ASK RF Transmitter Circuit With Pulse-Shaped Data Edges

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Solution Overview

Problem

Existing wireless communication systems face challenges in reducing the bandwidth of RF ASK signals while maintaining efficiency, as high-efficiency class C power amplifiers are non-linear and impractical for bandwidth control, and existing solutions require numerous components and large integrated circuit surface area.

Innovation Solution

A digital amplitude modulation circuit that uses a cascode assembly of two MOS transistors with a digital pulse shaper and a simple digital-to-analog converter to attenuate data transition edges, reducing bandwidth by reprogramming stored waveforms and employing a raised cosine filter, thereby minimizing component count and integrated circuit area.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a Class C power amplifier is used for high efficiency, then energy efficiency is improved, but bandwidth control capability deteriorates

Engineering Contradiction:

Improveenergy efficiencyVSAvoidbandwidth control capability

Core Design Contradiction:

Use of energy by moving objectVSAdaptability or versatility

Solution Approach 1:

The transmitter circuit is divided into separate functional blocks: a pulse shaping unit that processes data signals before modulation, and a Class C power amplifier that efficiently amplifies the modulated RF signals. This segmentation allows the non-linear Class C amplifier to operate at high efficiency while the linear pulse shaping unit handles bandwidth control, resolving the contradiction between efficiency and adaptability.

Inventive Principle:

Principle #1Segmentation

2Object-affected harmful factors

If bandwidth of RF ASK signals is reduced to avoid interference, then interference with neighboring transmitters is reduced, but output power must be reduced

Engineering Contradiction:

Improveinterference with neighboring transmittersVSAvoidoutput power

Core Design Contradiction:

Object-affected harmful factorsVSPower

Solution Approach 1:

The pulse shaping unit performs preliminary action by pre-processing the data signals to limit their bandwidth before modulation. By shaping the data signal spectrum in advance using digital filtering techniques, the system achieves bandwidth reduction without requiring power reduction, as the power amplifier operates on already-bandwidth-limited signals.

Inventive Principle:

Principle #10Preliminary action

3Area of stationary object

If edge attenuation of data signals is applied to reduce bandwidth, then spectral bandwidth is reduced, but signal transition quality may deteriorate

Engineering Contradiction:

Improvespectral bandwidthVSAvoidsignal transition quality

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The pulse shaping unit employs parameter changes by adjusting filtering parameters such as filter order, cutoff frequencies, and roll-off factors to achieve the desired bandwidth reduction while maintaining signal transition quality. These parameter optimizations allow the system to reduce spectral bandwidth without excessive degradation of signal integrity.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP2608401B1Circuit for transmitting ASK RF signals with adaptation of the edges of the data signals

Publication Date: 2019.03.27 EM MICROELECTRONIC-MARIN

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AI summary

The circuit has a power amplifier receiving an oscillating signal from a local oscillator and a data amplitude modulation control signal from a data pulse shaping unit. The data pulse shaping unit includes a pulse shaper (21) for digitally adapting data transition edges on basis of an incoming digital data signal. A digital-analog conversion stage converts the digital data signal that is shaped in the data pulse shaping unit so as to supply the data amplitude modulation control signal to the power amplifier.