Variable Admittance Circuit Switching to Minimize RF Glitches
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Solution Overview
Problem
Existing variable admittance circuits for programmable filters and amplifiers face accuracy issues due to cumulative tolerances and switching noise, requiring large silicon areas and precise component matching, and are prone to glitches during transitions.
Innovation Solution
A variable admittance circuit with a geometric sequence of switchable elements, reducing the number of branches and silicon area required, by using a fixed admittance element and at least three switchable elements with specific admittance values, and a controller to minimize switching noise and component changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If binary weighted admittance elements are used to minimize the number of branches, then the device complexity is reduced, but the manufacturing precision deteriorates due to cumulative tolerances and the need for careful component matching
Solution Approach 1:
The patent changes the admittance value parameters from traditional binary weighting to a modified geometric sequence where Y(i) = K*(Y(i-1) + Y(i-2)) with K in the range 0.8 to 1.05. This parameter modification allows the circuit to maintain fewer branches while reducing the sensitivity to component tolerance variations, as the new weighting scheme distributes the tolerance impact more evenly across transitions.
Solution Approach 2:
The patent introduces dynamic switching sequences that transition through intermediate states rather than direct binary jumps. By using a controller to manage the switching of admittance elements in a controlled sequence, the system dynamically avoids large simultaneous changes, thereby reducing glitches and tolerance accumulation while maintaining the reduced branch structure.
2Speed
If multiple switchable admittance elements are changed in a single transition to achieve fast switching, then the speed is improved, but harmful factors increase due to large glitches and transients that disturb circuit operation
Solution Approach 1:
The patent implements preliminary action by pre-planning and controlling the switching sequence of admittance elements. The controller manages transitions to occur in a predetermined sequence rather than simultaneously, preparing the circuit state in advance to avoid large transient changes. This staged switching approach maintains fast overall switching while minimizing harmful glitches during the transition process.
3Manufacturing precision
If component tolerances are reduced to improve accuracy of step changes, then the manufacturing precision is improved, but the area increases due to larger component sizes required for precise matching
Solution Approach 1:
The patent modifies the admittance parameter relationships from strict binary weighting to a geometric sequence with ratio K*(Y(i-1) + Y(i-2)) where K is between 0.8 and 1.05. This parameter change makes the system less sensitive to individual component tolerances, achieving acceptable step change accuracy with standard tolerance components, thereby avoiding the need for larger precision components that would increase silicon area.
Data Source
AI summary
A programmable variable admittance circuit may be used in a programmable filter or a variable gain amplifier in a number of different applications including tuners and other RF receiver circuits. A variable admittance circuit and operation is described including a number of switchable admittance elements arranged in parallel branches. The variable admittance circuit requires fewer transitions to change between successive admittance values than a binary weighted circuit and fewer branches for implementation then a thermometry admittance circuit.