Extended range voltage controlled oscillator for frequency synthesis in

Abstract

An improved DBS receiver front end architecture having a voltage controlled oscillator for frequency synthesis. The voltage controlled oscillator includes a tank circuit having an adjustable resonance frequency which may be varied over an octave. A tuning oscillator drives the tank circuit and provides a signal having that resonance frequency to a range extender which provides a tuning frequency. When enabled, the range extender doubles the input frequency, and when disabled, simply passes the input frequency through. A feedback path provides a control voltage to the tank circuit to adjust the resonance frequency and thereby cause the tuning frequency to be a multiple of a reference frequency. The range extender extends the tuning frequency range over two octaves without a loss of frequency resolution. Broadly speaking, the present invention contemplates a DBS receiver front end which includes a tuner chip and a demodulator/decoder chip. The tuner chip has a frequency doubler which provides a tuning frequency signal having a frequency twice that of an input frequency signal when the doubler is enabled, and a tuning frequency signal having a frequency equal that of an input frequency signal when the doubler is disabled. The tuner chip also has a tuning oscillator which provides the input frequency, and a downconverter coupled to receive the tuning frequency signal. The downconverter further receives a receive signal and responsively provides a product signal which is then converted to a baseband signal. The demodulator/decoder chip is configured to control the input frequency to the doubler, and further configured to convert the baseband signal to a decoded signal.