Transceiver with time-domain IQMM estimation

Abstract

To provide a transceiver with time-domain IQMM estimation.SOLUTION: In a transceiver, an auxiliary receiver 104 includes a switch network 134 and a mixer 136 in an analog circuitry 112, and an IQ mismatch (IQMM) estimator 144 in a digital circuitry 110. The switch network is adapted to be coupled to the output of a transmitter 102. The switch network selectively swaps the complementary signals of the differential pair. The mixer is coupled to the switch network and downconverts the output signal of the switch network. An IQMM estimation circuit is coupled to the mixer and estimates the IQMM of the transmitter on the basis of the output signal of the mixer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Wireless communication devices are widely used to provide communication of voice signals, multimedia signals, data signals, and other information. In some wireless communication devices, a digital baseband circuit provides a data stream of complex baseband data to the transmitter. The transmitted baseband data may be carried by a quadrature transmitter signal represented by a real (common-in-phase (I)) component and an imaginary (quadrature (Q)) component. In the transmitter, the common-in-phase and quadrature components of the transmitter signal are processed along parallel common-in-phase and quadrature component circuit paths. Signal processing provided along the common-in-phase and quadrature paths may include digital-to-analog conversion, mixing, filtering, power amplification, etc. The common-in-phase and quadrature signals are modulated to provide the transmitted analog radio frequency (RF) signal. Ideally, the common-in-phase and quadrature components are processed along parallel circuit paths in the transmitter, and the circuit elements along one path are exactly identical or "match" the corresponding circuit elements along the other parallel path. [Overview of the project]

[0002] In one example, the transceiver circuit includes a transmitter and a receiver. The transmitter includes an IQ mismatch (IQMM) correction circuit and a power amplifier. The power amplifier includes an input and an output. The input is coupled to the IQMM correction circuit. The receiver is coupled to the output of the power amplifier. The receiver includes a switch network, a mixer, and an IQMM estimation circuit. The switch network is coupled to the output of the power amplifier. The switch network includes a first input, a second input, a first output, a second output, a first switch, a second switch, a third switch, and a fourth switch. The first switch is coupled between the first input and the first output. The second switch is coupled between the first input and the second output. The third switch is coupled between the second input and the second output. The fourth switch is coupled between the second input and the first output. The mixer is coupled between the first output and the second output of the switch network. The IQMM estimation circuit is coupled to the mixer and the IQMM correction circuit.

[0003] In another example, the receiver includes a switch network, a mixer, and an IQMM estimation circuit. The switch network is adapted to be coupled to the transmitter's output. The switch network is configured to selectively swap the complementary signals of a differential pair. The mixer is coupled to the switch network and configured to downconvert the switch network's output signal. The IQMM estimation circuit is coupled to the mixer and configured to estimate the transmitter's IQMM based on the mixer's output signal.

[0004] In a further example, a method for IQMM estimation includes calculating a first IQMM estimation for a transmitter and receiver based on a symmetric down-conversion of a first received signal, and calculating a second IQMM estimation for a transmitter and receiver based on an asymmetric down-conversion of a second received signal. The transmitter IQMM estimation is calculated based on the first and second IQMM estimations. The transmitter IQMM estimation is applied to modify the signal transmitted by the transmitter.

Brief Description of the Drawings

[0005] For a detailed description of various examples, refer to the accompanying drawings.

[0006] [Figure 1] FIG. is a block diagram of an exemplary transceiver including symmetric and asymmetric downconversions for estimating transmitter IQ mismatch (IQMM).

[0007] [Figure 2] FIG. is a block diagram of a part of an exemplary auxiliary receiver including a switch network for use in symmetric and asymmetric downconversions.

[0008] [Figure 3] FIG. is a schematic diagram of an exemplary switch network suitable for use in symmetric and asymmetric downconversions.

[0009] [Figure 4] FIG. 1 shows various data modification operations of the transceiver.

[0010] [Figure 5] FIG. is a flowchart of a method for transmitter IQMM correction including transmitter IQMM estimation based on symmetric and asymmetric downconversions.

[0011] In the figures, the same reference numerals are used for the same or similar features (function and / or structure).

Modes for Carrying Out the Invention

[0012] In communication systems compliant with the IEEE 802.11 standard, orthogonal frequency division multiplexing (OFDM) subcarriers are modulated using quadrature amplitude modulation (QAM) for transmission. QAM uses common-mode (I) signals, quadrature (Q) signals, and associated parallel processing paths. The quality of the transmitted signal is evaluated using a parameter called error vector amplitude (EVM). EVM covers various transmitter faults, including radio frequency (RF) nonlinearity, IQ mismatch (IQMM), and phase noise (IPN).

[0013] IQMM is the gain or phase difference (mismatch) in parallel common-mode and quadrature channel processing paths. To meet the EVM target of -28 dB, the target signal-to-noise ratio (SNR) of the IQMM is 45 dB. To provide compensation for the IQMM, the amount of IQMM to be compensated is estimated in an auxiliary receiver coupled to the transmitter. There are various problems and limitations in measuring IQMM. In some cases, to facilitate low-power operation, the IQMM is measured in the time domain. Since the frequency band used to implement IEEE 802.11-based communication is shared with other wireless technologies (e.g., Bluetooth, ZIGBEE, etc.), IQMM estimation may be performed using ODFM packets rather than continuous wave tones. The auxiliary receiver coupled to the transmitter output provides a down-conversion of the transmitted signal for measuring the transmitter IQMM. However, the auxiliary receiver adds its own IQMM to the received signal, and the measurement of the transmitter IQMM is not affected by the auxiliary receiver's frequency-dependent IQMM (IQFD).

[0014] In the transceiver examples (transmitter and associated auxiliary receiver) described herein, time-domain IQMM estimation is performed using an indirect fitting algorithm. Symmetric and asymmetric down-conversions are used to separate the transmitter IQMM and auxiliary receiver IQMM from the transmitter-auxiliary receiver loop IQMM. Asymmetric down-conversion (conjugate generation) is performed by swapping the differential lines driving the auxiliary receiver mixer (i.e., inverting either the I or Q signal at the mixer input). IQMM estimation is unaffected by the auxiliary receiver's IQMM and IQFD. Two iterations are used in the estimation. The first iteration estimates the transmitter-auxiliary receiver loop IQMM using normal (symmetric) down-conversion (+I and +Q). The second iteration estimates the transmitter-auxiliary receiver loop IQMM using asymmetric down-conversion (+I and -Q, or -I and +Q), where the auxiliary receiver input is the conjugate of the original signal, and the resulting transmitter IQMM is the complex conjugate of the first iteration.

[0015] Figure 1 is a block diagram of an exemplary transceiver 100, including symmetric and asymmetric downconversion for estimating the transmitter IQMM. The transceiver 100 includes a transmitter 102, an auxiliary receiver 104, a local oscillator 114, and a coupler 116. The auxiliary receiver 104 is coupled to the transmitter 102 via the coupler 116. The auxiliary receiver 104 is used to provide feedback of the signal transmitted by the transmitter 102. The transceiver 100 functions for practical multicarrier signals, i.e., signals that can be used in an operating mode, during the exchange of operational data between wireless peers, such as using OFDM modulated signals.

[0016] OFDM signals (e.g., OFDM data symbols) can be used to support data communication in wireless applications such as PAN networks, WLAN networks (e.g., 802.11x WiFi), WAN networks (e.g., 4G and LTE cellular networks), WiMAX networks, mobile WiMAX networks, ADSL and VDSL networks, DVB-T and DVB-H networks, and UWB networks. The modulation schemes used may include, for example, phase-shifted modulation (PSK), amplitude-shifted modulation (ASK), or quadrature amplitude modulation (QAM).

[0017] The transceiver 100 includes a transmitter digital circuit element 106 and a transmitter analog circuit element 108. The transmitter digital circuit element 106 includes a constellation mapper 118, an inverse fast Fourier transform (IFFT) circuit 120, a guard interval (GI) and window circuit 122, an IQMM correction circuit 124, and a digital-to-analog converter (DAC) 126. The transmitter analog circuit element 108 includes a baseband filter 128, a mixer 130, and a power amplifier 132.

[0018] The constellation mapper 118 receives a digital signal, indicated as TBITS (for example, from a processor), and generates modulated I and Q signals from it for processing in parallel I and Q paths. The constellation mapper 118 can map each vector to a transmitted symbol, which is a member of one or more pre-selected symbol alphabets that themselves can correspond to a symbol constellation, using a constellation table. The IFFT circuit 120 implements an inverse Fourier transform that converts the frequency domain signal received from the constellation mapper 118 into time domain I and Q signals. The GI and window circuit 122 and the IQMM correction circuit 124 process the time domain signal received from the IFFT circuit 120.

[0019] The GI and window circuit 122 perform two tasks. The GI and window circuit 122 insert guard intervals to prevent intersymbol interference caused by multipathing. The GI and window circuit 122 also use windowing to reduce energy at out-of-band frequencies by generating gradual amplitude rises and falls at symbol boundaries.

[0020] The IFFT circuit 120 may further include an orthogonal frequency division multiple access (OFDMA) module, which maps different modulated streams to different subcarrier groups before IFFT processing. In some implementations, the IFFT circuit 120 may perform IFFT on the output of the constellation mapper 118 to generate one or more time-domain signals associated with one or more frequency ranges. In some implementations, the IFFT circuit 120 may be configured to use one or more FFT bandwidth frequencies such as 20 MHz, 40 MHz, 80 MHz, or 160 MHz. In some implementations, the IFFT circuit 120 may perform different IFFTs on the modulated data stream according to different FFT bandwidths.

[0021] The output of the IQMM correction circuit 124 is coupled to a DAC 126 coupled to a baseband filter 128. The DAC 126 and baseband filter 128 convert the time-domain signal received from the IQMM correction circuit 124 into an analog signal and shape the analog signal for transmission. The IQMM correction circuit 124 is configured to receive a digital time-domain complex representation of the transmitter 102's IQMM (denoted as θ) from the IQMM estimation circuit 144. The estimation of the transmitter IQMM is described herein. The IQMM estimation circuit 144 receives the I and Q time-domain signals, denoted as YI and YQ, from the output of the digital filter 142 in the auxiliary receiver 104, and the GI and time-domain I and Q signals, denoted as XI and XQ, from the output of the window circuit 122 in the transmitter 102, and calculates an estimate of the transmitter 102's IQMM. Thus, the disclosed estimation and compensation of the transmitter 102's IQMM are performed in the time domain, not the frequency domain.

[0022] The IQMM for the entire transmitter-auxiliary receiver loop (including transmitter 102 and auxiliary receiver 104) can be estimated as follows: TIFF2023080042000002.tif853 Here, θ is the IQMM for the entire transmitter-auxiliary receiver loop, x is the transmitter baseband signal before fault and correction. x n This is the nth sample of x, N is the packet length, y RX This is a transmitted signal with IQMM interference, which is received and down-converted to baseband. y RXn is, y RX This is the nth sample.

[0023] In transceiver 100, the IQMM estimation circuit 144 estimates the IQMM of transmitter 102, not the IQMM of the entire transmitter-auxiliary receiver loop, and passes the IQMM of transmitter 102 to the IQMM correction circuit 124 for use in IQMM correction. As will be explained later, symmetric and asymmetric down-conversion is used to extract the transmitter IQMM from the IQMM of the transmitter-auxiliary receiver loop. Therefore, in transceiver 100, the IQMM compensation applied to the transmitted signal is not subject to the IQMM of auxiliary receiver 104.

[0024] The IQMM estimation provided by the IQMM estimation circuit 144 and the IQMM correction performed by the IQMM correction circuit 124 can be implemented in hardware HW or firmware FW (software). In hardware implementation, a field-programmable array (FPGA) or application-specific integrated circuit (ASIC) may be used. In firmware implementation, a processor (e.g., a digital signal processor) that executes instructions stored as firmware may be used.

[0025] The baseband filter 128 is coupled to the mixer 130. The mixer 130 includes upconverting mixers for the I and Q paths. The mixer 130 receives local oscillator signals shifted by 90 degrees from the local oscillator 114 and mixes these local oscillator signals with the I and Q signals received from the baseband filter 128. The local oscillator 114 may provide a frequency that is the same as or very close to the carrier frequency of the intended transmitter output signal. Upconversion upconverts the analog signal to the corresponding frequency band and transmits it.

[0026] The local oscillator 114 may include a phase-locked loop (PLL). The upconverted signals generated by the mixer 130 are combined (e.g., added) and supplied to the power amplifier 132. The power amplifier 132 may include a low-noise amplifier and may be adapted so that its output is coupled to an antenna (not shown).

[0027] Coupler 116 is located between transmitter 102 and auxiliary receiver 104 and loops back the signal from the output of power amplifier 132 to the I and Q paths of auxiliary receiver 104. Similar to transmitter 102, auxiliary receiver 104 processes the I and Q signals in parallel I and Q paths. Coupler 116 is an analog component with some signal attenuation and generally includes linear passive components that may or may not add phase to the signal. For example, coupler 116 may include an RF capacitor or a resistor.

[0028] The auxiliary receiver 104 receives the RF signal transmitted by the transmitter 102 via the coupler 116. For example, the received signal may include a group of OFDM subcarriers. The auxiliary receiver 104 includes digital circuit elements 110 and analog circuit elements 112. The analog circuit elements 112 include a switch network 134, a mixer 136, a baseband filter 138, and an analog-to-digital converter (ADC) 140. The digital circuit elements 110 include a digital filter 142, an FFT circuit 146, a BCC decoder 148, and an IQMM estimation circuit 144. Various components of the digital circuit elements 110 and analog circuit elements 112 may be provided for both the I and Q processing paths. For example, the switch network 134 may provide separate switch circuits for the I path and the Q path, and the mixer 136 may include separate mixing circuits for the I path and the Q path, etc.

[0029] Switch network 134 is coupled to coupler 116 and receives I and Q signals looped back from transmitter 102. Switch network 134 includes switches that connect the differential I and Q signals received from coupler 116 to mixer 136. The switches in switch network 134 may be configured to pass the received signals to perform symmetric down-conversion in mixer 136 or to pass the received signals to perform asymmetric down-conversion in mixer 136. In transceiver 100, symmetric and asymmetric down-conversion is repeatedly performed on the received signals, and the results of the symmetric and asymmetric down-conversion are processed to estimate the IQMM of transmitter 102.

[0030] Mixer 136 mixes the 90-degree shifted local oscillator signal received from local oscillator 114 with the I and Q signals received from switch network 134, downconverting the I and Q signals. Baseband filter 138 and ADC 140 filter the downconverted signals, converting them into a digital data sequence. ADC 140 is coupled to digital filter 142. FFT circuit 146 converts the time-domain I and Q signals received from digital filter 142 into frequency-domain signals. BCC decoder 148 outputs the decoded bitstream.

[0031] Figure 2 is a block diagram of a portion of the auxiliary receiver 104, including the switch network 134. The switch network 134 includes inputs 134A and 134B, which are coupled to the coupler 116. Outputs 134C and 134D of the switch network 134 are coupled to the mixer 136. In Figure 2, mixer 210 of the mixer 136 is shown for reference. The switch network 134 includes switches 202, 204, 206, and 208. The first terminal of 202 is coupled to 134A, and the second terminal of 202 is coupled to 134C. The first terminal of 204 is coupled to 134A, and the second terminal of 204 is coupled to 134D. The first terminal of 206 is coupled to 134B, and the second terminal of 206 is coupled to 134D. The first terminal of 208 is coupled to 134B, and the second terminal of 208 is coupled to 134C. The output of coupler 116 forms a differential pair that carries the I and Q signals. Switch network 134 passes the signals to mixer 210 for down-conversion. Switch network 134 may be configured to swap the signals of the differential pair in order to perform asymmetric down-conversion in mixer 210. Switch network 134 may be configured to pass the signals of the differential pair (without swapping) in order to perform symmetric down-conversion. More specifically, in order to perform symmetric down-conversion in mixer 210, switches 202 and 206 are closed and switches 204 and 208 are open, and in order to perform asymmetric down-conversion in mixer 210, switches 204 and 208 are closed and switches 202 and 206 are open.

[0032] FIG. 3 is a schematic diagram of an exemplary switch network 300 suitable for use in symmetric and asymmetric downconversions. Switch network 300 is an implementation of switch network 134. Switch network 300 is coupled to mixer 310. Mixer 310 is an implementation of mixer 210. Switch network 300 includes transistors 302, 304, 306, and 308. Transistor 302 corresponds to switch 202 of switch network 134. Transistor 304 corresponds to switch 204 of switch network 134. Transistor 306 corresponds to switch 206 of switch network 134. Transistor 308 corresponds to switch 208 of switch network 134. To perform symmetric downconversion, transistors 302 and 306 are turned on and transistors 304 and 308 are turned off. To perform asymmetric downconversion, transistors 304 and 308 are turned on and transistors 302 and 306 are turned off.

[0033] FIG. 4 illustrates various data modification operations in the transmitter - auxiliary receiver loop of transceiver 100. Data (x IN ) to be transmitted is provided to IQMM correction block 402. IQMM correction block 402 corresponds to IQMM correction circuit 124. The IQMM correction output (y corr ) of IQMM correction block 402 is impaired by the transmitter IQMM represented by Tx IQMM block 404 and may represent non - idealities in any of DAC 126, baseband filter 128, mixer 130, and / or power amplifier 132. The IQMM - impaired transmitted data is labeled as y BB . y BB is up - converted in composite mixer block 406 to generate transmitted signal y TX . Gain and / or rotation is applied to the I and Q signals y TX as represented by gain and rotation block 408 to generate signal y rotThis generates the signal. Gain and rotation may be due to differences in trace length, component delay / attenuation, etc., in the clock path from the local oscillator 114 to the mixer 136 for the I and Q paths. For example, even if the same oscillator signal is provided to the I and Q path mixers, differences in the distribution of the clock signal may result in differences in the gain or rotation during down-conversion.

[0034] In the composite mixer input block 410, y rot The differential pair signals carrying the I and Q signals are switched in the switch network 134 to generate the input to the mixer 136. In the composite mixer input block 410, the signal for symmetric down-conversion is represented as (y × cos); (y × sin). The signal for asymmetric down-conversion is represented as (y × cos); (-y × sin) or (-y × cos); (y × sin), where -y represents the inversion of the I or Q signal by swapping the differential pair signals in the switch network 134. An IQMM fault in the auxiliary receiver 104 is represented by the AuxRx IQMM block 412, and the loopback data damaged by the auxiliary receiver 104 is y RX It is indicated as follows. The IQ estimation block 414 corresponding to the IQMM estimation circuit 144 of the auxiliary receiver 104 uses the IQMM of the transmitter-auxiliary receiver and the IQMM of the transmitter. i We estimate it to be v. i This is provided to the IQMM correction block 402 for use when compensating for the Tx IQMM block 404.

[0035] Regarding Figure 4, ideal y BB This can be expressed as follows: y BB =Re{x}+j·Im{x} (2) In reality, if IQMM is not corrected, the baseband signal y BB It will be damaged as follows. y BB =Re{x}·ae jφ +j·Im{x} (3) formula: TIFF2023080042000003.tif2753RF signal y TX This can be expressed as follows: The IQMM for TIFF2023080042000004.tif751Tx can be estimated as follows. v = β / α (8)

[0036] The estimation of v(IQMM) via a transmitter-auxiliary receiver loop (using symmetric down-conversion) can be expressed as follows (assuming transmitter-auxiliary receiver gain (A) and rotation (θ)). G=Ae jθ (9) y rot =y Tx · G (10) The auxiliary receiver input signal can be represented as follows: TIFF2023080042000005.tif751v loop The IQMM (of the transmitter-auxiliary receiver loop) can be expressed as follows: TIFF2023080042000006.tif1570TIFF2023080042000007.tif753β RX β TX * <<α RX α TX Therefore, the following holds true. TIFF2023080042000008.tif1660

[0037] The estimation of v via a transmitter-auxiliary receiver loop (using asymmetric down-conversion) can be expressed as follows (using transmitter-auxiliary receiver gain (A) and rotation (θ)). G=Ae jθ (17) y rot =y Tx * · G (18) The auxiliary receiver input signal can be represented as follows: TIFF2023080042000009.tif450v loopThis can be expressed as follows: TIFF2023080042000010.tif2570β RX β TX * <<α RX α TX Therefore, the following holds true. TIFF2023080042000011.tif1759

[0038] The transmitter IQMM is calculated as follows. Final calculation -1 We consider two v IQMM estimations using symmetric and asymmetric downconversion as follows. Considering TIFF2023080042000012.tif1656t1, the following applies. Considering TIFF2023080042000013.tif2657t2, the result is as follows. Considering TIFF2023080042000014.tif2554t3, the result is as follows. TIFF2023080042000015.tif1448 Note: t3 is a purely imaginary number.

[0039] Final calculation - 2 TIFF2023080042000016.tif746 and Therefore, the following applies to TIFF2023080042000017.tif746. TIFF2023080042000018.tif2757 Here, The filename is TIFF2023080042000019.tif651. Considering t4, it becomes as follows. TIFF2023080042000020.tif1865

[0040] Final calculation -3 TIFF2023080042000021.tif1751 Finally, |α TX | and arg(α TX Using both of the above, v TXThe (transmitter IQMM) can be determined as follows: TIFF2023080042000022.tif945

[0041] This transmitter IQMM can then be applied by IQMM correction block 402, which cancels out the IQMM applied as a result of Tx IQMM 404, and as a result the corrected y BB The value should be the ideal value of equation (2) or close to it.

[0042] Figure 5 is a flowchart for Method 500 for transmitter IQMM correction, including transmitter IQMM estimation based on symmetric and asymmetric down-conversion. For convenience, the actions are shown sequentially, but at least some of the actions shown may be performed in a different order and / or in parallel. Also, some implementations may perform only some of the actions shown. The operation of Method 500 may be performed by the transceiver 100. The calculation of Method 400 may be performed by the hardware of the IQMM estimation circuit 144 and / or by firmware performed by the processor of the IQMM estimation circuit 144.

[0043] In block 502, the transmitter 102 transmits one or more OFDM packets during normal operation. Transmission of OFDM packets may include applying a certain amount of IQMM correction. In initial operation, the IQMM correction applied to OFDM packets may be set to zero or a default value. OFDM packets are looped back to the auxiliary receiver 104 via the coupler 116.

[0044] In block 504, the auxiliary receiver 104 is configured for symmetric down-conversion. For both the I and Q signals, the switch network 134 is configured to pass the differential pair signals that carry OFDM packets without swapping (i.e., without inversion). In the switch network 134 (for both the I and Q signals), switches 202 and 206 are closed, and switches 204 and 208 are open. The mixer 136 down-converts the signals received from the switch network 134. The down-converted signals are filtered by the baseband filter 138, digitized by the ADC 140, and further filtered by the digital filter 142.

[0045] In block 506, the IQMM estimation circuit 144 calculates the IQMM of the transmitter 102 and auxiliary receiver 104 based on symmetrically down-converted OFDM packets according to equations (9) to (16).

[0046] In block 508, the transmitter 102 transmits one or more OFDM packets during normal operation. The OFDM packets are looped back to the auxiliary receiver 104 via the coupler 116.

[0047] In block 510, the auxiliary receiver 104 is configured for asymmetric down-conversion. For one of the I and Q signals, the switch network 134 is configured to swap (i.e., invert and pass) the differential pair signals carrying the OFDM packet. In the switch network 134 (for one of the I or Q signals), switches 204 and 208 are closed, and switches 202 and 206 are open. The mixer 136 down-converts the signal received from the switch network 134. The down-converted signal is filtered by the baseband filter 138, digitized by the ADC 140, and further filtered by the digital filter 142.

[0048] In block 512, the IQMM estimation circuit 144 calculates the IQMM of the transmitter 102 and auxiliary receiver 104 based on the asymmetrically down-converted OFDM packets according to equations (17) to (24).

[0049] In block 514, the IQMM estimation circuit 144 calculates the IQMM of transmitter 102 (according to equations (25) to (45)) based on the IQMMs of transmitter 102 and auxiliary receiver 104 calculated in block 506 using symmetric down-conversion and the IQMMs of transmitter 102 and auxiliary receiver 104 calculated in block 512 using asymmetric down-conversion. In some examples, the calculated IQMM is a measure of the uncorrected IQMM still present in transmitter 102 and represents the adjustment to the IQMM correction applied during the transmission of OFDM packets.

[0050] In block 516, the IQMM correction circuit 124 applies IQMM correction based on the transmitter's IQMM calculated in block 414 to adjust the signal to be transmitted by transmitter 102 (adjusting the signal's gain and phase). Applying IQMM may include generating an inverted image signal based on the IQMM and adding the inverted image signal to the signal to be transmitted.

[0051] In block 518, the transmitter transmits a signal (e.g., another set of OFDM symbols) by applying the IQMM correction in block 516.

[0052] The transmitter and IQMM estimation method implemented by the transmitter, as described herein, offer several advantages over other solutions. IQMM estimation is independent of the local oscillator leakage level, which affects the amplitude modulation detector method. Using special calibration patterns, such as continuous wave pulses, can lead to false radar triggering and violations of radiation specifications. Because IQMM estimation uses OFDM signals rather than special calibration patterns, it can be implemented across operational packets without allocating time and power to non-operational transmissions. IQMM estimation operates in the time domain using relatively small and inexpensive circuit elements. In contrast, frequency domain IQMM estimation uses large (e.g., more than 10 times larger than time domain circuit elements) FFT circuit elements and consumes considerable power. Compared to other time domain solutions, the IQMM estimation described herein is unaffected by the auxiliary receiver IQFD.

[0053] In this specification, the term “to combine” may encompass connections, communications, or signaling paths that enable a functional relationship consistent with the description herein. For example, if device A generates a signal to control control device B to perform a certain action, (a) in the first example, device A is combined with device B by a direct connection; and (b) in the second example, device A is combined with device B via an intervening component C, wherein the intervening component C does not alter the functional relationship between device A and device B, and so that device B is controlled by device A via a control signal generated by device A.

[0054] Devices "configured" to perform a certain task or function may be configured (e.g., programmed and / or hardwired) by the manufacturer at the time of manufacture to perform that function, and / or they may be configurable (or reconfigurable) by the user after manufacture to perform those functions and / or other additional or alternative functions. Such configurations may be via the device's firmware and / or software programming, or via the configuration and / or layout of hardware components and device interconnections, or a combination thereof.

[0055] A circuit or device described as containing certain components may instead be adapted to be coupled to those components to form the described circuit element or device. For example, a structure described as containing one or more semiconductor elements (such as transistors), one or more passive elements (such as resistors, capacitors, and / or inductors), and / or one or more power sources (such as voltage and / or current power supplies) may instead contain only the semiconductor elements within a single physical device (e.g., a semiconductor die and / or integrated circuit (IC) package), which may be adapted to be coupled to at least some of the passive elements and / or power sources, thereby forming the described structure, for example, by an end user and / or a third party, either at the time of manufacture or at a later point in time.

[0056] While specific transistors are described in this specification, other transistors (or equivalent devices) may be used instead. For example, a p-type metal oxide silicon field-effect transistor ("MOSFET") may be used in place of an n-type MOSFET with little or no modification to the circuit. Other types of transistors (e.g., bipolar junction transistors (BJTs)) may also be used.

[0057] The circuits described herein are reconfigurable to include additional or different components to provide functionality that is at least partially similar to the functionality available before component replacement. Components shown as resistors generally represent any one or more elements connected in series or parallel to provide the amount of impedance represented by the illustrated resistors, unless otherwise specified. A resistor or capacitor illustrated and described in the specification as a single component may instead be multiple resistors or capacitors, each connected in series between the same two nodes as a single resistor or capacitor.

[0058] Modifications to the described embodiments are permitted within the scope of the claims, and other embodiments are possible.

Claims

1. 1. A transceiver circuit comprising: a transmitter, an IQ mismatch (IQMM) correction circuit; a power amplifier having an input coupled to the IQMM correction circuit and an output; the transmitter including: a receiver coupled to an output of the power amplifier, a switch network coupled to an output of the power amplifier, the switch network having a first input, a second input, a first output, and a second output; a first switch coupled between the first input and the first output; a second switch coupled between the first input and the second output; a third switch coupled between the second input and the second output; a fourth switch coupled between the second input and the first output; the switch network, a mixer coupled to the first output and the second output of the switch network; an IQMM estimation circuit coupled to the mixer and the IQMM correction circuit; the receiver including: a transceiver circuit comprising:

2. 2. The transceiver circuit of claim 1, The first switch, the second switch, the third switch, and the fourth switch are to perform symmetric down-conversion, the first switch is closed, the second switch is open, the third switch is closed, and the fourth switch is open; to perform asymmetric down-conversion, the first switch is open, the second switch is closed, the third switch is open, and the fourth switch is closed. The transceiver circuit is coupled as follows:

3. 3. The transceiver circuit of claim 2, The transceiver circuit, wherein the IQMM estimation circuit is configured to calculate first IQMM estimates for the transmitter and the receiver based on the symmetric downconversion.

4. 4. The transceiver circuit of claim 3, The transceiver circuit, wherein the IQMM estimation circuit is further configured to calculate second IQMM estimates for the transmitter and the receiver based on the asymmetric downconversion.

5. 5. The transceiver circuit of claim 4, The transceiver circuit, wherein the IQMM estimation circuit is further configured to calculate a transmitter IQMM estimate based on the first IQMM estimate and the second IQMM estimate.

6. 6. A transceiver circuit according to claim 5, The transceiver circuit, wherein the IQMM correction circuit is further configured to modify a signal to be transmitted based on the transmitter IQMM estimate.

7. The transceiver circuit of claim 1, The transceiver circuit, wherein the transmitter is configured to transmit orthogonal frequency division multiplexing (OFDM) packets.

8. The transceiver circuit of claim 1, The transceiver circuit, wherein the receiver further includes an analog-to-digital converter coupled between the mixer and the IQMM estimation circuit.

9. The transceiver circuit of claim 8, The transceiver circuit, wherein the receiver further includes a baseband filter coupled between the mixer and the analog-to-digital converter.

10. The transceiver circuit of claim 1, the transmitter further includes a guard interval window circuit having an output; The transceiver circuit, wherein the IQMM correction circuit has an input coupled to an output of the guard interval window circuit.

11. The transceiver circuit of claim 10, The transceiver circuit, wherein the IQMM estimation circuit has an input coupled to an output of the guard interval window circuit.

12. The transceiver circuit of claim 1, The transceiver circuit, wherein the transmitter further includes a digital-to-analog converter coupled between the IQMM correction circuit and the power amplifier.

13. A transceiver circuit comprising: a transmitter, an IQ mismatch (IQMM) correction circuit having an input and an output; a digital-to-analog converter having an input coupled to the output of the IQMM correction circuit and an output; a power amplifier having an input coupled to the output of the digital-to-analog converter and an output; the transmitter including: a combiner having an input coupled to the output of the power amplifier and an output; a receiver coupled to the output of the combiner, a switch network coupled to the output of the combiner, the switch network having a first input, a second input, a first output, and a second output; a first switch coupled between the first input and the first output; a second switch coupled between the first input and the second output; a third switch coupled between the second input and the second output; a fourth switch coupled between the second input and the first output; the switch network, a mixer coupled to the first output and the second output of the switch network, the mixer having an output; an analog-to-digital converter (ADC) having an input coupled to the output of the mixer and an output; an IQMM estimation circuit having an input coupled to an output of the ADC and an output coupled to an input of the IQMM correction circuit; the receiver including: a transceiver circuit comprising:

14. The transceiver circuit of claim 13, The transceiver circuit, wherein the receiver further includes a baseband filter having an input coupled to the output of the mixer and an output coupled to the input of the ADC.

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