Frequency combining circuit
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorTomoki Ueno
Life of this patent
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Abstract
A frequency combining circuit in the form of a planar transmission circuit has a four-port directional coupler, two transmission lines respectively coupled to the forward and backward coupling ports of the directional coupler, and two filters respectively coupled to the two transmission lines, one of the two filters being further coupled to a load. By applying a first frequency signal to the coupler input port and applying a second frequency signal to the other one of the filters, the first and second frequency signals are combined in an excellent manner at the coupler output port of the coupler due to the provision of the two filters both of which reject the first frequency signal and pass therethrough the second frequency signal.
Claims5
A frequency combining circuit in the form of a planar transmission circuit and operative in a selected frequency band, said frequency combining circuit comprising:
- a four-port directional coupler having a coupler input port for receiving a first frequency signal in a first frequency band, a first coupler branch line coupled to said coupler input port, a coupler output port coupled to said first coupler branch line for receiving said first frequency signal from said coupler input port through said first coupler branch line, a coupler forward coupling port coupled to said first coupler branch line for receiving a portion of said first frequency signal, a second coupler branch line coupled to said coupler forward coupling port, and a coupler backward coupling port coupled to said second coupler branch line and also coupled to said first branch line;
- a first transmission line coupled at one end thereof to said coupler backward coupling port;
- first filter means coupled to the other end of said first transmission line for receiving a second frequency signal from a signal source, said second frequency signal being in a second frequency band separated from said first frequency band, said first filter means having a filtering property for rejecting said first frequency signal and passing therethrough said second frequency signal to said first transmission line and hence to said coupler backward coupling port, a portion of said second frequency signal being transferred to said coupler output port, and the other portion of said second frequency signal being transferred to said coupler forward coupling port through said second coupler branch line;
- a second transmission line coupled at one end thereof to said coupler forward coupling port for passing therethrough to the other end thereof said portion of said first frequency signal from said coupler forward coupling port;
- second filter means coupled to said other end of said second transmission line and having a filtering property for rejecting said first frequency signal and passing therethrough said second frequency signal;
- and
- a load to which said second filter means is also coupled, said portion of said first frequency signal passed through said coupler forward coupling port and said second transmission line being rejected by said second filter means and being returned to said coupler forward coupling port through said second transmission line, and said other portion of said second frequency signal passed through said second coupler branch line, said coupler forward coupling port and said second transmission line being passed through said second filter means and being absorbed by said load, and the pass band of said frequency combining circuit for said first frequency signal being varied by varying the length of said first transmission line and the length of said second transmission line.
Dependencies are inferred from the claim text.