Bidirectional active mixer
Through the bidirectional active mixer design without transconductors, the area and power consumption problems of the bidirectional RF transceiver are solved, and higher reverse isolation and broadband matching are achieved, and system performance and energy efficiency are improved.
Patent Information
- Application Number
- CN202510467854.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-14
- Publication Date
- 2025-08-01
AI Technical Summary
The existing bidirectional RF transceiver design faces problems such as high area cost, limited signal path switching performance and large local oscillator power consumption, especially in broadband systems.
Using a bidirectional active mixer without transconductors, the bidirectional operating mode is achieved by introducing switching circuits and static bias currents into the switching components, and the signals are directly coupled to the radio frequency/intermediate frequency ports, avoiding the limitation of independent transconductors, and supporting the cascade of bidirectional active amplifier circuits.
Achieve higher reverse isolation and broadband matching, simplify design, reduce additional performance losses, and improve system energy efficiency and applicability.
Smart Images
Figure CN120415331A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure belongs to the technical field of millimeter-wave radio frequency integrated circuits, and particularly relates to a bidirectional active mixer. Background Art
[0002] With the continuous development of semiconductor process nodes, in the design of modern radio frequency integrated circuits, especially radio frequency transceivers, the chip area occupied by passive networks (such as inductors, capacitors, etc.) is increasing day by day. Among them, the matching network for impedance matching is often one of the main parts of the area overhead. In order to improve the system integration, effectively utilize the chip area and reduce the cost, designing the circuit to be bidirectional and reusing passive devices such as matching networks as much as possible has become an important technical direction.
[0003] However, the traditional bidirectional design scheme of radio frequency transceivers usually faces many challenges. A common implementation method is to separately design the transmit (Tx) path and the receive (Rx) path. In this architecture, usually at least two pairs of transceiver switches are required to switch the paths of the radio frequency port signal and the baseband port signal respectively. In addition, the intermediate signal processing links between the two paths often also need to be designed separately. At the same time, in order to avoid or reduce the mutual coupling effect between the passive devices on the two paths, a certain physical distance also needs to be maintained in the layout. These factors result in the actual chip area overhead of the bidirectional transceiver using the traditional separate path design being more than twice that of a single transmit or single receive path.
[0004] Furthermore, in a broadband radio frequency system, directly setting the transceiver switch on the signal transmission path will introduce additional insertion loss, non-linearity and frequency correlation, which often become the bottleneck restricting the overall bandwidth and performance of the system.
[0005] In addition, using separate frequency conversion paths for transmission and reception (such as using two independent mixers) will also result in a doubled local oscillator (LO) network load. This not only increases the power consumption overhead of the local oscillator signal network, but also correspondingly reduces the energy efficiency of the entire system.
[0006] Therefore, the prior art often faces problems such as high area cost, signal path switch restricting performance, and large local oscillator power consumption when implementing the bidirectional radio frequency transceiver function, and an optimized solution is urgently needed. Summary of the Invention
[0007] The present disclosure proposes a cross-conduction-free bidirectional active mixer, which can overcome the technical defects of high area cost, limited bandwidth and large local oscillator load in the existing bidirectional transceiver solutions.
[0008] According to an embodiment of the present disclosure, a bidirectional active mixer is proposed, and the bidirectional active mixer includes:
[0009] A switching component including a plurality of switching transistors, wherein the control gates of the switching transistors are configured to receive a local oscillator signal; the switching component has at least one signal port node, and the signal port node is part of the source node or drain node of the switching transistors within the switching component;
[0010] A radio frequency port and an intermediate frequency port, configured such that a radio frequency signal or an intermediate frequency signal can be coupled to the at least one signal port node, and there is no independent cross-conduit with voltage-current conversion as the main function between the radio frequency port and the at least one signal port node or between the intermediate frequency port and the at least one signal port node;
[0011] A switching circuit, connected to the at least one signal port node and configured to selectively connect the at least one signal port node to a power supply terminal or a ground terminal according to a control signal to determine the operating mode of the bidirectional active mixer and provide a static bias current for the switching transistors in the switching component.
[0012] In some embodiments, the switching component has a first signal port node and a second signal port node; the radio frequency port is coupled to the first signal port node, and the intermediate frequency port is coupled to the second signal port node; the switching circuit is configured to selectively connect the first signal port node to a power supply terminal or a ground terminal, and selectively connect the second signal port node to a power supply terminal or a ground terminal.
[0013] In some embodiments, the switching component adopts a double-balanced mixer topology structure.
[0014] In some embodiments, the double-balanced mixer topology structure includes four of the switching transistors, and the four switching transistors are configured into a transistor quad array.
[0015] In some embodiments, the four switching transistors include a first pair of differentially-connected transistors and a second pair of differentially-connected transistors; the common source / drain node of the first pair of differentially-connected transistors constitutes the first signal port node; the common source / drain node of the second pair of differentially-connected transistors constitutes the second signal port node.
[0016] In some embodiments, the switching circuit includes:
[0017] A first switching unit, controlled by a first control signal, for connecting the first signal port node to the power supply terminal or the ground terminal;
[0018] A second switching unit, controlled by a second control signal, for connecting the second signal port node to the power supply terminal or the ground terminal.
[0019] In some embodiments, in the receiving mode, the first switching unit connects the first signal port node to the power supply terminal, and the second switching unit connects the second signal port node to the ground terminal; in the transmitting mode, the first switching unit connects the first signal port node to the ground terminal, and the second switching unit connects the second signal port node to the power supply terminal.
[0020] In some embodiments, the static bias current enables the switching transistor to operate in the saturation region when performing switching actions driven by the local oscillator signal.
[0021] In some embodiments, the mixer further includes at least one bidirectional active amplifier circuit, which is serially connected between the RF port and the at least one signal port node, and / or serially connected between the IF port and the at least one signal port node.
[0022] The present disclosure provides a bidirectional active mixer, which has the following beneficial effects:
[0023] First, by configuring the RF / IF ports to be directly coupled to the signal port nodes of the switching component, and there is no independent transconductance tube with the main function of voltage-current conversion, not only the bidirectional working ability is realized, but also the unidirectionality limitation introduced by the traditional transconductance stage is avoided, and moreover, the inherent trade-off between the noise figure and linearity in the traditional active mixer is eliminated, providing the possibility to achieve better performance indicators;
[0024] Second, a switching circuit connecting the signal port nodes and selectively connecting to the power supply / ground is introduced to determine the working mode and provide the static bias current. No switch is introduced in the signal path, so there is almost no additional performance loss, and it is more conducive to broadband implementation. Moreover, the provided static bias current enables the switching transistor to operate in the saturation region. Compared with the passive mixer, its reverse isolation can be significantly improved by more than 20 dB, greatly simplifying the design of the bidirectional matching network and the realization of broadband matching, and facilitating the reuse of the matching network;
[0025] Third, the core structure of this mixer allows bidirectional active amplifier circuits to be flexibly cascaded at the RF port and / or the IF port so that signals can be amplified in both working modes, thereby compensating for the losses that may occur during the mixing process or providing the required system gain, further enhancing the applicability.
[0026] Other details and advantages of the present disclosure are described in detail below. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The accompanying drawings here are incorporated into the specification and form a part of this specification, showing embodiments consistent with this specification, and are used together with the specification to explain the principles of this specification.
[0028] Figure 1(a) shows a schematic circuit diagram of a typical double-balanced active mixer in the prior art, which includes a transconductance (Gm);
[0029] Figure 1(b) shows a schematic circuit diagram of a typical double-balanced passive mixer in the prior art;
[0030] Figure 1(c) shows a schematic circuit diagram of a core switch component of a bidirectional active mixer without a transconductance provided according to an exemplary embodiment of the present disclosure;
[0031] Figure 2(a) shows the symbol of the bidirectional active amplifier 100 and a possible example of its circuit implementation;
[0032] Figure 2(b) shows a schematic circuit diagram of a bidirectional active mixer including a bidirectional active amplifier provided according to an exemplary embodiment of the present disclosure. Detailed Description of the Embodiments
[0033] Here, the exemplary embodiments will be described in detail, and the examples are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.
[0034] According to an embodiment of the present disclosure, a bidirectional active mixer is proposed, including:
[0035] A switch component including a plurality of switch transistors, the control gates of the switch transistors are configured to receive a local oscillator signal; the switch component has at least one signal port node, and the signal port node is a part of the source node or drain node of the switch transistors in the switch component;
[0036] A radio frequency port and an intermediate frequency port are configured such that a radio frequency signal or an intermediate frequency signal can be coupled to the at least one signal port node, and there is no independent transconductance with the main function of voltage-current conversion between the radio frequency port and the intermediate frequency port and the at least one signal port node;
[0037] A switching circuit, which is connected to the at least one signal port node and configured to selectively connect the at least one signal port node to a power supply terminal or a ground terminal according to a control signal to determine the operating mode of the bidirectional active mixer and provide a static bias current for the switching transistors in the switching assembly.
[0038] Figure 1(a) shows a typical double-balanced active mixer circuit structure in the prior art. This structure includes a bottom transconductance stage (formed by differential pair transistors gm1 and gm2) for converting a radio frequency input voltage signal (connected to the gates of gm1 / gm2) into a current signal. This current signal is fed into an upper switch quad (formed by switch transistors SW1, SW2, SW3, and SW4) and controlled by a local oscillator signal (connected to the gates of SW1 - SW4) for frequency mixing, and finally an intermediate frequency signal is output (extracted from the drains of SW1 - SW4 and the load). The key to this structure is the inclusion of independent transconductance tubes gm1 and gm2, but this leads to unidirectionality limitations and possible trade-offs between noise and linearity.
[0039] Figure 1(b) shows a typical double-balanced passive mixer circuit structure in the prior art. Its core only includes a switch quad formed by four switch transistors SW1, SW2, SW3, and SW4, without independent transconductance tubes. The radio frequency signal and the intermediate frequency signal are respectively coupled to different common nodes of the switch quad. Although it can work bidirectionally in terms of structure, due to the lack of a static bias current, its reverse isolation is poor, resulting in difficult bidirectional matching and usually requiring a large local oscillator drive.
[0040] FIG. 1(c) shows a schematic circuit diagram of a core switching component of a bidirectional active mixer without a cross-conduit according to an embodiment of the present disclosure. The core switching component also includes a switching quad array composed of four core switching transistors M1, M2, M3, and M4. The switching quad array includes two pairs of differentially connected transistors, M1, M2 and M3, M4. The common source / drain node of the first pair of differentially connected transistors M1, M2 constitutes the first signal port node Node_A, and the common source / drain node of the second pair of differentially connected transistors M3, M4 constitutes the second signal port node Node_B. The local oscillator signals LO+ and LO- drive the control gates of M2 / M3 and M1 / M4 respectively. The switching transistors M1, M2, M3, and M4 can be field effect transistors (FETs), such as metal oxide semiconductor field effect transistors (MOSFETs). Those skilled in the art can understand that if M1, M2, M3, and M4 are NMOS, then Node_A and Node_B are the common drain nodes of M1, M2 and M3, M4 respectively; if M1, M2, M3, and M4 are PMOS, then Node_A and Node_B are the common source nodes of M1, M2 and M3, M4 respectively.
[0041] Compared with the typical double-balanced active mixer shown in FIG. 1(a), the core switching component shown in FIG. 1(c) according to this embodiment does not include an independent cross-conduit. There is a passive network between the core switching component and the external ports Port_1 and Port_2, and the signals of the RF port and the IF port accessed through Port_1 and Port_2 are coupled to the signal port node system (including Node_A, Node_B, Node_C, Node_D) of the core switching component. Specifically, the signals can be coupled to the first signal port node Node_A and the second signal port node Node_B, which are part of the source node or drain node of the switching transistor, and / or coupled to another pair of signal port nodes Node_C and Node_D, thereby eliminating the limitation of the cross-conduit.
[0042] Compared with the typical double-balanced passive mixer shown in Fig. 1(b), the core switching component according to this embodiment shown in Fig. 1(c) introduces a switching circuit to achieve active operation and mode control. As shown in Fig. 1(c), the switching circuit may include a first switching unit connected to the first signal port node Node_A (shown as the upper shaded part in Fig. 1(c), including the switches SW_AV and SW_AG shown in Fig. 1(c)), and a second switching unit connected to the second signal port node Node_B (shown as the lower shaded part in Fig. 1(c), including the switches SW_BV and SW_BG shown in Fig. 1(c)). The first switching unit (including SW_AV and SW_AG) is controlled by a first control signal to selectively connect the first signal port node Node_A to the power supply terminal or the ground terminal; the second switching unit (including SW_BV and SW_BG) is controlled by a second control signal to selectively connect the second signal port node Node_B to the power supply terminal or the ground terminal. Through this configuration, the operating mode of the bidirectional active mixer can be determined, and a static bias current can be provided for the switching transistors M1 to M4 in the core switching component, enabling them to operate in the active state.
[0043] The connection of Node_A and Node_B to the power supply or the ground determines the main bias and the flow direction of the signal, thereby controlling the operating mode of the mixer. For example, it enables the mixer to operate in the receive mode from Port_1 to Port_2 or in the transmit mode from Port_2 to Port_1.
[0044] Assume that the signal is input from the external port Port_1 (as the RF port), and after mixing, the intermediate frequency signal is output from the external port Port_2 (as the intermediate frequency port) as the receive mode. Assume that the signal is input from the external port Port_2 (as the intermediate frequency port or the baseband port), and after mixing, the RF signal is output from the external port Port_1 (as the RF port) as the transmit mode.
[0045] Control the first switch unit to connect the first signal port node Node_A to the power supply terminal, i.e., turn on switch SW_AV and turn off switch SW_AG. At the same time, control the second switch unit to connect the second signal port node Node_B to the ground terminal, i.e., turn on switch SW_BG and turn off switch SW_BV, so as to configure the bidirectional active mixer to work in the above receiving mode. In this state, Node_A is pulled up to near the power supply voltage, providing a high-potential bias for transistors M1 and M2. Node_B is pulled down to near the ground potential, providing a low-potential reference for transistors M3 and M4. The radio frequency signal is coupled to Node_A and Node_B through Port_1 and the passive network. Driven by the local oscillator signals LO+ and LO-, the switching transistors M1 to M4 perform switching actions to mix the radio frequency signal coupled to Node_A / Node_B with the local oscillator signal. The intermediate frequency signal current generated by down-conversion mainly flows through the transistors to the lower-potential nodes Node_C and Node_D, and finally outputs to Port_2 through the passive network connected to Node_C / Node_D. At the same time, connecting Node_A to the power supply terminal and Node_B to the ground terminal provides a static bias current path for M1-M4, enabling them to work in the active state (such as the saturation region).
[0046] Control the first switch unit to connect the first signal port node Node_A to the ground terminal, i.e., turn on switch SW_AG and turn off switch SW_AV. At the same time, control the second switch unit to connect the second signal port node Node_B to the power supply terminal, i.e., turn on switch SW_BV and turn off switch SW_BG, so as to configure the bidirectional active mixer to work in the above transmitting mode. In this state, Node_A is pulled down to near the ground potential and Node_B is pulled up to near the power supply voltage. The intermediate frequency / baseband signal is coupled to nodes Node_C and Node_D through Port_2 and the passive network. The input signal modulates the current flowing through the switching transistors M1-M4. Driven by the local oscillator signals LO+ and LO-, the switching transistors M1 to M4 perform switching actions to mix the modulated signal current with the local oscillator signal (up-conversion). The radio frequency signal current generated by up-conversion mainly flows to the higher-potential nodes Node_A and Node_B, and the final radio frequency signal outputs to Port_1 through the passive network connected to Node_A / Node_B. Similarly, connecting Node_A to the ground terminal and Node_B to the power supply terminal also provides a static bias current path for M1~M4 to maintain their active working state (such as the saturation region).
[0047] In summary, the core switch component shown in Fig. 1(c) according to the present disclosure realizes bidirectional active mixing through a unique structure without an independent cross-conductor and with the switching circuit acting on the signal port nodes.
[0048] Cascading an amplifier at the signal port of the core switch component according to the present disclosure can provide signal gain in a two-way active mixer, compensate for mixing loss, or meet system requirements. FIG. 2(a) shows a schematic diagram of a two-way active amplifier 100, including its circuit symbol (shown on the left in FIG. 2(a)) and an exemplary circuit implementation (shown on the right in FIG. 2(a)). The two-way active amplifier 100 has a first pair of ports P1a, P1b and a second pair of ports P2a, P2b. The two-way active amplifier 100 is designed to be able to provide signal amplification in both directions, that is, the signal can be amplified from the P1a / P1b ports and output to the P2a / P2b ports, or can be amplified from the P2a / P2b ports and output to the P1a / P1b ports. A possible circuit topology for implementing this two-way amplification function is shown on the right in FIG. 2(a). The right side of FIG. 2(a) shows a circuit implementation based on a cross-coupled differential pair, but the present disclosure is not limited to this specific implementation, and those skilled in the art can adopt other known or newly designed two-way amplifier circuits.
[0049] FIG. 2(b) shows a circuit schematic diagram of a two-way active mixer including a two-way active amplifier according to an embodiment of the present disclosure. The core part of the two-way active mixer is the switch component shown in FIG. 1(c), which mainly includes switch transistors M1 to M4, signal port nodes Node_A, Node_B, Node_C, Node_D, local oscillator ports LO+, LO-, and a switching circuit including switches SW_AV, SW_AG, SW_BG, SW_BV, etc. Its structure and working principle can be referred to the relevant description about FIG. 1(c) above.
[0050] In the exemplary embodiment shown in FIG. 2(b), two-way active amplifiers 100a and 100b are respectively connected to both sides of the core switch component (the specific structure can be referred to FIG. 2(a)).
[0051] For the two-way active amplifier 100a, one side port is connected to an external port of the device, for example, differential ports Port_A1 and Port_A2, which can be used as the radio frequency port or intermediate frequency port of the whole device; the other side port is connected to the first signal port node Node_A and the second signal port node Node_B of the core switch component through a corresponding passive network and the corresponding switching circuit connection points.
[0052] For the two-way active amplifier 100b, one side port is connected to another external port of the device, for example, differential ports Port_B1 and Port_B2, which can be used as the intermediate frequency port or radio frequency port of the whole device; the other side port is connected to the other pair of signal port nodes Node_C and Node_D of the core switch component through a corresponding passive network.
[0053] The functions of the two bidirectional active amplifiers 100a and 100b are to amplify the input or output signals correspondingly when the mixer operates in the receiving mode or the transmitting mode to meet the gain requirements of the system. Since they are bidirectional, they can support the flow and amplification of signals in both directions, matching the bidirectional working characteristics of the core switch component.
[0054] The operating mode (receiving mode or transmitting mode) of the entire device is still determined by the switching circuit (the states of switches SW_AV, SW_AG, SW_BV, and SW_BG) inside the core switch component according to the external control signal. The principle can be referred to the relevant description in Figure 1(c). The amplifiers 100a and 100b cooperate with the bidirectional working mode of the core switch component to amplify the signals.
[0055] Although this specification contains many specific implementation details, these should not be construed as limiting the scope of any invention or the scope of what is claimed, but are mainly used to describe the features of specific embodiments of a particular invention. Certain features described in multiple embodiments in this specification can also be combined and implemented in a single embodiment. On the other hand, the various features described in a single embodiment can also be separately implemented in multiple embodiments or implemented in any suitable sub-combination. In addition, although the features may function in certain combinations as described above and are even initially claimed as such, one or more features from the claimed combination can be removed in some cases, and the claimed combination can be directed to a sub-combination or a variant of the sub-combination.
[0056] The above description is only the preferred embodiment of one or more embodiments of this specification and is not intended to limit one or more embodiments of this specification. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of one or more embodiments of this specification shall be included within the scope protected by one or more embodiments of this specification.
Claims
1. A two-way active mixer, characterized in that, The described two-way active mixer includes: A switching component including a plurality of switching transistors, the control gates of the switching transistors being configured to receive a local oscillator signal; the switching component having at least one signal port node, the signal port node being part of the source node or drain node of the switching transistors within the switching component; A radio frequency port and an intermediate frequency port configured such that a radio frequency signal or an intermediate frequency signal can be coupled to the at least one signal port node, and there is no independent cross-conductor with voltage-current conversion as the main function between the at least one signal port node; A switching circuit connected to the at least one signal port node and configured to selectively connect the at least one signal port node to a power supply terminal or a ground terminal according to a control signal to determine the operating mode of the two-way active mixer and provide a static bias current for the switching transistors in the switching component.
2. The two-way active mixer according to claim 1, wherein: The switching component has a first signal port node and a second signal port node; The radio frequency port is coupled to the first signal port node, and the intermediate frequency port is coupled to the second signal port node; The switching circuit is configured to selectively connect the first signal port node to a power supply terminal or a ground terminal, and selectively connect the second signal port node to a power supply terminal or a ground terminal.
3. The two-way active mixer according to claim 2, characterized in that, The switching component adopts a double-balanced mixer topology.
4. The two-way active mixer according to claim 3, characterized in that, The double-balanced mixer topology includes four of the switching transistors, and the four switching transistors are configured into a transistor quadrilateral array.
5. The two-way active mixer according to claim 4, wherein: The four switching transistors include a first pair of differentially connected transistors and a second pair of differentially connected transistors; The common source / drain node of the first pair of differentially connected transistors constitutes the first signal port node; The common source / drain node of the second pair of differentially connected transistors constitutes the second signal port node.
6. The bidirectional active mixer according to claim 2, wherein The switching circuit includes: A first switching unit controlled by a first control signal for connecting the first signal port node to the power supply terminal or the ground terminal; A second switching unit controlled by a second control signal for connecting the second signal port node to the power supply terminal or the ground terminal.
7. The two-way active mixer according to claim 6, wherein: In the receiving mode, the first switching unit connects the first signal port node to the power supply terminal, and the second switching unit connects the second signal port node to the ground terminal; In the transmitting mode, the first switching unit connects the first signal port node to the ground terminal, and the second switching unit connects the second signal port node to the power supply terminal.
8. The two-way active mixer according to claim 1, characterized in that The static bias current enables the switching transistors to operate in the saturation region when performing switching actions driven by the local oscillator signal.
9. The bidirectional active mixer according to claim 1, wherein The mixer further includes at least one bidirectional active amplifier circuit, and the bidirectional active amplifier circuit is connected in series between the RF port and the at least one signal port node, and / or is connected in series between the intermediate frequency port and the at least one signal port node.