Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
  • H03D3/00—Demodulation of angle-, frequency- or phase- modulated oscillations
  • H03D3/02—Demodulation of angle-, frequency- or phase- modulated oscillations by detecting phase difference between two signals obtained from input signal
  • H03D3/24—Modifications of demodulators to reject or remove amplitude variations by means of locked-in oscillator circuits
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
  • H03L7/00—Automatic control of frequency or phase; Synchronisation
  • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
  • H03L7/08—Details of the phase-locked loop
  • H03L7/099—Details of the phase-locked loop concerning mainly the controlled oscillator of the loop
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
  • H03L5/00—Automatic control of voltage, current, or power
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
  • H03L7/00—Automatic control of frequency or phase; Synchronisation
  • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
  • H03L7/08—Details of the phase-locked loop
  • H03L7/085—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal
  • H03L7/087—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal using at least two phase detectors or a frequency and phase detector in the loop
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
  • H03L7/00—Automatic control of frequency or phase; Synchronisation
  • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
  • H03L7/08—Details of the phase-locked loop
  • H03L7/10—Details of the phase-locked loop for assuring initial synchronisation or for broadening the capture range
  • H03L7/113—Details of the phase-locked loop for assuring initial synchronisation or for broadening the capture range using frequency discriminator
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
  • H03B2201/00—Aspects of oscillators relating to varying the frequency of the oscillations
  • H03B2201/02—Varying the frequency of the oscillations by electronic means
  • H03B2201/025—Varying the frequency of the oscillations by electronic means the means being an electronic switch for switching in or out oscillator elements
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
  • H03B2201/00—Aspects of oscillators relating to varying the frequency of the oscillations
  • H03B2201/02—Varying the frequency of the oscillations by electronic means
  • H03B2201/0275—Varying the frequency of the oscillations by electronic means the means delivering several selected voltages or currents
  • H03B2201/0283—Varying the frequency of the oscillations by electronic means the means delivering several selected voltages or currents the means functioning digitally
  • H03B2201/0291—Varying the frequency of the oscillations by electronic means the means delivering several selected voltages or currents the means functioning digitally and being controlled by a processing device, e.g. a microprocessor
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
  • H03J2200/00—Indexing scheme relating to tuning resonant circuits and selecting resonant circuits
  • H03J2200/10—Tuning of a resonator by means of digitally controlled capacitor bank

Definitions

• Frequency synthesizers are regularly employed in communication transceivers used in numerous types of communication systems and communication technologies, such as, radio frequency communication systems.
• a phase-locked loop to precisely control the frequency of the output signal of a voltage-controlled oscillator (VCO).
• VCO voltage-controlled oscillator
• the frequency synthesizer typically consists of a VCO, a low pass filter, and a phase-locked loop.
• the VCO generates an output signal having a particular frequency.
• a phase detector in the phase-locked loop receives the output signal and compares the output signal to a reference frequency. Based on the comparison of the output signal to the reference frequency, the phase-locked loop generates a control signal that is provided to the low pass filter and then to the VCO.
• the invention also provides related methods of operation and computer readable media.
• Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims.
• Communication device 100 may also be a multi-band communication device capable of communicating with multiple wireless communication systems.
• communication device 100 receives and transmits broadband signals, such as, for example, radio frequency signals, from and to the communication system via antenna 102.
• broadband signals such as, for example, radio frequency signals
• a broadband signal received by communication device 100 via antenna 102 is communicated to duplex filter 104.
• Duplex filter 104 receives signals from the communication system and communicates them via connection 126 to amplifier 106.
• Amplifier 106 provides an amplified signal to band pass filter 108 via connection 128.
• Band pass filter 108 passes frequencies within the range of frequencies associated with the communication systems with which communication device 100 communicates to mixer 1 10 via connection 130. Frequencies outside this range are attenuated.
• Mixer 110 receives a signal from frequency synthesizer 112 via connection 132, mixes it with the signal received via connection 130, and provides a signal to processor 114 via connection 134.
• Processor 114 processes the signal received via connection 134 and, where the signal is an audio signal, may provide the resulting signal to speaker 122.
• processor 114 may provide a data signal to a user interface, such as, for example, a liquid crystal display or other display device.
• each of the switched capacitors may be engaged or disengaged, there are eight possible binary configurations for the switched capacitors, with each configuration producing a distinct frequency for the output signal of controllable oscillator 202.
• each distinct ** frequency for the output signal of controllable oscillator 202 may be defined as a function of the component values for inductor 400 (L), variable capacitor 402 (C var ), and switched capacitors 404 (C 0 ), 406 (Ci), and 408 (C n ) and binary weighting coefficients bo, bi and b n , where f co is the frequency of the output signal of controllable oscillator 202:
• the number of switched capacitors also defines the number of control lines required between frequency control circuit 208 and controllable oscillator 202. For example, if there are three switched capacitors to be engaged or disengaged, frequency control circuit 208 may use three control lines (one control line for each switched capacitor). For example, referring to FIGS. 3 and 4, at block 304, frequency circuit 208 may determine that for a 3-bit system the frequency of the output signal of controllable oscillator 202 best approximates the predefined frequency where switched capacitor 404 is engaged, switched capacitor 406 is disengaged, and switched capacitor 408 is engaged. Accordingly, at block 306, frequency control circuit 208 may generate three control signals. A first control signal 410 corresponding to switched capacitor 404 may be configured to engage switched capacitor 404.
• controllable oscillator 202 may be further controlled by varying the control signal applied to variable capacitor 402 on connection 242.
• FIG. 7 is a tree state diagram of binary state search module 508 of FIG. 5.
• the binary tree comprises leaf nodes 700, intermediate nodes 702, and root node 704.
• Root node 704 represents the initial binary state that corresponds to the initial operational state of controllable oscillator 202 prior to the operation of frequency control* circuit 208.
• Intermediate nodes 702 represent the set of intermediate binary states corresponding to the possible operational states that controllable oscillator 202 may occupy during the operation of frequency control circuit 208.
• Leaf nodes 700 designate the final binary states corresponding to the plurality of operational states of controllable oscillator 202.
• binary state search module 508 may use the binary tree to search the plurality of operational states of controllable oscillator 202 and determine
• binary state search module 508 selects one of the two intermediate nodes 702 linked to root node 704.
• the two intermediate nodes 702 linked to root node 704 represent the two next operational states (010, 110 in the example of FIG. 7) for controllable oscillator 202.
• Binary state search module 508 may be configured so that the two next operational states for root 0 node 704 and intermediate nodes 702 are defined by the following equation, where M new represents the next operational state and M represents the current operational state:
• FIG. 8 illustrates a block diagram of another of a number of embodiments of the frequency synthesizer of FIG. 1.
• Frequency synthesizer 800 comprises a controllable oscillator 202, a low pass filter 204, a phase-locked loop 206, a frequency control circuit 208, an R-divider circuit 210, a serial port 212, and an amplitude control circuit 802.
• amplitude control circuit 802 may be enabled.
• controllable oscillator 202 may be further configured to have a plurality of operational states in which each of the operational states corresponds to a distinct amplitude for the output signal of controllable oscillator 202.
• the amplitude of the output signal of controllable oscillator 202 may be maintained throughout the frequency range by changing the operational state of controllable oscillator 202 and thereby changing the corresponding amplitude for the output signal.
• FIG. 9 is a flow chart 900 illustrating the architecture and operation of one of a number of embodiments of amplitude control circuit 802 of FIG. 8.
• amplitude control circuit 802 receives information associated with a predefined amplitude level for the output, signal of controllable oscillator 202.
• the information may define a minimum amplitude level above which the amplitude of the output signal of controllable oscillator 202 should be maintained.
• the information may also be represented as an amplitude range in which the amplitude of the output signal should be maintained.
• the important aspect of amplitude control circuit 802 is that it receives information for maintaining or controlling the amplitude level of the output signal of controllable oscillator 202.
• the information associated with the predefined amplitude level may be received from serial port 212 or any other component not shown in FIG. 8. The information may even be contained in memory within amplitude control circuit 802.
• amplitude control circuit 802 determines the amplitude of the output signal of controllable oscillator 202.
• amplitude control circuit 802 may be enabled to adjust the amplitude of the output signal. This interaction between frequency control circuit 208 and amplitude control circuit 802 may be controlled by tiL i g signals communicated via connection 805 (FIG. 8). In other embodiments of frequency synthesizer 800, there may be no frequency control circuit 208, in which case amplitude control circuit 802 responds to frequency changes produced by phase-locked loop 206.
• FIG. 10 illustrates a block diagram of one of a number of embodiments of a controllable oscillator 1002 for implementing the plurality of operational states and corresponding distinct amplitudes for the output signal, which are controlled by amplitude control circuit 802.
• Controllable oscillator 1002 may comprise a plurality of switched current sources 1000 connected in parallel. Switched current sources 1000 receive the control signal from amplitude control circuit 802 on connection 806. In response to the control signal, switched current sources 1000 are engaged or disengaged in a predetermined manner corresponding to one of the operational states of controllable oscillator 1002.
• the number of switched current sources 1000 also defines the number of control lines required for amplitude control circuit 802 to control controllable oscillator 1002. For example, if there are three switched current sources 1000 to be engaged or disengaged, amplitude control circuit 802 may use three control (one control line for each switched current source 1000). Amplitude control circuit 802 controls the operational state of controllable oscillator 1002 in the same manner as described above with respect to frequency control circuit 208.
• FIG. 11 illustrates a block diagram of one of a number of embodiments of amplitude control circuit 802 for maintaining the amplitude of the output signal of controllable oscillator 1002. Amplitude control circuit 802 may comprise peak detector 1 100, low pass filter 1102, amplifier 1 104, and binary state search module 1106.
• peak detector 1100 receives the output signal of controllable oscillator 1002 on connection 804. Peak detector 1 100 determines the amplitude of the output signal and provides the information on connection 1108 to low pass filter 1102 where the signal is filtered. The filtered signal is provided on connection 1 110 to amplifier 1104. Amplifier 1104 compares the information associated with the amplitude of the output signal of controllable oscillator 202 to a reference voltage 1112 and provides a control bit on connection 1 1 14 to binary state search module 1 106.
• FIGS. 3, 6, and 9 should be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps in the process, and alternate implementations are included within the scope of the preferred embodiment of the present invention in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art.
• frequency synthesizers 112 and 800, frequency control circuit 208, and amplitude control circuit 802 which may comprise an ordered listing of executable instructions for implementing logical functions, can be embodied in any computer readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions.
• a "computer readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
• the computer readable medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples (a nonexhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic) having one or more wires, a portable computer diskette (magnetic), a random access memory (RAM) (electronic), a' read-only memory (ROM) (electronic), an erasable programmable read-only memory (EPROM or Flash memory) (electronic), an optical fiber (optical), and a portable compact disc read-only memory (CDROM) (optical).
• an electrical connection having one or more wires
• a portable computer diskette magnetic
• RAM random access memory
• ROM read-only memory
• EPROM or Flash memory erasable programmable read-only memory
• CDROM portable compact disc read-only memory

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)
• Transceivers (AREA)
• Channel Selection Circuits, Automatic Tuning Circuits (AREA)
• Inductance-Capacitance Distribution Constants And Capacitance-Resistance Oscillators (AREA)

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