Microstrip-to-waveguide power combiner for radio frequency power combining

#This invention relates to power combining radio frequency signals, and more particularly, this invention relates to a power combining network for combining radio frequency signals using microstrip and waveguide circuits.

#Power combining techniques for radio frequency signals, including millimeter wavelength signals, have been accomplished in either a waveguide circuit or in a microstrip circuit. For example, prior art waveguide combining has been accomplished by feeding two or more signals in phase into a waveguide combiner. Although this type of power combining is efficient, the summing network is generally bulky and requires very high precision components. Microstrip power combining circuits have been accomplished by summing signals using a hybrid combiner circuit or a Wilkinson power summer circuit as known to those skilled in the art. This type of power combining circuit is more simple to implement in practice, but generally has higher losses.

#FIG. 1 illustrates a typical waveguide combiner 20, widely available in the industry, and traditionally used to combine radio frequency signals from two sources of RF power. The combiner 20 can be formed from different materials as known to those skilled in the art, and generally has two input ports 22 that are bolted or fastened by other techniques to respective waveguide sources. The signals combine and are summed at the output port 24. This combiner 20 provides a reliable method of adding radio frequency energy, but requires careful phase matching of two radio frequency inputs and precisely control over the length of the two waveguide sides 26. The precision requirements for this waveguide and the requirement for a metal coating on the inside surface of the waveguide to achieve low losses results in relatively expensive devices. Also, this waveguide combiner is usually bulky, as illustrated, and occupies a significant amount of space.

#Other objects, features and advantages of the present invention will become apparent from the detailed description of the invention which follows, when considered in light of the accompanying drawings in which:

#FIG. 1 is an isometric view of a prior art waveguide combiner.

#FIG. 2 is a schematic circuit diagram of a prior art microstrip power combiner as a Wilkinson combiner.

#The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

#The present invention is advantageous and power combines radio frequency signals using a combination of microstrip and waveguide or coax and waveguide techniques that result in very low losses. The power combining network of the present invention is extremely compact and can be used at a very low cost. In the present invention, two or more sources of radio frequency energy can be combined in a microstrip-to-waveguide or coax-to-waveguide transitions resulting in extremely low losses. Also, two or more sources of radio frequency energy are combined in microstrip-to-waveguide transition and are not as sensitive to phase mismatch between the radio frequency sources as other methods of power combining. The power combining is achieved efficiently at a low cost and is implemented in compact spaces. The method and apparatus of the present invention allow RF power combining that can be implemented at any frequency where energy can be transferred over a waveguide.

#FIGS. 4A and 4B illustrate respective side and front views of a coaxal-to-waveguide transition 49′ of the general type that can be modified and used with the present invention, including a coaxial cable support body 49a, formed back short 49b, a single launch probe 49c and coaxial connector 49d. Through holes (or screw holes) 49e provide means for receiving screws or other attachment fasteners (not shown) as known to those skilled in the art. This type of transition is widely used in the industry and has a 0.25 to 0.5 dB loss.