Wideband radio-frequency transceiver front-end and operation method thereof

A wideband radio-frequency transceiver front-end is provided. The transceiver front-end includes an antenna port and a transmission path coupled to the antenna port comprising a power amplifier and a first matching network. The transceiver front-end further includes a reception path coupled to the antenna port comprising a low noise amplifier and a second matching network. Furthermore, the transceiver front-end includes an impedance inverter coupled in-between the antenna port and the second matching network. Moreover, the transceiver front-end includes a controller comprising switching arrangement for a gate and a drain of the power amplifier. In this context, the controller is configured to initiate a first reception mode by connecting the gate of the power amplifier to ground and by connecting the drain of the power amplifier to a supply voltage.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a non-provisional patent application claiming priority to European Patent Application No. EP 20201999.8 filed Oct. 15, 2020, the contents of which are hereby incorporated by reference.

FIELD OF THE DISCLOSURE

This disclosure generally pertains to transceivers and methods of operation thereof. More particularly, this disclosure pertains to wideband radio-frequency transceivers.

BACKGROUND

This description relates to a radio-frequency (RF) transceiver operating at millimeter waves or Terahertz frequencies, especially to a wideband front-end circuit for wireless communication in time-division duplexing (TDD) systems.

Generally, in a TDD RF transceiver front-end, noise figure (NF) acts as the key specification, especially while the transceiver is in receiving mode, which affects the system performance significantly. Presently, wide operational bandwidth is available for wireless communication at millimeter waves and Terahertz frequencies. However, it is hard to keep a low NF for the entire wide operation bandwidth. In order to maintain good RF performance for TDD RF transceiver front-end at millimeter waves, a low NF of the front-end circuit is required within a wide operation bandwidth.

For example, the document US 2020/0083924 A1 shows a transmit receive switch system, where a symmetric λ/4 transmission line switching topology is incorporated in order to perform impedance matching on both transmitter and receiver ends. However, the presence of passive components at the transmission path disadvantageously leads to higher insertion loss, especially at higher frequencies (Terahertz), which results in lower output power from the power amplifier at the transmitter end.

This description pertains to providing a wideband RF transceiver front-end and an operation method for the same, which can overcome the aforementioned limitations.

SUMMARY

This description describes features of a wideband RF transceiver front-end and features of a method, as well as further developments.

According to a first example implementation, a wideband radio-frequency transceiver front-end is provided. The transceiver front-end includes an antenna port and a transmission path coupled to the antenna port comprising a power amplifier and a first matching network. The transceiver front-end further includes a reception path coupled to the antenna port comprising a low noise amplifier and a second matching network. Furthermore, the transceiver front-end includes an impedance inverter coupled in-between the antenna port and the second matching network. Moreover, the transceiver front-end includes a controller comprising switching arrangement for a gate and a drain of the power amplifier.

In this context, the controller is configured to initiate a first reception mode by connecting the gate of the power amplifier to ground and by connecting the drain of the power amplifier to a supply voltage. In at least some cases, this eliminates the necessity of having passive elements at the transmission path by introducing additional switching functionalities at the power amplifier. Especially, while receiving, a first mode of operation can occur in which the transmitter power amplifier is not completely switched off, instead configures the LC resonance of the coil of the first matching network and the equivalent drain capacitance of transistors. Consequently, while receiving, the impedance looking into the transmission path from the receiving path changes according to the operation frequency. This can reduce the NF.

According to at least some instances of the first example implementation, the controller is further configured to initiate a second reception mode by connecting the gate of the power amplifier to a bias voltage and by connecting the drain of the power amplifier to ground. Therefore, while receiving, a second mode of operation that further manipulates the impedance transformation at the transmission path can occur. Hence, the combined operation of the first reception mode and the second reception mode can facilitate a low NF for a wide operation bandwidth.

According to at least some other instances of the first example implementation, the transceiver front-end further comprises a shunt switch coupled to the low noise amplifier. In this regard, the controller is further configured to initiate a transmission mode by switching on the shunt switch, thereby creating a low impedance short across the low noise amplifier. In addition to this, the controller is further configured to connect the gate of the power amplifier to a bias voltage and the drain of the power amplifier to the supply voltage during the transmission mode.

In at least some instances of the first example implementations, the shunt switch is placed across the input of the low noise amplifier, i.e., between the second matching network and the input terminals of the low noise amplifier. This provides an Electrostatic Discharge (ESD) protection topology, since any potential ESD-event current from the antenna port will be led to ground through the matching networks.

According to at least some other instances of the first example implementation, the controller is further configured to cause the shunt switch to be off during the first reception mode and/or the second reception mode. In this context, the controller may also be configured to control timing of the shunt switch when transferring from the transmission mode to the first and/or second reception mode.

According to at least some other instances of the first example implementation, the controller further comprises a switching arrangement for a gate of the low noise amplifier. In this regard, the controller is further configured to connect the gate of the low noise amplifier to ground during the transmission mode. Additionally or alternately, the controller is further configured to connect the gate of the low noise amplifier to a bias voltage during the first reception mode and/or the second reception mode. In addition, the second matching network is further configured to not only transform impedance but also to compensate any parasitic associated with the shunt switch (both on and off states) as well as for the transistors of the low noise amplifier.

According to at least some other instances of the first example implementation, the impedance inverter is a quarter-wavelength (λ/4) transmission line, configured to perform a short-to-open impedance transformation. Moreover, the impedance inverter can be implemented as a transmission line that has a length of less than λ/4 in order to match the additional impedance contribution of the second matching network.

According to at least some other instances of the first example implementation, the controller is further configured to initiate the first reception mode for a frequency band over an operating frequency band greater than or less than or equal to a center frequency. Additionally or alternately, the controller is further configured to initiate the second reception mode for a frequency band over the operating frequency band greater than or less than or equal to the center frequency.

The matching network parameters can dictate the modes of operation with respect to the operating frequency, i.e. whether it is required to initiate the first or second reception mode above or below the center frequency of the whole operation bandwidth. Operating at the center frequency is an example case among the all the possible operating frequency cases.

According to at least some other instances of the first example implementation, the operating frequency band is in the range of millimeter band. In some of the implementations, the frequency band goes up into a Terahertz frequency band. For instance, the operating frequency band can be the whole D-band, where the center frequency can be at or around 150 GHz. A wide operation bandwidth can be incorporated and by means of the first and second reception modes, a low NF is maintained throughout the operation bandwidth.

According to at least some other instances of the first example implementation, the first matching network and the second matching network are transformer based matching networks, such as transformer-type baluns. However, the first impedance matching network and/or the second impedance matching network are not limited to transformer-type baluns. For instance, the second matching network can be implemented as a LC-based matching network, i.e. the low noise amplifier is configured as single-ended version.

According to a second example implementation, a method for operating a wideband radio-frequency transceiver front-end is provided. The method comprises providing a transmission path, comprising a power amplifier and a first matching network, coupled to an antenna port. The method further comprises providing a reception path, comprising a low noise amplifier and a second matching network, coupled to the antenna port. Furthermore, the method comprises providing an impedance inverter coupled in-between the antenna port and the second matching network. Moreover, the method comprises initiating a first reception mode by connecting a gate of the power amplifier to ground and by connecting a drain of the power amplifier to a supply voltage.

According to at least some instances of the second example implementation, the method further comprises initiating a second reception mode by connecting the gate of the power amplifier to a bias voltage and by connecting the drain of the power amplifier to ground. Therefore, a transceiver front-end that operates over a wide operation bandwidth can be provided, while facilitating higher output power and higher power efficiency for the transmitter power amplifier and further maintains a low NF for the entire operation bandwidth.

According to at least some other instances of the second example implementation, the method further comprises initiating a transmission mode by switching on a shunt switch coupled to the low noise amplifier and further by connecting the gate of the power amplifier to a bias voltage and the drain of the power amplifier to the supply voltage. In addition to switching the transmission and reception path only by switching a single switch, a provision for ESD protection can also be incorporated.

According to at least some other instances of the second example implementation, the method further comprises initiating the first reception mode for a frequency band greater than or less than or equal to a center frequency and initiating the second reception mode for a frequency band greater than or less than or equal to the center frequency over an operating frequency band. Therefore, a flexible operation for the first and second reception modes is incorporated with respect to the operating bandwidth.

All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary to elucidate example embodiments, wherein other parts may be omitted or merely suggested.

DETAILED DESCRIPTION

Reference will now be made in detail to the example embodiments illustrated in the accompanying drawings. The following embodiments may, however, be variously modified and the range of the claims is not limited by the following embodiments.

FIG.1illustrates an example embodiment of the transceiver front-end100. The transceiver front-end100comprises an antenna port101and an antenna or antenna array102coupled at the antenna port101, which is terminated to ground104. The parasitic for termination is hereby illustrated as a pad capacitance103(e.g., a flip chip pad capacitance). The antenna or antenna array102can operate at millimeter wave as well as at sub-millimeter wave.

The transceiver front-end100further comprises a transmission path110that is coupled to the antenna port101. The transmission path110comprises a transmitter amplifier or transmitter power amplifier or power amplifier111and a first matching network113, such as a first transformer based impedance matching network. The power amplifier111receives baseband signal112from a baseband generator (not shown) and performs the final stage amplification to generate the transmission signal, which is transmitted through the antenna or antenna array102during transmission. Specifically, the power amplifier111operates in differential mode, where the received baseband and the amplified output signals are differential type signals. The output of the power amplifier111is coupled to the first coil114of the first matching network113. The second coil116of the first matching network113is coupled to the antenna port101.

The transceiver front-end100further comprises a reception path120that is coupled to the antenna port101. The reception path comprises a receiver amplifier or receiver low noise amplifier or low noise amplifier121, a second matching network123(such as a second transformer based impedance matching network), and an impedance inverter125. The low noise amplifier121amplifies the received signal, which is received through the antenna or antenna array102during reception and provides amplified received signal122at its output. Specifically, the low noise amplifier121operates in differential mode, where the received signal and the amplified received signal are differential type signals.

The input terminals of the low noise amplifier, i.e., the gates of the transistors, are coupled to a switch127in shunt, hereinafter referred as a shunt switch127. The terminals are further coupled to the first coil124of the second matching network123. The second coil126of the second matching network123is coupled to an impedance inverter. In at least some embodiments, the impedance inverter is realized by a transmission line having a length shorter than one quarter-wavelength. In other words, the impedance inverter125is coupled in-between the antenna port101and the second coil126of the second matching network123.

It is to be noted that the second matching network123is not limited to a transformer based matching network, since a LC based matching network can also be implemented, where the low noise amplifier121will perform single-ended operation.

The transceiver front-end100further comprises a controller105that operates on the shunt switch127, therefore is configured to cause the shunt switch127to be on and off as needed for transmission and reception operations, respectively. The controller105further includes provisions for different voltage levels, i.e., the supply voltage Vdd, the gate bias voltage Vg and its variances, and ground potential (0V). Especially, the controller105comprises supply switch or switches in order to perform the switching of potentials ranging from the ground potential (0V) to the supply voltage (Vdd). The switch control logic can be transmitted via control signals (depicted as dashed lines) from the controller105to the respective paths110,120.

Next,FIG.2illustrates an example embodiment of the transceiver front-end in transmission mode200, hereinafter referred as TX-mode. The power amplifier111illustrated in detail, showing the differential arrangement of two transistors211,213with their respective gate212, drain214and source216terminals. Although, the topology shows only one transistor per path, it is conceivable that the topology can be extended to a larger number of stacked-transistor power amplifier topology. Furthermore, the power amplifier111can also be implemented as a cross-capacitive coupled common source power amplifier.

In order to initiate the TX-mode200, the controller105causes the shunt switch127to be on, thereby creating a low impedance short across the inputs of the low noise amplifier121(i.e. across the first coil124of the second matching network123). In addition, the controller105connects the gates224of the low noise amplifier121(i.e., the transistor switches of the low noise amplifier121) to ground104(0V). This results in the deactivation of the reception path120while keeping the transmission path110active.

The second matching network123allows avoiding the termination of the inactive reception path directly to ground104. The second matching network123also takes into account the parasitic associated with the shunt switch127when it is switched on.

The low impedance short caused by the shunt switch127across the first coil124of the second matching network123is transformed into a high impedance by the impedance inverter125, seen at the antenna port101from the perspective of the power amplifier111. The impedance inverter125is, for instance, a transmission line that has a length of slightly less than λ/4, which takes into account the additional impedance contribution of the second matching network123. The combined operation of the impedance inverter125and the second matching network123provides a combined impedance transformation of λ/4. The high impedance can be achieved based on resonance between cumulative capacitance of transmission line and pad capacitances and the transmission line impedance of the impedance inverter125.

Furthermore, during the TX-mode200, the controller105connects the drain of the power amplifier111, especially the drains214of the transistors211,213to a supply voltage Vdd. The controller105further connects the gate of the power amplifier111, especially the gates212of the transistors to a bias voltage Vg. The voltage switching is performed at a center tap of the first coil114of the first matching network113and at a center tap of the first coil124of the second matching network123for the power amplifier111and the low noise amplifier121, respectively.

Next,FIG.3illustrates a first example embodiment of the transceiver front-end in reception mode300, hereinafter referred as PA-SW-OFF. In order to initiate the PA-SW-OFF300, the controller105connects the gate of the power amplifier111, especially the gates212of the transistors to ground104(0V). Furthermore, the controller105connects the drain of the power amplifier111, especially the drains214of the transistors to the supply voltage Vdd. This effectively disables the power amplifier111to a high impedance state, which provides adequate isolation from the antenna port101, thereby deactivating the transmission path110.

Moreover, during the PA-SW-OFF300, the controller105causes the shunt switch127to be off, which presents an off switch capacitance across the low noise amplifier121(i.e., across the first coil124of the second matching network123). In addition, the controller105connects the gate of the low noise amplifier121, especially the gates224of the transistors to the bias voltage Vg, thereby activating the reception path120. The second matching network123further takes into account the parasitic associated with the shunt switch127when it is switched off.

Next,FIG.4illustrates a second example embodiment of the transceiver front-end400, hereinafter referred as PA-SW-ON, in reception mode. In order to initiate the PA-SW-ON400, the controller105connects the gate of the power amplifier111, especially the gates212of the transistors to a bias voltage Vsw. The bias voltage Vsw can be lower or higher than the nominal bias voltage Vg. The bias voltage Vsw can be within the range of the nominal bias voltage Vg and the supply voltage Vdd. Alternately, the bias voltage Vsw is as high as the supply voltage Vdd. In at least some embodiments, the bias voltage Vsw is sufficiently high in order to enable the transistors of the power amplifier111to stay in the ohmic region.

Furthermore, the controller105connects the drain of the power amplifier111, especially the drains214of the transistors to the ground104(0V). Hence, during PA-SW-ON400, the gate biasing voltages of the power amplifier111are set to a certain value to turn on the transistors while grounding the supply voltage of the power amplifier111. This effectively configures the power amplifier111to a low impedance shunt switch. The first matching network113performs a short to open impedance transform, i.e., transforming the low impedance of the power amplifier111operating as a low impedance shunt switch into a high impedance. This provides adequate isolation from the antenna port101, thereby deactivating the transmission path110.

Moreover, during the PA-SW-ON400, the controller105causes the shunt switch127to be off, which presents an off switch capacitance across the low noise amplifier121(i.e., across the first coil124of the second matching network123). In addition, the controller105connects the gate of the low noise amplifier121, especially the gates224of the transistors to the bias voltage Vg, thereby activating the reception path120. The second matching network123further takes into account the parasitic associated with the shunt switch127when it is switched off.

Therefore, during the TX-mode200, the power amplifier111operates as a large amplifying device, while the low impedance short across the low noise amplifier121is converted into a high impedance in order to achieve a high transmission efficiency. On the other hand, during the PA-SW-OFF300, the power amplifier111is disabled to a high impedance state in order to provide good isolation and hence low NF in the receiver topology. Additionally, during the PA-SW-ON400, the power amplifier111is disabled to a low impedance shunt while converting the low impedance into a high impedance at the antenna port101. This further provides adequate isolation from the antenna port101and hence low NF in the receiver topology. It is to be noted that the PA-SW-OFF300and the PA-SW-ON400modes are implemented at different frequencies and they do not co-exist at one frequency.

Next,FIG.5illustrates example NF simulations for the PA-SW-OFF300and PA-SW-ON400. The horizontal axis denotes the operating frequency range in Gigahertz and the vertical axis denotes the NF in decibels. The operation frequency range correspond to the whole D-band, as illustrated herein, where the center frequency is at or around 150 GHz. However, it is conceivable that the illustration is to exemplify the NF reduction technique and the operation frequency range is not limited to the D-band. For example, the operation frequency band can be in the range of millimeter wave as well as sub-millimeter wave range.

In this example, three observation frequencies are selected in order to demonstrate the NF fluctuation over the frequency range. A first observation frequency is selected at 135 GHz, a second observation frequency is selected around the center frequency at 149 GHz and a third observation frequency is selected at 165 GHz. The solid line represents the PA-SW-OFF300mode and the dashed line represents the PA-SW-ON400mode.

At the first observation frequency, the receiver NF501for PA-SW-OFF is approximately 5.05 dB and the receiver NF502for PA-SW-ON is approximately 6.35 dB. At the second observation frequency, the receiver NF503for PA-SW-OFF is approximately 5.81 dB and the receiver NF504for PA-SW-ON is approximately 5.81 dB. At the third observation frequency, the receiver NF505for PA-SW-OFF is approximately 9.22 dB and the receiver NF506for PA-SW-ON is approximately 5.93 dB.

It can be seen that, the NF degrades drastically for PA-SW-OFF as the operating frequency increases, whereas the NF is somewhat constant for PA-SW-ON over the whole frequency range. However, at lower frequencies, especially below the center frequency, the NF performance for PA-SW-OFF is superior to the NF performance for PA-SW-ON by approximately 1 dB. Therefore, the example embodiments can incorporate both PA-SW-OFF and PA-SW-ON modes over the whole operation bandwidth, where one mode is active for frequencies lower that the center frequency and the other mode is active for frequencies higher that the center frequency.

In this example, it can be seen that the NF performance of PA-SW-OFF is superior to PA-SW-ON for frequencies lower than the center frequency, therefore the PA-SW-OFF is initiated for frequencies lower than the center frequency. Further, the PA-SW-ON is initiated for frequencies higher than the center frequency, since the NF performance of PA-SW-ON is superior to the PA-SW-OFF for frequencies higher than the center frequencies. However, for other range of operating frequency bands, the initiation of both PA-SW-OFF and PA-SW-OFF with respect to their operating frequency range largely depends on the matching network parameters.

AlongFIG.6andFIG.7, an example test bench environment simulating NF degradation due to transmission path loss is shown. In particular,FIG.6shows an adopted test bench for simulating the NF degradation due to transmission path loss. The simulated impedance ZM looking into the transmission path and NF over frequencies are illustrated inFIG.7.

The operation frequency range illustrated herein corresponds to the whole D-band, where the center frequency is at 150 GHz. However, it is conceivable that the illustration is to exemplify the NF degradation and the operation frequency range is not limited to the D-band. The operation frequency band can be in the range of millimeter wave as well as sub-millimeter wave range.

The horizontal axis denotes the operating frequency range in Gigahertz. The vertical axis for the simulation at top denotes the real ZM in ohm. In addition, the vertical axis for the simulation at middle denotes the imaginary ZM in ohm. Further, the vertical axis for the simulation at bottom denotes the NF in decibels. For all three simulations, three observation frequencies are selected over the frequency range. A first observation frequency is selected at 135 GHz, a second observation frequency is selected at the center frequency at 150 GHz and a third observation frequency is selected at 165 GHz. The solid line represents the PA-SW-OFF300mode and the dashed line represents the PA-SW-ON400mode.

For the simulation at top, the real value of ZM at 135 GHz, denoted by the circle701, is around 65 ohm and 98 ohm for PA-SW-OFF and PA-SW-ON, respectively. In addition, the real value of ZM at 150 GHz, denoted by the circle702, is around 58 ohm and 60 ohm for PA-SW-OFF and PA-SW-ON, respectively. Furthermore, the real value of ZM at 165 GHz, denoted by the circle703, is around 113 ohm and 46 ohm for PA-SW-OFF and PA-SW-ON, respectively.

For the simulation at middle, the imaginary value of ZM at 135 GHz, as denoted by the circle704, is around −30 ohm and −72 ohm for PA-SW-OFF and PA-SW-ON, respectively. In addition, the imaginary value of ZM at 150 GHz, denoted by the circle705, is around 2 ohm and −49 ohm for PA-SW-OFF and PA-SW-ON, respectively. Furthermore, the imaginary value of ZM at 165 GHz, denoted by the circle706, is around 17 ohm and −30 ohm for PA-SW-OFF and PA-SW-ON, respectively.

It is to be noted that the combined ZM of PA-SW-OFF and PA-SW-ON modes over the whole operating frequency range has less variations that the individual ZM in PA-SW-OFF and PA-SW-ON mode, respectively. As a consequence, the matching networks, especially the second matching network123, will be benefited significantly by the proposed technique.

For the simulation at bottom, which illustrates NF degradation due to transmission path loss, the NF at 135 GHz, as denoted by the circle707, is around 1.1 dB and 1.6 dB for PA-SW-OFF and PA-SW-ON, respectively. In addition, the NF at 150 GHz, as denoted by the circle708, is around 1.6 dB and 1.5 dB for PA-SW-OFF and PA-SW-ON, respectively. Furthermore, the NF at 165 GHz, as denoted by the circle709, is around 3.4 dB and 1.4 dB for PA-SW-OFF and PA-SW-ON, respectively. This further verifies the proposed NF reduction technique by using switching functionality in the power amplifier side, i.e., to switch the power amplifier operation between PA-SW-OFF and PA-SW-ON around the center frequency over the whole operation frequency range.

Next,FIG.8illustrates an example embodiment of the method using blocks800-804. At block800, a transmission path is provided that comprises a power amplifier and a first matching network, where the transmission path is coupled to an antenna port.

Next, at block801, a reception path is provided that comprises a low noise amplifier and a second matching network, where the reception path is coupled to the antenna port.

Next, at block802, an impedance inverter is provided that is coupled in-between the antenna port and the second matching network.

Next, at block803, a first reception mode is initiated by connecting a gate of the power amplifier to ground and by connecting a drain of the power amplifier to a supply voltage.

Next, at block804, a second reception mode is initiated by connecting the gate of the power amplifier to a bias voltage and by connecting the drain of the power amplifier to ground.

In at least some embodiments of the method represented byFIG.8, a transmission mode is initiated by switching on a shunt switch coupled to the low noise amplifier and further by connecting the gate of the power amplifier to a bias voltage and the drain of the power amplifier to the supply voltage.

The example embodiments can be implemented by hardware, software, or any combination thereof. For example, various embodiments may be implemented by one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, or the like.

In addition to the one or more implementations illustrated and described herein, equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In addition, while a particular feature may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and for any given or particular application.