Patent ID: 6710813
Filing Date: 2004-03-23
Classification: H01P,H04N

Abstract:
A signal multiplexer for multiplexing a DTV signal and an NTSC signal that have different frequency bands, said signal multiplexer comprising:a first hybrid coupler and a first band pass filter that converts said NTSC signal into a first pair of filtered quadrature phase signals, wherein a video component of said NTSC signal is converted by said first hybrid coupler to produce said first pair of quadrature phase signals; a second hybrid coupler and a second band pass filter that converts said DTV signal into a second pair of filtered quadrature phase signals wherein said first and second band pass filters includes a pair of matched band pass filters, one for the quadrature phase signal of the first phase and the other for the quadrature phase signal of the second phase; a signal combiner that combines said first and second pairs of filtered quadrature phase signals to produce a pair of multiplexed quadrature phase signals; a notch filter that connected to said signal combiner and that is tuned to the aural frequency band of said NTSC signal; and a third hybrid coupler that converts said pair of multiplexed quadrature phase signals into a single multiplexed signal wherein said third hybrid coupler combines said reflected pair of aural quadrature phase signals and said pair of multiplexed quadrature phase signals into said single multiplexed signal; wherein said first hybrid coupler has a second port connected with a first load and third and fourth ports connected with separate ones of said first pair of matched band pass filters, wherein said second hybrid coupler has a second port connected with a second load and third and fourth ports connected with separate ones of said second pair of matched band pass filters, whereby out of band energy reflected from said first and second pairs of matched band pass filters is steered to said first and second loads.