Integrated phase locked loop local oscillator
First Claim
1. A dual-conversion super heterodyne receiver integrated circuit device, comprising:
- a radio frequency (RF) amplifier with selection means for receiving a first frequency (F1) carrier signal and a second frequency (F2) carrier signal;
a voltage controlled oscillator (VCO) for providing a first local oscillator (LO1) signal having a frequency of approximately (F1+F2) divided by two;
a first mixer having inputs connected to respective outputs of the RF amplifier and the VCO and an output for a first intermediate frequency signal;
frequency division means connected to an output of the VCO in a phase locked loop configuration and connected to derive a second local oscillator (LO2) signal from LO1 such that LO1 divided by LO2 equals "N.5", where "N" is a positive integer; and
a second mixer having inputs derived from respective outputs of the first mixer and the frequency division means and an output for a second intermediate frequency signal.
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Accused Products
Abstract
An embodiment of the present invention is a single-chip GPS receiver front-end comprising a radio frequency amplifier, a voltage-controlled oscillator operating at a first local oscillator frequency, a divide by seven and one-half counter for deriving a second local oscillator frequency from the first and a first and second mixer. The local oscillator frequency is mid-way between two carrier frequencies of interest that may be received by the radio frequency amplifier and the first mixer produces a first intermediate frequency. The second local oscillator frequency is then beat with the first intermediate frequency in the second mixer to produce a second intermediate frequency. A dual-conversion super heterodyne configuration is therefore employed in which the first and second local oscillator frequencies are derived from a single oscillator and the first local oscillator frequency is seven and one-half times the second local oscillator frequency.
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Citations
9 Claims
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1. A dual-conversion super heterodyne receiver integrated circuit device, comprising:
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a radio frequency (RF) amplifier with selection means for receiving a first frequency (F1) carrier signal and a second frequency (F2) carrier signal; a voltage controlled oscillator (VCO) for providing a first local oscillator (LO1) signal having a frequency of approximately (F1+F2) divided by two; a first mixer having inputs connected to respective outputs of the RF amplifier and the VCO and an output for a first intermediate frequency signal; frequency division means connected to an output of the VCO in a phase locked loop configuration and connected to derive a second local oscillator (LO2) signal from LO1 such that LO1 divided by LO2 equals "N.5", where "N" is a positive integer; and a second mixer having inputs derived from respective outputs of the first mixer and the frequency division means and an output for a second intermediate frequency signal. - View Dependent Claims (2, 3, 4)
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5. A dual-conversion super heterodyne receiver, comprising:
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a radio frequency (RF) amplifier; a first mixer coupled to an output of the RF amplifier for providing a first intermediate frequency output; a phase locked loop (PLL) including a voltage controlled oscillator (VCO) with an output connected to the first mixer, a numerical counter and a phase-frequency detector for comparing an output of said numerical counter to a reference frequency for phase locked loop operation; a divide by seven and one-half pulse-swallowing counter having an input connected to the PLL and a second local oscillator output for deriving a second local oscillator frequency one seven and a half part of said first local oscillator frequency; a second mixer having respective inputs connected to receive said first intermediate frequency from said first mixer and a second local oscillator signal from said second local oscillator output for providing an output for a second intermediate frequency; and an output stage with low-pass filtering and automatic gain control connected to said second intermediate frequency output of the second mixer.
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6. A voltage controlled oscillator (VCO), comprising:
a pair of cross-coupled amplification transistors provided for oscillator gain and a pair of feedback transistors each having its base tied to its emitter provided for capacitive positive feedback and respectively connected between the base of a first one and collector of a second one of said cross-coupled amplification transistors, wherein semiconductor process variations in the Miller capacitance of said amplification transistors is self-corrected by matching variations in the capacitance of said feedback transistors.
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7. A phase locked loop (PLL), comprising:
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a voltage controlled oscillator (VCO) with an astable multivibrator including a pair of cross-coupled amplification transistors provided for oscillator gain and a pair of feedback transistors each having its base tied to its emitter provided for capacitive positive feedback and respectively connected between the base of a first one and collector of a second one of said cross-coupled amplification transistors, wherein semiconductor process variations in the Miller capacitance of said amplification transistors is self-corrected by matching variations in the capacitance of said feedback transistors; a numeric counter means connected to divide down a sample of an output frequency produced by the VCO; and a phase-frequency detector connected to compare an output of the numeric counter to an externally provided reference frequency and connected to lock an operating frequency of the VCO to said reference frequency. - View Dependent Claims (8, 9)
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Specification