Method and circuit for achieving frequency conversion
First Claim
1. A frequency conversion method comprising:
- a first step of modulating a first excitation signal having a first excitation frequency by an input signal of a predetermined frequency to produce two sidebands and thereby generate a first intermediate signal;
a second step of modulating a second excitation signal having a second excitation frequency lower than said first excitation frequency by exactly a frequency twice the frequency of said input signal by said input signal to produce two sidebands and thereby generate a second intermediate signal; and
a third step of adding said first intermediate signal and said second intermediate signal so a lower sideband of the first intermediate signal and an upper sideband of the second intermediate signal are cancelled by each other to thereby generate an output signal composed of the upper sideband of the first intermediate signal and the lower sideband of the second intermediate signal.
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Abstract
A frequency conversion method and a frequency conversion circuit which enlarge the frequency difference between the upper and lower sidebands of the output signal so as to enable the undesired sideband to be easily eliminated by a filter even in a case where the frequency of the input signal is low. First, a first excitation signal having a first excitation frequency (Fp) is modulated by an input signal (a) of a predetermined frequency (F1) to produce two sidebands and thereby generate a first intermediate signal (b). Next, a second excitation signal having a second excitation frequency (Fq) lower than the first excitation frequency (Fp) by exactly a frequency twice the frequency of the input signal (a) is modulated by the input signal (a) to produce two sidebands and thereby generate a second intermediate signal (c). Further the first intermediate signal (b) and the second intermediate signal (c) are added so that the lower sideband of the first intermediate signal (b) and the upper sideband of the second intermediate signal (c) are cancelled by each other to thereby generate an output signal (d) composed of the upper sideband of the first intermediate signal (b) and the lower sideband of the second intermediate signal (c). By this, the space between the upper sideband and the lower sideband is widened and thereby the lower band erasing filter can easily erase the lower sideband.
36 Citations
18 Claims
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1. A frequency conversion method comprising:
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a first step of modulating a first excitation signal having a first excitation frequency by an input signal of a predetermined frequency to produce two sidebands and thereby generate a first intermediate signal; a second step of modulating a second excitation signal having a second excitation frequency lower than said first excitation frequency by exactly a frequency twice the frequency of said input signal by said input signal to produce two sidebands and thereby generate a second intermediate signal; and a third step of adding said first intermediate signal and said second intermediate signal so a lower sideband of the first intermediate signal and an upper sideband of the second intermediate signal are cancelled by each other to thereby generate an output signal composed of the upper sideband of the first intermediate signal and the lower sideband of the second intermediate signal. - View Dependent Claims (2, 3, 4)
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5. A frequency conversion method comprising:
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a first step of modulating a first excitation signal having a first excitation frequency to produce two sidebands by using an input signal which changes in frequency at predetermined time intervals according to a predetermined frequency pattern to thereby generate a first intermediate signal; a second step of modulating a second excitation signal having a second excitation frequency lower than said first excitation frequency by exactly a frequency obtained by adding the maximum frequency and minimum frequency of said frequency pattern to produce two sidebands by using a sub-input signal having a frequency lower than the frequency obtained by adding the maximum frequency and minimum frequency of said frequency pattern by exactly the frequency of said input signal to thereby generate the second intermediate signal; and a third step of adding said first intermediate signal and said second intermediate signal so that the lower sideband of the first intermediate signal and the upper sideband of the second intermediate signal are cancelled by each other to thereby generate an output signal composed of the upper sideband of the first intermediate signal and the lower sideband of the second intermediate signal. - View Dependent Claims (6, 7, 8)
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9. A frequency conversion circuit provided with:
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a first mixer which mixes a first excitation signal having a first excitation frequency and an input signal having a predetermined frequency to generate a first intermediate signal; a second mixer which mixes a second excitation signal having a second excitation frequency lower than said first frequency by exactly a frequency twice the frequency of said input signal and said input signal to generate a second intermediate signal; and an adder which adds said first intermediate signal and said second intermediate signal so that the lower sideband of the first intermediate signal and the upper sideband of the second intermediate signal are cancelled by each other to thereby generate an output signal composed of the upper sideband of the first intermediate signal and the lower sideband of the second intermediate signal. - View Dependent Claims (10, 13, 14, 15, 16)
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11. A frequency conversion circuit comprising:
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a first signal generator for outputting an input signal which changes in frequency at predetermined time intervals according to a predetermined frequency pattern; a second signal generator for outputting a sub-input signal having a frequency lower than a frequency obtained by adding the maximum frequency and minimum frequency of said frequency pattern by exactly the frequency of said input signal; a local oscillator for generating a first excitation signal having a first excitation frequency and a second excitation signal having a second excitation frequency lower than the first excitation frequency by exactly the frequency obtained by adding the maximum frequency and minimum frequency of said frequency pattern; a first mixer for mixing said first excitation signal and said input signal to thereby generate a first intermediate signal; a second mixer for mixing said second excitation signal and said sub-input signal to thereby generate a second intermediate signal; and an adder for adding said first intermediate signal and said second intermediate signal so the lower sideband of the first intermediate signal and the upper sideband of the second intermediate signal are cancelled by each other to thereby generate an output signal composed of the upper sideband of the first intermediate signal and the lower sideband of the second intermediate signal. - View Dependent Claims (12, 17, 18)
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Specification