Programmable LO Delay for PA-to-VCO Coupling Mitigation
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Solution Overview
Problem
Interference caused by power amplifier harmonic coupling into a voltage-controlled oscillator in transmitters leads to modulation errors, stability issues, and phase noise degradation, which existing solutions fail to adequately mitigate without increasing current consumption, silicon area, or introducing additional costs.
Innovation Solution
A programmable delay circuit is introduced between the power amplifier and the voltage-controlled oscillator, which adjusts the delay based on the oscillating signal period, frequency, and temperature to reduce control voltage changes and phase noise degradation, using a delay controller that combines calibration and temperature offsets to determine optimal delay settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frequency separation between PA and VCO is increased to mitigate coupling interference, then interference is reduced, but current consumption in VCO and LO chain increases
Solution Approach 1:
The patent changes the timing parameter (delay) of the LO signal to alter the phase relationship between PA and VCO. By adjusting the delay value, the coupling interference is mitigated without changing the frequency separation, thus avoiding increased current consumption while still reducing harmful coupling effects
Solution Approach 2:
The patent introduces a dynamic delay adjustment mechanism that adapts the LO signal timing based on operating conditions. The delay value can be programmatically adjusted to optimize performance across different frequencies and temperatures, providing dynamic mitigation of coupling interference without static frequency separation
2Object-affected harmful factors
If PA output power is reduced to mitigate coupling, then interference is reduced, but additional external front-end module is required increasing cost and board area
Solution Approach 1:
The patent changes the timing parameter (delay) of the LO signal to alter the phase relationship between PA and VCO. By adjusting the delay value, the coupling interference is mitigated without changing the PA output power, thus avoiding the need for external front-end modules and their associated cost and board area penalties
3Object-affected harmful factors
If wide-band synthesizer is employed to mitigate coupling, then interference is reduced, but undesired emissions increase due to higher phase noise
Solution Approach 1:
The patent changes the timing parameter (delay) of the LO signal to alter the phase relationship between PA and VCO. This approach mitigates coupling interference while maintaining the narrow-band synthesizer configuration, thereby avoiding the increased phase noise and undesired emissions that would result from using a wide-band synthesizer
4Object-affected harmful factors
If magnetically differential inductors are used in VCO to mitigate coupling, then interference is reduced, but silicon area consumption increases significantly
Solution Approach 1:
The patent changes the timing parameter (delay) of the LO signal to alter the phase relationship between PA and VCO. This software-based mitigation approach avoids the need for additional magnetic shielding components, thus preventing significant increases in silicon area consumption while still effectively reducing coupling interference
5Object-affected harmful factors
If PA and VCO sections are spatially separated to minimize coupling, then interference is reduced, but spatial separation is not feasible in advanced semiconductor fabrication technologies
Solution Approach 1:
The patent changes the timing parameter (delay) of the LO signal to alter the phase relationship between PA and VCO. This approach mitigates coupling interference through parameter adjustment rather than physical separation, making it fully compatible with advanced semiconductor fabrication technologies that require compact integration and do not permit increased spatial separation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively mitigates interference from power amplifier to voltage-controlled oscillator coupling, reducing phase noise and control voltage changes without affecting output power or efficiency, thus improving transmitter stability and emissions compliance.
Implementation Method 1
a voltage-controlled oscillator that provides an oscillating signal
Implementation Method 2
a power amplifier that is configured to use the delayed oscillating signal for transmitting a signal
Data Source
AI summary
A transmitter including a frequency synthesizer with a voltage-controlled oscillator that provides an oscillating signal, a programmable delay circuit that delays the oscillating signal to provide a delayed oscillating signal, a power amplifier that is configured to use the delayed oscillating signal for transmitting a signal, and a delay controller that programs the delay circuit with a delay time that reduces interference caused by coupling from the power amplifier to the voltage-controlled oscillator. The delay circuit may be programmed to reduce control voltage change of the voltage-controlled oscillator as a function of delay change, and/or to reduce phase noise degradation at an output of the transmitter as a function of delay change. The delay may be adjusted based on detected operating temperature. A calibration value may be determined at a calibration frequency, in which a frequency offset may be determined based on a selected channel frequency.