Pulsed LO Signal Generation for Mixer Harmonic Suppression
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Solution Overview
Problem
In RF transceivers, especially during carrier aggregation, unwanted harmonics generated by mixer circuits cause interference between multiple receiver and transmitter signals, leading to down-conversion of unwanted signal contents and in-band blocker interference, which existing methods fail to adequately mitigate.
Innovation Solution
A local oscillator (LO) signal with a pulse series is generated, featuring gaps during the duty cycle, specifically tailored to suppress targeted harmonics by adjusting the pulse pattern and gap duration, ensuring the mixer operates without content at specific harmonics, thereby preventing harmonic down-mixing of unwanted signals into the receiver's baseband.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional continuous LO signal is used in mixer circuits, then the mixer operates continuously with stable signal conversion, but unwanted harmonics are generated causing interference between multiple receiver and transmitter signals
Solution Approach 1:
The patent applies periodic action by using a pulsed LO signal instead of a continuous signal. The LO signal is enabled only during specific time intervals (when switches are active) and disabled during other intervals, creating a periodic on-off pattern that eliminates harmonics generated during switch transitions while maintaining stable signal conversion during active periods
Solution Approach 2:
The patent segments the continuous LO signal into discrete pulsed intervals that correspond to the switching periods of the mixer circuits. By dividing the signal transmission into separate time segments aligned with switch activation, the system achieves stable conversion during each segment while preventing harmonic generation at segment boundaries
2Object-generated harmful factors
If the duty cycle of the LO signal is reduced to suppress harmonics, then harmonic interference is mitigated, but the conversion gain and signal quality deteriorate
Solution Approach 1:
The patent employs dynamics by adjusting the LO signal parameters (duty cycle, pulse width, timing) dynamically based on the switching state of the mixer circuits. The LO signal is synchronized with the switch activation patterns, providing optimal signal levels during active periods while maintaining low duty cycle overall, thus preserving conversion gain while suppressing harmonics
Solution Approach 2:
The patent applies preliminary action by pre-synchronizing the LO signal pulses with the switch activation timing. The LO signal is prepared and applied just before or during the switch activation period, ensuring optimal signal conversion from the outset while avoiding the generation of harmonics that would occur with continuous signaling
3Productivity
If multiple receivers and transmitters operate simultaneously at different frequencies (carrier aggregation), then data communication rate increases, but interference between signals occurs due to harmonic down-conversion
Solution Approach 1:
The patent applies periodic action by coordinating the LO signal pulsing across multiple receiver and transmitter circuits operating in carrier aggregation mode. Each circuit uses pulsed LO signals synchronized to its respective switch activation patterns, eliminating harmonic generation that would otherwise cause interference between simultaneously operating frequency bands
Solution Approach 2:
The patent extracts and removes the harmful harmonic components by using pulsed LO signals that prevent their generation in the first place. By taking out the continuous signal portions that generate harmonics and retaining only the necessary pulsed portions for signal conversion, the system enables multiple frequency bands to operate simultaneously without inter-band interference
Data Source
Figure 1A~1C
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AI summary
A transceiver includes local oscillator (LO) signal circuitry configured to output an LO signal having an LO frequency and mixer circuitry configured to input the LO signal and an information signal that encodes communication data and output a shifted signal that corresponds to the information signal shifted to a desired frequency. The LO signal circuitry includes selection circuitry and generation circuitry. The selection circuitry is configured to select a pulse pattern and a gap duration based at least on a target harmonic of the LO frequency to be suppressed. The pulse pattern includes at least two pulses spaced apart by a gap having the gap duration. The generation circuitry is configured to generate an LO signal characterized by the selected pulse pattern and gap duration.