JP2008271311A - Undesired wave removing receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive undesired wave removing receiver which separates a wireless communication signal into an upper-sideband signal and a lower-sideband signal, and removes a wanted wave and image. <P>SOLUTION: An undesired wave removing receiver is characterized in that a baseband converted wireless communication signal into an upper-sideband signal and a lower-sideband signal, and an undesired wave is removed by selecting, as a band to be used, any one of the upper-sideband signal, the lower-sideband signal and a double-sideband signal, on the basis of comparing an S/N of the single-sideband signal to an S/N of the double-sideband signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a receiver having a circuit process for removing unnecessary waves from a radio communication signal including a spread spectrum signal.

In a receiver that receives a wireless communication signal including a spread spectrum signal, a high frequency band (RF) signal is converted into an intermediate frequency (IF) band signal using at least one mixer, and then converted into a baseband signal again. A heterodyne system for conversion is widely used. Further, a method of directly converting an RF signal into a baseband signal by a direct conversion (Zero-IF) method is also used.
Japanese Patent Laid-Open No. 03-092029

However, in the case of the heterodyne method, in addition to unnecessary waves included in the RF signal, it is necessary to remove image unnecessary waves generated by the mixing process. In this case, a technique using an image reject mixer of the Hartley or Weaver type is known, but an unnecessary wave mixed in the RF signal band signal cannot be removed. On the other hand, the Zero-IF method can solve the above-mentioned image unnecessary wave problem, but it cannot remove the unnecessary wave mixed in the RF signal band signal as in the Hartley or Weaver type image reject mixer.

The unnecessary wave mixed in the RF signal band signal is separated into the upper band signal (USB) and the lower band signal (LSB) using the variable notch filter method or the two band pass filters described in Patent Document 1. However, a method of removing the signal power by comparing the signal power of USB and LSB is known.

However, the variable notch filter method has a complicated circuit scale in order to specify a band in which unnecessary waves are mixed in the frequency band, and requires a higher Q-value notch filter, which causes an increase in cost. Has drawbacks.

In addition, the method of Patent Document 1 that separates an RF signal into a USB component and an LSB component using a band pass filter only provides a high attenuation for an unwanted wave in the intermediate band of USB and LSB. First, the power of the signal having the highest signal power density in the intermediate band between the two bandpass filters is lost. Furthermore, a means for suppressing an image unnecessary wave generated in the mixer for baseband conversion from the IF signal is separately required, and the circuit becomes complicated. Therefore, for example, the technique of Patent Document 1 is not suitable as an unwanted wave countermeasure technique in the RF front end portion of a GALILEO-GPS hybrid receiver aimed at low cost and downsizing.

The present invention has been made in view of the above-described problems, and it is an object of the present invention to provide an inexpensive unnecessary wave removing receiver while simultaneously removing unnecessary waves and image unnecessary waves mixed in a wireless communication signal band. .

In order to solve the above-described problem, the present invention converts a wireless communication signal into a baseband quadrature (I component and Q component, the same applies hereinafter) signal, and converts each component signal of the quadrature signal to an upper band signal and a lower side signal. An image reject mixing unit that separates the signal into a band signal, and a control signal that selects any one of the upper band signal, the lower band signal, and the both side band signals of the baseband quadrature signal as a use band signal is generated. A selection control unit, and an output control unit that switches to the use band signal among the baseband orthogonal signals by the control signal, wherein the control signal is (S / N of the upper band signal)> (the S / N of both side band signal) and S / N condition of (S / N of lower band signal)> (Both side band signal). Features.

Further, in the present invention, the control signal includes a condition of (S / N of the upper band signal)> (S / N of the double band signal) and (S / N of the lower band signal)> (the Instead of the two conditions of the S / N condition of both side band signals), the condition of (the power of the upper band signal)> comparison coefficient × (the power of the lower side band signal) and (the lower band signal) The power may be generated based on two conditions: signal power)> comparison coefficient × (power of the upper sideband signal). By making the comparison coefficient larger than 1, it is not only the choice between LSB and USB as presented in the conventional technique, but also the three choices from LSB, USB and DSB. In the alternative case, it is possible to reduce the occurrence probability of 3 dB loss of S / N of the used band signal that always occurs.

Further, in the present invention, the control signal generated using the output of the image reject mixing unit is an I component signal or a Q component signal of the baseband quadrature signal, or an upper band signal and a lower band of both component signals. It is generated based on a signal.

Further, in the present invention, the upper band signal and the lower band signal of the I component signal and the Q component signal obtained from the image reject mixing unit are individually converted into IF band signals having the same center frequency. An up-conversion unit that generates an IF band upper band signal and an IF band lower band signal, which integrates the I component signal and the Q component signal, and the IF band signal obtained from the image reject mixing unit, A selection control unit that generates a control signal for selecting any one of the IF band upper band signal, the IF band lower band signal, and the IF band both side band signal as a use band signal, and a band signal to be used by the control signal. An output control unit for switching, and the control signal includes a condition of (S / N of the IF band upper band signal)> (S / N of the IF band both side band signal), and (I It is generated based on two conditions: S / N of F band lower side band signal> S / N condition of (IF band both side band signal).

Further, in the present invention, the control signal includes a condition of (S / N of the IF band upper band signal)> (S / N of the IF band both side band signal) and (S of the IF band lower band signal). / N)> (power of the IF band upper band signal)> comparison coefficient × (IF band lower sideband signal instead of the two conditions of the S / N condition of (the IF band both side band signal)) And (the power of the IF band lower side band signal)> the comparison coefficient × (the power of the IF band upper side band signal). Also good.

Further, in the present invention, the control signal generated using the up-conversion unit output is generated based on the IF band upper band signal and the IF band lower band signal.

Further, in the present invention, a condition of (the power of the IF band upper side band signal)> comparison coefficient × (power of the IF band lower side band signal) and (the power of the IF band lower side band signal)> the comparison In the case where the control signal is generated based on two conditions: a coefficient × (the power of the IF band upper band signal), the comparison coefficient is predetermined within a range greater than 1 and 10 or less. It is set as the value obtained.

Furthermore, in the present invention,
The wireless communication signal may be converted into a digital quantity, and the processing after the digital quantity conversion may be performed by digital circuit processing or software processing.

According to the present invention, since the wireless communication signal is directly converted into the baseband using the image reject mixer, the problem of unnecessary waves in the image band can be solved. In addition, the amount of attenuation of unwanted waves in the vicinity of both band signals (DSB) is usually a drawback inherent to the USB and LSB separation methods using a conventional band-pass filter because an image rejection ratio of 30 dB or more can be obtained. The problem of deterioration of the suppression characteristics of unwanted waves mixed in the intermediate band of USB and LSB can be solved.

In addition, the technique of the present invention is the S / N of S / N generated by selecting either USB or LSB in order to select a band signal that uses DSB instead of either conventional LSB or USB. The probability of occurrence of 3dB loss can be reduced.

(Embodiment 1)
FIG. 1 shows the configuration of Embodiment 1 of the present invention. This embodiment is composed of three blocks: an image / reject mixing unit 10, a use band control unit 20, and an output control unit 30. This configuration diagram shows an analog processing circuit configuration except for the A / D conversion processing of the output control unit 30.

In FIG. 1, the wireless communication signal is input to the mixer 3a of the image reject mixing unit 10, mixed with the output of the RF local frequency generator 1 that generates a local frequency substantially equal to the center frequency of the wireless communication signal, and the I component. Generate a signal. On the other hand, the wireless communication signal is also input to the mixer 3b, and the output of the RF local frequency generator 1 is mixed with the signal phase-shifted 90 degrees by the phase shifter 2 to generate a Q component.

The output of the mixer 3a is phase-shifted by 90 degrees by the phase shifter 4a, and then subtracted by the output of the mixer 3b and the adder 5a to generate Q _USB , which is the USB of the baseband Q component signal, Q _LSB that is the LSB of the baseband Q component signal is generated by addition by the subtractor 5b.

Further, the output of the mixer 3b is phase-shifted by 90 degrees by the phase shifter 4b, and then added by the output of the mixer 3a and the adder 6a to generate I _USB which is the USB of the baseband I component signal. and, to generate the I _LSB is the LSB of the I component baseband signal by subtracting in a subtractor 6b.

As described above, the baseband signal USB and LSB have an image relationship centered on DC by directly converting the wireless communication signal to the baseband using the image reject mixer. And output as separated into LSB.

It is a feature of the technique according to the present invention that USB and LSB have an image relationship centering on DC, which is important. This will be described with reference to (a) to (c) of FIG. FIG. 2A shows the DSB power spectrum of the baseband signal. In this figure, S _LSB , N _LSB and J _LSB are the LSB desired wave signal power, thermal noise power and unnecessary wave power, respectively. S _USB , N _USB and J _USB are the USB desired wave signal power and thermal noise, respectively. Electric power and unnecessary wave power.

2 (b) and 2 (c) show the LSB and USB power spectrums separated by the technique according to the present invention, respectively. As shown in the figure, USB and LSB are different from ideal and cannot be completely separated, but by making the image relationship centered on DC, interference from the other band can usually be expected to be 30 dB or more. It shows that the rejection ratio (IMMR) can be suppressed. It is difficult to obtain an interference suppression ratio having such a value with a conventional separation method using a band-pass filter.

In addition, since the image reject mixing unit 10 directly converts the wireless communication signal into baseband, that is, DC, the image unnecessary wave suppression problem that occurs when converting the IF signal into the IF signal can be solved.

The baseband Q _USB signal generated by the image reject mixing unit 10 is detected by the detector 21a, filtered by the low-pass filter 22a, and input to the selection control unit 23. On the other hand, the baseband Q _LSB signal is detected by the detector 21 b, filtered by the low-pass filter 22 b, and input to the selection control unit 23. Here, instead of the Q _USB signal and the Q _LSB signal, the I _USB signal and the I _LSB signal can be input to the detectors 21a and 21b.

Further, the input signal to the selection control unit 23 is selected from the baseband Q _USB and Q _LSB or the I _USB and I _LSB signals, or in combination, to select the band signal used by the baseband signal according to the present invention. It is possible to control.

Here, as a method of using the Q _USB and Q _LSB or the I _USB and I _LSB signals together, they may be combined at any place from the input to the output of the use band control unit 20. For example, Q _USB + I _USB can be used as the input of the detector 21a, and Q _LSB + I _LSB can be used as the input of the detector 21b. Further, Q _USB , I _USB , Q _LSB , and I _LSB can be separately detected, and a signal obtained by combining USB and LSB at the detection output stage can be input to the low-pass filters 22a and 22b. Also, the USB and LSB can be combined at the output stages of the low-pass filters 22a and 22b and used as the input of the selection control unit 23.

The baseband signals I _USB and I _LSB of the image reject mixing unit 10 are respectively connected to the switch 31a and the switch 31b of the output control unit 30, and the baseband signals Q _USB and Q _LSB are respectively a switch 32a and a switch 32b. Connected to.

These switches are controlled by the output of the selection control unit 23 so as to select either LSB, USB, or DSB. In other words, any of I _USB , I _LSB , and I _DSB is selected by turning ON / OFF the switch 31a and the switch 31b for the I _USB signal and the I _LSB signal. The I component signal passes through the low-pass filter 33a and the A / D converter 34a to generate an I _base signal. Similarly, the Q _USB signal and the Q _LSB signal are selected by the switch 32a and the switch 32b, and any of Q _USB , Q _LSB and Q _DSB is selected, passed through the low-pass filter 33b and the A / D converter 34b, and then the Q _base signal Is generated.

In FIG. 1, the output terminals of the switch 31a and the switch 31b and the output terminals of the switch 32a and the switch 32b are depicted as being connected. However, when using the _DSB I _DSB or Q _DSB , the USB and LSB are used. Are added and integrated.

Next, a technique for removing unnecessary waves mixed in the band signal will be described. In FIG. 2 (a), if the desired signal powers S _USB and S _LSB are represented by S and N _USB and N _LSB are also represented by N, the S / N of each band signal is represented by [ [Expression 1], [Expression 2], and [Expression 3]. [Equation 1], [Equation 2], and [Equation 3] are also established for the I component signal and the Q component signal.

The selection control unit 23 selects a band signal to be used for the baseband signal based on the condition of (S / N) _LSB > (S / N) _{DSB and} the condition of (S / N) _USB > (S / N) _DSB Generate and output a signal to control.

(S / N) _LSB > (S / N) The _DSB condition is equivalent to the condition of N _USB + J _USB > 3 (N _LSB + J _LSB ) from [ _Equation 1] and [Equation 3] (S / N) _USB > (S / N) The _DSB condition is equivalent to the condition of N _LSB + J _LSB > 3 (N _USB + J _USB ) from [ _Equation 2] and [Equation 3]. Also, since S _USB and S _LSB are usually negligible compared to N _USB + J _USB and N _LSB + J _LSB , USB power P _USB , ≒ N _USB + J _USB , LSB power P _LSB ≒ N _LSB If + J _LSB , the condition of (S / N) _LSB > (S / N) _DSB is P _USB > 3 x P _LSB condition, and the condition of (S / N) _USB > (S / N) _DSB is It can be approximated under the condition of P _LSB > 3 × P _USB .

Therefore, the selection control unit 23 selects LSB (Q _LSB and I _LSB ) when the condition of (S / N) _LSB > (S / N) _DSB or the condition of P _USB > 3 × P _LSB is satisfied, and , (S / N) _USB > (S / N) Select DS (Q _USB and I _USB ) if the conditions of _DSB or P _LSB > 3 × P _USB are met, and any of the above conditions is met If not, a control signal that selects DSB is generated and output.

If the desired wave power cannot be ignored, the condition of (S / N) _LSB > (S / N) _{DSB or} the condition of (S / N) _USB > (S / N) _DSB is P _USB > 3 × P It becomes Gataku to say that can be approximated to _{the LSB} of conditions and P _LSB> 3 × P _USB of conditions. However, in this case, the condition of P _USB > 3 × P _{LSB and} the condition of P _LSB > 3 × P _USB can be applied. In this case, the point to switch to DSB, USB, or LSB is only slightly shifted, and there is no practical problem.

In this case, if the switching point changes to an unacceptable level for practical use, the comparison coefficient 3 of the condition of P _LSB > 3 P _USB or the condition of P _USB > 3 P _LSB is increased from a value larger than 1. By adjusting within the following range, it is possible to suppress the switching point fluctuation that is practically acceptable.

FIG. 3 shows the use band signal of the baseband signal selected by the output of the selection control unit 23. The thick line in the figure is the band signal selected as the band to be used.

FIG. 3A is a state diagram when the unnecessary wave J _USB is included only in the USB. When the unwanted wave J _USB is small, the desired signal power of USB and LSB is 1/4 of DSB and thermal noise is 1/2, so (S / N) _USB and (S / N) _LSB are (S / N) 3dB worse than _DSB . As the unnecessary wave J _USB increases, (S / N) _LSB becomes constant, but both (S / N) _DSB and (S / N) _USB decrease. In the range where the unnecessary wave J _USB is (S / N) _LSB > (S / N) _DSB , the band signal used by the baseband signal is switched from DSB to LSB.

FIG. 3B is a state diagram when the unnecessary wave J _LSB is included only in the LSB. When unnecessary wave J _LSB is small, use _DSB with large (S / N) _DSB, and use baseband signal in the range where unnecessary wave J _LSB is (S / N) _USB > (S / N) _DSB Switch the band signal from DSB to USB.

As mentioned above, DSB signal is used when neither (S / N) _LSB > (S / N) _DSB condition or (S / N) _USB > (S / N) _DSB condition is satisfied. To do. The technique for selecting and controlling the band signal used by the baseband signal according to the present invention is not only the alternative from LSB and USB as presented in the conventional technique, but the three from LSB, USB and DSB. It is characterized by being selected.

As a result, in the case of the three alternatives, the DSB is one of the choices, so the probability of generating a 3 dB loss of regular S / N in the case of the two alternatives can be reduced. In particular, when applied to a GNSS (Global Navigation Satellite Systems) receiver, the S / N 3 dB loss greatly affects the performance.

(Embodiment 2)
The configuration diagram of FIG. 1 is a configuration in which a band signal to be used is selected as an output signal of the image reject circuit unit 10 to obtain an I and Q orthogonal signal. FIG. _{In this configuration, the USB} and I _LSB and the Q _USB and Q _LSB are up-converted using the same IF local frequency generator 47 that generates an intermediate frequency (IF).

This configuration is an advantageous configuration in which the phase needs to be controlled for tracking a wireless communication signal, such as a GPS positioning signal. The IF signal is easier to perform phase control and phase shifter processing than the baseband signal for the signal sent to the post-processing baseband processing unit.

In this configuration, in the up-conversion unit 40, the outputs of the mixers 43a and 43b are added to generate the IF band upper band signal RF _USB , the outputs of the mixers 45a and 45b are added, and the IF band lower band A signal RF _LSB is generated. The RF _USB and RF _LSB signals are input to the output control unit 30, a band signal to be used is selected, A / D converted, and sent as an RFbase signal to a post-processing baseband processing unit (not shown). In the figure, the outputs of the switches 31a and 31b are combined. However, when both the RF _USB and RF _LSB signals are selected, the sum of the outputs of 31a and 31b is used.

Further, the RF _USB and RF _LSB signals are also input to the use band control unit 20, and a control signal for selecting a band signal to be used is generated and sent to the output control unit 30, as described in the first embodiment. .

(Embodiment 3)
In the configuration diagram of FIG. 1, the processing of the image reject circuit unit 10, the used band control unit 20, and the output control unit 30 can be processed by a digital circuit or software. In this case, the method of the present invention can be implemented by converting a wireless communication signal into a digital signal by an A / D converter and performing digital processing or software processing of each functional unit shown in FIG.

Similarly, in the embodiment of FIG. 4, the wireless communication signal is converted into a digital signal by an A / D converter, and the digital processing or software processing of each functional unit shown in FIG. 4 is performed. Can be implemented.

Explanatory drawing of Embodiment 1 of the unnecessary wave suppression circuit structure based on this invention Explanatory diagram of the power spectrum of the baseband signal according to the present invention Explanatory drawing of the band signal used of the baseband signal used according to the present invention Explanatory drawing of Embodiment 2 of the unnecessary wave suppression circuit structure based on this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 RF local frequency generator 2 90 degree phase shifter 3a, 3b Mixer 4a, 4b 90 degree phase shifter 5a, 6a Adder 5a, 6b Subtractor 10 Image rejection mixing part 20 Use band control part 21a, 21b Detection 22a, 22b Low pass filter 23 Selection control unit 30 Output control unit 31a, 31b I component selection switch 32a, 32b Q component selection switch 33a, 33b Low pass filter 34a, 34b A / D converter 40 Up-conversion unit 41a, 41b Low-pass filter 42a, 42b Low-pass filter 43a, 43b Mixer 44a, 44b 90 ° phase shifter 45a, 45b Mixer 46a, 46b Adder 47 IF local frequency generator

Claims (8)

An image reject mixing unit that converts a wireless communication signal into a baseband orthogonal signal and separates each component signal of the orthogonal signal into an upper band signal and a lower band signal;
A selection control unit that generates a control signal for selecting any one of the upper band signal, the lower band signal, and both side band signals as a use band signal among the baseband orthogonal signals;
An output control unit that switches to the use band signal among the baseband orthogonal signals by the control signal;
The control signal includes a condition of (S / N of the upper band signal)> (S / N of the double band signal) and S of (the S / N of the lower band signal)> (the double band signal). An unnecessary wave elimination receiver generated based on two conditions of / N. An image reject mixing unit that converts a wireless communication signal into a baseband orthogonal signal and separates each component signal of the orthogonal signal into an upper band signal and a lower band signal;
A selection control unit that generates a control signal for selecting any one of the upper band signal, the lower band signal, and both side band signals as a use band signal among the baseband orthogonal signals;
An output control unit that switches to the use band signal among the baseband orthogonal signals by the control signal;
The control signal has the following condition: (power of the upper band signal)> comparison coefficient × (power of the lower sideband signal) and (power of the lower sideband signal)> comparison coefficient × (the upper sideband band) A receiver for eliminating unnecessary waves, which is generated based on two conditions of a signal power). In the unnecessary wave removal receiver in any one of Claims 1-2,
The unnecessary wave elimination receiver, wherein the control signal is generated based on the upper band signal and the lower band signal of at least one component of the baseband quadrature signal. An image reject mixing unit that converts a wireless communication signal into a baseband orthogonal signal and separates each component signal of the orthogonal signal into an upper band signal and a lower band signal;
The upper band signal and the lower band signal of the baseband quadrature signal are individually converted to an IF band signal having the same center frequency, and an IF band upper band signal and an IF band lower band signal are generated.・ Conversion part,
A selection control unit for generating a control signal for selecting any one of the IF band upper band signal, the IF band lower band signal, and the IF band both side band signal as a use band signal among the IF band signals;
An output control unit that switches to the use band signal of the IF band signal by the control signal;
The control signal has the following condition: (S / N of the IF band upper band signal)> (S / N of the IF band double band signal) and (S / N of the IF band lower band signal)> (the An unnecessary wave elimination receiver, which is generated based on two conditions of S / N condition of IF band both-side band signal). An image reject mixing unit that converts a wireless communication signal into a baseband orthogonal signal and separates each component signal of the orthogonal signal into an upper band signal and a lower band signal;
The upper band signal and the lower band signal of the baseband quadrature signal are individually converted to an IF band signal having the same center frequency, and an IF band upper band signal and an IF band lower band signal are generated.・ Conversion part,
A selection control unit for generating a control signal for selecting any one of the IF band upper band signal, the IF band lower band signal, and the IF band both side band signal as a use band signal among the IF band signals;
An output control unit that switches to the use band signal of the IF band signal by the control signal;
The control signal has the following condition: (power of the IF band upper side band signal)> comparison coefficient × (power of the IF band lower side band signal) and (power of the IF band lower side band signal)> the comparison coefficient An unnecessary wave elimination receiver generated based on two conditions of x (the power of the IF band upper band signal). In the unnecessary wave elimination receiver of Claim 4 and Claim 5,
The unnecessary wave cancellation receiver, wherein the control signal is generated based on an IF band upper band signal and an IF band lower band signal. In the unnecessary wave elimination receiver according to claim 2 and claim 5,
The comparison coefficient is a value determined in advance within a range greater than 1 and 10 or less. In the unnecessary wave removal receiver in any one of Claims 1-7,
An unnecessary wave elimination receiver, wherein the wireless communication signal is converted into a digital quantity, and the processing after the digital quantity conversion is processed by digital circuit processing or software processing.

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