FSK modulator using saw resonator with switchable capacitors
First Claim
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1. In combination with an amplifier for oscillation, an FSK modulator comprising:
- a surface acoustic wave resonator connected to said amplifier;
a switching circuit connected in series with said surface acoustic wave resonator, said switching circuit including one or more fixed-capacity capacitors and a semiconductor switch having first and second terminals and being capable of being set in an ON condition or an OFF condition wherein said semiconductor switch is respectively conductive or non-conductive between said first and second terminals and thereby causing one or a combination of said fixed-capacity capacitors to be connected in series with said surface acoustic wave resonator; and
an input terminal connected to said semiconductor switch for receiving input signals for setting said semiconductor switch selectably in said ON or OFF condition.
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Abstract
An FSK modulator including an amplifier for oscillation has a surface acoustic wave resonator connected in series with a switching circuit formed without a variable-capacity diode but including a semiconductor switch and one or more fixed-capacity capacitors. When an input signal is received, the switch causes a capacitor or combination of capacitors to become connected in series with the surface acoustic wave resonator, providing oscillations with two frequencies to effect FSK modulation.
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Citations
19 Claims
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1. In combination with an amplifier for oscillation, an FSK modulator comprising:
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a surface acoustic wave resonator connected to said amplifier; a switching circuit connected in series with said surface acoustic wave resonator, said switching circuit including one or more fixed-capacity capacitors and a semiconductor switch having first and second terminals and being capable of being set in an ON condition or an OFF condition wherein said semiconductor switch is respectively conductive or non-conductive between said first and second terminals and thereby causing one or a combination of said fixed-capacity capacitors to be connected in series with said surface acoustic wave resonator; and an input terminal connected to said semiconductor switch for receiving input signals for setting said semiconductor switch selectably in said ON or OFF condition. - View Dependent Claims (2, 3, 4)
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5. A FSK modulator comprising:
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an amplifier including; a field-effect transistor (FET) for oscillation having a gate, a source and a drain; a first capacitor connected to the gate of said FET; and a second capacitor connected in series with said first capacitor between said first capacitor and the ground, a junction point between said first and second capacitors being connected to the source of said FET, through a resistor to the ground and to an output terminal, the drain of said FET being connected through a third capacitor to the ground; a surface acoustic wave resonator connected to the gate of said FET; a switching circuit connected in series with said surface acoustic wave resonator, said switching circuit including one or more fixed-capacity capacitors and a semiconductor switch having first and second terminals and being capable of being set in an ON condition or an OFF condition wherein said semiconductor switch is respectively conductive or non-conductive between said first and second terminals and thereby causing one or a combination of said fixed-capacity capacitors to be connected in series with said surface acoustic wave resonator; and an input terminal connected to said semiconductor switch for receiving input signals for setting said semiconductor switch selectably in said ON or OFF condition. - View Dependent Claims (6, 7, 8)
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9. In combination with an amplifier for oscillation having a control port and an output port, an FSK modulator comprising:
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a surface acoustic wave resonator of a two-port type having a first port and a second port, one end of said first port being connected to either one of said control and output ports of said amplifier, the other end of said first port being grounded; a switching circuit connected between one end of said second port of said surface acoustic wave resonator and the other of said control and output ports of said amplifier, the other end of said second port of said surface acoustic wave resonator being grounded, said switching circuit including one or more fixed-capacity capacitors and a semiconductor switch, said semiconductor switch having first and second terminals and being capable of being set in an ON condition or an OFF condition wherein said semiconductor switch is respectively conductive or non-conductive between said first and second terminals and thereby causing one or a combination of said fixed-capacity capacitors to be connected in series with said surface acoustic wave resonator; and an input terminal connected to said semiconductor switch for receiving input signals for setting said semiconductor switch selectably in said ON or OFF condition. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification