JP2009171238A - Communication equipment and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate the need of a filter bank when receiving a wide-band signal, and to eliminate the effect of a proximate interference wave. <P>SOLUTION: A wide-band reception signal is input to an LPF 1, and an output of the LPF 1 is up converted by a mixer 2. A signal passed through a BPF 4 is down converted into an IF signal of a frequency F1 by a mixer 5. A signal passed through a BPF 7 is down converted into an IF signal of a frequency F2 by a mixer 8. A signal passed through a BPF 10 is down converted into an IF signal of a frequency F3 by a mixer 11. In the BPF 7, a desired wave D is shifted to downside by down conversion by the mixer 5, so that an unwanted wave U1 can be suppressed. In the BPF 10, the desired wave D is shifted to upside by down conversion by the mixer 8, so that an unwanted wave U2 can be suppressed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a communication apparatus and communication method suitable for use in, for example, cognitive radio, and more specifically to a frequency converter and a frequency conversion method.

A single terminal recognizes and learns the radio wave usage environment around the user, and based on the result, adaptively switches / multiplexes to a wireless system that satisfies the bandwidth and QoS (Quality of Service) desired by the user Cognitive radio technology that performs wireless communication is attracting attention. Cognitive radio recognizes and recognizes the surrounding radio wave conditions for radio equipment such as terminals and base stations.
This is a method for improving the frequency utilization efficiency by selecting a bandwidth, a wireless method, or the like used for wireless communication according to the radio wave environment recognized and recognized by the wireless device itself. That is, an available wireless system is recognized for the presence of a signal using environment recognition technology such as sensing, and for the frequency band in which the presence of the signal is confirmed, the system is identified if possible. As a result of the environment recognition, adaptive switching / multiplexing is performed for a wireless system satisfying the bandwidth and QoS desired by the user based on the environment recognition result.

  In order to realize this cognitive radio, a high-frequency circuit (RF) capable of recognizing (sensing) the use environment of radio waves in a wide frequency band from VHF / UHF band to microwave band suitable for mobile communication / broadcasting. ) Part is required. A necessary condition for this RF section is that the signal can be down-converted while discriminating the radio communication system existing in each frequency band with as few parts as possible and a small device.

  An example of the RF unit is a filter bank. A filter bank prepares filters (band limiting filters) corresponding to a plurality of frequencies and bandwidths, and performs system discrimination by performing stepwise filtering. However, in order to correspond to the frequency band / bandwidth used by all wireless systems, it is necessary to prepare many filters, and the size of this filter is one major factor that determines the size of the RF section. It was. There is also a problem that it is not possible to easily add a new sensing frequency. Further, as described in Non-Patent Document 1 and Patent Document 1 below, a system using a variable filter has been proposed.

Kawai et al., “Bandpass filter with variable center frequency and bandwidth”, IEICE Tech. 73-76, July. 2007 JP 2007-31274 A

  The variable filter requires an advanced switching technology for switching the filter, and the current circuit technology still requires time.

  Accordingly, an object of the present invention is to provide a communication device and a communication method that can prevent an increase in circuit scale by using a large number of filter banks and that do not cause a problem of filter switching in the variable filter system. is there.

  That is, the present invention adaptively performs filtering in the process of up-converting (UC) a received signal in a wideband signal to a common frequency band by a variable synthesizer and then down-converting (DC) to an intermediate frequency band. A multiband frequency down conversion (MBFDC) method for extracting a signal is provided.

In order to solve the above-described problem, the present invention provides a low-pass filter to which a received signal of a desired frequency band including a plurality of signals having different frequency bands or wireless systems is supplied;
An up-conversion unit that up-converts the output of the low-pass filter to a common frequency;
It consists of an adaptive filtering unit connected to the up-conversion unit,
The adaptive filtering unit includes first and second down-conversion units, and first and second filters connected to the first and second down-conversion units, respectively.
Communication in which unnecessary signals existing in the upper frequency band and lower frequency band of the desired wave are removed by adjusting the local frequency of the local signal supplied to the first and second down-conversion units. Device.

  Preferably, a common third filter is inserted between the up-conversion unit and the first down-conversion unit of the adaptive filtering unit.

Preferably, if the desired frequency band is (f1 to f2), the cutoff frequency of the low-pass filter is f2, the stop band of the low-pass filter is fs, and the maximum bandwidth of the wireless system to be used is BWm. Is set to satisfy:
fx ≧ fs + (BWm) / 2
Furthermore, the frequency LO of the local signal supplied to the up-conversion unit is set so as to satisfy the following expression.
LO = fx + desired frequency

Preferably, in the adaptive filtering unit, when the maximum bandwidth of the wireless system to be used is BWm and the passbands of the first and second filters are BWp, the passband BWp is set to satisfy the following formula: .
BWp ≧ BWm
Furthermore, when the cutoff frequency of the first and second filters is fp, the stop band is fs, the minimum bandwidth of the wireless system to be used is BWn, and the channel interval is β, the following equation is set to be satisfied: Is done.
fp−fs ≧ β−BWn

The present invention performs left-right inversion by performing up-conversion on the output signal of the first filter when the passbands of the first and second filters are left-right asymmetric,
In this communication apparatus, the left and right inverted signals are supplied to the second filter to remove unnecessary signals.

The present invention includes a step of band-limiting a received signal in a desired frequency band including a plurality of signals having different frequency bands or wireless systems by a low-pass filter;
An up-conversion step for up-converting the output of the low-pass filter to a common frequency;
An adaptive filtering step on the upconverted signal,
The adaptive filtering step comprises first and second down-conversion steps, and first and second filtering steps for respective outputs of the first and second down-conversion steps;
By adjusting the local frequency of the local signal used in the first and second down-conversion steps, an unnecessary signal existing in each of the upper frequency band and the lower frequency band of the desired wave is removed. is there.

  In the present invention, up-conversion is performed on a desired signal band, and then filtering is performed in the up-converted frequency band. That is, a large number of band limiting filters are not required at the receiving input end. In addition, since the up-converted band is a high frequency, a small device is expected when performing operations such as filtering.

  Further, when up-conversion is performed, adjacent interference waves such as adjacent channel signals may be up-converted together. In the present invention, even when the interference wave signal is up-converted, the center frequency of the filter is fixed, and the center frequency of information is arbitrarily adjusted by the local frequency of frequency conversion so that unnecessary signals are removed. According to the present invention, it is possible to cut out only a necessary band.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The embodiment described below is a preferred specific example of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is particularly limited to the present invention in the following description. Unless otherwise stated, the present invention is not limited to these embodiments. The embodiment mainly includes (a) a part for shifting a desired frequency to a common frequency after receiving a wideband signal (Common center frequency Up-Conversion: CCFUC) part, and (b) A filtering unit adapted to adapt to a plurality of bandwidths (hereinafter referred to as an adaptive bandwidth filtering (ABF) unit).

  As shown in FIG. 1, a wideband received signal received by an antenna (not shown) and passed through a low noise power amplifier is input to a low pass filter (LPF) 1. The low-pass filter 1 removes components (signals outside the reception range) that exceed the maximum desired reception frequency in the entire system. An output signal of the low-pass filter 1 is supplied to a mixer (multiplier) 2. A local signal from the variable synthesizer 3 is input to the mixer 2. The frequency of the broadband signal is up-converted by the mixer 2 to the common frequency F0.

  Since the local signal has a different value required for a desired wireless system, the variable frequency synthesizer 3 is used to adjust the local frequency to a desired value. The low-pass filter 1 is provided to cope with the problem that aliasing occurs when mixing a received signal when another signal is present in a frequency band higher than the frequency band to be up-converted.

  In the subsequent stage of the mixer 2, band limitation is performed by a filter having a wide pass band, and adjacent channels and the like are removed by an adaptive band filtering unit in the subsequent stage. A band pass filter (BPF) 4 is connected to the output of the mixer 2. The signal that has passed through the bandpass filter 4 is supplied to the mixer 5. A local signal from the variable synthesizer 6 is supplied to the mixer 5 and is down-converted by the mixer 5 into an IF signal having an IF (Intermediate Frequency) frequency F1.

  The output signal of the mixer 5 is supplied to a band pass filter (BPF) 7. The signal that has passed through the bandpass filter 7 is supplied to the mixer 8. A local signal from the variable synthesizer 9 is supplied to the mixer 8 and is down-converted by the mixer 8 to an IF signal having an IF frequency F2.

  The output signal of the mixer 8 is supplied to a band pass filter (BPF) 10. The signal that has passed through the bandpass filter 10 is supplied to the mixer 11. A local signal from the variable synthesizer 12 is supplied to the mixer 11 and is down-converted by the mixer 11 into an IF signal having an IF frequency F3.

  An A / D converter 13 is connected to the mixer 11. The output signal of the mixer 11 is converted into a digital signal by the A / D converter 13. Although not shown, the digital signal output from the A / D converter 13 is processed by the digital signal processing unit. The contents of the processing of the digital signal processing unit are defined by software, and a software radio apparatus is configured. For example, a demodulator is configured by the digital signal processor, the degree of influence of the interference wave is determined from the demodulated output, and an appropriate radio system, frequency band, etc. are selected from the determination result.

  As shown in FIG. 2, as an example, the band to be used (band of received signal) is (300 MHz to 6 GHz), and the common frequency (shift frequency or up-conversion (UC) frequency) to be up-converted is, for example, 8 GHz. The

  As an example, the desired frequency in the broadband signal is set to 800 MHz, 2.4 GHz, and 5.2 GHz corresponding to three types of wireless systems. The local frequency LO of the local signal generated by the variable synthesizer 3 for these desired frequencies is (LO = UC frequency + 800 MHz), (LO = UC frequency + 2.4 GHz), and (LO = UC frequency + 5.2 GHz), respectively. Is set.

  The bandpass filter (BPF) 4 connected to the output of the mixer 2 has a band higher than the maximum bandwidth of the wireless system to be used so that the desired signal itself is not band-limited so that the up-converted frequency is 8 MHz as a center frequency. . The passband widths of the bandpass filter 4, the bandpass filter 7, and the bandpass filter 10 are equal to each other. These pass bandwidths are set corresponding to the wireless system.

  As shown in FIG. 3, in the passband width of the first-stage bandpass filter 4, for example, interference waves U1 and U2 that are unnecessary signals of adjacent channels exist above and below the band of the desired wave D having the center frequency F0. . In the next-stage band pass filter 7, the center frequency F 1 of the desired wave D is shifted downward within the pass bandwidth of the band pass filter 7 by down-conversion by the mixer 5. Since the jamming wave U1 is located below the pass band width of the bandpass filter 7, the jamming wave U1 can be suppressed. Further, in the next-stage bandpass filter 10, the center frequency F <b> 2 of the desired wave D is shifted upward within the passband width of the bandpass filter 10 by down-conversion by the mixer 8. Since the jamming wave U2 is located above the pass band width of the bandpass filter 10, the jamming wave U2 can be suppressed.

  In this way, the synthesizer value (local frequency) is varied for each wireless system having a different bandwidth, and unnecessary signals are pushed out of the passband by a plurality of filtering operations using a bandpass filter to limit the bandwidth. This makes it possible to perform filtering without using a filter bank.

  A parameter setting method such as the center frequency of the common frequency up-conversion for performing up-conversion according to the embodiment of the present invention will be described. The parameters corresponding to the step of shifting the desired signal in the wideband received signal to the same frequency and the step of filtering to adapt to a plurality of bandwidths will be described.

  As described above, when processing a wideband signal with a single radio, it is possible to process the subsequent stage as a single-band receiver by up-converting the desired frequency in the received signal to the same frequency. Become. However, since aliasing that occurs when mixing the received signal becomes a problem, it is necessary to set the center frequency of up-conversion so that aliasing does not occur.

  Assuming that the desired frequency range of the wireless system is f1 to f2, aliasing occurs when there is a frequency component greater than or equal to f2. For this reason, it is necessary to limit the band by the low-pass filter 1 so that there is no aliasing. FIG. 4 shows the settings of the frequencies f1, f2, and fs when the cutoff frequency of the low-pass filter 1 is f2 and the stop band is fs. If the maximum bandwidth of the wireless system to be used is set to BWm, no aliasing will occur if it is not affected by a signal having a frequency of f2 or higher and is within a range where fs and BWm do not overlap. FIG. 5 shows the relationship between the maximum bandwidth of the system and the optimum frequency. As shown in FIG. 5, the optimum frequency as the frequency to be shifted is fx, and the relational expression between fx and BWm is as shown in Expression (1).

fx ≧ fs + (BWm) / 2 (1)

  Next, a method for setting the local frequency LO will be described. A precaution in setting the local frequency LO is the removal of unnecessary frequency at the input stage of the mixer. When up-converting to the optimum frequency fx, it is necessary to apply the received signal to the mixer with a wide band, and as a result, the frequency components input to the mixer become very large. In addition, an operation occurs in which the mixer input, output, and local signal leak, and the frequency leaked from the output to the input is mixed again, and the frequency pattern generated further increases. In particular, since a harmonic signal is generated in accordance with the input frequency of the mixer, there is a high possibility that an unpredicted frequency component enters fx unless an unnecessary frequency is removed.

  FIG. 6 shows a signal pattern generated when the frequency input to the mixer is fr and the local signal is multiplied. Here, the larger the numerical values of n and m shown in FIG. 6, the smaller the power, and the farther apart on the frequency axis, the smaller the influence on other signals. In consideration of leakage of frequencies in the mixer and harmonic signals, setting of the local frequency LO is important when handling a wideband signal.

  In order to up-convert to the optimum frequency fx, there are two types of patterns in which fr + LO and fr−LO are adjusted to fx when n and m are 1 in FIG. 6, but when fr + LO is adjusted to fx, fr−LO becomes It exists in the original reception frequency band, and the influence of mixer leakage and harmonic signals increases. However, by adjusting fr-LO to fx, the fr + LO component becomes much higher on the frequency axis, and the influence on fx is eliminated.

  In consideration of the above, the setting condition of the local frequency LO when up-converting to the optimum frequency fx is expressed by Equation (2). It is optimal to perform the up-conversion shown in Equation (3) using the local frequency LO in Equation (2).

LO = fx + desired frequency (2)
(Fx + desired frequency) −desired frequency = fx (3)

  Next, a filter selection method of the adaptive band filtering (ABF) unit will be described. When processing received signals of a plurality of wireless systems, the bandwidth of each channel differs for each communication method. As shown in FIG. 3, in the adaptive band filtering unit, as shown in FIG. 3, the frequency of the information signal is controlled by a variable synthesizer, and an unnecessary signal is pushed out of the pass band of the filter. Other interference waves are reduced. It is necessary to consider the optimum values of parameters for realizing a filter having both a pass band that does not cut the desired wave and a steepness that does not allow the adjacent channel signal to enter, as parameters necessary for realizing this method. . Moreover, since a general filter is not completely left-right symmetric, it is desirable to take measures when the shape of the filter is left-right asymmetric.

  In one embodiment, filtering processing is performed using two bandpass filters 7 and 10. A condition suitable as the bandwidth of the bandpass filter depends on the maximum bandwidth of the wireless system to be used. The required conditions when the filter pass band is BWp and the maximum bandwidth of the wireless system to be used is BWm are shown in FIG.

  From FIG. 7, the closer the BWm is to BWp, the more closely the two filters overlap. Therefore, when BWm = BWp, it is the minimum condition for enabling filtering without attenuating the desired wave, and BWp must be more than that.

BWp ≧ BWm (4)

  The conditions necessary for sufficiently removing the signal of the adjacent channel depend on the width from the cutoff frequency of the filter to the stop band, the minimum bandwidth of the wireless system to be used, and the channel spacing. FIG. 8 shows conditions when the cutoff frequency of the filter is fp, the stop band is fs, the minimum bandwidth of the wireless system to be used is BWn, and the channel interval is β.

  As shown in FIG. 8, the minimum condition that the signal of the adjacent channel does not enter between fp and fs only needs to be separated by the difference between the minimum channel interval β and the bandwidth BWn of the wireless system to be used. Thus, the optimum condition for the distance on the frequency axis of the cut-off frequency and the stop band is expressed by Equation (5).

fp−fs ≧ β−BWn (5)

  Many general bandpass filters are asymmetrical, and it may be assumed that one side satisfies equation (5) but the other side does not satisfy equation (5). As a method of sufficiently restricting adjacent channels even when left-right asymmetry is used using a general-purpose filter, a method is adopted in which the IQ channel is inverted in the processing step and the adjacent channels on both sides are band-limited on one side of the filter. it can.

  FIG. 9 shows processing steps that can be considered when the bandpass filter is asymmetrical, and FIG. 10 shows an example of an inverted IQ channel. FIG. 10 shows an output when the input frequency is 140 MHz, the bandwidth is 10 MHz, and the local frequency LO of the local signal supplied to the mixer 8a is 980 MHz as an example.

  As shown in FIG. 9, the up-converted signal from the previous stage is band-limited by the band-pass filter 4 and supplied to the mixer 5. Down-converted by local signals from the mixer 5 and the variable synthesizer 6. The output signal of the mixer 5 is supplied to the band-pass filter 7, and the one-side adjacent signal (interference wave) is pushed out below the bandwidth of the band-pass filter 7, and the one-side adjacent signal is removed.

  The output of the bandpass filter 7 and the local signal from the variable synthesizer 9a are supplied to the mixer 8a, and up-conversion is performed. By this up-conversion, the left and right of the signal are inverted. The output signal of the mixer 8a is supplied to the mixer 8b via the bandpass filter 10a, and down-converted by the local signal from the variable synthesizer 9b. The output signal of the mixer 8b is supplied to the bandpass filter 10b, and the reverse side adjacent signal is removed. An A / D converter is connected to the band pass filter 10b.

  As shown in FIG. 10, when the input signal from the bandpass filter 7 is up-converted by the local frequency 980 MHz in the mixer 8a, the upper component of (LO + input frequency = 980 + 140 = 1120 MHz) and (LO−input frequency = 980) -140 = 840 MHz) is output from the mixer 8a. By selecting the lower component with the bandpass filter 10a, the left and right of the signal can be inverted. By using this method, even when the filter is asymmetrical, it is possible to obtain the same characteristics as a symmetrical filter.

  The actual example of the present invention described above and measurement results will be described. FIG. 11 shows the configuration of a prototype radio device. In order from the input side, low-pass filter 1, mixer 2, band-pass filter 4, mixer 5a, band-pass filter 7a, mixer 5b, band-pass filter 7b, mixer 8a, band-pass filter 10a, mixer 8b, band-pass filter 10b, mixer 11 are connected in series in this order. The frequency range of the assumed wireless system is 300 MHz to 6 GHz.

  A signal having a local frequency of (reception frequency + 8 GHz) is supplied from the variable synthesizer 3 to the mixer 2, and the mixer 2 performs up-conversion. The bandpass filter 4 limits the frequency band to 8 GHz as a center frequency (pass bandwidth: 100 MHz), and the mixer 5a has a center frequency of 836.5 MHz due to the local signal (LO = 7.1635 GHz) from the variable synthesizer 6a. Down converted. The bandpass filter 7a limits the frequency band to 836.5 MHz as a center frequency (pass bandwidth: 25 MHz) and supplies the band to the mixer 5b.

  In the mixer 5b, down-conversion is performed by the local signal from the variable synthesizer 6b, and the signal is converted into a signal having a center frequency near 140 MHz. The output signal of the mixer 5b is supplied to the mixer 8a through a bandpass filter 7b having a center frequency of 140 MHz and a pass bandwidth of 25 MHz.

  A local signal is supplied from the variable synthesizer 9a to the mixer 8a, and the mixer 8a up-converts the signal to a signal having a center frequency of 836.5 MHz. The IQ channel is inverted by up-conversion. The output signal of the mixer 8a is supplied to the mixer 8b via a bandpass filter 10a having a center frequency of 836.5 MHz and a pass bandwidth of 25 MHz.

  In the mixer 8b, down conversion is performed by the local signal from the variable synthesizer 9b, and the signal is converted into a signal having a center frequency in the vicinity of 140 MHz. The output signal of the mixer 8b is supplied to the mixer 11 via a bandpass filter 10b having a center frequency of 140 MHz and a pass bandwidth of 25 MHz.

  In the mixer 11, down conversion is performed by the local signal from the variable synthesizer 12, and the signal is converted into a signal in the range of 20 to 40 MHz. The output signal of the mixer 11 is supplied to the A / D converter 13 and converted into a digital signal.

  Table 1 shows the specifications of the wireless system as an example of the desired signal, and Table 2 shows the parameter setting values of the device example shown in FIG.

As shown in Table 1, IEEE. With a center frequency of 5170 MHz and a bandwidth of 16.6 MHz. 802.
The measurement was performed assuming 11a as a desired wave. By substituting the values of Table 1 and Table 2 into Equation (1), fx = 7008 MHz or higher, Wp = 16.6 MHz or higher from Equation (4), and fp−fs = 3.4 MHz or lower from Equation (5). Are obtained respectively. The configuration shown in FIG. 11 described above is designed to satisfy these three conditions.

  FIG. 12 shows a configuration at the time of measurement. A desired wave, an adjacent channel jamming wave, and a next adjacent channel jamming wave are generated by signal generators 21, 22 and 23, respectively. These signals are combined by the combiner 24, and the output signal of the combiner 24 is supplied to the reception RF unit 25. The reception RF unit 25 has the configuration shown in FIG. The output signal of the reception RF unit 25 is analyzed by the analysis unit 26.

As an example, the following three conditions were measured.
(A) Only the desired wave (5170 MHz) was supplied to the reception RF unit 25, and the EVM (error vector magnitude) of the output result was measured. The power of the desired wave is lowered from −5 dBm to −45 dBm.
(B) The interference wave which adds up the adjacent channel (5190 MHz) and the next adjacent channel (5210 MHz) to the desired wave (5170 MHz) to -10 dBm is added, and the power of the desired wave is lowered from -5 dBm to -45 dBm. The EVM was measured.
(C) Add the interference wave that adds -10 dBm to the adjacent channel (5150 MHz) and the next adjacent channel (5130 MHz) with respect to the desired wave (5170 MHz), and reduce the power of the desired wave from -5 dBm to -45 dBm. The EVM was measured.

  The measurement result of the condition (a) is shown in FIG. 13, the measurement result of the condition (b) is shown in FIG. 14, and the measurement result of the condition (c) is shown in FIG. In these figures, proposed and EVM represent the average EVM when the desired wave signal shown in Table 1 is received for 2 ms, and withoutRF and EVM are signals without passing only the desired wave (5170 MHz) through the reception RF unit 25. This is the value when the generator 21 is passed directly through the analyzer. withoutRF and EVM are values for comparison.

  13, 14, and 15, when the signal power of the desired wave is larger than the interference wave, the EVM is deteriorated because the total power received due to the dynamic range of the reception RF unit 25 is large and the amplifier is distorted. Because. As a result shown in FIGS. 13, 14, and 15, the same result was obtained with and without an interference wave in the adjacent channel. From this, it can be seen that, as a result of measurement using the radio device created under the above-described conditions, the interference wave of the adjacent channel can be appropriately limited by the filtering method according to the present invention.

  The present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible. For example, in the present invention, three band-pass filters and three down-conversion units are connected in series to the common frequency up-conversion unit, but two band-pass filters and two down-conversion units are connected. A conversion unit may be provided. The present invention can be applied not only to cognitive radio but also to a radio apparatus that receives a broadband signal.

It is a block diagram of one embodiment of this invention. It is a basic diagram which shows the frequency conversion process of the common frequency upconversion part in one embodiment of this invention. It is a basic diagram which shows the filtering process of the adaptive band filtering part in one embodiment of this invention. It is a basic diagram which shows the relationship between a use frequency range and the characteristic of a low-pass filter. It is a basic diagram which shows the relationship between the maximum bandwidth of a system, and the optimal frequency. It is a basic diagram which shows roughly the pattern of the signal which generate | occur | produces in a mixer. It is a basic diagram which shows roughly the setting of the bandwidth of a band pass filter. It is a basic diagram used for description of the setting of the cutoff frequency of a band pass filter, and a stop band. It is a block diagram which shows the structure at the time of using the band pass filter which has a left-right asymmetric characteristic. It is a basic diagram which shows the process of a structure at the time of using the band pass filter which has a left-right asymmetric characteristic. It is a block diagram which shows the specific example of the radio | wireless machine by this invention. It is a block diagram which shows the structure at the time of a measurement. It is a graph which shows the measurement result in 1st measurement conditions. It is a graph which shows the measurement result in 2nd measurement conditions. It is a graph which shows the measurement result in 3rd measurement conditions.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Low pass filter 2, 5, 5a, 5b, 8, 8a, 8b, 11 ... Mixer 3, 6, 6a, 6b, 9, 9a, 9b, 12 ... Variable synthesizer 4, 7, 7a , 7b, 10, 10a, 10b... Band-pass filter

Claims (14)

A low-pass filter to which a reception signal of a desired frequency band including a plurality of signals having different frequency bands or wireless systems is supplied;
An up-conversion unit that up-converts the output of the low-pass filter to a common frequency;
An adaptive filtering unit connected to the up-conversion unit,
The adaptive filtering unit includes first and second down-conversion units, and first and second filters connected to the first and second down-conversion units, respectively.
By adjusting the local frequency of the local signal supplied to the first and second down-conversion units, unnecessary signals existing respectively in the upper frequency band and the lower frequency band of the desired wave are removed. Communication device. The communication device according to claim 1,
A communication apparatus in which a common third filter is inserted between the up-conversion unit and the first down-conversion unit of the adaptive filtering unit. The communication device according to claim 1,
When the desired frequency band is (f1 to f2), the cutoff frequency of the low-pass filter is f2, the stop band of the low-pass filter is fs, and the maximum bandwidth of the wireless system to be used is BWm. A communication device in which fx is set to satisfy the following expression.
fx ≧ fs + (BWm) / 2 The communication device according to claim 3.
A communication apparatus in which a frequency LO of a local signal supplied to the up-conversion unit is set to satisfy the following expression.
LO = fx + desired frequency The communication device according to claim 1,
A communication apparatus in which the passband BWp is set to satisfy the following equation, where BWm is the maximum bandwidth of the wireless system to be used and BWp is the passband of the first and second filters.
BWp ≧ BWm The communication device according to claim 5, wherein
When the cutoff frequency of the first and second filters is fp, the stop band is fs, the minimum bandwidth of the wireless system to be used is BWn, and the channel interval is β, the following equation is set. Communication equipment.
fp−fs ≧ β−BWn The communication device according to claim 1,
When the passbands of the first and second filters are asymmetrical left and right, the left and right inversion is performed by up-converting the output signal of the first filter,
A communication apparatus that removes unnecessary signals by supplying left and right inverted signals to the second filter. Band-limiting a received signal in a desired frequency band including a plurality of signals having different frequency bands or wireless systems with a low-pass filter;
An up-conversion step for up-converting the output of the low-pass filter to a common frequency;
An adaptive filtering step for the upconverted signal,
The adaptive filtering step comprises first and second down-conversion steps, and first and second filtering steps for respective outputs of the first and second down-conversion steps;
Communication in which unnecessary signals existing in the upper frequency band and the lower frequency band of the desired wave are removed by adjusting the local frequency of the local signal used in the first and second down-conversion steps. Method. The communication method according to claim 8, wherein
A communication method in which a common third filtering step is inserted between the up-conversion step and the first down-conversion step of the adaptive filtering step. The communication method according to claim 8, wherein
When the desired frequency band is (f1 to f2), the cutoff frequency of the low-pass filter is f2, the stop band of the low-pass filter is fs, and the maximum bandwidth of the wireless system to be used is BWm. A communication method in which fx is set to satisfy the following expression.
fx ≧ fs + (BWm) / 2 The communication method according to claim 10,
A communication method in which the frequency LO of a local signal used in the up-conversion step is set to satisfy the following expression.
LO = fx + desired frequency The communication method according to claim 8, wherein
A communication method in which the passband BWp is set so as to satisfy the following equation, where BWm is the maximum bandwidth of the wireless system used and BWp is the passband of the first and second filters.
BWp ≧ BWm The communication method according to claim 12,
When the cutoff frequency of the first and second filters is fp, the stop band is fs, the minimum bandwidth of the wireless system to be used is BWn, and the channel interval is β, the following equation is set. Communication method.
fp−fs ≧ β−BWn The communication method according to claim 8, wherein
When the passbands of the first and second filters are asymmetrical left and right, the left and right inversion is performed by up-converting the output signal of the first filter,
A communication method in which left and right inverted signals are supplied to the second filter to remove unnecessary signals.

Images