Digital frequency hopping transceiver and method thereof

1. A receiver, used in a frequency-hopping communication system comprising a transmitter which converts a baseband transmitting signal into a frequency-hopping signal and transmits the frequency-hopping signal to the receiver through a channel comprising N sub-bands, for receiving the frequency-hopping signal, the receiver comprising:

a demodulator for demodulating the frequency-hopping signal into an analog baseband signal according to an oscillation frequency;

a converter, coupled to the demodulator, for converting the analog baseband signal into a digital baseband signal; and

a frequency-dehopping module, coupled to the converter, for generating a baseband receiving signal according to the digital baseband signal, wherein the baseband receiving signal comprises information of the baseband transmitting signal;

wherein the frequency-dehopping module comprises:

a shift signal generator for generating N shift signals corresponding to the N sub-bands;

N multipliers, coupled to the ADC and the shift signal generator, for multiplying the digital baseband signal with the N shift signals respectively;

N frequency down-converters, each frequency down-converter, coupled to the corresponding multiplier, for down-converting an output of the corresponding multiplier to generating a down-converted signal according to a down-converting factor M; and

a selector, coupled to the N frequency down-converters, for selectively outputting one of the N down-converted signals from the N frequency down-converters to generate the baseband receiving signal.

2. The receiver of claim 1 , wherein the demodulator comprises:

an oscillator for generating an oscillation signal having the oscillation frequency; and

a mixer, coupled to the oscillator, for generating the analog baseband signal according to the frequency-hopping signal and the oscillation signal.

3. The receiver of claim 1 , wherein the converter comprises:

an analog-to-digital converter (ADC) for converting the analog baseband signal into the digital baseband signal;

wherein a sampling frequency f s of the ADC is determined according to a frequency difference B total between a highest frequency and a lowest frequency of the N sub-bands.

4. The receiver of claim 3 , wherein the sampling frequency f s of the ADC is not smaller than the frequency difference B total .

5. The receiver of claim 3 , wherein the converter further comprises:

a low-pass filter for filtering the analog baseband signal according to a cutoff frequency, wherein the cutoff frequency is determined according to the B total and an oscillation frequency of an oscillation signal outputted by an oscillator of the demodulator.

6. The receiver of claim 5 , wherein the oscillation frequency is approximately a central frequency of the channel and the cutoff frequency is approximately B total /2.

7. The receiver of claim 1 , wherein the frequency-hopping communication system is a multi-band orthogonal frequency division multiplexing (MB-OFDM) system.

8. A receiving method, used in a frequency-hopping communication system comprising a transmitter which converts a baseband transmitting signal into a frequency-hopping signal and transmits the frequency-hopping signal to a receiver through a channel comprising N sub-bands, for receiving the frequency-hopping signal, the receiving method comprising:

demodulating the frequency-hopping signal into an analog baseband signal according to an oscillation frequency by a demodulator in a receiver of the frequency-hopping communication system;

converting the analog baseband signal into a digital baseband signal by a converter in the receiver; and

generating a baseband receiving signal according to frequency dehopping of the digital baseband signal by a frequency-dehopping module in the receiver, wherein the baseband receiving signal comprises information of the baseband transmitting signal;

wherein the step of generating the baseband receiving signal comprises:

generating N shift signals corresponding to the N sub-bands by a shift signal generator in the frequency-dehopping module;

multiplying the digital baseband signal with the N shift signals to produce N multiplication results by N multipliers in the frequency-dehopping module;

down-converting the N multiplication results according to a down-converting factor M to generate N down-converted signals by N frequency down-converters in the frequency-dehopping module; and

selectively outputting one of the N down-converted signals to generate the baseband receiving signal by a selector in the frequency-dehopping module.

9. The receiving method of claim 8 , wherein the step of converting comprises:

filtering the analog baseband signal to generate a filtered baseband signal according to a first cutoff frequency by a low-pass filter in the converter; and

converting the filtered baseband signal into the digital baseband signal according to a sampling frequency f s by an analog-to-digital converter in the converter;

wherein the sampling frequency f s is determined according to a frequency difference B total between a highest frequency and a lowest frequency of the N sub-bands, and the first cutoff frequency is determined according to the B total and the oscillation frequency.

10. The receiving method of claim 9 , wherein the oscillation frequency is approximately a central frequency of the channel and the first cutoff frequency is approximately B total /2.

11. The receiving method of claim 10 , wherein the sampling frequency f s is not smaller than the frequency difference B total .

12. The receiving method of claim 9 , further comprising:

respectively filtering the N multiplication results according to a second cutoff frequency π/M by N digital low-pass filters in the frequency-dehopping module, wherein the value M is determined according to the sampling frequency.