switching the respective one of the switching elements between a short- circuit-state and an open-circuit-state.

[0040] The embodiment according to Fig. 2 differs in that the circuit 2 comprises a transmission line TL3, which is connected between the coupling element Cl and the second selection port P3. There are different constraints on the characteristic impedances of Cl (ZOE, ZOO, i.e. even and odd mode) and TL3 (Zo). There are different optimum values for the different operation states, working bandwidth, and the "privileged" port.

[0041] The inventive idea also bases on the following equations regarding the different states depending on which port is selected or should be selected: where Ro is the working or normalization impedance (typically 50 Q); ZOE / ZOO is a monotonic increasing function of the working bandwidth.

[0042] There are 5 equations 1, 2a, 2b, 3 plus the ratio Z OE / ZOO given by the required bandwidth with 2 unknowns ZOE, ZOO .

[0043] In a further embodiment as shown in Fig. 3, all signal lines comprises a transmission line. Hence, transmission line TL1 is connected between the common input port Pl and the coupling element Cl, transmission line TL2 is connected between the first selection port P2 and the coupling element Cl and transmission line TL3 is connected as already described above. The characteristic impedances Z01, Z02, Z03 can be adjusted around Ro, in order to improve the transmission coefficients in some operation modes and / or in a portion of the working bandwidth.

[0044] A different embodiment is shown in Fig. 4. The main difference is the realization of the coupling element Cl. In Fig. 4 the coupling element Cl is a non-twisted directional coupler, while in the other shown embodiments the coupling element Cl is a "twisted" directional coupler, like a Lange Coupler. List of reference numerals

[0045] 2 switchable routing circuit

[0046] Pl common input port

[0047] P2 first selection port

[0048] P3 second selection port

[0049] Cl coupling element

[0050] SWO first switching element

[0051] SW2 second switching element

[0052] SW3 third switching element

[0053] TL1 first transmission line

[0054] TL2 second transmission line

[0055] TL3 third transmission line

Claims

Claims1. Switchable routing circuit (2) comprising: a plurality of ports including a common input (Pl) port and two selection ports (P2, P3); at least one resistor (R); a plurality of switching elements (SWO, SW2, SW3), wherein each of the ports (Pl, P2, P3) is connected to a respective one of the plurality of switching elements (SWO, SW2, SW3); and a coupling element (Cl), which is coupled between the plurality of ports (Pl, P2, P3); wherein the switchable signal routing circuit (2) is configured to couple the common input port (Pl) to one or both of the selection ports (P2, P3) by: varying the even and odd characteristic impedances of the coupling element (Cl); and switching the respective one of the switching elements (SWO, SW2, SW3) between a short-circuit-state and an open-circuit-state.

2. Switchable routing circuit (2) according to claim 1, wherein a transmission line (TL2, TL3) is interposed between the coupling element (Cl) and one of the selection ports (P2, P3).

3. Switchable routing circuit according (2) to claim 1, wherein a transmission line (TL2, TL3) is interposed between the coupling element (Cl) and each one of the selection ports (P2, P3).

4. Switchable routing circuit (2) according to one of claims 1 to 3, wherein a transmission line (TL1) is interposed between the coupling element (Cl) and the common input port (Pl).

5. Switchable routing circuit (2) according to one of claims 1 to 4, wherein the coupling element (Cl) comprises a directional coupler, which is of one of the following coupler types: microstrip, stripline or multilayer stripline.

6. Switchable routing circuit (2) according to claim 5, wherein the coupling element (Cl) is a Lange Coupler.

7. Switchable routing circuit (2) according to one of claims 1 to 4, wherein the coupling element (Cl) comprises a non-twisted directional coupler.

8. Switchable routing circuit (2) according to one of claims 1 to 7, wherein the at least one resistor (R) comprises an impedance of 50Q.

9. Switchable routing circuit (2) according to claims 2 to 4, wherein an impedance of the transmission line (TL1, TL2, TL3) is adjusted around the impedance of the at least one resistor (R).

10. Switchable routing device comprising a plurality of switchable routing circuits (2) according to one of claims 1 to 9.

11. Method for routing a signal, preferably by using a switchable routing circuit (2) according to one of claims 1 to 10, the method comprising the steps of: transmitting a signal to a common input port (Pl); routing the signal to a coupling element (Cl); selecting one or both selecting ports (P2, P3) by varying the even and odd characteristic impedances of the coupling element (Cl) and by switching the respective one of the switching elements (SWO, SW2, SW3) between a short-circuit-state and an open-circuit-state; and transmitting the signal to the one or both selected ports (P2, P3).

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