Separate TDD RF Filters for Carrier Aggregation

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Solution Overview

Problem

Current RF circuit designs for carrier aggregation face challenges in optimizing impedance matching, interference rejection, and insertion loss, particularly in inter-band carrier aggregation, leading to increased complexity and footprint due to the need for integrated receive-transmit filters that must suppress harmonics and intermodulation products across multiple frequency bands.

Innovation Solution

The implementation of separate time-division duplex (TDD) receive and transmit filters, which are functionally independent, allows for improved impedance matching, interference rejection, and reduced insertion loss without increasing the RF circuit's footprint by directly connecting the TDD receive filter to the LNA and separating it from the TDD transmit filter.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If integrated receive-transmit filters are used to support multiple frequency bands, then band support capability is improved, but device complexity and footprint increase

Engineering Contradiction:

Improveband support capabilityVSAvoidcircuit complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent divides the integrated receive-transmit filter into separate receive filter and transmit filter components. Each filter is independently optimized for its specific function, allowing simpler individual filter designs while maintaining overall multi-band support capability through selective switching between filters.

Inventive Principle:

Principle #1Segmentation

2Object-affected harmful factors

If integrated receive-transmit filters are used to suppress harmonics and intermodulation products, then interference rejection is improved, but device footprint increases

Engineering Contradiction:

Improveinterference rejectionVSAvoidcircuit footprint

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

The patent separates the receive and transmit filter functions into distinct components, each optimized for specific interference suppression requirements. The receive filter handles downlink interference while the transmit filter handles uplink interference, reducing the total footprint compared to a single integrated filter attempting to handle all interference types.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each filter is designed with specific characteristics optimized for its particular function - the receive filter is optimized for receiving signals with specific interference rejection properties, while the transmit filter is optimized for transmitting signals with different interference rejection requirements. This localized optimization reduces overall circuit footprint.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If integrated receive-transmit filters are used, then multi-band filtering is achieved, but impedance matching deteriorates

Engineering Contradiction:

Improvemulti-band filteringVSAvoidimpedance matching

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

By separating the receive and transmit filters into independent components, each filter can be independently impedance-matched to its respective circuit stage (receiver or transmitter). This eliminates the impedance matching compromises that would be required in an integrated filter design.

Inventive Principle:

Principle #1Segmentation

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 results in a 1 dB reduction in insertion loss and improved noise figure performance, enhancing the efficiency and linearity of the RF circuit by reducing the burden on individual filters and allowing for better impedance matching to desired power amplifier and LNA impedances.

Implementation Method 1

The TDD receive filter is configured to receive a TDD RF receive signal in a TDD band and pass the TDD RF receive signal to the TDD band LNA

Methodology Applied

Scientific EffectFilter (electronic): Filter (electronic)

Implementation Method 2

The TDD transmit filter is configured to receive a TDD RF transmit signal in the TDD band from the high-band PA and pass the TDD RF transmit signal to a front-end circuit

Methodology Applied

Scientific EffectFilter (electronic): Filter (electronic)

Implementation Method 3

TDD band low-noise amplifier (LNA)

Methodology Applied

Scientific EffectLow-noise amplification:

Implementation Method 4

high-band power amplifier (PA)

Methodology Applied

Scientific EffectPower amplification:

Data Source

PatentUS11121736B2Radio frequency circuit supporting carrier aggregation

Publication Date: 2021.09.14 QORVO US INC

AI summary

A radio frequency (RF) circuit is provided. The RF circuit may include a variety of RF filters organized into a number of filter banks and configured to support carrier aggregation (CA) in a variety of band combinations. In examples discussed herein, the RF circuit is configured to utilize separate receive and transmit filters for filtering an RF receive signal and an RF transmit signal in a time-division duplex (TDD) band, respectively. By employing separate receive and transmit filters for the TDD band, as opposed to using an integrated receive-transmit filter, it may be possible to implement the receive and transmit filters in the RF circuit with improved impedance matching, interference rejection, and insertion loss without increasing a footprint of the RF circuit.