Frequency Hopping Transmit Path with Multiple Local Oscillators

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Solution Overview

Problem

Conventional transmit paths in LTE communication networks generate spurious signal emissions, particularly when allocating narrow resource blocks, which can interfere with other channels and limit user equipment (UE) coverage due to the need for additional power reduction to comply with 3GPP specifications.

Innovation Solution

The implementation of a frequency hopping uplink transmission method using a control unit and multiple local oscillators (LOs) to dynamically adjust the frequency of the transmit path based on upcoming resource block allocations, selecting an unused LO and tuning it to the corresponding frequency if the allocation differs from the current allocation and the number of allocated resource blocks is below a threshold.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a conventional transmit path with a fixed frequency carrier signal is used, then the system structure is simple, but spurious signal emissions increase and interfere with other channels

Engineering Contradiction:

Improvetransmit path structureVSAvoidspurious signal emissions

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The patent implements frequency hopping by dynamically switching the carrier frequency based on resource block allocations. The transmit path transitions from a fixed frequency system to a dynamic frequency system where the carrier frequency changes according to the allocated RBs, thereby reducing spurious emissions that occur with narrow RB allocations in conventional fixed-frequency systems

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the frequency parameter of the carrier signal dynamically. By adjusting the carrier frequency to match the center frequency of allocated resource blocks and implementing frequency hopping patterns, the system reduces the generation of spurious signals while maintaining compliance with 3GPP spectral emission masks

Inventive Principle:

Principle #35Parameter changes

2Object-generated harmful factors

If additional maximum power reduction (AMPR) parameters are adopted to suppress spurious signal emissions, then spectral compliance is improved, but output power decreases and coverage area is limited

Engineering Contradiction:

Improvespurious signal emissionsVSAvoidoutput power

Core Design Contradiction:

Object-generated harmful factorsVSPower

Solution Approach 1:

The system performs frequency pre-compensation by adjusting the carrier frequency in advance based on predicted resource block allocations. The baseband filter dynamically adjusts its frequency to match upcoming RB allocations before transmission occurs, preventing the generation of spurious emissions at the source rather than requiring post-transmission power reduction

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the conventional approach of suppressing spurious emissions through power reduction (mechanical/electrical control) with a frequency-domain solution. By using frequency hopping and dynamic frequency alignment in the baseband, the system eliminates the need for aggressive AMPR parameters while maintaining both spectral compliance and output power

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If the carrier frequency is fixed at a relatively high frequency, then the transmit path is simple, but frequency conversion to match varying RB allocations generates spurious emissions

Engineering Contradiction:

Improvefrequency conversion mechanismVSAvoidintermodulation products

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

Instead of converting the baseband signal to a fixed high carrier frequency and then adjusting, the patent inverts the approach by using a variable baseband frequency that directly matches the allocated RB center frequency. This eliminates the need for complex frequency conversion and reduces intermodulation products by avoiding large frequency shifts

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS10575279B2Methods and apparatus for a transmit path with frequency hopping phase locked loop

Publication Date: 2020.02.25 QUALCOMM INC

AI summary

An apparatus comprising a transmit path, a plurality of local oscillators and a control unit. The control unit may be configured to: receive an upcoming resource block (RB) allocation; determine whether the upcoming RB allocation is the same as the current RB allocation; in response to determining that the upcoming RB allocation is different than the current RB allocation: select an unused LO of the plurality of LOs; determine whether a number of allocated RBs associated with the upcoming RB allocation is greater than a threshold; and in response to determining that the number of allocated RBs associated with the upcoming RB allocation is not greater than the threshold, tune the selected LO to a frequency corresponding to the upcoming RB allocation.