CN201563133U - Intermediate frequency signal modulating module of digital modulator - Google Patents

Abstract

The utility model relates to an intermediate frequency signal modulating module, in particular to an intermediate frequency signal modulating module of a digital modulator, which comprises an FPGA control unit, a high-speed digital-to-analogue conversion unit and an upper frequency conversion unit. The FPGA control unit generates baseband signals and control signals, the high-speed digital-to-analogue conversion unit is connected with the FPGA control unit, receives the baseband signals and the control signals and generates intermediate frequency signals, and the upper frequency conversion unit is connected with the high-speed digital-to-analogue conversion unit and receives the intermediate frequency signals. The intermediate frequency signal modulating module of a digital modulator can modulate baseband signals of a digital television to intermediate frequency 100MHz and keep delta f range from 200MHz to 8MHz, increases bandwidth of a transitional band, and directly reduces design complexity of an upper frequency conversion filter. Particularly, complexity of the filter can be reduced well when designing the relatively wide filter of an upper frequency conversion pass band.

Description

Digital modulator intermediate-freuqncy signal modulation module

Technical field

The utility model relates to a kind of intermediate-freuqncy signal modulation module, especially a kind of intermediate-freuqncy signal modulation module of digital modulator.

Background technology

In communication system, the radio frequency that is modulated to of baseband signal will be through twice modulation: one, baseband signal is modulated to intermediate-freuqncy signal; Two, intermediate-freuqncy signal further is modulated to radio frequency.The phenomenon that is modulated at frequency domain is moving of baseband frequency spectrum, after an intermediate frequency Modulation, can see the signal spectrum that needs on the frequency spectrum positive axis, can occur the image spectra of a signal spectrum simultaneously at the negative semiaxis of frequency spectrum.When carrying out secondary modulation, signal spectrum and mirror image thereof can be moved identical frequency, as shown in Figure 1: after modulation for the second time, promptly in upconverter, also need to leach signal spectrum with filter, just can obtain the radiofrequency signal that needs.Δ f among Fig. 1 has directly influenced the design complexities of up-converting filter, particularly under the situation of passband broad.

The shortcoming of prior art: prior art mostly is modulated to digital television baseband signals intermediate frequency 38MHz, Δ f=76-8MHz, and the bandwidth of Digital Television is 8MHz, transition band is less, and the complexity of up-converting filter design is had relatively high expectations.

Summary of the invention

The utility model provides a kind of bandwidth that increases transition band, has directly reduced the digital modulator intermediate-freuqncy signal modulation module of the design complexities of up-converting filter.

To achieve these goals, the utility model adopts following technical scheme, and it comprises

The FPGA control unit produces baseband signal and control signal;

The high-speed digital-analog converting unit is connected with the FPGA control unit, and receiving baseband signal and control signal produce intermediate-freuqncy signal;

The up-conversion unit is connected receiving intermediate frequency signal with the high-speed digital-analog converting unit.

Owing to adopted said structure, digital modulator intermediate-freuqncy signal modulation module of the present utility model can be modulated to digital television baseband signals intermediate frequency 100MHz, Δ f=200-8MHz has increased the bandwidth of transition band, has directly reduced the design complexities of up-converting filter.Particularly in design during the filter of frequency conversion passband broad, this method can well reduce the complexity of Design of Filter.

Description of drawings

Fig. 1 is a baseband signal modulation waveform schematic diagram;

Fig. 2 is the modular structure schematic diagram of the utility model embodiment.

The utility model purpose, function and advantage will be in conjunction with the embodiments, are described further with reference to accompanying drawing.

Embodiment

As shown in Figure 2, the digital modulator intermediate-freuqncy signal modulation module of present embodiment comprises FPGA control unit 1, FPGA control unit 1 described generation baseband signal and control signal;

High-speed digital-analog converting unit 2, high-speed digital-analog converting unit 2 is connected with FPGA control unit 1, and receiving baseband signal and control signal produce intermediate-freuqncy signal;

Up-conversion unit 3, up-conversion unit 3 is connected receiving intermediate frequency signal with the high-speed digital-analog converting unit.

The above only is a preferred embodiment of the present utility model; be not so limit claim of the present utility model; every equivalent structure or equivalent flow process conversion that utilizes the utility model specification and accompanying drawing content to be done; or directly or indirectly be used in other relevant technical fields, all in like manner be included in the scope of patent protection of the present utility model.

Claims (1)

1. digital modulator intermediate-freuqncy signal modulation module is characterized in that it comprises:

The FPGA control unit produces baseband signal and control signal;

The high-speed digital-analog converting unit is connected with the FPGA control unit, and receiving baseband signal and control signal produce intermediate-freuqncy signal;

The up-conversion unit is connected receiving intermediate frequency signal with the high-speed digital-analog converting unit.

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