Patent ID: 7479850
Filing Date: 2009-01-20
Classification: H01P

Abstract:
1. A miniaturised half-wave balun having a given operating frequency and comprising: a single-ended I/O port comprising a first signal carrying terminal for connection to a source impedance; a differential I/O port comprising second and third signal carrying terminals for connection to a load impedance; at least one transmission line comprising a first transmission line section and a second transmission line section of equal length and characteristic impedance, and wherein the length of said at least one transmission line is substantially less than one half of the wavelength of an RF signal at said operating frequency; a first loading shunt capacitor connected to a first circuit node at a first end of said first transmission line section; a second loading shunt capacitor connected to a second circuit node at a first end of said second transmission line section, said second ends of said first and said second transmission line sections being connected together at a third circuit node; and a shunt capacitive element connected at said third circuit node; wherein said first signal carrying terminal is coupled to said first transmission line section, wherein said second signal carrying terminal is connected directly to said first circuit node and is connected to said first transmission line section at first circuit node, wherein said third signal carrying terminal is connected directly to said second circuit node and is connected to said second transmission line section at said second circuit node, and wherein the capacitance of said shunt capacitive element is chosen so that the common mode impedance of said differential I/O port at a selected frequency is substantially zero Ohms.