Frequency Modulation Based on Two Path Modulation

摘要

A two path direct frequency modulation system is disclosed. The system includes a Varactor, a voltage-controlled oscillator (VCO) calibration capacitor bank including a first plurality of switchable capacitors, and a frequency deviation capacitor bank including a second plurality of switchable capacitors. The method includes switching on or off a number of the first plurality of switchable capacitors to obtain a desired frequency band and determining number of cycles within a first predetermined time to obtain a first count, switching on or off a number of the first plurality of switchable capacitors or of the second plurality of switchable capacitors to change the desired frequency band and determining number of cycles within a second predetermined time to obtain a second count, and modulating a data signal by switching on or off a switchable capacitors of the second plurality of switchable capacitors according to the first and the second count.

主权项

1. A two path direct frequency modulation system comprising:
a voltage controlled oscillator (VCO) comprising:
a frequency deviation capacitor bank including a first plurality of switchable capacitors; anda VCO calibration capacitor bank including a second plurality of switchable capacitors; a first path coupled to feed a digital control signal output from a baseband modulator to the first plurality of switchable capacitors and configured to control how many of the first plurality of switchable capacitors are turned on and how many of the first plurality of switchable capacitors are turned off; and a second path comprising a serially coupled a charge pump, a loop filter and a Varactor of the VCO configured to control how many of the second plurality of switchable capacitors are turned on and how many of the second plurality of switchable capacitors are turned off; wherein the VCO calibration capacitor bank determines VCO frequency and the frequency deviation capacitor bank determines data modulation.