Abstract: Efficiency of an RF/microwave power amplifier is increased at a back-off power level by increasing the load resistance of the amplifier at the reduced output power level as compared to load impedance at a higher power level including full operating power. The different load impedances can be realized with two amplification units in parallel each having different load impedances. Alternatively, a single amplification path can be provided with an output impedance matching network which is selectively bypassed for increased impedance load during back-off power operation. In another embodiment, the output impedance matching network can include a shunt inductance which is selectively switched into the network to increase impedance for back-off power operation.

Abstract: In a computer network consisting of at least one host computer and computer peripheral devices, such as scanners, fax machines, and printers, a user may use a hot key on the scanner to copy, scan, e-mail, and faxing etc. via the control of an application program. An auto-crop module implemented in the host computer can automatically crop the image of a scanned sheet. The cropped image is saved in the memory device. Before sending the cropped image to the computer peripheral devices, the computing module will compute the output format of the cropped image according to the resolution requirement and scaling factor of the associated computer peripheral device. The retained position will be also saved in the memory. In response to the user operation, the image of the scanned sheet with its retained position will be transmitted to the printer or facsimile machine via the control of the application program.

Abstract: In an RF amplifier circuit having a plurality of transistor stages with each transistor having an input terminal for receiving an RF signal, a bias circuit is provided for applying a DC bias to the input terminal of a transistor. An isolation circuit connects a DC power supply to a bias circuit whereby DC voltage from the power terminal is applied to the bias circuit and RF signal from the transistor input terminal is attenuated. The isolation circuit includes a reactive serial path which allows the flow of DC current and presents an impedance to RF current flow and a reactive shunt path to ground which can comprise a capacitor or a serial inductor/capacitor circuit. The reactive serial path can comprise an inductor or an inductor/capacitor parallel circuit.