CN101521773B - Demodulator and corresponding demodulating method thereof - Google Patents

Abstract

The invention relates to a demodulator, which is applicable to ATSC, NTSC, PAL, SECAM, VSB and SSB standard systems, and comprises an antenna for receiving a radio-frequency signal, a low-noise amplifier that is electrically connected with the antenna, a first frequency mixer, a second frequency mixer, a low-pass wave filter and a signal processor. The first frequency mixer is electrically connected with the low-noise amplifier so as to lead the radio-frequency signal to be frequency-mixed with a first local oscillating signal, thus generating a first output signal. The second frequency mixer is electrically connected with the low-noise amplifier so as to lead the radio-frequency signal to be frequency-mixed with a second local oscillating signal, thus generating a second output signal. The low-pass wave filter is respectively and electrically connected with the first frequency mixer and the second frequency mixer so as to implement the wave filtering of the middle frequence components in the first output signal and the second output signal, thus respectively generating a first baseband signal and a second baseband signal. The signal processor implements the recovering processing of the first baseband signal and the second baseband signal so as to restore and obtain an original video signal.

Description

Demodulator and corresponding demodulation method thereof

Technical field

The present invention relates to a kind of demodulator and corresponding demodulation method thereof, relate in particular to a kind of ATSC of being used for (Advanced Television Systems Committee, the United States advanced television system committee), NTSC (National Television System Committee, National Television System Committee), PAL (Phase Alternating Line, Phase Alternate Line), VSB (Vestigial Side Band, the residual sideband standard), SECAM (Sequential Couleur Avec Memoire, SEQUAM system), and demodulator in the system of SSB standards such as (Single Side Band, single sideband system formulas) and corresponding demodulation method thereof.

Background technology

Digital Television (Digital Television) is a kind of television system of developing in order to experience the strong atmosphere of arenas in family.Compare with the simulated television of present extensive use, it has improved definition, the fabric width of picture greatly, and CD (Compact Disc) is provided the multichannel sound accompaniment of level.For Digital Television, the U.S., Europe and Japan and other countries are all being formulated the standard that meets self respectively.At present, the standard of being formulated has ATSC in the world, NTSC, PAL, SECAM, VSB, SSB standard, and QAM (Quadrature Amplitude Modulation, quadrature amplitude modulation), QPSK (Quadrature Phase Shift Keying, Quadrature Phase Shift Keying), OFDM (Orthogonal Frequency Division Multiplexing, orthogonal multiple frequency division of labor system), GSM (Global System for Mobile Communications, global system for mobile communications), CDMA (Code Division Multiple Access, code division multiple access) standard or the like.For example, the VSB standard that the U.S. adopted, specifically can be referring to people such as Wayne at document IEEE Transactions on Consumer Electronics, Vol.41, VSB Modem Subsystem Design for Grand Alliance Digital Television Receivers one literary composition of delivering August nineteen ninety-five among the No.3.

In the prior art, for ATSC, NTSC, PAL, SECAM, VSB and SSB standard adopt superhet demodulation method (super heterodyne method for demodulation) usually, and its signal only takies the part of double-side band, and this superhet demodulation method needs logical (intermediate frequency) filter (sharp passband (IF) filter) of a sharpening band, to remove the signal in the adjacent lanes before recovering modulated signal.

Because this superhet demodulation method need adopt logical (intermediate frequency) filter of sharpening band to filter out unwanted radiofrequency signal (RF Signals), and logical (intermediate frequency) filter of this sharpening band is one and has the high request standard, suitable Fu Za circuit, it needs a large amount of electronic building bricks, and the energy that consumes is more.In order to reduce high request standard to logical (intermediate frequency) filter of this sharpening band, can in system, increase an image removing circuit (Imaging Rejection Circuit), but it still needs logical (intermediate frequency) filter of this sharpening band can satisfy certain restriction.And this image removing circuit also is the circuit of a complexity, particularly in wide path is used, as the video transmission path of 40MHZ to 800MHZ.

In view of this, be necessary to provide a kind of at ATSC, NTSC, PAL, SECAM, the demodulator of VSB and SSB standard and corresponding demodulation method, it can reduce needed electronic building brick, simplifies corresponding circuit.

Summary of the invention

To illustrate with embodiment below a kind of at ATSC, NTSC, PAL, SECAM, the demodulator of VSB and SSB standard and corresponding demodulation method, it can reduce needed electronic building brick, simplifies corresponding circuit.

A kind of ATSC that is applicable to, NTSC, PAL, SECAM, the demodulator of VSB and SSB modular system, it comprises: one is used for the antenna of received RF signal; One low noise amplifier that is electrically connected with antenna, this low noise amplifier are used for the received radiofrequency signal of antenna is amplified; One first frequency mixer, it is electrically connected to this low noise amplifier so that this radiofrequency signal and one first local oscillation signal carry out mixing to produce one first output signal; One second frequency mixer, it is electrically connected to this low noise amplifier so that this radiofrequency signal and one second local oscillation signal carry out mixing to produce one second output signal, this second local oscillation signal and the first local oscillation signal quadrature; One low pass filter, it is electrically connected to this first frequency mixer and this second frequency mixer respectively so that this first output signal and second output signal are carried out low-pass filtering, and this low pass filter filters out intermediate frequency composition in this first output signal and this second output signal to produce one first baseband signal and one second baseband signal respectively; And a signal processor, it forms to be electrically connected so that this first baseband signal and this second baseband signal are handled with reduction with this low pass filter and obtains original video signal.Wherein, thereby this signal processor is handled this first baseband signal and this second baseband signal and is obtained one first processing signals, this first processing signals is a real part with first baseband signal, is imaginary part with second baseband signal, and this signal processor is ω with this first processing signals and a frequency also _hComplex signal carry out mixing, thereby obtain one second processing signals, calculate reduction and obtain this vision signal, ω thereby this second processing signals is got real part _hCorresponding to half frequency values of this radiofrequency signal bandwidth, it is a base band frequency.

A kind of ATSC that is applicable to, NTSC, PAL, SECAM, the demodulation method of VSB and SSB modular system, it comprises: utilize an antenna received RF signal, this radiofrequency signal is that a vision signal and a carrier wave are modulated and generated; Utilize a low noise amplifier that the received radiofrequency signal of antenna is amplified; The radiofrequency signal and one first local oscillation signal of this amplification are carried out mixing to produce one first output signal; The radiofrequency signal and one second local oscillation signal of this amplification are carried out mixing to produce one second output signal, this second local oscillation signal and this first local oscillation signal quadrature; This first output signal is carried out low-pass filtering, and the intermediate frequency composition that filters out this first output signal is to produce one first baseband signal; This second output signal is carried out low-pass filtering, and the intermediate frequency composition that filters out this second output signal is to produce one second baseband signal; Utilize a signal processor that this first baseband signal and this second baseband signal are handled with reduction and obtain original video signal.Wherein, thereby this signal processor is handled this first baseband signal and this second baseband signal and is obtained one first processing signals, this first processing signals is a real part with first baseband signal, is imaginary part with second baseband signal, and this signal processor is ω with this first processing signals and a frequency also _hComplex signal carry out mixing, thereby obtain one second processing signals, calculate reduction and obtain this vision signal, ω thereby this second processing signals is got real part _hCorresponding to half frequency values of this radiofrequency signal bandwidth, it is a base band frequency.

With respect to prior art, the ATSC that is applicable to provided by the present invention, NTSC, PAL, SECAM, the demodulator of VSB and SSB modular system and corresponding demodulation method are to convert radiofrequency signal to zero intermediate frequency signals, and therefore demodulator of the present invention and demodulation method adopt low pass filter can restore original video signal, and do not need the sharpening band to lead to (intermediate frequency) filter.And low pass filter leads to (intermediate frequency) filter compared to the sharpening band, and its circuit is comparatively simple, and the electronic component that needs is less, and consumed energy is few, and can be integrated on an integrated chip or the integrated circuit, is fit to the needs of present integrated circuit high integration.

Description of drawings

Fig. 1 be the embodiment of the invention provide be applicable to ATSC, NTSC, PAL, SECAM, the spectrum diagram of the vision signal of VSB and SSB modular system.

Fig. 2 is the schematic diagram of the analytic signal of vision signal shown in Figure 1.

Fig. 3 is the schematic diagram of the modulation signal that produces after ovennodulation of analytic signal shown in Figure 2.

Fig. 4 is that the process of modulation signal shown in Figure 3 gets that real part calculates and the schematic diagram of the radiofrequency signal that generates.

Fig. 5 be the embodiment of the invention provide be applicable to ATSC, NTSC, PAL, SECAM, the schematic diagram of the demodulator of VSB and SSB modular system.

Fig. 6 carries out demodulation and the intermediate treatment signal that generates and the schematic diagram of first processing signals to radiofrequency signal shown in Figure 5.

Fig. 7 handles and second processing signals that generates and the schematic diagram of going back original video signal first processing signals shown in Figure 6.

Embodiment

To be described in further detail the embodiment of the invention below in conjunction with accompanying drawing.

What the present invention relates to is to be applicable to ATSC, NTSC, PAL, SECAM, the demodulator of VSB and SSB modular system and corresponding demodulation method, but, for a better understanding of the present invention, at first will briefly introduce being applicable to ATSC, NTSC, PAL, SECAM, the correlated process that the vision signal of VSB and SSB modular system is modulated.And in the present embodiment, be that the vision signal with the SSB modular system is that example is modulated and demodulation, certainly, ATSC, NTSC, PAL, SECAM, the vision signal of VSB modular system also can be modulated and demodulation it as the described method of present embodiment.

At first, the vision signal S (t) with the SSB modular system utilizes analytic method to simulate.See also Fig. 1, according to Fourier page or leaf principle, if this vision signal S (t) is the baseband signal of a real number, then this vision signal S (t) is the yoke rice symmetry (Hermitian Symmetrical) about 0 frequency on frequency spectrum.See also Fig. 2, this vision signal S (t) is carried out Hilbert (Hilbert) conversion, thereby obtain the analytic signal S of this vision signal S (t) _a(t).This analytic signal S _a(t) be:

$s_a\left(t\right)=s\left(t\right)+j\hat{s}\left(t\right)$

Wherein,

Hilbert transform form for this vision signal S (t).

Because this analytic signal S _a(t) be that vision signal S (t) is carried out Hilbert transform and obtains, therefore, this analytic signal S _a(t) be a positive frequency signal.And because this vision signal S (t) is a baseband signal, so this analytic signal S _a(t) also be a baseband signal, it also is not easy to carry out wireless transmission.For with this analytic signal S _a(t) can carry out wireless transmission, need be to its modulation of being correlated with, to obtain a modulation signal Z (t).

See also Fig. 3, this modulation signal Z (t) is with this analytic signal S _a(t) has positive frequency f with one _cThereby carrier wave carry out mixing and obtain, promptly this modulation signal Z (t) is this analytic signal S _a(t) multiply by

$z\left(t\right)=s_a\left(t\right)e^{j{\mathrm{\ω}}_{c}t}=s_a\left(t\right)[\cos \left({\mathrm{\ω}}_{c}t\right)+j\cos \left({\mathrm{\ω}}_{c}t\right)]$

Because analytic signal S _a(t) be a positive frequency signal, thus itself and have positive frequency f _cCarrier multiplication and the modulation signal Z (t) that obtains also is a positive frequency signal, this modulation signal Z (t) does not have any negative frequency composition, and this modulation signal Z (t) also is an analytic signal, it is a complex signal, can be expressed as:

$z\left(t\right)=s_{\mathrm{ssb}}\left(t\right)+j\widehat{s_{\mathrm{ssb}}\left(t\right)}$

S wherein _Ssb(t) be radiofrequency signal, it is used to carry out the path transmission; And Be RF signal S _Ssb(t) Hilbert transition form.Because this modulation signal Z (t) is a plural number (Complex Number), it can not be used for the path transmission, therefore, gets the real part S of this modulation signal Z (t) _Ssb(t) as radiofrequency signal, to be used for the path transmission.This RF signal S _Ssb(t) as shown in Figure 4, it includes f _cThe carrier wave composition of frequency, it is:

$s_{\mathrm{ssb}}\left(t\right)=\mathrm{Re}\left\{Z\left(t\right)\right\}=\mathrm{Re}\{s_a\left(t\right)\·e^{j{\mathrm{\ω}}_{c}t}\}$

$=\mathrm{Re}\left\{\right[s\left(t\right)+j\hat{s}\left(t\right)]\·[\cos \left({\mathrm{\ω}}_{c}t\right)+j\sin \left({\mathrm{\ω}}_{c}t\right)\left]\right\}$

$=s\left(t\right)\cos \left({\mathrm{\ω}}_{c}t\right)-\hat{s}\left(t\right)\sin \left({\mathrm{\ω}}_{c}t\right)$

Below will specifically introduce the ATSC of being applicable to provided by the present invention, NTSC, PAL, SECAM, the demodulator of VSB and SSB modular system and corresponding demodulation method.In the present embodiment, be that the vision signal S in the SSB modular system (t) is carried out the RF signal S that said method modulation back produces _SsbThe demodulation of (t) being correlated with.

See also Fig. 5, a kind of ATSC of being applicable to that the embodiment of the invention provides, NTSC, PAL, SECAM, the demodulator 100 of VSB and SSB modular system.This demodulator 100 comprises that is used for a received RF signal S _Ssb(t) antenna 110; A low noise amplifier that is electrically connected with this antenna 110 (LNA, Low Noise Amplifier) 120, this low noise amplifier 120 are used for the received RF signal S of antenna 110 _Ssb(t) amplify; One first frequency mixer 130, it is electrically connected to this low noise amplifier 120 so that this radiofrequency signal and one first local oscillation signal cos ((ω _c+ ω _h)) t carries out mixing to produce one first output signal I; Second frequency mixer 140 with these first frequency mixer, 130 quadratures, it is electrically connected to this low noise amplifier 120 so that this RF signal S _Ssb(t) with one second local oscillation signal sin ((ω _c+ ω _k)) t carries out mixing to produce one second output signal Q, this second local oscillation signal Q and the first local oscillation signal I quadrature; A low pass filter 150, it is electrically connected to this first frequency mixer 130 and this second frequency mixer 140 respectively so that this first output signal I and the second output signal Q are carried out low-pass filtering, thereby produces one first baseband signal I_channel and one second baseband signal Q_channel respectively; A signal processor (DSP, Digital Signal Processor) 170, it forms to be electrically connected so that this first baseband signal I_channel and this second baseband signal Q_channel are handled with reduction with this low pass filter 150 and obtains original signal.

Preferably, this demodulator 100 further comprises an analog to digital converter 160, this analog to digital converter 160 is connected electrically between this low pass filter 150 and this signal processor 170 so that form between this signal processor 170 and this low pass filter 150 and be electrically connected, and this analog to digital converter 160 carries out digitized processing with the first baseband signal I_channel and the second baseband signal Q_channel that this low pass filter 150 is produced, and transfers to this signal processor 170 then and handles.This signal processor 170 is a digital signal processor.

The concrete operation principle of this demodulator 100 is as described below:

(1) utilizes antenna 110 received RF signal S _Ssb(t), this RF signal S wherein _Ssb(t) be:

$s_{\mathrm{ssb}}\left(t\right)=s\left(t\right)\cos \left({\mathrm{\ω}}_{c}t\right)-\hat{s}\left(t\right)\sin \left({\mathrm{\ω}}_{c}t\right)$

(2) 120 pairs of these RF signal S of this low noise amplifier _Ssb(t) amplify.

(3) RF signal S after 130 pairs of amplifications of this first frequency mixer _Ssb(t) with first local oscillation signal the cos ((ω _c+ ω _h)) t carries out mixing to produce this first output signal I.

$I=s_{\mathrm{ssb}}\left(t\right)\cos (-({\mathrm{\ω}}_c+{\mathrm{\ω}}_h))t=(s\left(t\right)\cos \left({\mathrm{\ω}}_{c}t\right)-\hat{s}\left(t\right)\sin \left({\mathrm{\ω}}_{c}t\right))\cos (-({\mathrm{\ω}}_c+{\mathrm{\ω}}_h)t)$

$=\frac{1}{2}[s\left(t\right)\cos (-{\mathrm{\ω}}_{h}t)+s\left(t\right)\cos (2{\mathrm{\ω}}_c+{\mathrm{\ω}}_h)t-\hat{s}\left(t\right)\sin (-{\mathrm{\ω}}_{h}t)-\hat{s}\left(t\right)\sin (2{\mathrm{\ω}}_c+{\mathrm{\ω}}_h)t]$

Wherein, ω _hCorresponding to this RF signal S _Ssb(t) half frequency values of bandwidth, it is a base band frequency.This first output signal I is a zero intermediate frequency signals, and it has ω _hBaseband signal and (2 ω near the frequency _c+ ω _h) near the intermediate-freuqncy signal of frequency.

(4) RF signal S after 140 pairs of amplifications of this second frequency mixer _Ssb(t) with second local oscillation signal the sin ((ω _c+ ω _h)) t carries out mixing to produce this second output signal Q.

$Q=s_{\mathrm{ssb}}\left(t\right)\sin (-({\mathrm{\ω}}_c+{\mathrm{\ω}}_h))t=(s\left(t\right)\cos \left({\mathrm{\ω}}_{c}t\right)-\hat{s}\left(t\right)\sin \left({\mathrm{\ω}}_{c}t\right))\sin (-({\mathrm{\ω}}_c+{\mathrm{\ω}}_h)t)$

$=\frac{1}{2}[-s\left(t\right)\sin (2{\mathrm{\ω}}_c+{\mathrm{\ω}}_h)t+s\left(t\right)\sin (-{\mathrm{\ω}}_h)t-\hat{s}\left(t\right)\cos ({2\mathrm{\ω}}_c+{\mathrm{\ω}}_h)t+\hat{s}\left(t\right)\cos (-{\mathrm{\ω}}_h)t]$

This second output signal Q is a zero intermediate frequency signals, and it has ω _hBaseband signal and (2 ω near the frequency _c+ ω _h) near the intermediate-freuqncy signal of frequency.

(5) utilize 150 couples of these the first output signal I of low pass filter and the second output signal Q to carry out low-pass filtering, removing its intermediate frequency composition (is to filter out correspondence (2 ω herein _c+ ω _h) near the relevant signal of frequency), thereby produce the first baseband signal I_channel and the second baseband signal Q_channel, promptly

$I\_\mathrm{channel}=\frac{1}{2}[s\left(t\right)\cos (-{\mathrm{\ω}}_h)t-\hat{s}\left(t\right)\sin (-{\mathrm{\ω}}_h)t]=\frac{1}{2}[s\left(t\right)\cos {\mathrm{\ω}}_{h}t+\hat{s}\left(t\right)\sin {\mathrm{\ω}}_{h}t]$

$Q\_\mathrm{channel}=\frac{1}{2}[s\left(t\right)\sin (-{\mathrm{\ω}}_h)t+\hat{s}\left(t\right)\cos (-{\mathrm{\ω}}_h)t]=\frac{1}{2}[-s\left(t\right)\sin {\mathrm{\ω}}_{h}t+\hat{s}\left(t\right)\cos {\mathrm{\ω}}_{h}t]$

This first baseband signal I_channel and the second baseband signal Q_channel are the baseband signal near 0 frequency, and corresponding to (2 ω _c+ ω _h) near the signal of correlated frequency be low pass filtering device 150 filterings.

(6) utilize 160 couples of these the first baseband signal I_channel of analog to digital converter and the second baseband signal Q_channel to carry out digitized processing, and the baseband signal I_channel after the digitized processing and the second baseband signal Q_channel are transferred to digital signal processor 170 handle to restore original video signal.

Concrete, see also Fig. 6, at first utilize this digital signal processor 170 to integrate this first baseband signal I_channel and this second baseband signal Q_channel, thereby generate one first processing signals S _{Ssb0_lowpass}(t), this first processing signals S _{Ssb0_lowpass}(t) be a complex signal, wherein this first baseband signal I_channel is as this first processing signals S _{Ssb0_lowpass}(t) real part, and this second baseband signal is as this first processing signals S _{Ssb0_lowpass}(t) imaginary part, that is:

${\mathrm{<figure-callout\; id="0"\; label="S\; ssb"\; filenames="S2008100816391E00041.png,S2008100816391E00051.png"\; state="\{\{state\}\}">S</figure-callout>}}_{\mathrm{ssb}}\left(t\right)=I\_\mathrm{channel}+\mathrm{jQ}\_\mathrm{channel}$

$=\frac{1}{2}\left\{\right[s\left(t\right)\cos (-{\mathrm{\&omega;}}_h)t-\hat{s}\left(t\right)\sin (-{\mathrm{\&omega;}}_h)t]+j[s\left(t\right)\sin (-{\mathrm{\&omega;}}_h)t+\hat{s}\left(t\right)\cos (-{\mathrm{\&omega;}}_h)t\left]\right\}$

$=\frac{1}{2}\left\{\right[s\left(t\right)\cos {\mathrm{\&omega;}}_{h}t+\hat{s}\left(t\right)\sin {\mathrm{\&omega;}}_{h}t]+j[-s\left(t\right)\sin {\mathrm{\&omega;}}_{h}t+\hat{s}\left(t\right)\cos {\mathrm{\&omega;}}_{h}t\left]\right\}$

And, this first processing signals S _{Ssb0_lowpass}(t) be one and be positioned near the baseband signal of zero frequency.

See also Fig. 7, then, utilize this digital signal processor 170 to continue this first processing signals S _{Ssb0_lowpass}(t) proceed to handle, to obtain second processing signals

This second processing signals For utilizing this digital signal processor 170 with this first processing signals S _{Ssb0_lowpass}(t) with a ω _hThe plural number of frequency (Complex Number) signal carries out mixing and produces, i.e. this second processing signals

Be the first processing signals S _{Ssb0_lowpass}(t) with

Product, therefore,

${\mathrm{<figure-callout\; id="0"\; label="s\; ssb"\; filenames="S2008100816391E00041.png,S2008100816391E00051.png"\; state="\{\{state\}\}">s</figure-callout>}}_{\mathrm{ssb}}\left(t\right)={\mathrm{<figure-callout\; id="0"\; label="S\; ssb"\; filenames="S2008100816391E00041.png,S2008100816391E00051.png"\; state="\{\{state\}\}">S</figure-callout>}}_{\mathrm{ssb}}\left(t\right)\&CenterDot;w^{j{\mathrm{\&omega;}}_{h}t}$

$=\frac{1}{2}\left\{\right[s\left(t\right)\cos (-{\mathrm{\&omega;}}_h)t-\hat{s}\left(t\right)\sin (-{\mathrm{\&omega;}}_h)t]+j[s\left(t\right)\sin (-{\mathrm{\&omega;}}_h)t+\hat{s}\left(t\right)\cos (-{\mathrm{\&omega;}}_h)t\left]\right\}\&CenterDot;(\cos {\mathrm{\&omega;}}_{h}t+j\sin {\mathrm{\&omega;}}_{h}t)$

$=\frac{1}{2}\left[(s\left(t\right)\cos {\mathrm{\&omega;}}_{h}t+\hat{s}\left(t\right)\sin {\mathrm{\&omega;}}_{h}t+j(-s\left(t\right)\sin {\mathrm{\&omega;}}_{h}t+\hat{s}\left(t\right)\cos {\mathrm{\&omega;}}_{h}t))\right]\&CenterDot;(\cos {\mathrm{\&omega;}}_{h}t+j\sin {\mathrm{\&omega;}}_{h}t)$

$=\frac{1}{2}[s\left(t\right)({\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="S2008100816391E00041.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\mathrm{\&omega;}}_{h}t+{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="S2008100816391E00041.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2{\mathrm{\&omega;}}_{h}t)+j\hat{s}\left(t\right)({\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="S2008100816391E00041.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\mathrm{\&omega;}}_{h}t+{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="S2008100816391E00041.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2{\mathrm{\&omega;}}_{h}t)$

$=\frac{1}{2}[s\left(t\right)+j\hat{s}\left(t\right)]$

As shown in Figure 7, this second processing signals

Be the analytic signal of a plural number, utilize 170 pairs of these second processing signals of this digital signal processor

Get real part and calculate, this is vision signal s (t) about zero frequency yoke rice symmetry on frequency spectrum thereby reduce, promptly

$s\left(t\right)=2\&CenterDot;\mathrm{Re}\left\{s_{\mathrm{<figure-callout\; id="0"\; label="ssb"\; filenames="S2008100816391E00041.png,S2008100816391E00051.png"\; state="\{\{state\}\}">ssb</figure-callout>}0\_\mathrm{lowpass}\_\mathrm{shift}{\mathrm{\&omega;}}_h}\left(t\right)\right\}=2\&CenterDot;\mathrm{Re}\left\{\frac{1}{2}\right[s\left(t\right)+j\hat{s}\left(t\right)\left]\right\}=s\left(t\right)$

What certainly can understand is also can produce second processing signals

The time this digital signal processor 170 it got real part calculate, thereby reduce this vision signal s (t), that is to say this first processing signals S _{Ssb0_lowpass}(t) be ω with frequency _hComplex signal carry out mixing simultaneously, this digital signal processor 170 is got real part to it and is calculated, promptly

$s\left(t\right)=2\&CenterDot;\mathrm{Re}\left\{\frac{1}{2}\right[(s\left(t\right)\cos (-{\mathrm{\&omega;}}_h)t-\hat{s}\left(t\right)\sin \left({-\mathrm{\&omega;}}_h\right)t)+j(s\left(t\right)\sin \left({-\mathrm{\&omega;}}_h\right)t+\hat{s}\left(t\right)\cos \left({-\mathrm{\&omega;}}_h\right)t)]\&CenterDot;(\cos {\mathrm{\&omega;}}_{h}t+j\sin {\mathrm{\&omega;}}_{h}t)$

$=2\&CenterDot;\mathrm{Re}\left\{\frac{1}{2}\right[(s\left(t\right)\cos {\mathrm{\&omega;}}_{h}t+\hat{s}\left(t\right)\sin {\mathrm{\&omega;}}_{h}t+j(-s\left(t\right)\sin {\mathrm{\&omega;}}_{h}t+\hat{s}\left(t\right)\cos {\mathrm{\&omega;}}_{h}t))]\&CenterDot;(\cos {\mathrm{\&omega;}}_{h}t+j\sin {\mathrm{\&omega;}}_{h}t)\}$

$=2\&CenterDot;\mathrm{Re}\left\{\frac{1}{2}\right[s\left(t\right)({\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="S2008100816391E00041.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\mathrm{\&omega;}}_{h}t+{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="S2008100816391E00041.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2{\mathrm{\&omega;}}_{h}t)+j\hat{s}\left(t\right)({\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="S2008100816391E00041.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\mathrm{\&omega;}}_{h}t+{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="S2008100816391E00041.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2{\mathrm{\&omega;}}_{h}t)\left]\right\}$

$=2\&CenterDot;\frac{1}{2}\left[s\left(t\right)\right]=s\left(t\right)$

Certainly, step of the present invention (3)-(6) also can be understood as this RF signal S _Ssb(t) thus generated as shown in Figure 6 an intermediate treatment signal S by first frequency mixer 130 and second frequency mixer 140 back _Ssb0(t), this intermediate treatment signal S _Ssb0(t) be this RF signal S _Ssb(t) with a frequency be-(ω _c+ ω _h) complex signal carry out mixing, i.e. this intermediate treatment signal S _Ssb0(t) be this RF signal S _Ssb(t) with

Product, therefore, this intermediate treatment signal S _Ssb0(t) be

$s_{\mathrm{ssb}0}\left(t\right)=s_{\mathrm{ssb}}\left(t\right)e^{-j({\mathrm{\&omega;}}_c+{\mathrm{\&omega;}}_h)}t$

$=\frac{1}{2}[(s\left(t\right)\cos \left({-\mathrm{\&omega;}}_h\right)t+s\left(t\right)\cos (2{\mathrm{\&omega;}}_c+{\mathrm{\&omega;}}_h)t-\hat{s}\left(t\right)\sin \left({-\mathrm{\&omega;}}_h\right)t-\hat{s}\left(t\right)\sin (2{\mathrm{\&omega;}}_c+{\mathrm{\&omega;}}_h)t)$

$+j(s\left(t\right)\sin \left({-\mathrm{\&omega;}}_h\right)t-s\left(t\right)\sin (2{\mathrm{\&omega;}}_c+{\mathrm{\&omega;}}_h)t+\hat{s}\left(t\right)\cos \left({-\mathrm{\&omega;}}_h\right)t)-\hat{s}\left(t\right)\cos (2{\mathrm{\&omega;}}_c+{\mathrm{\&omega;}}_h)t\left)\right]$

Please intermediate treatment signal S _Ssb0During (t) by this low pass filter 150, filter out (2 ω _c+ ω _h) near the relevant signal of frequency, thereby obtain this first processing signals S _{Ssb0_lowpass}(t), and then to this first processing signals S _{Ssb0_lowpass}(t) carry out relevant treatment, thereby obtain second processing signals And vision signal s (t).

The ATSC that is applicable to of the present invention, NTSC, PAL, SECAM, the demodulator 100 of VSB and SSB modular system and corresponding demodulation method are directly with RF signal S _Ssb(t) be converted to zero intermediate frequency signals (intermediate treatment signal S _Ssb0(t)), utilize low pass filter 150 to get rid of intermediate-freuqncy signal ((2 ω then _c+ ω _h) near the relevant signal frequency), only allow baseband signal (the first processing signals S _{Ssb0_lowpass}(t)) by this low pass filter 150, again baseband signal is handled, thereby restored vision signal s (t).

Compared to prior art, the ATSC that is applicable to of the present invention, NTSC, PAL, SECAM, the demodulator 100 of VSB and SSB modular system and corresponding demodulation method, it adopts low pass filter 150 to get final product, it does not need the sharpening band to lead to (intermediate frequency) filter, and low pass filter 150 leads to (intermediate frequency) filter compared to the sharpening band, and its circuit is comparatively simple, the electronic component that needs is less, consumed energy is few, and can be integrated on an integrated chip or the integrated circuit, is fit to the needs of present integrated circuit high integration.

In addition, those skilled in the art also can do other variation in spirit of the present invention, as long as it does not depart from technique effect of the present invention and all can.The variation that these are done according to spirit of the present invention all should be included within the present invention's scope required for protection.

Claims (7)

1. demodulator, it is used for ATSC, NTSC, PAL, SECAM, VSB and SSB modular system, this demodulator comprises:

One is used for the antenna of received RF signal;

One low noise amplifier that is electrically connected with antenna, this low noise amplifier are used for the received radiofrequency signal of antenna is amplified;

One first frequency mixer, it is electrically connected to this low noise amplifier so that the radiofrequency signal of this amplification and one first local oscillation signal carry out mixing to produce one first output signal;

One second frequency mixer, it is electrically connected to this low noise amplifier so that the radiofrequency signal of this amplification and one second local oscillation signal carry out mixing to produce one second output signal, this second local oscillation signal and the first local oscillation signal quadrature;

One low pass filter, it is electrically connected to this first frequency mixer and this second frequency mixer respectively so that this first output signal and second output signal are carried out low-pass filtering, and this low pass filter filters out intermediate frequency composition in this first output signal and this second output signal to produce one first baseband signal and one second baseband signal respectively; And

One signal processor, it forms to be electrically connected so that this first baseband signal and this second baseband signal are handled with reduction with this low pass filter and obtains original video signal, wherein, thereby this signal processor is handled this first baseband signal and this second baseband signal and is obtained one first processing signals, this first processing signals is a real part with first baseband signal, with second baseband signal is imaginary part, and this signal processor is ω with this first processing signals and a frequency also _hComplex signal carry out mixing, thereby obtain one second processing signals, calculate reduction and obtain this vision signal, ω thereby this second processing signals is got real part _hCorresponding to half frequency values of this radiofrequency signal bandwidth, it is a base band frequency.

2. demodulator as claimed in claim 1, it is characterized in that, further comprise an analog to digital converter, this analog to digital converter is connected electrically between this low pass filter and this signal processor so that form between this signal processor and this low pass filter and be electrically connected, this analog to digital converter transfers to this signal processor and handles after first baseband signal that this low pass filter produced and second baseband signal are carried out digitized processing.

3. demodulator as claimed in claim 2 is characterized in that, this signal processor is a digital signal processor.

4. demodulation method, it is used for ATSC, NTSC, PAL, SECAM, VSB and SSB modular system, it comprises this conciliation method:

Utilize an antenna received RF signal, this radiofrequency signal is that a vision signal and a carrier wave are modulated and generated;

Utilize a low noise amplifier that the received radiofrequency signal of antenna is amplified;

The radiofrequency signal and one first local oscillation signal of this amplification are carried out mixing to produce one first output signal;

The radiofrequency signal and one second local oscillation signal of this amplification are carried out mixing to produce one second output signal, this second local oscillation signal and this first local oscillation signal quadrature;

This first output signal is carried out low-pass filtering, and the intermediate frequency composition that filters out this first output signal is to produce one first baseband signal;

This second output signal is carried out low-pass filtering, and the intermediate frequency composition that filters out this second output signal is to produce one second baseband signal;

Utilize a signal processor to handle this first baseband signal and this second baseband signal and obtain original video signal with reduction, wherein, thereby this signal processor is handled this first baseband signal and this second baseband signal and is obtained one first processing signals, this first processing signals is a real part with first baseband signal, with second baseband signal is imaginary part, and this signal processor is ω with this first processing signals and a frequency also _hComplex signal carry out mixing, thereby obtain one second processing signals, calculate reduction and obtain this vision signal, ω thereby this second processing signals is got real part _hCorresponding to half frequency values of this radiofrequency signal bandwidth, it is a base band frequency.

5. demodulation method as claimed in claim 4 is characterized in that this carrier wave has positive frequency f _c

6. demodulation method as claimed in claim 4 is characterized in that, the frequency of this first local oscillation signal and second local oscillation signal is-(ω _c+ ω _h).

7. demodulation method as claimed in claim 4 is characterized in that, this first output signal is a zero intermediate frequency signals, and it has a baseband signal and an intermediate-freuqncy signal; This second output signal also is a zero intermediate frequency signals, and it also has a baseband signal and an intermediate-freuqncy signal.

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