Folded MOS Transistor Random Signal Generator for Smart Cards
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Solution Overview
Problem
Existing random binary signal generators for smart cards produce deterministic and repetitive sequences due to finite state machines, and noise-based generators require power-consuming transistors, which are undesirable in integrated circuits.
Innovation Solution
A random signal generator utilizing a folded MOS transistor with a zigzag-shaped channel as an electronic noise source, coupled with a reference transistor and amplification circuit to generate a random binary signal, ensuring equal probability of output bits and integrating within smart card ICs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a state machine with finite internal states is used to generate random binary sequences, then the device complexity is reduced and cost is lowered, but the generated sequences become deterministic and highly repetitive with statistical bias
Solution Approach 1:
The patent replaces the mechanical state machine approach with an electronic noise-based approach using folded MOS transistors. The random component in the drain-source current of the folded transistor serves as the noise source, eliminating the need for complex state machines while providing true randomness through physical noise phenomena.
Solution Approach 2:
The patent changes the operating parameters of the MOS transistor by using a folded configuration with specific channel dimensions at the resolution limit of manufacturing technology. This parameter change transforms the transistor from a deterministic device into one that exhibits significant random current components, thereby generating high-quality random sequences.
2Reliability
If electronic noise sources such as avalanche-connected diodes or biased diodes are used, then high randomness is achieved, but power consumption increases due to the need for high gain amplifiers with bipolar transistors
Solution Approach 1:
The patent substitutes bipolar transistors with MOS transistors in the amplifier stage. MOS transistors have significantly lower power consumption than bipolar transistors while providing the necessary amplification gain. This substitution maintains the randomness quality while dramatically reducing power consumption, making the generator suitable for smart card applications.
Solution Approach 2:
The patent changes the noise generation mechanism from requiring high bias currents (as in avalanche diodes) to utilizing the intrinsic random component in the drain-source current of folded MOS transistors. This parameter change reduces the power consumption while maintaining adequate noise levels for random sequence generation.
3Reliability
If the channel size of folded MOS transistor is reduced to enhance random component, then randomness is improved, but manufacturing precision becomes more difficult to achieve
Solution Approach 1:
The patent converts the manufacturing variability and resolution limits into a benefit. By designing the folded transistor channel dimensions to be at the resolution limit of manufacturing technology, the patent exploits the inherent variability and random effects that occur at these small dimensions. What would normally be considered a manufacturing defect or limitation becomes the source of enhanced randomness in the drain-source current.
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 provides a compact, low-power random signal generator that overcomes the limitations of existing generators by leveraging the random component of the drain-source current in folded MOS transistors, ensuring high randomness and equal bit probabilities, suitable for smart card applications.
Implementation Method 1
the noise generated by an avalanche-connected diode or a biased diode, or also the thermal noise in a resistor
Implementation Method 2
the noise generated by an avalanche-connected diode or a biased diode
Data Source
AI summary
A random signal generator uses a folded MOS transistor, whose drain-source current includes a random component, as an electronic noise source. The random signal generator generates a random binary signal from the random component. The invention may be applied, in particular, to smart cards.