Low leakage local oscillator system

• US 20050118973A1
• Filed: 06/03/2002
• Published: 06/02/2005
• Est. Priority Date: 06/25/2001
• Status: Active Grant

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Khlat, Nadim
• Granted Patent: US 7,327,993 B2
• Time in Patent Office: Days
• US Class Current: 455/260
• CPC Class Codes: H03D 7/165 at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature combined with amplitude demodulation H03D1/2245, combined with angle demodulation H03D3/007; N-path filters H03H19/002
• CPC Class Codes: H03J 5/0272 the digital values being used to preset a counter or a frequency divider in a phase locked loop, e.g. frequency synthesizer
• CPC Class Codes: H03J 7/065 the counter or frequency divider being used in a phase locked loop
• CPC Class Codes: H03L 7/1974 for fractional frequency division
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22

Abstract

Local oscillator apparatus comprising communication signal terminals (LNA IN, LNA INX; RF OUT,RF OUTN) for a communication signal, especially in a receiver or a transmitter, and a controlled frequency oscillator (204; 404) for producing a local oscillator signal. The local oscillator also includes a reference frequency generator (210; 410) and a feedback loop (208;408) for selecting and adjusting the frequency (fVCO) of the local oscillator signal relative to the frequency (fxtal) of said reference frequency signal. A first frequency divider (205; 405) divides the frequency of the local oscillatr signal by a first division factor (M) to produce a conversion signal, where the frequency (FILO) of said conversion signal is at least approximately equal to the frequency (fRF) of the communication signal, and conversion means (202,203; 402, 403) responsive to the conversion signal converts between said communication signal and a base-band signal. A second frequency divider (206;406) divides the frequency of the local oscillator signal by a second division factor (N) and is connected in the feedback loop, where the first division factor (N) is different to the second division factor (M) and the ratios between said first and second division factors (M/N, N/M) are fractional.

Claims

1. Local oscillator apparatus comprising communication signal terminals (LNA_IN, LNA_INX;

RF_OUT, RF_OUTN) for a communication signal, controlled frequency oscillator means (204;

404) for producing a local oscillator signal, reference frequency means (210;

410) for producing a reference frequency signal, feedback loop means (207-209;

407-409) for selecting and adjusting the frequency (fVCO) of said local oscillator signal relative to the frequency (fxtal) of said reference frequency signal, said feedback loop means (207-209;

407-409) including fractional-number dividing means (208;

408) for dividing said reference frequency by a programmable fractional number and supplying a feedback signal (VTUNE) to control the frequency (fVCO) of said oscillator means (204;

404), first frequency divider means (205;

405) for dividing the frequency of said local oscillator signal by a first division factor (M) to produce a conversion signal, where the frequency (FILO) of said conversion signal is at least approximately equal to the frequency (fRF) of said communication signal, and conversion means (202, 203;

402, 403) responsive to said conversion signal for converting between said communication signal and a base-band signal,

characterised in that second frequency divider means (206;

406) for dividing the frequency of said local oscillator signal by a second division factor (N) is connected in said feedback loop means (207-209;

407-409) between said controlled frequency oscillator means (204;

404) and said fractional-number dividing means (208;

408) so that said fractional-number dividing means (208;

408) is responsive to the relative values of said reference frequency divided by said programmable fractional number and said frequency of said local oscillator signal (fVCO) divided by said second division factor (N), where the first division factor (M) is different to the second division factor (N) and the ratios between said first and second division factors (M/N, N/M) are fractional.

2. Local oscillator apparatus as claimed in claim 1, characterised in that said first and second division factors (M, N) are integers greater than 1.

3. Local oscillator apparatus as claimed in claim 2, characterised in that said first division factor (M) is an even number.

4. Local oscillator apparatus as claimed in claim 3, characterised in that said second division factor (N) comprises a factor that is an odd number.

5. Local oscillator apparatus as claimed in claim 3, characterised in that said second division factor (N) is an odd number.

6. Local oscillator apparatus as claimed in any of claims 2 to 5, characterised in that said second division factor (N) comprises a factor that differs by 1 from a factor of said first division factor.

7. Local oscillator apparatus as claimed in any of claims 2 to 5, characterised in that said second division factor (N) differs by 1 from said first division factor.

8. Local oscillator apparatus as claimed in any preceding claim, characterised in that said communication signal terminals (LNA_IN, LNA_INX;

RF_OUT, RF_OUTN), said controlled frequency oscillator means (204;

404), said first frequency divider means (205;

405) and said conversion means (202, 203;

402, 403) are included in an integrated circuit (200;

400) and said feedback loop means (207-209;

407-409) are separate from said integrated circuit (200;

400).

9. Local oscillator apparatus as claimed in any preceding claim, characterised in that said feedback loop means (207-209;

407-409) comprises a fractional-number frequency synthesizer arranged to divide said reference frequency in steps that are a multiple of the ratio (MIN) of said first division factor (M) divided by said second division factor (N), whereby to change said frequency (FILO) of said conversion signal in steps equal to the channel spacing of the communication signal.

10. Receiver apparatus comprising local oscillator apparatus as claimed in any preceding claim, characterised in that said communication signal is received at said communication signal terminals (LNA_IN, LNA_NX), said conversion means (202, 203) being adapted to combine said communication signal with said conversion signal to produce said base-band signal.

11. Receiver apparatus as claimed in claim 10, characterised in that a low noise amplifier means (201) is connected to said communication signal terminals (LNA_IN, LNA_INX) to receive said communication signal and a transformer is connected between low noise amplifier means (201) and said conversion means (202, 203), said transformer presenting inductances and internal capacitances to said communication signal such as to form a band-pass filter tuned to the frequency fRF of the communication signal.

12. Transmitter apparatus comprising local oscillator apparatus as claimed in any of claims 1 to 9, characterised in that said communication signal is output at said communication signal terminals (RF_OUT, RF_OUTN), said conversion means (402, 403) being adapted to combine said base-band signal with said conversion signal to produce said communication signal.

13. Terminal apparatus comprising transmitter apparatus as claimed in claim 12, characterised in that said terminal apparatus also includes receiver apparatus capable of receiving signals in accordance with GPS standards, said transmitter apparatus being capable of transmitting a signal in accordance with WBCDMA standards and said first division factor (N) being equal to 3.