Title of Invention

LOCAL OSCILLATOR LEAKAGE CONTROL IN DIRECT CONVERSION PROCESSES

Abstract

A system and method for generating a local oscillator (LO) frequency in a zero intermediate frequency (IF) receiver or transmitter is presented. A signal is received from a voltage controlled oscillator (VCO). The signal has a VCO frequency. The VCO frequency is divided by a number N to produce a signal having a divided-down frequency. The signal having the VCO frequency is then mixed with the signal having the divided-down frequency to produce an output signal having an output frequency. Local oscillator leakage is reduced. Thus, the receiver or transmitter may operate in multiple wireless communication bands and modes and meet the associated specifications. Fig. 7

Full Text

LOCAL OSCILLATOR LEAKAGE CONTROL IN DIRECT CONVERSION PROCESSES BACKGROUND Field [0001] This invention relates in general to wireless communications. Specifically, this invention relates to systems and methods for direct conversion transceivers. Background and Belated Art [0002] The field of communications has experienced a tremendous growth due in large part to the improved capabilities of wireless devices. Wireless devices employ radio waves to enable distant communications without the physical constraints of wire-bascd systems, Information, such as voice, data, or paging information, is conveyed by radio waves transmitted over predetermined frequency bands. Allocation of available frequency spectra is regulated to ensure that numerous users may communicate without undue interference. [0003] Information to be transmitted from a source to. a destination is seldom acquired in a format that is ready for radio transmission. Typically, a transmitter takes an input signal and formats it for transmission in a predetermined frequency band. The input signal, also referred to as a baseband signal, modulates a earner in the desired frequency band. For -Example, a radio transmitter that receives an audio input signal modulates a carrier frequency with the input signal. [01)041 A corresponding remote receiver tuned to the same carrier frequency as the transmitter must receive and demodulate the transmitted signal. That is, the remote receiver most recover the baseband signal from the modulated carrier. The baseband signal may be directly presented to a user or may be farther processed prior to being presented to the user Many consumer wireless devices, such as radios, televisions, and pagers, are solely receivers. 10005] Transceivers are wireless devices that integrate a transmitter and receiver in a single package- Transceivers enable nearly instantaneous two-way communications. [0010] Intemodulation distortion is the result of two or more signals mixing together to produce additional unwanted distortion within the signal bandwidth. For two produce uudesired signals, such as DC signal levels that are proportional to the amplitude modulation (AM) component of the jammer signal. AM jammer signals may be located at any frequency within a receive frequency band. receive frequncy band is 869-894 MHz, and the associated transmit frequency band is 824-849 MHz, Similarly, receive and transmit frequency bands are allocated to Japan Cellular, IMT, and Korean PCS. (0020] Communications standards set forth specifications that wireless communication devices must meet. For instance, spurious emissions, sensitivity, jamming range and current consumption for elements in receiver 101 after IF filters 70, In addition, phase and amplitude matching between the I and Q channels 106,107 may be achieved more easily because the IF signal is at a lower frequency range. In view of these benefits receiver 10;. is well-suited for multi-mode and multi-band applications, wherein received receiver 200, the received RF signal is mixed with a local oscillator (LO) frequency to produce a baseband signal Because it does not incorpoiate an IF signal path, receiver 200 eliminates cost, board area, and power consumption associated with IF componentSt which mclude IF S AWs, LC matching and discrete filters, a pre-amp, AGC, IF mixers, and the IF VCO and PLL. Further, less part-to-part and temperature variation occurs. [0027A] WO 00/52840 describes a multi-band transceiver utilizing a direct conversion receiver. The direct conversion receiver generates a local oscillator signal by filtering a voltage controlled oscillator (VCO) signal using a low pass filter, or by doubling the VCO signal in frequency, and passing the result through a low pass filter. [0031] In CDMA, sensitivity is tested with a signal, set to a level such that a certain frame error rate (FER) is met. IS-98 specifies that the device under test must meet a [0034] Therefore, what is needed is a direct conversion transceiver that can modulate RF signals in multiple bands and multiple modes. [0038] The features, objects, and advantages of the disclosed embodiments will become mors apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout, and wherein: that outputs a signal whose frequency is a divided down version of an input signal For instance, divider 430 may divide by an integer N, wherein the value of N may be set by a control signa.. [0103] The foregoing detailed description refers to the accompanying drawings that illustrate exemplary embodiments of the present inventions. Other embodiments are possible and modifications may be made to the embodiments without ieparting from the spirit and scope of the invention. For mstance, many of the above devices; may be indirectly coupled to one another such that the devices are separated by intermediate devices, such as filters or amplifiers. Moreover, the teachings of the present invention may be applied to future-developed modulation standards and operating bands. Therefore, the detailed description is not meant to limit the invention. Rather, the scope of the invention is defined by the appended claims. WE CLAIM: 1. A method for generating a local oscillator (LO) frequency in a multi-band direct conversion wireless communication device, the method comprising: receiving a first signal, from a voltage controlled oscillator (VCO) (420), having a VCO frequency; characterised by: dividing the first signal in frequency by a number N to produce a second signal having a divided down frequency; and mixing the first signal with the second signal to produce an output signal having the LO frequency. 2. The method as claimed in claim 1, comprising dividing the output signal in frequency by a number M. 3. The method as claimed in claim 1, comprising shifting the phase of the output signal. 4. The method as claimed in claim 1, wherein the frequency of the first signal is divided by N when a control signal is received. 5. The method as claimed in claim 1, wherein the device comprises a receiver. 6. The method as claimed in claim 1, comprising mixing the output signal with a third signal having an offset frequency to produce a forth signal for a transmitter. 7. The method as claimed in claim 1, wherein the device comprises a transmitter. 8. A method for generating a local oscillator (LO) frequency in a multi-band direct conversion wireless communication device, the method comprising: receiving a first signal, from a voltage controlled oscillator (VCO), having a VCO frequency; characterised by: dividing the first signal in frequency by a number N to produce a second signal having a divided down frequency; dividing the second signal in frequency by a number M to produce a third signal having a divided-down frequency; and mixing the second signal with the third signal to produce an output signal having the LO frequency. 9. The method as claimed in claim 9, comprising dividing the output signal in frequency by a number P. 10. The method as claimed in claim 9, wherein the VCO is a multi-band VCO. 11. The method as claimed in claim 1, comprising: configuring an LO generator to have one or more configurations, each configuration being associated with at least one frequency band of RF signals and producing an output signal whose frequency is associated with the at least one frequency band of RF signals, and to mix a VCO frequency with a divided-down version of the VCO frequency; choosing a frequency band of RF signals; and selecting a configuration of an LO generator associated with the chosen frequency band of RF signals, the LO generator having one or more configurations, each configuration being associated with at least one frequency band of RF signals and producing an output signal whose frequency is associated with the at least one frequency band of RF signals. 12. The method as claimed in claim 11, comprising controlling the LO generator based on the selecting. 13. A system for generating a local oscillator (LO) frequency in a multi-band direct conversion wireless communication device, the system comprising: a voltage controlled oscillator (VCO)(420); characterised by: a divider (430) having an input and an output produced by dividing an input signal, the divider input being operatively coupled to the VCO; and a mixer (450) having a first mixer input operatively coupled to the VCO, a second mixer input operatively coupled to the divider output, and an output providing the LO frequency. 14. The system as claimed in claim 13, wherein the VCO is external to a chip that comprises the device. 15. The system as claimed in claim 14, wherein the VCO has a single-ended output. 16. The system as claimed in claim 13, wherein the VCO is integrated in a chip that comprises the device. 17. The system as claimed in claim 13, wherein the VCO operates below a frequency of RF signals. 18. The system as claimed in claim 13, wherein the VCO operates above a frequency of RF signals. 19. The system as claimed in claim 13, wherein the VCO operates at frequencies between 1600 and 1788MHz. 20. The system as claimed in claim 13, wherein the VCO is operatively coupled to a phaselocked loop (PLL)(410), comprising a second PLL and a second VCO for signals received when in a GPS mode, the second VCO operating at two times the frequency of received GPS signals. 21. The system as claimed in claim 20, comprising a third PLL and a third VCO for signals received when in a Bluetooth mode. 22. The system as claimed in claim 13, wherein the mixer comprises a single side band (SSB) mixer. 23. The system as claimed in claim 22, wherein the SSB mixer is a low side SSB mixer. 24. The system as claimed in claim 22, wherein the SSB mixer is a high side SSB mixer. 25. The system as claimed in claim 13, wherein the mixer output is operatively coupled to a phase-locked loop(PLL), wherein the PLL is internal to a chip that comprises the device. 26. The system as claimed in claim 13, wherein the divider input is selectively coupled to the VCO. 27. The system as claimed in claim 26, wherein a switch (440) selectively couples the divider input to the VCO. 28. The system as claimed in claim 27, wherein the switch is controlled by a switch control based on a band of the RF signals. 29. The system as claimed in claim 13, wherein the divider input is selectively coupled to the mixer output. 30. The system as claimed in claim 13, wherein the mixer output is selectively coupled to the VCO. 31. The system as claimed in claim 13, comprising a phase shifter having an input coupled to the mixer output, the phase shifter having an output that produces quadrature signals. 32. The system as claimed in claim 31, wherein the phase shifter comprises an active phase shifter. 33. The system as claimed in claim 13, comprising a second divider (470) having an input operatively coupled to the mixer output and an output produced by dividing an input signal. 34. The system as claimed in claim 33, wherein the second divider divides by 2. 35. The system as claimed in claim 33, wherein the second divider outputs a first signal and a second signal, the first signal being 90 degrees out of phase of the second signal. 36. The system as claimed in claim 35, wherein the first signal drives one of an I mixer and a Q mixer in the device. 37. The system as claimed in claim 13, wherein the device comprises a receiver, wherein a fi-equency band of received RF signals is US Personal Communications System (PCS), and wherein: the VCO operates between frequencies of 1716 MHz and 1769 MHz, the divider divides by 8, and the mixer is a high side single side band (SSB) mixer. 38. The system as claimed in claim 14, wherein the device comprises a receiver, wherein a band of received RF signals is Intemational Telecommunications Union (IMT), and wherein: the VCO operates between frequencies of 1688 MHz and 1736 MHz, the divider divides by 4, and the mixer is a high side single side band (SSB) mixer. 39. The system as claimed in claim 13, wherein the device is comprised in a wireless communication transceiver. 40. The system as claimed in claim 13, wherein the device comprises a transmitter. 41. The system as claimed in claim 40, wherein a frequency band of transmitted RF signals is US Personal Communications System (PCS), and wherein: the VCO operates at frequencies between 1480 MHz and 1528 MHz, the divider divides by 4, and the mixer is a high side single side band (SSB) mixer. 42. The system as claimed in claim 40, comprising a first amplifier chain configured to operate in a first transmit frequency band, the amplifier chain being operatively coupled to an upconverter. 43. The system as claimed in claim 13, wherein the device comprises a receiver, and comprising an offset LO coupled to a third input of the mixer, wherein the mixer output provides the LO frequency for a transmitter. 44. The system as claimed in claim 13, wherein the first mixer input and the mixer output are differential. 45. The system as claimed in claim 13, wherein the device comprises a receiver that incorporates differential signal paths. 46. A system for generating a local oscillator (LO) frequency in a multi-band direct conversion wireless communication device, the system comprising: a voltage controlled oscillator (VCO)(50l); characterised by: a first divider (520) having an input and an output produced by dividing a first 5 divider input signal, the input of the first divider being operatively coupled to the VCO; a secona divider (530) having an input ana an output proaucea by dividing a second divider input signal, the input of the second divider being operatively coupled to the output of the first divider; and a mixer (540) having a first mixer input operatively coupled to the output of the first divider, a second mixer input operatively coupled to the output of the second divider, and an output providing the LO fi-equency. 47. The system as claimed in claim 46, comprising a third divider (550) operatively coupled to the mixer output. 48. The system as claimed in claim 46, wherein the VCO is a multi-band VCO. 49. The system as claimed in claim 13, comprising: an LO generator having one or more configurations, each configuration being associated with at least one fi-equency band of RF signals and producing an output signal whose frequency is associated with the at least one frequency band of RF signals, the LO generator comprising the mixer and dividor; and a configuration selection mechanism arranged to select a configuration 25 associated with a chosen frequency band of RF signals. 50. The system as claimed in claim 49, wherein the LO generator is controlled based on the configuration selection mechanism.

Documents:

1068-chenp-2003 abstract duplicate.pdf

1068-chenp-2003 claims duplicate.pdf

1068-chenp-2003 description (complete) duplicate.pdf

1068-chenp-2003 drawings duplicate.pdf

1068-chenp-2003-abstract.pdf

1068-chenp-2003-assignement.pdf

1068-chenp-2003-claims.pdf

1068-chenp-2003-correspondnece-others.pdf

1068-chenp-2003-correspondnece-po.pdf

1068-chenp-2003-description(complete).pdf

1068-chenp-2003-drawings.pdf

1068-chenp-2003-form 1.pdf

1068-chenp-2003-form 13.pdf

1068-chenp-2003-form 26.pdf

1068-chenp-2003-form 3.pdf

1068-chenp-2003-form 5.pdf

1068-chenp-2003-pct.pdf