Claims
- 1. A frequency conversion circuit comprising:
- a SAW filter;
- a SAW oscillator having the same temperature characteristics as those of said SAW filter;
- a second local oscillation oscillator for oscillating a second local oscillation signal using said SAW oscillator to modify a frequency of a first intermediate signal inputted into said SAW filter with respect to variations in the center frequency of said SAW filter's bandwidth caused by temperature changes;
- a frequency converter for converting a frequency of the second local oscillation signal to generate a first local oscillation signal, said frequency converter comprising a first mixer and a stable oscillator, wherein the second local oscillator and the stable oscillator are coupled to said first mixer for producing the first local oscillation signal;
- a second mixer for mixing the first local oscillation signal with an input signal to output the first intermediate frequency signal to said SAW filter; and
- a third mixer for mixing an output from said SAW filter with the second local oscillation signal to output a stable frequency conversion signal regardless of a frequency shift in said SAW filter due to a change in temperature.
- 2. A frequency conversion circuit according to claim 1, wherein said SAW filter and said SAW oscillator are jointly formed on a substrate.
- 3. A frequency conversion circuit according to claim 1, wherein said SAW filter and said SAW oscillator are jointly formed on a piezoelectric substrate.
- 4. A frequency conversion circuit according to claim 1, wherein said SAW filter is formed on a first piezoelectric substrate having a predetermined cut angle and said SAW oscillator is formed on second piezoelectric substrate having the same cut angle.
- 5. A frequency conversion circuit comprising:
- a SAW filter;
- a SAW oscillator having the same temperature characteristics as said SAW filter;
- a second local oscillator for oscillating a second local oscillation signal using said SAW oscillator to modify a frequency of a first intermediate signal inputted into said SAW filter with respect to variations in the center frequency of said SAW filter's bandwidth caused by temperature changes;
- a frequency converter for converting a frequency of the second local oscillation signal to generate a first local oscillation signal, said frequency converter comprises a first mixer and a phase lock loop oscillator wherein the second local oscillator and the phase lock loop oscillator are coupled to said first mixer for producing the first local oscillation signal;
- a second mixer for mixing the first local oscillation signal with an input signal to output the first intermediate frequency signal to said SAW filter; and
- a third mixer for mixing an output from said SAW filter with the second local oscillation signal to output a stable frequency conversion signal regardless of a frequency shift in said SAW filter due to a change in temperature.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2-179480 |
Jul 1990 |
JPX |
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Parent Case Info
This is a continuation of application Ser. No. 07/725,206, filed Jul. 3, 1991, now abandoned.
US Referenced Citations (10)
Non-Patent Literature Citations (1)
Entry |
Information Transmission, Modulation, and Noise, Misha Schwartz,.COPYRGT.1959, 1970, pp. 198-199, McGraw-Hill Book Company. |
Continuations (1)
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Number |
Date |
Country |
Parent |
725206 |
Jul 1991 |
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