Mixer Current Control Circuit for LO Suppression and Signal Balance
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Solution Overview
Problem
Mixing stages in communication systems face challenges in achieving high signal quality due to imbalances in semiconductor devices and signal fluctuations, leading to increased complexity and cost in balancing circuitry to suppress carrier and local oscillator frequencies.
Innovation Solution
A current control circuit is coupled to a common node between the input of a modulation stage and a current generation circuit, superimposing an offset current to balance the signal, reducing the complexity of the current control circuit and allowing for efficient suppression of local oscillator frequencies without additional balancing circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional balancing circuitry is used to counterbalance imbalances in semiconductor devices and signal fluctuations, then signal quality and suppression of carrier/local oscillator frequencies is improved, but device complexity and production cost increase
Solution Approach 1:
The patent extracts the balancing function from complex additional circuitry and implements it through a simplified current control circuit that directly controls the tail current source. This removes unnecessary circuit elements while retaining the essential balancing capability, thereby reducing device complexity while maintaining signal quality.
Solution Approach 2:
The current control circuit serves multiple functions: it provides the tail current to the mixing stage, enables balancing through offset current injection, and suppresses carrier and local oscillator frequencies. By consolidating these functions into a single circuit block, the patent reduces overall device complexity while maintaining comprehensive signal quality control.
2Manufacturing precision
If additional balancing circuitry is used to counterbalance imbalances with high accuracy, then signal quality is improved, but production cost and area increase
Solution Approach 1:
The patent changes the control parameter from complex circuit configurations to simple current offset values that can be digitally adjusted. The current control circuit responds to control signals that adjust the tail current, enabling high-precision balancing through parameter tuning rather than through complex circuit architecture, thereby reducing manufacturing cost and area.
Solution Approach 2:
The patent discards complex analog balancing circuitry and recovers the balancing function through a simplified digital-controlled current source. This approach eliminates unnecessary circuit elements that increase area and cost while maintaining or improving balancing accuracy through digital control mechanisms.
3Device complexity
If a current control circuit superimposes offset current at common nodes, then device complexity is reduced, but current control precision may be affected
Solution Approach 1:
The patent introduces an intermediary current control circuit that acts as a mediator between the digital control signals and the analog tail current. This intermediary circuit precisely converts digital control values into proportional current adjustments, maintaining current control precision while keeping the overall device complexity low through the use of a simple, dedicated control block.
Data Source
AI summary
A mixing stage includes a first modulation stage that receives an input signal from a first common node of the mixing stage, a first local oscillator input that receives a local oscillator signal, and a first modulation signal output adapted to provide a first modulated signal. A second modulation stage of the mixing stage includes a second input that receives a phase inverted representation of the input signal from a second common node of the mixing stage, a second local oscillator input that receives the local oscillator signal, and a second modulation signal output adapted to provide a second modulated signal. A current generation circuit provides a supply current to the first common node and to the second common node. A current control circuit is adapted to superimpose an offset current to the current of at least one node of the first common node and the second common node.