Active Termination Circuit for Power Transmitter Efficiency
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Solution Overview
Problem
Conventional power transmitter circuits, such as power DACs, RF transmitters, and PAs, face inefficiencies in impedance matching due to high output impedance, leading to power loss and reduced reliability, especially when using passive back-termination methods.
Innovation Solution
Active termination circuits are introduced, utilizing controlled current sources and resistors to minimize the output current drawn, thereby increasing power efficiency and achieving optimal impedance matching, which can be adapted in real-time to optimize power transfer and reduce parasitic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive back-termination is used to achieve impedance matching, then impedance matching is improved, but power efficiency deteriorates (only 25% termination efficiency)
Solution Approach 1:
The patent replaces passive resistive termination with active electronic termination using transistors (MOSFETs or BJTs) configured as current sources. This substitution of mechanical/passive components with active electronic components enables impedance matching while minimizing power consumption, achieving up to 81% termination efficiency compared to 25% with passive methods.
Solution Approach 2:
The active termination circuit uses the signal itself to control the termination impedance. The transistor gates are driven by the differential signal, causing the termination impedance to automatically track and match the characteristic impedance of the transmission line across varying signal conditions, achieving adaptive impedance matching without external control circuits.
2Reliability
If passive back-termination is used, then impedance matching is achieved, but power loss increases due to current division between termination resistor and load
Solution Approach 1:
The patent replaces the passive resistive current divider with active transistor-based current control. The transistors are configured to present a high impedance to the signal while consuming minimal current, eliminating the 6 dB power loss inherent in passive termination where current divides equally between the termination resistor and load.
3Power
If conventional current source output is used, then high output impedance is achieved, but load impedance matching deteriorates
Solution Approach 1:
The patent transforms the static high output impedance of conventional current sources into a dynamic adaptive termination system. The transistor output impedances are modulated by the differential signal to dynamically track and match the transmission line characteristic impedance, enabling both high output drive capability and precise impedance matching simultaneously.
Data Source
AI summary
Embodiments of the present invention, as further described below, provide active termination circuits that can be used with power transmitter circuits. Embodiments reduce power loss due to impedance matching and increase power efficiency in power transmitter circuits. In particular, embodiments provide active termination circuits that can be configured to draw minimal amounts of the output current generated by the power transmitter circuits. At the same time, embodiments achieve optimal impedance matching, thus enabling optimal power transfer to the load. Further, embodiments can be controlled adaptively in real time to reduce parasitic effects on power transfer and to optimize impedance matching. Embodiments can be implemented using various transistor technologies (e.g., MOSFET, BJT, etc.), and can be used with a variety of power transmitter circuits, including, for example, power DACs, analog/digital RF transmitters, and analog/digital PAs.