System and method for frequency translation using an image reject mixer
View Patent ↗Frequency translation, such as frequency up conversion of a video baseband or intermediate frequency to a desired frequency division broadcast channel, is provided utilizing a single sideband or image reject mixer and filtering having relaxed selectivity requirements. According to a preferred embodiment, a first single sideband mixer accepts an input signal at an intermediate frequency and up converts this signal to a high intermediate frequency. The image rejection provided by the single sideband mixer in combination with simple filtering provide sufficient signal quality to achieve desired levels of desired signal isolation, such as on the order of 40 dB. Preferably, a second single sideband mixer accepts the high intermediate frequency signal and down converts this signal to a desired transmission or broadcast frequency. The image rejection provided by the single sideband mixers in combination with simple filtering provide sufficient desired signal isolation, such as on the order of 40 dB, thereby relax the linearity requirements of amplifiers utilized in the frequency translation system. A preferred embodiment of the present invention disposes all or substantially all the frequency translation circuit elements on a single substrate.
1. A method of providing a frequency translation circuit comprising:
providing a first single sideband mixer having a first input and a first output, wherein a signal provided to said first input is provided to said first output at an increased frequency;
providing a second single sideband mixer having a second input and a second output, wherein said second single sideband mixer is coupled to said first single sideband mixer, and wherein a signal provided to said second input is provided to said second output at a decreased frequency, and wherein said first single sideband mixer and said second single sideband mixer are disposed in a common integrated circuit substrate;
providing at least one filter having frequency selection characteristics insufficient to independently provide head end quality signal characteristics; and
operating said frequency translation circuit to provide video head end quality frequency translation through operation of said first single sideband mixer, said second single sideband mixer, and said at least one filter.
2. The method of claim 1 , further comprising:
disposing a filter of said at least one filter between said first single sideband mixer and said second single sideband mixer, wherein said filter is adapted to substantially rely upon said first single sideband mixer for image rejection.
3. The method of claim 1 , further comprising:
at least one amplifier having linearity characteristics insufficient to provide head end quality signal characteristics when tones associated with an undesired image signal are present with tones of a signal to be amplified.
4. A system comprising:
an integrated circuit having a common substrate comprising:
a first single sideband mixer having a first input and a first output, wherein a signal provided to said first input is provided to said first output at an increased frequency;
a second single sideband mixer having a second input and a second output, wherein said second single sideband mixer is coupled to said first single sideband mixer, and wherein a signal provided to said second input is provided to said second output at a decreased frequency; and
at least one filter having frequency selection characteristics insufficient to independently provide head end quality signal characteristics.
5. The system of claim 4 wherein a filter of said at least one filter is disposed between said first single sideband mixer and said second single sideband mixer, and wherein said filter is adapted to substantially rely upon said first single sideband mixer for image rejection.
6. The system of claim 4 further comprising at least one amplifier having linearity characteristics insufficient to provide head end quality signal characteristics when tones associated with an undesired image signal are present with tones of a signal to be amplified.
7. The system of claim 6 wherein said at least one amplifier is included on said integrated circuit substrate.
8. A frequency translation circuit comprising:
a first single sideband mixer having a first input and a first output, wherein a signal provided to said first input is provided to said first output at an increased frequency, said first single sideband mixer disposed on an integrated circuit substrate;
a second single sideband mixer having a second input and a second output, wherein a signal provided to said second input is provided to said second output at a decreased frequency, said second single sideband mixer disposed on said integrated circuit substrate; and
a filter disposed on said integrated circuit substrate and further disposed on a signal path between said first single sideband mixer and said second single sideband mixer, said filter configured to have frequency selection characteristics insufficient to independently provide head end quality signal characteristics.
9. The frequency translation circuit of claim 8 further comprising an amplifier disposed on said signal path at an output of said second single sideband mixer, said amplifier configured to have linearity characteristics insufficient to provide head end quality signal characteristics when tones associated with an undesired image signal are present with tones of a signal to be amplified.
10. The frequency translation circuit of claim 8 wherein said amplifier is included on said integrated circuit substrate.