RF modem with oscillator switching circuit
AssigneeAMP Incorporated
InventorGerald L. Somer
Life of this patent
Estimating the term…
Abstract
A channel switching oscillator circuit (230) in which the oscillator frequency is selected from one of a predetermined number of frequencies by switching into the oscillator circuit (230) one of a plurality of tank circuits (L4, L5, L6). The tank circuit (L4, L5, L6) is resonant with one of a plurality of crystals (Y2, Y3, Y4) in the oscillator (230) to generate a carrier signal at the predetermined frequency. The crystals (Y2, Y3, Y4) remain in the oscillator circuit (230) with no switching thereof as the frequencies at which the crystals (Y2, Y3, Y4) oscillate are sufficiently far apart, coupled with the high Q of the tank circuit (L4, L5, L6), that only one of the crystals (Y2, Y3, Y4) is resonant with each tank circuit (L4, L5, L6).
Claims21
A channel switching oscillator for generating a radio frequency carrier signal, comprising:
- means for generating a time varying periodic signal;
- a plurality of nonswitchable frequency determining means for establishing the frequency of the periodic signal;
- a plurality of tank circuits individually switchable into the oscillator, each of said tank circuits resonant with a frequency determming means;
- and
- means for switching each of the tank circuits into the oscillator, whereby the tank circuit switched into the oscillator resonates with a frequency determining means.
A channel switching oscillator for generating a radio frequency carrier signal, comprising:
- a transistor amplifier configured as an oscillator for producing a time varying period signal;
- a capactive divider circuit between the transistor collector and ground, said capacitive divider circuit having a divided voltage point;
- a plurality of frequency determining means between the divided voltage point and the transistor emitter;
- a plurality of tank circuits between the transistor collector and ground, each of the tank circuits individually switchable into the oscillator;
- controllable switching means for switching each of the tank circuits into the oscillator;
- and
- means for controlling the switching means to determine which tank circuit is switched into the oscillator.
A channel switching oscillator for generating a radio frequency carrier signal, comprising:
- a transistor amplifier configured as an oscillator for providing a time varying periodic signal;
- a capacitive divider circuit between the transistor collector and ground, said capacitive divider circuit having a divided voltage point;
- a plurality of frequency determining crystals between the divided voltage point and the transistor emitter;
- a plurality of tank circuits between the transistor collector and ground, said tank circuits individually switchable into the channel switching oscillator;
- each of the tank circuits having a first diode between the tank circuit and ground, the cathodes of said first diodes forming a common point;
- biad means between the common point and ground for reverse biasing the common point from ground potential;
- a channel select circuit;
- a second diode associated with each tank circuit, the anode of said second diode connected to the channel select circuit, the cathode of said second diode connected to the anode of each respective first diode, whereby to switch a tank circuit into the channel switching oscillator the channel select circuit energizes the second diode associated with the tank circuit to be switched which in turn energizes the respective first diode and generates a voltage across the bias means to reverse bias to the unused first diodes thus switching into the oscillator circuit one tank circuit of said plurality of tank circuits while preventing the other tank circuits from being switched into the oscillator circuit.
Dependencies are inferred from the claim text.