阅读说明：本技术 Rf切换 (RF handover ) 是由 阳昕 多米尼克斯·马蒂纳斯·威廉默斯·莱纳特 于 2019-08-07 设计创作，主要内容包括：RF收发器前端包括接收器分支和发射器分支,所述接收器分支包括一段传输线、阻抗匹配网络、下游分路开关和下游的另外的接收器部件。所述阻抗匹配网络被配置成当所述分路开关断开并且所述RF收发器前端可操作于接收器模式时,变换所述另外的接收器部件的输入阻抗以与所述接收器分支的输入阻抗相匹配。所述阻抗匹配网络另外被配置成当所述分路开关闭合并且所述RF收发器前端可操作于发射器模式时,变换所述分路开关的输入阻抗以将开路呈现为所述接收器分支的所述输入阻抗。在所述RF收发器的操作频率下,所述传输线的长度可以为零到小于λ/4。(The RF transceiver front-end comprises a receiver branch comprising a length of transmission line, an impedance matching network, a downstream shunt switch and downstream further receiver components, and a transmitter branch. The impedance matching network is configured to transform the input impedance of the further receiver component to match the input impedance of the receiver branch when the shunt switch is open and the RF transceiver front end is operable in a receiver mode. The impedance matching network is further configured to transform an input impedance of the shunt switch to present an open circuit as the input impedance of the receiver branch when the shunt switch is closed and the RF transceiver front end is operable in a transmitter mode. The length of the transmission line may be zero to less than λ/4 at the operating frequency of the RF transceiver.)

1. An RF transceiver front-end having an operating frequency, the RF transceiver front-end comprising:

a receiver branch comprising a length of transmission line, an impedance matching network, a shunt switch arranged downstream of the impedance matching network, and a further receiver component arranged downstream of the shunt switch, wherein the receiver branch has a receiver branch input impedance and the further receiver component has a further receiver component input impedance; and

a transmitter branch, wherein the impedance matching network is configured to transform the further receiver component input impedance to match the receiver branch input impedance when the shunt switch is open and the RF transceiver front end is operable in a receiver mode, and wherein the impedance matching network is further configured to transform the input impedance of the shunt switch to present an open circuit as the receiver branch input impedance when the shunt switch is closed and the RF transceiver front end is operable in a transmitter mode, and the length of the transmission line is less than λ/4 for the operating frequency.

2. The RF transceiver front-end of claim 1, characterized in that the further receiver component is a low noise amplifier and the further receiver component input impedance is a low noise amplifier input impedance.

3. The RF transceiver front-end of claim 1, characterized in that the further receiver component is a pre-matching network and the receiver branch further comprises a low noise amplifier arranged downstream of the pre-matching network, and wherein the further receiver component input impedance is a pre-matching network input impedance.

4. The RF transceiver front-end of any of claims 1 to 3, characterized in that the impedance matching network is configured to act as a low-pass network.

5. The RF transceiver front-end of claim 4, characterized in that the impedance matching network comprises an inductance arranged in series and a capacitance arranged in parallel.

6. The RF transceiver front-end of claim 5, characterized in that the capacitance is upstream of the inductance or the capacitance is downstream of the inductance.

7. The RF transceiver front-end of any of claims 1 to 3, characterized in that the impedance matching network is configured to act as a high-pass network.

8. A package comprising an integrated circuit, wherein the integrated circuit is configured to provide an RF transceiver front-end according to any one of claims 1 to 7.

9. A time division duplex communication system, characterized in that it comprises an RF transceiver front-end according to any of claims 1 to 7 or a package according to claim 8.

10. A method of operating an RF transceiver front-end having a receiver branch and a transmitter branch connected to a common antenna, wherein the receiver branch comprises a shunt switch arranged downstream of an impedance matching network and a further receiver component downstream of the shunt switch, the method comprising:

opening a shunt switch in the receiver branch and matching an input impedance of the receiver branch with an input impedance of the further receiver component using the impedance matching network upon reception; and

closing the shunt switch in the receiver branch and transforming an input impedance of the shunt switch using the impedance matching network at transmit time to present an open circuit as the input impedance of the receiver branch.

Technical Field

This description relates to switching Radio Frequency (RF) signals, and in particular to switching RF signals at an RF transceiver front end.

Background

RF signals are used in a variety of applications and can present a number of problems, many of which can be associated with relatively high frequency RF signals, typically in the GHz portion of the RF frequency range.

RF signals are particularly useful in wireless communication applications, including various applications in so-called 5G (5 th generation) communications.

For example, Radio Frequency (RF) switches are used in RF transceiver front ends and need to be able to withstand worst case maximum voltage swings during signal transmission. Some RF transceiver front ends typically use a stack of multiple switching transistors in series to withstand large voltage swings during transmission due to the breakdown voltage limitations of the individual transistors used for switching. However, with more stacked transistor switches, the insertion loss will increase, which lowers the overall noise figure of the receive branch (receivinglmb) of the transceiver.

An alternative approach is to use quarter-wave (λ/4) switches to avoid the use of multiple stacked transistors in series in the receiver branch and to ensure large signal swing persistence. However, a disadvantage of the λ/4 switch is that it is only suitable for use at higher operating frequencies (e.g., greater than about 60 GHz). When the operating frequency is low, the physical length of the transmission line required to implement the λ/4 switch becomes long. Therefore, the physical transmission line increases in size and has high insertion loss, and thus the receiver noise figure decreases.

Therefore, a switchable RF transceiver front-end with good performance in the receiver branch would be beneficial.

Disclosure of Invention

According to a first aspect of the present disclosure, there is provided an RF transceiver front-end having an operating frequency, the RF transceiver front-end comprising: a receiver branch comprising a length of transmission line, an impedance matching network, a shunt switch arranged downstream of the impedance matching network, and a further receiver component arranged downstream of the shunt switch, wherein the receiver branch has a receiver branch input impedance and the further receiver component has a further receiver component input impedance; and a transmitter branch, wherein the impedance matching network is configured to transform the further receiver component input impedance to match the receiver branch input impedance when the shunt switch is open and the RF transceiver front end is operable in a receiver mode, and wherein the impedance matching network is further configured to transform the input impedance of the shunt switch to present an open circuit as the receiver branch input impedance when the shunt switch is closed and the RF transceiver front end is operable in a transmitter mode, and a length of a transmission line is less than λ/4 for the operating frequency.

In one or more embodiments, the further receiver component may be a low noise amplifier and the further receiver component input impedance may be a low noise amplifier input impedance.

In one or more embodiments, the further receiver component may be a pre-matching network and the receiver branch may further comprise a low noise amplifier arranged downstream of the pre-matching network, and wherein the further receiver component input impedance is a pre-matching network input impedance.

In one or more embodiments, the impedance matching network may be configured to act as a low pass network. The low pass network may have a cut-off frequency at least equal to or greater than the operating frequency. The low pass network may have a resonant frequency at least equal to or greater than the operating frequency.

In one or more embodiments, the impedance matching network may include an inductance arranged in series and a capacitance arranged in parallel.

In one or more embodiments, the capacitance may be upstream of the inductance or the capacitance may be downstream of the inductance.

In one or more embodiments, the impedance matching network may be configured to act as a high pass network. The high pass network may have a cutoff frequency at least equal to or greater than the operating frequency. The high pass network may have a resonant frequency at least equal to or greater than the operating frequency.

In one or more embodiments, the impedance matching network may include a series arrangement of capacitors and a parallel arrangement of inductors.

In one or more embodiments, the inductance may be upstream of the capacitance or the inductance may be downstream of the capacitance.

In one or more embodiments, the length of the transmission line is zero.

In one or more embodiments, the operating frequency is less than 60GHz, 50GHz, or 40 GHz.

In one or more embodiments, the operating frequency is less than 20 GHz.

In one or more embodiments, the operating frequency is in the range of 10GHz to 100 GHz.

In one or more embodiments, the operating frequency is in the range of 20GHz to 50 GHz.

In one or more embodiments, the operating frequency is in the range of 24GHz to 45 GHz.

According to a second aspect of the present disclosure there is provided a package comprising an integrated circuit, wherein the integrated circuit is configured to provide an RF transceiver front-end according to the first aspect and any preferred features thereof.

In one or more embodiments, the package may be a Front End Integrated Circuit (FEIC), and in particular may be a millimeter wave FEIC.

According to a third aspect of the present disclosure there is provided a wireless communication device or system comprising an RF transceiver front-end according to the first aspect or a package according to the second aspect.

In one or more embodiments, the wireless communication device or system may be a time division duplex communication device or system.

According to a fourth aspect of the present disclosure, there is provided a method of operating an RF transceiver front-end having a receiver branch and a transmitter branch connected to a common antenna, wherein the receiver branch comprises a shunt switch arranged downstream of an impedance matching network and a further receiver component downstream of the shunt switch, the method comprising: opening a shunt switch in the receiver branch and matching the input impedance of the receiver branch with the input impedance of the further receiver component using the impedance matching network upon reception; and closing the shunt switch in the receiver branch and transforming the input impedance of the shunt switch to present an open circuit as the input impedance of the receiver branch using the impedance matching network when transmitting.

Features of the first aspect may also be corresponding features of the fourth aspect.

Drawings

Embodiments of the invention will now be described in detail, by way of example only, and with reference to the accompanying drawings, in which:

fig. 1 shows a schematic block diagram of a first RF transceiver front-end according to the present invention;

fig. 2 shows a schematic block diagram of a second RF transceiver front-end according to the present invention;

fig. 3 shows a circuit diagram of a first embodiment of a portion of the RF transceiver front-end shown in fig. 2 in a receive mode of operation;

FIG. 4 shows the circuit diagram of FIG. 3 in a transmit mode of operation;

FIG. 5 shows a Smith chart illustrating possible ranges of input impedance values for the pre-match networks of the circuits shown in FIGS. 3 and 4;

FIG. 6 shows a Smith chart illustrating particular input impedance values of the pre-match networks of the circuits shown in FIGS. 3 and 4;

fig. 7 shows a circuit diagram of a second embodiment of a portion of the RF transceiver front-end shown in fig. 1 in a receive mode of operation;

FIG. 8 shows the circuit diagram of FIG. 7 in a transmit mode of operation;

FIG. 9 shows a Smith chart illustrating possible ranges of input impedance values for the pre-match networks of the circuits shown in FIGS. 7 and 8;

fig. 10 shows a circuit diagram of a third embodiment of a portion of the RF transceiver front-end shown in fig. 1 in a receive mode of operation;

FIG. 11 shows the circuit diagram of FIG. 10 in a transmit mode of operation;

FIG. 12 shows a Smith chart illustrating possible ranges of input impedance values for the pre-match networks of the circuits shown in FIGS. 9 and 10;

FIG. 13 shows a Smith chart illustrating possible input impedance values for the pre-match networks of the circuits shown in FIGS. 9 and 10; and is

Fig. 14 shows a flow chart illustrating a method of operating an RF transceiver front end.

Similar items in different figures share the same reference numerals unless otherwise specified.

Detailed Description

Referring to fig. 1, a schematic block diagram of an RF transceiver front-end device 100 attached to an antenna 102 is shown. The front-end device 100 may be in the form of an integrated circuit provided in a package. In other embodiments, the antenna 102 may also be provided as part of the integrated circuit 100. The RF transceiver front-end, also sometimes referred to simply as a front-end IC, also has a connection 104 for receiving and passing on RF signals from other parts of the larger system, which RF signals are to be transmitted through the antenna 102 or have been received by the antenna 102. The RF signal may typically be in the range of about 20GHz to 60 GHz.

For example, the front end may be used in devices and systems that conform to the 5G millimeter wave frequency range of 24GHz to 45 GHz.

However, the method can be more generally applied at sufficiently high frequencies, typically from 20GHz to greater, to allow for high efficiency silicon implementations.

In some applications (e.g., phased antenna arrays), there may be multiple RF transceiver front ends, each having a respective antenna and a respective RF connection. One or more RF transceiver front ends may be used in a variety of applications including 5G telecommunications. The methods described herein may also be used for FEIC based on the application of phased array concepts, 60GHz communication standards, and E-band communication at 85 GHz.

The RF transceiver front-end arrangement 100 comprises a transmit branch 110 connected between an antenna connection 103 for the antenna 102 and the RF connection switch 106, and a receive branch 120 also connected between the antenna connection 103 and the RF connection switch 106. The RF connection switch 106 is used to selectively provide a signal path between the antenna and the RF connection through either the transmit branch 110 or the receive branch 120.

The transmit branch 110 may include various components 112 as are typically provided in transceivers and are not the focus of the present invention. For example, as shown in fig. 1, the transmit components in the transmit branch may include a transmitter power amplifier 114 configured to increase the RF signal power prior to transmission through the antenna, and a transmitter switch 116. The transmitter switch may be operable to connect the power amplifier 114 to the antenna 102 during a transmit mode of operation and to isolate the power amplifier 114 from the antenna 102 during a receive mode of operation.

The receiving branch 120 may also comprise various components, some of which may be typically provided in a transceiver, and others of which form part of the present invention as explained below.

The receiving branch 120 comprises a length of transmission line 122 connected to the antenna connection 103. Unlike previous RF transceiver front ends, the transmission line 122 has a length of less than a quarter wavelength λ/4 at the operating frequency of the RF transceiver front end. An impedance matching circuit 124 is provided downstream of the transmission line and then a shunt switch 126 connected to ground is provided downstream of the impedance matching network 124. In the embodiment shown in fig. 1, a pre-matching network is provided downstream of the shunt switch 126 and before the amplifier 130, which amplifier 130 may be a low noise amplifier. The output of the low noise amplifier 130 is connected to the input of a variable gain amplifier 132, the output of the variable gain amplifier 132 is connected to a vector modulator or phase shifter 134, and the output of the vector modulator or phase shifter 134 is connected to the RF switch 106.

Fig. 2 shows a schematic block diagram of a second RF transceiver front-end arrangement 100' generally similar to the arrangement shown in fig. 1. However, in the second RF transceiver front-end 100', the pre-matching network 128 is not present between the shunt switch 126 and the amplifier 130. Thus, in some embodiments of the present invention, the pre-match network 128 may not be used, depending on a number of factors including the input impedance presented by the amplifier 130.

It should be understood that the specific receiver components and transmitter components illustrated in fig. 1 and 2 are by way of example only, and the method is not limited to those specific transmitter component arrangements and receiver component arrangements. Instead, the method described herein relates more to the connection 103 between the transmitter and receiver branches of the transceiver.

The illustrated series of impedance matching network 124, shunt switch 126, and amplifier 130 may be used to reduce the physical length of the transmission line 122 in the receiver branch to less than λ/4, and in some particular cases, the transmission line 122 may even be omitted from the receiver branch. With the reduced physical length of the transmission line, the transmission line 122 has a smaller size, the receiver branch 120 has a lower insertion loss and an improved receiver noise figure. Furthermore, this approach may extend the operating frequency of the RF transceiver front-end device to lower frequencies, e.g. on the order of several GHz, e.g. 10 GHz. The upper end with respect to the application range may be about 100 GHz.

In the receiver branch, a shunt switch 126 is applied downstream of the impedance matching network 124 and between the impedance matching network 124 and a pre-matching network 128 (when used) or amplifier 130. During the receiver mode of operation, with the shunt switch 126 open, the pre-match network 128 transforms the input impedance of the amplifier 130 to a specified impedance (Zpm), and the impedance match network 124 transforms Zpm to 50 Ω, the impedance of the transmission line 122. In the transmitter mode of operation, with shunt switch 126 closed, impedance matching network 124 transforms the very low impedance (≈ 0 Ω) provided by closed shunt switch 126 into an inductive impedance, which reduces the physical length of the transmission line that needs to be provided so as to achieve an open input impedance of receiver branch 120 and thus effectively prevents leakage of high-power RF signals into receiver branch 120.

In general, the particular value Zpm of the input impedance of the pre-match network is not limited to a single value and may have a range of values. As described in more detail below, the particular topology of the impedance matching network 124 may affect the range of Zpm values as well as the physical length of the transmission line 122. As mentioned above, the pre-matching network is optional and may be omitted entirely in some cases when the input impedance of the amplifier naturally meets the requirement of Zpm values. Furthermore, the technology is independent of IC technology and can be applied in, for example, CMOS, BiMCOS and GaAs solutions.

Fig. 3 and 4 show a circuit diagram 200 of a first embodiment of portions of a receiver branch and a transmitter branch of the RF transceiver front-end shown in fig. 1 in a receive mode of operation and a transmit mode of operation, respectively. As shown in fig. 3, in the receive mode of operation, the shunt switch 126 is open (and provides an open circuit), and as shown in fig. 4, in the transmit mode of operation, the shunt switch 126 is closed (and substantially provides a short circuit). The impedance matching network 124 is configured to have low pass performance. In particular, the impedance matching network includes a capacitor 210 arranged in parallel and connected to ground and an inductor 212 arranged in series and downstream of the capacitor.

It will now be explained that the physical length of the transmission line 122 is reduced to less than lambda/4. For simplicity of explanation, it is assumed that the pre-matching network 128 is configured to transform the input impedance of the low noise amplifier 130 to 10 Ω.

When operating in receiver mode, as shown in fig. 3, the low-pass LC network 124 transforms 10 Ω to 50 Ω, and thus the input impedance Z of the impedance matching network 124_inIs 50 omega. In the transmitter mode, as shown in fig. 4, the same low-pass LC network 124 transforms the low impedance (almost the short circuit provided by the closed shunt switch 126) to j x 100 Ω. Thus, a transmission line with a physical length of 0.07 λ is sufficient to transform j x 100 Ω to a high impedance (almost open circuit), and thus the input impedance Z of the transmission line 122 and the receiver branch in the transmitter mode_inVery large and almost open circuit. The physical length of transmission line 122 in this example is only 28% (i.e., 0.07/0.25 ≈ 28%) compared to the λ/4 length transmission line approach.

For the low pass impedance matching network 124 shown in fig. 3 and 4, the input impedance requirement of the pre-matching network 128 is Z_inZpm — Rpm + j Xpm, where Rpm is the resistance of the pre-match network 128 and Xpm is the reactance of the pre-match network 128. Since the impedance matching network 124 transforms Zpm to 50 Ω in the receiver mode and 0 Ω to inductive in the transmitter mode, respectively:

the above equations can be rearranged to obtain:

fig. 5 shows a graph of the input impedance range of the pre-matching network in smith chart 220 meeting this criteria, and where the shaded region 222 in fig. 5 shows Zpm values that can work with the low-pass impedance matching network 124 as shown in fig. 3 and 4 to reduce the length of the transmission line 122 below λ/4.

As mentioned above, in some cases, the length of the transmission line 122 may be reduced to zero, and thus the transmission line 122 may be omitted from the receiver branch 120.

If in fig. 3 and 4 the impedance matching network 124 transforms the input impedance Zpm of the pre-matching network 128 to 50 Ω in the receiver mode (fig. 3) and 0 Ω to high impedance (open circuit) in the transmitter mode (fig. 4), then:

the above equations can be rearranged to obtain:

in this case, the impedance matching network LC circuit resonates at the operating frequency in the transmitter mode and the transmission line length is reduced to zero, and thus the transmission line 122 may be omitted.

Fig. 6 shows a smith chart 230 including a plot 232 of the range of impedance values of Zpm, which Zpm may work with the impedance matching network 1234 of fig. 3 and 4 to allow the transmission line 122 to be omitted.

Fig. 7 and 8 show a circuit diagram 240 of a second embodiment of portions of a receiver branch and a transmitter branch of the RF transceiver front-end shown in fig. 1 in a receive mode of operation and a transmit mode of operation, respectively. As shown in fig. 7, in the receive mode of operation, the shunt switch 126 is open (and provides an open circuit), and as shown in fig. 8, in the transmit mode of operation, the shunt switch 126 is closed (and substantially provides a short circuit). The impedance matching network 124 is again configured to have low pass performance. In particular, the impedance matching network includes an inductance 232 arranged in series and a capacitance 244 connected in parallel to ground and downstream of the inductance 244.

Similar to the first embodiment, the low-pass impedance matching network 124 transforms Zpm to 50 Ω in the receiver mode (fig. 7) and transforms 0 Ω to high impedance (open circuit) in the transmitter mode (fig. 8):

rearranging the above formula yields:

X_pm ²＞50R_pm-R_pm ²

fig. 9 shows a smith chart 250 including a region 252 showing Zpm values, the Zpm may work with the low pass impedance matching network 124 of fig. 7 and 8 to reduce the length of the transmission line 122 below λ/4.

Similar to the first and second embodiments, fig. 10 and 11 show a circuit diagram 260 of a third embodiment of portions of the receiver and transmitter branches of the RF transceiver front-end shown in fig. 1 in a receive mode of operation and a transmit mode of operation, respectively. In the third embodiment, the impedance matching network 124 is configured to have high-pass performance. In particular, the impedance matching network 124 includes an inductance 262 arranged in parallel and connected to ground and a capacitance 264 connected in series and downstream of the inductance 262.

Similar to the first and second embodiments, the low-pass impedance matching network 124 transforms Zpm to 50 Ω in the receiver mode (fig. 10) and transforms 0 Ω to high impedance (open circuit) in the transmitter mode (fig. 11):

and after rearrangement yields:

fig. 12 shows a smith chart 270 including a region 272 showing Zpm values, the Zpm may work with the high-pass impedance matching network 124 of fig. 10 and 11 to reduce the length of the transmission line 122 below λ/4.

The condition for reducing the length of the transmission line 122 to zero and thus omitting the transmission line is:

fig. 13 shows a smith chart 280 including a line 280 illustrating Zpm values, the Zpm may work with the high-pass impedance matching network 124 of fig. 10 and 11 to reduce the length of the transmission line 122 to zero and thus achieve an omitted transmission line.

As described above, and as shown in fig. 2, in some embodiments, the pre-match network 128 may be omitted. In that case, the impedance matching network 124 is configured to match the input impedance Z of the low noise amplifier in the receiver mode_lnaTransforming to the input impedance of the transmission line or receiver branch (50 Ω in the above example) and transforming 0 Ω to a high impedance (open circuit) in the transmitter mode.

In some embodiments, the RF transceiver front-end 100 shown in fig. 1 and 2 may be provided in the form of an integrated circuit in a package.

Fig. 14 shows a flow chart 300 illustrating a method of operating an RF transceiver front end. The method begins 302 with operating the entire system of which RF transceiver front-end 100 forms a part. At 304, the system determines whether the front end is to be used in a transmit mode or a receive mode. It is determined that the front end is to be used for transmission and then at 306 the shunt switch is closed or remains closed if already closed and the transmit branch is used for transmission at 308. As explained above, the short circuit provided by the closed shunt switch is effectively transformed by the impedance matching network into an open input impedance for the receiving branch, and thus if any of the signals to be transmitted can leak into the receiving branch, the leaked signal is very little.

If it is determined at 310 that the system continues to be operated, processing returns to 304, as illustrated by process flow 312, where a determination is again made at 304 whether the system is transmitting or receiving. If the system is receiving, then at 314 the shunt switch is open if previously closed or remains open if previously open, and at 316 the input impedance of the receive branch is matched to the input impedance of the downstream portion of the receive branch, such as when the impedance matching network 124 provides the low noise amplifier 130 or the pre-matching network 128. Thus, the received RF signal is efficiently introduced to the receiving branch and the downstream component due to the good input impedance matching between the receiving branch and the downstream component.

The method may then continue and repeat with the system controlling the opening and closing of the shunt switch, depending on whether the transceiver is in a receive mode of operation or a transmit mode of operation.

The techniques described herein may be used for the front end of any Time Division Duplex (TDD) system that operates at high frequencies. In such systems, some sort of switching functionality is required at the antenna port to enable reception or transmission. This technique extends the operating frequency of the λ/4-type switch from very high frequencies (> 60GHz) to lower frequencies, as the lower frequencies allow the length of the transmission line to be reduced, in some cases to zero, and will reduce insertion loss and improve the noise figure of the receiver. The reduced physical size of the transmission line also improves the simplicity with which the front end can be implemented as an integrated circuit.

In this specification, example embodiments have been presented in terms of a selected set of details. However, those of ordinary skill in the art will understand that many other example embodiments may be practiced that include a different selected set of these details. The following claims are intended to cover all possible example embodiments.

Any instructions and/or flowchart steps may be executed in any order, unless a specific order is explicitly stated. Further, those skilled in the art will recognize that while one example set of instructions/methods has been discussed, the materials in this specification can be combined in various ways to produce other examples as well, and will be understood in the context provided by this detailed description.

While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. However, it is to be understood that other embodiments are possible in addition to the specific embodiments described. All modifications, equivalents, and alternative embodiments falling within the scope of the appended claims are also contemplated.