Radio frequency amplifier with fast envelope tracking

Description

Improving the efficiency, consumption, dissipation and/or linearity of radio-frequency (RF) solid state power amplifiers (SSPAs) is a high priority for manufacturers of ground mobile telephony network infrastructures due to the very demanding requirements for 3G-UMTS.  The very high linearity required dramatically impacts the efficiency of power amplifiers used in base stations.  Similar requirements arise in in space applications.

Linearity and energetic efficiency are seen as contradictory requirements and therefore the “flexible amplifier” concept consists in adjusting the power supply to the average RF power in order to achieve both high linearity and high efficiency.  “Envelope tracking” is an evolution of this approach, wherein the power supply is dynamically adjusted, following the RF signal envelope.

The invention solves the problems of existing SoA through a device consisting of a radio-frequency power amplifier with envelope tracking, comprising:

• A power RF amplifying device
• A fast DC/DC converter for envelope tracking using two RF power transistors for implementing both the switching element and rectifier.
• An optional low-pass filter for reducing the bandwidth of the envelope signal on which the PWM signal driving the DC/DC converter depends.

As an advantage, the switching device, the rectifying device and the power RF amplifier can be identical transistors.

An RF power transistor connected as a rectifier enables a high commutation speed to be achieved, whilst dealing with comparatively high currents (>1A) and powers (several Watts).  This is not possible using commercial diodes and therefore a transistor connected as a two terminal device avoids “diode bottlenecks” seen with current technology.

Innovations and advantages

The technology offers better efficiency, wider bandwidth, better integration, better linearity and power flexibility. Monolithic integration of the envelope tracking circuit and the main RF power amplifier is possible. A single power supply to the envelope tracking circuit is sufficient.

Commercialisation aspects

Applications and Markets

This power amplifier may be used in any field where a modulated signal (most efficient case) is used. 

Examples include:

• General telecom applications (L, S, C band) such as telephony, radio, TV or radio links
• GNSS communications
• Ground applications that use an SSPA transmitting device (e.g. SAR imaging)
• Radar
• Sensors (ultrasonic, infrared or laser) which use a modulated signal for increasing their range.