CN101908896B - 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, the frequency conversion structure that relates in particular to a kind of radio-frequency transmitter applicable to multi-mode satellite navigation navigation system and multi-mode wireless communications system and be applicable to them.

Background technology

On the present navigator fix market, the navigation system that has this various modes, comprise the GPS of the U.S., 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 structural 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 suppresses image signal with mirror filter 101 exactly before down-conversion.But because the IF-FRE in this structure is generally lower, so that mirror filter must reach higher inhibiting rate and very high exponent number.In order to alleviate the 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 two local frequencies 201,202 choose, can establish the frequency of the first intermediate frequency higher, can greatly alleviate like this requirement to mirror filter 203.But the problem of bringing simultaneously is that a plurality of elements of needs especially need two independently frequency synthesizers.

Summary of the invention

The technical problem that (one) 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 band, this multi-frequency band radio-frequency receiver comprises the first frequency mixer 302, the first intermediate-frequency filter 301, the 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 the first frequency mixer 302, radiofrequency signal is transformed on the first intermediate-frequency band, exports to afterwards the first intermediate-frequency filter 301; The repeatedly clutter that the first intermediate-frequency filter 301 filtering multi-band signals disturb and produce because of the first frequency mixer 302 non-ideal factors is exported to the second frequency mixer 303; Also enter into the second frequency mixer 303 behind the frequency reference signal process n frequency divider 305 that frequency synthesizer 304 provides, become the second local oscillation signal; The 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 inputting from n frequency divider 305 of the 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 the first intermediate-freuqncy signal is f _IF1, the frequency of the first local oscillation signal is f _LO1, the frequency of the 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:

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

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

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

In the such scheme, the selection of described the first local oscillation signal has two kinds: $f_{\mathrm{LO}1}=\frac{n}{n+1}(f_{\mathrm{RF}}+f_{\mathrm{IF}})$ With $f_{\mathrm{LO}1}=\frac{n}{n+1}(f_{\mathrm{RF}}-f_{\mathrm{IF}}),$ Then at the first local oscillation signal be $f_{\mathrm{LO}1}=\frac{n}{n+1}(f_{\mathrm{RF}}+f_{\mathrm{IF}})$ The time, the frequency of described the first intermediate-freuqncy signal $f_{\mathrm{IF}1}=\frac{1}{n+1}{f}_{\mathrm{RF}}-\frac{n}{n+1}{f}_{\mathrm{IF}};$ At the first local oscillation signal be $f_{\mathrm{LO}1}=\frac{n}{n+1}(f_{\mathrm{RF}}-f_{\mathrm{IF}})$ The time, the frequency of described the first intermediate-freuqncy signal $f_{\mathrm{IF}1}=\frac{1}{n+1}{f}_{\mathrm{RF}}+\frac{n}{n+1}{f}_{\mathrm{IF}}.$

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

Its first IF-FRE is

For the low-frequency range radiofrequency signal, the reference frequency of frequency synthesizer need to 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 needs so that the first IF-FRE of this moment drops between two above-mentioned the first IF-FRE and gets 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 flexibly local frequency, 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 second frequency conversion superheterodyne receiver structure chart 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 band, this multi-frequency band radio-frequency receiver comprises the first frequency mixer 302, the first intermediate-frequency filter 301, the 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 the first frequency mixer 302, radiofrequency signal is transformed on the first intermediate-frequency band, exports to afterwards the first intermediate-frequency filter 301; The repeatedly clutter that the first intermediate-frequency filter 301 filtering multi-band signals disturb and produce because of the first frequency mixer 302 non-ideal factors is exported to the second frequency mixer 303; Also enter into the second frequency mixer 303 behind the frequency reference signal process n frequency divider 305 that frequency synthesizer 304 provides, become the second local oscillation signal; The 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 inputting from n frequency divider 305 of the first intermediate-frequency filter 301 inputs, and carrier signal is converted to intermediate-freuqncy signal output.

Analyze take input signal as single frequency point signal, behind radiofrequency signal process low noise amplifier and the filter, the local oscillation signal that provides with frequency synthesizer 304 in the first frequency mixer 302 carries out the down-conversion first time, afterwards by the first intermediate-frequency filter 301, arrive in the second frequency mixer 303, simultaneously the frequency reference signal that provides of frequency synthesizer 304 also enters into the 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 the second frequency mixer provides local oscillation signal except for the first frequency mixer provides local oscillation signal.

Local frequency planning of the present invention is when the radiofrequency signal of input is a plurality of frequency range, needs to select the reference frequency signal of suitable frequency synthesizer output, so that the bandwidth that the first intermediate-freuqncy signal occupies is minimum, alleviates the pressure of the 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 the first intermediate-freuqncy signal is f _IF1, the frequency of the local oscillation signal of the first frequency mixer input is f _LO1, the frequency of the local oscillation signal of the second frequency mixer input is f _LO2, the frequency dividing ratio of frequency divider is n, for the first frequency mixer 302, has f _IF1=| f _RF-f _LO1|, two kinds of forms are namely arranged, f _IF1=f _RF-f _LO1And f _IF1=f _LO1-f _RFFor the 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, only has in the relation that the first frequency mixer exists here: f _IF1=f _RF-f _LO1Consider whole link, have two kinds of frequency allocation methods, a kind ofly be:

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

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

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

Another kind is:

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

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

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

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 emphatically consideration is exactly the problem of the first intermediate-frequency filter 301, at this moment, the effect of the first intermediate-frequency filter 301 is not only the repeatedly clutter that filtering produces because of the first frequency mixer 302 non-ideal factors, also will suppress as best one can the interference of other frequency ranges, this is so that the bandwidth of the first intermediate-frequency filter 301 is narrow as much as possible.But under receiver structure of the present invention, under the multi-band signal input, the 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, so that the bandwidth of the first IF-FRE that multi-band signal produces is minimum.Concrete implementation method is as follows:

For the high band radiofrequency signal, the reference frequency of frequency synthesizer need to be set to Its first IF-FRE is

For the low-frequency range radiofrequency signal, the reference frequency of frequency synthesizer need to 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 needs so that the first IF-FRE of this moment drops between two above-mentioned the first IF-FRE and gets 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 making, 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 band, it is characterized in that this multi-frequency band radio-frequency receiver comprises the first frequency mixer (302), the first intermediate-frequency filter (301), the second frequency mixer (303), frequency synthesizer (304) and n frequency divider (305);

Wherein, behind radiofrequency signal process low noise amplifier and the filter, the the first local oscillation signal mixing that in the 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 band, exports to afterwards the first intermediate-frequency filter (301); The repeatedly clutter that the first intermediate-frequency filter (301) filtering multi-band signal disturbs and produces because of the first frequency mixer (302) non-ideal factor is exported to the second frequency mixer (303); Also enter into the second frequency mixer (303) behind the frequency reference signal process n frequency divider (305) that frequency synthesizer (304) provides, become the second local oscillation signal; The 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 inputting from n frequency divider (305) of the 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 the first intermediate-freuqncy signal is f _IF1, the frequency of the first local oscillation signal is f _LO1, the frequency of the second local oscillation signal is f _LO2, the frequency dividing ratio of frequency divider is n, then arbitrary group in the satisfied following two groups of relational expressions of above-mentioned each frequency:

One group is:

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

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

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

Another group is:

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

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

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

3. multi-frequency band radio-frequency receiver according to claim 1 is characterized in that, the selection of described the first local oscillation signal has two kinds: $f_{\mathrm{LO}1}=\frac{n}{n+1}(f_{\mathrm{RF}}+f_{\mathrm{IF}})$ With $f_{\mathrm{LO}1}=\frac{n}{n+1}(f_{\mathrm{RF}}-f_{\mathrm{IF}}),$ Then at the first local oscillation signal be $f_{\mathrm{LO}1}=\frac{n}{n+1}(f_{\mathrm{RF}}+f_{\mathrm{IF}})$ The time, the frequency of described the first intermediate-freuqncy signal $f_{\mathrm{IF}1}=\frac{1}{n+1}{f}_{\mathrm{RF}}-\frac{n}{n+1}{f}_{\mathrm{IF}};$ At the first local oscillation signal be $f_{\mathrm{LO}1}=\frac{n}{n+1}(f_{\mathrm{RF}}-f_{\mathrm{IF}})$ The time, the frequency of described the first intermediate-freuqncy signal $f_{\mathrm{IF}1}=\frac{1}{n+1}{f}_{\mathrm{RF}}+\frac{n}{n+1}{f}_{\mathrm{IF}}.$

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, so that the bandwidth that the first intermediate-freuqncy signal occupies is minimum; For the high band radiofrequency signal, the reference frequency of frequency synthesizer need to be set to

Its first IF-FRE is

For the low-frequency range radiofrequency signal, the reference frequency of frequency synthesizer need to 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 needs so that the first IF-FRE of this moment drops between two above-mentioned the first IF-FRE and gets 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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