JPH07202742A - 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 (21.4-22.0GHz) 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 (9.925-10.525GHz) of 10GHz band by a mixer 12 and a local oscillator 13 (11.475GHz) and amplified by an IF amplifier 14. Then a mixer 17 and a local oscillator 13 are used to frequency-convert the amplified signal into an IF output signal (0.95-1.55GHz) of 1GHz band again and the result is outputted from an IF output terminal 16. The frequency of the local oscillator 13 is selected higher than the frequency of the IF 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. 4 shows the configuration of a conventional frequency converter for 21 GHz band satellite broadcasting. The frequency converter 40 for the 21 GHz band has a high frequency (hereinafter referred to as RF) input terminal 41 with RF
The mixer 43 is connected via the amplifier 42. Mixer 4
3, a local oscillator 44 with 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 the output is amplified by the IF amplifier 45. Here, the frequency of the IF output signal output from the IF output terminal 46 of the frequency conversion device 40 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).
Only 0.95 GHz apart from (Hz), and the ratio (f _R −) in which the local frequency is arranged apart from the RF signal frequency.
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 41. 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 43 is easily deteriorated due to the insufficient image suppression ratio of the mixer 43.

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.

Further, when a 1 GHz band IF output signal composed of a plurality of carrier signals having different frequencies for each channel is selected and converted into a low intermediate frequency signal having a constant frequency (eg 403 MHz), Since it is necessary to perform frequency conversion with a local oscillator having a frequency higher than the IF output signal (0.95 to 1.55 GHz) of the frequency conversion device 40, the spectrum of a low intermediate frequency signal having a constant frequency (403 MHz) is RF.
It becomes the spectrum that the signal spectrum is inverted.
Therefore, there is a problem that the modulated signal of the inverted spectrum must be demodulated.

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 41 of the frequency converter of the 21 GHz band, and also causes image interference. An object of the present invention is to provide a frequency conversion device that is strong and has a non-inverted spectrum after tuning.

[0011]

According to a first aspect of the present invention, a local oscillator that outputs a local oscillation signal lower than a high frequency signal, a local oscillation signal of the local oscillator and a high frequency signal are input, and a first intermediate frequency is input. A first mixer for converting to a signal, and a second mixer for inputting outputs of the first intermediate frequency signal and the local oscillation signal and converting to a second intermediate frequency signal lower than the first intermediate frequency signal; , And the oscillation frequency of the local oscillator is set higher than the frequency of the first intermediate frequency signal.

Further, the invention according to claim 2 is such that a local oscillator which outputs a local oscillation signal lower than a high frequency signal, and a local oscillation signal of the local oscillator and a high frequency signal are input and are converted into a first intermediate frequency signal. And a second mixer for inputting the first intermediate frequency signal and the local oscillation signal of the local oscillator extracted from the first mixer and converting the second intermediate frequency signal into a second intermediate frequency signal. The oscillation frequency of the local oscillator is set higher than the frequency of the first intermediate frequency signal, and the invention of claim 3 is characterized in that, in addition to this, the local oscillation signal of the local oscillator is passed through. 1 band pass filter, an intermediate frequency amplifier for amplifying the first intermediate frequency signal and the local oscillation signal of the local oscillator that has passed through the first band pass filter, and the local oscillation signal of the local oscillator among the outputs of the intermediate frequency amplifier To A second band-pass filter for passing and outputting a second intermediate frequency signal to the second mixer, and a third band-pass filter for passing a first intermediate frequency signal of the output of the intermediate frequency amplifier and outputting the second intermediate frequency signal to the second mixer. And are provided.

[0013]

According to the invention of claim 1 of the present application having such a feature, the high frequency signal is converted into the first intermediate frequency signal by the local oscillator and the first mixer, and the local oscillator and the second oscillator are further converted. It is converted into the second intermediate frequency signal by the mixer. The local oscillation frequency is set so that the oscillation frequency of the local oscillator is higher than the maximum frequency of the first intermediate frequency signal.

According to a second aspect of the present invention, the high frequency signal is frequency-converted into a first intermediate frequency signal by the local oscillator and the first mixer, and the local oscillation signal leaking from the first mixer and the first intermediate signal are leaked. By inputting the frequency signal and the second mixer into the second mixer, the first intermediate frequency signal is converted into the second intermediate frequency signal. According to the third aspect of the invention, the output of the local oscillator is input to the intermediate frequency amplifier together with the first intermediate frequency signal through the first band pass filter and is amplified. Further, the output of the intermediate frequency amplifier is used as the local oscillation signal and the first
The intermediate frequency signals are separated by the second and third band pass filters and output to the second mixer. The oscillation frequency of the local oscillator is set to be higher than the maximum frequency of the first intermediate frequency signal. This makes it possible to set the image signal frequency as well as the local signal frequency to a position far away from the RF signal frequency.
It is possible to easily realize a frequency conversion device that is strong against leakage of local signals and strong against image interference.

[0015]

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 1
A local oscillator 13 of 1.475 GHz is connected. The mixer 12 inputs the input signal to the first IF signal (9.925 band) in the 10 GHz band.
Up to 10.525 GHz), the output of which is amplified by the first IF amplifier 14 and the second mixer 1
Input to 7. The output of the local oscillator 11 is branched and given to the mixer 17. The mixer 17 converts the first IF signal into the IF output signal (0.95) which is the second IF signal in the 1 GHz band.
Frequency conversion to 1.55 GHz) again. The output is amplified by the IF amplifier 19 and output to the IF output terminal 16.

Here, the frequency of the local oscillation signal of the local oscillator 13 (11.475 GHz) is the frequency of the first IF signal (9.925 GHz).
~ 10.525 GHz).

The frequency conversion device according to the first embodiment has the following effects. (1) Image signal frequency of mixer 12 (0.95 to 1.55G
Since (Hz) is completely distant from the RF signal frequency (21.4 to 22.0 GHz), the structure of the image signal blocking filter is 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. Moreover, even in the mixer 17, the image signal frequency (12.425 to 13.025 GHz) is the frequency of the IF signal (9.
925 to 10.525 GHz) is relatively distant. Therefore, the configuration of the image signal blocking filter becomes relatively easy,
Since the image signal processing of the mixer 17 is also facilitated, the conversion loss characteristic of the mixer 17 can be improved.

(2) Since the frequency of the local oscillator 13 is far away from the RF signal frequency, the construction of the local oscillation signal blocking filter becomes easy and the leakage of the local oscillation signal from the RF input terminal 15 can be suppressed. Will be easier.

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.

(3) The frequency of the local oscillator 13 of the frequency converter is the frequency of the conventional local oscillator of FIG. 4 (20.45 G
(Hz), which is about 1/2 that of 11.25 GHz, which is relatively easy to realize technically, and is technically easy to realize as a frequency conversion device. In particular, a local oscillator using a dielectric resonator can easily realize a local oscillation signal with small phase noise.

(4) Frequency of the local oscillator 13 (11.475G
Hz) is the frequency of the first IF signal (9.925 to 10.525 GHz)
Therefore, the spectrum of the second IF signal output to the IF output terminal 16 is an inverted spectrum of the RF signal. Therefore, when a second IF signal composed of signals of a plurality of carriers is selected and frequency-converted into an IF signal of 403 MHz as in a 12 GHz band satellite broadcasting reception system, the spectrum is inverted again and the RF signal The same spectrum as the spectrum is obtained. Therefore 403 M
Since it becomes possible to directly demodulate the modulated signal of the non-inverted spectrum from the IF signal of Hz, even if the modulated signal is not preferable to be demodulated from the modulated signal of the inverted spectrum, the frequency conversion need not be performed again. Good. Moreover, 403
Even when demodulating the modulation frequency at a frequency lower than MHZ (for example, 140 MHZ), frequency conversion is possible without inverting the spectrum.

FIG. 2 is a block diagram of a frequency converter according to a second embodiment of the present invention. In this embodiment, the R of 21 GHz (21.4 to 22.0 GHz) input from the RF input terminal 25 is used.
The F signal is amplified by the RF amplifier 21, and the mixer 2
Entered in 2. A local oscillator 23 (11.475 GHz) that oscillates a frequency of 11.475 GHz, for example, is connected to the mixer 22, and the input signal is the first IF signal (9.
925 to 10.525 GHz). The output is amplified by the IF amplifier 24 and input to the mixer 27. The mixer 27 has a first amplifier amplified by the IF amplifier 24.
The local oscillation signal of 11.475 GHz leaked to the output terminal 28 of the mixer 22 is also amplified by the IF amplifier 24, and these are added to the mixer 27. Therefore mixer 2
In No. 7, the input signal is the second IF output signal of 1 GHz band (0.95
The frequency can be converted again to ~ 1.55 GHz). Second
The IF output signal of is amplified by the IF amplifier 29 and output from the IF output terminal 26. Here, the IF output signal frequency of the mixer 27 is I of the frequency converter for satellite broadcasting of 12 GHz.
0.95 to 1.55 GHz is selected to match the F output signal frequency. Moreover, the first frequency (1
1.475 GHz is the frequency of the IF signal (9.925 to 10.525 GHz
Since it is selected higher than z), the second IF output signal has an inversion spectrum of the RF signal.

In the second embodiment shown in FIG. 2, the oscillation signal of the local oscillator leaks as it is and is amplified as the output of the mixer 22 in addition to the first IF signal.
As shown in FIG. 3, the output of the local oscillator 23 is temporarily output to the distributor 3
1 is supplied to the mixer 22, a part of which is supplied to the mixer 22, and the other is supplied to the mixer 2 through a filter 32 which selectively passes the local oscillation signal.
It may be connected to the second output terminal 28 side. In this way, the IF amplifier 24 can simultaneously amplify the local oscillation signal in addition to the first IF signal in the 10 GHz band.

Further, the first IF signal (9.925 to 10.525 GHz) is passed through a bandpass filter 34 for passing the first IF signal and a bandpass filter 33 for selectively passing the local oscillation signal, respectively, for the signals passed through the IF amplifier 24. ) And a local oscillation signal (11.475 GHz), and this may be added to the mixer 27. In this way, the mixer 27 can surely convert the first IF signal into the second IF output signal.

The frequency conversion apparatus according to the second and third embodiments has the following effects. (1) Since a part of the local oscillator signal taken out to the output terminal 28 of the mixer 22 is amplified by the IF amplifier 24 and then input to the mixer 27 together with the first IF signal, the local oscillator 23
The output power level of 1 may be a power level that causes one mixer 23 to function. (2) Moreover, since the first IF signal and the local oscillation signal to be input to the mixer 27 can be input to the mixer 27 from the same terminal, the mixer having a very simplified circuit configuration can be realized. It will be easier.

[0026]

According to the present invention, the following effects can be obtained. (1) Since the distance between the frequency of the RF signal and the frequency of the image signal can be widened, a frequency converter that is strong against image interference can be configured.

(2) Since the interval between the RF signal frequency and the frequency of the local oscillator can be widened, it is possible to prevent the deterioration of the conversion loss characteristic of the mixer by performing image recovery processing on the image signal generated in the mixer at the preceding stage. Mixer especially mixer
This image recovery process is an effective means in the case of a single-ended type that can be configured with one diode. Moreover, since the frequency of the image signal of the mixer in the subsequent stage is relatively far from the frequency of the IF signal which is the input signal, the configuration of the image signal blocking filter becomes relatively easy and the image signal processing of the mixer becomes easy. Therefore, the deterioration of the conversion loss characteristics can be prevented even in the latter mixer.

(3) 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.

(4) 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 as a frequency converter. In particular, a local oscillator using a dielectric resonator can easily realize a local oscillation signal with small phase noise.

(5) Since the frequency of the local oscillator is higher than the frequency of the IF signal, the spectrum of the IF output signal is R
It is an inverted spectrum of the F signal. Therefore, when an IF output signal in the 1 GHz band composed of a plurality of carriers is tuned and frequency-converted to an IF signal lower than this (for example, 403 MHz), the spectrum is inverted again, and the spectrum is the same as that of the RF signal. An inverted spectrum is obtained. Therefore, it is possible to directly demodulate the modulated signal of the non-inverted spectrum from the IF signal of 403 MHz, so that it is not necessary to perform frequency conversion again even in the case of the modulated signal which is not preferable to be demodulated from the modulated signal of the inverted spectrum May be. Moreover, frequencies lower than 403 MHz (for example, 140 M
Even if you want to demodulate the modulated signal at (Hz), frequency conversion is possible without inverting the spectrum.

(6) In the inventions of claims 2 and 3, in addition to the above effects, in the mixer of the subsequent stage, a part of the local oscillation signal output to the output terminal of the mixer of the previous stage is amplified by the IF amplifier. After that, since it is input to the mixer in the subsequent stage together with the IF signal, the level of the local oscillation signal output to the output terminal of the mixer in the previous stage may be low. Therefore, it is possible to operate the two mixers with the output power level of the local oscillator being the level at which the one mixer in the preceding stage is operated.

[Brief description of drawings]

FIG. 1 is a block diagram of a frequency converter according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a frequency converter according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a frequency converter according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing an example of a conventional frequency conversion device.

[Explanation of symbols]

 11,21 RF amplifier 12,17,22,27 Mixer 13,23 Local oscillator 14,19,24,29 IF amplifier 15,25 RF input terminal 16,26 IF output terminal 31 Distributor 32,33,34 Band pass filter

Claims (3)

[Claims] 1. A local oscillator that outputs a local oscillation signal lower than a high-frequency signal; a first mixer that receives the local oscillation signal and the high-frequency signal of the local oscillator and converts the first oscillation signal into a first intermediate-frequency signal; A second mixer which receives the first intermediate frequency signal and the output of the local oscillation signal and converts the output to a second intermediate frequency signal lower than the first intermediate frequency signal; A frequency conversion device, wherein an oscillation frequency is set higher than a frequency of the first intermediate frequency signal. 2. A local oscillator that outputs a local oscillation signal lower than a high-frequency signal; a first mixer that receives the local oscillation signal and the high-frequency signal of the local oscillator and converts the first oscillation signal into a first intermediate-frequency signal; A second mixer for receiving a first intermediate frequency signal and a local oscillation signal of the local oscillator extracted from the first mixer and converting the signal to a second intermediate frequency signal; The oscillation frequency of the first intermediate frequency signal is set higher than the frequency of the first intermediate frequency signal. 3. A first band pass filter for passing a local oscillation signal of the local oscillator, and an amplifier for amplifying a local oscillation signal of the local oscillator that has passed the first intermediate frequency signal and the first band pass filter. A second intermediate frequency amplifier for transmitting a local oscillation signal of the local oscillator among the outputs of the intermediate frequency amplifier and outputting the second oscillation signal to the second mixer.
And a third band-pass filter for passing the first intermediate-frequency signal of the output of the intermediate-frequency amplifier and outputting it to the second mixer. Claim 2
The described frequency conversion device.