Ultra-Wideband VCO Tuning Sensitivity for Temperature-Stable Bands
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Solution Overview
Problem
Temperature-induced band switching in ultra-wide band voltage-controlled oscillators (VCOs) leads to significant flickering in received signals and reduced tuning sensitivity, which is not effectively addressed by existing methods.
Innovation Solution
A method and circuit that adjust tuning sensitivity using a digitally controlled variable current source, a variable transconductance circuit, and a control circuit to compensate for frequency variations, with programmable varactor circuits and a capacitor switch array to maintain frequency stability across temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the entire frequency range is divided into smaller bands to reduce spurs, then spur reduction is achieved, but band-switching occurs when temperature changes causing flickering
Solution Approach 1:
The patent implements a dynamically adjustable tuning sensitivity (KVCO) that can be programmed to different values to accommodate temperature-induced frequency variations. The VCO system transitions from a fixed KVCO to a programmable KVCO that adapts to temperature changes, preventing band-switching while maintaining the divided frequency band structure for spur reduction.
Solution Approach 2:
The patent changes the KVCO parameter from a fixed value to a programmable value that can be adjusted based on temperature conditions. By modifying the tuning sensitivity parameter, the system compensates for temperature-induced frequency drift without requiring band-switching, thus eliminating flickering while preserving the spur-reduction benefits of frequency division.
2Object-generated harmful factors
If KVCO is decreased to reduce spurs, then spur levels are reduced, but band-switching-induced screen flickering increases
Solution Approach 1:
The system employs a programmable KVCO that can be dynamically adjusted to optimal values based on operating conditions. Instead of using a uniformly low KVCO that causes flickering, the system can program higher KVCO values when appropriate to maintain frequency stability across temperature ranges, thereby eliminating flickering while still achieving spur reduction through frequency band division.
Solution Approach 2:
The patent optimizes the KVCO parameter by making it programmable rather than fixed. This allows the system to select the minimum KVCO value needed to prevent band-switching at each temperature condition, rather than using a conservatively low KVCO that causes flickering. The parameter is tuned to achieve the lowest possible spur levels without inducing flickering.
3Object-generated harmful factors
If frequency bands are made narrow to reduce spurs, then spur reduction is achieved, but temperature changes require band-switching causing instability
Solution Approach 1:
The patent implements a programmable KVCO that allows the system to maintain narrow frequency bands for spur reduction while dynamically adjusting the tuning sensitivity to compensate for temperature-induced frequency variations. This dynamic adjustment prevents the need for band-switching, maintaining both the spur-reduction benefits and frequency band stability across temperature changes.
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
This approach reduces or eliminates temperature-induced band-switching, ensuring stable signal reception and reducing reference spurs and power supply ripple spurs, thereby enhancing synthesizer loop stability and production yields across various temperature and voltage conditions.
Implementation Method 1
The variable transconductance circuit may be programmable by selectively activating elements of an array of varactor circuits, according to a capacitance associated with each varactor circuit
Implementation Method 2
a voltage-controlled oscillator (VCO) provides a signal which frequency varies according to a control signal applied at the VCO's input terminal
Data Source
AI summary
A method and a voltage-controlled oscillator provide an output signal with a frequency within one of a plurality of frequency bands, while reducing or eliminating temperature-induced band-switching or other drifts in operating frequency. The band-switching is reduced or eliminated by providing a circuit that adjusts a tuning sensitivity according to a calibration performed under test conditions. For example, such a voltage-controlled oscillator may include (a) a digitally controlled variable current source for providing a first control current to select one of the frequency bands for the voltage-controlled oscillator; (b) a variable transconductance circuit providing a second control current to compensate a variation in operating frequency; and (c) a control circuit for varying the frequency of the output signal in accordance with the first and second control signals. The variable transconductance circuit may be programmable by selectively activating elements of an array of varactor circuits, according to a capacitance associated with each varactor circuit. The capacitance associated with each varactor circuit is binary weighted.