Transmitter mixer circuit and method for reducing local oscillator leakage

Abstract

A transmitter mixer circuit is provided for reducing local oscillator leakage. The transmitter mixer circuit (100) includes a double-balanced transmitter mixer comprising two branches. Furthermore, the first branch of the two branches includes a first calibration current source (I00). P ) and the first calibration capacitor (C P Furthermore, the first calibration capacitor (C) P Grounding, the second branch of the two branches includes a second calibration current source (I) N ) and second calibration capacitor (C N Additionally, the transmit mixer circuit (100) is used to: based on the first calibration capacitor (C) P ) and the second calibration capacitor (C N The capacitor of ) and the first calibration current source (I) P ) and the second calibration current source (I N The output of the transmitter mixer (100) is used to calibrate the double-balanced transmitter mixer (102). The transmitter mixer circuit (100) performs two-dimensional calibration, that is, adjusting the amplitude difference and phase difference between the LO leakage currents to reduce the overall LO leakage.

Description

Technical Field

[0001] This invention generally relates to the field of radio frequency communication systems, and more specifically, to transmit mixer circuits for reducing local oscillator leakage. Furthermore, this invention specifically relates to a method for reducing local leakage in transmit mixer circuits. Background Technology

[0002] In radio frequency (RF) communication systems, transmit mixers are typically used to combine two or more input signals of different frequencies to generate an output signal. Depending on the application, various types of transmit mixers are used in RF communication systems. For example, an IQ mixer can be a type of transmit mixer where complex-modulated baseband data (e.g., in-phase (I) data and quadrature-phase (Q) data) is up-converted to an RF frequency. Additionally, a double-sideband (DSB) mixer can be a type of transmit mixer where the input signal is mixed with the LO signal to generate an output signal with two sidebands, the sum and difference of the frequencies of the input signal and the LO signal. Furthermore, a power amplifier (PA) is connected to a DSB mixer to amplify the output signal. Other types of transmit mixers exist, such as single-sideband mixers and two synchronous single-sideband mixers. A common problem involved in the operation of transmit mixers is LO leakage. In LO leakage, the LO signal leaks through both output signals in addition to being mixed with the input signal. LO leakage may reduce the signal quality of transmitted signals, violate out-of-band transmission requirements, and interfere with other receivers.

[0003] Several attempts have been made to reduce LO leakage in transmit mixers. One such attempt involves using an IQ mixer (instead of other mixer topologies) and calibrating the LO signal by adding two independent offsets to the two baseband (BB) signals. However, a problem associated with this approach is that using an IQ mixer is not always ideal, as generating accurate quadrature LO signals is very difficult and consumes significant power, especially at high frequencies. In another example, a conventional DSB mixer can suppress LO leakage by inserting a bandpass or notch filter between the DSB mixer and the PA. However, a problem associated with this approach is that the filter may not adequately suppress LO leakage because the leakage is near the edge of the upconversion band. Furthermore, bandpass or notch filters can cause performance degradation in terms of gain, area, and power consumption of the two output signals. Other attempts include adding conventional calibration functions to the DSB mixer to reduce LO leakage. However, a problem with this approach is that the calibration function can generate unacceptable residual leakage in some applications due to the lack of quadrature phase in the LO signals. Therefore, a technical challenge exists: how to reduce LO leakage in transmit mixers without affecting output signal performance.

[0004] Therefore, in light of the above discussion, it is necessary to overcome the drawbacks associated with traditional LO leakage suppression techniques. Summary of the Invention

[0005] This invention provides a transmit mixer circuit for reducing local oscillator (LO) leakage and a method for reducing LO leakage. The invention provides a solution to the existing problem of reducing LO leakage in a transmit mixer without affecting output signal performance. An object of the invention is to provide a solution that at least partially overcomes the problems encountered in the prior art, and to provide an improved transmit mixer circuit for reducing LO leakage and an improved method for reducing LO leakage in the transmit mixer circuit.

[0006] One or more objects of the present invention are achieved by means of the technical solutions provided in the appended independent claims. Advantageous embodiments of the invention are further defined in the dependent claims.

[0007] On one hand, the present invention provides a transmit mixer circuit for reducing local oscillator leakage. The transmit mixer circuit includes a double-balanced transmit mixer comprising two branches. Furthermore, a first branch includes a first calibration current source and a first calibration capacitor. The first calibration capacitor is grounded. The second branch includes a second calibration current source and a second calibration capacitor. Furthermore, the transmit mixer circuit is used to calibrate the double-balanced transmit mixer based on the capacitances of the first and second calibration capacitors and the outputs of the first and second calibration current sources.

[0008] The transmitter mixer circuit is equipped with a calibration current source and calibration capacitor to adjust the amplitude and phase difference of the LO leakage current generated by the two branches, thereby eliminating any residual leakage in the double-balanced transmitter mixer without affecting the performance of the output signal. The transmitter mixer circuit improves the quality of the output signal by reducing LO leakage. The proposed LO leakage calibration technique is applicable to reducing LO leakage in various types of transmitter mixers, such as IQ mixers, DSB mixers, and single-sideband mixers.

[0009] In one implementation, the transmit mixer circuit is further configured to provide two-dimensional calibration via the first calibration current source and the second calibration current source, as well as the first calibration capacitor and the second calibration capacitor.

[0010] Two-dimensional calibration of a dual-balanced transmit mixer is beneficial for covering a wider amplitude and phase range of LO leakage current.

[0011] In another implementation, the transmit mixer circuit is further configured to provide the calibration by aligning the phase of the LO leakage from the first branch and the second branch through the first calibration capacitor and the second calibration capacitor.

[0012] In one implementation, the transmit mixer circuit is further configured to: align the phase and amplitude of the LO leakage from the first branch through the first calibration current source and the first calibration capacitor, and align the phase and amplitude of the LO leakage from the second branch through the second calibration current source and the second calibration capacitor, thereby providing the calibration.

[0013] The first and second calibration current sources, along with the first and second calibration capacitors, can adjust the amplitude and phase differences of the LO leakage current, thereby helping to eliminate any residual LO leakage in the double-balanced transmit mixer.

[0014] In one implementation, the transmit mixer circuit is also used to provide the calibration via two direct current (DC) currents.

[0015] These two DC current sources provide calibration LO leakage currents, which adjust the amplitude difference of the LO leakage current and eliminate residual leakage current.

[0016] In another implementation, the first calibration capacitor and the second calibration capacitor are adjustable capacitors.

[0017] Adjustable capacitors are useful for adjusting capacitance to suppress LO leakage current of multiple amplitudes.

[0018] In one implementation, the double-balanced mixer is an active mixer.

[0019] Active mixers are beneficial for improving the conversion gain of double-balanced transmit mixers.

[0020] In one implementation, each branch also includes a current switch and an input stage. Furthermore, the input stage includes a current source.

[0021] In one implementation, a first FET and a second FET are connected in parallel. Furthermore, the drain of the first FET is connected to a first port of the impedance; the drain of the second FET is connected to a second port of the impedance. Additionally, the sources of the first and second FETs are connected to the input stage. The input stage includes a calibration current source and a field-effect transistor (FET), which is connected in parallel between ground and the current switch. Furthermore, a calibration capacitor is connected in parallel with the FET. Additionally, the drains of the first and second FETs of the current switch in the branch are connected to the impedance in a mirror manner.

[0022] Impedance is used to match the impedance of all input and output ports of a double-balanced transmit mixer in order to minimize signal attenuation or loss during operation of the double-balanced transmit mixer.

[0023] In one implementation, the field-effect transistor of the input stage is a metal-oxide-semiconductor field-effect transistor (MOSFET), and the source is grounded.

[0024] MOSFETs are beneficial for reducing power consumption during the operation of a double-balanced emitter mixer.

[0025] In another implementation, the calibration current source is an adjustable current source.

[0026] An adjustable current source is useful for adjusting the current supply to suppress LO leakage current of multiple amplitudes.

[0027] In one implementation, the current switch includes a first FET and a second FET connected in parallel. Furthermore, the drain of the first FET is connected to a first port of the impedance; the drain of the second FET is connected to a second port of the impedance. Additionally, the sources of the first FET and the second FET are connected to the input stage. The input stage also includes a calibration FET as a first calibration current source.

[0028] On the other hand, the present invention provides a method for reducing local oscillator leakage in a transmit mixer circuit. The transmit mixer circuit includes a double-balanced transmit mixer comprising two branches. Furthermore, each branch includes a calibration current source and a calibration capacitor. Additionally, the method includes: calibrating the double-balanced transmit mixer based on the capacitance of the calibration capacitor; and calibrating the double-balanced transmit mixer based on the calibration current source to provide a two-dimensional calibration.

[0029] This method achieves all the advantages and technical effects of the transmitter mixer circuit of the present invention.

[0030] In one implementation, each branch also includes an input voltage converter.

[0031] In another implementation, the input voltage converter includes a FET.

[0032] It should be understood that all the above implementations can be combined. It should be noted that all devices, elements, circuits, units, and modules described in this application can be implemented in software or hardware elements or any combination thereof. All steps performed by the various entities described in this application, and the functions to be performed by the various entities described, are intended to indicate that each entity is suitable for or used to perform the corresponding steps and functions. Although in the following description of specific embodiments, a particular function or step performed by an external entity is not reflected in the detailed description of the specific element of the entity performing that particular step or function, it should be apparent to those skilled in the art that these methods and functions can be implemented in the corresponding software or hardware elements or any combination thereof. It should be understood that the features of the present invention are readily combined in various combinations without departing from the scope of the invention as defined by the appended claims.

[0033] Additional aspects, advantages, features and objects of the invention will become apparent from the accompanying drawings and the detailed description of illustrative implementations as explained in conjunction with the following appended claims. Attached Figure Description

[0034] A better understanding of the above-described invention and the following detailed description of illustrative embodiments can be achieved by reading the accompanying drawings. Exemplary structures of the invention are shown in the drawings to illustrate the invention. However, the invention is not limited to the specific methods and tools disclosed herein. Furthermore, those skilled in the art will understand that the drawings are not drawn to scale. Where possible, similar elements are represented by similar numbers.

[0035] The embodiments of the present invention will now be described with reference to the following figures, which are merely examples, in which: Figure 1 This is a circuit diagram of a transmitter mixer circuit for reducing local oscillator (LO) leakage according to an embodiment of the present invention; Figure 2A , Figure 2B and Figure 2C This is an arrow diagram illustrating the difference and distribution of LO leakage current in a double-balanced transmit mixer according to an embodiment of the present invention; Figure 3A , Figure 3B and Figure 3C This is an arrow diagram depicting the calibration of a double-balanced transmit mixer using a DC source in a transmit mixer circuit, according to an embodiment of the present invention. Figure 4A , Figure 4B and Figure 4C This is an arrow diagram depicting the calibration of a double-balanced transmit mixer using a DC source and a calibration capacitor in a transmit mixer circuit, according to an embodiment of the present invention. Figure 5 This is a circuit diagram depicting a transmitter mixer circuit for reducing local oscillator leakage according to a different embodiment of the present invention; Figure 6 This is a flowchart illustrating a method for reducing local oscillator leakage in a transmit mixer circuit according to an embodiment of the present invention.

[0036] In the accompanying diagram, underlined numbers indicate the item in which the underlined number is located or the item adjacent to the underlined number, while ununderlined numbers are associated with the item identified by the line that links the ununderlined number to the item. When a number is ununderlined and has an associated arrow, the ununderlined number is used to identify the general item that the arrow points to. Detailed Implementation

[0037] The following detailed description illustrates embodiments of the present invention and ways in which these embodiments can be implemented. While some modes of implementing the invention have been disclosed, those skilled in the art will recognize that other embodiments for implementing or practicing the invention may also exist.

[0038] Figure 1 This is a circuit diagram of a transmit mixer circuit for reducing local oscillator leakage according to an embodiment of the present invention. (Reference) Figure 1 The diagram shows a circuit diagram of a transmit mixer circuit 100 for reducing local oscillator (LO) leakage.

[0039] This invention relates to a transmit mixer circuit 100 for reducing LO leakage in an RF transmit mixer. LO leakage refers to the leakage current generated by the local oscillator (LO) during mixing at the input frequency. The transmit mixer circuit 100 is used to reduce LO leakage in a double-balanced transmit mixer. The transmit mixer circuit 100 is used to perform two-dimensional calibration, i.e., adjusting the amplitude and phase differences of the leakage current introduced by the LO to eliminate the overall leakage current.

[0040] The transmit mixer circuit includes a double-balanced transmit mixer. A double-balanced transmit mixer is a type of RF transmit mixer that is configured with multiple diodes or transistors interconnected in a balanced configuration to mix the input intermediate frequency (IF) signal and the local oscillator (LO) signal, thereby providing a radio frequency (RF) output signal. Double-balanced transmit mixers are used to eliminate unwanted signals and provide better performance than single-balanced mixers. According to one embodiment, the double-balanced transmit mixer is an active mixer. In other words, the double-balanced transmit mixer is an active double-balanced transmit mixer. Active double-balanced transmit mixers are configured with active components, such as transistors or amplifiers. Active double-balanced transmit mixers are advantageous for improving conversion gain. LO leakage refers to the leakage current generated when the local oscillator (LO) signal leaks to the output port of the double-balanced transmit mixer. The LO signal leaks to the output port through the power supply or through silicon elements in the double-balanced transmit mixer. Therefore, LO leakage includes LO leakage current, including all types of LO leakage, regardless of the leakage method.

[0041] The double-balanced transmit mixer comprises two branches. Furthermore, the first branch of these two branches includes a first calibration current source I. P and the first calibration capacitor C P In addition, the first calibration capacitor C P Grounding. Furthermore, the second branch of the two branches includes a second calibration current source I. N Second calibration capacitor C N In one implementation, the first calibration current source I... P Second calibration current source I NUsed for calibrating a double-balanced transmit mixer. In one implementation, the first calibration capacitor C P Second calibration capacitor C N Used for calibrating a double-balanced transmit mixer. In one implementation, the transmit mixer circuit 100 includes a positive intermediate frequency (IF) port. P The first calibrated field-effect transistor (FET) connected to the ) P In one example, the first calibration FET (M) P ) is a P-type transconductance (i.e., voltage-to-current conversion) transistor used to transmit current through IF P The port receives the IF frequency signal. In one implementation, the transmit mixer circuit includes a port connected to the negative intermediate frequency (IF) port. N The second calibration field-effect transistor (FET) connected to the connection (M) N In one example, the second FET (M) N ) is an N-type transconductance transistor used to transmit IF N The port receives the IF frequency. In one implementation... Figure 1 The first calibration capacitor C in P Second calibration capacitor C N This can be implemented as a switched capacitor array, programmable via a control signal from a switch. According to one embodiment, the calibration capacitor C... P C N An adjustable capacitor is a type of capacitor whose capacitance can be adjusted or changed. Calibration capacitors are used to align the phase of different LO leaks in a double-balanced transmit mixer to eliminate residual leakage and improve the performance of the double-balanced transmit mixer.

[0042] According to one embodiment, the transmit mixer circuit 100 is also used to provide calibration via two direct current (DC) sources. In one implementation, one of the two DC sources is connected to a first calibration current source I. P and the first calibration capacitor C P The two DC sources are connected in parallel, with the other DC source in parallel configuration with the second calibration current source I. N Second calibration capacitor C N Connection. During the calibration operation, two DC sources provide DC power to generate a calibration LO leakage current, which adjusts the amplitude of the LO leakage current generated by the local oscillator.

[0043] The transmitter mixer circuit 100 is used for: based on the first calibration capacitor C P Second calibration capacitor C NThe capacitor and the first calibration current source I P Second calibration current source I N The output of this is used to calibrate the double-balanced transmit mixer. In other words, the first calibration current source I... P For use individually and with the first calibration capacitor C P Together, calibrate the double-balanced transmit mixer. In one example (e.g.) Figure 1 As shown in the figure, during the calibration of the double-balanced transmit mixer, two LO leakage currents ILO are generated in the first and second branches of the double-balanced transmit mixer, respectively. P and ILO N In addition, the combined LO leakage current ILO P and ILO N This forms the output leakage current ILO. If the LO leakage current ILO P and ILO N If an amplitude difference exists, this difference will cause residual LO leakage in the double-balanced transmit mixer. To avoid residual LO leakage, the transmit mixer circuit 100 activates one of the two DC sources to generate a calibration LO leakage current, which is added to the ILO to adjust the LO leakage current ILO. P and ILO N The amplitude difference. In the LO leakage current ILO P and ILO N When both amplitude and phase differences exist simultaneously, the transmitting mixer circuit 100 will simultaneously operate the first calibration current source I. P and the first calibration capacitor C P (or second calibration current source I) N Second calibration capacitor C N (Through the first calibration current source I) P Second calibration current source I N Adjusting the leakage current ILO P and ILO N The amplitude difference. Furthermore, in order to adjust the leakage current ILO of LO. P and ILO N The phase difference between them, the transmitter mixer circuit 100 tunes the first calibration capacitor C P Second calibration capacitor C N To generate a calibration vector that adjusts the LO leakage current ILO. P and ILO N The phase difference between them.

[0044] According to one embodiment, the transmitter mixer circuit 100 is further configured to: transmit current through the first calibration current source I P Second calibration current source I Nand the first calibration capacitor C P Second calibration capacitor C N Aligning the phase of the local oscillator (LO) leakage from the first and second branches provides calibration. In this embodiment, an LO leakage current ILO is generated on the first branch of the double-balanced transmit mixer. P A leakage current ILO is generated in the second branch of the double-balanced transmit mixer. N In one implementation, the first calibration current source I... P and the first calibration capacitor C P Alignment LO leakage current ILO P The phase. Furthermore, the second calibration current source I... N Second calibration capacitor C N Alignment LO leakage current ILO N The phase. Due to ILO P and ILO N Phase alignment, the transmit mixer circuit 100 eliminates the phase alignment caused by ILO. P and ILO N Any residual LO leakage caused by phase difference.

[0045] According to one embodiment, the transmitter mixer circuit 100 is further configured to: transmit current through the first calibration current source I P and the first calibration capacitor C P Align the phase and amplitude of the LO leakage from the first branch, and pass it through the second calibration current source I. N Second calibration capacitor C N Align the phase and amplitude of the LO leakage from the second branch to provide calibration.

[0046] According to one embodiment, the transmitter mixer circuit 100 is further configured to: transmit current through the first calibration current source I P Second calibration current source I N and the first calibration capacitor C P Second calibration capacitor C N Two-dimensional calibration is provided. This involves calibrating the current source (I0). P and I N ) and calibration capacitor (C P and C N The calibration performed by the transmit mixer circuit 100 is a two-dimensional calibration. Furthermore, the transmit mixer circuit 100 simultaneously adjusts the ILO. P and ILO N The amplitude difference and phase difference. Compared with traditional calibration methods (which involve one-dimensional calibration), two-dimensional calibration is advantageous for covering a wider range of LO leakage current differences.

[0047] According to one embodiment, each branch further includes current switches 106, 108 and input stages 110, 112. In one implementation, current switches 106, 108 include a first current switch 106 and a second current switch 108. In this implementation, input stages 110, 112 include a first input stage 110 and a second input stage 112. Current switches 106, 108 are part of the transmit mixer circuit 100 for receiving a local oscillator (LO) signal for frequency modulation from a local oscillator (LO) circuit. In one implementation, input stages 110, 112 are part of the transmit mixer circuit 100 for calibrating a double-balanced transmit mixer. Reference Figure 1 The diagram shows two LO circuits connected to the current switches 106 and 108 of the double-balanced transmit mixer, for example, LO... P and LO N In one implementation, LO P This is a P-type LO circuit, using a P-type transistor as the active device. Similarly, LO... N This is an N-type LO circuit, using N-type transistors as active devices. Furthermore, during double-balanced emitter mixer operation, input stages 110 and 112 pass through IF... P Ports and IFs N The port receives an intermediate frequency signal. In one implementation, the second branch includes a second current switch 108 and a second input stage 112. In one implementation, the second current switch 108 is operationally equivalent to the first current switch 106, and the second input stage 112 is operationally equivalent to the first input stage 110.

[0048] According to one embodiment, the current switch 106 includes a first field-effect transistor (FET) SW connected in parallel. PP Second FETSW PN First FETSW PP Second FETSW PN These are types of transistors that use an electric field to control the flow of current. Furthermore, the first FETSW... PP Second FETSW PN These include a source terminal, a drain terminal, and a gate terminal. Additionally, the first FETSW... PP Drain and impedance Z L The first port 114 is connected, and the second FETSW is connected. PN Drain and impedance Z L The second port 116 is connected. Additionally, the first FETSW... PP Second FETSW PNThe source is connected to the input stage 110. In one implementation, the impedance Z... L This refers to the combined suppression of the electrical signal flow through a double-balanced transmit mixer using a combination of resistors, capacitors, and / or inductors. In one implementation, the impedance Z... L This is used to provide an output voltage with an RF frequency via the first port 114 and the second port 116. Furthermore, input stages 110 and 112 include a calibration current source I connected to a calibration current source. P I N And a field-effect transistor (FET), which is connected in parallel between ground and current switches 106 and 108. In one implementation, calibration current source I... P I N Including the first calibration current source I P Or the second calibration current source I N Calibrate current source I P I N This refers to the electrical component that provides current during the calibration of a double-balanced transmit mixer. In one implementation, the calibration current source I... P I N Used to generate calibration leakage current to adjust LO leakage within a double-balanced emitter mixer. In one implementation, this FET is a first FET (M P ) or second FET (M N ).

[0049] Additionally, the first FETSW of the current switches 106 and 108 in the branch circuit PP Second FETSW PN The drain is mirrored with impedance Z. L Connection. The current switches 106 and 108 of the branch refer to the first current switch 106 and the second current switch 108. The first current switch 106 of the first branch includes a first FETSW. PP Second FETSW PN Furthermore, the second current switch 108 includes a third FETSW. NN and the fourth FETSW NP Additionally, the third FETSW NN Drain and impedance Z L The first port 114 is connected, and the fourth FETSW PN Drain and impedance Z L The second port 116 is connected. First FETSW PP With impedance Z L The connection between the first port 114 is similar to that between the second FETSW. PNA mirror image of the connection between the second port 118 and the third FETSW. NN With impedance Z L The connection between the first port 114 is similar to that of the fourth FETSW NP With impedance Z L The mirror image of the connection between the second port 118. First FETSW PP , Second FETSW PN , Third FETSW NN and the fourth FETSW NP It is biased to operate in the corresponding nonlinear region and generates a new frequency by mixing the input RF signal. In one implementation, the first FETSW PP , Second FETSW PN , Third FETSW NN and the fourth FETSW NP It is a switching transistor.

[0050] According to one embodiment, the field-effect transistors of input stages 110 and 112 are metal-oxide-semiconductor field-effect transistors (MOSFETs) with their sources grounded. In this embodiment, the transmit mixer circuit 100 uses MOSFETs as active elements during the calibration of the double-balanced transmit mixer. MOSFETs are advantageous for generating low noise during mixing of the input RF signal, improving the linearity of the output signal, and reducing power consumption during the calibration and / or operation of the double-balanced transmit mixer. The drain of the FET is grounded, and the gate of the FET is connected to the IF... P The FET source is connected to current switches 106 and 108 via port connections.

[0051] According to one embodiment, the calibration current source I P I N It is an adjustable current source. In other words, it is controlled by the calibration current source I. P I N The amplitude of the supplied current can vary within a certain range according to the requirements of the calibration current source (LO) leakage current amplitude. Calibration current source I P I N Its adjustable characteristics are beneficial for adjusting LO leakage at multiple amplitudes and extending the calibration range of the transmit mixer circuit 100.

[0052] According to one embodiment, current switches 106, 108 include first FETSW connected in parallel. PP Second FETSW PN In this embodiment, the first current switch 106 includes as follows: Figure 1The first FETSW is shown connected in parallel configuration. PP Second FETSW PN Furthermore, the second current switch 108 includes a third FETSW connected in parallel configuration. NN and the fourth FETSW NP Furthermore, the first FETSW PP Drain and impedance Z L The first port 114 is connected, and the second FETSW is connected. PN The drain of the first FET is connected to the second port 116 with an impedance of 130Ω. Additionally, the first FETSW... PP Second FETSW PN The source of the first FET is connected to the input stages 110 and 112. In other words, the first FETSW... PP Second FETSW PN The source of the third FET is connected to the first input stage 110, while the third FETSW is connected to the first input stage 110. NN and the fourth FETSW NP The source of the first input stage 110 is connected to the second input stage 112. In one implementation, the first input stage 110 includes a first calibration FETM. P The second input stage 112 includes a second calibration FETM. N .

[0053] The transmitter mixer circuit 100 is equipped with a first calibration current source I P Second calibration current source I N and the first calibration capacitor C P Second calibration capacitor C N To adjust the LO leakage current (LO) P and LO N The transmitter mixer circuit 100 eliminates any residual LO leakage (i.e., carrier leakage) in the double-balanced transmit mixer by reducing the amplitude and phase differences of the LO leakage current, without affecting the performance of the output signal. The transmitter mixer circuit 100 helps improve the quality of the output signal by reducing LO leakage and reduces power consumption during the operation of the double-balanced transmit mixer. Furthermore, the transmitter mixer circuit 100 is used to perform two-dimensional calibration of the double-balanced transmit mixer, which helps cover a wide amplitude range of LO leakage current. Additionally, the transmitter mixer circuit 100 is configured with an adjustable inductor and an adjustable capacitor, which facilitates adjustment of LO leakage current at multiple amplitudes. This is achieved by using two calibration current sources I... P I N and the first calibration capacitor C P Second calibration capacitor C NTherefore, compared to conventional calibration methods, the transmit mixer circuit 100 can suppress more LO leakage amplitude. The transmit mixer circuit 100 is also suitable for reducing LO leakage in other types of transmit mixers, such as IQ mixers and DSB mixers.

[0054] Figure 2A , Figure 2B and Figure 2C This is an arrow diagram illustrating the difference and distribution of LO leakage current in a double-balanced transmit mixer according to an embodiment of the present invention. (Reference) Figure 2A , Figure 2B and Figure 2C The arrow diagrams 200A, 200B, and 200C shown depict the differences and distribution of LO leakage current in a double-balanced transmit mixer.

[0055] In one implementation, during the operation of the double-balanced transmit mixer, the local oscillator LO... P and LO N Two LO leakage currents ILO are generated. P and ILO N Due to transistor mismatch within the double-balanced emitter mixer, the LO leakage current ILO exhibits different amplitudes or phases. P and ILO N Each is generated by the first branch (i.e., M) of the double-balanced transmit mixer. P SW PP and SW PN ) and the second branch (M N SW NP and SW NP ) is generated. In one scenario, the leakage current ILO of LO is... N The amplitude is less than the leakage current ILO of LO. P The amplitude, such as Figure 2A As shown. In another scenario, the phase difference between the LO leakage currents is not equal to 180°, as... Figure 2B As shown. Furthermore, Figure 2C This describes the combined LO leakage current ILO (=ILO) generated by transistor mismatch in a double-balanced transmit mixer. P +ILO N A graphical representation of the two-dimensional distribution of ( ). (Reference) Figure 2C The graph shows the horizontal (X-axis) and vertical (Y-axis) axes, with multiple data points distributed along them. The vertical axis represents the real value of the combined LO leakage current (Re(ILO)) and the imaginary value of the combined LO leakage current ILO. Furthermore, Figure 2CEach data point corresponds to the complex combination LO leakage current ILO in the transistor mismatch case of a double-balanced emitter mixer. In this implementation, multiple data points are plotted using a Monte Carlo sampling method.

[0056] Figure 3A , Figure 3B and Figure 3C This is an arrow diagram depicting the calibration of a double-balanced transmit mixer using a DC source in a transmit mixer circuit, according to an embodiment of the present invention. (Reference) Figure 3A , Figure 3B and Figure 3C The arrow diagrams 300A, 300B, and 300C shown depict the calibration of a double-balanced transmit mixer using a DC source in the transmit mixer circuit 100.

[0057] In one implementation, the transmitter mixer circuit 100 uses either of two DC sources (i.e., the first calibration current source I). P Or the second calibration source I N The double-balanced transmit mixer is calibrated. During calibration, calibration source I... N Activated to generate the first calibration LO leakage current ILO cal_In (Due to the up-conversion), such as Figure 3A As shown. Furthermore, ILO cal_In It is added to the combined LO leakage current ILO to eliminate overall LO leakage, such as Figure 3A and Figure 3B As shown. Furthermore, Figure 3C It describes the calibration current source I P I N A graphical representation of the provided calibration range. (Reference) Figure 3C The diagram shows the horizontal axis representing the imaginary value of ILO (Im(ILO)), the vertical axis representing the real value of ILO (Re(ILO)), and multiple data points, where each data point corresponds to the complex value of the combined LO leakage current ILO under transistor mismatch conditions in a double-balanced emitter mixer. Furthermore, Figure 3C Two arrows, 302 and 304, are depicted, representing the current supplied by the first calibration current source I. P The achieved calibration range and the calibration current source I N Achieved calibration range. Calibration current source I P I N The achieved calibration range is one-dimensional, meaning only the ILO is adjusted. P and ILO N The difference in amplitude.

[0058] Figure 4A , Figure 4B and Figure 4CThis is an arrow diagram illustrating the calibration of a double-balanced transmit mixer using a DC source and calibration capacitor in a transmit mixer circuit, according to an embodiment of the present invention. (Reference) Figure 4A , Figure 4B and Figure 4C The arrow diagrams 400A, 400B, and 400C shown depict the calibration of a double-balanced transmit mixer using a DC source and calibration capacitor in the transmit mixer circuit 100.

[0059] In one implementation, the transmitter mixer circuit 100 is used to: simultaneously implement the calibration current source (i.e., the first calibration current source I) P Or the second calibration current source I N ) and calibration capacitor (i.e., the first calibration capacitor C) P Or the second calibration capacitor C N The double-balanced transmit mixer is calibrated. During the calibration of the double-balanced transmit mixer, the calibration current source I is enabled. P I N To generate the first calibration LO leakage current ILO cal_In It is added to the LO leakage current ILO. N In order to balance ILO P and ILO N The amplitude (i.e., ILO) N +ILO cal_In =ILO P ),like Figure 4A As shown. In one example, when the calibration current source I is activated (or tuned) N and calibration capacitor C N At this time, two calibration leakage currents will be generated, for example, ILO. cal_In Second calibration LO leakage current ILO cal_Cn (or calibration vector). Combined Figure 4B Second calibration capacitor C N Generate ILO cal_Cn Second calibration current source I N Generate ILO cal_In They will adjust ILO simultaneously P and ILO N The amplitude difference and phase difference.

[0060] In addition, refer to Figure 4C The diagram shows the horizontal axis representing the imaginary value of ILO (Im(ILO)), the vertical axis representing the real value of ILO (Re(ILO)), and multiple data points, where each data point corresponds to the complex value of the combined LO leakage current ILO under transistor mismatch conditions in a double-balanced emitter mixer. Furthermore, Figure 4C Depicting the simultaneous operation of calibration current source I PI N and the first calibration capacitor C P C N The combined two-dimensional calibration range is achieved. First calibration current source I... P and the first calibration capacitor C P The achieved two-dimensional calibration range is represented by the first region 402. Furthermore, the second calibration current source I... N Second calibration capacitor C P The achieved two-dimensional calibration range is represented by the second region 404. Two-dimensional calibration is achieved by adjusting the LO leakage current ILO. P and ILO N The amplitude and phase differences are used to reduce LO leakage in the double-balanced transmit mixer. By covering all possible transistor mismatches, adding calibration capacitors helps to extend the calibration range to a two-dimensional region (first region 402 and second region 404).

[0061] Figure 5 This is a circuit diagram depicting a transmit mixer circuit for reducing local oscillator leakage according to a different embodiment of the present invention. (Reference) Figure 5 The circuit diagram 500 shown depicts a transmit mixer circuit 100 for reducing local oscillator (LO) leakage. Figure 1 middle).

[0062] The transmitter mixer circuit 100 includes a transformer 502 having a third port 504 and a fourth port 506. Furthermore, the transmitter mixer circuit 100 includes a first transistor 508, a second transistor 510, a third transistor 512, and a fourth transistor 514 connected in a balanced configuration. The drains of the first transistor 508 and the third transistor 512 are connected to the third port 504, and the drains of the second transistor 510 and the fourth transistor 514 are connected to the fourth port 506. Additionally, the sources of the first transistor 508 and the second transistor 510 are connected to the drain of a fifth transistor 516, and the sources of the third transistor 512 and the fourth transistor 514 are connected to the drain of a sixth transistor 518. Furthermore, the sources of the fifth transistor 516 and the sixth transistor 518 are grounded. Additionally, the sources of the first transistor 508 and the second transistor 510 are connected to the drain terminal of a seventh transistor 520 and a first capacitor 526, as shown below. Figure 5 As shown. The seventh transistor 520 can be represented as M. IP The first capacitor 526 can be represented as C P Furthermore, the sources of the third transistor 512 and the fourth transistor 514 are connected to the eighth transistor 522 and the second capacitor 528. The eighth transistor 522 can be represented as M. IN The second capacitor 528 can be represented as C NThe sources of the seventh transistor 520 and the eighth transistor 522 are grounded. Furthermore, the gate terminals of the seventh transistor 520 and the eighth transistor 522 are connected to the current source 524 via two shunt switches, as shown below. Figure 5 As shown. Reference Figure 5 The diagram also shows a detailed view 530 of a current source 524. The current source 524 includes a plurality of transistors connected in parallel, each transistor's drain connected to a switch. (Reference) Figure 5 The diagram also shows a detailed view 532 of the first capacitor 526. The first capacitor 526 comprises a plurality of capacitors connected in parallel, each of which is connected to a switch, the corresponding switch being grounded.

[0063] In one implementation, the seventh transistor 520, the eighth transistor 522, and the current source 524 can be collectively referred to as the calibration current source 534. In another implementation, the first capacitor 526 and the second capacitor 528 can be collectively referred to as the calibration capacitor 536. The calibration current source 534 and the calibration capacitor 536 are used to generate a calibration LO leakage current to suppress residual LO leakage in the double-balanced emitter mixer. In one implementation, the first transistor 508, the second transistor 510, the third transistor 512, and the fourth transistor 514 are operationally equivalent to the first FET 124, the second FET 126, the third FET 134, and the fourth FET 136, respectively (e.g., ...). Figure 1 (As shown). In another implementation, the fifth transistor 516 and the sixth transistor 518 are operationally equivalent to the first calibration FET 108A and the second calibration FET 108B (as shown). Figure 1 (As shown).

[0064] In one implementation, the seventh transistor 520 and the eighth transistor 522 are connected in parallel with the fifth transistor 516, as shown below. Figure 5 As shown. In this implementation, the seventh transistor 520 achieves an adjustable gate voltage (V... tune Together with the fifth transistor 516, it serves as a calibration current source. In one implementation, the gate voltage of the seventh transistor 520 or the eighth transistor 522 is configured at V via a plurality of shunt switches connected in series. tune When the gate of the seventh transistor 520 or the eighth transistor 522 is grounded (with the shunt switch on and / or the series switch off), the fifth transistor 516 is turned off and no calibration current is injected into the emitter mixer circuit 100. When the gate of the seventh transistor 520 or the eighth transistor 522 is grounded, the fifth transistor 516 is turned off and no calibration current is injected into the emitter mixer circuit 100. tune During connection (with the shunt switch open and / or the series switch on), a calibration current is injected into the transmitter mixer circuit 100, and the calibration current is supplied by V. tuneControl. In one implementation, V tune The calibration process involves generating and controlling a programmable current flowing through an NMOS transistor connected to a diode. This programmable current is generated by a switch-controlled array of PMOS current sources.

[0065] Figure 6 This is a flowchart illustrating a method for reducing local oscillator leakage in a transmit mixer circuit according to an embodiment of the present invention. (Reference) Figure 6 The flowchart shown depicts a method 600 for reducing local oscillator leakage in a transmit mixer circuit 100. The method 600 includes steps 602 and 604.

[0066] The transmit mixer circuit 100 includes a double-balanced transmit mixer. Furthermore, the double-balanced transmit mixer includes two branches (e.g., a first branch and a second branch). Additionally, each branch includes a first calibration current source I. P I N and calibration capacitor C P C N .

[0067] At step 602, method 600 includes calibrating capacitor C. P C N The capacitor C is used to calibrate the double-balanced transmit mixer. In other words, during the calibration of the double-balanced transmit mixer, the calibration capacitor C is run or tuned. P C N To generate calibration LO leakage current (ILO) cal_Cn or ILO cal_Cp ), thereby adjusting the leakage current ILO of LO. P and ILO N The phase difference between them (if any). In one implementation, the first calibration current source I P For the first calibration current source I P First calibration current source I N For the second calibration current source I N .

[0068] According to one embodiment, each branch further includes an input voltage converter. An input voltage converter is an electrical component used to convert an input voltage into current. According to one embodiment, the input voltage converter includes a FETM. P M N In one implementation, FETM P M N Used to turn the current supply from the source to the drain on or off. In one example, during the operation of a double-balanced transmit mixer, the IF connected to the input voltage converter... PThe port is used to receive intermediate frequency (IF) signals. If the amplitude of the IF signal is greater than a threshold, then FETM... P M N The switch is activated, allowing current to flow from the source to the drain in order to perform the mixing of the intermediate frequency signal and the LO signal.

[0069] At step 604, method 600 includes calibrating current source I. P I N The double-balanced transmit mixer is calibrated to provide a two-dimensional calibration. Two-dimensional calibration refers to a calibration method that involves simultaneously adjusting the amplitude and phase differences of the LO leakage current. During the calibration of the double-balanced transmit mixer, the calibration current source I is run. P I N To generate calibration LO leakage current (ILO) cal_In or ILO cal_Ip ), thereby adjusting the LO leakage current (ILO) P and ILO N The amplitude difference between (if any) and (if any). According to one embodiment, the calibration current source is a calibration FET. The calibration FET is useful for adjusting the corresponding bias voltage to achieve specific gain and linearity performance, while reducing LO leakage current.

[0070] Method 600 includes a transmitter mixer circuit 100 configured with a first calibration current source and a calibration capacitor to adjust the amplitude and phase differences of the LO leakage current, thereby eliminating any residual leakage in the double-balanced transmitter mixer without affecting the performance of the output signal. Method 600 is advantageous in improving the quality of the output signal by reducing LO leakage and reducing power consumption during operation of the double-balanced transmitter mixer. Furthermore, Method 600 is used to perform two-dimensional calibration on the double-balanced transmitter mixer, which is advantageous in covering a wider amplitude range of the LO leakage current.

[0071] Steps 602 and 604 are merely illustrative, and other alternatives may be provided, in which one or more steps are added, one or more steps are deleted, or one or more steps are provided in a different order, without departing from the scope of the claims herein. Here, the order of steps 602 and 604 may be reversed without departing from the scope of the claims of method 600.

[0072] Modifications to the embodiments of the invention described above may be made without departing from the scope of the invention as defined in the appended claims. Expressions such as “comprising,” “integrating,” “having,” “is,” etc., used to describe and claim the invention are intended to be interpreted in a non-exclusive manner, including items, components, or elements not explicitly described. Singular references should also be interpreted as relating to the plural. The term “exemplary” as used herein means “as an example, instance, or illustration.” Any embodiment described as “exemplary” is not necessarily to be construed as being more preferred or advantageous than other embodiments, or excluding combinations of features from other embodiments. The term “optionally” as used herein means “provided in some embodiments and not in others.” It should be understood that certain features of the invention described in the context of a single embodiment for clarity may also be provided in combination in a single embodiment. Conversely, various features of the invention described in the context of a single embodiment for brevity may also be provided individually or in any suitable combination or as embodiments of any other described aspect of the invention.

Claims

1. A transmitter mixer circuit (100) for reducing local oscillator leakage, characterized in that, The transmit mixer circuit (100) includes a double-balanced transmit mixer, which comprises two branches, wherein... The first of the two branches includes a first calibration current source (I P ) and the first calibration capacitor (C P ), wherein the first calibration capacitor (C) P Grounding; the second branch of the two branches includes a second calibration current source (I N ) and second calibration capacitor (C N ); The transmit mixer circuit (100) is used to: based on the first calibration capacitor (C P ) and the second calibration capacitor (C N The capacitor of ) and the first calibration current source (I) P ) and the second calibration current source (I N The output of the signal is used to calibrate the double-balanced transmit mixer.

2. The transmitter mixer circuit (100) according to claim 1, characterized in that, The transmit mixer circuit (100) is also used to: transmit current through the first calibration current source (I P ) and the second calibration current source (I N ) and the first calibration capacitor (C P ) and the second calibration capacitor (C N It provides two-dimensional calibration.

3. The transmitter mixer circuit (100) according to any one of the preceding claims, characterized in that, The transmit mixer circuit (100) is also used to: transmit current through the first calibration current source (I P ) and the second calibration current source (I N ) and the first calibration capacitor (C P ) and the second calibration capacitor (C N The calibration is provided by aligning the phase leakage of the local oscillator (LO) from the first branch and the second branch.

4. The transmitter mixer circuit (100) according to claim 3, characterized in that, The transmit mixer circuit (100) is also used to: transmit current through the first calibration current source (I P ) and the first calibration capacitor (C P Align the phase and amplitude of the LO leakage from the first branch, and pass it through the second calibration current source (I N ) and the second calibration capacitor (C N Align the phase and amplitude of the LO leakage from the second branch to provide the calibration.

5. The transmitter mixer circuit (100) according to any one of the preceding claims, characterized in that, The transmit mixer circuit (100) is also used to provide the calibration via two direct current (DC) currents.

6. The transmitter mixer circuit (100) according to any one of the claims, characterized in that, The first calibration capacitor (C) P ) and the second calibration capacitor (C N () is an adjustable capacitor.

7. The transmitter mixer circuit (100) according to any one of the preceding claims, characterized in that, The double-balanced mixer is an active mixer.

8. The transmitter mixer circuit (100) according to any one of the preceding claims, characterized in that, Each branch also includes a current switch (106, 108) and an input stage (110, 112), wherein the input stage includes a current source.

9. The transmitter mixer circuit (100) according to claim 8, characterized in that, The current switches (106, 108) include: The first FET (SW) connected in parallel PP ) and the second FET (SW) PN ),in, The first FET (SW) PP The drain and impedance (Z) of the ) L The first port (114) is connected; The second FET (SW) PN The drain and the impedance (Z) L The second port (116) of the first FET (SW) is connected; PP ) and the second FET (SW) PN The source of the circuit is connected to the input stage (110, 112), wherein, The input stages (110, 112) include: Calibration current source (I) P I N ); A field-effect transistor (FET) is connected in parallel between ground and the current switches (106, 108), wherein the calibration capacitor (C) P C N ) connected in parallel to the FET; The first FET (SW) of the current switches (106 and 108) of the branch PP ) and the second FET (SW) PN The drain of the impedance (Z) is mirrored with the impedance (Z) in a mirror manner. L )connect.

10. The transmitter mixer circuit (100) according to claim 9, characterized in that, The field-effect transistors of the input stages (110, 112) are metal-oxide-semiconductor field-effect transistors (MOSFETs), and their drains are grounded.

11. The transmitter mixer circuit (100) according to claim 9 or 10, characterized in that, The calibration current source (I) P I N () is an adjustable current source.

12. A method (500) for reducing local oscillator (LO) leakage in a transmitter mixer circuit (100), characterized in that, The transmit mixer circuit includes a double-balanced transmit mixer, which comprises two branches, each branch including a calibration current source (I0). P I N ) and calibration capacitor (C P C N The method (500) includes: Based on the calibration capacitor (C) P C N The capacitor is used to calibrate the double-balanced transmit mixer. Based on the calibration current source (I) P I N The dual-balanced transmit mixer is calibrated to provide two-dimensional calibration.

13. The method according to claim 12, characterized in that, Each branch also includes an input voltage converter.

14. The method according to claim 13, characterized in that, The input voltage converter includes a FET (M P M N ).

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