FM composite signal processor
AssigneeSolid Electronics Labs
InventorStephen J. Hemphill
Life of this patent
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Abstract
A signal processor for amplitude and frequency limiting of a multiplex FM composite signal is described. To maximize the amount of available bandwidth and minimize the generated distortion, the disclosed signal processor employs multiple low-distortion amplifying and clipping subsystems. The subsystems include a stereophonic pilot signal protection circuit which protects the 19 khz pilot signal from the composite FM signal processing, an adjustable limiting circuit, and an adjustable dual low-pass filter/overshoot compensation circuit.
Claims21
A signal processor for use in preparation of a modulated signal to be broadcast comprising:
- a modulated signal;
- and,
- a clipping amplifier comprising:
- a first low-pass filter, having a first transfer function, receiving the modulated signal;
- and
- a first overshoot compensator removing any modulation above a predetermined maximum modulation created by said first low-pass filter;
- and
- a first circuit receiving an input signal having a pilot subcarrier and the modulated signal, said first circuit separating the pilot subcarrier from the input signal and outputting the modulated signal to said clipping amplifier, said first circuit recombining the pilot subcarrier with the output of said clipping amplifier.
In a signal processor preparing a complex signal to be broadcast comprising, a circuit for protecting a pilot signal in a complex signal comprising:
- separating means for separating out the pilot signal;
- inverting means, receiving the pilot signal from said separating means, for reversing the phase of the pilot signal;
- a summing circuit combining the complex signal with the output of said inverting means to remove the pilot signal from the complex signal;
- processing means for processing the output from said summing circuit;
- restoring means for restoring the pilot signal with the output of the processing means.
In a signal processor preparing a modulated signal to be broadcast comprising, a circuit for limiting the modulation of a modulated signal comprising:
- a clipper amplifier receiving the modulated signal, said clipper operating between a predetermined high voltage and a predetermined low voltage;
- adjusting means adjusting the predetermined high voltage and the predetermined low voltage;
- setting means for setting one of the predetermined high voltage and the predetermined low voltage;
- an inverting circuit for inverting said one of the predetermined high voltage and the predetermined low voltage and outputting the other one of the predetermined high voltage and the predetermined low voltage;
- and,
- a balance circuit connected across said inverting circuit adjusting the balance between the predetermined high voltage and the predetermined low voltage.
Dependencies are inferred from the claim text.