RF Transceiver Dual-PA Topology for Low-Power Backoff Efficiency
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Solution Overview
Problem
Current RF transceivers face efficiency reductions at lower output powers and large backoffs, with switches in the receive path experiencing stress and power dissipation, and the low noise amplifier not being adequately protected, leading to inefficiencies and component wear.
Innovation Solution
The RF transceiver design includes a single RF antenna port with separate high and low power transmit paths, each with dedicated switches and capacitors to ground, eliminating switches in series with power amplifiers and minimizing path coupling, thereby improving efficiency across a broader power range and backoff range, including -5 dBm to +5 dBm and up to 20 dB backoffs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a switch is placed in series with the low power amplifier output to enable transmit/receive switching, then path switching is achieved, but the switch experiences high voltage and current stress leading to component wear and power dissipation
Solution Approach 1:
The patent extracts the switch from the series path with the power amplifier output and relocates it to a parallel configuration. The switch now connects the receive path to the antenna port rather than being in series with the transmit path, eliminating direct exposure to high voltage and current swings from the power amplifier.
Solution Approach 2:
The patent introduces a parallel path configuration where the receive path is connected through a switch to the antenna port, mediated by the parallel structure rather than forcing the switch to handle the full power amplifier output directly. This intermediary configuration protects the switch from harmful electrical stress.
2Ease of operation
If a switch is placed in series with the power amplifier to enable path switching, then switching functionality is achieved, but ohmic resistance in the closed switch position causes power dissipation and reduced amplifier efficiency
Solution Approach 1:
The switch is extracted from the main signal path between the power amplifier and antenna, removing the source of ohmic resistance losses. The switch now operates in a parallel configuration where its resistance does not directly impact the power amplifier output efficiency.
3Ease of operation
If the low noise amplifier input is not directly grounded, then receiver functionality is maintained, but the low noise amplifier is exposed to stress from power amplifier signals
Solution Approach 1:
The patent segments the receive path into separate components with dedicated switching control. The low noise amplifier is isolated from direct exposure to transmit signals through the switch configuration, while maintaining its grounding for proper receiver operation. The switch controls access to the antenna port separately from the low noise amplifier grounding.
Solution Approach 2:
The potential stress exposure to the low noise amplifier is extracted through the parallel switch configuration, preventing harmful signals from reaching the sensitive receiver component while maintaining normal receiver functionality through proper grounding paths.
4Device complexity
If a single high power amplifier is used for all transmit powers, then device complexity is reduced, but efficiency deteriorates at lower output powers and large backoffs
Solution Approach 1:
The patent segments the transmit power function into two separate power amplifiers: a high power amplifier for high-power transmit modes and a low power amplifier for low-power transmit modes and receive operations. This segmentation allows each amplifier to operate in its optimal efficiency range, with the low power amplifier handling cases where the high power amplifier would operate at large backoffs.
Solution Approach 2:
The low power amplifier serves multiple functions: it handles low-power transmit modes, receive operations, and acts as a buffer for the high power amplifier during high-power modes. This multi-functionality improves overall system efficiency without significantly increasing complexity, as the same component serves multiple purposes across different operating modes.
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
The present invention concerns a RF transceiver (100) comprising: - a single RF antenna port (20) for a receive path, a first transmit path and a second transmit path - a balun (10) comprising a primary winding (11) and a secondary winding (12), wherein a first terminal of the secondary winding (12) is coupled to the RF antenna port (20), - the receive path, which comprises - a low noise amplifier (LNA), comprising an input terminal coupled to a second terminal of the secondary winding (12), - the first transmit path, which comprises - a high power amplifier (HPA), comprising differential output terminals (3, 4) coupled to the primary winding (11), and - a first and second switches (S1, S2) between each differential output terminal (3; 4) of the high power amplifier (HPA) and the ground potential, - a third capacitor (C1) between the first switch (S1) and the ground potential or between the first switch (S1) and a first differential output terminal (4) of the high power amplifier (HPA), - a fourth capacitor (C2) between the second switch (S2) and the ground potential or between the second switch (S2) and a second differential output terminal (3) of the high power amplifier (HPA), - the second transmit path, which comprises - a low power amplifier (LPA) having an output terminal coupled to the RF antenna port (20), and - a third switch (S3) between the output terminal of the low power amplifier (LPA) and the ground potential