JPH1198091A - Radio communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communication device which prevents a communication quality from being lowered due to noise and prevents a communication quality from being lowered because a circuit is saturated by noise. SOLUTION: A signal band of the radio communication device is set to a band which is not overlapped on a band of noise which is emitted from a noise generation source such as an electronic oven. When the amplitude of noise that passes through a high frequency band pass filter 11 is smaller than threshold Vth, a gain controlling means 18 does not operate. In such cases, noise is eliminated by a base band low pass filter 16. On the other hand, when the amplitude of noise that passes through the filter 11 is larger than the threshold Vth, the means 18 lowers the gain of a high frequency band pass filter 12. This prevents a high frequency amplifier 12 and a frequency mixer 13 from being saturated with noise and prevents a signal from being distorted by saturation and a communication quality from being lowered. Also, the means 18 increases the gain of the base band amplifier 16 to compensate gain that is suppressed by high frequency amplification 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication apparatus, and more particularly to a radio communication apparatus using a spread spectrum communication system.

[0002]

2. Description of the Related Art Conventionally, a radio communication device as shown in FIG. 7 has been known as a radio communication device using a spread spectrum communication system. The radio communication device shown in FIG. 7 includes an antenna 100 for receiving a high-frequency signal, a high-frequency bandpass filter 101 for limiting the band of the received high-frequency signal, and a high-frequency amplifier 10 for adjusting the amplitude of the band-limited high-frequency signal.
2. A frequency mixer 103 for down-converting a high-frequency signal whose amplitude has been adjusted, a local oscillator 104 for generating a local oscillation signal having a frequency f0, and a baseband low-pass filter for limiting the band of the down-converted signal. 10
5. A baseband amplifier 106 for adjusting the amplitude of the band-limited signal, and a demodulator 10 for performing despreading and data demodulation.
7 and the like. This wireless communication device operates as follows. The high-frequency signal spectrum-spread with the spread code is received by the antenna 100, band-limited by the high-frequency band-pass filter 101, and then amplified by the high-frequency amplifier 102. The amplified high frequency signal is mixed with a local oscillation signal from a local oscillator 104 by a frequency mixer 103 and downconverted to a baseband signal. The downconverted signal is a baseband low
After the unnecessary signal is removed by band limitation by the pass filter 105, the signal is amplified by the base band amplifier 106. Demodulator 107 performs despreading and data demodulation, and outputs demodulated data.

[0003]

In a radio communication apparatus using such a spread spectrum communication system, 2.484 ± 0.0 in the ISM band (2.4 to 2.5 [GHZ]).
13 [GHZ] is used as a signal band. That is, as shown in FIG. 8, the radio center frequency f0 is set to 2.48.
4 [GHZ], baseband signal bandwidth Bw1 is 26
[MHZ]. However, there is noise radiated from the microwave in this ISM band. For this reason, when the microwave oven operates near the wireless communication device using the spread spectrum communication method, noise radiated from the microwave exists in the signal band of the wireless communication device as shown in FIG. There is a problem that it decreases. Also, even if the base band low-pass filter 105
, The high-frequency amplifier 102 and the frequency mixer 103 at the preceding stage may be saturated by high-power noise radiated from the microwave oven. When the high-frequency amplifier 102 and the frequency mixer 103 are saturated, the signal is distorted, and the communication quality is reduced. As a countermeasure, it is conceivable to use a high-frequency amplifier 102 or a frequency mixer 103 having a high capacity, but this leads to an increase in the size and cost of the apparatus, which is not desirable. On the other hand, the frequency component of the noise radiated from the microwave oven varies with time, and a period in which the noise exists in the signal band and a period in which the noise does not exist alternately occur. Therefore, a method has been developed which utilizes the periodicity of the noise and performs communication during a period in which the noise does not exist in the signal band to avoid the influence of the noise. However, according to this method, for example, in the case of packet communication, the packet length cannot be made longer than the period in which noise does not exist in the signal band, and the amount of one data transmission decreases, and the communication time increases. There is a problem.
The present invention has been made in order to solve such problems of the related art, and a wireless communication device that does not have a risk of deteriorating communication quality even when used near a noise source such as a microwave oven. The task is to provide.

[0004]

According to an aspect of the present invention, there is provided a high-frequency filter for limiting a band of a received high-frequency signal, and adjusting an amplitude of the band-limited high-frequency signal. A first gain unit, a frequency mixer for down-converting the high-frequency signal whose amplitude has been adjusted,
In a wireless communication apparatus including a filter for limiting the band of a downconverted signal and a second gain device for adjusting the amplitude of the band-limited signal, the band of the high-frequency signal does not overlap with the band of noise. Set to the band, the first
The gain of the gain device is configured to be variable. According to a second aspect of the present invention, in the wireless communication apparatus according to the first aspect, the first gain device includes a plurality of high-frequency amplifiers and a changeover switch. With the wireless communication device according to the first and second aspects, it is possible to prevent communication quality from being degraded by noise radiated from a noise source such as a microwave oven. In addition, since the gain of the first gain unit that adjusts the amplitude of the high-frequency signal is configured to be variable, it is possible to prevent the circuit from being saturated in the preceding stage of the filter that limits the signal band even when the noise power is large. Thus, it is possible to prevent a decrease in communication quality due to saturation of the circuit. According to a third aspect of the present invention, in the wireless communication apparatus according to the first or second aspect, the gain control means for lowering the gain of the first gain unit according to the amplitude of the band-limited high-frequency signal is provided. Provide. According to the third aspect of the present invention, the gain of the first gain unit is automatically reduced according to the level of noise passing through the high-frequency filter by the gain control means. This eliminates the need to adjust the work. According to a fourth aspect of the present invention, in the wireless communication apparatus according to any one of the first to third aspects, the gain of the second gain unit is configured to be variable.
According to the wireless communication device of the fourth aspect, the gain reduced by the first gain device can be compensated by the second gain device, so that demodulated data having a normal amplitude can be obtained. According to a fifth aspect of the present invention, in the wireless communication apparatus according to the fourth aspect, a limiter amplifier is used as the second gain device. The invention according to claim 6 is the same as the invention according to claim 4.
In the wireless communication device according to the, the gain control means,
The gain of the first gain unit is reduced and the gain of the second gain unit is increased according to the amplitude of the band-limited high-frequency signal. The use of the wireless communication device according to claims 5 and 6 eliminates the need to adjust the gain of the second gain device.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. First, the signal band of the wireless communication device using the spread spectrum communication system of the present invention is set to a band that does not overlap with the band of noise radiated from a noise source such as a microwave oven in the ISM band as shown in FIG. Set. Here, the band that does not overlap with the noise band is preferably a band that does not completely overlap with the noise band, but may be a band that has relatively little noise. In this case, the signal bandwidth Bw2 of the wireless communication device of the present invention is narrower than the signal bandwidth Bw1 of the conventional wireless communication device, so that the amount of signal transmission decreases, but priority is given to improvement of communication quality.

FIG. 2 shows a first embodiment of the wireless communication apparatus according to the present invention. In the first embodiment, an antenna 10 for receiving a high-frequency signal, a high-frequency bandpass filter 11, a variable-gain high-frequency amplifier 12, a frequency mixer 13, and a frequency f
A local oscillator 14 for generating a local oscillation signal of 0, a baseband low-pass filter 15, a variable gain baseband amplifier 16, a demodulator 17, a variable gain high-frequency amplifier 12, and an amplification factor of the variable gain baseband amplifier 16 are adjusted. And a gain control means 18 for controlling the gain. The gain control means 18 includes a detector 19 for detecting the amplitude of the high-frequency signal band-limited by the high-frequency band-pass filter 11,
Comparator 2 for comparing the amplitude detected at 9 with the threshold value Vth
0, a low-pass filter 21, and an inverting amplifier 22. The high-frequency filter for limiting the band of the high-frequency signal according to the present invention corresponds to a high-frequency band-pass filter, and the first gain device for adjusting the amplitude of the band-limited high-frequency signal corresponds to the variable gain high-frequency amplifier 12. The frequency mixer for down-converting the high-frequency signal whose frequency has been adjusted corresponds to the frequency mixer 13, and the filter for limiting the band of the down-converted signal corresponds to the base band low-pass filter 15. The second gain device for adjusting the amplitude of the received signal is a variable gain baseband amplifier 1.
6, and a gain control means for adjusting the gains of the first and second gain devices in accordance with the amplitude of the band-limited high-frequency signal corresponds to the gain control means 18.

[0007] The wireless communication device of the first embodiment operates as follows. The high-frequency signal received by the antenna 10 is band-limited by the high-frequency band-pass filter 11, and unnecessary signals outside the desired band are removed. However, unnecessary signals near the desired band cannot be completely removed due to the characteristics of the high-frequency band-pass filter and the like. The band-limited high-frequency signal is amplified by a variable gain high-frequency amplifier 12 and then mixed with a local oscillation signal of a frequency f0 from a local oscillator 14 by a frequency mixer 13 to be down-converted into a base band signal. . The downconverted signal is
The signal band (Bw2 /
After the band is limited to 2), the signal is amplified by the variable gain base band amplifier 16. The demodulator 17 performs despreading and data demodulation and outputs demodulated data.

When such a wireless communication apparatus is used near a microwave oven as a noise source, noise of frequency components near a desired band among noises emitted from the microwave oven passes through a high-frequency bandpass filter 11 together with a signal. I do.
When the amplitude of the noise passing through the high-frequency band-pass filter 11 is small, the gain control unit 18 does not operate. In this case, the variable gain high frequency amplifier 12 and the frequency mixer 1
3 is not saturated, the signal is
There is no distortion in the frequency mixer 13. After being down-converted by the frequency mixer 13, it is supplied to the base band low-pass filter 15, and the noise is removed by the base band low-pass filter 15. As a result, the communication quality does not decrease. On the other hand, if the amplitude of the noise passing through the high-frequency bandpass filter 11 is large,
Since the variable gain high-frequency amplifier 12 and the frequency mixer 13 are saturated, the signal is distorted by the variable gain high-frequency amplifier 12 and the frequency mixer 13 and communication quality is degraded. To prevent this, the comparator 20 outputs a signal when the amplitude of the high-frequency signal detected by the detector 19 exceeds the threshold value Vth. The output signal of the comparator 20 has a predetermined time constant.
The signal is supplied to the variable gain high frequency amplifier 12 via the pass filter 21 and to the variable gain base band amplifier 16 via the inverting amplifier 22. Thereby, the gain of the variable gain high frequency amplifier 12 is suppressed, and the variable gain high frequency amplifier 12 and the frequency mixer 13 are prevented from being saturated by noise. The variable gain baseband amplifier 16 increases the gain so as to compensate for the gain suppressed by the variable gain high frequency amplifier 12. With this configuration, the communication quality does not decrease due to noise, and the communication quality does not decrease even in the presence of strong noise. The gain control means 18 may be configured to continuously adjust the gains of the variable gain high frequency amplifier 12 and the variable gain base band amplifier according to the amplitude of the high frequency signal.

Next, FIG. 3 shows a second embodiment. In the second embodiment, an antenna 30, a high-frequency band-pass filter 31, a variable gain high-frequency amplifier 32, a frequency mixer 33, a local oscillator 34, a base band low-pass filter 35, a limiter amplifier 36, a demodulator 37, a gain control means 38. The gain control means 38 includes a detector 39, a comparator 40 for comparing the detected amplitude with a threshold value Vth, and a low-pass filter 41.
In the second embodiment, the variable gain base of the first embodiment is used.
Gain control means 1 for adjusting the gains of the variable gain high frequency amplifier 12 and the variable gain base band amplifier 16 while using a limiter amplifier 36 instead of the band amplifier 16;
The difference from the first embodiment is that a gain control means 38 for adjusting the gain of the variable gain high frequency amplifier 32 is used instead of the gain control unit 8. The limiter amplifier 36 outputs a signal having a constant amplitude regardless of the amplitude of the input signal. For this reason, even if the gain of the variable gain high frequency amplifier 32 decreases, the limiter amplifier 36 operates to compensate for the gain suppressed by the variable gain high frequency amplifier 32, so that it is not necessary to adjust the gain by the gain control means. The operation of the second embodiment is the same as the operation of the first embodiment, and will not be described. The gain control means of the present invention for adjusting the gain of the first gain device according to the amplitude of the band-limited high-frequency signal corresponds to the gain control means 38.

Next, FIG. 4 shows a third embodiment. In the third embodiment, an antenna 50, a high-frequency bandpass filter 51, high-frequency amplifiers 52 and 54, a changeover switch 5
3, 55, a frequency mixer 56, a local oscillator 57, a baseband low-pass filter 58, a limiter amplifier 59, a demodulator 60, and a gain control means 61. The gain control means 38 includes a detector 62 and a comparator 63 for comparing the detected amplitude with a threshold value Vth, and outputs a control signal to the changeover switches 53 and 55. The third embodiment is different from the variable gain high-frequency amplifier 32 of the second embodiment.
Are constituted by a plurality of high-frequency amplifiers 52 and 54 and changeover switches 53 and 55 for switching the number of stages of the high-frequency amplifiers. That is, the high-frequency bandpass filter 5
When the amplitude of the noise passing through 1 is smaller than the threshold value Vth, the switches 53 and 55 are switched by the output of the comparator 61 to form a high-frequency amplifier by the high-frequency amplifiers 52 and 54 connected in series, When the noise is larger than the threshold value Vth, the switches 53 and 55 are switched by the output of the comparator 61 to the high-frequency amplifier 54.
Is switched off so that only the high-frequency amplifier 52 constitutes the high-frequency amplifier. The number of high-frequency amplifiers and the number of switching stages can be changed as appropriate. Also,
Instead of the limiter amplifier 59, a variable gain baseband amplifier controlled by gain control means can be used. In this case, it may be constituted by a plurality of baseband amplifiers and changeover switches.

Next, a fourth embodiment is shown in FIG. In the fourth embodiment, an antenna 70, a high-frequency bandpass filter 71, high-frequency amplifiers 72 and 74, a changeover switch 7
3, 75, a frequency mixer 76, a local oscillator 77, a baseband low-pass filter 78, a limiter amplifier 79, and a demodulator 80. In the fourth embodiment,
If the use environment of the wireless communication apparatus is known, the gain of the high-frequency amplifier may be set in advance, so that the variable gain control means 61 of the third embodiment is omitted and can be switched manually. Changeover switches 73 and 75 are provided. That is, when the surrounding noise is small and there is no possibility that the high frequency amplifier or the frequency mixer is saturated, the changeover switches 73 and 75 are switched so that the high frequency amplifier is constituted by the high frequency amplifiers 72 and 74 connected in series,
If the surrounding noise is large and the high frequency amplifier or the frequency mixer is likely to be saturated, the high frequency amplifier 74 is separated and the changeover switches 73 and 75 are switched so that the high frequency amplifier is constituted only by the high frequency amplifier 72. The number of high-frequency amplifiers and the number of switching stages can be changed as appropriate. Instead of the limiter amplifier 79, a variable gain baseband amplifier controlled by gain control means can be used. In this case, it may be constituted by a plurality of baseband amplifiers and changeover switches.

FIG. 6 is a diagram showing a changeover switch for changing the number of stages of the high-frequency amplifier by changing the mounting direction of the capacitor. As shown in FIG. 6a, when the capacitor 94 is mounted between the conductive paths 91 and 92, the conductive path 9
1 and 92 are connected, for example, a high-frequency amplifier is composed of two stages. On the other hand, as shown in FIG. 6B, when the capacitor 94 is mounted between the conductive paths 91 and 93, the conductive paths 91 and 93 are connected, and for example, only one high-frequency amplifier is constituted.

In the above embodiment, a variable gain high frequency amplifier is used, but a high frequency amplifier and a variable gain attenuator may be used. Although the direct conversion wireless communication apparatus has been described, the present invention can be applied to a super heterodyne wireless communication apparatus. Further, the high-frequency filter, the first gain device, the second gain device, and the filter for limiting the signal band can have various configurations. Further, the second gain device for adjusting the amplitude of the band-limited signal is provided, but the second gain device may be omitted if it is not necessary to adjust the amplitude of the band-limited signal.

[0014]

As described above, the use of the wireless communication apparatus according to the first and second aspects can prevent the communication quality from being degraded due to noise, and can reduce the communication quality due to the saturation of the circuit due to noise. Can be prevented from decreasing. Further, if the wireless communication device according to the third aspect is used, the operation of adjusting the gain of the first gain device becomes unnecessary. Further, if the wireless communication device according to claim 4 is used,
Demodulated data of normal amplitude can be obtained. In addition, the use of the wireless communication device according to claims 5 and 6 eliminates the need to adjust the gain of the second gain device.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a signal band of a wireless communication device according to the present invention.

FIG. 2 is a diagram showing a first embodiment of the present invention.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a third embodiment of the present invention.

FIG. 5 is a diagram showing a fourth embodiment of the present invention.

FIG. 6 is a diagram illustrating an example of a changeover switch.

FIG. 7 is a diagram showing a conventional wireless communication device.

FIG. 8 is a diagram illustrating a signal band of a conventional wireless communication device.

[Explanation of symbols]

11, 31, 51, 71, 101 High-frequency band-pass filter 12, 32 Variable gain high-frequency amplifier 13, 33, 56, 76, 103 Frequency mixer 15, 35, 58, 78, 105 Base band low-pass filter 16 Variable gain filter -Band amplifiers 18, 38, 61 gain control means 36, 59, 79 limiter amplifiers 52, 54, 72, 74, 102 high frequency amplifiers 53, 55, 73, 75

Claims (6)

[Claims] 1. A high-frequency filter for limiting the band of a received high-frequency signal, a first gain unit for adjusting the amplitude of the band-limited high-frequency signal, and a frequency for down-converting the high-frequency signal whose amplitude has been adjusted. Mixer and down converter
And a second gain unit for adjusting the amplitude of the band-limited signal, wherein the band of the high-frequency signal is set to a band that does not overlap the band of the noise. A wireless communication device, wherein the gain of the first gain device is configured to be variable. 2. The wireless communication device according to claim 1, wherein the first gain device includes a plurality of high-frequency amplifiers and a changeover switch. 3. The wireless communication apparatus according to claim 1, further comprising gain control means for lowering the gain of the first gain device according to the amplitude of the band-limited high-frequency signal. 4. The wireless communication device according to claim 1, wherein a gain of said second gain device is configured to be variable. 5. The wireless communication device according to claim 4, wherein a limiter amplifier is used as said second gain device. 6. The gain control unit according to claim 1, wherein the gain of the first gain unit is decreased and the gain of the second gain unit is increased according to the amplitude of the band-limited high-frequency signal. 5. The wireless communication device according to 4.