Solid-state RF power transistors modernise microwave ovens

7th October 2014
Siobhan O'Gorman

The 250W MHT1003N and 350W MHT1002N RF power transistors, designed for consumer and commercial microwave oven appliance OEMs, have been released by Freescale Semiconductor. While the MHT1003N provides 58% power added efficiency for 2.45GHz microwave oven applications, the MHT1002N provides 63% for 915MHz microwave applications.

Without performance degradation, solid-state RF power technology provides efficient and controllable RF energy. The RF technology is, therefore, a good alternative to legacy magnetron-based microwave systems. According to Freescale, it's solid-state RF transistors are the first devices housed in plastic packages to operate at 915MHz and 2.45GHz. Using magnetron technology can result in uneven cooking as it uses a crude on/off control which causes energy to arbitrarily fill the microwave cavity. The solid-state devices allow RF energy to be controlled, enabling OEMs to develop ovens that provide more precise cooking, greater consistency in quality of cooking, selective heating, and cooking combinations. After as little as 500 operating hours, a magnetron can begin to lose its ability to produce RF energy. Under continuous use and without performance degradation, solid-state RF power is claimed to have a reliability of up to a 20-year lifetime. This reduces commercial kitchen downtime and repairs and ensures that food cooks consistently throughout the appliance's lifetime. 

To provide the capabilities required for operation, evaluation and optimisation of RF power devices, the solid-state RF power transistors are supported by Freescale's RF Power Tool system. Freescale introduced the RFPOWERTOOL1000 system to assist customers with little RF circuit design expertise and no RF instrumentation. By using the system, development can be simplified and time-to-market reduced. Claimed to be the only integrated RF power application development system on the market, Freescale's system provides OEMs with portable, multi-functional instrumentation capabilities. These capabilities are designed for key amplifier operation and measurements including gain, efficiency, bandwidth and bias requirements. The size, cost and complexity of RF lab equipment needed for application development are reduced as the system integrates its capabilities into a single compact unit. The need for a full bench of RF evaluation equipment is also reduced by this integration. Operating from a PC or front panel interface, the system can be installed quickly and easily and at a lower cost than a traditional RF bench setup.

Available in the OM-780-2L and -4L packages, the MHT1003N and MHT1002N RF power transistors are sold in 10,000 quantities and priced at $37.00 and $26.00, respectively. The RFPOWERTOOL1000 RF Power Tool system is available now and priced at $5,500. The RFPT-H2450-250, a MHT1003N compatible evaluation board is also available and priced at $1,650. 

“Solid-state RF power is a major leap forward for the market, and what we know as microwave cooking and how it’s performed over the last 30 years is all about to change,” said Paul Hart, Senior Vice President and General Manager of Freescale’s RF business. “Freescale’s full suite of RF heating products and essential development tools will enable our customers to create differentiated products that cook more efficiently, more effectively, and with greater consistency and higher quality.”

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