A wireless communication system, which is provided with a PLL circuit having a plurality of oscillators and is capable of processing two or more transmit and receive signal different in frequency band from one another according to the switching between the oscillators, has a reset means which resets a voltage applied to each of filter capacitors lying within the PLL circuit to a predetermined voltage when the switching between the oscillators is performed.

Wireless communication system

A phase locked loop (PLL) frequency synthesizer to produce a local oscillator signal for a superheterodyne transmitter for operation at a first and a second RF frequency band that are disparate. The transmitter has a fixed intermediate frequency that is a sizable fraction of the bandwidth of one or more of the RF bands. The superheterodyne transmitter includes a first and a second RF upconverter, each having a local oscillator input coupled to the frequency synthesizer. The synthesizer includes a voltage controlled oscillator (VCO) to provide a VCO frequency signal and a non-integer frequency multiplier to produce a frequency multiplied signal having a frequency wither at the VCO frequency or at a non-integer multiple of the VCO signal depending on a control input. The synthesizer further includes a programmable divider accepting the frequency multiplied signal and dividing the frequency of the by a settable amount, a phase detector to compare the phase of the output of the programmable divider to that of a reference oscillator and produce a phase difference signal; and a loop filter to filter a function of the phase difference to produce a control input to the VCO. The non-integer multiple is selected such that the frequency synthesizer can supply the local oscillator signal for both the first and second RF bands, such that the tuning range of the VCO is a relatively low fraction of the VCO frequency, and such that spurious mixer products do not fall in the frequency bands of operation.

Frequency synthesizer and synthesis method for generating a multiband local oscillator signal

A ratiometric clock system for an integrated receiver and associated method are disclosed that provide an advantageous solution for combining digital signal processing (DSP) circuitry on the same integrated circuit as mixer and local oscillator (LO) generation circuitry. The generation circuitry generates an oscillation signal that is passed through a first divider to generate mixing signals for the mixer and that is passed through a second divider to generate a digital clock signal that is utilized by the DSP circuitry. This digital clock signal can be utilized by integrated analog-to-digital conversion circuitry, as well.

Ratiometric clock systems for integrated receivers and associated methods

Systems and methods for providing support services to users of programmable devices are provided. One of many possible methods for providing support services for a plurality of programmable devices associated with a plurality of users involves the steps of: receiving user-specific data associated with one of the programmable devices and the corresponding user; storing the user-specific data associated with the programmable device and the corresponding user; receiving notification that a replacement programmable device for the programmable device is needed by the user; and configuring the replacement programmable device based on the user-specific data associated with the programmable device and the corresponding user. The method may further involve the steps of: providing the replacement programmable device to the user; receiving the programmable device; repairing the programmable device; providing the repaired programmable device to the user; receiving the replacement programmable device from the user; and receiving payment for providing the support services to the user.

Systems and methods for providing off-line backup of a programmable device's configuration data to users of programmable devices at a service location

A local oscillator apparatus is disclosed for use in radio frequency communication systems. The local oscillator apparatus comprises at least one mixer coupled to an oscillator input signal and to a feedback signal such that a local oscillator signal may be produced by fractional multiplication of the oscillator input signal. In an embodiment of the invention, the local oscillator apparatus includes a regenerative modulator comprising a pair of frequency dividers and a single side band mixer.

Local oscillator apparatus for radio frequency communication systems

A method and apparatus for generating two disparate frequency reference signals using a single phase locked loop. The circuit includes a local oscillator for generating a reference signal and a phase comparator for comparing the reference signal with a feedback signal. The output of the phase comparator is converted to a first one of the desired output frequencies by a voltage controlled oscillator. That signal is also fed to a variable frequency divider circuit under control of a Σ/Δ converter which generates a lower frequency signal without creating a secondary frequency tone. The lower frequency signal is the second of the output frequencies. This signal also is fed back to the second input of the phase comparator through a fixed frequency divider.

Hussein K. Mecklai

Papers

Phase locked loop for generating two disparate, variable frequency signals