JPH07202743A - Frequency converter - Google Patents

Abstract

PURPOSE:To provide a frequency converter immune to image interference and suppressing leakage of a local oscillator signal from an RF input terminal in the frequency converter of 21GHz band. CONSTITUTION:An RF signal at a 21GHz and received from an RF input terminal 15 is amplified by an RF amplifier 11. Then the amplified signal is frequency-converted into an IF signal by a mixer 12 and a local oscillator 13. Then a mixer 17 and a local oscillator 13 are used to frequency-convert the IF signal into an IF output signal of 1GHz band again and the result is outputted from an IN output terminal 16. The difference between frequencies of the local oscillators 13, 18 is selected higher than the maximum frequency of the IF output signal. Thus, the local oscillator signal of the local oscillator 13 is frequency-converted by the mixer 17 to prevent the frequency-converted signal from being a interference signal of an IF output signal.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a high frequency signal of 21 GHz band (21.4 to 22.0 GHz) distributed for broadcasting satellite service.
The present invention relates to a frequency conversion device that converts an intermediate frequency signal in the GHz band.

[0002]

2. Description of the Related Art At present, satellite broadcasting using frequencies in the 12 GHz band is already in practical use. Satellite broadcasting using frequencies in the 21 GHz band is also planned in the future.

In the 12 GHz band frequency converter for satellite broadcasting, the RF signal is 11.7 to 12.5 GHz and the local oscillation frequency is 10 GHz.
The 1 GHz band is generally often used as the band and IF output signal. Even in the frequency converter for 21 GHz band satellite broadcasting, it is conceivable to match the IF output signal with the frequency of the 12 GHz band satellite broadcasting IF output signal, or to set it to a close value of 1 GHz band.

FIG. 3 shows the structure of a conventional frequency converter for 21 GHz band satellite broadcasting. The 21 GHz frequency converter 30 has a high frequency (hereinafter referred to as RF) input terminal 31 with an RF
The mixer 33 is connected via the amplifier 32. Mixer 3
3, a local oscillator 34 having a frequency of 20.45 GHz is connected,
The input signal (21.4 to 22.0 GHz) is converted into an intermediate frequency (hereinafter referred to as IF), and its output is amplified by the IF amplifier 35. Here, the frequency of the IF output signal output from the IF output terminal 36 of the frequency conversion device 30 is 12
In order to match the frequency of the IF output signal of the frequency converter in the GHz band, 0.95 to 1.55 GHz is selected.

[0005]

[Problems to be Solved by the Invention]
In the frequency converter for satellite broadcasting in the GHz band, the RF signal frequency f _R (21.4 to 22.0 GHz) and the local oscillation frequency f _L (20.45 G).
The ratio of the local frequency to the RF signal frequency (f _R −f)
_L ) / f _R is as small as 0.044.

This ratio is about 1/2 of 0.079 in the frequency converter for satellite broadcasting in the 12 GHz band. This is because the RF signal frequency is doubled from 11.7 to 12.5 GHz to 21.4 to 22.0 GHz, while the IF output signal frequencies are matched.

Therefore, as compared with the frequency converter for satellite broadcasting in the 12 GHz band, the frequency converter for the 21 GHz band is
(1) It is difficult to suppress the leakage of the locally generated signal from the RF input terminal 31. Also, the RF signal frequency (21.4 to 22.0
Since (GHz) and the image signal frequency (18.9 to 19.5 GHz) are close to each other, (2) it is weak against image interference. (3) There is a problem that the conversion loss characteristic of the mixer 33 is easily deteriorated due to the insufficient image suppression ratio of the mixer 33.

In particular, in a frequency conversion device composed of a microwave integrated circuit, the no-load Q value of a filter that passes an RF signal or blocks an image signal or a local signal cannot be increased, so that the out-of-band characteristics are sharp. It is difficult to construct such a filter, and the fact that the RF signal frequency is close to the local oscillation frequency and the image signal frequency has been a serious problem in terms of local leakage and image interference.

The present invention has been made in view of the above points, and eliminates the drawbacks of the above-described conventional example, suppresses local leakage from the RF input terminal 31 of the frequency converter of the 21 GHz band, and also causes image interference. An object is to provide a strong frequency converter.

[0010]

According to a first aspect of the present invention, a first local oscillator that outputs a local oscillation signal lower than a high frequency signal, and a local oscillation signal and a high frequency signal of the first local oscillator are input. , A first mixer for converting into a first intermediate frequency signal, a second local oscillator for outputting a local oscillation signal, a local oscillation signal of the second local oscillator and a first intermediate frequency signal, Second converting to a second intermediate frequency signal
And a mixing frequency of the first local oscillator and the second local oscillator so that the frequency difference between the first local oscillator and the second local oscillator is higher than the maximum frequency of the second intermediate frequency signal. It is characterized by setting.

According to a fifth aspect of the present invention, there is provided a first local oscillator which outputs a local oscillation signal lower than a high frequency signal, and a first local oscillator.
A first mixer for receiving a local oscillation signal and a high frequency signal of the local oscillator and converting the signal to a first intermediate frequency signal, a second local oscillator for outputting the local oscillation signal, and a local portion of the second local oscillator. A second mixer which receives the oscillation signal and the first intermediate frequency signal and converts the second intermediate frequency signal into a second intermediate frequency signal, wherein the frequency difference between the first local oscillator and the second local oscillator is the second The frequency of the first local oscillator and the frequency of the second local oscillator are set to be lower than the minimum frequency of the intermediate frequency signal.

[0012]

According to the invention of claim 1 of the present application having the above characteristics, the high frequency signal is converted into the first intermediate frequency signal by the first local oscillator and the first mixer, and the second local frequency signal is further converted. The second intermediate frequency signal is converted by the oscillator and the second mixer. The local oscillation frequency is set so that the frequency difference between the first and second local oscillators is higher than the maximum frequency of the second intermediate frequency signal.

According to the invention of claim 5, the frequency difference between the first and second local oscillators is set to be lower than the minimum frequency of the second intermediate frequency signal. By doing so, it is possible to set the image signal frequency as well as the local signal frequency far from the RF signal frequency, and it is easy to realize a frequency conversion device that is strong against local signal leakage and image interference. it can.

[0014]

1 is a block diagram showing a frequency converter 10 according to a first embodiment of the present invention. 21G in this figure
RF input terminal 15 for RF signals in the Hz band (21.4 to 22.0 GHz)
It is amplified by the RF amplifier 11 via and is input to the first mixer 12. The mixer 12 has a local oscillation frequency of 9.
A first local oscillator 13 of 3 GHz is connected. The mixer 12 inputs the IF signal of the 12 GHz band (12.1 to 12.7).
Frequency conversion to GHz), the output of which is the first
Is amplified by the IF amplifier 14 and input to the second mixer 17. A second local oscillator 18 having a local oscillation frequency of 11.15 GHz is connected to the mixer 17. The mixer 17 frequency-converts the input signal again into an IF output signal (0.95 to 1.55 GHz) which is the second IF signal in the 1 GHz band.
The output is amplified by the IF amplifier 19 and the IF output terminal 1
It is output from 6.

The frequency of the IF output signal output from the mixer 17 is selected so as to match the frequency of the IF output signal of the 12 GHz band frequency converter for satellite broadcasting. Furthermore, the local oscillator 13 (9.3 GHz) and the local oscillator 1
The frequency difference (1.85 GHz) of 8 (11.15 GHz) is selected higher than the maximum frequency (1.55 GHz) of the IF output signal.

The frequency conversion device according to the first embodiment has the following effects. (1) Image signal frequency of mixer 12 (2.8-3.4 G
Since (Hz) is completely distant from the RF signal frequency (21.4 to 22.0 GHz), the structure of the image signal blocking filter can be simplified and a frequency converter that is very strong against image interference can be provided. At the same time, since the image signal processing of the mixer 12 is facilitated, the conversion loss characteristic of the mixer 12 can be improved.

(2) Since the frequencies of the local oscillators 13 and 18 are reduced to about 1/2 of the frequency of the conventional local oscillator of FIG. 3 (20.45 GHz), it is technically easy to realize. There is. Particularly in a local oscillator using a dielectric resonator, it is easy to realize a local oscillation signal with small phase noise.

(3) Since the frequencies of the local oscillator 13 and the local oscillator 18 are far apart from the RF signal frequency, the construction of the local oscillator signal blocking filter becomes easy, and the local oscillator signal from the RF input terminal 15 is generated. It becomes easy to suppress the leakage of

For example, when the waveguide WR42 corresponding to the RF signal frequency in the 21 GHz band is used for the RF input terminal 15, the cutoff frequency of this waveguide is about 14 GHz.
Only by making the signal input structure of the frequency converter of the 21 GHz band a circular or rectangular waveguide (for example, WR42) which is commonly used, this waveguide functions as an image signal blocking filter and a local signal blocking filter, It is possible to provide a frequency converter in the 21 GHz band that is strong against image interference and has little local signal leakage.

The frequency difference (1.85 GHz) between the local oscillator 13 (9.3 GHz) and the local oscillator 18 (11.15 GHz) is selected higher than the maximum frequency (1.55 GHz) of the IF output signal. Moreover, the image rejection type mixer is used as the mixer 17, and the image rejection band of the mixer 17 is realized in a wider band than the image signal frequency band (9.6 to 10.2 GHz), and the local oscillator 13 has a local oscillation frequency (9.3 GHz). ) Is placed in the image rejection band of the mixer 17, preventing the local oscillation signal of the local oscillator 13 from being frequency-converted by the mixer 17 and being output to the IF output terminal 16 as an interfering signal. it can.

The first embodiment shown in FIG. 1 is a local oscillator 13.
(9.3 GHz) and the local oscillator 18 (11.15 GHz) frequency difference (1.85 GHz) IF output signal maximum frequency (1.55 GHz)
This is an example in which the frequency difference between the two local oscillators is higher than the maximum frequency of the IF output signal. In Table 1, RF signal, IF signal,
IF output signal, local oscillator signals a and b of two local oscillators (a local oscillator signal of the previous stage local oscillator 13 is distinguished by a, and a local oscillator signal of the latter stage local oscillator 18 is distinguished by a suffix of b), and two mixed Image signals a and b of the mixers 12 and 17 (the mixer 12 of the previous stage
The image signal of (a) and the image signal of the mixer 17 in the subsequent stage are distinguished by the suffix of b), and the frequency difference between the two local oscillators.

[Table 1]

In Table 1, Case 1 corresponds to the first embodiment shown in FIG. In the example of Case 2 in Table 1, the local signal a
Is frequency-converted by the mixer 17, and I
In order to prevent it from being output to the F output terminal 16, the frequency (11.15 GHz) of the local oscillation signal a is not far from the frequency band (10.25 to 10.85 GHz) of the IF signal,
It is necessary to prevent the local oscillation signal a from being input to the mixer 17 by using a relatively sharp band stop filter or the like. Furthermore, the frequency of the image signal a of the mixer 12 (0.3
.About.0.9 GHz) is set so as not to overlap the frequency of the IF output signal, so that the image signal a generated in the mixer 12 is prevented from becoming an interfering signal of the IF output signal. The other effects are the same as those of the first embodiment of case 1.

In the case 3 embodiment of Table 1, the local oscillator signal b
The frequency (10.55 GHz) is the frequency of the IF signal (9.0 to 9.
6 GHz), the IF output signal spectrum is an inverted spectrum of the RF signal. Therefore,
The spectrum of the RF signal is inverted when the IF output signals of multiple channels composed of signals of multiple carriers are tuned and frequency-converted to an IF signal of 403 MHz as in the case of a 12 GHz band satellite broadcasting reception system. The same spectrum as is obtained. In other words, in case 1 and case 2, since the 403 MHz IF signal has an inverted spectrum, frequency conversion is required again to return the inverted spectrum to the non-inverted spectrum. On the other hand, in case 3, since it is possible to directly demodulate the modulated signal of the non-inverted spectrum from the IF signal of 403 MHz, the frequency conversion is performed again even in the case of the modulated signal which is not preferable to be demodulated from the modulated signal of the inverted spectrum. You don't have to

Moreover, even when it is desired to demodulate a modulated signal at a frequency lower than 403 MHz (for example, 140 MHz), frequency conversion can be performed without inverting the spectrum. The other effects are the same as those of the first embodiment of case 1.

In the embodiment of case 4 in Table 1, the local oscillator signal b
Frequency (12.4 GHz) is the frequency of the IF signal (10.85 ~ 1
Since it is higher than 1.45 GHz), the spectrum of the IF output signal is an inverted spectrum of the RF signal. Therefore, the spectrum is inverted again when the IF output signals of a large number of channels composed of signals of a plurality of carriers are selected and frequency-converted to an IF signal of 403 MHz as in the reception system for 12 GHz band satellite broadcasting, and the RF signal The same spectrum as the spectrum of is obtained. In other words, in case 4, since it is possible to demodulate the non-inverted spectrum modulated signal directly from the 403 MHz IF signal as in case 3, even in the case of a modulated signal in which it is not desirable to demodulate from the inverted spectrum modulated signal. It is not necessary to perform frequency conversion again.

Moreover, even if it is desired to demodulate the modulated signal at a frequency lower than 403 MHz (for example, 140 MHz), frequency conversion can be performed without inverting the spectrum. The other effects are the same as in the case 2 embodiment.

FIG. 2 is a block diagram showing a frequency converter 20 according to a second embodiment of the present invention. 21 in this figure
RF input terminal 2 for RF signals in the GHz band (21.4 to 22.0 GHz)
The signal is amplified by the RF amplifier 21 via 5 and input to the first mixer 22. The mixer 22 has a local oscillation frequency
A first local oscillator 23 of 11.8 GHz is connected. The mixer 22 inputs the IF signal of the 9 GHz band (9.6 to 10.2).
Frequency conversion to GHz), the output of which is the first
Is amplified by the IF amplifier 24 and input to the second mixer 27. A second local oscillator 28 having a local oscillation frequency of 11.15 GHz is connected to the mixer 27. The mixer 27 frequency-converts the input signal into an IF output signal (0.95 to 1.55 GHz) which is the second IF signal in the 1 GHz band.
The output is amplified by the IF amplifier 29 and the IF output terminal 2
It is output from 6.

The frequency conversion device according to the second embodiment has the following effects. (1) Image signal frequency of the mixer 22 (1.6 to 2.2 G
Since (Hz) is completely distant from the RF signal frequency (21.4 to 22.0 GHz), the structure of the image signal blocking filter can be simplified and a frequency converter that is very strong against image interference can be provided. At the same time, since the image signal processing of the mixer 22 is facilitated, the conversion loss characteristic of the mixer 22 can be improved.

(2) Since the frequencies of the local oscillators 23 and 28 are reduced to about half the frequency (20.45 GHz) of the conventional local oscillator of FIG. 3, it is technically easy to realize. There is. Particularly in a local oscillator using a dielectric resonator, it is easy to realize a local oscillation signal with small phase noise.

(3) Since the frequencies of the local oscillator 23 and the local oscillator 28 are far apart from the RF signal frequency, the construction of the local oscillation signal blocking filter becomes easy, and the local oscillation signal from the RF input terminal 25 is transmitted. It becomes easy to suppress the leakage of

For example, when the waveguide WR42 corresponding to the RF signal frequency in the 21 GHz band is used for the RF input terminal 25, the cutoff frequency of this waveguide is about 14 GHz.
By only using a circular or rectangular waveguide (eg, WR42) that is commonly used as the signal input structure of the 21 GHz band frequency converter, this waveguide functions as both an image signal blocking filter and a local signal blocking filter. It is possible to provide a frequency converter in the 21 GHz band that is strong against image interference and has little local signal leakage.

(4) Frequency of the local oscillator 28 (11.15 G
Since (Hz) is higher than the frequency of the IF signal (9.6 to 10.2 GHz), the spectrum of the IF output signal is the inversion spectrum of the RF signal. Therefore, when the IF output signal composed of signals of a plurality of carriers is selected and frequency-converted to an IF signal of 403 MHz as in the 12 GHz band satellite broadcasting receiving system, the spectrum is inverted again, and the spectrum of the RF signal is changed. The same spectrum is obtained. That is, when the modulated signal is directly demodulated from the 403 MHz IF signal, the demodulation can be performed with the modulated signal of the non-inverted spectrum. Moreover, frequencies lower than 403 MHz (for example, 140 MHz
Even if you want to demodulate the modulated signal in z), frequency conversion is possible without inverting the spectrum.

The frequency difference (0.65 GHz) between the local oscillator 23 (11.8 GHz) and the local oscillator 28 (11.15 GHz) is IF.
It is selected lower than the minimum frequency (0.95 GHz) of the output signal. Moreover, the image rejection type mixer is used as the mixer 27, and the image rejection band of the mixer 27 is realized in a wider band than the image signal frequency band (12.1 to 12.7 GHz), and the frequency of the local oscillator 23 (11.8 GHz) is mixed. Bowl 2
By arranging the signal in the image rejection band of No. 7, it is possible to prevent the local oscillation signal of the local oscillator 23 from being frequency-converted by the mixer 27 and output to the IF output terminal 26 as an interfering signal.

The second embodiment shown in FIG. 2 is a local oscillator 23.
The frequency difference (0.65 GHz) between the local oscillator 28 (11.15 GHz) (11.8 GHz) and the minimum frequency of the IF output signal (0.95 GHz)
Although it is an example in which the frequency difference between the two local oscillators is lower than the minimum frequency of the IF output signal, Table 2 shows another example. In Table 2, RF signal, IF signal,
IF output signal, local oscillator signals a and b of two local oscillators (local oscillator signal of the local oscillator 23 in the preceding stage is distinguished by a, and local oscillator signal of the latter local oscillator 28 is distinguished by a suffix of b) and two mixed Of the image signals a and b of the mixer (the image signal of the mixer 22 at the front stage is distinguished from the image signal of the mixer 27 at the rear stage by a suffix of b) and the frequency difference between the two local oscillators.

[Table 2] Case 7 in Table 2 corresponds to the second embodiment in FIG. In the embodiment of case 5 in Table 2, the frequency of the local oscillator signal b (10.55 G
Hz) is lower than the frequency of the IF signal (11.5 to 12.1 GHz), the spectrum of the IF output signal is the same as the spectrum of the RF signal. Therefore, when the IF output signal composed of signals of a plurality of carriers is tuned and frequency-converted into an IF signal of 403 MHz as in the 12 GHz band satellite broadcasting reception system, the spectrum is inverted and a frequency lower than 403 MHz is used. If you want to demodulate the modulated signal with 403 MHz
In order to return the inversion spectrum of the IF signal of the above to the signal of the non-inversion spectrum, for example, the IF signal of 403 MHz is 543 M
If the frequency is again converted to a 140 MHz signal by a fixed oscillator of Hz, a 140 MHz signal having a non-inverted spectrum can be obtained, and the modulated signal can be demodulated at a low frequency of 140 MHz. The other effects are the same as those in the case 7 (FIG. 2).

In the embodiment of case 6 in Table 2, the local signal a
The frequency of the local signal a (10.55 GHz) is in the frequency band (10.85 to 11.45 GHz) of the IF signal in order to prevent the signal from being frequency-converted by the mixer in the subsequent stage and output to the IF output terminal 26 as an interfering signal. Since it is not far away from the local oscillation signal a
Must be prevented from being input to the mixer at the subsequent stage. Further, since the frequency (0.3 to 0.9 GHz) of the image signal a of the former mixer does not overlap with the frequency of the IF output signal, the image signal a generated in the former mixer is the IF output signal. To prevent it from becoming an interfering signal. The other effects are the same as those of the case 5 embodiment.

In the case 8 embodiment of Table 2, the local oscillator signal a
The frequency of the local oscillator signal a (11.15 GHz) is in the frequency band of the IF signal (10.25 to 10.85 GHz) in order to prevent the signal from being frequency-converted by the mixer in the subsequent stage and output as an interfering signal to the IF output terminal 26. Since it is not far away from the local oscillation signal a
Must be prevented from being input to the mixer at the subsequent stage. Further, since the frequency (0.3 to 0.9 GHz) of the image signal a of the former mixer does not overlap with the frequency of the IF output signal, the image signal a generated in the former mixer is the IF output signal. To prevent it from becoming an interfering signal. The other effects are the same as those in the case 7 (FIG. 2).

[0037]

As described above, according to the inventions of claims 1 to 8 of the present application, the following effects can be obtained. (1) Since the interval between the image signal frequency and the RF signal frequency can be widened, it is possible to configure a frequency converter that is strong against image interference.

(2) Since the frequency of the local oscillator is reduced to about 1/2 of the frequency of the conventional local oscillator, it is technically easy to realize. In particular, a local oscillator using a dielectric resonator can easily realize a local oscillation signal with small phase noise.

(3) Since the interval between the image signal frequency and the RF signal frequency can be widened, it is possible to prevent the conversion loss characteristic of the mixer from deteriorating by performing image recovery processing on the image signal generated in the mixer in the preceding stage. In particular, the mixer
This image recovery process is an effective means in the case of a single-ended type that can be configured with one diode.

(4) Since the interval between the RF signal frequency and the frequency of the local oscillator can be widened, it becomes easy to suppress the leakage of the local oscillation signal from the RF input terminal. In particular, even if only the RF input terminal is a waveguide, it is possible to suppress leakage of a local oscillation signal from the RF input terminal by utilizing the high pass filter characteristic of the waveguide.

(5) IF the frequency difference between the two local oscillators
Select higher than the maximum frequency of the output signal or IF
By selecting a frequency lower than the minimum frequency of the output signal, even if the local oscillator signal of the local oscillator is frequency-converted by the mixer in the subsequent stage and is output to the IF output terminal as an interference signal, the interference signal is within the frequency band of the IF output signal. Can be prevented.

(6) In the second and sixth aspects of the invention, an image rejection type mixer is used as the mixer in the latter stage, and the image rejection band of the mixer is realized in a band wider than the frequency band of the image signal, and the local part in the preceding stage is used. By setting the frequency of the oscillator within the image rejection band of the mixer at the rear stage, the local oscillation signal of the local oscillator at the front stage is frequency-converted by the mixer at the rear stage and output as an interference signal to the IF output terminal. Can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram of a frequency conversion device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a frequency conversion device according to another embodiment of the present invention.

FIG. 3 is a block diagram of a conventional frequency conversion device.

[Explanation of symbols]

 11,21 RF amplifier 12,17,22,27 Mixer 13,18,23,28 Local oscillator 14,19,24,29 IF amplifier 15,25 RF input terminal 16,26 IF output terminal

Claims (8)

[Claims] 1. A first local oscillator that outputs a local oscillation signal lower than a high frequency signal, and a first local oscillator that receives the local oscillation signal and the high frequency signal of the first local oscillator and converts the first local oscillator signal into a first intermediate frequency signal. A second local oscillator for outputting a local oscillation signal, a second local oscillator for inputting the local oscillation signal of the second local oscillator and a first intermediate frequency signal, and a second intermediate frequency signal for converting the second local frequency signal to a second intermediate frequency signal. The mixer, the first local oscillator and the second local oscillator so that a frequency difference between the first local oscillator and the second local oscillator is higher than a maximum frequency of the second intermediate frequency signal. A frequency conversion device characterized in that an oscillation frequency of an oscillator is set. 2. The second mixer is an image rejection type mixer, and the local oscillation frequency of the first local oscillator is arranged within an image rejection band of the image rejection type mixer. 2. The frequency conversion device according to claim 1, wherein the frequency of the local oscillator and the image rejection band of the image rejection mixer are set. 3. The oscillation frequencies of the first and second local oscillators are set so that the image frequency of the first mixer does not overlap with the frequency band of the second intermediate frequency signal. The frequency conversion device according to claim 1. 4. The frequency conversion device according to claim 1, wherein the frequency of the second local oscillator is set higher than the frequency of the first intermediate frequency signal. 5. A first local oscillator which outputs a local oscillation signal lower than a high frequency signal, and a first local oscillator which receives the local oscillation signal and the high frequency signal of the first local oscillator and converts the first local oscillator signal into a first intermediate frequency signal. A second local oscillator for outputting a local oscillation signal, a second local oscillator for inputting the local oscillation signal of the second local oscillator and a first intermediate frequency signal, and a second intermediate frequency signal for converting the second local frequency signal to a second intermediate frequency signal. A mixer of the first local oscillator so that the frequency difference between the first local oscillator and the second local oscillator is lower than the minimum frequency of the second intermediate frequency signal. Frequency and the second
2. A frequency conversion device characterized in that the frequency of the local oscillator is set. 6. The second mixer is an image rejection type mixer, and the local oscillation frequency of the first local oscillator is arranged within an image rejection band of the image rejection type mixer. 6. The frequency conversion device according to claim 5, wherein the frequency of the local oscillator 1 and the image rejection band of the image rejection mixer are set. 7. The oscillation frequencies of the first and second local oscillators are set so that the image frequency of the first mixer does not overlap with the frequency band of the second intermediate frequency signal. The frequency conversion device according to claim 5. 8. The frequency converter according to claim 5, wherein the frequency of the second local oscillator is set higher than the frequency of the first intermediate frequency signal.