RF Power Amplifier Combining With Isolation Feedback Calibration
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Solution Overview
Problem
Current high output power radio frequency (RF) power amplifier combining techniques face challenges with power amplifier mismatch over time, frequency, and temperature, leading to increased costs and reduced efficiency, particularly in remote radio heads (RRHs) requiring high transmitter output power.
Innovation Solution
A method and system for magnitude and phase adjustment of combined power amplifiers using existing smaller output power PA transistors, employing a hybrid coupler or Wilkinson combiner for calibration, which reduces hardware development time and costs by eliminating the need for transistor binning and allowing for field calibration without requiring new components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If two power amplifiers are combined to increase transmitter output power, then the output power is improved, but the complexity of matching gain and phase over frequency, time and temperature increases
Solution Approach 1:
The patent applies preliminary action by performing calibration of magnitude and phase adjustments before the RRH is deployed in the field. The calibration is done in a controlled environment where temperature and other conditions are stable, allowing pre-determination of correction values that will be stored and applied during operation. This preliminary calibration avoids the need for complex real-time matching mechanisms during field operation.
Solution Approach 2:
The patent uses feedback by measuring the isolation port signal of the hybrid coupler, which contains information about the magnitude and phase mismatch between the two power amplifiers. This isolation signal is fed back to the adjustment circuits, which automatically adjust the magnitude and phase of each amplifier's input signal to minimize the isolation signal, thereby achieving automatic matching.
2Manufacturing precision
If transistor binning is performed to reduce mismatch between amplifiers, then the matching precision is improved, but the cost increases
Solution Approach 1:
The system applies self-service by using the isolation port of the hybrid coupler itself as the feedback source for calibration. No external test equipment or additional sensors are needed - the system uses its own internal signal paths and the natural isolation port output to generate the feedback signal that drives the adjustment circuits during calibration.
Solution Approach 2:
The patent applies parameter changes by adjusting the magnitude and phase parameters of each amplifier's input signal dynamically. Instead of selecting specific transistors during manufacturing (binning), the system changes the operational parameters (magnitude and phase) of each amplifier to achieve optimal matching, thereby avoiding the costs associated with transistor binning while achieving the same matching precision.
3Power
If high power PAs are designed from scratch, then the power output is improved, but the development time increases
Solution Approach 1:
The patent applies merging by combining two existing smaller output power PA transistors to achieve high output power (100W or higher). Instead of designing and developing a new high-power PA transistor from scratch, the system merges the functionality of two already-developed, commercially available lower-power transistors through a hybrid coupler configuration, thereby significantly reducing development time while achieving the required power output.
Solution Approach 2:
The system applies universality by using commercially available PA transistors designed for 80W or lower output power in a multi-functional configuration. These standard transistors serve both as individual amplifiers and, when combined through the hybrid coupler, as components of a high-power (100W+) transmitter system. The same standard transistors can be used across different applications and power requirements.
4Ease of operation
If field calibration is performed without new components, then the ease of operation is improved, but the measurement precision may be compromised
Solution Approach 1:
The patent uses the isolation port of the hybrid coupler as an intermediary element for feedback. The isolation port naturally provides a signal that represents the mismatch between the two amplifiers, and this intermediary signal is used to drive the adjustment circuits during calibration. This approach enables field calibration using existing components without requiring external test equipment, maintaining both ease of operation and adequate precision for field conditions.
Data Source
AI summary
A method and a transmitter providing magnitude and phase adjustment for high output power radio frequency (RF) power amplifier (PA) combining are provided. According to one aspect, a method includes making adjustments to the magnitude and phase of a received signal to produce first and second amplifier input signals. The method also includes amplifying a respective one of the first and second amplifier input signals via respective first and second power amplifiers. The method further includes combining outputs from each of the first and second power amplifiers to produce a first transmit signal, and to produce an isolation signal indicative of an amount by which the outputs from the first and second power amplifiers differ in magnitude and phase. The isolation signal is used to adjust the received signal to drive the isolation signal toward zero.