Motorola Corporation

Jerry David Meyerhoff

Theodore V Lester

David J Priniski

Loren E Saar

A controllable fuse (10; 40; 50; 60; 80) has a pair of isolated conductor pads (26, 27), a solder connection (32; 41; 51) connected to the pads and providing a circuit connection therebetween, and at least one heater (14; 70, 75) to produce heat in response to an electrical signal. When sufficient heat is provided, the solder connection will desolder and disconnect the circuit connection between the conductor pads (26, 27). Major features are that the conductor pads and the heater are provided on a planar surface(s) (19, 25) as planar films and that redundancy for the fuse can be implemented by providing more than one heater (70, 75). A preferred manufacturing method for the fuse is disclosed which utilizes a solder retaining structure. Several fuse configurations are illustrated.

Controllable fuse

The antenna of a transceiver couples through a low pass filter to the input port of a high pass filter network. The high pass network is designed to reflect a very high impedance to its input port when its output port is at ground potential. The transmitter portion of the transceiver couples to the input port of the network with the receiver coupling to the network output port. A semiconductor diode couples from the output port to ground potential. In the receive mode the combination low pass and high pass filters couple received signals in the desired frequency band to the input of the receiver. Upon activation to the transmit mode the diode is forward biased whereby the network output port is taken to ground potential. In this mode the filter network effectively isolates the receiver from the transmitter.

Antenna switch

An improved balanced dual output diode mixer circuit having separate output terminals for audio and RF output signals is disclosed. The mixer circuit includes a first transformer having a primary and a center tapped secondary winding. The ends of the secondary winding are coupled to end terminals of two separate secondary windings of a second transformer through a switching circuit which comprises four diodes. RF bypass capacitors are coupled between an RF terminal and end terminals of the secondary windings of the second transformer and provide a low RF and a high audio impedance therebetween. RF chokes are coupled between audio output terminals and the RF bypass capacitors and provide a low impedance audio path which is connected at a point of low RF impedance. A pair of resistors coupled between ground and the RF bypass capacitors provide a DC current path to ground for the rectified DC current created by the switching network. The primary winding of the second transformer is coupled to RF output terminals. The balanced dual output diode mixer is adaptable for providing both audio and RF output signals when RF signals are applied directly to the primary winding of the first transformer and through the RF bypass capacitors to the secondary windings of the second transformer.

Growing community of inventors

Buffalo Grove, IL, United States of America

Jerry David Meyerhoff