Programmable LO Delay for PA-VCO Coupling Interference
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Solution Overview
Problem
The interference caused by power amplifier (PA) harmonic coupling into a voltage-controlled oscillator (VCO) in communication devices leads to modulation errors, stability issues, and phase noise degradation, which are not effectively addressed by existing solutions that increase current consumption, require additional components, or are not feasible in advanced semiconductor technologies.
Innovation Solution
A transmitter circuit with a programmable delay circuit and delay controller that adjusts the delay between the VCO and PA to mitigate interference by moving the coupling away from zero-crossing regions, using digital calibration and temperature compensation to minimize phase noise and control voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frequency separation between PA and VCO is increased to reduce 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 minimized without changing frequency separation, thereby avoiding increased current consumption while still reducing harmful coupling effects.
2Object-affected harmful factors
If output power from on-chip PA is reduced to minimize coupling, then interference is reduced, but additional external components are required increasing cost and area
Solution Approach 1:
The patent introduces a delay circuit as an intermediary element between the VCO and PA. This mediator adjusts the timing of the LO signal to reduce coupling interference, allowing the on-chip PA to maintain its output power without requiring external components, thus reducing device complexity and area.
3Object-affected harmful factors
If wide-band synthesizer is employed to reduce coupling sensitivity, then interference is reduced, but undesired emissions increase due to higher phase noise
Solution Approach 1:
The patent changes the delay parameter of the LO signal to minimize coupling interference. This approach allows the use of narrow-band synthesizers while still reducing coupling sensitivity, thereby avoiding the phase noise degradation that would result from using wide-band synthesizers.
4Object-affected harmful factors
If magnetically differential inductors are used in VCO to reduce coupling, then interference is reduced, but silicon area consumption increases significantly
Solution Approach 1:
The patent introduces a delay circuit as an intermediary between VCO and PA to reduce coupling interference. This approach achieves interference mitigation without using magnetically differential inductors, thereby avoiding significant silicon area consumption while still protecting the VCO from PA coupling.
5Object-affected harmful factors
If ring-oscillator replaces L-C VCO to reduce coupling susceptibility, then interference is reduced, but phase noise increases
Solution Approach 1:
The patent changes the delay parameter of the LO signal to minimize coupling interference, allowing the continued use of L-C VCOs with their superior phase noise characteristics. This approach reduces coupling susceptibility through timing adjustment rather than replacing the VCO architecture, thereby avoiding phase noise degradation.
6Object-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 technologies
Solution Approach 1:
The patent changes the timing parameter (delay) of the LO signal to reduce coupling interference. This allows PA and VCO to remain spatially close on the chip, maintaining compatibility with advanced semiconductor fabrication technologies while still minimizing coupling effects through temporal separation rather than 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 reduces interference without affecting output power or efficiency, improving transmitter performance by minimizing phase noise and modulation errors across varying temperatures and frequencies.
Implementation Method 1
PA to VCO 'pulling' may occur because of magnetic coupling involving the inductances of the PA and VCO
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 amplify the delayed oscillating signal for transmission sufficient to produce interference, 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.