MULTIBAND RF RECEIVER AND METHOD FOR RECEIVING MULTIBAND RF SIGNAL

• US 20090325520A1
• Filed: 06/29/2009
• Published: 12/31/2009
• Est. Priority Date: 06/30/2008
• Status: Active Grant

• Current Assignee: KDDI Corporation
• Original Assignee: KDDI Corporation
• Inventors: KITAYABU, Toru
• Granted Patent: US 8,244,202 B2
• Time in Patent Office: Days
• US Class Current: 455/142
• CPC Class Codes: H04B 1/0007 wherein the AD/DA conversion occurs at radiofrequency or intermediate frequency stage
• CPC Class Codes: H04B 1/0064 with separate antennas for the more than one band H04B1/0053 takes precedence

Abstract

A multiband receiver is disclosed for receiving a multiband RF signal having first and second RF bands. The first RF band contains a first service RF range, and the second RF band contains a second service RF range. The receiver includes a mixer for converting the RF signal into an IF signal, using a single local oscillator frequency “f,” and an IF bandpass filter for canceling out some of frequencies of the IF signal outside of a predetermined passband. The local oscillator frequency “f” is determined to allow the first and second service IF ranges to lie outside of the predetermined passband, and to allow a frequency portion of the first IF band exclusive of the first service IF range and a frequency portion of the second IF band exclusive of the second service IF range to lie within the predetermined passband.

Claims

1. A receiver for receiving through at least one antenna a multiband radio frequency (RF) signal having first and second RF bands which are distinct,

wherein the first RF band contains high and low frequency portions, and the second RF band contains high and low frequency portions, and

the first RF band contains a first existing service RF range in a selected one of the high and low frequency portions of the first RF band, and the second RF band contains a second existing service RF range in a selected one of the high and low frequency portions of the second RF band,

the receiver comprising:

a mixer for converting the RF signal into an intermediate frequency (IF) signal, using a single local oscillator frequency “

f”

produced from a single local oscillator;

an IF bandpass filter for canceling out frequencies of the IF signal outside of a predetermined passband of the IF bandpass filter; and

an analog-to-digital (A/D) converter for converting the IF signal which has passed through the IF bandpass filter, into a Low-IF signal produced by simultaneous sampling of the IF signal at a single sampling frequency,

wherein the IF signal contains a first IF band corresponding to the first RF band, and a second IF band corresponding to the second RF band,

the first IF band contains a first existing service IF range corresponding to the first existing service RF range,

the second IF band contains a second existing service IF range corresponding to the second existing service RF range, and

the local oscillator frequency “

f”

is determined to allow the first and second existing service IF ranges to lie outside of the predetermined passband of the IF bandpass filter, and to allow a frequency portion of the first IF band exclusive of the first existing service IF range and a frequency portion of the second IF band exclusive of the second existing service IF range to lie within the predetermined passband of the IF bandpass filter.

2. The receiver according to claim 1, wherein the first and second existing service RF ranges lie in the first and second RF bands on a same side with respect to center frequencies of the first and second RF bands, respectively.

3. The receiver according to claim 1, further comprising a processor for selecting an arbitrary point located between the first and second RF bands as an initial local-oscillator-frequency “

f₀,”

for moving the local oscillator frequency “

f”

from the initial local-oscillator-frequency “

f₀”

by an amount Δ

f for allowing the first and second existing service IF ranges to lie outside of the predetermined passband of the IF bandpass filter, and for indicating a final value of the local oscillator frequency “

f”

to the local oscillator.

4. The receiver according to claim 1, wherein the A/D converter performs undersampling for the IF signal.

5. The receiver according to claim 1, wherein the IF bandpass filter is a single IF bandpass filter common to the first and second IF bands, and

the predetermined passband of the single IF bandpass filter is common to the first and second IF bands.

6. The receiver according to claim 5, wherein the local oscillator frequency “

f”

is determined to prevent interference, on a frequency axis, between a frequency portion of the first IF band exclusive of the first existing service IF range, and a frequency portion of the second IF band exclusive of the second existing service IF range, within the predetermined passband of the IF bandpass filter.

7. The receiver according to claim 1, wherein the IF signal includes two orthogonal signal components,

the mixer includes first and second mixers for the two orthogonal signal components, respectively,

the IF bandpass filter includes first and second IF bandpass filters for the two orthogonal signal components, respectively, and

the A/D converter includes first and second A/D converters for the two orthogonal signal components, respectively.

8. The receiver according to claim 7, wherein the first and second IF bandpass filters share a common passband, and

the local oscillator frequency “

f”

is determined to allow a frequency portion of the first IF band exclusive of the first existing service IF range and a frequency portion of the second IF band exclusive of the second existing service IF range to overlap with each other on a frequency axis, within the predetermined passbands of the first and second IF bandpass filters, respectively.

9. The receiver according to claim 1, wherein the IF bandpass filter is in the form of a notch filter having a predetermined stopband, and

the local oscillator frequency “

f”

is determined to allow the first and second existing service IF ranges to lie in the predetermined stopband of the notch filter.

10. A method for converting frequencies of a multiband radio frequency (RF) signal having first and second RF bands which are distinct, operable in a receiver for receiving the RF signal through at least one antenna,

wherein the first RF band contains high and low frequency portions, and the second RF band contains high and low frequency portions, and

the first RF band contains a first existing service RF range in a selected one of the high and low frequency portions of the first RF band, and the second RF band contains a second existing service RF range in a selected one of the high and low frequency portions of the second RF band,

the method comprising the steps of:

converting the RF signal into an intermediate frequency (IF) signal, using a single local oscillator frequency “

f”

produced from a single local oscillator;

canceling out frequencies of the IF signal outside of a predetermined passband of an IF bandpass filter; and

converting the IF signal which has passed through the IF bandpass filter, into a Low-IF signal produced by simultaneous sampling of the IF signal at a single sampling frequency,

wherein the IF signal contains a first IF band corresponding to the first RF band, and a second IF band corresponding to the second RF band,

the first IF band contains a first existing service IF range corresponding to the first existing service RF range,

the second IF band contains a second existing service IF range corresponding to the second existing service RF range, and

the local oscillator frequency “

f”

is determined to allow the first and second existing service IF ranges to lie outside of the predetermined passband of the IF bandpass filter, and to allow a frequency portion of the first IF band exclusive of the first existing service IF range and a frequency portion of the second IF band exclusive of the second existing service IF range to lie within the predetermined passband of the IF bandpass filter.

11. The method according to claim 10, wherein the first and second existing service RF ranges lie in the first and second RF bands on a same side with respect to center frequencies of the first and second RF bands, respectively.

12. The method according to claim 10, further comprising the steps of:

selecting an arbitrary point located between the first and second RF bands as an initial local-oscillator-frequency “

f₀;

”

moving the local oscillator frequency “

f”

from the initial local-oscillator-frequency “

f₀”

by an amount Δ

f for allowing the first and second existing service IF ranges to lie outside of the predetermined passband of the IF bandpass filter; and

indicating a final value of the local oscillator frequency “

f”

to the local oscillator.

13. A computer-readable medium having stored therein a program which, when executed by a computer, controls a receiver for receiving through at least one antenna a multiband radio frequency (RF) signal having first and second RF bands which are distinct,

wherein the first RF band contains high and low frequency portions, and the second RF band contains high and low frequency portions, and

the first RF band contains a first existing service RF range in a selected one of the high and low frequency portions of the first RF band, and the second RF band contains a second existing service RF range in a selected one of the high and low frequency portions of the second RF band,

the receiver comprising:

a mixer for converting the RF signal into an intermediate frequency (IF) signal, using a single local oscillator frequency “

f”

produced from a single local oscillator;

an IF bandpass filter for canceling out frequencies of the IF signal outside of a predetermined passband of the IF bandpass filter; and

an analog-to-digital (A/D) converter for converting the IF signal which has passed through the IF bandpass filter, into a Low-IF signal produced by simultaneous sampling of the IF signal at a single sampling frequency,

wherein the IF signal contains a first IF band corresponding to the first RF band, and a second IF band corresponding to the second RF band,

the first IF band contains a first existing service IF range corresponding to the first existing service RF range, and

the second IF band contains a second existing service IF range corresponding to the second existing service RF range,

the program comprising;

instructions for selecting an arbitrary point located between the first and second RF bands as an initial local-oscillator-frequency “

f₀;

”

instructions for moving the local oscillator frequency “

f”

from the initial local-oscillator-frequency “

f₀”

by an amount Δ

f for allowing the first and second existing service IF ranges to lie outside of the predetermined passband of the IF bandpass filter; and

instructions for indicating a final value of the local oscillator frequency “

f”

to the local oscillator.