New Pre-Driver Offers High Linearity, Compression Over Large Bandwidths

With more carriers comes more concerns about bandwidth—something Guerilla RF addresses with its newest power amplifier.

Guerilla RF has announced a new power amplifier that can improve linearity over larger bandwidths. This announcement builds on Guerilla RF’s existing power amplifier portfolio and improves performance and bandwidth.

The GRF5112 is highly linear and accommodates a large fractional bandwidth, allowing designers to simplify RF transmitter designs for modern applications. Image used courtesy of Guerilla RF

As more wireless devices are deployed, designers often need an efficient, linear, and broadband power amplifier. In the case of multicarrier base stations, amplifier linearity and bandwidth can place unwanted restrictions on the RF front-end. Guerilla RF claims its newest power amplifier can help ease these limitations.

Why Is Linearity Important?

A key metric of modern power amplifiers is their linearity, which describes how much of the input signal is amplified at the same frequency. When amplifiers become nonlinear (typically as a result of receiving too much input power), some energy is converted to harmonic or intermodulation frequencies, which can greatly impact a transmitter's final performance.

If, for example, a signal with multiple subcarriers is sent to the input of a power amplifier with poor linearity, intermodulation can create leakage between adjacent carriers, potentially impacting the receiver’s ability to decode the signal. As a result, several metrics, including P1dB, OIP3, and adjacent channel leakage ratio (ACLR), are used to quantify an amplifier's linearity.

With multicarrier systems, nonlinearity in amplifiers can create considerable distortion and make decoding the RF signal difficult. As such, designers work to ensure that the linearity of power amplifiers is as high as possible. Image used courtesy of Analog Devices

The GRF5112's linearity makes it sufficient for a variety of transmitter designs. With 20 dBm of output power, the GRF5112 offers a reported > 45 dBc ACLR, ensuring that transmitters using the power amplifier do not suffer from distortion in multi-carrier designs. Guerilla RF further reports an output P1dB compression point of 32.2 dBm and an OIP3 of 40 dBm at 18 dBm of output power per tone.

Improvements Over Previous Generations

Guerilla RF also cites the power amplifier's generational improvements over the GRF5115 core. The company says the new device provides an overall better experience for designers thanks to the streamlined tuning process and larger bandwidths.

The GRF5112 (datasheet linked) provides a maximum fractional bandwidth of up to 40%, allowing designers to potentially accommodate two or more cellular bands in the same transmitter. Compared to the previous generation, this represents a 35% increase in fractional bandwidth.

An example 1.8 GHz design shows the utility of the GRF5112, with an 11% fractional bandwidth and a simple tuning network. Image used courtesy of Guerilla RF

The GRF5112 has a gain of 17.1 dB at 1.8 GHz, a 212 mA supply current with a 5 V supply, and a large temperature range that can still maintain linearity. Furthermore, the amplifier has a noise figure of 1.7 dB using the evaluation board. 

The 3 mm × 3 mm QFN GRF5112 and accompanying evaluation boards are available for sampling now from Guerilla RF.