Up / down conversion circuitry for radio transceiver

• US 20030219067A1
• Filed: 05/22/2002
• Published: 11/27/2003
• Est. Priority Date: 05/22/2002
• Status: Active Grant

• Current Assignee: Zarbana Digital Fund LLC (Intellectual Ventures LLC)
• Original Assignee: JS Whight Incorporated, Seven Generations Energy Ltd.
• Inventors: Wight, James Stuart, Birkett, Alexander Neil
• Granted Patent: US 7,194,044 B2
• Time in Patent Office: Days
• US Class Current: 375/219
• CPC Class Codes: H03D 7/163 the local oscillations of at least two of the frequency changers being derived from a single oscillator
• CPC Class Codes: H04B 1/26 for superheterodyne receivers multiple frequency-changing H03D7/16
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22

Abstract

A multi-channel RF receiver uses an image rejection mixer (e.g. double quadrature mixer) in the IF down conversion stage for image side band rejection (whereby use of an IF narrow band filter for image rejection may be omitted if desired) and comprises a simplified frequency synthesizer which generates both a “wandering” IF oscillator frequency and an RF oscillator frequency for the up/down conversion stages (being, for down conversion, from RF to IF and from IF to base band. The IF used for a particular RF carrier (channel) is selected so as to be both an integer (N) sub-harmonic of that RF carrier and within the operating frequency band of the image rejection mixer. Advantageously, the synthesizer comprises only one loop and one VCO, wherein the IF oscillator signal is produced from the RF oscillator signal by means of a frequency divider.

Claims

1. Down conversion circuitry for use in a radio transceiver for down converting a received RF information signal to a base band information signal in two stages wherein a first said stage converts said RF information signal to an IF information signal and a second said stage converts said IF information signal to said base band information signal, said down conversion circuitry comprising:

(a) a mixer component configured for down converting said RF information signal to said IF information signal using an RF oscillator signal;

(b) an image rejection mixer component configured for down converting said IF information signal to said base band signal using an IF oscillator signal and achieving substantial image signal rejection; and

,

(c) a frequency synthesizer configured for generating each of said RF and IF oscillator signals whereby said IF oscillator signal is an integer (N) sub-harmonic of said RF oscillator signal and the frequency value of said IF oscillator signal is pre-selected to be within the operating frequency band of said image rejection mixer component.

2. Down conversion circuitry according to claim 1 wherein said image signal rejection is at least 40 dB.

3. Down conversion circuitry according to claim 2 wherein said image rejection mixer component comprises a double quadrature mixer.

4. Down conversion circuitry according to claim 1 for use in a multiple channel radio transceiver wherein said frequency synthesizer generates RF and IF oscillator signals for each channel of said multiple channels and each said IF oscillator signal is of a different frequency from one said channel to another.

5. Down conversion circuitry according to claim 4 wherein said frequency synthesizer comprises a first frequency divider configured for dividing each said RF oscillator signal frequency for each said channel by an integer value N to produce said IF oscillator signal for said channel.

6. Down conversion circuitry according to claim 5 wherein said frequency synthesizer comprises a feedback loop and said first frequency divider, said feedback loop comprising a second frequency divider, a reference frequency source, multiplier means, low pass filter means and a voltage controlled oscillator wherein said RF oscillator signal derives from the output of said voltage controlled oscillator, said second frequency divider being configured for dividing said output of said voltage controlled oscillator by a preselected integer value M calculated to establish a desired frequency for said output of said voltage controlled oscillator based on said reference frequency, wherein a different value of M is preselected for each said channel to establish an RF oscillator signal associated with said channel.

7. Down conversion circuitry according to claim 6 wherein said RF oscillator signals are spaced 18 MHz apart for said multiple channels, said IF oscillator signals are spaced 2 MHz apart for said multiple channels and said value N is 9.

8. A method for use in a radio transceiver for down converting, in two stages, a received RF information signal to a base band information signal wherein a first said stage converts said RF information signal to an IF information signal and a second said stage converts said IF information signal to said base band information signal, said method comprising:

(a) down converting said RF information signal to said IF information signal using an RF oscillator signal;

(b) down converting said IF information signal to said base band signal using image rejection down conversion means configured for achieving substantial image signal rejection, and an IF oscillator signal; and

,

(c) generating each of said RF and IF oscillator signals whereby said IF oscillator signal is an integer (N) sub-harmonic of said RF oscillator signal, including preselecting the frequency value of said IF oscillator signal to be within the operating frequency band of said image rejection down conversion means.

9. A method according to claim 8 whereby said image signal rejection is at least 40 dB.

10. A method according to claim 8 for use in a multiple channel radio transceiver whereby said RF and IF oscillator signals are generated for each channel of said multiple channels and each said IF oscillator signal has a different frequency from one said channel to another.

11. A method according to claim 10 whereby said generating comprises dividing each said RF oscillator signal frequency for each said channel by an integer value N to produce said IF oscillator signal for said channel.

12. A method according to claim 11 whereby said generating uses a feedback loop comprising a second frequency divider, a reference frequency source, multiplier means, low pass filter means and a voltage controlled oscillator whereby said RF oscillator signal is derived from an output of said voltage controlled oscillator and said output is divided by a preselected integer value M calculated to establish a desired frequency for said output based on said reference frequency.

13. A method according to claim 12, whereby a different value of M is preselected for each said channel to establish an RF oscillator signal associated with said channel.

14. A method according to claim 13 whereby said RF oscillator signals are spaced 18 MHz apart for said multiple channels, said IF oscillator signals are spaced 2 MHz apart for said multiple channels and said value N is 9.

15. Up conversion circuitry for use in a radio transceiver for up converting, in two stages, a base- band information signal to an RF information signal for transmission, wherein a first said stage converts said base band information signal to an IF information signal and a second said stage converts said IF information signal to said RF information signal, said up conversion circuitry comprising:

(a) an image rejection mixer component configured for up converting said base band information signal to said IF information signal using an IF oscillator signal and achieving substantial image signal rejection;

(b) a mixer component configured for up converting said IF information signal to said RF information signal using an RF oscillator signal; and

,

(c) a frequency synthesizer configured for generating each of said RF and IF oscillator signals whereby said IF oscillator signal is an integer (N) sub-harmonic of said RF oscillator signal and the frequency value of said IF oscillator signal is pre-selected to be within the operating frequency band of said image rejection mixer component.

16. Up conversion circuitry according to claim 15 for use in a multiple channel radio transceiver wherein said frequency synthesizer generates RF and IF oscillator signals for each channel of said multiple channels and each said IF oscillator signal is of a different frequency from one said channel to another.

17. Up conversion circuitry according to claim 16 wherein said frequency synthesizer comprises a first frequency divider configured for dividing each said RF oscillator signal frequency for each said channel by an integer value N to produce said IF oscillator signal for said channel.

18. A method for use in a radio transceiver for up converting, in two stages, a base band information signal to an RF information signal wherein a first said stage converts said base band information signal to an IF information signal and a second said stage converts said IF information signal to said RF information signal, said method comprising:

(a) up converting said base band information signal to said IF information signal using image rejection up conversion means configured for achieving substantial image signal rejection and an IF oscillator signal;

(b) up converting said IF information signal to said RF information signal using an RF oscillator signal; and

,

(c) generating each of said RF and IF oscillator signals whereby said IF oscillator signal is an integer (N) sub-harmonic of said RF oscillator signal, including preselecting the frequency value of said IF oscillator signal to be within the operating frequency band of said image rejection up conversion means.

19. A method according to claim 18 for use in a multiple channel radio transceiver whereby said RF and IF oscillator signals are generated for each channel of said multiple channels and each said IF oscillator signal has a different frequency from one said channel to another.

20. A method according to claim 19 wherein said generating comprises dividing each said RF oscillator signal frequency for each said channel by an integer value N to produce said IF oscillator signal for said channel.