What is claimed is:
1. An automatic filter tuning control system for tuning a characteristic frequency of a filter to a target frequency, the system comprising:
circuit configuration replacing means for replacing an original circuit configuration of the filter with an alternative tuning-dedicated circuit configuration while the filter is being tuned, wherein the filter with the alternative configuration has the same characteristic frequency as that of the filter with the original configuration and shows a signal-to-noise ratio higher than that of the filter with the original configuration;
a characteristic tuner, which measures one or some periods of an oscillating waveform appearing at the output of the filter with the alternative configuration when an impulse signal, pulse signal or step signal is input as a test signal to the filter;
detects the characteristic frequency of the filter in accordance with the period measured; and
then supplies a tuning signal to the filter, thereby adjusting a difference between the characteristic and target frequencies; and
a controller, which issues a tuning instruction to start the characteristic tuner and then stores a level of the tuning signal when the difference between the characteristic and target frequencies of the filter enters a tolerance range, wherein in operating the filter, the controller restores the filter to the original configuration, stops operating the characteristic tuner and controls the characteristics of the filter using the tuning signal stored.
2. The system of claim 1, wherein the filter is a gm-C filter comprising a plurality of transconductance amplifiers and a plurality of capacitors.
3. The system of claim 1, wherein the circuit configuration replacing means comprises means for boosting a gain of the filter being tuned.
4. The system of claim 1, wherein the circuit configuration replacing means comprises means for increasing a quality factor of the filter being tuned.
5. The system of claim 1, wherein the circuit configuration replacing means comprises means for oscillating the filter being tuned at the characteristic frequency of the filter.
6. The system of claim 1, wherein the controller averages levels of the tuning signal that has been input to the filter at multiple tuning attempts, stores the tuning signal with the averaged level and controls the characteristics of the filter using the tuning signal with the averaged level.
7. The system of claim 1, wherein the characteristic tuner comprises:
a frequency divider for dividing the frequency of a clock signal that has been delivered as a reference signal;
a test signal generator for generating the test signal from the clock signal with the divided frequency;
a counter for measuring one or some periods of the oscillating waveform, which appears at the output of the filter responsive to the test signal, synchronously with the clock signal;
a frequency detector for detecting the characteristic frequency of the filter based on the period measured by the counter; and
an updown counter for changing the tuning signal in accordance with the difference between the detected characteristic frequency and the target frequency.
8. The system of claim 7, further comprising a digital-to-analog converter, which receives the tuning signal as a digital quantity from the characteristic tuner or the controller and supplies an analog control signal, corresponding to the tuning signal, to the filter.
9. The system of claim 7, further comprising a phase-locked loop circuit for generating the reference signal.
10. The system of claim 7, wherein the greater the difference between the detected characteristic frequency and the target frequency, the more greatly the updown counter changes the tuning signal.
11. The system of claim 7, wherein when the detected characteristic frequency is close to the target frequency, the updown counter decreases control sensitivity of the tuning signal.
12. The system of claim 7, wherein the filter comprises a master filter and a slave filter, each of which has its characteristic frequency controlled variably responsive to the tuning signal, and wherein after the master filter has been tuned in advance in response to a second reference signal, obtained by dividing the frequency of the reference signal, the slave filter is tuned in response to the test signal.
13. A cellular phone comprising the automatic filter tuning control system as recited in one of claims 1 to 12 in a receiver section thereof.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for obtaining phosphors through microwave synthesis, the method comprising the steps of:
providing an insulator having an opening therein, wherein the opening is substantially symmetrically disposed in relation to a central axis of the insulator, and wherein the opening is adapted to receive a phosphor starting material;
depositing the starting material within the opening; and
subjecting the phosphor starting material to microwaves.
2. The method of claim 1, further comprising the step of positioning a susceptor configuration within the cavity, wherein the susceptor configuration is substantially symmetrically disposed in relation to the central axis of the insulator.
3. The method of claim 1, wherein the insulator is comprised of refractory material that is essentially transparent to microwaves in a working temperature range.
4. The method of claim 3, wherein the insulator is comprised of one of aluminosilicate fibers and alumina fibers.
5. The method of claim 4, wherein the phosphor is one of halophosphate, barium-magnesium aluminate, lanthanum phosphate, and europium doped yttrium oxide.
6. The method of claim 1, further comprising the step of positioning a susceptor configuration within the cavity.
7. The method of claim 1, wherein the microwave furnace is adapted to be tilted by raising the first end of the tube to facilitate the movement of the starting material through the tube.
8. A method of synthesis of a phosphor by microwave processing, the method comprising the steps of:
(a) providing a microwave furnace having a microwave chamber;
(b) providing a phosphor starting material in the microwave chamber; and
(c) subjecting the phosphor starting material to microwaves, whereby the starting material is synthesized into a phosphor.
9. The method of claim 8, wherein the phosphor is a halophosphate phosphor.
10. The method of claim 9, wherein the phosphor is represented by Ca10(PO4)6(Cl,F):Sb:Mn.
11. The method of claim 9, wherein the phosphor is synthesized by microwave processing at about 1000\xb0 C.
12. The method of claim 10, wherein the starting material comprises a mixture of HCaPO4, CaCO3, CaF2, NH4Cl, MnCO3 and Sb2O3.
13. The method of claim 12, wherein the phosphor is synthesized by microwave processing at about 1000\xb0 C. for about 20 minutes.
14. The method of claim 8, wherein the phosphor is a barium-magnesium aluminate.
15. The method of claim 14, wherein the phosphor is represented by BaMg1+xAl10+yO17+z, wherein 0<x<2.0, 0<y<5.0, and 0<z<10.5 and the phosphor has a europium activator.
16. The method of claim 14, wherein the phosphor is synthesized by microwave processing in a reducing atmosphere at about 1250\xb0 C. to about 1500\xb0 C.
17. The method of claim 16, wherein the phosphor is synthesized by microwave processing at about 1400\xb0 C. to about 1500\xb0 C.
18. The method of claim 15, wherein the starting material is a mixture of aluminum hydroxide, magnesium oxide, barium carbonate, europium oxide and a barium fluoride flux.
19. The method of claim 18, wherein the phosphor is synthesized by microwave processing in a reducing atmosphere at about 1250\xb0 C. to about 1500\xb0 C. for about 20 minutes.
20. The method of claim 8, wherein the phosphor is a lanthanum phosphate.
21. The method of claim 20, wherein the phosphor is represented by (La, Ce, Tb)PO4:Ce:Tb.
22. The method of claim 20, wherein the phosphor is synthesized by microwave processing at about 800\xb0 C. to about 1125\xb0 C.
23. The method of claim 21, wherein the starting material is a coprecipitate mixture of lanthanum phosphate, cerium phosphate and terbium phosphate.
24. The method of claim 21, wherein the starting material further includes a flux.
25. The method of claim 23, wherein the phosphor is synthesized by microwave processing at about 800\xb0 C. to about 1125\xb0 C. for about 10 to about 30 minutes.
26. The method of claim 8, wherein the phosphor is a europium doped yttrium oxide.
27. The method of claim 26, wherein the phosphor is synthesized by microwave processing at about 1100\xb0 C. to about 1350\xb0 C.
28. The method of claim 26, wherein the starting material is a mixture of yttrium oxide and europium oxide.
29. The method of claim 28, wherein the phosphor is synthesized by microwave processing at about 1100\xb0 C. to about 1350\xb0 C. for about 10 minutes to about 40 minutes.
30. The method of claim 29, wherein the mixture further includes a flux.
31. The method of claim 8, wherein the phosphor is synthesized without a flux.