CN102064767B - Frequency conversion device and conversion method and filter thereof - Google Patents

Abstract

The invention relates to a frequency conversion device and a conversion method and a filter thereof. The frequency conversion device samples an input signal by an analog-digital converter according to a sampling frequency to generate a first digital signal, wherein the sampling frequency and the frequency of the input signal have a corresponding relation, a symbol conversion circuit performs symbol conversion on the first digital signal to generate a second digital signal, a first switch module is used for selecting one of the first digital signal and the second digital signal as an output signal according to the sampling frequency, a filter receives and filters the output signal to generate a filtering signal, and a second switch module is used for outputting the filtering signal to a first output path or a second output path alternatively according to the sampling frequency. Therefore, the invention reduces the use of a filter and an analog-digital converter by the corresponding relation between the sampling frequency and the frequency of the input signal, reduces the area of the circuit and further saves the cost.

Description

Frequency conversion device and conversion method and filter thereof

technical field

The present invention relates to a conversion device and its conversion method, in particular to a frequency conversion device and its conversion method.

Background technique

For wireless communication products, its main components usually include two parts: a transmitter and a receiver, and the present invention is an innovation aimed at the receiver part. Taking the current TV system as an example, there are two main types of tuners in the TV system, one is the IF signal output structure of the traditional iron shell tuner (CAN tuner), and the other is the tuner commonly used in silicon chips (silicon chip). tuner) zero intermediate frequency (Zero IF) architecture, so a frequency conversion device in the demodulation processing circuit at the back end of the tuner must support these two input signals at the same time, that is, the intermediate frequency input signal and the base frequency input signal, please refer to Figure 1, It is a block diagram of a prior art frequency conversion device with an intermediate frequency signal input. As shown in the figure, the frequency conversion device 10' of the prior art includes an analog-to-digital converter 12', a first multiplier 14', a second multiplier 16', an oscillator 18', a first filter 24' and a second filter 26'. The analog-to-digital converter 12' receives the intermediate frequency signal output by the tuner 1', and converts the intermediate frequency signal according to a sampling frequency fs to generate a digital signal, and sends it to the first multiplier 14' and the second multiplier 16', the second A multiplier 14' and a second multiplier 16 respectively multiply the digital signal by a cosine signal and a sine signal, and reduce the intermediate frequency signal to a base frequency signal, and send it to the first filter 24' and the second filter 24'. The second filter 26' generates an I signal and a Q signal for subsequent circuits.

Since the demodulation processing circuit must support the intermediate frequency signal and the base frequency signal output by the tuner 1' at the same time, if the demodulation processing circuit does not use the frequency conversion device 10' in Figure 1, it uses a frequency conversion device that can receive the base frequency input signal. device. No matter what kind of frequency conversion device is used, two filters are required, and this makes the area of the demodulation processing circuit high, which will be reflected in the cost.

Contents of the invention

One of the objectives of the present invention is to provide a frequency conversion device and a conversion method thereof, which reduce the use of filters, reduce the area of the circuit, and further save costs.

One of the objectives of the present invention is to provide a frequency conversion device and a conversion method thereof, which reduce the use of analog-to-digital converters, reduce the complexity and area of circuits, and further save costs.

One of the objectives of the present invention is to provide a frequency conversion device and a conversion method thereof, which does not use a mixer, thereby reducing the complexity and area of the circuit, thereby saving cost.

One of the objectives of the present invention is to provide a frequency conversion device and its conversion method, which can simultaneously support the IF signal and the base frequency signal output by the tuner, thereby reducing the area of the circuit, thereby saving cost and improving performance.

The frequency conversion device of the present invention includes an analog-to-digital converter, a sign conversion circuit, a first switch module, a filter and a second switch module. The analog-to-digital converter receives and samples an input signal according to a sampling frequency to generate a first digital signal, wherein there is a corresponding relationship between the sampling frequency and the frequency of the input signal, and the symbol conversion circuit receives the first digital signal and converts the first The digital signal undergoes a symbol conversion to generate a second digital signal, the first switch module is used to select one of the first digital signal and the second digital signal as an output signal according to the sampling frequency, and the filter receives and filters the output signal to generate a filtered signal, and the second switch module is used to alternately output the output signal to a first output path or a second output path according to the sampling frequency. In this way, the use of a filter and an analog-to-digital converter can be reduced, thereby reducing the area of the circuit, thereby saving cost.

Furthermore, the frequency conversion device of the present invention further includes a third switch module and a switch control module. The third switch module is coupled to the analog-to-digital converter, and switches between a first input path and a second input path according to the sampling frequency and a switching control signal, and receives the input signal, and uses the first input path or the second input path to switch. The input signal received by the two input paths is sent to the analog-to-digital converter, wherein the third switch module can also stop switching according to the switching control signal, and only transmit the signal received by the first input path, and the switching control module is used for Generate switching control signals to the first switch module and the third switch module to control the switching of the first switch module and the third switch module. In this way, the frequency conversion device of the present invention can simultaneously support the intermediate frequency signal and the base frequency signal output by the tuner, thereby reducing the area of the circuit, thereby saving cost and improving performance.

The present invention provides a frequency conversion device, which includes: an analog-to-digital converter that receives and samples an input signal according to a sampling frequency to generate a first digital signal, wherein the frequency between the sampling frequency and the frequency of the input signal There is a corresponding relationship; a symbol conversion circuit is used to receive the first digital signal and perform a symbol conversion to generate a second digital signal; a first switch module is used to select the first digital signal according to the sampling frequency. One of the first digital signal and the second digital signal is used as an output signal; a filter, coupled to the first switch module, is used to filter the output signal from the first switch module and generate a first switch module. a filtered signal and a second filtered signal; and a second switch module coupled to the filter for alternately outputting the first filtered signal and the second filtered signal to a first output according to the sampling frequency path or a second output path.

The present invention also provides a frequency conversion method, the steps of which include: providing a first input path, receiving and sampling a first input signal from the first input path according to a first sampling frequency, to generate a first A digital signal, wherein the first sampling frequency has a corresponding relationship with the frequency of the first input signal; performing a symbol conversion on the first digital signal and generating a second digital signal; filtering the first digital signal and the at least one of the second digital signals to generate a first filtered signal and a second filtered signal; and output the first filtered signal and the second filtered signal to a first output path and a second output respectively path.

The present invention also provides a frequency conversion device, which includes: a first switch module, which switches between a first input path and a second input path according to a sampling frequency, and receives a first input signal or a first input signal. Two input signals, and transmit the first input signal and the second input signal; an analog-to-digital converter, receive and sample the first input signal or the second input signal according to the sampling frequency to generate a first digital signal , wherein, there is a corresponding relationship between the sampling frequency and the frequency of the input signal; a filter, coupled to the analog-to-digital converter, is used to receive and filter the first digital signal from the analog-to-digital converter, and generate A first filtered signal and a second filtered signal; and a second switch module, coupled to the filter, which alternately outputs the first filtered signal and the second filtered signal to a first output according to the sampling frequency path and a second output path.

The present invention also provides a frequency conversion method, the steps of which include: providing a first input path and a second input path, switching and receiving the signal transmitted by the first input path or the second input path according to a sampling frequency A first input signal and a second input signal; according to the sampling frequency, receive and sample the first input signal and the second input signal to generate a first digital signal, wherein the sampling frequency and the second input signal There is a corresponding relationship between an input signal and the frequency of the second input signal; filtering the first digital signal to generate a first filter signal and a second filter signal; and the first filter signal and the second filter signal respectively output to a first output path and a second output path.

Description of drawings

Fig. 1 is the block diagram of the frequency conversion device with intermediate frequency signal input of prior art;

Fig. 2 is a block diagram of a preferred embodiment of the present invention;

Fig. 3 is the block diagram of the finite impulse response filter of a preferred embodiment of the present invention;

Fig. 4 is the block diagram of another preferred embodiment of the present invention; And

FIG. 5 is a block diagram of another preferred embodiment of the present invention.

Description of reference symbols

current technology:

10’ frequency converter

12’ Analog to Digital Converter

14’ first multiplier

16’ second multiplier

18’ Oscillator

24’ first filter

26’ second filter

this invention:

10 frequency conversion device

12 Analog-to-digital converters

14 multipliers

16 switch

18 filter

180 first delay module

1800 first delay unit

181 Second delay module

1810 second delay unit

183 The first addition module

1830 The first addition unit

184 The first multiplication module

185 second multiplication module

186 Second addition module

187 The third addition module

20 switch modules

22 first switch

24 second switch

30 frequency conversion device

32 switch

34 Analog-to-digital converters

36 filters

38 switch module

40 frequency conversion device

42 first switch

44 Analog to Digital Converter

46 filter

47 switch module

48 multipliers

49 second switch

50 first logic gates

52 second logic gate

54 Inverter

Detailed ways

Please refer to FIG. 2 , which is a block diagram of a preferred embodiment of the present invention. As shown in the figure, the frequency conversion device 10 of the present invention includes an analog-to-digital converter 12 , a sign conversion circuit 14 , a switch 16 , a filter 18 and a switch module 20 . The analog-to-digital converter 12 receives an input signal and samples the input signal according to a sampling frequency fs of the sampling signal to generate a first digital signal. Wherein, the input signal is an output signal of a tuner 1 , and the input signal can be an intermediate frequency signal, and the analog-to-digital converter 12 outputs the first digital signal to the switch 16 and the symbol conversion circuit 14 . The sign conversion circuit 14 receives the first digital signal, and performs a sign conversion on the first digital signal to generate a second digital signal, that is, in the first embodiment, the sign conversion circuit 14 performs sign conversion on the first digital signal ; In the second embodiment, the sign conversion circuit 14 can be a 1's complement (1'scomplement) circuit; in the third embodiment, the multiplier 14 can be a 2's complement (2's complement) circuit. In addition, the sign conversion circuit 14 can also be a multiplier, which is used to multiply the first digital signal by a negative number to generate the second digital signal.

The switch 16 switches according to the speed of half the sampling frequency (fs/2), to select one of the first digital signal and the second digital signal as an output signal, that is, the first digital signal or the second digital signal The signal is sent to the filter 18 for filtering processing, such as low-pass filtering, to generate a first filtered signal and a second filtered signal respectively. The switch module 20 is coupled to the filter 18, and the switch module 20 is used to alternately output the filtered signal to a first output path or a second output path according to the sampling frequency, that is, the switch module 20 performs switching according to the sampling frequency fs, In order to output the first filtered signal and the second filtered signal as an output signal of the frequency converter 10, wherein the first output path and the second output path are respectively an in-phase (I) output path or a quadrature (Q ) output path. The switch module 20 includes a first switch 22 and a second switch 24 . The first switch 22 is used to switch the first filtered signal or the second filtered signal from the filter 18 to an I signal, and the second output switching switch 24 is used to switch the first filtered signal or the second filtered signal from the filter 18 to a Q signal.

Based on the above knowledge, the sampling frequency fs of the analog-to-digital converter 12 must meet the following equation;

n·Sampling frequency (f _s )±IF signal (f _if )=Sampling frequency (fs)/4

Wherein n is any integer, if n=-1, then sampling frequency fs=4x(fIF/5), wherein the selection of n can be according to the specification of analog-to-digital converter 10 and subsequent data processing circuit (not shown in the figure ) to select an appropriate value based on the amount of data required for processing, and obtain the sampling frequency fs of the analog-to-digital converter 12 . In a preferred embodiment, the values of n are generally -1, 0 and 1. In one embodiment, the frequency of the selected input signal is equal to a quarter of the sampling frequency of the sampling signal, that is, the frequency of the digital intermediate frequency is f _DIF =fs/4, so the oscillator 18' (as shown in FIG. 1 ) is The generated cosine and sine sequences can be simplified to the sequence of 0, 1, 0, -1.... Therefore, the present invention can omit the multipliers 14' and 16' of the prior art in Fig. 1, and use filtering The filter 18 replaces the first filter 24' and the second filter 26' of the prior art in FIG. 1 . Of course, in another embodiment, in this way, the area of the circuit can be reduced, thereby saving cost. Furthermore, since the sequence (0, 1, 0, -1...) and the sequence (1, 0, -1, 0...) represent the sine and cosine sequences respectively, the two sequences can be combined into one sequence (1, 1, -1, -1...), therefore, the switching frequency of the first switch 16 is switched according to half the sampling frequency (fs/2) to obtain the first digital signal or the second digital signal , and sent to the filter 18, so as to filter the I signal and Q signal at the same time. The above-mentioned implementation method can be realized with only one multiplier and one filter, so the cost is relatively saved.

In one embodiment, the filter 18 may be a finite impulse response (Finite Impulse Response, FIR) filter to filter the first digital signal or the second digital signal. In addition, since the filter 18 has symmetry, the filter 18 uses a finite impulse response filter with symmetric coefficients.

Please refer to FIG. 3 , which is a block diagram of a finite impulse response filter according to a preferred embodiment of the present invention. As shown in the figure, filter 18 of the present invention comprises a first delay module 180, a second delay module 181, a first addition module 183, a first multiplication module 184, a second multiplication module 185, a second The addition module 186 and a third addition module 187 . Wherein, the first delay module 180 , the second delay module 181 and the first addition module 183 respectively include a plurality of first delay units 1800 , a plurality of second delay units 1810 and a plurality of third addition units 1830 .

The first delay module 180 sequentially delays the first digital signal or the second digital signal, and sequentially generates a plurality of first delayed signals; the second delay module 181 sequentially delays the first delay from the first delay unit 1800 signal, and sequentially generate a plurality of second delayed signals; the first adding module 183 respectively corresponds to the first delayed signal and the second delayed signal, and the adding unit 1830 adds the corresponding first delayed signal and the second delayed signal The second delays the signal and generates a plurality of first sum signals sequentially. The first delay unit 1800 is connected in series to delay the first digital signal or the second digital signal and generate the first delayed signal. The second delay unit 1810 is connected in series for delaying the first delayed signal output from the last one in the series column formed by the first delay unit 1800 and generating a plurality of second delayed signals. The first adding unit 1830 corresponds to the first delay unit 1800 and the second delay unit 1810 respectively, and adds the first delay signal and the second delay signal corresponding to the first delay unit 1800 and the second delay unit 1810 respectively. delayed signal.

The first multiplication module 184 respectively multiplies odd-numbered first sum signals of the first sum signals with corresponding first coefficients among the plurality of first coefficients to generate a plurality of first product signals. The second multiplication module 185 respectively multiplies the even-numbered first sum signal of the first sum signal by the corresponding second coefficient among the plurality of second coefficients, and generates a plurality of second product signals. The second adding module 186 adds the first product signal to generate a first filtered signal. The third adding module 187 adds the second product signals to generate a second filtered signal. In this way, the filter 18 of the present invention uses the first adding module 183 shared by the first delay module 180 and the second delay module 181 to reduce the amount of computation by half, thereby reducing the area and cost of the circuit.

Please refer to FIG. 4 , which is a block diagram of another preferred embodiment of the present invention. As shown in the figure, the difference between the frequency conversion device 30 of this embodiment and the embodiment shown in FIG. 2 lies in that this embodiment is applied to receive a baseband signal for frequency conversion. This embodiment includes a switch 32 , an analog-to-digital converter 34 , a filter 36 and a switch module 38 . The switch 32 switches between a first input path and a second input path according to the sampling frequency f _s , and receives a first input signal or a second input signal respectively corresponding to the first input path and the second input path, and Send the first input signal and the second input signal to the analog-digital converter 34, and when the analog-digital converter 34 receives the first input signal or the second input signal, it samples the first input signal or the second input signal according to the sampling frequency f _s signal to generate a first digital signal, wherein there is a corresponding relationship between the sampling frequency and the frequency of the first input signal, that is, the frequency of the second input signal, that is, the sampling frequency is 1/4 of the frequency of the first input signal or the second input signal one.

The filter 36 is coupled to the analog-to-digital converter 34 to receive and filter the first digital signal of the analog-to-digital converter 34, and generate a filtered signal. The switch module 38 is coupled to the filter 36, and according to the sampling frequency f _s , Alternately output the filtered signal to a first output path and a second output path. Wherein, the first output path and the second output path are respectively an in-phase (I) output path or a quadrature (Q) output path, that is, the filtered signal generated by the filter 36 includes the first filtered signal and the second filtered signal, And output to the first output path and the second output path respectively through the switch module 38 . The above-mentioned analog-to-digital converter 34 , filter 36 and switch module 38 have been described in detail in the embodiment of FIG. 2 , so further description is omitted.

2, since the sampling frequency is 1/4 of the frequency of the first input signal or the second input signal, the present invention uses the switch 32 to switch the first input signal and the second input signal according to the sampling frequency, In order to save the use of an analog-to-digital converter and a filter, and reduce the complexity and area of the circuit, thereby saving cost.

Please refer to FIG. 5 , which is a block diagram of another preferred embodiment of the present invention. As shown in the figure, the frequency converting device 40 of this embodiment differs from the embodiments shown in FIG. 2 and FIG. 4 in that it can be applied to receive an intermediate frequency signal and a base frequency signal for conversion at the same time as the present embodiment. The frequency conversion device 40 of this embodiment includes a first switch 42, an analog-to-digital converter 44, a filter 46, a switch module 47, a multiplier 48, a second switch 49, a first logic gate 50, A second logic gate 52 and an inverter 54 .

Since the frequency converter 40 of this embodiment has one more switch module than the frequency conversion device 10 to control the first switch 42 and the second switch 49, wherein the switch module includes a first logic gate 50 and a second logic gate 52 to The switches 42 and 49 are controlled, so they can be used for frequency conversion of intermediate frequency signals or base frequency signals at the same time. In one embodiment, the first logic gate 50 may be an AND gate, and the second logic gate 52 may be an AND gate with at least one of the input terminals having an inverting input. The first logic gate 50 generates a switching signal according to a control signal to control the first switch 42, that is, when the control signal received by the first logic gate 50 is a high level signal, it means that the frequency conversion device 40 is applied to the baseband signal , that is, the first logic gate 50 sequentially switches the first input signal and the second input signal according to the sampling frequency fs of the sampling signal, for the analog-to-digital converter 44 to perform sampling and conversion, and at the same time, the second switch 49 stops switching , only the first digital signal generated by the analog-to-digital converter 44 is sent to the filter 46 for filtering and then output; when the control signal is a low-level signal, it means that the frequency conversion device 40 is applied to an intermediate frequency signal, the first A switch 42 stops switching. At this time, the operating mode of the frequency conversion device 40 is the same as that of the frequency conversion device 10. Therefore, the analog-to-digital converter 44 receives a third input signal through the transmission pipeline of the first input signal or the second input signal. input signal, and generate a third digital signal in the symbol conversion circuit 48 and the second switch 49, wherein the third input signal (not shown) is an output signal of a tuner, which is an intermediate frequency signal; the symbol conversion circuit 48. Convert the third digital signal to a positive or negative sign, that is, perform a negative sign conversion on the third digital signal to generate a fourth digital signal. Same as above, in another embodiment, the sign conversion circuit 48 can be a multiplier, and multiplies the third digital signal by a negative number to generate a fourth digital signal, which is sent to the switch 49 . In a preferred embodiment, the negative number can be -1; in the second embodiment, the sign conversion circuit 48 can be a 1's complement (1's complement) circuit; in the third embodiment, the sign conversion circuit 48 can be a 2's complement (2's complement) circuit. At the same time, the second switch 49 sequentially switches the third digital signal and the fourth digital signal according to half the sampling frequency (fs/2), and sends them to the filter 46 for filtering processing, and generates a The third filtered signal and a fourth filtered signal.

In summary, the frequency conversion device of the present invention satisfies the following equation with the sampling frequency fs of the analog-to-digital converter included therein:

n·f _s ±f _if ＝fs/4

That is, the sampling frequency fs of the analog-to-digital converter is 4 times, 8 times, etc. of the frequency of the input signal. Therefore, the use of the oscillator can be saved, and the use of the analog-to-digital converter and the filter can be reduced by switching the switch, and the area of the circuit can be relatively reduced, thereby saving cost. Moreover, the frequency converter of the present invention can At the same time, it is applied to the use of baseband signals or intermediate frequency signals, which further saves costs.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. All equivalent changes and modifications made according to the shape, structure, characteristics and spirit of the claims of the present invention, All should be included in the scope of the claims of the present invention.

Claims (39)

1. A frequency conversion device comprising: An analog-to-digital converter receives and samples an input signal according to a sampling frequency to generate a first digital signal, wherein there is a corresponding relationship between the sampling frequency and the frequency of the input signal; A symbol conversion circuit, used to receive the first digital signal and perform a symbol conversion on it to generate a second digital signal; a first switch module, used to select one of the first digital signal and the second digital signal as an output signal according to the sampling frequency; a filter, coupled to the first switch module, for filtering the output signal from the first switch module, and generating a first filtered signal and a second filtered signal; and A second switch module, coupled to the filter, is used to alternately output the first filtered signal and the second filtered signal to a first output path or a second output path according to the sampling frequency. 2. The frequency conversion device as claimed in claim 1, wherein the corresponding relationship is that the sampling frequency is a quarter of the frequency of the input signal. 3. The frequency conversion device as claimed in claim 1, wherein the sign conversion is a sign conversion of a signal. 4. The frequency conversion device as claimed in claim 1, wherein the first switch module transmits the first digital signal and the second digital signal alternately according to a frequency of one-half of the sampling frequency. 5. The frequency conversion device as claimed in claim 1, wherein the sign conversion circuit comprises a multiplier for multiplying the first digital signal by a negative number to generate the second digital signal. 6. The frequency conversion device as claimed in claim 1, wherein the filter comprises: A first delay module, used to receive and sequentially delay the output signal, and generate a plurality of first delayed signals; A second delay module, used to receive and sequentially delay one of the first delayed signals to generate a plurality of second delayed signals; A first adding module, used to receive the input signal, the first delayed signal and the second delayed signal, and calculate the input signal, the first delayed signal and the second delayed signal corresponding to each other Parts are added to generate a plurality of first sum signals correspondingly; A first multiplication module, used to receive the first sum signal and a plurality of first coefficients, and multiply the first sum signal and corresponding parts of the first coefficients to generate corresponding a plurality of first product signals; A second multiplication module, used to receive the first sum signal and a plurality of second coefficients, and multiply the first sum signal and the corresponding parts of the second coefficients to generate corresponding a plurality of second product signals; a second adding module, used to respectively receive and add up the first product signal to generate the first filtered signal; and A third adding module is used to respectively receive and sum the second product signals to generate the second filtered signal. 7. The frequency conversion device as claimed in claim 6, wherein the filter is a finite impulse response filter. 8. The frequency conversion device as claimed in claim 7, wherein the finite impulse response filter is a finite impulse response filter with symmetric coefficients. 9. The frequency conversion device as claimed in claim 1, wherein the first output path and the second output path are respectively an in-phase I output path or a quadrature Q output path. 10. The frequency conversion device as claimed in claim 1, wherein the input signal is an intermediate frequency signal. 11. The frequency conversion device as claimed in claim 1, wherein the input signal is an output signal of a tuner. 12. The frequency conversion device as claimed in claim 1, further comprising: A third switch module, coupled to the analog-to-digital converter, switches between a first input path and a second input path according to the sampling frequency and a switching control signal, receives the input signal, and uses the first input path The input signal received by an input path or the second input path is transmitted to the analog-to-digital converter, wherein the third switch module can also stop switching according to the switching control signal, and only transmit the input signal received by the first input path the signal received; and A switch control module is used to generate the switch control signal to the first switch module and the third switch module to control the switch between the first switch module and the third switch module. 13. The frequency conversion device according to claim 12, wherein when the third switch module is fixedly receiving the signal transmitted by the first input path, the first switch module alternately transmits the first digital signal according to the sampling frequency and the second digital signal to the filter. 14. The frequency conversion device as claimed in claim 12, wherein when the third switch module switches between the first input path and the second input path to receive the input signal, the first switch module stops switching and Only the first digital signal is transmitted. 15. The frequency conversion device as claimed in claim 12, wherein the input signal received by the third switch module is an intermediate frequency signal. 16. The frequency conversion device as claimed in claim 14, wherein the input signal received by the third switch module can be an I signal and a Q signal. 17. A frequency conversion method, the steps comprising: A first input path is provided to receive and sample a first input signal from the first input path according to a first sampling frequency to generate a first digital signal, wherein the first sampling frequency is the same as the first There is a corresponding relationship between the frequency of the input signal; performing a symbol conversion on the first digital signal and generating a second digital signal; filtering at least one of the first digital signal and the second digital signal to generate a first filtered signal and a second filtered signal; and Outputting the first filtered signal and the second filtered signal to a first output path and a second output path respectively. 18. The frequency conversion method as claimed in claim 17, wherein the corresponding relationship is that the first sampling frequency is a quarter of the frequency of the first input signal. 19. The frequency conversion method as claimed in claim 17, wherein the step of generating the first filtered signal and the second filtered signal further comprises: According to a second sampling frequency, it is used for switching between the first digital signal and the second digital signal, and alternately filtering the first digital signal and the second digital signal. 20. The frequency conversion method as claimed in claim 19, wherein the second sampling frequency is half of the first sampling frequency. 21. The frequency conversion method as claimed in claim 19, wherein the first input signal is an intermediate frequency signal. 22. The frequency conversion method as claimed in claim 17, wherein the step of generating the first digital signal further comprises: Provide a second input path, switch between the first input path and the second input path according to the first sampling frequency and a switching control signal, and alternately transmit the first input signal and the signal from the second input path A second input signal for generating the first digital signal. 23. The frequency conversion method as claimed in claim 22, wherein the step of generating the first filtered signal and the second filtered signal further comprises: The first digital signal is filtered to generate the first filtered signal and the second filtered signal. 24. The frequency conversion method as claimed in claim 22, wherein the first input signal and the second input signal are I signal and Q signal respectively. 25. The frequency conversion method as claimed in claim 22, wherein the first input signal and the second input signal are a baseband signal. 26. The frequency conversion method as claimed in claim 17, wherein the sign conversion is a sign conversion. 27. A frequency conversion device comprising: A first switch module switches between a first input path and a second input path according to a sampling frequency, receives a first input signal or a second input signal, and transmits the first input signal and the second input signal Two input signals; An analog-to-digital converter receives and samples the first input signal or the second input signal according to the sampling frequency to generate a first digital signal, wherein there is a corresponding relationship between the sampling frequency and the frequency of the input signal; a filter, coupled to the analog-digital converter, for receiving and filtering the first digital signal from the analog-digital converter, and generating a first filtered signal and a second filtered signal; and A second switch module, coupled to the filter, alternately outputs the first filtered signal and the second filtered signal to a first output path and a second output path according to the sampling frequency. 28. The frequency conversion device as claimed in claim 27, wherein the corresponding relationship is that the sampling frequency is a quarter of the frequency of the first input signal or the second input signal. 29. The frequency conversion device as claimed in claim 27, wherein the filter comprises: A first delay module, used to receive and sequentially delay the first digital signal, and generate a plurality of first delayed signals; A second delay module, used to receive and sequentially delay one of the first delayed signals to generate a plurality of second delayed signals; A first adding module, used to receive the first input signal, the first delayed signal and the second delayed signal, and combine the first input signal or the second input signal, the first delayed signal and the Parts corresponding to each other in the second delayed signal are added to generate a plurality of first sum signals correspondingly; A first multiplication module, used to receive the first sum signal and a plurality of first coefficients, and multiply the first sum signal and corresponding parts of the first coefficients to generate corresponding a plurality of first product signals; A second multiplication module, used to receive the first sum signal and a plurality of second coefficients, and multiply the first sum signal and the corresponding parts of the second coefficients to generate corresponding a plurality of second product signals; a second adding module, used to respectively receive and add up the first product signal to generate the first filtered signal; and A third adding module is used to respectively receive and sum the second product signals to generate the second filtered signal. 30. The frequency conversion device as claimed in claim 29, wherein the filter is a finite impulse response filter. 31. The frequency conversion device as claimed in claim 30, wherein the finite impulse response filter is a finite impulse response filter with symmetric coefficients. 32. The frequency conversion device as claimed in claim 27, wherein the first output path and the second output path are respectively an in-phase I output path or a quadrature Q output path. 33. The frequency conversion device as claimed in claim 27, wherein the first input signal and the second input signal are a baseband signal. 34. The frequency conversion device as claimed in claim 27, wherein the first input signal and the second input signal are an output signal of a tuner. 35. The frequency conversion device as claimed in claim 27, wherein the first input signal and the second input signal are respectively an I signal or a Q signal. 36. A method of frequency conversion, the steps comprising: providing a first input path and a second input path, switching and receiving a first input signal and a second input signal transmitted by the first input path or the second input path according to a sampling frequency; receiving and sampling the first input signal and the second input signal according to the sampling frequency to generate a first digital signal, wherein the sampling frequency corresponds to the frequencies of the first input signal and the second input signal relation; filtering the first digital signal to generate a first filtered signal and a second filtered signal; and Outputting the first filtered signal and the second filtered signal to a first output path and a second output path respectively. 37. The frequency conversion method as claimed in claim 36, wherein the corresponding relationship is that the sampling frequency is a quarter of the frequencies of the first input signal and the second input signal. 38. The frequency conversion method as claimed in claim 36, wherein the first input signal and the second input signal are a baseband signal. 39. The frequency conversion method as claimed in claim 36, wherein the first input signal and the second input signal are I signal and Q signal respectively.

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