DC offset calibration in an interdependent quadrature receiver
In one aspect, an apparatus includes: a low noise amplifier (LNA) to receive and amplify a radio frequency (RF) signal; a mixer coupled to the LNA to downconvert the RF signal to a second frequency signal; a quadrature transimpedance amplifier (TIA) to convert a current of the second frequency signal to a voltage signal, the quadrature TIA having an in-phase (I)-channel having an I-channel DC offset and a quadrature-phase (Q)-channel having a Q-channel DC offset; and a DC offset calibration circuit coupled to the quadrature TIA. The DC offset calibration circuit is configured to calibrate a DC offset of the quadrature TIA. The DC offset calibration circuit may be configured to independently determine an I-channel DC offset setting and independently determine a Q-channel DC offset setting, where the I-channel and Q-channels have a DC offset interdependency.
1 . An apparatus comprising:
a low noise amplifier (LNA) to receive and amplify a radio frequency (RF) signal;
a mixer coupled to the LNA to downconvert the RF signal to a second frequency signal;
a quadrature transimpedance amplifier (TIA) to convert a current of the second frequency signal to a voltage signal, the quadrature TIA having an in-phase (I)-channel having an I-channel DC offset and a quadrature-phase (Q)-channel having a Q-channel DC offset; and
a DC offset calibration circuit coupled to the quadrature TIA, the DC offset calibration circuit to calibrate a DC offset of the quadrature TIA comprising the I-channel DC offset and the Q-channel DC offset, the DC offset calibration circuit to independently determine an I-channel DC offset setting while a Q-channel DC offset setting is held and independently determine the Q-channel DC offset setting while the I-channel DC offset setting is held, wherein the I-channel and the Q-channel of the quadrature TIA have a DC offset interdependency.
2 . The apparatus of claim 1 , wherein the DC offset calibration circuit comprises a sequencer to initiate the DC offset calibration in response to a trigger condition.
3 . The apparatus of claim 2 , wherein the sequencer is to control operation of the DC offset calibration according to a successive approximation.
4 . The apparatus of claim 3 , wherein the sequencer is to cause an initial Q-channel DC offset setting to be provided to the Q-channel and cause the DC offset calibration circuit to determine a first I-channel DC offset setting according to the successive approximation.
5 . The apparatus of claim 4 , wherein the sequencer is to thereafter cause the first I-channel DC offset setting to be provided to the I-channel and cause a determination of a first Q-channel DC offset according to the successive approximation.
6 . The apparatus of claim 5 , wherein the DC offset calibration circuit is to iteratively determine the first I-channel DC offset setting and the first Q-channel DC offset setting, until a convergence is detected.
7 . The apparatus of claim 6 , wherein the DC offset calibration circuit is to determine the convergence when a successive I-channel DC offset is within at least a threshold of the first I-channel DC offset.
8 . The apparatus of claim 4 , wherein the DC offset calibration circuit is to perform the DC offset calibration during a factory test and store a seed I-channel DC offset setting and a seed Q-channel DC offset setting in a non-volatile storage.
9 . The apparatus of claim 8 , wherein the DC offset calibration circuit is to provide the seed Q-channel DC offset setting as the initial Q-channel DC offset setting.
10 . A method comprising:
initiating a DC offset calibration for a quadrature differential amplifier having a first channel and a second channel, the first channel and the second channel having DC offset interdependency;
iteratively, until a convergence is detected, calibrating at least one of:
the second channel to determine a DC offset setting for the second channel while a DC offset setting for the first channel is held; and
the first channel to determine the DC offset setting for the first channel while the DC offset setting for the second channel is held;
storing a converged DC offset setting for the first channel in a first storage;
storing a converged DC offset setting for the second channel in a second storage; and
providing the converged DC offset setting for the first channel and the converged DC offset setting for the second channel to the quadrature differential amplifier to provide DC offset compensation.
11 . The method of claim 10 , further comprising detecting the convergence for the second channel when a successive DC offset setting for the second channel equals a preceding DC offset setting for the second channel.
12 . The method of claim 10 , further comprising detecting the convergence for the second channel when a successive DC offset setting for the second channel is within a threshold of a preceding DC offset setting for the second channel.
13 . The method of claim 10 , wherein initiating the DC offset calibration comprises providing an initial DC offset setting for the first channel.
14 . The method of claim 13 , wherein providing the initial DC offset setting for the first channel comprises providing a seed DC offset setting for the first channel, the seed DC offset setting for the first channel obtained from a non-volatile storage.
15 . The method of claim 10 , further comprising providing the converged DC offset setting for the first channel and the converged DC offset setting for the second channel to at least one digital-to-analog converter (DAC), the at least one DAC to output therefrom a DC offset compensation for the first channel and a DC offset compensation for the second channel.
16 . The method of claim 10 , further comprising, if the convergence is not detected, iteratively calibrating the second channel and the first channel for a predetermined number of iterations.
17 . A system comprising:
an antenna to receive a radio frequency (RF) signal;
a low noise amplifier (LNA) coupled to the antenna to amplify the RF signal;
a mixer coupled to the LNA to down convert the RF signal to a second frequency signal;
a quadrature differential amplifier to amplify the second frequency signal and output a quadrature differential signal, the quadrature differential amplifier having an in-phase (I)-channel having an I-channel DC offset and a quadrature-phase (Q)-channel having a Q-channel DC offset, wherein the I-channel and the Q-channel have DC offset interdependency;
a DC offset calibration circuit coupled to the quadrature differential amplifier, the DC offset calibration circuit to independently determine, based at least in part on a seed value for at least one of the I-channel or the Q-channel, an I-channel DC offset setting and a Q-channel DC offset setting, to compensate for the I-channel DC offset and the Q-channel DC offset, wherein the DC offset calibration circuit is to:
calibrate the I-channel to determine the I-channel DC offset setting while the seed value for the Q-channel is held; and
calibrate the Q-channel to determine the Q-channel DC offset setting while the I-channel DC offset setting is held;
a peak detector coupled to the quadrature differential amplifier to detect a peak signal from the quadrature differential signal; and
a non-volatile memory to store the seed value for the at least one of the I-channel or the Q-channel.
18 . The system of claim 17 , wherein the DC offset calibration circuit is to iteratively calibrate the I-channel and the Q-channel until a convergence is detected.
19 . The system of claim 17 , further comprising a digital-to-analog converter (DAC) to receive the I-channel DC offset setting and the Q-channel DC offset setting and output, based thereon, an I-channel DC offset compensation value and a Q-channel DC offset compensation value.