JPH059015U - Frequency converter - Google Patents

Abstract

(57) [Summary] [Object] To provide a frequency converter that suppresses an image signal component generated during frequency conversion and suppresses a leakage signal component of a local oscillation signal. [Structure] The phase is π / with respect to the modulation signal and the local oscillation signal.
First mixer means for mixing the first delayed local oscillation signal delayed by two and outputting the first signal, and a delayed modulation signal having a phase delayed by π / 2 with respect to the modulation signal and the local oscillation signal. Second mixer means for mixing and outputting a second signal, means for generating a second delayed local oscillation signal whose phase is delayed by 5π / 4 with respect to the local oscillation signal, and this second delayed local oscillation Means for adjusting the level of the signal and outputting a third signal;
The first to third signals are input and a combined signal is output, and the leakage signal components of the local oscillation signal and the first delayed local oscillation signal are suppressed by adjusting the level of the third signal. To do.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a frequency converter that frequency-converts a modulated signal into a radio frequency band signal.

[0002]

[Prior Art]

 FIG. 3 is a block diagram showing a conventional frequency converter, 1 is a modulator, 2 is a mixer, 3 is a local oscillator and a band limiting filter 4.

The modulation signal from the modulator 1 and the local oscillation signal from the local oscillator 3 are input to the mixer 2, and a signal component corresponding to the product of these signals is output. At this time, an image frequency component is generated in addition to the desired signal. In order to remove this, the band limiting filter 4 is connected to the latter stage of the mixer 2.

In the frequency converter having such a configuration, the band limiting filter 4 needs to pass a signal having a desired signal frequency and sufficiently attenuate the image frequency signal. However, the lower the output frequency of the modulator 1 with respect to the output frequency of the local oscillator 3, the closer the frequency of the desired signal and the image frequency are to each other, so that the band limiting filter 4 satisfying the above characteristics can be realized. It will be difficult.

As a method of suppressing the image frequency signal without using the band limiting filter 4, a frequency converter having a configuration as shown in FIG. 4 can be considered.

This frequency converter comprises a local oscillator 7, −π / 2 phase shifters 8 and 9, mixers 10 and 11, and a combiner 12. The output signal from the modulator 1 is input to the mixer 11 and also to the mixer 10 via the −π / 2 phase shifter 8. The local oscillation output signal from the local oscillator 7 is input to the mixer 10 and also to the mixer 10 via the -π / 2 phase shifter 9. The output signals from the mixers 10 and 11 are input to the synthesizer 12, and the added signals are output.

[0007] represents a local oscillation signal from the modulation signal and local oscillator 7 from the modulator 1 to the following equation, [modulated signal] A (t) cos (ω c t + ψ (t)) [ local oscillation signal] Bcosω _l t These signals and the delayed signals from the π / 2 phase shifters 8 and 9 are input into the mixers 10 and 11, respectively, and the output signals are as follows.

[0008] Mixer 10 Output] A (t) cos (ω c t + ψ (t) -π / 2) × Bcosω l t = (B · A (t) / 2) {sin ((ω c + ω l) t + ψ (t)) + sin (( ω c -ω l) t + ψ (t))} (1) [ mixer 11 output] A (t) cos (ω c t + ψ (t)) × Bcos (ω l t-π / 2 ) = (B · A (t) / 2) {sin ((ω _c + ω _l ) t + ψ (t)) −sin ((ω _c −ω _l ) t + ψ (t))} (2) Therefore, the mixer 10, When the output signal from the 11 added in combiner 12, (1) and (2), a (t) cos (ω c t + ψ (t) -π / 2) × Bcosω l t + a (t) cos ( _{ω c t + ψ (t)} ) × Bcos (ω l t-π / 2) = B · A (t) {sin ((ω c + ω l) t + ψ (t))} , and the image signal component [sin ((ω _c− ω _l ) t + φ (t))}] is canceled and only the desired signal B · A (t) {sin ((ω _c + ω _l ) t + φ (t))} is extracted.

[0009]

[Problems to be solved by the device]

 However, since the local oscillation signal is actually leaked and output from the mixers 10 and 11, the output signal of the frequency converter 6 is expressed by the following equation.

B · A (t) {sin ((ω _c + ω _l ) t + ψ (t))} + ΔB′cos (ω _l t) + ΔB ″ cos (ω _l t−π / 2) (3) (3 2), the second term is the leak signal component from the mixer 10, and the third term is the leak signal component from the mixer 11.

An object of the present invention is to prevent such a leak signal component of a local oscillation signal from being output.

[0012]

[Means for Solving the Problems]

 In view of the above points, the frequency converter of the present invention includes a modulation signal and a means for generating a delayed modulation signal whose phase is delayed by π / 2 with respect to the modulation signal, and a local oscillation means for generating a local oscillation signal. , A means for generating a first delayed local oscillation signal whose phase is delayed by π / 2 with respect to the local oscillation signal, and the modulation signal and the first delayed local oscillation signal are mixed to generate a first signal. First mixer means for outputting, second mixer means for mixing the delayed modulation signal and the local oscillation signal and outputting a second signal, and at least the first and second signals described above are inputted. And a means for generating a predetermined signal by combining a plurality of input signals, a means for generating a second delayed local oscillation signal whose phase is delayed by 5π / 4 with respect to the local oscillation signal, and the local portion. The synthesizing means for the oscillation signal and the first delayed local oscillation signal In which the leakage signal components of by adjusting the signal level of the second delay local oscillator signal to be suppressed and means for input to the combining means.

[0013]

[Action]

 With the above configuration, the second delayed local oscillation signal whose phase is delayed by 5π / 4 with respect to the local oscillation signal is generated, and the level of the signal is adjusted to adjust the local oscillation signal and the first delayed local oscillation signal. The leakage signal component to the synthesizing means of the above is suppressed.

[0014]

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a frequency converter of the present invention. The same parts as those in the conventional example of FIG. 4 are designated by the same reference numerals and the description thereof will be omitted. The difference from the frequency converter in FIG. 4 is that the frequency converter shown in FIG. 4 includes a −3π / 4 phase shifter 13 and a variable attenuator 14. These are connected in series between the −π / 2 phase shifter 9 and the combiner 12. The -π / 2 phase shifter 9 and the -3π / 4 phase shifter 13 constitute a means for generating a second delayed local oscillation signal whose phase is delayed by 5π / 4 with respect to the local oscillation signal.

Then, the local oscillation signal output from the local oscillator 7 is delayed by π / 2 phase by the -π / 2 phase shifter 9, and further delayed by 3π / 4 by the -3π / 4 phase shifter 13. The level of the local oscillation signal delayed by 5π / 4 is adjusted by the variable attenuator 14 and input to the synthesizer 12. The level of this input signal is adjusted so that the leak signal of the local oscillation signal from the mixers 10, 11 is canceled in the combiner 12.

Here, assuming that the leak signal components from the mixers 10 and 11 are equal (ΔB ′ = ΔB ″), the equation (3) becomes the following equation.

B · A (t) {sin ((ω _c + ω _l ) t + ψ (t))} + ΔB sin (ω _l t + π / 4) (4) where ΔB / √2 = ΔB ′ = ΔB ″ The -π / 2 phase shifter 9 delays the phase of the output signal of the local oscillator 7 by π / 2, and the -3π / 4 phase shifter 13 further delays the phase by 3π / 4, and the variable attenuator 14 When the signal level is adjusted to generate a signal component shown in the following equation, the second term of the equation (4) is canceled by the combiner 12.

ΔBsin (ω _l t−5π / 4) Therefore, only the desired signal [B · A (t) {sin ((ω _c + ω _l ) t + ψ (t))}] is output from the combiner 12. Will be.

Even if the leak signal components from the mixers 10 and 11 are different from each other, it is possible to reduce the output of the leak signal component from the combiner 12.

FIG. 2 is a block diagram showing another embodiment of the present invention, which is an example of frequency conversion of a digital modulation signal. In this case, since the digital modulator 15 generates the modulation signal S2 and the modulation signal S1 whose phase is delayed by π / 2, the −π / 2 phase shifter 8 is omitted as compared with the embodiment of FIG. can do.

The second delayed local oscillation signal generating means delays the phase of the local oscillation signal from the local oscillator 7 by 5π / 4 and includes a −5π / 4 phase shifter between the local oscillator 7 and the variable attenuator 14. It goes without saying that they may be connected and configured.

[0023]

[Effect of the device]

 As described above, according to the present invention, it is possible to suppress the image signal component generated at the time of frequency conversion and also suppress the leakage signal component of the local oscillation signal.

[Brief description of drawings]

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

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

FIG. 3 is a block diagram of a conventional frequency converter.

FIG. 4 is a block diagram of an improved conventional frequency converter.

[Explanation of symbols]

 1 Modulator 7 Local Oscillator 8 -π / 2 Phaser 9 -π / 2 Phaser 10 Mixer 11 Mixer 12 Combiner 13 -3π / 4 Phaser 14 Variable Attenuator

Claims (1)

Claims for utility model registration: 1. Modulation signal and means for generating a delayed modulation signal whose phase is delayed by π / 2 with respect to the modulation signal; local oscillation means for generating a local oscillation signal; Means for generating a first delayed local oscillation signal whose phase is delayed by π / 2 with respect to the local oscillation signal, and the modulation signal and the first delayed local oscillation signal are mixed to output a first signal. A first mixer means, a second mixer means for mixing the delay modulation signal and the local oscillation signal and outputting a second signal, and at least the first and second signals are input, and a plurality of Combining means for combining the input signals and outputting a predetermined signal; means for generating a second delayed local oscillation signal having a phase delayed by 5π / 4 with respect to the local oscillation signal; Leakage of the delayed local oscillation signal of 1 to the synthesizing means Frequency converter and means for input to the combining means adjusts the signal level of the second delayed local oscillation signal so that the signal component is suppressed.