Patent ID: 8306067

Claim:
A dual frequency multiplexer comprising a multiplexer port, a first port used to receive a first frequency band, a second port used to receive a second frequency band, a first and second coaxial harmonic oscillator type band pass filter, and a first and second direct current circuit, each of said first and second coaxial harmonic oscillator type band pass filters having a coaxial chamber; the first direct current circuit is connected between the first port and the multiplexer port, while the second direct current circuit is connected between the second port and the multiplexer port; one end of the first coaxial harmonic oscillator type band pass filter is connected electrically with the first port through a first blocking capacitor, while one end of the second coaxial harmonic oscillator type band pass filter is connected electrically with the second port through a second blocking capacitor; the other ends of both first and second coaxial harmonic oscillator type band pass filters are electrically coupled to the multiplexer port by a third blocking capacitor; wherein the first direct current circuit includes a first low pass filter coupled electrically with the first blocking capacitor, whilst the second direct current circuit includes a second low pass filter coupled electrically with the second blocking capacitor; the first and second direct current circuits share a common third low pass filter which is connected in electrical manner with the third blocking capacitor; the first and second coaxial harmonic oscillator type band pass filters are disposed in a box including a base body, a cover plate and a cover body; the two coaxial harmonic oscillator type band pass filters are located on the base body and spaced each other by a metal plate; the multiplexer port, first and second ports are positioned on a lateral side of the base body; the first and second blocking capacitors are contained in the coaxial chambers of the two coaxial harmonic oscillator type band pass filters; the cover plate is secured on the base body; the first and second direct current circuits are placed on the cover plate; the low pass filters of the first and second direct current circuits are each fixed on an edge of a top surface of a corresponding coaxial chamber in the corresponding coaxial harmonic oscillator type band pass filter by means of a support member; and the cover body and the base body are fastened with each other.