Balanced-Unbalanced Transformer Circuit With LC Phase Compensation
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Solution Overview
Problem
The existing balanced-unbalanced transformer circuits using Ruthroff transmission lines face challenges in achieving wideband frequency operation due to monotonic phase changes with frequency, making it difficult to perform appropriate phase compensation across a wide frequency band.
Innovation Solution
Incorporating a first LC resonant circuit between the balanced and unbalanced nodes, which provides inductive impedance in one frequency band and capacitive impedance in another, allowing for phase compensation in both bands, and using a dual-balanced-unbalanced transformer circuit configuration to amplify RF signals while canceling interference waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a transmission line is used for phase compensation in a balanced-unbalanced transformer circuit, then phase imbalance at a branch point is compensated, but the phase change monotonically increases with frequency making it difficult to achieve wideband operation
Solution Approach 1:
The patent changes the impedance parameter of the compensation element from a fixed value (transmission line) to a frequency-dependent value (LC resonant circuit). The LC resonant circuit provides different impedance characteristics (inductive below resonant frequency, capacitive above resonant frequency) to compensate for phase imbalance across different frequency bands, thereby achieving wideband operation.
2Reliability
If a transmission line is used for phase compensation, then phase imbalance is addressed, but appropriate phase compensation over a wide frequency band cannot be performed
Solution Approach 1:
The compensation element's impedance parameter is changed from a fixed transmission line characteristic to a frequency-dependent LC resonant circuit characteristic. This allows the circuit to provide appropriate phase compensation across a wide frequency band by exploiting the resonant behavior that creates distinct inductive and capacitive impedance regions.
3Power
If dual balanced-unbalanced transformer circuits are used to amplify RF signals, then signal amplification is achieved, but interference waves may be amplified along with the signal
Solution Approach 1:
The patent converts the harmful effect of interference wave amplification into a beneficial filtering effect. By designing the dual balanced-unbalanced transformer circuits with complementary frequency operation (one circuit operates at frequency f, the other at frequency 2f), interference waves at unwanted frequencies are naturally canceled out while desired signals are amplified, thus converting potential harm into benefit.
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 configuration enables wider band operation by compensating phase imbalances in two frequency ranges, effectively transforming unbalanced signals into balanced signals and vice versa, while minimizing the amplification of interference waves.
Implementation Method 1
a first LC resonant circuit connected at least one of between the first balanced node and the unbalanced node, between the second balanced node and the fourth end, and between the first end and the unbalanced node
Implementation Method 2
The first LC resonant circuit has an impedance that is inductive in one of a low frequency band lower than a resonant frequency and a high frequency band higher than the resonant frequency, and that is capacitive in the other
Data Source
AI summary
A main line (transmission line) has a first end and a second end. A sub-line (transmission line) coupled to the main line has a third end and a fourth end. The main line and the sub-line are coupled to each other. A direction of the main line is identical to a direction of the sub-line. An unbalanced node is connected to the first end. The first balanced node is connected to the first end, and the second balanced node is connected to the fourth end. The second end and the third end are connected to a reference potential. A first LC resonant circuit is connected between the first balanced node and the unbalanced node, the second balanced node and the fourth end, or the first end and the unbalanced node.