Broadband Solid-state Class A Power Amplifiers for 1 to 11 GHz Applications
Introduction to the highly functional and extremely flexible series 2000 boradband solid-state class A power amplifier
With microwave power amplifiers finding applications in such diverse and demanding fields as communications, medical systems, test equipment and the military market, functionality, adaptability and flexibility of design are distinct assets. The Series 2000 broadband solid-state class A power amplifiers meet these requirements, operating in the 1 to 11 GHz frequency range, with output powers from 1 to 1000 W.
Modularity of design is a key feature, allowing a combination of exceptional power density (250W RF power in a 3U package) coupled with solid-state reliability and ease of use. In addition, this modularity allows the user to have their unit reconfigured, with respect to frequency and power, as end-user requirements evolve and change over time. With the ability to withstand 100 percent reflected power indefinitely, all models in the series find use in high power applications, such as passive intermodulation testing, component testing, high energy research physics and antenna testing. Figure 1 shows the typical transfer characteristics of the AS0102-200 amplifier at 2.1 GHz. Figure 2 shows the amplifiers adjacent channel power characteristics and a measurement of adjacent channel power is shown in Figure 3.
The front panel, shown in Figure 4, has provision for up to four N-type and four SMA connectors, while the rear panel has provision for two N-type and two SMA connectors. The front panel also features fault status indication, which highlights a module or supply fault within the amplifier or an SWR or interlock problem external to the unit.
The front panel can be "locked out," via a software command, to prevent unauthorised users from changing amplifier parameters when the amplifier is being operated remotely. A choice of power monitor outputs is available at the user's request. Integral directional couplers, built into the power combiners, have the capability to provide RF and detected RF sample outputs. Additionally, two LED bar graph displays on the front panel indicate forward and reverse power.
To enhance safe operation in high power applications the Series 2000 features a safety interlock on the rear of the amplifier, which can be hard-wired into the safety system of a laboratory. If the interlock is removed the amplifier will either shut down or sound an audible warning. This response is user-configurable. For example, if the power amplifier were being used in an EMC shielded room and radiating 220W it can be wired so that the amplifier will automatically shut down when the chamber door is opened.
Cooling is by forced air convection using integral air blowers. There is one air supply intake for the power supply unit and one for the amplifier blocks. Both have black dust filters, which are simply pulled out for cleaning and easily pushed back into place.
Series 2000 amplifiers allow four user-configurable options via a set of switches accessed behind the front panel dust filter. The 'minimum instruction set' makes a Series 2000 unit fully backwards compatible with the existing installed base of the company's amplifiers. Setting this option allows a Series 2000 unit to respond exactly to software instructions as an earlier model would.
The customer can tailor the response of the amplifier on detecting excessive reflected power. Although the power amplifier will withstand 100 percent reflected power, the level at which the amplifier will trip is user-configurable. This allows the user to have the SWR warning light illuminate to indicate poor system load conditions. The customer can also choose to have the amplifier either shut down or sound an audible warning when an excessive SWR is encountered.
The safety interlock can be set by the user to be non-latching (that is, provide a visible warning only) and the audible alarm can be disabled. These are selected via two additional configurable switches.
One of the most common add-on options is the IEEE control, which is a 19-inch bolt on tray, affording RS 232 and GPIB control. Alternatively, there are digital ports on the rear of the unit allowing direct TTL control of the on/off functions, frequency band selection, front panel lockout and access to all available monitoring functions.
Although offering standard models, the modularity and options available on the Series 2000 not only afford flexibility but also provide the facility for quick and easy upgrading and future proofing to accommodate additional requirements and extend useful working life. Additional information is available at www.milmega.com.
Isle of Wight, UK
+44 (0) 1983 618000.
Circle No. 303