JP5043142B2 - Frequency conversion device and frequency conversion method - Google Patents

Description

  The present invention relates to a frequency conversion device and a frequency conversion method, and more particularly to a frequency conversion device and a frequency conversion method that reduce noise caused by a local signal.

  In order to perform frequency conversion, a frequency conversion device that distributes an input signal into a plurality of frequencies and converts the frequency has been proposed (for example, see Patent Document 1). The frequency conversion device of Patent Literature 1 distributes an input analog signal into a plurality of signals, and frequency-converts the distributed signals using different local signals. Then, the frequency-converted signals are combined to reconstruct the input analog signal data. Thereby, the frequency converter of patent document 1 frequency-converts the high frequency wideband input signal to a low frequency in real time.

JP 2009-246958 A

  During frequency conversion, noise due to local signals may occur. However, in Patent Document 1, since this noise is not taken into consideration, there is a case where noise due to a local signal is mixed in data to be reconstructed.

  Accordingly, an object of the present invention is to provide a frequency conversion device and a frequency conversion method that reduce noise caused by a local signal.

  In order to achieve the above object, the frequency conversion apparatus and frequency conversion method of the present invention use a local signal that is divided into a plurality of signals and independently divides each signal.

Specifically, the frequency converter of the present invention includes a signal distributor (21) that distributes an input signal in N (where N is a positive integer), an intermediate frequency after frequency conversion, and the approximate center of the input signal. A local signal generator (22) for generating a local signal having a frequency M times the frequency difference (where M is a positive integer), and a local signal distribution for distributing the local signal from the local signal generator into N a vessel (11), said by M divider each local signal independent from the local signal distributor, N pieces of the frequency divider for generating a local signal in phase with the noise having no correlation with each other (12 1 to 12-N) and each input signal from the signal distributor is mixed with each local signal from each of the N frequency dividers, and N pieces of intermediate frequency signals obtained by the mixing are output. Frequency converter (23-1 Comprises a 23-N), the N signal combiner for combining together the phase of the intermediate frequency signal from the frequency converter (25), the.

  Since the local signal generator and the frequency converter are provided, the frequency conversion of the input signal can be performed. Since each local signal from the local signal distributor is independently divided by N frequency dividers, a plurality of in-phase local signals having uncorrelated noise can be generated. Further, the phase noise of the local signal can be reduced to 1 / M by the effect of frequency division. As a result, the noise of each local signal input to the frequency converter becomes thermal noise having no correlation and phase noise reduced to 1 / M. Therefore, the frequency conversion device of the present invention can reduce noise caused by local signals in the output signal synthesized by the signal synthesizer.

  In addition, since the signal distributor, the N frequency converters, and the signal synthesizer are provided, the signal level input to each frequency converter can be reduced, resulting from the input level output from each frequency converter. It is also possible to reduce distortion components. Therefore, the frequency converter of the present invention can improve the signal-to-noise ratio of the signal when the signal synthesizer is synthesized.

Specifically, the frequency conversion method of the present invention distributes the input signal N (where N is a positive integer), and M times the difference between the intermediate frequency after frequency conversion and the approximate center frequency of the input signal. (However, M is a positive integer.) A local signal having a frequency of N is generated and divided into N, and then divided by M independently to generate in- phase local signals having uncorrelated noises. Each of the distributed input signals and each of the M-divided local signals are mixed to generate N intermediate frequency signals , and the phases of the N intermediate frequency signals are combined and combined.

  Since the input signal and each of the M-frequency-divided local signals are mixed to generate N intermediate frequency signals, and the N intermediate frequency signals are synthesized, frequency conversion of the input signal can be performed. Since the local signal is divided by M, the phase noise of the local signal can be reduced to 1 / M. In addition, since the local signal is divided into M after being distributed N times, a plurality of in-phase local signals having uncorrelated noise can be generated. As a result, the noise of each local signal becomes thermal noise having no correlation and phase noise reduced to 1 / M. Therefore, the frequency conversion method of the present invention can reduce noise caused by local signals in the output signal synthesized by the signal synthesizer.

  Further, since the input signal is divided into N and N intermediate frequency signals are synthesized, the input level to each frequency converter can be reduced, and the distortion component caused by the input level output from each frequency converter Can also be reduced. Therefore, the frequency conversion method of the present invention can improve the signal-to-noise ratio of the signal when the signal synthesizer is synthesized.

  ADVANTAGE OF THE INVENTION According to this invention, the frequency converter and frequency conversion method which reduce the noise resulting from a local signal can be provided.

An example of the frequency converter which concerns on this embodiment is shown. An example of the input signal RF is shown. An example of the third-order distortion generated in the frequency converter is shown.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

  FIG. 1 shows an example of a frequency conversion device according to this embodiment. The frequency converter 101 includes a signal distributor 21, N (where N is a positive integer) frequency converters 23-1 to 23 -N, and ADCs (Analog to Digital Converters) 24-1 to 24-. N, a signal synthesizer 25, a local signal generator 22, a local signal distributor 11, frequency dividers 12-1 to 12-N, and amplifiers 13-1 to 13-N.

The frequency conversion device 101 executes the frequency conversion method according to the present embodiment. In the frequency conversion method according to this embodiment, the signal distributor 21 distributes the input signal RF N (where N is a positive integer), and the local signal generator 22 M times the frequency f _LO (where M Is a positive integer), and after the local signal distributor 11 distributes N, the frequency dividers 12-1 to 12-N independently divide the frequency into M and the frequency converter 23-1. -23-N mixes the N-divided input signals B-1 to BN and the M-divided local signals L-1 to L-N, respectively, so that N intermediate frequency signals IF-1 to IF- IF-N is generated, and the signal synthesizer 25 synthesizes the N intermediate frequency signals IF-1 to IF-N. Details will be described below.

The signal distributor 21 shown in FIG. 1 distributes the input signal RF into N, and outputs the input signals B-1 to BN to the frequency converters 23-1 to 23-N. The frequency converters 23-1 to 23-N mix the input signals B-1 to B-N from the signal distributor 21 with the local signals L-1 to L-N of the frequency f _LO , respectively. The obtained intermediate frequency signals IF-1 to IF-N are output. The ADCs 24-1 to 24-N convert the intermediate frequency signals IF-1 to IF-N from the frequency converters 23-1 to 23-N into digital signals D-1 to DN. As a result, the input signals B-1 to BN are converted into digital signals D-1 to DN, respectively.

  For example, the frequency converter 23-1 mixes the input signal B-1 with the local signal L-1, and outputs an intermediate frequency signal IF-1 obtained by the mixing. The ADC 24-1 converts each intermediate frequency signal IF-1 from the frequency converter 23-1 into a digital signal D-1. Thereby, the input signal B-1 is converted into a digital signal D-1. The same applies to the input signals B-2 to B-N.

FIG. 2 shows an example of the input signal RF. Since the signal distributor 21 distributes the input signal RF into N, the signal levels of the input signals B-1 to BN become 1 / N of the input signal RF. The frequency f _Lo is determined by the difference (f _IF −f _RF ) between the intermediate frequency f _IF after frequency conversion and the approximate center frequency f _RF of the input signal RF. Since the frequency converters 23-1 to 23-N are mixed with the local signals L-1 to L-N having the frequency f _LO , the frequency band of the input signals B-1 to B-N is shifted by the frequency f _LO. The frequency signals IF-1 to IF-N can be converted. Since the ADCs 24-1 to 24-N convert the intermediate frequency signals IF-1 to IF-N into the digital signals D-1 to DN, the intermediate frequency signals IF-1 to IF-N are generated for each frequency. It can be converted into sampled digital signals D-1 to DN.

  Here, if the signal level of the input signal RF is too low, the input signal RF and noise cannot be separated. However, when the signal level of the input signal RF is increased, the third-order distortion generated in the frequency converters 23-1 to 23-N increases.

  FIG. 3 shows an example of the third-order distortion generated in the frequency converter. The third-order distortion generated in the frequency converter varies depending on the input signal level. The higher the input signal level, the greater the third-order distortion generated in the frequency converter.

  Therefore, the frequency converter 101 distributes the input signal RF into N using the signal distributor 21 and reduces the signal level at each frequency of the input signals B-1 to BN to 1 / N of the input signal RF. ing. Thereby, the frequency converter 101 can reduce the third-order distortion generated in the frequency converters 23-1 to 23-N. The value of N is 2 or 4, for example.

  The signal synthesizer 25 shown in FIG. 1 synthesizes the digital signals D-1 to DN from the ADCs 24-1 to 24-N. For example, all of the digital signal D-1 to the digital signal DN are synthesized so that the same frequencies of the intermediate frequency signals IF-1 to IF-N are synthesized. At this time, the phases of the digital signals D-1 to DN are matched. Thereby, a signal obtained by converting the input signal RF shown in FIG. 2 into an intermediate frequency can be constructed.

Local signal generator shown in FIG. 1 22 generates a local signal LO having a M times the frequency of the frequency f _Lo. The local signal distributor 11 distributes the local signal LO from the local signal generator 22 into N. The frequency dividers 12-1 to 12 -N independently divide each local signal LO from the local signal distributor 11 by M. The amplifiers 13-1 to 13-N amplify the local signals from the frequency dividers 12-1 to 12-N. Thereby, the amplifiers 13-1 to 13-N output the local signals L-1 to L-N having the frequency component of the frequency f _Lo to the frequency converters 23-1 to 23-N.

For example, a local signal generator 22 generates a local signal LO having a M times the frequency of the frequency f _Lo. The frequency divider 12-1 divides one of the local signals LO from the local signal distributor 11 by M. The amplifier 13-1 amplifies the local signal L-1 from the frequency divider 12-1. As a result, the local signal L-1 having the frequency f _LO is output from the amplifier 13-1 to the frequency converter 23-1. The same applies to the local signals L-2 to L-N.

Here, the input signal RF side of the noise is zero, when the noise of the local signal LO and _{N L,} noise output from the frequency converter 23-1 to 23-N becomes _N L -IL. Here, IL is usually 20 dB to 30 dB in local IF (Intermediate Frequency) isolation. In this case, in order to reduce the output, that is, the noise on the IF side, it is necessary to reduce the noise of the local signal LO, but this is limited by the performance and specifications of the local signal generator 22.

  In this embodiment, since the local signal LO is independently M-divided, the influence of noise caused by the performance and specifications of the local signal generator 22 can be eliminated. Further, the phase noise of the local signal LO can be reduced to 1 / M by the effect of frequency division. As a result, the noises of the local signals L-1 to LN input to the frequency converters 23-1 to 23-N become thermal noise having no correlation and phase noise reduced to 1 / M. . Therefore, noise caused by the local signal LO in the output signal synthesized by the signal synthesizer 25 can be reduced.

  The value of M is 2 or 4, for example, and is determined by the number to be divided. The value of M is preferably 4 or more. Further, the frequency dividers 12-1 to 12-N may be either analog or digital in order to achieve the operation and effect of the present invention as long as the local signal LO can be divided. If digital, the frequency dividers 12-1 to 12-N can be configured using a counter.

  Since the present invention can be applied to a frequency converter, it can be used in the information communication industry.

11: Local signal distributors 12-1, 12-2, 12-N: Frequency dividers 13-1, 13-2, 13-N: Amplifier 21: Signal distributor 22: Local signal generators 23-1, 23 -2, 23-N: Frequency converters 24-1, 24-2, 24-N: ADC
25: Signal synthesizer
101: Frequency converter

Claims (2)

A signal distributor (21) for distributing the input signal N (where N is a positive integer);
A local signal generator (22) for generating a local signal having a frequency M times the difference between the intermediate frequency after frequency conversion and the substantially center frequency of the input signal (where M is a positive integer);
A local signal distributor (11) for distributing N local signals from the local signal generator;
Wherein by M divider each local signal independent from the local signal distributor, N pieces of the frequency divider for generating a local signal in phase with the noise having no correlation with each other (12-1 to 12-N) When,
Each of the input signals from the signal distributor is mixed with each of the local signals from the N frequency dividers, and N frequency converters (23-1 to 23-1) that output intermediate frequency signals obtained by the mixing. 23-N),
A signal synthesizer (25) for synthesizing the phases of the intermediate frequency signals from the N frequency converters;
A frequency conversion device comprising: The input signal is distributed N (where N is a positive integer), and the frequency is M times the difference between the intermediate frequency after frequency conversion and the approximate center frequency of the input signal (where M is a positive integer). Local signals having in- phase noise with no correlation to each other are generated by generating N local signals and performing N division independently, and each of the input signals after the N division and the M divided divisions are generated . A frequency conversion method for generating N intermediate frequency signals by mixing each local signal and combining the N intermediate frequency signals in phase .

Images