Structure for preventing intermodulation interference in satellite transmission
First Claim
1. A structure for preventing intermodulation interference in satellite transmission, comprising:
- a receiving antenna for receiving vertical and horizontal polarized signal sent from a satellite;
an RF amplifying system for down-converting and amplifying the received vertical and horizontal signals;
a first and a second band-pass filter for filtering signals output from said RF amplifying system;
a first mixer for receiving a signal output from said first band-pass filter and executing a frequency subtraction operation;
a local oscillator, from an oscillating frequency of which a frequency of said signal output from said first band-pass filter is subtracted in the frequency subtraction operation at said first mixer to generate a first mid-band;
a high-pass filter for filtering and isolating a signal within said first mid-band and output from said first mixer, and outputting the filtered and isolated signal;
a second mixer for receiving the signal filtered at and output from said second band-pass filter and executing a frequency subtraction operation;
a first-stage local oscillator, from an oscillating frequency of which a frequency of said signal output from said second band-pass filter is subtracted in the frequency subtraction operation executed at said second mixer to obtain a reverse-phase signal of said signal output from said second band-pass filter;
a third band-pass filter for filtering and isolating said reverse-phase signal output from said second mixer;
a third mixer for receiving the signal output from said third band-pass filter and executing a frequency addition operation;
a second-stage local oscillator, to an oscillating frequency of which a frequency of said signal output from said third band-pass filter is added in the frequency addition operation executed at said third mixer to obtain a second mid-band;
a low-pass filter for filtering and isolating a signal within said second mid-band and output from said third mixer, and outputting the filtered and isolated signal; and
a multiplex adder for receiving and combining said signals separately output from said high-pass filter and said low-pass filter;
whereby second and third harmonic differences between a frequency obtained by subtracting the oscillating frequency of said second-stage local oscillator from the oscillating frequency of said first-stage local oscillator and the oscillating frequency of said local oscillators do not fall in said first and said second mid-bands, respectively, and an intermodulation interference can therefore be prevented.
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Accused Products
Abstract
A structure for preventing intermodulation interference in satellite transmission is characterized in that a frequency subtraction is executed at a first mixer and a local oscillator on one of the received satellite vertical and horizontal polarized signals to obtain a first mid-band, while a frequency subtraction is executed at a second mixer and a first-stage local oscillator on the other received signal to obtain a reverse-phase signal thereof, and a frequency addition is executed at a third mixer and a second-stage local oscillator on the reverse-phase signal to obtain a second mid-band, and that second and third harmonic differences between a frequency obtained by subtracting the oscillating frequency of the second-stage local oscillator from the oscillating frequency of the first-stage local oscillator and the oscillating frequency of the local oscillators do not fall in the first and the second mid-bands, respectively, and an intermodulation interference is prevented.
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Citations
3 Claims
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1. A structure for preventing intermodulation interference in satellite transmission, comprising:
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a receiving antenna for receiving vertical and horizontal polarized signal sent from a satellite;
an RF amplifying system for down-converting and amplifying the received vertical and horizontal signals;
a first and a second band-pass filter for filtering signals output from said RF amplifying system;
a first mixer for receiving a signal output from said first band-pass filter and executing a frequency subtraction operation;
a local oscillator, from an oscillating frequency of which a frequency of said signal output from said first band-pass filter is subtracted in the frequency subtraction operation at said first mixer to generate a first mid-band;
a high-pass filter for filtering and isolating a signal within said first mid-band and output from said first mixer, and outputting the filtered and isolated signal;
a second mixer for receiving the signal filtered at and output from said second band-pass filter and executing a frequency subtraction operation;
a first-stage local oscillator, from an oscillating frequency of which a frequency of said signal output from said second band-pass filter is subtracted in the frequency subtraction operation executed at said second mixer to obtain a reverse-phase signal of said signal output from said second band-pass filter;
a third band-pass filter for filtering and isolating said reverse-phase signal output from said second mixer;
a third mixer for receiving the signal output from said third band-pass filter and executing a frequency addition operation;
a second-stage local oscillator, to an oscillating frequency of which a frequency of said signal output from said third band-pass filter is added in the frequency addition operation executed at said third mixer to obtain a second mid-band;
a low-pass filter for filtering and isolating a signal within said second mid-band and output from said third mixer, and outputting the filtered and isolated signal; and
a multiplex adder for receiving and combining said signals separately output from said high-pass filter and said low-pass filter;
whereby second and third harmonic differences between a frequency obtained by subtracting the oscillating frequency of said second-stage local oscillator from the oscillating frequency of said first-stage local oscillator and the oscillating frequency of said local oscillators do not fall in said first and said second mid-bands, respectively, and an intermodulation interference can therefore be prevented. - View Dependent Claims (2, 3)
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Specification