Radio frequency switch circuit and apparatus having built-in coupler

A radio frequency switch circuit is described including a radio frequency switch and a coupler. The radio frequency switch includes a first band switch circuit connected between a first signal port and a common port, and configured to switch a first band signal. The coupler includes a first coupling wiring, disposed adjacent to a signal wiring formed between the common port of the radio frequency switch and an antenna port, and configured to form a first coupling signal with the signal wiring. A resonant frequency of the first coupling wiring is based on an inductance of the first coupling wiring and a capacitance of the radio frequency switch.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit under USC 119(a) of Korean Patent Application Nos. 10-2016-0086254, filed on Jul. 7, 2016 and 10-2016-0154330, filed on Nov. 18, 2016 in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference for all purposes.

BACKGROUND

The following description relates to a radio frequency switch circuit and apparatus having a built-in coupler for use in a time division multiplexing (TDM) communications system.

2. Description of Related Art

In general, in various communications systems using a time division multiplexing (TDM) scheme, an antenna radio frequency (RF) switch is used between a transmitter and a receiver. In addition, in a communications system performing multiple communications, a band selection radio frequency (RF) switch is used between an antenna and a duplexer in order to switch between band signals.

The antenna RF switch described above alternately switches the transmitter and the receiver on and off, thus, decreasing the entire power consumption of a system and decreasing interference between the transmitter and the receiver. In addition, the band selection RF switch selectively switches multiple bands on and off, thus, decreasing the entire power consumption of a system and decreasing interference between the bands.

The RF switch described above may be used in communications systems such as Bluetooth, cellular personal communications service (PCS), code division multiple access (CDMA), wideband CDMA (WCDMA), time division multiple access (TDMA), global system for mobile communications (GSM), and wireless local area network (WLAN).

The RF switch requires performance characteristics such as low insertion loss, high power handling capability, high isolation, and the like.

In addition, an existing communications system includes a coupler to monitor an output signal of a power amplifier (PA).

The coupler, however, has some operational disadvantages such as mismatching between antenna impedances and signal loss. The coupler may be used, however, to control an output signal and control an input signal to improve efficiency of an entire system, and thus allow for an increase in a battery discharge time and system adjustment.

However, existing communications systems may include a coupler implemented or positioned separately from the RF switch, the RF switch may be implemented as an integrated circuit (IC), and the coupler may be formed as a printed circuit board (PCB) pattern on a PCB or may be mounted as an individual component on a board or the PCB.

A coupler has a coupling factor, which can represent how much power is provided to a coupled port of the coupler relative to the power of an RF signal at the power input port. Such coupler typically causes an insertion loss in an RF signal path. Thus, an RF signal received at a power input port of the coupler can have a lower power when provided at the power output port of the coupler. Insertion loss can be due to a portion of the RF signal being provided to the coupled port (or to the isolated port) and/or to losses associated with the main transmission line of the coupler. Thus, as described above, in a configuration in which a PCB-based coupler is implemented external to the RF switch, separately from an IC type RF switch, an area occupied by the PCB-based coupler is large, and efficiency is decreased due to the large loss of the coupler.

In addition, in a case in which the communications system includes a bi-directional coupler to transmit/receive (Tx/Rx) coupling separately from the RF switch, the bi-directional coupler may detect bi-directional signals (forward and reverse signals). However, the bi-directional coupler occupies a large area in a communications module depending on a frequency being used. Also, efficiency of the power amplifier (PA) is further decreased due to line loss caused by implementation of the PCB.

SUMMARY

In one general aspect, there is provided a radio frequency switch apparatus having a built-in coupler that has a decreased occupied area and a size, and has an improved coupling characteristics using capacitances of switch devices in a switch-off state among switch devices included in a radio frequency switch circuit. The radio frequency switch apparatus includes an integrated circuit (IC) including a radio frequency switch and the coupler.

In accordance with an embodiment, there is provided a radio frequency switch circuit, including: a radio frequency switch may include a first band switch circuit connected between a first signal port and a common port, and configured to switch a first band signal; and a coupler may include a first coupling wiring, disposed adjacent to a signal wiring formed between the common port of the radio frequency switch and an antenna port, and configured to form a first coupling signal with the signal wiring, wherein a resonant frequency of the first coupling wiring may be based on an inductance of the first coupling wiring and a capacitance of the radio frequency switch.

The first band switch circuit may include a first series switch circuit connected between the first signal port and the common port, and a first shunt switch circuit connected between the first signal port and a ground, and the resonant frequency of the first coupling wiring may be based on the inductance of the first coupling wiring and a capacitance of the first shunt switch circuit in a switch-off state.

The coupler further may include a second coupling wiring spaced apart from the first coupling wiring and adjacent to the signal wiring and the antenna port to form a second coupling signal with the signal wiring, and a resonant frequency of the second coupling wiring may be based on an inductance of the second coupling wiring and a capacitance of the first band switch circuit.

The first band switch circuit may include a first series switch circuit connected between the first signal port and the common port, and a first shunt switch circuit connected between the first signal port and a ground, and the resonant frequency of the second coupling wiring may be based on the inductance of the second coupling wiring and a capacitance of the first shunt switch circuit in a switch-off state.

The resonant frequency of the first coupling wiring may coincide with a frequency of the first band signal transmitted from the first band switch circuit based on the inductance of the first coupling wiring and a capacitance of the first shunt switch circuit in a switch-off state.

The resonant frequency of the first coupling wiring may be based on a capacitance of the first shunt switch circuit in a switch-off state, and a mutual capacitance and a mutual inductance between the signal wiring and the first coupling wiring.

A resonant frequency of the coupler may be based on

Fres=12⁢⁢π*Coff⁢(CmLm-1Zo),
where Coff may be a capacitance of the first shunt switch circuit in a switch-off state, Cm may be a mutual capacitance between the signal wiring and the first coupling wiring, Lm may be a mutual inductance between the signal wiring and the first coupling wiring, and Zo may be an intrinsic impedance of the first signal port.

The radio frequency switch and the coupler may be integrally formed on an integrated circuit board.

In accordance with an embodiment, there is provided a radio frequency switch apparatus, including: a radio frequency switch may include a first band switch circuit connected between a first signal port and a common port, and configured to switch a first band signal; a coupler may include a first coupling wiring disposed adjacent to a signal wiring formed between the interstage matching circuit and an antenna port to form a first coupling signal with the signal wiring; and an interstage matching circuit connected to the common port and configured to perform impedance matching between the radio frequency switch and the coupler, wherein a resonant frequency of the first coupling wiring may be based on an inductance of the first coupling wiring and a capacitance of the radio frequency switch.

The first band switch circuit may include a first series switch circuit connected between the first signal port and the common port and a first shunt switch circuit connected between the first signal port and a ground, and the resonant frequency of the first coupling wiring may be based on the inductance of the first coupling wiring and a capacitance of the first shunt switch circuit in a switch-off state.

The coupler further may include a second coupling wiring spaced apart from the first coupling wiring, and adjacent to the signal wiring and the antenna port to form a second coupling signal with the signal wiring, and a resonant frequency of the second coupling wiring may be based on an inductance of the second coupling wiring and a capacitance of the first band switch circuit.

The first band switch circuit may include a first series switch circuit connected between the first signal port and the common port and a first shunt switch circuit connected between the first signal port and a ground, and the resonant frequency of the second coupling wiring may be based on the inductance of the second coupling wiring and a capacitance of the first shunt switch circuit in a switch-off state.

The resonant frequency of the first coupling wiring coincides with a frequency of the first band signal transmitted from the first band switch circuit based on the inductance of the first coupling wiring and a capacitance of the first shunt switch circuit in a switch-off state.

The resonant frequency of the first coupling wiring may be based on a capacitance of the first shunt switch circuit in a switch-off state, and a mutual capacitance and a mutual inductance between the signal wiring and the first coupling wiring.

A resonant frequency of the coupler may be based on

Fres=12⁢⁢π*Coff⁢(CmLm-1Zo),
where Coff may be a capacitance of the first shunt switch circuit in the switch-off state, Cm may be the mutual capacitance between the signal wiring and the first coupling wiring, Lm may be the mutual inductance between the signal wiring and the first coupling wiring, and Zo may be an intrinsic impedance of the first signal port.

The radio frequency switch and the coupler may be integrally formed on an integrated circuit board.

In accordance with an embodiment, there is provided an apparatus, including: a first band switch circuit may include a first series switch circuit and a first shunt switch circuit, wherein the first series switch circuit may be connected between a signal port and a common port; and a coupler may include a signal wiring may include one end connected to the common port and another end connected to an antenna port, and a first coupling wiring disposed coextensive to the signal wiring to form a coupling with the signal wiring and configured to produce a first coupling signal, wherein a resonant frequency of the first coupling wiring may be based on an inductance of the first coupling wiring and a capacitance of the first shunt switch circuit in a switch-off state.

The first coupling wiring may be disposed between a first detection port and a resistor.

In response to the first shunt switch circuit being in the switch-off state and the first series switch circuit being in a switch-on state, the first band switch circuit transmits a first band signal to the coupler.

The apparatus may further include a second coupling wiring disposed coextensive to the signal wiring, diametrically opposite to the first coupling wiring, and configured to form a coupling with the signal wiring and produce a second coupling signal to monitor signal reception strength.

The apparatus may further include an output matching circuit disposed between the coupler and an antenna terminal configured to match an impedance of the first band switch circuit and match an impedance of the antenna terminal and an impedance of the coupler to each other to decrease transfer loss of signals.

The impedance of the coupler may be different from the impedance of the first band switch circuit.

The apparatus may further include a radio frequency switch may include the first band switch circuit and connected between the signal port and the common port; and an interstage matching circuit disposed between the radio frequency switch and the coupler configured to match impedances between the radio frequency switch and the coupler.

The signal wiring may be disposed on a first layer of an integrated circuit, the first and second coupling wirings may be disposed on a second layer of the integrated circuit, and corresponding resistors of the first and second coupling wirings, corresponding grounds of the first and second coupling wirings, and a ground part of the integrated circuit may be disposed on a third layer of the integrated circuit.

The second layer may be disposed below the first layer, and the third layer may be disposed below the second layer.

The first and second coupling wirings may be disposed on a layer of an integrated circuit different from a layer on which a ground part of the integrated circuit may be disposed to relatively increase a distance between the first and second coupling wirings and the ground part of the integrated circuit.

In accordance with another embodiment, there is provided an apparatus, including: a first band switch circuit may include a first series switch circuit and a first shunt switch circuit, wherein the first series switch circuit may be connected between a signal port and a common port; and a coupler may include a signal wiring may include one end connected to the common port and another end connected to an antenna port, and a first coupling wiring disposed coextensive to the signal wiring to form a coupling with the signal wiring and configured to produce a first coupling signal, wherein a resonant frequency of the first coupling wiring may be determined based on a capacitance of the first shunt switch circuit in a switch-off state, and a mutual capacitance and a mutual inductance between the signal wiring and the first coupling wiring.

The first coupling wiring and the signal wiring may be coupled to each other to form the mutual capacitance and the mutual inductance between the first coupling wiring and the signal wiring.

The first shunt switch circuit may be connected between the signal port and a ground, and the first shunt switch circuit changes from a switch-on state to the switch-off state based on a second gate signal of the first shunt switch circuit.

In response to the first shunt switch circuit being in the switch-off state and the first series switch circuit being in a switch-on state, the first band switch circuit transmits a first band signal to the coupler.

The resonant frequency, Fres, may be based on a following relationship

Fres=12⁢⁢π*Coff⁢(CmLm-1Zo),
where, Coff may be the capacitance of the first shunt switch circuit in the switch-off state, Cm may be the mutual capacitance between the signal wiring and the first coupling wiring, Lm may be the mutual inductance between the signal wiring and the first coupling wiring, and Zo may be an intrinsic impedance of the signal port.

DETAILED DESCRIPTION

FIG. 1is a schematic view illustrating a radio frequency switch circuit having a built-in coupler, according to an embodiment.

Referring toFIG. 1, the radio frequency switch circuit100having a built-in coupler, according to an embodiment, includes a radio frequency switch110and a coupler120.

The radio frequency switch110includes at least one first band switch circuit SWB1, connected between at least one first signal port P1and a common port Pcom. The first band switch circuit SWB1includes a capacitor Coff. The radio frequency switch110is configured to switch a first band signal SB1received at the first signal port P1.

In some embodiments, the radio frequency switch110includes one first band switch circuit SWB1. Alternatively, the radio frequency switch110may include first to N-th band switch circuits SWB1to SWBN (here, N indicates a natural number of 2 or more).

In this alternative embodiment, the first band switch circuit SWB1may be connected between the first signal port P1and the common port Pcom, and may switch the first band signal SB1, while the N-th band switch circuit SWBN may be connected between an N-th signal port PN and the common port Pcom, and may switch an N-th band signal SBN.

Because the radio frequency switch110is similarly applied to the various embodiments described, an overlapping description for the radio frequency switch110will be omitted to avoid redundancy.

The coupler120includes a first coupling wiring LCPL1between a first detection port PCPL1and an end point of a resistor R11, which is grounded GND1at another end thereof. The first coupling wiring LCPL1is disposed adjacent to, coextensive to, parallel to, substantially proximate to, or near to a signal wiring Lant to form a first coupling signal with the signal wiring Lant. The signal wiring Lant is positioned within the coupler120, between one end P11and another end P12, as shown inFIG. 1. The coupler120is formed, positioned, or disposed between the common port Pcom of the radio frequency switch110and an antenna port Pant to form a coupling with the signal wiring Lant and output a first coupling signal from the first detection port PCPL1.

In this case, a resonant frequency Fres from the first coupling wiring LCPL1is determined by an inductance of the first coupling wiring LCPL1and a capacitance Coff of the radio frequency switch110.

In an example, the one end P11of the signal wiring Lant is connected to the common port Pcom of the radio frequency switch110, and the other end P12of the signal wiring Lant is connected to the antenna port Pant.

FIG. 2is a schematic view illustrating a radio frequency switch apparatus having the built-in coupler, according to an embodiment.

Referring toFIG. 2, the radio frequency switch apparatus having a built-in coupler includes a radio frequency switch circuit100and an output matching circuit250.

The coupler120of the radio frequency switch circuit100includes a second coupling wiring LCPL2, in addition to a structure illustrated inFIG. 1.

The second coupling wiring LCPL2is disposed between a first detection port PCPL2and an end point of a resistor R21, which is grounded GND2at another end thereof. The second coupling wiring LCPL2is disposed adjacent to, coextensive to, parallel to, substantially proximate to, or near to the signal wiring Lant described with reference toFIG. 1to form a second coupling signal with the signal wiring Lant.

In an example, a resonant frequency Fres from the second coupling wiring LCPL2is determined by an inductance of the second coupling wiring LCPL2and the capacitance Coff of the first band switch circuit SWB1.

The output matching circuit250is connected between the antenna port Pant of the radio frequency switch circuit100and an antenna terminal Tout to which an antenna is connected, and may match impedances between the antenna port Pant and the antenna terminal Tout to decrease transfer loss of signals.

Referring toFIGS. 1 and 2, the radio frequency switch circuit100having a built-in coupler includes the radio frequency switch110and the coupler120and is formed on one or a single integrated circuit board using a same manufacturing process as to be implemented when forming a single integrated circuit.

As an example, the integrated circuit is an integrated circuit using a semiconductor board such as a silicon-on-insulator (SOI), or the like, and, for example, in an embodiment in which a semiconductor board is used such as the SOI, or the like, loss may be decreased due to high resistive board characteristics. The radio frequency switch110and the coupler120may be disposed as adjacent to, coextensive to, parallel to, substantially proximate to, or near to each other as possible to significantly decrease insertion loss.

Therefore, when the radio frequency switch circuit100having a built-in coupler, according to the embodiment, is used, the insertion loss is reduced, and an area occupied by the coupler and a size of the coupler is decreased.

As previously explained, the first coupling wiring LCPL1of the coupler120are connected to the first detection port PCPL1and the first resistor R11.

The first detection port PCPL1is connected to one end of the first coupling wiring LCPL1disposed adjacent to, coextensive to, parallel to, substantially proximate to, or near to the common port Pcom, and output a first coupling signal coupled from the signal wiring Lant. In an example, the first coupling signal provided through the first coupling wiring LCPL1may be used as a signal for monitoring transmission power.

The first resistor R11is connected between the other end of the first coupling wiring LCPL1disposed adjacent to, coextensive to, parallel to, substantially proximate to, or near to the antenna port Pant and the ground GND1, and matches impedances to each other. In an example, the first resistor R11, which is a resistor for matching impedances to each other, is set to 50Ω.

In addition, the second coupling wiring LCPL2of the coupler120is connected between the second detection port PCPL2and the second resistor R21.

The second detection port PCPL2is connected to one end of the second coupling wiring LCPL2disposed adjacent to, coextensive to, parallel to, substantially proximate to, or near to the antenna port Pant, and outputs a second coupling signal coupled from the signal wiring Lant. In an example, the second coupling signal provided through the second coupling wiring LCPL2is used as a signal to monitor reception strength. The second coupling wiring LCPL2is diametrically opposite to the first coupling wiring LCPL1or on another side of the signal wiring Lant on which the first coupling wiring LCPL1is disposed.

The second resistor R21is connected between the other end of the second coupling wiring LCPL2disposed adjacent to, coextensive to, parallel to, substantially proximate to, or near to the common port Pcom and a ground, and match impedances to each other. In an example, the second resistor R21, which is a resistor for matching impedances to each other, may be set to 50Ω as an example.

As described above, an area occupied by the coupler and a size of the coupler is decreased and loss of the coupler itself is improved. In an example in which the coupler120is implemented together with the radio frequency switch110by the integrated circuit IC, as compared to an example in which the coupler120is formed as a printed circuit board (PCB) pattern on a board, or is mounted as an individual coupler device as a board.

As illustrated inFIGS. 1 and 2, in an integrated circuit including the radio frequency switch110and the coupler120, an impedance of the coupler120connected to the antenna terminal, of which an impedance is 50Ω, and an impedance of the radio frequency switch110may not coincide with each other. As an example, the impedance of the radio frequency switch110is not 50Ω, and because the coupler120is connected to the antenna terminal, the impedance of the coupler120is 50Ω, which is the same as that of the antenna terminal.

In this example, an output matching circuit250is disposed between the coupler120and the antenna terminal Tout in order to match the impedance of the radio frequency switch110and the impedance of the antenna terminal and the coupler120to each other. Although the output matching circuit250is illustrated inFIG. 2as being external to the radio frequency switch apparatus100, in an alternative embodiment, the output matching circuit250may be integrated within the radio frequency switch apparatus100.

Therefore, the output matching circuit250matches the impedance between the radio frequency switch circuit100and the antenna terminal Tout. As a result, the impedance is matched between the radio frequency switch110and the coupler120, and the impedance is matched between the coupler120and the antenna terminal.

FIG. 3is another schematic view illustrating a radio frequency switch apparatus having a built-in coupler, according to an embodiment.

Referring toFIG. 3, the radio frequency switch apparatus having a built-in coupler, according to an embodiment, includes a radio frequency switch circuit100and an interstage matching circuit220. Although the interstage matching circuit220is illustrated inFIG. 3as being external to the radio frequency switch apparatus100, in an alternative embodiment, the interstage matching circuit220may be integrated within the radio frequency switch apparatus100.

The radio frequency switch circuit100is the same as the radio frequency switch circuit described with reference toFIGS. 1 and 2, and thus, a detailed description therefor will be omitted.

The coupler120includes a first coupling wiring LCPL1. The first coupling wiring LCPL1is disposed adjacent to, coextensive to, parallel to, substantially proximate to, or near to a signal wiring Lant formed between the interstage matching circuit220and an antenna port Pant to form a first coupling signal with a portion of the signal wiring Lant. In an example, one end P21of the signal wiring Lant is connected to the interstage matching circuit220, and the other end P22of the signal wiring Lant is connected to the antenna port Pant.

The interstage matching circuit220is connected between the common port Pcom of the radio frequency switch110and the coupler120. The interstage matching circuit220is configured to match impedances between the radio frequency switch110and the coupler120.

In addition, a resonant frequency Fres from the first coupling wiring LCPL1is determined by an inductance of the first coupling wiring LCPL1and a capacitance Coff of the radio frequency switch110.

FIG. 4is another schematic view illustrating a radio frequency switch apparatus having the built-in coupler, according to an embodiment.

Referring toFIG. 4, the radio frequency switch apparatus having a built-in coupler according to the exemplary embodiment includes a radio frequency switch circuit100and an interstage matching circuit220.

The coupler120of the radio frequency switch circuit100also includes a second coupling wiring LCPL2, in addition to a structure illustrated inFIG. 3.

The second coupling wiring LCPL2may be disposed adjacent to the signal wiring Lant, described with reference toFIG. 3, to form second coupling signal with the signal wiring Lant.

In an example, a resonant frequency Fres by the second coupling wiring LCPL2is determined by an inductance of the second coupling wiring LCPL2and a capacitance Coff of the first band switch circuit SWB1.

The interstage matching circuit220is connected between the common port Pcom of the radio frequency switch110and the coupler120. The interstage matching circuit220is configured to match impedances between the radio frequency switch110and the coupler120.

Furthermore, as illustrated inFIGS. 3 and 4, in an integrated circuit including the radio frequency switch110and the coupler120, an impedance of the coupler120connected to the antenna terminal, of which an impedance is 50Ω, does not coincide with or is different from the impedance of the radio frequency switch110. As an example, the impedance of the radio frequency switch110is not 50Ω, and because the coupler120is connected to an antenna, the impedance of the coupler120is 50Ω, which is the same as the impedance of the antenna terminal.

In an example, the interstage matching circuit220is disposed between the radio frequency switch110and the coupler120in order to match impedances between the radio frequency switch110and the coupler120. In an example, the interstage matching circuit220is disposed outside the integrated circuit including the radio frequency switch110and the coupler120.

The interstage matching circuit220is connected between the radio frequency switch110and the coupler120. The interstage matching circuit220is configured to match impedances between the radio frequency switch110and the coupler120.

FIG. 5is a schematic view illustrating a first band switch circuit, according to an embodiment;FIG. 6is an equivalent circuit diagram of a switch-on state of the first band switch circuit ofFIG. 5;FIG. 7is a schematic view illustrating an N-th band switch circuit, according to an embodiment; andFIG. 8is an equivalent circuit diagram of a switch-on state of the N-th band switch circuit ofFIG. 7.

Referring toFIGS. 5 and 6, the first band switch circuit SWB1includes a first series switch circuit SW1-1and a first shunt switch circuit SW1-2.

The first series switch circuit SW1-1is connected between the first signal port P1and a common port Pcom, and changes from a switch-on state to a switch-off state, and vice-versa, depending on a first gate signal SG1-1. As an example, the first series switch circuit SW1-1includes one or more switch devices M1-1, such as a metal oxide semiconductor field effect transistor (MOSFET), N-channel MOSFET, or P-channel MOSFET, connected in series between the first signal port P1and the common port Pcom.

The first shunt switch circuit SW1-2is connected between the first signal port P1and a ground, and changes from a switch-on state to a switch-off state, and vice-versa, depending on a second gate signal SG1-2. As an example, the first shunt switch circuit SW1-2includes one or more switch devices M1-2, such as a MOSFET, N-channel MOSFET, or P-channel MOSFET, connected in series between the first signal port P1and the ground.

Further, the switch devices M1-1and M1-2may be metal oxide semiconductor (MOS) transistors, and types of MOS transistors are not particularly limited.

In this example, in order for the first band switch circuit SWB1to transfer the first band signal SB1, the first shunt switch circuit SW1-2changes to a switch-off state, based on a low voltage level of the second gate signal SG1-2in response to the first series switch circuit SW1-1being in a switch-on state, based on a high voltage level of the first gate signal SG1-1. In this case, the first shunt switch circuit SW1-2in the switch-off state has a capacitance Coff.

Further, a resonant frequency Fres by the first coupling wiring LCPL1is determined by an inductance of the first coupling wiring LCPL1and a capacitance Coff of the first shunt switch circuit SW1-2in the switch-off state.

In contrast, in order for the first band switch circuit SWB1to block the first band signal SB1, the first shunt switch circuit SW1-2changes to a switch-on state, depending on a high voltage level of the second gate signal SG1-2in response to the first series switch circuit SW1-1being in a switch-off state, and depending on a low voltage level of the first gate signal SG1-1.

Referring toFIGS. 7 and 8, the N-th band switch circuit SWBN includes an N-th series switch circuit SWN-1and an N-th shunt switch circuit SWN-2.

The N-th series switch circuit SWN-1is connected between the N-th signal port PN and a common port Pcom, and changes from a switch-on state to a switch-off state, and vice-versa, depending on a first gate signal SGN-1. As an example, the N-th series switch circuit SWN-1includes one or more switch devices MN-1, such as a MOSFET, N-channel MOSFET, or P-channel MOSFET, connected in series between the N-th signal port PN and the common port Pcom.

The N-th shunt switch circuit SWN-2is connected between the N-th signal port PN and a ground, and changes from a switch-on state to a switch-off state, and vice-versa, depending on a second gate signal SGN-2. As an example, the N-th shunt switch circuit SWN-2includes one or more switch devices MN-2, such as a MOSFET, N-channel MOSFET, or P-channel MOSFET, connected in series between the N-th signal port PN and the ground.

In an embodiment, the one or more switch devices MN-1and MN-2may be MOS transistors, and types of MOS transistors are not particularly limited.

In an embodiment, in order for the N-th band switch circuit SWBN to transfer the N-th band signal SBN, the N-th shunt switch circuit SWN-2changes to a switch-off state based on a low voltage level of the second gate signal SGN-2in response to the N-th series switch circuit SWN-1being in a switch-on state based on a high voltage level of the first gate signal SGN-1. In this embodiment, the N-th shunt switch circuit SWN-2in the switch-off state has a capacitance Coff.

In this embodiment, a resonant frequency Fres by the first coupling wiring LCPL1is based on or is determined by an inductance of the first coupling wiring LCPL1and a capacitance Coff of the N-th shunt switch circuit SWN-2in the switch-off state.

Further, in contrast, in order for the N-th band switch circuit SWBN to block the N-th band signal SBN, the N-th shunt switch circuit SWN-2changes to a switch-on state, based on a high voltage level of the second gate signal SGN-2in response to the N-th series switch circuit SWN-1being in a switch-off state, based on a low voltage level of the first gate signal SGN-1.

Referring toFIGS. 5 through 8, the number of semiconductor switch devices included in each of the first to N-th shunt switch circuits SW1-2to SWN-2may be determined by considering an entire capacitance Coff of switch devices in a switch-off state in the corresponding shunt switch circuits determining the resonant frequency Fres of the coupler120, because capacitances of the respective semiconductor switch devices in the switch-off state are summed up to have an influence on the resonant frequency Fres of the coupler120.

Referring toFIGS. 5 through 8, the resonant frequency Fres by the first coupling wiring LCPL1may coincide with a frequency of the first band signal SB1transferred through the first band switch circuit SWB1by the inductance of the first coupling wiring LCPL1and the capacitance Coff of the first shunt switch circuit SW1-2in the switch-off state.

In a respective embodiments, the coupler120may be formed on a single-layer semiconductor board or may be formed on a multilayer semiconductor board in order to be manufactured in a smaller size, an example of which will be described with reference toFIGS. 9A through 9C.

FIGS. 9A through 9Care schematic views illustrating the coupler ofFIG. 2.FIG. 9Ais a perspective view of the coupler120.FIG. 9Bis a view illustrating the first and second coupling wirings LCPL1and LCPL2ofFIG. 9A.FIG. 9Cis an enlarged view of the first coupling wiring LCPL1, the first resistor R11(seeFIG. 2), and a first ground GND1.

Referring toFIGS. 9A and 9B, the signal wiring Lant is disposed on a first layer, the first and second coupling wirings LCPL1and LCPL2are disposed on a second layer, and the first and second resistors, first and second grounds GND1and GND2, and a ground part GND of the insulating layer are disposed on a third layer.

The second layer is disposed below the first layer, and the third layer may be disposed below the second layer. Wirings between the first and second layers and signal wirings (or ground wirings) of the second and third layers are electrically connected to each other through conductive vias. In an example, the first and second resistors disposed on the third layer are electrically connected to corresponding coupling wirings and a ground by a conductor pattern CP.

In this embodiment, the first and second coupling wirings LCPL1and LCPL2are disposed on a layer different from a layer on which the ground part GND is disposed, such that a distance between the first and second coupling wirings LCPL1and LCPL2and the ground part GND in the integrated circuit is relatively increased. Therefore, isolation between the first and second coupling wirings LCPL1and LCPL2and the ground part GND is improved.

InFIGS. 9A through 9C, a coupler structure including the signal wiring Lant and the first and second coupling wirings LCPL1and LCPL2is only an example, and the various embodiments are not limited thereto.

Furthermore, the resonant frequency Fres of the first coupling wiring LCPL1is determined based on the capacitance Coff of the first shunt switch circuit SW1-2in the switch-off state, and a mutual capacitance Cm and a mutual inductance Lm between the signal wiring Lant and the first coupling wiring LCPL1. In an example, the inductance of the first coupling wiring LCPL1is the mutual inductance. This will be described with reference toFIG. 10.

FIG. 10is a view to describe the coupler ofFIG. 1.

FIG. 10is an equivalent circuit diagram of the coupler in the radio frequency switch circuit100in which the first band switch circuit SWB1is in a switch-on state. The first band switch circuit SWB1is the first band switch circuit of N-th band switch circuits of the radio frequency switch110.

Referring toFIGS. 1 and 10, the coupler120includes the first coupling wiring LCPL1, which is represented as an inductor. In this case, the signal wiring Lant, between the common port Pcom of the radio frequency switch110and the antenna port Pant, is an inductor.

In this embodiment, the first coupling wiring LCPL1and the signal wiring Lant are disposed adjacent to each other and coupled to each other, such that a mutual capacitance Cm and a mutual inductance Lm is formed between the first coupling wiring LCPL1and the signal wiring Lant.

The resonant frequency Fres of the coupler120is determined as represented by the following Equation 1:

Here, Coff is a capacitance of the first shunt switch circuit SW1-2in the switch-off state, Cm is the mutual capacitance between the signal wiring Lant and the first coupling wiring LCPL1, Lm is the mutual inductance between the signal wiring Lant and the first coupling wiring LCPL1, and Zo is an intrinsic impedance (a line intrinsic impedance) of the first signal port P1.

Referring to Equation 1, in the radio frequency switch apparatus having a built-in coupler, a switch in a switch-off state in the radio frequency switch circuit is represented by a capacitance Coff. In addition, in Equation 1, a coupling factor and an isolation value of the coupler are set using the mutual capacitance Cm and the mutual inductance Lm, and the capacitance Coff has an influence on a resonant point of the coupling factor and the isolation of the coupler. In consideration of this, the mutual capacitance Cm and the mutual inductance Lm are determined.

As an example, in an example in which the resonant frequency of the coupler is set to coincide with a use frequency, excellent coupling characteristics may be secured.

In addition, referring toFIG. 10, a level at which an original signal interferes and is viewed in the coupler120, when a signal input through the first signal port P1is transmitted through an antenna connected to the antenna port, is called a ‘coupling factor’. A level at which a signal is viewed in the coupler120when the signal is received in a reverse direction (from the antenna port to the first signal port P1) is called ‘isolation.’ In this case, because the isolation is an undesired signal, the lower the isolation, the better.

In addition, a phase difference depending on a direction of the coupler may be present in coupling by the mutual inductance Lm, different than in the case of coupling by the mutual capacitance Cm. The coupling factor and the isolation as described above may be represented by the following Equations 2 and 3:

Here, Vcpl is a coupling voltage, Vinput is an input voltage input through the first signal port P1, Voutput is an output voltage output through the antenna port, and w is an angular frequency (=2πf (here, f is a frequency)).

It may be appreciated from Equations 2 and 3 that the coupling factor and the isolation may be determined based on the mutual capacitance Cm and the mutual inductance Lm.

FIG. 11Ais a graph illustrating non-ideal performance of a coupler formed on a printed circuit board.FIG. 11Bis a graph illustrating an ideal performance of an integrated circuit (IC) built-in coupler in accord with an embodiment.

InFIG. 11A, G11is a graph illustrating insertion loss characteristics, G12is a graph illustrating directivity characteristics, G13is a graph illustrating the characteristics of a coupling factor, and G14is a graph illustrating the characteristics of isolation.

In addition, inFIG. 11B, G21is a graph illustrating insertion loss characteristics, G22is a graph illustrating directivity characteristics, G23is a graph illustrating the characteristics of a coupling factor, and G24is a graph illustrating the characteristics of isolation.

It may be appreciated fromFIGS. 11A and 11Bthat performance of an ideal IC-based coupler, according to an embodiment, is improved when compared to performance of a non-ideal PCB-based coupler. For example, insertion loss was increased from −0.24 [dB] to −0.17 [dB] by 0.07 [dB].

In addition, a space of about 90% may be saved in the IC-based coupler, according to an embodiment, compared to the non-ideal PCB-based coupler.

The radio frequency switch circuit and apparatus having a built-in coupler, according to an embodiment as described above, may be used for a frequency division multiplexing (FDM) communications scheme, but may also be appropriate for a time division multiplexing (TDM) communications scheme.

The TDM communications scheme is a scheme to detect signals through a signal wiring, which is a common communications wiring, without using signal wirings for each band paths. This communications scheme has at least an advantage in terms of corresponding size and cost, and specific band signals are transmitted and received at any one point in time in the TDM communications scheme such that the signals are more accurately detected through the signal wiring, which is a common communications wiring in the TDM communications scheme, in contrast with the FDM communications scheme.

As set forth above, according to an embodiment, a coupler is built in a radio frequency switch to implement an integrated circuit (IC), where an area occupied by the coupler and the size of the coupler is decreased, and signal loss is decreased when compared to a coupler formed of a PCB-based pattern.

Because one coupler is disposed between the common port of the radio frequency switch and the antenna port, the radio frequency switch circuit having a built-in coupler according to an embodiment, can include one coupler compared to other circuits, in which couplers are disposed in each of a number of band paths. Some of the many advantages of the radio frequency switch circuit having a built-in coupler, according to the embodiment, is smaller in the area to be occupied by the coupler and a manufacturing cost of the coupler is reduced, and signals may be detected through the coupler immediately before transmitting the signals through the antenna, and thus, the signals are more accurately detected.

In addition, capacitances of switch devices in a switch-off state, among switch devices included in the radio frequency switch, are used to allow a resonant frequency to coincide with a corresponding band frequency, such that loss of the coupler is decreased, thus, improving performance characteristics of the coupler.

Further, signal and power loss of the coupler is decreased, thus, relatively decreasing power consumption.

While various embodiments have been shown and described above, it will be apparent after an understanding of the disclosure of this application that modifications and variations could be made without departing from the scope of the present application, as defined by the appended claims.