CARRIER RECOVERY IN RE-MODULATION COMMUNICATION SYSTEMS

• US 20120220246A1
• Filed: 02/27/2011
• Published: 08/30/2012
• Est. Priority Date: 02/27/2011
• Status: Active Grant

• Current Assignee: Maxlinear Israel Ltd. (Maxlinear Incorporated)
• Original Assignee: Provigent Ltd. (Maxlinear Incorporated)
• Inventors: Friedmann, Jonathan, Shaked, Ronen, Oren, Tzahi, Kushnir, Igal Yehuda
• Granted Patent: US 8,406,709 B2
• Time in Patent Office: Days
• US Class Current: 455/118
• CPC Class Codes: H03D 3/004 wherein the demodulated signal is used for controlling an oscillator, e.g. the local oscillator
• CPC Class Codes: H04B 1/04 Circuits
• CPC Class Codes: H04L 2027/002 using feedback from a remote receiver
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657

Abstract

A communication apparatus includes transmission circuitry and a frequency conversion unit. The transmission circuitry is configured to down-convert an input Intermediate Frequency (IF) signal using a transmit (TX) Local Oscillator (LO) signal so as to produce a TX baseband signal, to up-convert the TX baseband signal to produce an output Radio Frequency (RF) signal, and to send the output RF signal to an antenna. The frequency correction unit is configured to estimate a frequency of the TX baseband signal or of the input IF signal, and to adjust the TX LO signal based on the estimated frequency so as to cause the transmission circuitry to down-convert the input IF signal to a predefined target frequency.

Claims

1. A communication apparatus, comprising:

transmission circuitry, which is configured to down-convert an input Intermediate Frequency (IF) signal using a transmit (TX) Local Oscillator (LO) signal so as to produce a TX baseband signal, to up-convert the TX baseband signal to produce an output Radio Frequency (RF) signal, and to send the output RF signal to an antenna; and

a frequency correction unit, which is configured to estimate a frequency of the TX baseband signal or of the input IF signal, and to adjust the TX LO signal based on the estimated frequency so as to cause the transmission circuitry to down-convert the input IF signal to a predefined target frequency.

2. The apparatus according to claim 1, wherein the transmission circuitry and the frequency control unit are comprised in an Outdoor Unit (ODU), and wherein the transmission circuitry is configured to receive the input IF signal over a cable from an Indoor Unit (IDU).

3. The apparatus according to claim 2, wherein the IDU comprises an up-converter, which is configured to produce the input IF signal.

4. The apparatus according to claim 1, wherein the predefined target frequency comprises zero Hz.

5. The apparatus according to claim 1, wherein the input IF signal comprises a modulated signal, and wherein the frequency correction unit is configured to recover a carrier of the modulated signal and to adjust the TX LO signal based on the recovered carrier.

6. The apparatus according to claim 5, wherein the frequency correction unit is configured to recover the carrier of the modulated signal using one of a blind estimation process, a decision-directed estimation process and a data-aided estimation process.

7. The apparatus according to claim 1, and comprising reception circuitry, which is configured to down-convert an input RF signal to produce a receive (RX) baseband signal, to up-convert the RX baseband signal using a RX LO signal so as to produce an output IF signal having a desired frequency, and to output the output IF signal, wherein the frequency correction unit is configured to adjust the RX LO signal responsively to the estimated frequency.

8. A communication apparatus, comprising:

transmission circuitry, which is configured to produce and transmit an output Radio Frequency (RF) signal;

reception circuitry, which is configured to down-convert an input RF signal to produce a receive (RX) baseband signal, to up-convert the RX baseband signal using a RX LO signal so as to produce an output IF signal, and to output the output IF signal; and

a frequency correction unit, which is configured to estimate a signal frequency used in the transmission circuitry, and to adjust the RX LO signal responsively to the estimated signal frequency.

9. The apparatus according to claim 8, wherein the transmission circuitry is configured to produce the output RF signal by down-converting an input IF signal using a TX LO signal so as to produce a TX baseband signal and then up-converting the TX baseband signal to produce the output RF signal, and wherein the signal frequency comprises a frequency of the TX baseband signal or of the input IF signal.

10. The apparatus according to claim 8, wherein the transmission circuitry, the reception circuitry and the frequency control unit are comprised in an Outdoor Unit (ODU), and wherein the reception circuitry is configured to send the output IF signal over a cable to an Indoor Unit (IDU).

11. A communication system, comprising:

a transmitter, comprising;

an Indoor Unit (IDU), which is configured to produce an Intermediate Frequency (IF) signal, and to send the IF signal over a cable; and

an Outdoor Unit (ODU), which is configured to accept the IF signal from the cable, to up-convert the IF signal so as to produce a Radio Frequency (RF) signal, and to transmit the RF signal over a wireless channel; and

a receiver, which is configured to receive the RF signal from the wireless channel, to process the RF signal so as to estimate a frequency error introduced by a difference between respective clock frequencies of the IDU and the ODU, and to transmit to the transmitter feedback so as to cause the transmitter to correct the frequency error.

12. A communication method, comprising:

down-converting an input Intermediate Frequency (IF) signal using a transmit (TX) Local Oscillator (LO) signal so as to produce a TX baseband signal;

up-converting the TX baseband signal to produce an output Radio Frequency (RF) signal, and sending the output RF signal to an antenna; and

estimating a frequency of the TX baseband signal or of the input IF signal, and adjusting the TX LO signal based on the estimated frequency so as to cause the input IF signal to be down-converted to a predefined target frequency.

13. The method according to claim 12, wherein down-conversion of the input IF signal, up-conversion of the TX baseband signal, estimation of the frequency error and adjustment of the TX LO signal are performed in an Outdoor Unit (ODU), and comprising receiving the input IF signal over a cable from an Indoor Unit (IDU).

14. The method according to claim 13, and comprising producing the input IF signal using an up-converter in the IDU.

15. The method according to claim 12, wherein the predefined target frequency comprises zero Hz.

16. The method according to claim 12, wherein the input IF signal comprises a modulated signal, and wherein estimating the frequency error and adjusting the TX LO signal comprise recovering a carrier of the modulated signal and adjusting the TX LO signal based on the recovered carrier.

17. The method according to claim 16, wherein recovering the carrier of the modulated signal comprises applying one of a blind estimation process, a decision-directed estimation process and a data-aided estimation process.

18. The method according to claim 12, and comprising down-converting an input RF signal to produce a receive (RX) baseband signal, up-converting the RX baseband signal using a RX LO signal so as to produce an output IF signal having a desired frequency and outputting the output IF signal, and adjusting the RX LO signal responsively to the estimated frequency.

19. A communication method, comprising:

using transmission circuitry, producing and transmitting an output Radio Frequency (RF) signal;

using reception circuitry, down-converting an input RF signal to produce a receive (RX) baseband signal, up-converting the RX baseband signal using a RX LO signal so as to produce an output IF signal, and outputting the output IF signal; and

estimating a signal frequency used in the transmission circuitry, and adjusting the RX LO signal responsively to the estimated signal frequency.

20. The method according to claim 19, wherein producing the output RF signal comprises down-converting an input IF signal using a TX LO signal so as to produce a TX baseband signal and then up-converting the TX baseband signal to produce the output RF signal, and wherein the signal frequency comprises a frequency of the TX baseband signal or of the input IF signal.

21. The method according to claim 19, wherein transmission of the output RF signal, down-conversion of the input RF signal, up-conversion of the RX baseband signal, and estimation of the TX frequency error are performed in an Outdoor Unit (ODU), and comprising sending the output IF signal over a cable to an Indoor Unit (IDU).

22. A communication method, comprising:

producing an Intermediate Frequency (IF) signal in an Indoor Unit (IDU) of a transmitter, and sending the IF signal over a cable;

in an Outdoor Unit (ODU) of the transmitter, accepting the IF signal from the cable, up-converting the IF signal so as to produce a Radio Frequency (RF) signal, and transmitting the RF signal to a receiver;

in the receiver, receiving the RF signal, processing the RF signal so as to estimate a frequency error introduced by a difference between respective clock frequencies of the IDU and the ODU, and transmitting to the transmitter feedback indicative of the frequency error; and

correcting the frequency error in the transmitter responsively to the feedback.