QWED cooperates with the team of engineers from the Institute of Radioelectronics, Warsaw University of Technology (IRE WUT), in design and manufacturing of specialised solid state sources of microwave power. The sources are destined for microwave power applications including precision heating, microwave chemistry, plasma generation, etc.
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custom-made, computer-controlled solid state power sources
for microwave power applications
The offered solid state microwave sources have many advantages with respect to classical magnetron-based solutions:
extremely good spectrum purity and high frequency stability,
possibility of precise frequency tuning in a wide range,
possibilities of external computer control of generated frequency and power as a function of time or data acquired as a feedback from the physical system.
The well-known limitation of usage of the solid state sources, namely their relatively high price, has been mitigated due to the progress in manufacturing of high power transistors based on Si LDMOSFET and GaN HEMT technologies.
QWED offers the synthesised high-power microwave sources, including isolator at the output, with technical parameters as follows:
A general view of the unit producing 200 W of CW power
in the 2.45GHz ISM band combining of 4 60W GaN HEMTs.
frequency range to be defined (from hundreds of MHz up to X-band); power levels defined below concern the most typical band around 2.45 GHz,
output power level up to 200W for CW and pulsed operation,
output power controlled within 20dB dynamic range (optionally 30dB),
frequency tunability: 10% in the L, S and C band with a typical step of 1MHz,
long-term frequency stability: 2ppm,
short-term frequency stability: better than -75dBc/Hz@1kHz,
autonomous mode or cooperation with PC via USB interface,
fully functional front panel with a display and keyboard,
software tailored to the individual needs of the user,
air-cooled and AC supply 240V/50-60Hz,
size: 19" rack enclosure, typically 4U high.
measurement of reflection coefficient versus frequency, at high power levels,
automatic tuning of the frequency of the system, to the minimum of reflection from the load changing in time.
Block diagram of a typical solid state microwave power unit.
Typical applications of QWED microwave power sources include:
Heating of small volumes
Microwave power units can be used for precision heating of relatively small volumes. Typical examples can be found in microwave chemistry applications. Narrow spectrum of the source allows choosing a specific mode of the resonant cavity in which the substance is being heated. The computerised system can lock the generator to that mode, even when the resonant frequency of the cavity changes due to changing temperature of the load.
Detection of leakage from microwave power installations
Microwave power units can be used for measurement of leakage from microwave power installations. When a leakage is detected in a high power microwave installation driven by a magnetron source, it is quite difficult to detect its cause precisely. To control the leakage we need to know its frequency dependence which cannot be measured using the magnetron source.
Application of multiple power units controlled from one Master Unit
Microwave power units can be used to deliver power of the same frequency but with individual amplitudes and phase shifts between, computer controlled from a single Master Unit.
An example application of that kind of setup for microwave heating - feeding a microwave cavity from multiple sources
with controlled phases of the signals can bring a significant improvement in the heating efficiency.
Technical parameters are always customised in response to the user needs. For the exemplary MPU source designed and manufactured for the industrial company, parameters of microwave heating have been as follows:
| Output power and output power step
||4W ÷ 200W, ≤1dB
| Frequency range and frequency step
||2350MHz ÷ 2600MHz, 1MHz
| Maximum number of frequency points
||2kHz square wave
| Output impedance
| Output protection
|| Circulator with integrated dummy load
|| N Type
| Power supply
| Connection to PC
| Operating ambient temperature range
||0 ÷ +400C
The MPU is provided with:
||Fixed excitation frequency.
Continuous sweep of excitation frequency from start to stop settings.
Sweep of excitation frequency from start to stop settings, lock at maximum output power (minimum reflection).
Set output power.
||Select modulation: on/off.
Start excitation frequency.
Stop excitation frequency.
If start and stop frequencies are the same, set a fixed excitation frequency.
Sweep time for frequency sweep.
Output power level.
|Output Data from MPU
Log(output power)= Log(transmitted power)-Log(reflected power).
Set start excitation frequency.
Set stop excitation frequency.
If start and stop frequency are the same, set a fixed excitation frequency.
Set sweep time for frequency sweep.
Choose output power level.
Choose continuous sweep of excitation frequency from start to stop settings.
Choose sweep of excitation frequency from start to stop settings, lock at maximum output power (minimum reflection).
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