CN101908896A - Multi-frequency band radio-frequency receiver - Google Patents

Abstract

The invention discloses a multi-frequency band radio-frequency receiver, which is used for switching radio-frequency carriers of multiple frequency bands onto the same intermediate-frequency band. The multi-frequency band radio-frequency receiver comprises a first frequency mixer (302), a first intermediate-frequency filter (301), a second frequency mixer (303), a frequency synthesizer (304) and n frequency dividers (305). A radio-frequency signal is mixed twice, down-converted twice and converted into a needed intermediate frequency for output. Apart from providing a local oscillation signal for the first frequency mixer, the frequency synthesizer provides the local oscillation signal to the second frequency mixer through the frequency divider. The receiver provided by the invention adopts a flexible local frequency scheme, so that the requirement of a multi-frequency band radio-frequency signal on the filter after first frequency conversion can be lowered.

Description

A kind of multi-frequency band radio-frequency receiver

Technical field

The present invention relates to the radio-frequency transmitter technical field, relate in particular to a kind of applicable to the radio-frequency transmitter of multi-mode satellite navigation navigation system and multi-mode wireless communications system and the frequency conversion structure that is applicable to them.

Background technology

On the present navigator fix market, the navigation system that has this various modes, comprise GPS of USA, Galileo, the Muscovite GLONASS in Europe and the Big Dipper of China's independent development, the navigation positioning system of various modes is exactly a plurality of frequency ranges that need to cover various patterns for the requirement of radio-frequency front-end.Equally, for present various modes wireless communication system, the design of receiver also needs to satisfy this generic request.

Super-heterodyne architecture receiver in the traditional scheme is to use more a kind of system configuration, basic principle as shown in Figure 1, radiofrequency signal is through amplifying and frequency down-converts is that a fixing intermediate-freuqncy signal is exported.In case the shortcoming of this structure maximum is exactly to have image signal, image signal will with the local oscillator mixing, export identical intermediate frequency, disturb useful signal.The unique way that solves this interference is exactly to use mirror filter 101 to suppress image signal before down-conversion.But, make mirror filter must reach than high inhibitory and very high exponent number because the IF-FRE in this structure is generally lower.In order to alleviate requirement to mirror filter, can adopt the double conversion structure, as shown in Figure 2, radiofrequency signal is through being converted to fixing intermediate-freuqncy signal output behind the double conversion.By to the choosing of two local frequencies 201,202, can establish the frequency of first intermediate frequency than higher, can alleviate requirement so greatly to mirror filter 203.But the problem of bringing simultaneously is that a plurality of elements of needs especially need two independent frequency synthesizers.

Summary of the invention

(1) technical problem that will solve

For the requirement of satisfying the receiver module miniaturization reduces simultaneously to the requirement of multi-band signal to filter, main purpose of the present invention is to provide a kind of multi-frequency band radio-frequency receiver of miniaturization.

(2) technical scheme

For achieving the above object, the invention provides a kind of multi-frequency band radio-frequency receiver, be used for the radio-frequency carrier of a plurality of frequency ranges is transformed into same intermediate frequency frequency range, this multi-frequency band radio-frequency receiver comprises first frequency mixer 302, first intermediate-frequency filter 301, second frequency mixer 303, frequency synthesizer 304 and n frequency divider 305; Wherein, behind radiofrequency signal process low noise amplifier and the filter, the down-conversion first time is carried out in the first local oscillation signal mixing that provides with frequency synthesizer 304 in first frequency mixer 302, radiofrequency signal is transformed on the first intermediate frequency frequency range, exports to first intermediate-frequency filter 301 afterwards; The repeatedly clutter that first intermediate-frequency filter, 301 filtering multi-band signals disturb and produce because of first frequency mixer, 302 non-ideal factors is exported to second frequency mixer 303; Also enter into second frequency mixer 303 behind the frequency reference signal process n frequency divider 305 that frequency synthesizer 304 provides, become second local oscillation signal; Second frequency mixer 303 will carry out the down-conversion second time from first intermediate-freuqncy signal and the second local oscillation signal mixing of importing from n frequency divider 305 of first intermediate-frequency filter, 301 inputs, and carrier signal is converted to intermediate-freuqncy signal output.

In the such scheme, the frequency of supposing described radiofrequency signal is f _RF, the frequency of the intermediate-freuqncy signal of final output is f _IF, the frequency of first intermediate-freuqncy signal is f _IF1, the frequency of first local oscillation signal is f _LO1, the frequency of second local oscillation signal is f _LO2, the frequency dividing ratio of frequency divider is n, then above-mentioned each frequency satisfies following relational expression:

$f_{\mathrm{LO}1}=\frac{n}{n+1}\left(f_{\mathrm{RF}}{\±f}_{\mathrm{IF}}\right)$

$f_{\mathrm{LO}2}=\frac{1}{n+1}\left(f_{\mathrm{RF}}{\±f}_{\mathrm{IF}}\right)$

$f_{\mathrm{IF}1}=f_{\mathrm{RF}}-f_{\mathrm{LO}1}=\frac{1}{n+1}{f}_{\mathrm{RF}}\stackrel{\‾}{+}\frac{n}{n+1}{f}_{\mathrm{IF}}.$

In the such scheme, the selection of described first local oscillation signal has two kinds:

With

Then be at first local oscillation signal

The time, the frequency of described first intermediate-freuqncy signal At first local oscillation signal be The time, the frequency of described first intermediate-freuqncy signal

In the such scheme, when the radiofrequency signal of input is a plurality of frequency range, need to select suitable local oscillation signal, the bandwidth minimum that the intermediate-freuqncy signal of winning is occupied; For the high band radiofrequency signal, the reference frequency of frequency synthesizer need be set to

Its first IF-FRE is

For the low-frequency range radiofrequency signal, the reference frequency of frequency synthesizer need be set to

Its first IF-FRE is

For the radiofrequency signal of intermediate bands, the setting of the reference frequency of frequency synthesizer only need make first IF-FRE of this moment drop between two the first above-mentioned IF-FRE and get final product.

In the such scheme, described multi-band signal is not received simultaneously, and the reference frequency of the output by selecting frequency synthesizer receives at times.

(3) beneficial effect

Multi-frequency band radio-frequency receiver provided by the invention by adopting local frequency flexibly, can reduce the requirement to filter after the frequency conversion first time of multi-frequency band radio-frequency signal.

Description of drawings

Fig. 1 is the structural representation of superheterodyne receiver system traditional in the prior art;

Fig. 2 is the structural representation of the superheterodyne receiver of double conversion in the prior art;

Fig. 3 is miniaturization double superheterodyne receiver structure figure provided by the invention.

Embodiment

For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.

As shown in Figure 3, multi-frequency band radio-frequency receiver provided by the invention, be used for the radio-frequency carrier of a plurality of frequency ranges is transformed into same intermediate frequency frequency range, this multi-frequency band radio-frequency receiver comprises first frequency mixer 302, first intermediate-frequency filter 301, second frequency mixer 303, frequency synthesizer 304 and n frequency divider 305.Wherein, behind radiofrequency signal process low noise amplifier and the filter, the down-conversion first time is carried out in the first local oscillation signal mixing that provides with frequency synthesizer 304 in first frequency mixer 302, radiofrequency signal is transformed on the first intermediate frequency frequency range, exports to first intermediate-frequency filter 301 afterwards; The repeatedly clutter that first intermediate-frequency filter, 301 filtering multi-band signals disturb and produce because of first frequency mixer, 302 non-ideal factors is exported to second frequency mixer 303; Also enter into second frequency mixer 303 behind the frequency reference signal process n frequency divider 305 that frequency synthesizer 304 provides, become second local oscillation signal; Second frequency mixer 303 will carry out the down-conversion second time from first intermediate-freuqncy signal and the second local oscillation signal mixing of importing from n frequency divider 305 of first intermediate-frequency filter, 301 inputs, and carrier signal is converted to intermediate-freuqncy signal output.

With the input signal is that single frequency point signal is analyzed, behind radiofrequency signal process low noise amplifier and the filter, the local oscillation signal that provides with frequency synthesizer 304 in first frequency mixer 302 carries out the down-conversion first time, afterwards by first intermediate-frequency filter 301, arrive in second frequency mixer 303, simultaneously the frequency reference signal that provides of frequency synthesizer 304 also enters into second frequency mixer after through a n frequency divider, becomes local oscillation signal.Desired intermediate-freuqncy signal is finally exported in the mixing of two signal phases.The system schema of multi-frequency band radio-frequency receiver of the present invention comprises receiver structure and local frequency planning two parts.

Receiver structure of the present invention (as shown in Figure 3) than the super-heterodyne architecture (as shown in Figure 2) of double conversion, has lacked a frequency synthesizer, replaces to use a n frequency divider.Remaining frequency synthesizer also will pass through the n frequency divider with n frequency division of signal, for second frequency mixer provides local oscillation signal except for first frequency mixer provides local oscillation signal.

Local frequency of the present invention planning is when the radiofrequency signal of input is a plurality of frequency range, needs the reference frequency signal of selecting suitable frequency synthesizer to export, and the bandwidth minimum that the intermediate-freuqncy signal of winning is occupied alleviates the pressure of first intermediate-frequency filter 301.

If the frequency of radiofrequency signal is f _RF, the frequency of the intermediate-freuqncy signal of final output is f _IF, the frequency of first intermediate-freuqncy signal is f _IF1, the frequency of the local oscillation signal of first frequency mixer input is f _LO1, the frequency of the local oscillation signal of second frequency mixer input is f _LO2, the frequency dividing ratio of frequency divider is n, for first frequency mixer 302, has f _IF1=| f _RF-f _LO1|, two kinds of forms are promptly arranged, f _IF1=f _RF-f _LO1And f _IF1=f _LO1-f _RFFor second frequency mixer 303, there is f _IF=| f _IF1-f _LO2|, two kinds of forms are equally also arranged, f _IF=f _IF1-f _LO2And f _IF=f _LO2-f _IF1For frequency divider, there is f _LO1=nf _LO2Angle for cost and the final complexity that realizes is considered, generally selects the output frequency frequency synthesizer scheme lower than the frequency of radiofrequency signal, therefore, has only in the relation that first frequency mixer exists here: f _IF1=f _RF-f _LO1Take all factors into consideration whole link, have two kinds of frequency allocation methods, a kind ofly be:

$f_{\mathrm{LO}1}=\frac{n}{n+1}\left(f_{\mathrm{RF}}{+f}_{\mathrm{IF}}\right)$

$f_{\mathrm{LO}2}=\frac{1}{n+1}\left(f_{\mathrm{RF}}{+f}_{\mathrm{IF}}\right)$

$f_{\mathrm{IF}1}=f_{\mathrm{RF}}-f_{\mathrm{LO}1}=\frac{1}{n+1}{f}_{\mathrm{RF}}-\frac{n}{n+1}{f}_{\mathrm{IF}}.$

Another kind is:

$f_{\mathrm{LO}1}=\frac{n}{n+1}\left(f_{\mathrm{RF}}{-f}_{\mathrm{IF}}\right)$

$f_{\mathrm{LO}2}=\frac{1}{n+1}\left(f_{\mathrm{RF}}{-f}_{\mathrm{IF}}\right)$

$f_{\mathrm{IF}1}=f_{\mathrm{RF}}-f_{\mathrm{LO}1}=\frac{1}{n+1}{f}_{\mathrm{RF}}+\frac{n}{n+1}{f}_{\mathrm{IF}}.$

When input was multi-band signal, under receiver structure of the present invention, multi-band signal received at times by the reference frequency of the output of selection frequency synthesizer.What need consideration emphatically is exactly the problem of first intermediate-frequency filter 301, at this moment, the effect of first intermediate-frequency filter 301 is not only the repeatedly clutter that filtering produces because of first frequency mixer, 302 non-ideal factors, also will suppress the interference of other frequency ranges as best one can, this makes the bandwidth of the intermediate-frequency filter 301 of winning narrow as much as possible.But under receiver structure of the present invention, under the multi-band signal input, first IF-FRE that produces is unfixing, therefore, can be according to two kinds of above-mentioned frequency allocation methods, reasonably select the frequency of frequency synthesizer, make the bandwidth minimum of first IF-FRE that multi-band signal produces.Concrete implementation method is as follows:

For the high band radiofrequency signal, the reference frequency of frequency synthesizer need be set to

Its first IF-FRE is

For the low-frequency range radiofrequency signal, the reference frequency of frequency synthesizer need be set to

Its first IF-FRE is

For the radiofrequency signal of intermediate bands, the setting of the reference frequency of frequency synthesizer only need make first IF-FRE of this moment drop between two the first above-mentioned IF-FRE and get final product.

Above-described specific embodiment; purpose of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the above only is specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (5)

1. multi-frequency band radio-frequency receiver, be used for the radio-frequency carrier of a plurality of frequency ranges is transformed into same intermediate frequency frequency range, it is characterized in that this multi-frequency band radio-frequency receiver comprises first frequency mixer (302), first intermediate-frequency filter (301), second frequency mixer (303), frequency synthesizer (304) and n frequency divider (305);

Wherein, behind radiofrequency signal process low noise amplifier and the filter, the first local oscillation signal mixing that in first frequency mixer (302), provides with frequency synthesizer (304), carry out the down-conversion first time, radiofrequency signal is transformed on the first intermediate frequency frequency range, exports to first intermediate-frequency filter (301) afterwards; The repeatedly clutter that first intermediate-frequency filter (301) filtering multi-band signal disturbs and produces because of first frequency mixer (302) non-ideal factor is exported to second frequency mixer (303); Also enter into second frequency mixer (303) behind the frequency reference signal process n frequency divider (305) that frequency synthesizer (304) provides, become second local oscillation signal; Second frequency mixer (303) will carry out the down-conversion second time from first intermediate-freuqncy signal and the second local oscillation signal mixing of importing from n frequency divider (305) of first intermediate-frequency filter (301) input, and carrier signal is converted to intermediate-freuqncy signal output.

2. multi-frequency band radio-frequency receiver according to claim 1 is characterized in that, the frequency of supposing described radiofrequency signal is f _RF, the frequency of the intermediate-freuqncy signal of final output is f _IF, the frequency of first intermediate-freuqncy signal is f _IF1, the frequency of first local oscillation signal is f _LO1, the frequency of second local oscillation signal is f _LO2, the frequency dividing ratio of frequency divider is n, then above-mentioned each frequency satisfies following relational expression:

$f_{\mathrm{LO}1}=\frac{n}{n+1}\left(f_{\mathrm{RF}}{\±f}_{\mathrm{IF}}\right)$

$f_{\mathrm{LO}2}=\frac{1}{n+1}\left(f_{\mathrm{RF}}{\±f}_{\mathrm{IF}}\right)$

$f_{\mathrm{IF}1}=f_{\mathrm{RF}}-f_{\mathrm{LO}1}=\frac{1}{n+1}{f}_{\mathrm{RF}}\stackrel{\‾}{+}\frac{n}{n+1}{f}_{\mathrm{IF}}.$

3. multi-frequency band radio-frequency receiver according to claim 1 is characterized in that, the selection of described first local oscillation signal has two kinds: With

Then be at first local oscillation signal

The time, the frequency of described first intermediate-freuqncy signal

At first local oscillation signal be

The time, the frequency of described first intermediate-freuqncy signal

4. multi-frequency band radio-frequency receiver according to claim 1 is characterized in that, when the radiofrequency signal of input is a plurality of frequency range, needs to select suitable local oscillation signal, the bandwidth minimum that the intermediate-freuqncy signal of winning is occupied; For the high band radiofrequency signal, the reference frequency of frequency synthesizer need be set to Its first IF-FRE is

For the low-frequency range radiofrequency signal, the reference frequency of frequency synthesizer need be set to

Its first IF-FRE is

For the radiofrequency signal of intermediate bands, the setting of the reference frequency of frequency synthesizer only need make first IF-FRE of this moment drop between two the first above-mentioned IF-FRE and get final product.

5. multi-frequency band radio-frequency receiver according to claim 4 is characterized in that described multi-band signal is not received simultaneously, and the reference frequency of the output by selecting frequency synthesizer receives at times.

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