System and method for detecting local oscillator leakage and image tones

Abstract

A detector circuit includes a squaring circuit configured to receive an output of a power amplifier of a radio transmitter and produce an output current, the output of the power amplifier including a desired tone, a local oscillator leakage tone, and an image tone, and the output current of the squaring circuit including a direct current (DC) component including a function of the desired tone and an alternating current (AC) component; and a DC current sink electrically connected to an output of the squaring circuit, the DC current sink configured to filter out the DC component of the output current of the squaring circuit to produce a filtered output of the squaring circuit, the filtered output including the AC component, the AC component including a function of the local oscillator leakage tone and a function of the image tone.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to U.S. Provisional Patent Application No. 62 / 944,927, filed December 6, 2019, with the United States Patent and Trademark Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] Various aspects of embodiments of this disclosure relate to radio frequency (RF) circuits, and more specifically, to systems and methods for detecting local oscillator leakage and image tone in an I / Q mixer-based transceiver. Background Technology

[0004] A mixer is a circuit that generates a new signal from two signals applied to it. For example, two mixers (an in-phase (I) mixer and a quadrature (Q) mixer) that receive the frequency of a phase-locked local oscillator (LO) – the in-phase (I) frequency and the quadrature (Q) frequency, respectively, separated by 90 degrees, can be used to convert an input baseband signal (e.g., a low-frequency signal) into a radio frequency (RF) signal (e.g., a high-frequency signal). Generally, a mixer can be thought of as multiplying two input signals.

[0005] In radio frequency (RF) transceivers, mixers are typically used in conjunction with a local oscillator (LO) to convert signals between the baseband frequency and the RF frequency in which the transceiver operates. For example, on the transmitting side of an RF transceiver, an analog baseband signal (e.g., in the range of 0 Hz to 20 MHz or greater) can be mixed with an LO (e.g., a transmitter LO) to frequency the signal to the radio's transmit frequency (e.g., 410 MHz to 7125 MHz and / or 24.25 GHz to 52.6 GHz in the case of 5G new radios). Similarly, on the receiving side of an RF transceiver, the received analog signal in the RF frequency is mixed with an LO (e.g., a receiver LO) to recover the baseband signal. Summary of the Invention

[0006] Various aspects of embodiments of this disclosure relate to systems and methods for detecting local oscillator leakage and image tone in an I / Q mixer-based transceiver.

[0007] According to one embodiment of this disclosure, a detector circuit includes: a squaring circuit configured to receive the output of a power amplifier of a radio transmitter and configured to generate an output current, the output of the power amplifier including: a desired tone; a local oscillator leakage tone; and an image tone, and the output current of the squaring circuit including: a direct current (DC) component and an alternating current (AC) component comprising a function of the desired tone, the AC component comprising a function of the local oscillator leakage tone and a function of the image tone; and a DC current absorber electrically connected to the output of the squaring circuit, the DC current absorber being configured to filter out the DC component of the output current of the squaring circuit to generate a filtered output of the squaring circuit, the filtered output comprising a function of the local oscillator leakage tone and a function of the image tone.

[0008] The filtered output can be provided to the transimpedance amplifier.

[0009] A radio transmitter may include a transmit mixer configured to mix the output of a transmitter local oscillator with an input baseband signal to produce a transmit mixer output, which is provided as an input to a power amplifier. A squaring circuit may be configured to generate an output current at an output terminal of a radio receiver connected via a detector switch. The radio receiver may include a transimpedance amplifier and a receive mixer configured to mix a received signal with a receiver local oscillator, the output of which is connected to the transimpedance amplifier via a receiver switch.

[0010] A radio transceiver includes a radio transmitter and a radio receiver, and the radio receiver includes a transimpedance amplifier; and the detector circuitry may be included in an integrated circuit.

[0011] The detector circuit may further include: a receiver switch connected between the receiver mixer of the radio receiver and the transimpedance amplifier, the receiver switch being configured to disconnect the radio receiver during calibration of the radio transceiver using the detector circuit; and a detector switch connected between the output of the square circuit and the transimpedance amplifier, the detector switch being configured to connect the output of the square circuit of the detector circuit to the transimpedance amplifier during calibration of the radio transceiver.

[0012] The radio transmitter may also include a transmit mixer configured to mix the output of the transmitter's local oscillator with an input baseband signal to produce a mixer output, which is provided to a power amplifier.

[0013] The local oscillator leakage tone can correspond to the output of the transmitter's local oscillator.

[0014] The signal path of the transmitting mixer can include an in-phase portion and a quadrature portion, and the picture tone can correspond to the imbalance between the in-phase and quadrature portions of the signal path.

[0015] The square circuit may include: a first transistor; and a second transistor having substantially the same transistor characteristics as the first transistor, the first transistor and the second transistor being connected in parallel between the output terminal of the square circuit and ground, the output current of the square circuit being corresponding to the sum of a first current flowing through the first transistor and a second current flowing through the second transistor according to the output of the power amplifier, wherein the output of the power amplifier can be differentially provided to the first gate of the first transistor and the second gate of the second transistor.

[0016] DC current sinks may include voltage followers based on low-dropout regulators.

[0017] A DC current sink may include: an operational amplifier, the non-inverting input of which is connected to the output of a square circuit, and the inverting input of which is connected to a reference voltage source; a transistor connected between the power supply and the output of the square circuit, with the gate of the transistor connected to the output of the operational amplifier; and a capacitor connected between the power supply and the gate of the transistor.

[0018] The output impedance of a DC current sink can be frequency-dependent, exhibiting low output impedance at frequencies below the desired cutoff frequency and high output impedance at other frequencies.

[0019] According to one embodiment, a method for detecting local oscillator leakage and image tone includes: providing the output of a power amplifier of a radio transmitter of a radio transceiver to a square circuit of a detector circuit to generate an output current, the output of the power amplifier including: a desired tone, a local oscillator leakage tone, and an image tone; the output current of the square circuit including: a direct current (DC) component and an alternating current (AC) component, both functions of the desired tone, the AC component including: a function of the local oscillator leakage tone and a function of the image tone; absorbing the DC component of the output current by a DC current absorber of the detector circuit to generate a filtered output of the square circuit, wherein the filtered output includes a function of the local oscillator leakage tone and a function of the image tone; and detecting the local oscillator leakage tone and the image tone based on the filtered output.

[0020] The method may also include providing the filtered output to a transimpedance amplifier.

[0021] A transimpedance amplifier can be included in the radio receiver of a radio transceiver.

[0022] The radio receiver may further include a receive mixer configured to mix the received signal with a receiver local oscillator, the output of which is connected to a transimpedance amplifier via a receiver switch. The detector circuit may include an output configured to provide a filtered output to the transimpedance amplifier via a detector switch. The method may further include: connecting the output of the detector circuit to the transimpedance amplifier via a detector switch when detecting local oscillator leakage and image tone of the radio transceiver; and disconnecting the receive mixer from the transimpedance amplifier via a receiver switch.

[0023] The method may further include: mixing an input baseband signal with the output of a transmitter local oscillator of the radio transceiver by a transmitter mixer to produce a mixer output; and amplifying the mixer output by a power amplifier of the radio transmitter to produce a power amplifier output.

[0024] The local oscillator leakage tone can correspond to the output of the transmitter's local oscillator.

[0025] The signal path of the transmitting mixer can include an in-phase portion and a quadrature portion, and the picture tone can correspond to the imbalance between the in-phase and quadrature portions of the signal path.

[0026] The square circuit may include: a first transistor and a second transistor having substantially the same transistor characteristics as the first transistor, the first transistor and the second transistor being connected in parallel between the output terminal of the square circuit and ground, wherein the output current of the square circuit may correspond to the sum of a first current flowing through the first transistor and a second current flowing through the second transistor according to the output of the power amplifier, wherein the output of the power amplifier may be differentially provided to the first gate of the first transistor and the second gate of the second transistor. Attached Figure Description

[0027] The accompanying drawings, together with the specification, illustrate exemplary embodiments of the present disclosure and, together with the specification, serve to explain the principles of the present disclosure.

[0028] Figure 1 This is a block diagram of a transceiver including a detector according to an embodiment of the present disclosure.

[0029] Figure 2A It is a schematic diagram depicting the local oscillator (LO) leakage and image tone that appear in the power spectrum or amplitude spectrum of the output of a power amplifier.

[0030] Figure 2B This is a schematic diagram illustrating the power spectrum or amplitude spectrum of the detected LO leakage function or signature and the detected image pitch function or signature according to an embodiment of the present disclosure.

[0031] Figure 3 This is a schematic block diagram of a detector according to an embodiment of the present disclosure.

[0032] Figure 4 This is a schematic diagram illustrating the frequency-dependent output impedance of a voltage follower of a detector according to an embodiment of the present disclosure.

[0033] Figure 5 This is a circuit diagram illustrating a square circuit according to an embodiment of the present disclosure.

[0034] Figure 6 This is a circuit diagram showing a DC current sink according to an embodiment of the present disclosure. Detailed Implementation

[0035] In the following detailed description, only certain exemplary embodiments of the present disclosure are shown and described by way of illustration. As those skilled in the art will recognize, embodiments of the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Throughout the specification, similar reference numerals denote similar elements.

[0036] Radio frequency (RF) transceivers are widely used in electronic communications and can be found in a variety of consumer devices, such as smartphones (e.g., for communicating with cell towers), laptops (e.g., for communicating with wireless LAN base stations), and personal accessories (e.g., for connecting to Bluetooth hosts). Therefore, there is a need for high-performance and efficient RF transceivers for both consumer and enterprise electronic wireless communications.

[0037] Figure 1 This is a block diagram of a transceiver including a detector according to one embodiment of the present disclosure. Reference Figure 1The radio frequency (RF) transceiver (or radio transceiver) 1 may include a radio transmitter (or transmitter or transmitting side) 10 configured to modulate a baseband signal for transmission. For example, the transmitting side may receive a digital representation of the input baseband waveform at a digital-to-analog converter (DAC) 12, where, for example in the case of a smartphone, the baseband waveform may be encoded for digital voice data, network data (e.g., internet traffic), etc. In some embodiments, the digital representation of the waveform may be, for example, the output of a software-defined radio (SDR) or other digital signal processing hardware (referred to herein as a “modem”). The DAC 12 converts the digital data into a corresponding analog baseband signal, and then provides the corresponding analog baseband signal to a low-pass filter 14 (e.g., to suppress harmonics generated by the DAC 12) before providing it to the transmit mixer 16. The transmit mixer 16 mixes the provided baseband signal with a first local oscillator frequency f. LO1 The output of the transmitter local oscillator (LO) 17 is mixed to divert the signal from the baseband frequency f. BB (For example, in the range of 0Hz to 200MHz or higher) converted to radio frequency f RF Transmission is performed, wherein the specific frequency may depend on the frequency band specified by the protocol (e.g., 410MHz to 7.125GHz and / or 24.25GHz to 52.6GHz in the case of 5G new radios) and is tuned by the transceiver (e.g., by selecting a specific operating channel). The output of the transmit mixer 16 (mixer output) is then provided to one or more amplification stages (in... Figure 1 It is described as a power amplifier (PA) 18, and provides the amplified signal to one or more antennas for transmission.

[0038] Figure 1 The RF transceiver 1 shown also includes a receiving side (or receiver or radio receiver) 20 configured to demodulate the received signal into a baseband signal for further processing. The radio receiver 20 of the RF transceiver 1 can receive radio frequency signals (e.g., from an antenna) and can provide the received signals to a low-noise amplifier (LNA) 22. The amplified signal is then provided to a receive mixer 24, which mixes the received amplified signal with a second local oscillator frequency f. LO2 The receiver local oscillator (LO) 23 output is mixed to transfer the signal from radio frequency f RF Reduced to baseband frequency f BBThe receiver local oscillator 23 can be the same local oscillator 17 used with the transmitter mixer 16 (e.g., in the case of time division multiplexing), or it can be a different local oscillator (e.g., allowing transceiver 1 to transmit and receive simultaneously at different frequencies using frequency division multiplexing). The baseband frequency signal can then be provided to a transimpedance amplifier (TIA) 26, which amplifies the baseband frequency signal and outputs the amplified signal to a low-pass filter (LPF) 27 (e.g., a dual quadratic or dual second-order filter). The filtered signal is then provided to an analog-to-digital converter (ADC) 28, which converts the analog signal into its digital representation for further processing (e.g., via a modem, as described above).

[0039] The receiver may also include a receiver switch 25 to disconnect the radio receiver 20. For example, as Figure 1 As shown, receiver switch 25 is located between the output of receiver mixer 24 and the input of transimpedance amplifier 26. (However, embodiments of this disclosure are not limited thereto.) Typically, receiver switch 25 can be used to disconnect the radio receiver 20 of the transceiver when calibration is performed by detector circuit (Det) 100, as described in more detail below.

[0040] Figure 2A This is a schematic diagram illustrating local oscillator (LO) leakage and image tone appearing in the power spectrum or amplitude spectrum of a power amplifier output. More specifically, Figure 2A This is a schematic diagram depicting the power spectrum or amplitude spectrum of the output signal 2 of the power amplifier 18. As noted in the background art, two in-phase / quadrature (I / Q) mixers, each receiving a phase-locked local oscillator (LO) frequency and separated by 90 degrees, convert radio frequency (RF) to in-phase (I) and quadrature (Q) frequencies, respectively. For example, each of the transmit mixer 16 and the receive mixer 24 may include an in-phase (I) signal path and a quadrature (Q) signal path. I / Q imbalance or I / Q mismatch may occur due to phase mismatch between the in-phase and quadrature portions of the signal paths (e.g., when the two signal paths are not exactly 90 degrees apart). For convenience, in the following discussion, the first local oscillator frequency f, generated by the transmitter local oscillator 17 and mixed with the baseband signal by the transmit mixer 16, will be referred to as... LO1 This can be called the local oscillator frequency f. LO The second local oscillator frequency f, generated by the receiver local oscillator 23 and mixed by the receiver mixer 24 with the received amplified signal, is... LO2 In this paper, it will always be referred to as the second local oscillator frequency f. LO2 .

[0041] like Figure 2AAs shown, the output of the power amplifier can include effective signals at three different frequencies. One signal is a radio frequency (RF) f RF Expected pitch A at the location RF This corresponds to the desired output of radio transmitter 10. According to standard mixer operation, the desired tone is at a frequency equal to the local oscillator frequency f. LO (exist Figure 2A In the embodiment shown, the first local oscillator frequency f LO1 and baseband frequency f BB The sum of (f) RF =f LO +f BB ) radio frequency f RF However, I / Q mismatch may cause the power amplifier output to also include frequencies at the image tone frequency f. IM (where f) IM =f LO -f BB Image pitch A at ) IM Furthermore, local oscillator (LO) leakage may also cause the signal output by the transmitter's local oscillator 17 to become the local oscillator frequency f. LO (First local oscillator frequency f) LO1 A at ) LO It appears in the output. Therefore, the expected pitch is A. RF Compared to the local oscillator frequency f LO high f BB And similarly, image tone A IM Compared to the local oscillator frequency f LO low f BB This makes the image tone A IM And the expected pitch A RF Separate 2f in frequency BB The I / Q mismatch can vary at different frequencies (e.g., different baseband frequencies and different local oscillator frequencies). As a concrete example, at a baseband frequency f... BB It can be 200MHz, the local oscillator frequency f LO It can be 10GHz, therefore the desired RF f-frequency of the tone RF It could be 10GHz + 200MHz = 10.2GHz, and the image tone frequency f IM It could be 10GHz - 200MHz = 9.8GHz.

[0042] Therefore, various aspects of the embodiments of this disclosure relate to the detection of a local oscillator leakage signal A. LO (For example, the first local oscillator frequency corresponding to the frequency of the input baseband signal to be transmitted, which is mixed by the transmit mixer 16) and the image tone A IMSystems and methods for calibrating transceiver 1 to reduce or eliminate local oscillator leakage. LO And the image tone A caused by I / Q imbalance across the entire operating frequency range. IM Embodiments of this disclosure can be used with a variety of different types of radio transceivers operating in various modes, including radio transceivers implementing Time Division Duplex (TDD) and / or Frequency Division Duplex (FDD) operating modes. Detection of local oscillator leakage signal and image tone can be performed as part of a calibration process, wherein calibration can be factory calibration, real-time calibration, background calibration, and / or foreground calibration.

[0043] refer to Figure 1 According to some embodiments of this disclosure, detector circuit 100 is electrically connected between the output of power amplifier 18 of radio transmitter 10 and the input of transimpedance amplifier 26 of radio receiver 20 to provide feedback circuitry that provides information to a modem to calibrate, for example, the in-phase and quadrature portions of a mixer. Detector switch 29 may further connect the output of detector circuit 100 to transimpedance amplifier 26 so that detector circuit 100 is only connected to transimpedance amplifier 26 during calibration measurements (e.g., when receiver switch 25 is open and transceiver 1 does not receive a signal captured from the antenna). Although the comparison system includes on-chip calibration capabilities, embodiments of this disclosure provide efficient detection circuitry with low power and small area, at least in part because portions of radio receiver 20 are reused to provide feedback information via detector circuit 100 and because detector circuitry 100 according to embodiments of this disclosure is relatively simple and has relatively few and relatively small components. According to some embodiments of this disclosure, the same (or a single) integrated circuit (IC) includes detector circuitry 100 and one or more components of transceiver 1’s radio transmitter 10 and radio receiver 20 (e.g., a mixer signal integrated circuit or an analog radio frequency integrated circuit, wherein DAC 12 and ADC 28 may be included in or excluded from the integrated circuit).

[0044] Figure 2B This is a schematic depiction of the power spectrum or amplitude spectrum of the detected LO leakage function or key signature and the detected image tone function or key signature according to an embodiment of the present disclosure. Figure 2B As shown, the detector circuit 100 can be configured to assist in generating a detector signal 3, which includes a first frequency f. BB The function or tone signature of the local oscillator leakage at the location (e.g., leakage of the transmitter local oscillator 17) and the second frequency 2f BBThe generated detector signal 3 is a function of the image tone or key signature. It can then be provided to a modem so that the modem can tune the transceiver 1 to reduce or eliminate I / Q imbalance. The system and method used by the detector circuit 100 according to embodiments of this disclosure for generating the detector signal 3 are described in more detail below.

[0045] Figure 3 This is a schematic block diagram of a detector according to an embodiment of the present disclosure. Figure 3 In the illustrated embodiment, the detector circuit 100 includes a squarer or square circuit (X). 2 )110 and voltage follower or DC current sink 150. (For convenience and clarity, in Figure 3 Detector switch 29 is omitted, but it could be located separately between node N of transimpedance amplifier 26 and square circuit 110 and DC current sink 150. Square circuit 110 receives output signal 2 from power amplifier 18 as input (e.g., as shown in the image). Figure 1 As shown, the current output of the squaring circuit 110 is represented herein as I, which is the input to the detector circuit 100 and outputs a current signal corresponding to the square of the input signal (e.g., the input signal multiplied by itself). DC +I AC .

[0046] like Figure 3 As shown, the detector's input signal 2 includes a signal with amplitude A. RF radio frequency f RF The expected pitch at the location, with amplitude A LO The local oscillator frequency f LO (or the first local oscillator frequency f) LO1 The local oscillator tone at ) and the amplitude A IM Image frequency f IM The image pitch at that location can be considered as the sum of three pitches:

[0047] A RF f RF +A LO f LO +A IM f IM .

[0048] When the squaring circuit 110 performs a squaring operation on the input signal 2, it generates an output current I. DC +I AC Its magnitude corresponds to the square of the input:

[0049] (A RF f RF +A LOf LO +A IM f IM ) 2 .

[0050] The square signal expression can be expanded as follows (after the extracted factor 2):

[0051]

[0052] A RF A LO (f RF -f LO )+A LO A IM (f LO -f IM )+A RF A IM (f RF -f IM )

[0053] According to mixer mathematics, when a signal is multiplied by itself, the product includes a component with a frequency of zero (e.g., becoming a DC component) and a component with a frequency twice that of the input signal.

[0054] Therefore, the first item It can be rewritten as:

[0055]

[0056] Therefore, as Figure 3 As shown, the power of the desired pitch is a function of the key signature s(A). RF The DC component appears at output 4 of the square circuit 110. (The component at twice the signal frequency is outside the operating frequency band of the circuit, and those skilled in the art will understand that the component at twice the signal frequency can be ignored.)

[0057] As mentioned above, the frequency f of the desired pitch RF Compared to the local oscillator frequency f LO high f BB Therefore f RF =f LO +f BB Similarly, the frequency f of the image pitch IM Compared to the local oscillator frequency f LO low f BB Therefore f IM =f LO -f BB Therefore, the second term A RF A LO (f RF -f LO )+ALO A IM (f LO -f IM This can be rewritten as:

[0058] A RF A LO (f LO +f BB -f LO )+A LO A IM (f LO -f LO +f BB )

[0059] It equals:

[0060] A RF A LO f BB +A LO A IM f BB

[0061] It can be simplified to:

[0062] (A RF A LO +A LO A IM )f BB

[0063] Therefore, as Figure 3 As shown, the function or key signature s(A) for local oscillator leakage (or transmitter local oscillator leakage) LO At the output 4 of the square circuit 110, the baseband frequency f is used as the baseband frequency. BB The amplitude s(A) is at the point. LO ) = A RF A LO +A LO A IM The signal appeared.

[0064] The third term A in the above expression for the output of the square circuit 110 RF A IM (f RF -f IM It can also be simplified in the way described above:

[0065] A RF A IM (f LO +f BB -(f LO -f BB ))=A RF A IM (f LO +fBB -f LO +f BB )

[0066] =A RF A IM 2f BB

[0067] Therefore, the function of the image pitch or key signature s(A) IM As at frequency 2f BB The amplitude s(A) is at the point. IM ) = A RF A IM The signal appears at output 4 of the square circuit 110.

[0068] Therefore, the output of the square circuit 110 is 4I. DC +I AC Having DC, f BB and 2f BB The power spectrum with a peak at a certain point, such as Figure 3 As shown in the figure. The DC component I of the output of the square circuit 110 DC It can have an amplitude:

[0069]

[0070] And the AC component I of the output of the square circuit 110 DC It can have an amplitude:

[0071] (A RF A LO +A LO A IM )f BB +A RF A IM 2f BB .

[0072] Typically, the desired pitch power is a function of the key signature s(A). RF ) has a function or tone sign s(A) that leaks more than the local oscillator LO The amplitude and tone of the image are functions of the key signature s(A). IM The amplitude is much larger. Directly supplying the output of the square circuit 110 to the transimpedance amplifier 26 causes some problems, which can prevent the detection of local oscillator leakage and the function or key signature of the image tone. One problem is the large DC component I. DCThis will cause the transimpedance amplifier 26 to saturate. Another problem is that the voltage at node N will vary based on the input power of the RF signal, which may cause the bias voltage at node N to exceed the operating voltage range designed for the operation of the squaring circuit 110 and the transimpedance amplifier 26. A third problem is that high operating power may cause nonlinear operation of the circuit. Thus, aspects of the embodiments of this disclosure relate to filtering out the DC component I of the output 4 of the squaring circuit 110. DC This produces a filtered output, which essentially contains only the AC component I of the output of the square circuit 110. AC Including the representation of local oscillator leakage s(A) LO ) and the representation of image pitch s(A IM The AC component I of the output of the square circuit 110 AC It is provided to the transimpedance amplifier 26.

[0073] A method for filtering out the DC component I of the output 4 of a square circuit 110 DC The comparison method includes a DC blocking capacitor between the output of the square circuit and the input of the transimpedance amplifier 26, while a bias circuit (e.g., a bias resistor or a diode-connected PMOS transistor) is coupled between the voltage source VDD and the square circuit 110. However, in order to make the DC blocking capacitor operate at a baseband frequency f, for example, from 1MHz to 400MHz... BB When the DC signal is blocked during operation, such a DC blocking capacitor would need to be very large, necessitating the use of an integrated circuit with an impractical area or an off-chip capacitor (thus requiring the use of one of the limited number of pins on the chip), both of which significantly increase the manufacturing cost of such devices. Furthermore, the modulation of the RF power alters the bias point of the node between the DC blocking capacitor, the bias circuit, and the square circuit 110, causing the output of the square circuit 110 to become nonlinear.

[0074] The DC component I at the output terminal 4 of the square circuit 110 is filtered out. DC Another comparative approach is to include a DC bypass inductor between the power supply VDD and the square circuit 110. However, similar to the DC blocking capacitor method described above, a DC bypass inductor capable of controlling the baseband frequency in the range of 1MHz to 400MHz would require a very large inductor, which would also need to be done off-chip. Therefore, using a large DC bypass inductor would significantly increase manufacturing costs.

[0075] Therefore, as Figure 3 As shown, according to some embodiments of this disclosure, the detector circuit 100 includes a DC current sink or voltage follower 150, which provides a low-impedance current path to absorb the DC component I of the output 4 of the square circuit 110. DCMore specifically, the DC current sink 150 presents a very low output impedance at DC and a high impedance at AC signals. Figure 4 The frequency-dependent output impedance Z of a voltage follower of a detector according to an embodiment of the present disclosure is schematically depicted. in The illustration. For example... Figure 4 As shown, in some embodiments, the DC current absorber 150 operates below the desired cutoff frequency f. cutoff At low signal frequencies (e.g., less than 700Hz (0.7kHz), such as 100Hz), the output impedance is very low (e.g., about 1.5Ω). In some embodiments, the DC current sink 150 operates above the desired cutoff frequency f. cutoff The signal frequency exhibits high impedance (e.g., approximately 50 kΩ). The DC current sink 150 also sets a DC level at the input of the transimpedance amplifier 26, which functions as a differential amplifier (e.g., setting the input voltage of the transimpedance amplifier 26 at node N to the reference voltage V provided as input to the DC current sink 150). REF ).

[0076] Therefore, for example, such as Figure 3 and Figure 4 As shown, the detector circuit 100 includes a DC current absorber 150 that only absorbs the AC signal I from the output 4 of the square circuit 110. AC This is provided as input to the transimpedance amplifier 26. Therefore, the DC component of the output 4 of the square circuit 110 (which represents the power of the power amplifier for the desired RF signal) does not cause the aforementioned problem, thus allowing the detection of the local oscillator leakage function or tone mark s(A) LO ) and the function or key signature s(A) of the image pitch. IM This can then be provided to a modem for calibration (e.g., in the digital domain). For example, the DC current sink 150 in various embodiments can prevent saturation of the transimpedance amplifier 26, maintain a stable bias voltage at node N, and draw most of the power at node N to keep the circuit within its linear operating range.

[0077] Figure 5 This is a circuit diagram illustrating a square circuit according to an embodiment of the present disclosure. Figure 5 As shown, in one embodiment, the square circuit 110 includes a first NMOS transistor 112 and a second NMOS transistor 114 having substantially the same transistor characteristics, wherein the source of each transistor is grounded and the drain of each transistor is connected to node N. According to the bias voltage V... G Two transistors are driven in the saturation region. The input signal 2 from power amplifier 18 is represented herein as voltage v. dAnd it is differentially applied to the gates of the first NMOS transistor 112 and the second NMOS transistor 114. More specifically, the bias voltage V G Half of the input signal 2 (v d The sum of / 2) (V) G +v d / 2) is supplied to the gate of the first NMOS transistor 112, and the bias voltage V G and half of the input signal 2 (v d The difference between / 2) (V) G -v d / 2) is provided to the gate of the second NMOS transistor 114.

[0078] The drain currents i1 and i2 flowing from the drain to the source of the corresponding transistors 112 and 114 are the gate-source voltages (V) of the transistors. GS The square-law function of ). By summing over currents i1 and i2, the linear components (e.g., due to V) G The generated components are canceled out, but the addition of second-order components produces a signal including a second harmonic, which comprises a mixed product and a power. Therefore, the output current i of the square circuit 110 includes the input signal v. d The square of.

[0079] Figure 6 This is a circuit diagram illustrating a DC current sink according to an embodiment of the present disclosure. Figure 6 In the embodiment shown, the reference voltage V REF The inverting input of the operational amplifier (op-amp) 152 (e.g., the reference voltage V) is provided REF (Provided by a reference voltage source). The output of operational amplifier 152 is connected to the gate of PMOS transistor 154. A power supply (or voltage source) VDD is provided to the sources of operational amplifier 152 and PMOS transistor 154. The drain of PMOS transistor 154 is connected to node N, which is also connected to the non-inverting input of operational amplifier 152. Additionally, in some embodiments, capacitor 156 is connected between the power supply VDD and the gate of PMOS transistor 154 as an optional component for stability compensation. Figure 6 In the illustrated embodiment, Miller compensation is not used to avoid high-frequency short circuits (e.g., there is no capacitor between the output of operational amplifier 152 and the non-inverting input of operational amplifier 152).

[0080] Despite Figure 6The present disclosure describes some embodiments of using voltage follower circuits as DC current sinks in operational amplifier-based circuits; however, the embodiments described herein are not limited thereto, and other known and suitable designs for voltage follower or DC current sink circuits can be used, for example, voltage followers based on low-dropout regulators (LDOs) can also be used. Furthermore, as those skilled in the art will understand, regarding Figure 6 The embodiment of the DC current absorber 150 shown and described can be related to... Figure 5 The square circuit 110 shown and described is used in combination.

[0081] Thus, some embodiments of this disclosure relate to a detector circuit 100 that includes a squaring circuit 110 (e.g., a CMOS squaring circuit) that downconverts LO leakage and image tone to f. BB and 2f BB At the offset, where harmonics are eliminated, and a detection signal with second harmonics is provided to the transimpedance amplifier 26 of receiver 20, thereby allowing existing hardware to be shared between multiple purposes and reducing the need for additional area on the receiver chip for providing feedback for recalibration of transceiver 1 (e.g., for detecting LO leakage and I / Q imbalance).

[0082] In some embodiments, the DC current absorber 150 provides a low-power (e.g., consuming 100 μA at 1V VDD) area-efficient (e.g., requiring no large capacitors and / or inductors and by reusing existing components of the receiver circuitry) method for removing the DC component of the signal, wherein the DC component exhibits a power component and is relative to the baseband frequency f of the output of the square circuit 110. BB Components and 2f BB The component provides an impedance greater than 50KΩ.

[0083] Therefore, aspects of embodiments of this disclosure provide systems and methods for detecting local oscillator leakage and image tone in the output of an amplifier (e.g., a power amplifier) ​​on the transmitting side of a radio transceiver. Aspects of embodiments of this disclosure can be implemented in a compact circuit by reusing portions of the radio receiver 20 of the radio transceiver to detect LO leakage and image tone; and by using a voltage follower or other DC current sink circuitry to substantially remove the radio frequency signal from the detector output without relying on the use of large DC blocking capacitors or large DC bypass inductors. The use of a square circuit (e.g., which may consist of only two transistors) and a simple voltage follower also allows embodiments of this disclosure to operate at low power (e.g., without requiring an additional oscillator or mixer).

[0084] While embodiments of the present disclosure have been described in conjunction with certain exemplary embodiments, it should be understood that embodiments of the present disclosure are not limited to the disclosed embodiments, but rather are intended to cover various modifications and equivalent arrangements within the spirit and scope of the appended claims and their equivalents.

Claims

1. A radio transceiver, comprising: a radio transmitter including a power amplifier; a radio receiver including a transimpedance amplifier; and a detector circuit connected between the power amplifier of the radio transmitter and the transimpedance amplifier of the radio receiver and including: a squaring circuit configured to receive an output of the power amplifier of the radio transmitter and to provide an output current to a node connected to an input of the transimpedance amplifier of the radio receiver; and a DC current sink electrically connected to an output of the squaring circuit via the node.

2. The radio transceiver of claim 1, wherein the output current of the squaring circuit includes a direct current, DC, component and an alternating current, AC, component, the DC component including a function of a desired tone included in the output of the power amplifier, the AC component including a function of a local oscillator leakage tone included in the output of the power amplifier at a first frequency and a function of an image tone included in the output of the power amplifier at a second frequency.

3. The radio transceiver of claim 2, wherein the DC current sink is configured to filter out the DC component of the output current of the squaring circuit to produce a filtered output of the squaring circuit, the filtered output including the function of the local oscillator leakage tone and the function of the image tone.

4. The radio transceiver of claim 2, wherein the first frequency is equal to a baseband frequency of an input baseband signal and the second frequency is twice the baseband frequency.

5. The radio transceiver of claim 1, wherein the radio transmitter further includes a transmit mixer configured to mix an output of a transmitter local oscillator with an input baseband signal to produce a transmit mixer output, the transmit mixer output being provided as input to the power amplifier, wherein the squaring circuit is configured to produce the output current at the node connected to the transimpedance amplifier of the radio receiver through a detector switch, and wherein the radio receiver further includes a receive mixer configured to mix a received signal with an output of a receiver local oscillator, an output of the receive mixer being connected to the transimpedance amplifier through a receiver switch.

6. The radio transceiver of claim 1, wherein the radio transmitter, the radio receiver, and the detector circuit are included in an integrated circuit.

7. The radio transceiver of claim 1, further comprising: a receiver switch connected between a receive mixer of the radio receiver and the transimpedance amplifier, the receiver switch configured to disconnect the radio receiver during calibration of the radio transceiver using the detector circuit; and a detector switch connected between the squaring circuit and the node, the detector switch configured to disconnect the squaring circuit during calibration of the radio transceiver using the detector circuit. ​ ​ a detector switch connected between the output of the squaring circuit and the transimpedance amplifier, the detector switch configured to connect the output of the squaring circuit of the detector circuit to the transimpedance amplifier during calibration of the radio transceiver.

8. The radio transceiver of claim 2, wherein the radio transmitter further comprises a transmit mixer configured to mix an output of a transmitter local oscillator with an input baseband signal to produce a mixer output, the mixer output provided to the power amplifier, and wherein the local oscillator leakage tone corresponds to the output of the transmitter local oscillator.

9. The radio transceiver of claim 8, wherein a signal path of the transmit mixer comprises an in-phase portion and a quadrature portion, and wherein the image tone corresponds to an imbalance between the in-phase portion and the quadrature portion of the signal path.

10. The radio transceiver of claim 1, wherein the squaring circuit comprises: a first transistor; and a second transistor having the same transistor characteristics as the first transistor, the first transistor and the second transistor connected in parallel between the output of the squaring circuit and ground, wherein the output current of the squaring circuit corresponds to a sum of a first current flowing through the first transistor and a second current flowing through the second transistor in accordance with the output of the power amplifier differentially provided to a first gate of the first transistor and a second gate of the second transistor.

11. The radio transceiver of claim 1, wherein the DC current sink comprises a low dropout regulator based voltage follower.

12. The radio transceiver of claim 1, wherein the DC current sink comprises: an operational amplifier having a non-inverting input connected to the output of the squaring circuit and an inverting input connected to a reference voltage source; a transistor connected between a power supply and the output of the squaring circuit, and a gate of the transistor connected to an output of the operational amplifier; and a capacitor connected between the power supply and the gate of the transistor.

13. The radio transceiver of claim 1, wherein an output impedance of the DC current sink is frequency dependent and has a low output impedance at frequencies below a desired cutoff frequency and a high output impedance at other frequencies.

14. A method for a radio transceiver comprising a radio transmitter, a radio receiver, and a detector circuit, the radio transmitter comprising a power amplifier, the radio receiver comprising a transimpedance amplifier, the detector circuit connected between the power amplifier of the radio transmitter and the transimpedance amplifier of the radio receiver, the method comprising: ​ The output of the power amplifier of the radio transmitter is provided to a squaring circuit of the detector circuit, such that the squaring circuit provides an output current to a node connected to an input of the transimpedance amplifier of the radio receiver, wherein the output of the power amplifier comprises: a desired tone; a local oscillator leakage tone; and an image tone; and the output current of the squaring circuit comprises: a direct current, DC, component comprising a function of the desired tone; and an alternating current, AC, component comprising: a function of the local oscillator leakage tone; and a function of the image tone; the DC component of the output current is absorbed by a DC current sink of the detector circuit to produce a filtered output of the squaring circuit, wherein the DC current sink is electrically connected to an output of the squaring circuit via the node, and the filtered output comprises the function of the local oscillator leakage tone and the function of the image tone; and the local oscillator leakage tone and the image tone are detected based on the filtered output.

15. The method of claim 14, further comprising: The filtered output is provided to the transimpedance amplifier.

16. The method of claim 14, wherein the radio receiver further comprises a receive mixer configured to mix a received signal with an output of a receiver local oscillator, an output of the receive mixer being connected to the transimpedance amplifier by a receiver switch, wherein the detector circuit comprises an output configured to provide the filtered output to the transimpedance amplifier by a detector switch, and wherein the method further comprises: in detecting the local oscillator leakage tone and the image tone of the radio transceiver, the output of the detector circuit is connected to the transimpedance amplifier by the detector switch; and the receive mixer is disconnected from the transimpedance amplifier by the receiver switch.

17. The method of claim 14, further comprising: mixing, by a transmit mixer of the radio transmitter, an input baseband signal with an output of a transmitter local oscillator of the radio transmitter to produce a mixer output; and amplifying, by the power amplifier of the radio transmitter, the mixer output to produce the output of the power amplifier.

18. The method of claim 17, wherein the local oscillator leakage tone corresponds to the output of the transmitter local oscillator.

19. The method of claim 17, wherein a signal path of the transmit mixer comprises an in-phase portion and a quadrature portion, and wherein the image tone corresponds to an imbalance between the in-phase portion and the quadrature portion of the signal path.

20. The method of claim 14, wherein the squaring circuit comprises: a first transistor; and a second transistor having the same transistor characteristics as the first transistor, the first transistor and the second transistor being connected in parallel between an output of the squaring circuit and ground, ​ ​ wherein the output current of the squaring circuit corresponds to a sum of a first current flowing through the first transistor and a second current flowing through the second transistor from the output of the power amplifier, wherein the output of the power amplifier is differentially provided to a first gate of the first transistor and a second gate of the second transistor.

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