Capacitor Array Servo Loop for Constant RC and Low Power Loss
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Solution Overview
Problem
Variable capacitor arrays in short-range wireless applications face challenges with non-zero switch resistance leading to power loss and reduced tuning range due to parasitic capacitance and temperature dependence, which affects the efficiency and control of transmitted power.
Innovation Solution
A method and apparatus that adjust the gate voltage of transistors within the capacitor array to maintain constant impedance by comparing the resistance of replica devices to a desired value, using a control voltage circuit to compensate for variations in temperature and supply voltage, thereby reducing parasitic capacitance and maintaining a consistent RC product.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If switch resistance is reduced by increasing the size of switch, then power loss is reduced, but the area of the capacitor array becomes excessively large
Solution Approach 1:
The patent changes the electrical parameters (gate voltage) of the switch devices dynamically to compensate for resistance variations. By adjusting the gate voltage based on temperature and supply voltage conditions, the system maintains constant switch resistance without requiring larger physical switch devices, thus avoiding increased capacitor array area while reducing power loss.
2Reliability
If switch resistance is reduced by increasing the size of switch, then transmitted power control is improved, but the parasitic capacitance increases causing degraded off-to-on capacitance ratio
Solution Approach 1:
The patent dynamically adjusts the gate voltage parameter to compensate for changes in switch resistance due to temperature and supply voltage variations. This maintains constant switch resistance and improves transmitted power control without increasing switch size, thereby avoiding increased parasitic capacitance and maintaining a high off-to-on capacitance ratio.
3Reliability
If gate voltage is adjusted to compensate for temperature and supply voltage variations, then switch resistance is maintained constant, but device complexity increases
Solution Approach 1:
The patent employs feedback mechanisms where the gate voltage is dynamically adjusted based on detected temperature and supply voltage conditions. The control circuit monitors these parameters and modifies the gate voltage accordingly to maintain constant switch resistance, achieving high reliability through closed-loop control.
Solution Approach 2:
The control voltage circuit performs multiple functions: it compensates for temperature variations, compensates for supply voltage variations, and maintains constant switch resistance. By combining these functions into a single circuit block, the patent reduces overall device complexity compared to having separate circuits for each compensation function.
4Adaptability or versatility
If multiple capacitive elements are switched to achieve variable capacitance, then tuning range is improved, but power loss increases due to non-zero switch resistance
Solution Approach 1:
The patent maintains constant switch resistance by dynamically adjusting the gate voltage parameter in response to temperature and supply voltage changes. This allows the capacitor array to achieve its full tuning range through switching multiple capacitive elements without suffering from increased power loss due to resistance variations.
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 ensures a more stable and efficient transmission of power by maintaining constant switch resistance, reducing power loss and increasing the tuning range of the capacitor array, especially in battery-operated systems where voltage variations are significant.
Implementation Method 1
the switch resistance, and therefore the amount of the power loss, depends on processing, temperature, and switching voltage
Implementation Method 2
supplying one or more transistors within the unit element a gate voltage that adjusts to compensate for variations in at least one of supply voltage and temperature
Implementation Method 3
The control voltage circuit comprises a compare circuit to compare resistance of one or more replica devices corresponding to the one or more transistors to a desired value
Implementation Method 4
a capacitor array that includes a plurality of unit elements. Each unit element includes at least one capacitor
Data Source
AI summary
The impedance of the elements of a capacitor array in the transmitter is kept substantially constant over changes in process, temperature, and supply voltage. The impedance is maintained substantially constant by compensating a gate voltage supplied to switches in each element of the capacitor array to adjust for changes in temperature and supply voltage to thereby maintain a substantially constant RC product for each unit element in the capacitor array and thereby improve the quality factor of the capacitor array.