Method of calibrating a multistage selective amplifier

A method of calibrating, to a selected receiving frequency, a multistage selective amplifier including an oscillator circuit that outputs a selectively variable oscillator output frequency dependent on and responsive to a variable oscillator input voltage, at least one tuning circuit that is tunable to a selectively variable tuning circuit frequency dependent on and responsive to a variable tuning voltage, and a memory, wherein said method comprises:

• a) for each one of said at least one tuning circuit, determining a respective mathematical equation defining said tuning voltage as a function of frequency, and storing equation data characterizing said respective mathematical equation in said memory;
• b) generating said oscillator input voltage with a proper oscillator voltage value dependent on said selected receiving frequency, and applying said oscillator input voltage to said oscillator circuit, such that said oscillator output frequency corresponds to or is frequency shifted from said selected receiving frequency;
• c) for each one of said at least one tuning circuit, calling up said equation data from said memory, and generating said tuning voltage with a proper tuning voltage value in accordance with said equation data characterizing said mathematical equation at said selected receiving frequency, and applying said tuning voltage with said proper tuning voltage value respectively to said at least one tuning circuit, such that said tuning circuit frequency corresponds to said selected receiving frequency.

A tunable multistage selective amplifier comprising:

• an oscillator circuit having an input adapted to receive a variable oscillator voltage and an output adapted to provide a variable oscillator frequency that is responsive to and dependent on said oscillator voltage,
• at least one tuning circuit having a signal input adapted to receive an input signal, a tuning input adapted to receive a variable tuning voltage, and an output adapted to provide an output signal derived from said input signal filtered by a variable receiving frequency that is responsive to and dependent on said tuning voltage,
• a phase-locked loop circuit having a control input adapted to receive a control signal, and an output adapted to provide said oscillator voltage responsive to and dependent on said control signal,
• a microprocessor connected to said control input of said phase-locked loop circuit and adapted to provide said control signal,
• a memory connected to said microprocessor and adapted to store therein and provide to said microprocessor a respective multiplicative coefficient and a respective additive factor for each said tuning circuit, and
• a respective multiplicative and additive amplifier circuit connected between said output of said phase-locked loop circuit and said tuning input of said tuning circuit, and connected at least indirectly to said memory to receive data characterizing said multiplicative coefficient and said additive factor, so as to receive said oscillator voltage and multiplicatively amplify said oscillator voltage by said multiplicative coefficient and additively increase said oscillator voltage by said additive factor and thereby to generate said tuning voltage.