Apparatus and methods for radio transceivers
Apparatus and methods for transceivers are provided herein. In a first aspect, an observation receiver is implemented to detect common-mode local oscillator (LO) leakage while the observation receiver performs other functions. In a second aspect, a transceiver is implemented with an LO leakage compensation circuit that compensates a transmitter for LO leakage using a digital filter, such as a Kalman filter, that combines differential LO leakage observations with common-mode LO leakage observations. In a third aspect, a transmitter includes multiple local loopback paths including a first loopback path after a variable gain amplifier (VGA) and a second loopback path before the VGA.
1 . A transceiver integrated circuit (IC) comprising:
a first transmitter including at least one mixer and a local oscillator (LO), wherein the first transmitter is configured to generate a first radio frequency (RF) transmit signal based on the LO controlling the at least one mixer to provide frequency upconversion; and
an observation receiver configured to receive an observation signal for observing at least the first transmitter, wherein the observation receiver includes an observation data path configured to process the observation signal to detect a transmit power of the first RF transmit signal, and an LO leakage observation circuit configured to generate leakage observation data based on processing data captured from the observation data path, the LO leakage observation circuit including a digital mixer configured to generate frequency-shifted data based on mixing the data captured from the observation data path, and a digital accumulator configured to generate the leakage observation data based on accumulating the frequency-shifted data,
wherein the first transmitter is configured to process the leakage observation data to compensate for a leakage of the LO.
2 . The transceiver IC of claim 1 , wherein the LO leakage observation circuit does not interrupt the observation data path from detecting the transmit power.
3 . The transceiver IC of claim 1 , wherein the observation data path is further configured to process the observation signal to perform digital pre-distortion (DPD), wherein the LO leakage observation circuit does not interrupt the observation data path from performing DPD.
4 . The transceiver IC of claim 1 , wherein the first transmitter is further configured to compensate for the leakage of the LO based on local transmit observation data from one or more local observation paths of the transceiver IC.
5 . The transceiver IC of claim 4 , wherein the first transmitter is configured to detect a differential LO leakage from the local leakage observation data, and a common-mode LO leakage from the leakage observation data from the observation receiver.
6 . The transceiver IC of claim 4 , wherein the first transmitter further includes a variable gain amplifier (VGA) configured to amplify the first RF transmit signal, wherein the one or more local observation paths includes a first local observation path after the VGA and a second local observation path before the VGA.
7 . The transceiver IC of claim 4 , wherein the first transmitter comprises a digital filter configured to process both the local leakage observation data and the leakage observation data from the observation receiver.
8 . The transceiver IC of claim 7 , wherein the digital filter is a Kalman filter.
9 . The transceiver IC of claim 4 , wherein the first transmitter is configured to collect the local leakage observation data and the leakage observation data from the observation receiver in a plurality of batches.
10 . The transceiver IC of claim 9 , wherein the first transmitter is configured to update a value of an LO leakage compensation signal for compensating for the leakage of the LO after receiving a given number of samples of the local leakage observation data and the leakage observation data from the observation receiver.
11 . The transceiver IC of claim 1 , wherein the LO leakage observation circuit further includes a digital oscillator configured to provide a digital clock signal to the digital mixer.
12 . The transceiver IC of claim 1 , further comprising a plurality of transmitters including the first transmitter, wherein the observation signal is configured to observe one of the plurality of transmitters at a given time, and wherein the LO leakage observation circuit is configured to separately track the leakage observation data for each of the plurality of transmitters.
13 . The transceiver IC of claim 1 , wherein the observation data path includes an analog-to-digital converter (ADC) configured to generate a digital observation signal based on the observation signal, and a digital circuit configured to process the digital observation signal.
14 . A transceiver integrated circuit (IC) comprising:
a plurality of transmitters including a first transmitter that includes at least one mixer and a local oscillator (LO), wherein the first transmitter is configured to generate a first radio frequency (RF) transmit signal based on the LO controlling the at least one mixer to provide frequency upconversion; and
an observation receiver configured to receive an observation signal for observing at least the first transmitter, wherein the observation receiver includes an observation data path configured to process the observation signal to detect a transmit power of the first RF transmit signal, and an LO leakage observation circuit configured to generate leakage observation data based on processing data captured from the observation data path, wherein the observation signal is configured to observe one of the plurality of transmitters at a given time, wherein the LO leakage observation circuit is configured to separately track the leakage observation data for each of the plurality of transmitters, and
wherein a selected transmitter for observation of the plurality of transmitters is changeable without interrupting operation of the LO leakage observation circuit.
15 . The transceiver IC of claim 14 , wherein the observation data path is further configured to process the observation signal to perform digital pre-distortion (DPD), wherein the LO leakage observation circuit does not interrupt the observation data path from performing DPD.
16 . The transceiver IC of claim 14 , wherein the first transmitter is further configured to compensate for the leakage of the LO based on local transmit observation data from one or more local observation paths of the transceiver IC.
17 . The transceiver IC of claim 14 , wherein the observation data path includes an analog-to-digital converter (ADC) configured to generate a digital observation signal based on the observation signal, and a digital circuit configured to process the digital observation signal.
18 . A method of compensating for local oscillator (LO) leakage in a transceiver, the method comprising:
generating a first radio frequency (RF) transmit signal using a first transmitter that includes at least one mixer and a local oscillator (LO) that controls the at least one mixer;
generating an observation signal based on a loopback path from the first transmitter to an observation receiver through an RF front end;
processing the observation signal to detect a transmit power of the first RF transmit signal using an observation data path of the observation receiver;
generating leakage observation data based on processing data captured from the observation data path;
processing the leakage observation data to compensate for a leakage of the LO;
compensating for the leakage of the LO based on local transmit observation data from one or more local observation paths that are not through the RF front end; and
merging the local leakage observation data and the leakage observation data from the observation receiver using a digital filter.
19 . The method of claim 18 , wherein the leakage observation data is generated without interrupting detection of the transmit power.
20 . The method of claim 18 , wherein processing the observation signal includes performing digital pre-distortion (DPD) on the first RF transmit signal, wherein the leakage observation data is generated without interrupting DPD.