JP2002185349A - High frequency signal receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and inexpensive high frequency signal receiver. SOLUTION: This high frequency signal receiver is provided with an input terminal 31 to which a high frequency signal is inputted, a mixer 35 to whose one input a signal inputted to the input terminal 31 is supplied and to whose other input the output of a local oscillator 34 is supplied, a fixed filter 36 for allowing intermediate frequency to be outputted from the mixer 35 to pass, an output terminal 46 to which the output of the fixed filter 36 is supplied, a phase comparator 52 to whose one input the output of the local oscillator 34 is supplied and whose other input comparison frequency is inputted, and a low pass filter 55 connected between the output of the phase comparator 52 and the input of the local oscillator 34. In this case, the integral multiple of the comparison frequency is set as the large comparison frequency so as not to be made equal to the channel interval frequency of the high frequency signal. Thus, it is possible to obtain the compact and inexpensive high frequency signal receiver.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency signal receiving apparatus for receiving a high-frequency digital signal.

[0002]

2. Description of the Related Art A conventional high frequency signal receiving apparatus will be described below. As shown in FIG. 10, a conventional high-frequency signal receiving apparatus has an input terminal 1 to which a high-frequency digital signal is input.
And a high-pass filter 2 supplied with a signal input to the input terminal 1 and passing a frequency of 1450 MHz or more, and a band-pass filter connected to an output of the high-pass filter 2 and passing a frequency of 1450 MHz to 1492 MHz. A mixer 5 having an output of the bandpass filter 3 connected to one input and an output of a local oscillator 4 connected to the other input;
A tracking filter 6 to which the output of the mixer 5 is connected; an electronic changeover switch 7 to which the output of the tracking filter 6 is connected to one terminal 7a; A low-pass filter 8 for passing a frequency, a tracking filter 9 connected between the output of the low-pass filter 8 and the other terminal 7b of the changeover switch 7, and a common terminal 7c of the changeover switch 7 are connected to one input. A mixer 11 connected to the other input and connected to the output of the local oscillator 10, a band-pass filter 12 connected to the output of the mixer 11 and passing a frequency of about 38.9 MHz, Bandpass filter 1
A mixer 14 whose output is connected to one input and whose other input is connected to the output of a local oscillator 13;
The output of the mixer 14 is connected and approximately 2.0 M
The bandpass filter 15 passes a frequency of 1 Hz, and an output terminal 16 to which the output of the bandpass filter 15 is connected.

The local oscillator 4 is connected to the PLL circuit 17 in a loop and oscillates at a frequency of 1271 MHz (fixed). The local oscillator 10 is also connected to the PLL circuit 18 in a loop. By changing the data of the PLL circuit 18, the oscillation frequency output from the local oscillator 10 is changed so that the frequency output from the mixer 11 becomes approximately 38.9 MHz. That is, tuning is performed by making the oscillation frequency of the local oscillator 10 variable. Further, the tracking filters 6 and 9 control the passing frequency by the voltage output from the PLL circuit 18.

[0004] The operation of the high-frequency signal receiving apparatus configured as described above will be described below. FIG. 10, FIG.
1, the input terminal 1 has 174M as shown at 20.
A high frequency digital signal of a V band 26 from Hz to 245 MHz and an L band 21 of 1450 MHz to 1492 MHz are input.

It is assumed that the changeover switch 7 has been switched to the side 7a in order to select the L band 21. Then, the signal of the L band 21 from 1450 MHz to 1492 MHz is mixed with the signal of the local oscillator 4 oscillating the frequency of 1271 MHz by the mixer 5 and the signal of the V band 23 from 179 MHz to 221 MHz as shown in FIG. Shift to obi. The V band 23 is selected by the local oscillator 10 which is a variable frequency oscillator, and is converted into an intermediate frequency 24a of 38.9 MHz shown in 24. This intermediate frequency 24a is converted by the local oscillator 13 as a fixed frequency oscillator into an intermediate frequency 25a of 2.0 MHz indicated by 25 and output from the output terminal 16.

Next, the changeover switch 7 is set to the V band 26
It has been switched to 7b in order to select. Then, the V band 26 input from 174 MHz to 245 MHz is selected by the tracking filter 9 and the mixer 11, and
1 is converted to an intermediate frequency 24a of 38.9 MHz shown at 24. This intermediate frequency 24a is converted by the local oscillator 13 as a fixed frequency oscillator into an intermediate frequency 25a of 2.0 MHz indicated by 25 and output from the output terminal 16.

As described above, this high-frequency signal receiving apparatus can receive two bands of the V band 26 and the L band 21 by switching the changeover switch 7 with one apparatus.

[0008]

However, in such a conventional high-frequency signal receiving apparatus, the tracking filter 6 is required for receiving the L band 21 despite the fact that the mixer 5 is provided. The tracking filter 6 has a larger shape and a higher price than the fixed filter.

An object of the present invention is to solve such a problem and to provide a small and low-cost high-frequency signal receiving apparatus.

[0010]

In order to achieve this object, a high-frequency signal receiving apparatus according to the present invention uses a fixed filter as a filter for passing an intermediate frequency and an integer multiple of a comparison frequency to set a channel spacing frequency of the high-frequency signal. The comparison frequency is set so as not to be equal to.

As a result, a small and inexpensive high-frequency signal receiving device can be obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, an input terminal to which a high-frequency signal is input, a signal input to this input terminal is supplied to one input, and is input to the other input. Is a mixer to which the output of a local oscillator whose oscillation frequency is variable, a filter that passes an intermediate frequency output from the mixer, an output terminal to which the output of this filter is supplied, An output is supplied to one input, and the other input is provided with a phase comparator to which a comparison frequency is input, and a low-pass filter connected between an output of the phase comparator and an input of the local oscillator. The filter that passes the intermediate frequency is a fixed filter, and the comparison frequency is large enough that an integral multiple of the comparison frequency is not equal to the channel spacing frequency of the high-frequency signal. It is a high-frequency signal receiving device set to a number, and the high-frequency signal is mixed with the output of the local oscillator whose oscillation frequency can be varied by the mixer. A fixed filter can be used as the filter. Therefore, the size and the price are lower than those of the tracking filter.

Further, since the comparison frequency is set to be so large that the integral multiple of the comparison frequency is not equal to the channel interval frequency of the high-frequency signal, phase noise is reduced, and errors are reduced in demodulation of digital signals.

According to a second aspect of the present invention, when the channel spacing frequency is approximately 1.712 MHz, the comparison frequency is 64 KHz, and the comparison frequency is as large as 64 KHz. , Phase noise is reduced, and errors are reduced in demodulation of digital signals. Further, since the channel spacing frequency is approximately 1.712 MHz, sufficient frequency accuracy that can be practically used can be obtained.

According to a third aspect of the present invention, a variable frequency divider is provided between the local oscillator and the input of the phase comparator, and the 1 / n and n +
A frequency divider that can be switched to 1/1 is provided, and the frequency division ratio of the variable frequency divider is controlled;
3. An error minimizing means which is controlled so that a difference between an intermediate frequency output from the mixer and a predetermined frequency is minimized by performing switching control of the frequency divider. And the error minimizing means is provided, so that sufficient frequency accuracy can be obtained.

According to a fourth aspect of the present invention, there is provided the high frequency signal receiving apparatus according to the third aspect, wherein the error minimizing means is constituted by software, and hardware for the error minimizing means is not required. The size and the price can be reduced.

According to a fifth aspect of the present invention, there is provided the high-frequency signal receiving apparatus according to the third aspect, wherein the value of n is 30. If the channel spacing frequency is approximately 1.712 MHz and the comparison frequency is 64 KHz, Maximum frequency error width is 1.37
Since the frequency is about 6 MHz, practically sufficient frequency accuracy can be obtained, and the design of the fixed filter becomes easy.

According to a sixth aspect of the present invention, the output of the fixed filter that passes the intermediate frequency is connected to one terminal of the changeover switch, and the other end of the changeover switch is connected to the input terminal. A tracking filter, a second mixer having a common terminal of the changeover switch connected to one terminal and an output of a second local oscillator in which a PLL circuit is loop-connected to the other terminal, 2. The high-frequency signal receiving apparatus according to claim 1, further comprising a second intermediate frequency filter to which an output of the second mixer is supplied, and an output terminal to which an output of the second intermediate frequency filter is supplied. By switching the changeover switch, two frequency bands can be received.

According to a seventh aspect of the present invention, the output of the second intermediate frequency filter is connected to one terminal and the output of a third local oscillator is connected to the other terminal.
And a third mixer to which the output of the third mixer is supplied.
7. The high-frequency signal receiving apparatus according to claim 6, further comprising: an intermediate frequency filter of the formula (1), and an output terminal to which the output of the third intermediate frequency filter is connected. Since it is a double super receiver with
Even in the V band, even if there is a jamming radio wave near a desired reception signal, it can be efficiently removed.

According to an eighth aspect of the present invention, there is provided a fourth filter for attenuating a frequency having a symmetrical relationship with a second intermediate frequency of a desired signal with respect to a local oscillation frequency output from a third local oscillator. 8. The high-frequency signal receiving apparatus according to claim 7, wherein the high-frequency signal receiving apparatus is connected in series with the second intermediate frequency filter, and a second intermediate signal of a desired signal with respect to a local oscillation frequency output from a third local oscillator by a fourth filter. Since the frequency having a symmetrical relationship with the frequency is attenuated, even if there is a high-power interference wave near the desired signal, this interference wave is attenuated by the fourth filter, so that it is not output from the output terminal. . Therefore, in conclusion, the occurrence of errors is reduced.

According to a ninth aspect of the present invention, when the surface acoustic wave filter is used as the second intermediate frequency filter and the second intermediate frequency of the desired signal is higher than the frequency output from the third local oscillator, 9. The high-frequency signal receiving device according to claim 8, wherein the fourth filter is a high-pass filter including an inductance and a capacitance, and the second intermediate frequency filter uses a surface acoustic wave filter, so that a high amount of attenuation is provided. Can be obtained.

Further, since the second intermediate frequency of the desired signal is higher than the frequency output from the third local oscillator, the interference frequency becomes lower than the frequency output from the third local oscillator, so that May use a high-pass filter. Further, since this high-pass filter is composed of inductance and capacitance, a low-cost high-pass filter can be realized.

According to a tenth aspect of the present invention, when the surface acoustic wave filter is used as the second intermediate frequency filter and the second intermediate frequency of the desired signal is lower than the frequency output from the third local oscillator, 9. The high-frequency signal receiving apparatus according to claim 8, wherein the fourth filter is a low-pass filter including an inductance and a capacitance, and the second intermediate frequency filter uses a surface acoustic wave filter, so that a high attenuation is provided. Can be obtained.

Also, since the second intermediate frequency of the desired signal is lower than the frequency output from the third local oscillator, the interference frequency becomes higher than the frequency output from the third local oscillator, and is applied to the fourth filter. May use a low-pass filter. Further, since this low-pass filter is composed of an inductance and a capacitance, a low-cost low-pass filter can be realized.

An eleventh aspect of the present invention is the high-frequency signal receiving apparatus according to the eighth aspect, wherein an amplifier is inserted between the second intermediate frequency filter and the fourth filter. In addition, the isolation between the intermediate frequency filter and the fourth filter can be improved and impedance matching can be achieved, and the characteristics of each filter can be utilized.

According to a twelfth aspect of the present invention, a surface acoustic wave filter is used as the second intermediate frequency filter, and an output of the second intermediate frequency filter is input to a fourth filter including an inductance and a capacitance. The output of the second mixer is input first to the surface acoustic wave filter having a steep attenuation characteristic and a large amount of attenuation. Suitable for use in particularly strong areas.

According to a fourth aspect of the present invention, the fourth filter is constituted by an inductance and a capacitance, and the output of the fourth filter is constituted by a surface acoustic wave filter.
9. The high-frequency signal receiving apparatus according to claim 8, wherein the signal is input to the intermediate frequency filter, and a fourth filter including an inductance and a capacitance is connected at the beginning of the output of the second mixer, so that the loss is reduced. And NF is good. Suitable for use in areas where interference is weak.

According to a fourteenth aspect of the present invention, the fourth filter is a high-frequency signal receiving apparatus according to the eighth aspect of the present invention, which is a trapping circuit composed of an inductance and a capacitance. Price. Suitable for use in areas where the bandwidth of the disturbance is narrow.

According to a fifteenth aspect of the present invention, in the high frequency signal receiving apparatus according to the eighth aspect, the attenuation of the second intermediate frequency filter is set to approximately 40 dB, and the attenuation of the fourth filter is set to approximately 20 dB. The amount of attenuation of the fourth filter is approximately 20 dB, which can be realized by the pattern inductance and the capacitor, and the cost can be reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram of a high-frequency signal receiving apparatus according to Embodiment 1 of the present invention.
In FIG. 1, a high-frequency signal receiving apparatus according to the present invention includes an input terminal 31 to which a high-frequency digital signal is input, a signal input to the input terminal 31, and a signal 145.
High-pass filter 32 that passes frequencies above 0 MHz
And a band-pass filter 33 connected to the output of the high-pass filter 32 and passing a frequency from 1450 MHz to 1492 MHz. An output of the band-pass filter 33 is connected to one input and a local input is connected to the other input. The mixer 3 to which the output of the oscillator 34 is connected
5, a fixed filter 36 to which the output of the mixer 35 is connected, and an output of the fixed filter 36
a low-pass filter 38 connected to the input terminal 31 and passing a frequency of 245 MHz or less, and an output of the low-pass filter 38 and the other terminal 37b of the change-over switch 37. And a common terminal 37c of the changeover switch 37.
Is connected to one input and the other input is connected to the output of a local oscillator 40, and a band-pass filter connected to the output of the mixer 41 and passing a frequency of 38.912 MHz. 42, a mixer 44 having an output connected to one of the inputs of the band-pass filter 42 and the other input connected to the output of the local oscillator 43, and an output 2 connected to the mixer 44. It comprises a bandpass filter 45 for passing a frequency of 0.048 MHz and an output terminal 46 to which the output of the bandpass filter 45 is connected.

Here, the fixed filter 36 is a band-pass filter having a center frequency of 199.04 MHz and a bandwidth of approximately 1.4 MHz. The local oscillator 34 is a PLL circuit 4
7 is connected in a loop to select a channel. That is, the output frequency of the local oscillator 34 becomes 30
It is connected to a 1/49 frequency divider 49 and a 1/31 frequency divider 50. The outputs of the frequency dividers 49 and 50 are connected to one input of a phase comparator 52 via a switch 51. A reference frequency of 64 KHz is input to the other input of the phase comparator 52. This 6
The frequency of 4 KHz is generated by dividing the crystal unit 53 of 36.864 MHz into 1/576 by the frequency divider 54. The output of the phase comparator 52 is a low-pass filter 5
5 is connected to the input terminal of the local oscillator 34.

In the PLL circuit 47 configured as described above, the frequency divider 48 can change the frequency division ratio from 632 to 1/673, and the electronic changeover switch 51 can appropriately change the frequency dividers 49 and 50. The channel is selected by selecting. That is, the intermediate frequency output from the mixer 35 is a predetermined value (in the case of the present embodiment, 199.04M
Hz), the control of the frequency division ratio of the frequency divider 48 and the control of switching between the frequency dividers 49 and 50 are performed by the error minimizing means. This improves the intermediate frequency accuracy. The error minimizing means is a PLL
The microcomputer 47 controls the tuning operation of the circuit 47 by software. Therefore, no special hardware is required for this error minimizing means,
The size and the price can be reduced.

By providing such an error minimizing means, the output frequency of the mixer 35 is increased from 198.352 to 1
99.728 MHz, and the bandwidth is 1.376 MHz.
Becomes Therefore, the fixed filter 36 can be used, and the size and cost of the filter can be reduced. Also, since the comparison frequency is set as large as 64 KHz,
Phase noise can be reduced and errors can be prevented. By setting the comparison frequency from about 32 KHz to 256 KHz, it is possible to obtain good oscillation frequency characteristics with respect to phase noise.

The local oscillator 40 is also loop-connected to the PLL circuit 56. That is, the output frequency of the local oscillator 40 is connected to one input of the phase comparator 58 via the variable frequency divider 57. A frequency of 16 KHz is input to the other input of the phase comparator 58. This 16
The frequency of KHz is generated by dividing the frequency of the crystal oscillator 53 of 36.864 MHz by 1/576 by the frequency divider 54 and further dividing by 1/4 by the frequency divider 59. The output of the phase comparator 58 is connected to the input terminal of the local oscillator 40 via a low-pass filter 60. The output of the low-pass filter 60 is output from the tracking filter 39.
Is also connected to control the passing frequency.

In the PLL circuit 56 configured as described above, when the changeover switch 37 is switched to 37a to receive the L band, the local oscillator 40 is controlled in accordance with the output of the mixer 35, and 3
8.912 MHz is obtained. This frequency is mixed with the oscillating frequency of 36.864 MHz by the next mixer 44 to obtain 2.048
It has a frequency of MHz.

When the changeover switch 37 is switched to 37b to receive the V band, the frequency divider 57
Is used as a variable frequency divider, the oscillation frequency of the local oscillator 40 is controlled, and the mixer 41 is controlled to output a frequency of 38.912 MHz. Also, the tracking filter 39 is controlled to select a V-band high-frequency signal. The output of the mixer 41 is mixed with the oscillation frequency of 36.864 MHz in the next mixer 44 via the band-pass filter 42 to have a frequency of 2.048 MHz.

As described above, since the double super system in which the frequency is converted again by using the mixer 44 is used, it is possible to remove the interfering radio wave in the reception signal band.

The operation of the high-frequency signal receiving apparatus configured as described above will be described below. 1 and 2, the input terminal 31 has a frequency of 174 MHz as indicated by 70.
V band 71 from 245 MHz to 1 from 1450 MHz
A 492 MHz L band 72 high frequency digital signal is input.

It is assumed that the changeover switch 37 has been switched to 37a to select the L band. Then,
The L-band 72 input from 1450 MHz to 1492 MHz is mixed with the signal of the local oscillator 34 by the mixer 35 and
As shown in FIG. 3, from 198.352 MHz shown earlier to 19
It is converted to a frequency 74 of 9.728 MHz and is selected.
This signal is controlled by the local oscillator 40 and
5 is converted to an intermediate frequency 75a of 38.912 MHz. This intermediate frequency 75 a is
6 is converted to an intermediate frequency 76a of 2.048 MHz and output from the output terminal 46.

Next, it is assumed that the changeover switch 37 has been switched to 37b in order to select the V band. Then, the signal of the V band 71 from 174 MHz to 245 MHz is selected by the tracking filter 39 and the mixer 41, and then converted into the 38.912 MHz intermediate frequency 75 a shown by 75 in FIG. This intermediate frequency 75a
Is converted by the local oscillator 43 into an intermediate frequency 76a of 2.048 MHz shown at 76 and output from the output terminal 46.

As described above, in this high-frequency signal receiving apparatus, the voltage of V
Two bands, band 71 and L band 72, can be received.

Reference numeral 77a in FIG. 3 denotes the bandwidth of the frequency output from the mixer 35 when there are no frequency dividers 49 and 50, and reference numeral 78a 78 denotes that the frequency dividers 49 and 50 are appropriately switched to minimize the error. This is the bandwidth of the frequency output from the mixer 35 when the error is set to the minimum by the converting means. Thus, the setting of the frequency division ratio of the variable frequency divider 48 and the frequency divider 4
By using the error minimizing means for appropriately switching between 9 and 50, the bandwidth can be narrowed, and the comparison frequency can be increased to reduce the phase noise.

(Embodiment 2) FIG. 4 is a block diagram of a high-frequency signal receiving apparatus according to Embodiment 2 of the present invention.
The second embodiment relates to the switch 37 in the first embodiment and thereafter, and the portion before the switch 37 is simplified. The second embodiment is suitable when there is a large signal interference wave near a desired high-frequency signal.

In FIG. 4, the high-frequency signal receiving apparatus of the present invention includes an input terminal 131 to which the common terminal 37c of the changeover switch 37 of FIG. 1 is connected, and an amplifier 132 to which a signal input to the input terminal 131 is connected. And the mixer 1 having the output of the amplifier 132 connected to one input and the output of the local oscillator 133 connected to the other input.
And a SAW filter 136 connected to the output of the mixer 134 and passing the intermediate frequency 135
An intermediate frequency amplifier 137 to which the output of the SAW filter 136 is connected, a filter 138 to which the output of the intermediate frequency amplifier 137 is connected and which is formed by an inductance and a capacitor formed in a pattern;
The output of the filter 138 is connected to one input and the other input is connected to the mixer 140 to which the output of the local oscillator 139 is connected. The output of the mixer 140 is connected to the intermediate frequency 143. Filter 1
41, and an output terminal 142 to which the output of the filter 141 is connected. Note that the filter 138 may be a SAW filter. In this case, a larger attenuation can be obtained.

Here, the input terminal 131 is connected to 145 in FIG.
It is assumed that a signal including several channels of a high-frequency digital signal as shown in FIG. The frequency of the high-frequency digital signal 145 is 200 MHz, and its bandwidth 1
45a is 1.5 MHz. It is also assumed that there is an interference signal 146 that is 40 dB higher than the high-frequency digital signal 145 at a position of 204 MHz that is 4 MHz above the high-frequency digital signal 145.

In the second embodiment, the intermediate frequency 135
Is 38.9 MHz, and the oscillation frequency 1 of the local oscillator 139 is
70 is 36.9 MHz, and the intermediate frequency 143 is 2 MHz.
Is set to

FIG. 6 shows a characteristic 147 of the SAW filter 136.
The center frequency 148 is 38.9 MHz, the bandwidth 149 is 1.4 MHz, the attenuation in this bandwidth is approximately 2 dB, and the attenuation 150 outside the band is 40 dB.

FIG. 7 shows a high-pass filter 1 formed by an inductance formed by a pattern and a capacitor.
38, and 38.9 of the intermediate frequency 135.
MHz is passed (the attenuation is about 0.5 dB), and the attenuation 152 at an interference frequency 4 MHz lower than the intermediate frequency 135 is about 20 dB. It is to be noted that the larger the amount of attenuation 152 is, the better, but it is practical to set this level to obtain a low-cost filter 138. 5, 6 and 7, the vertical axis represents the level (dB), and the horizontal axis represents the frequency (MHz).

The operation of the high-frequency signal receiving apparatus configured as described above will be described below. Input terminal 13
1 is mixed with the output of the local oscillator 133 by the mixer 134 and the intermediate frequency 13
Get 5. As the intermediate frequency 135, an intermediate frequency (38.9 MHz) 135a of a desired signal is selected by a SAW filter 136 having a center frequency of 38.9 MHz. This signal 135a passes through an intermediate frequency amplifier 137 to obtain an amplified signal 135b. This signal 135b passes through a high-pass filter 138 to obtain a signal 135c. The signal 135c is mixed with the output of the local oscillator 139 that outputs the oscillation frequency 170 of 36.9 MHz by the mixer 140 to obtain the intermediate frequency 143 of 2 MHz. Then, the intermediate frequency 143 is output from the output terminal 142 via the band pass filter 141 of 2 MHz.

Here, the high-frequency digital signal input from the input terminal 131 is as follows when the oscillation frequency of the local oscillator 133 is changed. That is, when the changeover switch 37 of the first embodiment selects the V band of 37b, a desired radio wave is selected by changing the frequency of the local oscillator 133.

Next, a case where an interfering wave exists will be described.
As shown in FIG. 8A, it is assumed that, for example, when a desired wave 145 of 200 MHz is to be received, there is a 204 MHz interference wave 146 that is 4 MHz higher than the desired wave 145.
Note that the interference wave 146 has a level difference of 1 from the desired wave 145.
As shown in FIG.

Since the intermediate frequency 135 is 38.9 MHz, the oscillation frequency 133a of the local oscillator 133 is set to 238.
Set to 9 MHz. Then, the desired wave 145 is mixed with 238.9 MHz of the local oscillation frequency 133a of the local oscillator 133 from the mixer 134 to output a desired wave signal 145a of 38.9 MHz. At this time, the interference wave 146 is also changed to the local oscillation frequency. 133a mixed with 238.9MHz of 3a
An 4.9 MHz interference wave signal is output.

Here, the center frequency of the SAW filter 136 is set to 38.9 MHz, which is the intermediate frequency.
Assuming that the attenuation at about 0.7 MHz away from the center frequency is 40 dB, the interfering wave 146 is attenuated by 40 dB as compared with the desired wave 145, and as shown in FIG. The signal level becomes the same as that of the signal 145a.

These signals 145a and 146a pass through a high-pass filter 138 via an intermediate frequency amplifier 137. The high-pass filter 138 controls the interference signal 1
20 dB is attenuated for the frequency of 34.9 MHz of 46a. That is, in the output of the high-pass filter 138, FIG.
As shown in (c), the interference wave signal 146c has a level difference 162 of 20 dB as compared with the desired wave signal 145c. The desired wave signal 145c passes through the mixer 140,
As shown in (d), it overlaps with the interference signal 146d, but its level is extremely low. Here, the local oscillator 139
The oscillation frequency 170 is fixed at 36.5 MHz, and the intermediate frequency 143 is set at 2 MHz.

Therefore, even if a high-output interference wave 146 is present in the vicinity of the desired wave 145, the desired wave is hardly affected by the interference wave at the output terminal 142, and no reception error occurs. That is, normal reception becomes possible. 8A, 8B, 8C, and 8D, the vertical axis represents the signal level (dB), and the horizontal axis represents the frequency (MHz).

(Third Embodiment) In the third embodiment, when the intermediate frequency 135 is 38.9 MHz, the local oscillation frequency of the local oscillator 139 is set to 40.9 MHz in order to create an intermediate frequency 143 of 2 MHz. . In this case, an interference frequency lower than the desired wave frequency becomes a problem.

Therefore, in the third embodiment, the high-pass filter 138 is used instead of the high-pass filter 138.
A low-pass filter that attenuates 2.9 MHz by approximately 20 dB is used. Hereinafter, description will be made with reference to FIG. FIG. 9 (a)
As shown in, for example, when it is desired to receive a desired wave 145 of 200 MHz, it is assumed that there is an interference wave 166 of 196 MHz, which is 4 MHz lower than the desired wave 145. It is assumed that the interference wave 166 is 40 dB higher than the desired wave 145 as indicated by a level difference 167.

Since the intermediate frequency 135 is 38.9 MHz, the oscillation frequency of the local oscillator 133 is set to 238.9 MHz. Then, the desired wave 145 is mixed with the local oscillation frequency 133a from the mixer 134 to output the desired wave signal 145a of 38.9 MHz.
6 is also mixed with 238.9 MHz of the local oscillation frequency 133a to output a 42.9 MHz interference signal.

Here, the center frequency of the SAW filter 136 is set to 38.9 MHz which is an intermediate frequency.
Assuming that the attenuation at about 0.7 MHz away from the center frequency is 40 dB, the interference wave 166 is attenuated by 40 dB as compared with the desired wave 145, and as shown in FIG. The signal level becomes the same as that of the signal 145a.

These signals 145a and 166a pass through a low-pass filter via an intermediate frequency amplifier 137. This low-pass filter is assumed to have a characteristic of attenuating by 20 dB with respect to the frequency 42.9 MHz of the interference wave signal 166a. That is, in the output of the low-pass filter, as shown in FIG. 9C, the level difference 168 of the interference wave signal 166c is 20 dB as compared with the desired wave signal 145c. Therefore, when the desired wave signal 145c passes through the mixer 140, it overlaps with the interference wave signal 166d as shown in FIG. 9D, but its level becomes extremely low.

Therefore, even if a high-output interference wave 166 exists near the desired wave 145, the influence of the interference wave on the desired wave is almost eliminated at the output terminal 142, and no reception error occurs. That is, normal reception becomes possible.

Here, the oscillation frequency of local oscillator 139 is fixed at 40.9 MHz, and intermediate frequency 143 is set at 2 MHz. 9 (a), (b), (c),
In both (d), the vertical axis represents the signal level (dB), and the horizontal axis represents the frequency (MHz).

(Embodiment 4) In Embodiment 4, the high-pass filter 138 shown in Embodiment 2 or the low-pass filter shown in Embodiment 3 is replaced with the SAW filter 13.
Connected before 6. In this case, the high-pass filter 138 or the low-pass filter is
Since the loss in the pass band is smaller than that in No. 6, NF is improved.

(Fifth Embodiment) In the fifth embodiment, the output frequency of the local oscillator 139 is reduced by using a trap circuit instead of the high-pass filter 138 shown in the second embodiment or the low-pass filter shown in the third embodiment. On the other hand, it attenuates the frequency having a symmetry of 38.9 MHz which is the intermediate frequency. In this embodiment, the circuit is formed by the trap path, and the circuit can be simplified, so that the cost can be reduced.

[0066]

As described above, according to the present invention, an input terminal to which a high-frequency signal is input, a signal input to this input terminal is supplied to one input, and an oscillation frequency is applied to the other input. A mixer to which the output of the variable local oscillator is supplied, a filter that passes an intermediate frequency output from the mixer, an output terminal to which the output of the filter is supplied, and one of the outputs of the local oscillator A phase comparator supplied to an input and having a second input to which a comparison frequency is input, and a low-pass filter connected between an output of the phase comparator and an input of the local oscillator; Is set to a fixed filter, and set to a large comparison frequency such that an integral multiple of the comparison frequency is not equal to the channel interval frequency of the high-frequency signal. Since the high frequency signal is mixed with the output of the local oscillator whose oscillation frequency is variable by the mixer, the output from the mixer is substantially constant, and the filter connected to the mixer is A fixed filter can be used. Therefore, the size and the price are lower than those of the tracking filter.

Further, since the comparison frequency is set to a large value so that the integral multiple of the comparison frequency does not become equal to the channel interval frequency of the high-frequency signal, phase noise is reduced, and errors are reduced in demodulation of digital signals.

[Brief description of the drawings]

FIG. 1 is a block diagram of a high-frequency signal receiving device according to a first embodiment of the present invention.

FIG. 2 is a frequency transition diagram of the same.

FIG. 3 is a diagram showing a frequency bandwidth output from the mixer.

FIG. 4 is a block diagram of a high-frequency signal receiving device according to a second embodiment of the present invention.

FIG. 5 is a level diagram of a signal input to an input terminal of the high-frequency signal receiving device.

FIG. 6 is a characteristic diagram of a SAW filter used in the high-frequency signal receiving device.

FIG. 7 is a characteristic diagram of a high-pass filter for attenuating an interfering wave.

8A is a level diagram by a simplified display of a signal input to an input terminal. FIG. 8B is a level diagram of a signal output from the SAW filter. FIG. 8C is a level diagram of a signal output from the SAW filter. The signal level diagram (d) is the level diagram of the signal output from the output terminal.

9A is a level diagram of a signal input to an input terminal in the third embodiment, FIG. 9B is a level diagram of a signal output from the SAW filter, and FIG. The level diagram of the output signal (d) is the level diagram of the signal output from the output terminal.

FIG. 10 is a block diagram of a conventional high-frequency signal receiving device.

FIG. 11 is the same frequency transition diagram.

[Explanation of symbols]

 31 input terminal 34 local oscillator 35 mixer 36 fixed filter 46 output terminal 52 phase comparator 55 low-pass filter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Osamu Kuramoto, Inventor 1006, Kazuma, Kadoma, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. Terms (reference) 5K020 AA08 BB06 BB08 DD02 DD11 EE01 EE04 EE05 FF04 HH11 KK02

Claims (15)

[Claims] An input terminal to which a high-frequency signal is input, and a signal input to the input terminal is supplied to one input and an output of a local oscillator whose oscillation frequency is variable is supplied to the other input. Mixer, a filter that passes an intermediate frequency output from the mixer, an output terminal to which the output of the filter is supplied, and an output of the local oscillator that is supplied to one input and to the other input. Comprises a phase comparator to which a comparison frequency is input, and a low-pass filter connected between the output of the phase comparator and the input of the local oscillator, and the filter that passes the intermediate frequency is a fixed filter. A high-frequency signal receiving apparatus set to a comparative frequency that is so large that an integral multiple of the comparative frequency is not equal to the channel spacing frequency of the high-frequency signal. 2. The channel spacing frequency is approximately 1.712M.
2. The high-frequency signal receiving device according to claim 1, wherein the comparison frequency is 64 KHz in the case of Hz. 3. A variable frequency divider between a local oscillator and an input of a phase comparator, and a frequency divider capable of switching between 1 / n and n + 1/1, wherein a variable frequency divider is provided. The difference between the intermediate frequency output from the mixer and the predetermined frequency is minimized by controlling the frequency division ratio and controlling the switching of the frequency divider between 1 / n and 1 / n + 1. 3. The high-frequency signal receiving apparatus according to claim 2, further comprising an error minimizing means controlled to be equal to or smaller than the threshold. 4. The high-frequency signal receiving device according to claim 3, wherein the error minimizing means is constituted by software. 5. The high-frequency signal receiving device according to claim 3, wherein the value of n is 30. 6. A switch connected to one terminal of an output of a fixed filter that passes an intermediate frequency, a tracking filter connected between the other terminal of the switch and an input terminal, and the switch. A second mixer having a common terminal connected to one terminal and the other terminal connected to the output of a second local oscillator having a PLL circuit connected in a loop, and an output of the second mixer. A second intermediate frequency filter to which the fixed filter is supplied, and an output terminal to which the output of the second intermediate frequency filter is supplied, wherein the frequency band of the fixed filter is substantially equal to the frequency band of the tracking filter. Item 2. The high-frequency signal receiving device according to Item 1. 7. A third mixer in which the output of the second intermediate frequency filter is connected to one terminal and the output of a third local oscillator is connected to the other terminal. 7. The high-frequency signal receiving apparatus according to claim 6, further comprising a third intermediate frequency filter to which an output of the third intermediate frequency filter is supplied, and an output terminal to which an output of the third intermediate frequency filter is connected. 8. A fourth filter for attenuating a frequency symmetrical to a second intermediate frequency of a desired signal with respect to a local oscillation frequency output from a third local oscillator is connected in series with the second filter. The high-frequency signal receiving device according to claim 7. 9. When a surface acoustic wave filter is used as the second intermediate frequency filter and the desired second intermediate frequency is higher than the frequency output from the third local oscillator,
The high-frequency signal receiving device according to claim 8, wherein the fourth filter is a high-pass filter including an inductance and a capacitance. 10. When a surface acoustic wave filter is used as the second intermediate frequency filter, and the desired second intermediate frequency is lower than the frequency output from the third local oscillator, the fourth filter has an inductance and a capacitance. The high-frequency signal receiving device according to claim 8, wherein the high-frequency signal receiving device is a low-pass filter configured by: 11. The high-frequency signal receiving apparatus according to claim 8, wherein an amplifier is inserted between the second intermediate frequency filter and the fourth filter. 12. The high-frequency signal receiving device according to claim 8, wherein a surface acoustic wave filter is used as the second intermediate frequency filter, and an output of the filter is input to a fourth filter including an inductance and a capacitance. . 13. The high-frequency signal reception according to claim 8, wherein the fourth filter is constituted by an inductance and a capacitance, and an output thereof is inputted to a second intermediate frequency filter constituted by a surface acoustic wave filter. apparatus. 14. The high-frequency signal receiving apparatus according to claim 8, wherein the fourth filter is a trap circuit including an inductance and a capacitance. 15. The high-frequency signal receiving apparatus according to claim 8, wherein the attenuation of the second intermediate frequency filter is approximately 40 dB, and the attenuation of the fourth filter is approximately 20 dB.