Expanding their selection of in-stock amplifiers available for same-day shipment, Pasternack has introduced a family of solid-state power amplifiers (SSPA) using GaN technology to achieve high power and power-added efficiency (PAE).
The SMA-connectorized portfolio comprises 12 models (see Table 1) that offer 10 to 100 W of saturated output power, PAE to 35 percent, gain from 43 to 60 dB and gain flatness as low as ±1.25 dB. The high output load impedance of GaN eases impedance matching, allowing lower loss matching components. The amplifiers are unconditionally stable, matched to 50 Ω at the input and output, with at most a 2:1 input VSWR. Harmonics are typically -15 or -20 dBc, spurious at -70 dBc—even with the broadband high frequency amplifiers—providing a predictable and stable response. Other features include DC on/off control using a TTL logic signal, and some models have voltage regulation, bias sequencing, current monitoring and temperature shutdown up to +90ºC, for added reliability.
Amplifier operating temperature range is from -40º to 85ºC. Many of the power amplifiers (PA) come in hermetically sealed packages for rugged environments. The PE15A5032F and PE15A5033F models have integrated heat sinks and cooling fans to ensure performance in high temperature applications. Aside from the technical performance, the GaN amplifier series offers a wide variety of monitoring features, for ease of use and optimum power handling.
GaN high electron mobility transistor (HEMT) technology is a very attractive option for the amplifier industry due its many advantages, including high power density, reliability, heat dissipation and the capability to amplify signals in the millimeter wave band. Still, the biasing and bias circuitry of high power RF devices require detailed analysis and design to prevent instabilities that can affect linearity or cause thermal runaway. The risk of instability can intensify with high current, continuous wave (CW) applications. To ensure best performance, Pasternack offers bias sequencing for most of these GaN amplifier models.
CURRENT AND TEMPERATURE MONITORING
Some models in Pasternack’s GaN PA series offer current monitoring to minimize potential instability and noise, as the current in GaN HEMT amplifiers can increase with temperature. An over temperature shutdown at +85º to +90ºC provides thermal protection to maintain the safe working operation of the device.
OVER VOLTAGE PROTECTION AND VOLTAGE REGULATION
Pasternack’s GaN amplifiers have under- and over-voltage shutdown, where the unit will shut down if the bias is below or above specified voltages. When the load at the output of the amplifier varies, the output voltage can change due to the change in current from the power supply, making internal voltage regulation a useful feature in a high power amplifier. Internal voltage regulation is also used to control temperature variation that can cause erratic operation of the sensitive internal semiconductor circuitry.
LOAD VSWR AND REVERSE BIAS PROTECTION
Ideally, an RF amplifier with a 50 Ω output impedance will be connected to a perfectly matched load, i.e., with an impedance of 50 Ω, where all the power from the amplifier transmitted to the load without any reflected. However, in real applications, the load impedance can vary greatly from the output impedance of the amplifier, reflecting an excessive amount of power back and potentially damaging the amplifier. Some of the models in Pasternack’s GaN SSPA family will withstand a 5:1 mismatch, with internal circuitry to protect the amplifier. Pasternack’s GaN amplifier lineup also offers infinite load VSWR protection at all amplitude and phase angles, as well as reverse bias protection, where the unit will not enable or draw current if the +VDC bias and ground are switched.
For digital communications applications, some of Pasternack’s GaN PAs offer linear coded orthogonal frequency division multiplexing (COFDM) power output for multi-path propagation. CW operation is also available in some models, as well as RF input signal formats of CW, amplitude modulation (AM), phase modulation (PM) and pulsed. Hermetically sealed amplifiers are available for applications that are exposed to the elements.
Most systems impose many challenging requirements on a high power amplifier, considering the type of signal, mismatch effects, operating temperature, current and voltage control and other environmental factors. Pasternack’s SSPA family offers multiple monitoring and protection systems to ensure the robustness of the amplifier design for long-term use and reliability (see Table 2).
The frequency coverage and high output power of Pasternack’s family of GaN SSPAs make them ideal for military and other radar systems, military and commercial communications, air traffic control, weather and earth observation satellite and medical applications. Amplifiers with linear COFDM power output ability are excellent for unmanned aerial vehicle and unmanned ground vehicle (UAV/UGV) data links as well as COFDM video applications. Pasternack’s GaN amplifier series can be used as high gain driver amplifiers and high gain, high output PAs.