Repeater and method for processing signal, and method for converting synchronous frequency thereof

• US 8,306,472 B2
• Filed: 09/26/2008
• Issued: 11/06/2012
• Est. Priority Date: 11/21/2007
• Status: Expired due to Fees

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Lim, Hyoung Soo, Eum, Ho Min, Park, Sung Ik, Seo, Jae Hyun, Lee, Yong Tae, Lee, Yong Hoon, Kim, Sung-Hoon, Kim, Heung Mook, Lim, Jong Soo, Lee, Soo In
• Primary Examiner(s): Ferguson, Keith
• Application Number:
  US12/741,081
• Publication Number:
  US 20100265996A1
• Time in Patent Office: 1,502 Days
• Field of Search: 455/20, 455/7, 455/11.1, 455/12.1, 455/21, 455/22, 455/23, 455/422.1, 455/403, 455/445, 455/550.1, 455/67.11, 455/500, 455/517, 455/67.13, 455/426.1, 455/426.2, 455/502, 370/315, 370/310, 370/317, 370/324, 370/350, 370/503, 375/211, 375/213
• US Class Current: 455/20
• CPC Class Codes: H04B 7/15528 Control of operation parameters of a relay station to exploit the physical medium

Abstract

A repeater having different input and output frequencies converts a signal received with the input frequency to a first intermediate frequency signal based on a local oscillating frequency for intermediate frequency conversion, and converts the first intermediate frequency signal to a second intermediate frequency signal by performing digital processing on the first intermediate frequency signal. Then, the repeater generates a first frequency tone signal that corresponds to a difference between the input and output frequencies, and generates a second frequency tone signal from the local oscillating frequency for intermediate frequency conversion and the first frequency tone signal. The repeater up-converts the second intermediate frequency signal to the output frequency based on the second frequency tone signal, and transmits the signal.

Claims

1. A signal processing method of a repeater that processes a received signal and outputs a transmitting signal, the signal processing method comprising:

converting the received signal to a first intermediate frequency signal based on a local oscillating frequency for intermediate frequency conversion;

converting the first intermediate frequency signal to a second intermediate frequency signal by performing digital processing on the first intermediate frequency signal;

generating a first frequency tone signal that corresponds to a difference between a first radio frequency of the received signal and a second radio frequency of the transmitting signal;

generating a second frequency tone signal from the local oscillating frequency for intermediate frequency conversion and the first frequency tone signal; and

outputting the transmitting signal by up-converting the second intermediate frequency signal to the second radio frequency based on the second frequency tone signal.

2. The signal processing method of claim 1, further comprising band-filtering the second frequency tone signal according to whether the first radio frequency is higher or lower than the second radio frequency.

3. The signal processing method of claim 2, wherein, when the first radio frequency is higher than the second radio frequency, a high frequency band signal of the second frequency tone signal is filtered.

4. The signal processing method of claim 2, wherein, when the first radio frequency is lower than the second radio frequency, a low frequency band signal of the second frequency tone signal is filtered.

5. The signal processing method of claim 2, wherein the outputting of the second intermediate frequency signal comprises:

generating a second baseband signal by compensating a frequency error while frequency down-converting the first intermediate frequency signal to a first baseband signal;

generating a third baseband signal by compensating a symbol timing error of the second baseband signal;

generating a fourth baseband signal by reflecting the symbol timing error on the third baseband signal; and

reflecting the frequency error on the fourth baseband signal and outputting the second intermediate frequency signal.

6. The signal processing method of claim 5, wherein the outputting of the second intermediate frequency signal further comprises generating a symbol clock from the third baseband signal, and the symbol clock serves as a reference clock for generating the first frequency tone signal.

7. The signal processing method of claim 1, wherein the first and second intermediate frequency signals have the same frequency.

8. A repeater for processing a received signal and transmitting a transmitting signal, the repeater comprising:

a down-converter for converting a first radio frequency of the received signal to a first intermediate frequency based on a local oscillating frequency;

a digital signal processor for down-converting the first intermediate frequency to a baseband frequency and frequency up-converting the baseband frequency to a second intermediate frequency;

a frequency synchronizer for generating a third radio frequency that corresponds to a difference between the first radio frequency and the second radio frequency according to a reference clock, and generating a fourth radio frequency by mixing the local oscillating frequency and the third radio frequency;

an up-converter for generating the second radio frequency by mixing the fourth radio frequency and the second intermediate frequency; and

a transmitter for transmitting the transmitting signal with the second radio frequency.

9. The repeater of claim 8, wherein the frequency synchronizer comprises a band-pass filter for band-filtering according to whether the first radio frequency is higher or lower than the second radio frequency.

10. The repeater of claim 8, wherein the digital signal processor comprises:

a frequency controller for compensating a frequency error of the received signal in frequency down-conversion to the baseband frequency;

a symbol timing recovery unit for compensating a symbol timing error of the frequency error-compensated signal; and

a clock generator for generating a symbol clock from the symbol timing error, wherein the symbol clock is used as the reference clock.

11. The repeater of claim 10, wherein the digital signal processor comprises:

an interpolator for reflecting the symbol timing error again on the symbol timing error-compensated signal; and

a frequency converter for outputting the second intermediate frequency signal by reflecting the frequency error again on a received signal on which the symbol time error is reflected,

wherein the first intermediate frequency is the same as the second intermediate frequency.

12. A frequency synchronization method of a repeater of which input frequency and output frequency are different from each other, the frequency synchronization method comprising:

generating a first frequency that corresponds to a difference between the input frequency and the output frequency;

generating a second frequency by mixing a local oscillating frequency with the first frequency, wherein the local oscillating frequency for intermediate frequency conversion is used for down-converting the input frequency to the intermediate frequency; and

generating the output frequency by mixing the first intermediate frequency and the second frequency.

13. The frequency synchronization method of claim 12, further comprising band-filtering the second frequency according to whether the input frequency is higher or lower than the output frequency.