Fast Hopping Frequency Synthesizer

• US 20090088113A1
• Filed: 09/27/2007
• Published: 04/02/2009
• Est. Priority Date: 09/27/2007
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Toso, Sterano Dal, Bevilacqua, Andrea, Tiebout, Marc, Marsili, Stefano
• Granted Patent: US 7,940,830 B2
• Time in Patent Office: Days
• US Class Current: 455/260
• CPC Class Codes: H03L 7/06 using a reference signal applied to a frequency- or phase-locked loop
• CPC Class Codes: H04B 1/7136 Arrangements for generation of hop frequencies, e.g. using a bank of frequency sources, using continuous tuning or using a transform
• CPC Class Codes: H04B 2001/71362 using a bank of frequency sources

Abstract

Apparatus and systems for synthesizing frequencies for use in a fast hopping wireless communications system. A frequency synthesizer comprises a plurality of oscillators with each oscillator having a first input coupled to a reference clock frequency signal, and a signal selector having a control signal input and a plurality of reference clock inputs with each reference clock input coupled to an output from an oscillator. Each oscillator produces a reference frequency that is a harmonic of a reference clock frequency of the reference clock frequency signal, and the signal selector couples a reference clock input to an output based on a control signal provided by the control signal input.

Claims

1. A frequency synthesizer for use in a fast frequency hopping communications device, the frequency synthesizer comprising:

a plurality of oscillators, each oscillator having a first input coupled to a reference clock frequency signal, the oscillator configured to produce a reference frequency that is a harmonic of a reference clock frequency of the reference clock frequency signal; and

a signal selector having a control signal input and a plurality of reference clock inputs, each reference clock input coupled to an output from an oscillator in the plurality of oscillators, the signal selector to couple a reference clock input to an output based on a control signal provided by the control signal input.

2. The frequency synthesizer of claim 1, wherein each oscillator in the plurality of oscillators comprises an injection locked oscillator.

3. The frequency synthesizer of claim 2, wherein the reference clock frequency comprises a signal with the reference clock frequency and harmonics of the reference clock frequency, and wherein each injection locked oscillator locks onto a unique harmonic of the reference clock frequency.

4. The frequency synthesizer of claim 2, wherein each injection locked oscillator comprises a quadrature injection locked oscillator, the quadrature injection locked oscillator to produce two reference frequencies having substantially equal frequencies that are ninety degrees out of phase.

5. The frequency synthesizer of claim 2, further comprising a clock divider coupled to the output of the signal selector, the clock divider to produce two reference frequencies having substantially equal frequencies that is a reference frequency produced by an oscillator selected by the signal selector divided by n (where n is the divisor of the clock divider), wherein the two reference frequencies are about ninety degrees out of phase.

6. The frequency synthesizer of claim 5, wherein the reference clock frequency signal is an integral multiple of the reference clock frequency, and wherein the integral multiple and n are multiplicative inverses.

7. The frequency synthesizer of claim 1, wherein each oscillator in the plurality of oscillators comprises a frequency multiplier, and wherein each frequency multiplier produces a unique multiple of the reference clock frequency.

8. The frequency synthesizer of claim 1, wherein the fast frequency hopping communications device communicates using several groups of frequency bands, with each group of frequency bands having a different reference clock frequency, wherein the plurality of oscillators is partitioned into several groups of oscillators, one group of oscillators per group of frequency bands, and wherein each group of oscillators is coupled to a different reference clock frequency signal.

9. The frequency synthesizer of claim 1, wherein the reference clock signal frequency signal comprises only even or odd harmonics of the reference clock frequency.

10. The frequency synthesizer of claim 9, further comprising a pulse generator having a reference clock signal input and a modulating sequence input, the pulse generator to modulate the reference clock frequency with a modulating sequence to produce the reference clock frequency signal.

11. The frequency synthesizer of claim 10, wherein the modulating sequence comprises a sequence of alternating a +voltage value and a −

voltage value, and wherein the reference clock frequency signal comprises odd harmonics of the reference clock frequency.

12. The frequency synthesizer of claim 10, wherein the modulating sequence comprises a sequence of a +voltage value, and wherein the reference clock frequency signal comprises even harmonics of the reference clock frequency.

13. The frequency synthesizer of claim 9, further comprising a high pass filter coupled to a clock signal input providing a clock signal with a frequency about two times the reference clock frequency.

14. The frequency synthesizer of claim 1, wherein the frequency synthesizer is used in a WiMedia compliant communications device, and wherein the reference clock frequency is about equal to an integer multiple of 264 MHz.

15. The frequency synthesizer of claim 1, wherein each oscillator is an LC oscillator.

16. A fast hopping communications device comprising a receiver to receive transmissions over multiple frequency bands, the receiver comprising:

a first amplifier coupled to a radio frequency input, the first amplifier to change a signal level of a radio frequency signal provided by the radio frequency input to create an amplified radio frequency signal;

a frequency synthesizer to produce a receiver reference frequency for a frequency band over which the radio frequency signal is being received, the frequency synthesizer comprising

a plurality of oscillators, one oscillator per frequency band, each oscillator coupled to a reference clock frequency signal input, the oscillator to produce a reference frequency that is a harmonic of a reference clock frequency of a reference clock frequency signal provided by the reference clock frequency signal input, and

a first multiplexer having a first control signal input and a plurality of first reference clock inputs, each first reference clock input coupled to an output from an oscillator in the plurality of oscillators, the first multiplexer to couple a reference clock input to an output based on a first control signal provided by the first control signal input;

a first mixer coupled to the first amplifier and to the frequency synthesizer, the first mixer to remove a carrier frequency at the receiver reference frequency from the amplified radio frequency signal; and

a first filter coupled to the first mixer, the first filter to eliminate signals outside of a specified frequency range to produce an incoming baseband signal.

17. The fast hopping communications device of claim 16, further comprising a transmitter to transmit transmissions over multiple frequency bands, the transmitter comprising:

a second amplifier coupled to an outgoing baseband signal input, the second amplifier to change a signal level of an outgoing baseband signal provided by the outgoing baseband signal input;

a second filter coupled to the second amplifier, the second filter to eliminate signals outside of the specified frequency range to produce a filtered outgoing baseband signal;

a second multiplexer having a second control signal input and a plurality of second reference clock inputs, each second reference clock input coupled to an output from an oscillator in the plurality of oscillators, the second multiplexer to couple a second reference clock input to an output based on a second control signal provided by the second control signal input to produce a transmitter reference frequency; and

a second mixer coupled to the second filter, the second mixer to move the filtered outgoing baseband signal into a frequency band with a center frequency located at about the transmitter reference frequency.

18. The fast hopping communications device of claim 17, wherein the fast hopping communications device is a WiMedia compliant communications device.

19. A digitally controlled frequency synthesizer for use in a fast frequency hopping communications device, the digitally controlled frequency synthesizer comprising:

a digitally controlled capacitor array to provide a capacitive load dependent on a control word; and

an LC oscillator coupled to the digitally controlled capacitor array and to a reference signal input, the LC oscillator to produce a signal at about an integer multiple of the reference frequency that is a function of the capacitive load provided by the digitally controlled capacitor array.

20. The digitally controlled frequency synthesizer of claim 19, wherein the digitally controlled capacitor array comprises:

a plurality of capacitors arranged in parallel; and

a plurality of switches, each switch arranged in series with a capacitor in the plurality of capacitors, each switch coupled to a control word input with each switch'"'"'s state dependent on a value of the control word.