RFHIC Corporation has developed a 30 kW solid-state microwave generator for industrial and medical applications such as sterilizing, heating, drying, welding and scanning. An all solid-state design using GaN transistors, the RIK0930K-40T provides 30 kW CW output power at the RF cavity with a system efficiency of 56 percent across a 30 MHz bandwidth, tunable between 900 and 930 MHz.
RFHIC’s GaN microwave generators offer many benefits compared to magnetron sources on the market, setting a new standard for microwave energy in the digital age. The RIK0930K-40T provides differentiated value from both the product and RFHIC’s service.
MODULAR
The generator consists of eight rack-mountable shelves, each containing two, 2 kW GaN power amplifiers (PAs) which are water cooled. The shelf architecture makes the PAs easily accessible by users for quick PA replacement and output power scaling with minimum downtime and maintenance cost.
The generator has a three-phase, 50/60 Hz, air-cooled power supply unit, capable of 380 to 400 VAC operation, and a WR-975 waveguide converter. 220 to 240 and 480 VAC power supply voltages are available as custom options. Without the AC terminal box and external power combiner, the size of the generator system is 2048 cm high × 1018 cm deep × 810 cm wide and it weighs 520 kg. The generator height is being reduced by approximately 178 cm, i.e., 4U.
DIGITAL MONITORING AND CONTROL
RFHIC’s solid-state microwave generator has many advantages over a magnetron. The output frequency of a magnetron is determined by the cavity’s physical dimensions and, unlike GaN PAs, the magnetron cannot amplify the power of an applied microwave signal. It only serves as an oscillator, with limited control of frequency, power, phase and the signal source. The magnetron is controlled by an analog voltage, constraining users from controlling and monitoring the system remotely.
In comparison, the RIK0930K-40T uses a phase-locked loop synthesizer to digitally generate the desired frequency, producing more precise and stable frequencies with a low noise floor (see Figure 1). The solid-state microwave generator system includes RFHIC’s software suite, which includes accurate and nearly instantaneous power controls. Various frequency control modes are provided, including frequency sweeping. The software’s built-in analytic feature performs real-time monitoring with automatic frequency adjustment, enabling users to create an optimal “recipe” for an application. The system constantly monitors and adjusts the key operating parameters to provide the optimal amount of microwave energy to the target, tuning the frequency and controlling phase over 360 degrees.
Figure 1 A solid-state microwave generator (a) provides better frequency control and spectral purity than a typical magnetron generator (b). Output power for each at 1 (left), 3 (middle) and 6 (right) kW.
Another feature of the RIK0930K-40T is the high speed, pulse mode operation, with a pulse duty cycle of 1 to 99 percent and switching from CW to pulse within 100 ms. The pulse mode is beneficial for plasma generating, welding and sterilizing applications.
DURABLE AND RELIABLE
Magnetron systems are equipped with a single microwave source and operate at high voltage—up to 38 kV. Magnetron heads have an average lifetime from 2,000 to 5,000 hours, and they typically lose 30 to 40 percent of rated power over their lifetime. The short lifetime and high voltage operation have made magnetrons unsuitable for automated and industrial operations, where safety and minimum downtime are crucial.
To address this, RFHIC designed the PAs with GaN devices, so the microwave generators are durable and cost efficient, particularly for agile manufacturing. The RIK0930K-40T is equipped with reliable components and various protective features and has an average lifetime of 50,000 to 100,000 hours, depending on the operational settings and usage.
As noted, the RIK0930K-40T includes a three-phase, 400 VAC, 50/60 Hz power supply which provides 50 VDC bias for the generator. The generator provides a stable source of microwave energy without fluctuations and a safe environment for industrial manufacturing environments. The solid-state power supplies have a switch-mode design, which helps filter AC ripple, making the solid-state generator less sensitive than magnetrons to the quality of the AC power.
For added protection, the RIK0930K-40T is equipped with sensors that monitor the system’s temperature, forward/reverse power and current. The PAs within the system have a maximum operating temperature of 80°C, and the maximum current is 60 A. If the system’s sensors detect high reverse power, temperature or current, the system automatically shuts down to prevent damage. Each of the 16 PAs in the system is equipped with high power isolators to absorb any reflected power, preventing it from damaging the PAs. With a VSWR of 3:1 at maximum output, the system will withstand up to 25 percent of the reflected energy at maximum output power without any damage.
SCALABLE
Figure 2 60 kW solid-state microwave generator prototype, combining two 30 kW generators.
RFHIC’s GaN microwave generators are designed with a scalable architecture so users can easily add multiple power blocks to meet changing requirements. To increase the available power range, RFHIC is developing a 60 kW, 900 to 930 MHz, solid-state microwave generator (see Figure 2). A sample is planned to be completed during July of this year.
VALUE
The microwave industry is generally aware of the low acquisition cost for magnetron systems. The magnetron head is sold at a low price, benefiting from its larger manufacturing volume but the power supply is sold for a premium. In comparison, RFHIC’s systems use 50 VDC, cost-efficient power supplies, which increase system efficiency and reliability. Although the initial cost of the GaN PAs may be higher than a magnetron head, the differentiating features of RFHIC’s microwave generators provide significant added-value in control, quality and reliability. Comparing the total cost of ownership, the GaN PA design is equivalent to a magnetron within two to three years.
RFHIC is semi-vertically integrated, the only company with a portfolio from GaN transistors and PAs to full systems, from commercial off-the-shelf products to custom modules and sub-systems delivering output power to multi-megawatts. RFHIC’s GaN PA capabilities provide the highest quality and cost efficient solid-state microwave generators in the industry, supported with fast lead times—from three to six months—and excellent service.
RFHIC Corp.
Anyang, South Korea
www.rfhic.com