Power Electronics ♦ news digest


Figure 2: Photo and structure of GaN wide broadband T/R module


Key features of the new technology include an embedded heat sink structure that efficiently dissipates the heat generated at high output levels. The heat sink is built into the T/R module’s multilayer alumina ceramic substrate. Compared to previous designs, heat dissipation improved by a factor of five times, enabling high output levels of 10 W.


An ultra-broadband terminal structure reduces the input/output terminal signal loss that occurs at higher frequencies. High frequency signals passing through the module can be transmitted at up to 40 GHz, three times the frequency levels of previous designs.


Figure 1: Usage scenarios for multifunctional radars operating across C-Ku bands


T/R modules are essential to operate multifunctional radar over a broad spectrum. Users therefore demand that T/R modules possess wideband features capable of operating across multiple frequency ranges, and high output performance so as to cover a wide area.


To develop a T/R module with 10 W-class high output power over a wide broadband range, such as the C-Ku band, not only is a wideband PA and LNA required, but it is also critical to improve the T/R module’s heat dissipation characteristics as heat generation intensifies in tandem with higher output levels.


In addition, it is also necessary to reduce signal losses in the input/output terminal to maintain frequencies up to 18 GHz. This is because at higher frequency ranges input/output signal losses increase in the terminal portion of the T/R module.


In addition to the GaN HEMT PA, the researchers have now developed a new LNA that uses a GaN HEMT. The compact 2.7 × 1.2 mm LNA achieves a gain of 16 dB across 3-20 GHz, and noise figures of 2.3-3.7 dB, representing one of the world’s best performance levels.


Figure 3: Photo and cross-sectional diagram of GaN wide broadband T/R module


The T/R module measures only 12 × 30 mm and paves the way for further system integration in broadband communications and radar systems that utilise various frequencies, meaning more compact and lighter equipment.


Cree unveils gallium nitride HEMTs for S-Band radar


The firm will be showcasing its GaN transistors and MMICs which it says deliver industry leading power and efficiency for applications at 2011 IEEE IMS.


October 2011 www.compoundsemiconductor.net 179


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