Frequency synthesizer circuit for mobile stations
First Claim
1. A radio frequency (RF) transceiver comprising:
- a first oscillating means for generating a first local oscillator (LO) signal that is hopped between two different frequencies for transmitting and receiving, respectively, said first oscillating means including;
a main voltage controlled oscillator (VCO) for generating said first LO signal;
a programmable frequency divider for dividing said first LO signal;
a phase detector for comparing the output of said frequency divider to a reference frequency signal and for generating a tuning signal to said main VCO based on said comparison;
a loop filter at the input of said main VCO for filtering said timing signal; and
means for lowering the frequency of said first LO signal prior to being divided by said frequency divider such that the bandwidth of said loop filter can be selected so as to minimize the settling time of said main VCO without a concurrent increase in output noise when hopping the frequency of said first LO signal between the transmit and receive operations;
a second oscillating means for generating a second LO signal;
a first mixing means for combining said first LO signal with a received signal to produce a first intermediate frequency (IF) signal;
a second mixing means for combining said first IF signal with said second LO signal to produce a second IF signal;
frequency scaling means for scaling the frequency of said second LO signal to produce a transmit offset signal;
modulation means for modulating said transmit offset signal with a data signal; and
a third mixing means for combining said first LO signal with said data modulated signal to produce a transmit RF signal.
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Accused Products
Abstract
In general, the present invention provides a low cost mechanism for reducing the settling time and/or improving the phase noise performance of a frequency synthesizer in a mobile station. In one embodiment, the present invention eliminates the need for using two transmit offset synthesizers in a mobile station which must be able to operate on two different frequency bands characterized by different transmit-receive (TX-RX) channel separation. According to the present invention, one or both of the transmit offset synthesizers may be eliminated by deriving an appropriate transmit offset signal from an auxiliary synthesizer in the mobile station through a relatively simple and inexpensive frequency scaling circuit (e.g., frequency divider or multiplier), and by using a fast settling main channel synthesizer to hop between two different frequencies when the mobile station is switching between transmitting and receiving, respectively.
56 Citations
32 Claims
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1. A radio frequency (RF) transceiver comprising:
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a first oscillating means for generating a first local oscillator (LO) signal that is hopped between two different frequencies for transmitting and receiving, respectively, said first oscillating means including; a main voltage controlled oscillator (VCO) for generating said first LO signal; a programmable frequency divider for dividing said first LO signal; a phase detector for comparing the output of said frequency divider to a reference frequency signal and for generating a tuning signal to said main VCO based on said comparison; a loop filter at the input of said main VCO for filtering said timing signal; and means for lowering the frequency of said first LO signal prior to being divided by said frequency divider such that the bandwidth of said loop filter can be selected so as to minimize the settling time of said main VCO without a concurrent increase in output noise when hopping the frequency of said first LO signal between the transmit and receive operations; a second oscillating means for generating a second LO signal; a first mixing means for combining said first LO signal with a received signal to produce a first intermediate frequency (IF) signal; a second mixing means for combining said first IF signal with said second LO signal to produce a second IF signal; frequency scaling means for scaling the frequency of said second LO signal to produce a transmit offset signal; modulation means for modulating said transmit offset signal with a data signal; and a third mixing means for combining said first LO signal with said data modulated signal to produce a transmit RF signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A mobile station comprising:
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means for receiving a radio frequency (RF) signal; means for processing an analog signal into a data signal; a main channel synthesizer for generating a first local oscillator (LO) signal that is hopped between two different frequencies for transmitting and receiving, respectively, said main channel synthesizer including; a main voltage controlled oscillator (VCO) for generating said first LO signal; a programmable frequency divider for dividing said first LO signal; a phase detector for comparing the output of said frequency divider to a reference frequency signal and for generating a tuning signal to said main VCO based on said comparison; a loop filter at the input of said main VCO for filtering said tuning signal; and means for lowering the frequency of said first LO signal prior to being divided by said frequency divider such that the bandwidth of said loop filter can be selected so as to minimize the settling time of said main VCO without a concurrent increase in output noise when hopping the frequency of said first LO signal between the transmit and receive operations; an auxiliary synthesizer for generating a second LO signal; a first mixing means for combining said first LO signal with said received RF signal to produce a first intermediate frequency (IF) signal; a second mixing means for combining said first IF signal with said second LO signal to produce a second IF signal; frequency scaling means for scaling the frequency of said second LO signal to produce a transmit offset signal; modulation means for modulating said transmit offset signal with said data signal; and a third mixing means for combining said first LO signal with said data modulated signal to produce a transmit RF signal. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method for transceiving radio frequency (RF) signals in a mobile station comprising the steps of:
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generating a first local oscillator (LO) signal that is hopped between two different frequencies for transmitting and receiving, respectively, said first LO signal being generated in a voltage controlled oscillator (VCO) that is in a phase locked loop (PLL) with a frequency divider, a phase detector and a loop filter; lowering the frequency of said first LO signal prior to being divided by said frequency divider such that the bandwidth of said loop filter can be selected so as to minimize the settling time of said VCO without a concurrent increase in output noise when hopping the frequency of said first LO signal between the transmit and receive operations; generating a second LO signal; mixing said first LO signal with a received RF signal to produce a first intermediate frequency (IF) signal; mixing said first IF signal with said second LO signal to produce a second IF signal; scaling the frequency of said second LO signal to produce a transmit offset signal; modulating said transmit offset signal with a data signal; and mixing said first LO signal with said data modulated signal to produce a transmit RF signal. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32)
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Specification