JP6273310B2 - Power measuring device - Google Patents

Description

  The present invention relates to a power measuring apparatus.

  As a technique for measuring AC power, for example, there is a technique disclosed in Patent Document 1. In this technique, a voltage input from an input terminal is amplified by a voltage amplifier, frequency-converted by a mixer, and input to a vector voltmeter. On the other hand, the current is converted into a voltage signal by a current-voltage converter, frequency-converted by a mixer, and input to a vector voltmeter. The input signal of the mixer is separated into frequency components by the sweep of the local signal generator and measured by a vector voltmeter. That is, the vector voltmeter measures an effective value for each frequency component of current and voltage and a phase difference between the voltage and current. The power for each frequency component is calculated from this measured value by a computer, and the sum of these powers is calculated to obtain a desired power value.

  On the other hand, as a method for measuring a broadband signal, for example, a configuration shown in FIG. 13 is known. 13 includes an input terminal 210, a low-pass filter 211, a mixer 212, a local oscillator signal generator 213, a filter 214, a mixer 215, a local oscillator signal generator 216, a band pass filter 217, and a detector 218. have.

  In the power measuring device shown in FIG. 13, the wideband signal input from the input terminal 210 passes through a desired band by the low-pass filter 211, and the other band is attenuated and output. The mixer 212 converts the input signal into a high frequency or a low frequency according to the local signal supplied from the local signal generator 213. The filter 214 passes a signal in a target band from the signal output from the mixer 212, and attenuates and outputs the other signals. The mixer 215 converts the signal output from the filter 214 into a desired band by the local signal output from the local signal generator 216, and supplies the band to the bandpass filter 217. The bandpass filter 217 passes a desired band from the signal output from the mixer 215, and attenuates the rest and supplies it to the detector 218. The detector 218 measures the signal supplied from the band pass filter 217.

  In the power measuring apparatus shown in FIG. 14, the signal input from the input terminal 310 is quadrature demodulated by the mixers 311 and 312, the local oscillation signal generator 314, and the phase shifter 313 to convert a desired band to a low frequency. After that, the vicinity of the target band is cut out by the filters 315 and 316. The output signals of the filters 315 and 316 are input to the analog-digital converters 317 and 318 and converted into digital signals, and then the signal power is measured by the digital signal processing unit 319.

Japanese Patent Laid-Open No. 06-273458

  By the way, the technique disclosed in Patent Document 1 has a problem in that since there is no filter on the input side, it is impossible to accurately measure only the power of a signal in a target band from a wide desired band.

  Further, in the conventional example shown in FIG. 13, the second and higher harmonics of the local signal are generated due to the distortion characteristics of the mixer 212, and an unintended band of the input signal is converted into a frequency to be measured by this harmonic. End up. For this reason, since the low-pass filter 211 needs to attenuate the band corresponding to the second and higher harmonics, a large number of filters are required, resulting in high cost and complicated design. Further, the filter 214 requires a steep cutoff characteristic for leakage of the local oscillation signal 213 and suppression of unnecessary bands. For example, an expensive filter such as a SAW filter is used as a filter having such a steep characteristic. Since this is necessary, there is a problem that the manufacturing cost of the device is increased.

  Further, the conventional example shown in FIG. 14 uses a digital component such as a digital signal processor 319 configured by analog-digital converters 317 and 318, a DSP (Digital Signal Processor), and the like, so that the apparatus becomes expensive. There is a point. Further, since aliasing occurs in the analog-digital converters 317 and 318 by the sampling theorem, it is necessary to suppress aliasing. For this reason, there is a problem that the sampling frequency of the analog-digital converters 317 and 318 must be increased, or that an anti-aliasing filter used for band limitation requires steep characteristics. Furthermore, since spurious and power supply noise generated in the middle of frequency conversion enter the measurement target band as image components and alias components, it is necessary to design them in consideration of these, and the design is complicated. There is also the problem of becoming.

  In particular, the cutoff characteristics of the filters used in these circuits generally vary depending on the ambient temperature. However, if there are many parts around the filter, these temperature variations will cause the characteristics of the filter to vary greatly, resulting in measurement. There is a problem that an error occurs in the result.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a power measuring apparatus capable of accurately measuring the power of a broadband signal with a simple circuit configuration and low cost.

In order to solve the above-described problem, the present invention provides a power measurement apparatus that inputs a signal having a predetermined band and measures the power of a signal in a target band included in the predetermined band. A first filter that attenuates signals in other bands and a signal in the target band that has passed through the first filter is converted into a predetermined frequency by the input first signal. A frequency converter, a second filter that passes the signal in the target band from the signal output from the first frequency converter, and attenuates the other band; and a signal output from the second filter Second frequency conversion means for converting the signal into a frequency signal, wherein the first signal is a rectangular wave.
According to such a configuration, it is possible to accurately measure the power of a signal in a desired band among signals of a predetermined band input with a simple circuit configuration and low cost.

Further, the invention is characterized in that the signal having the predetermined band has a bandwidth in which the frequency on the high frequency side of the band is three times or more the frequency on the low frequency side.
According to such a configuration, a low-pass filter having a gentle cutoff characteristic can be used, and the number of low-pass filters can be reduced.

In addition, the present invention has two each of the first frequency conversion means, the second filter, and the second frequency conversion means, one of the first frequency conversion means and one of the second filters. A first signal line connected in series with one of the second frequency converting means, the other first frequency converting means, the other second filter, and the other second frequency converting means. Are connected in series, and the second signal line is different from the first signal line, and the first and second signal lines are respectively connected in parallel to the output of the first filter, The two first frequency converters connected to the first and second signal lines are inputted with the first signals having phases orthogonal to each other, and the center frequency of the output signal becomes a DC component. Frequency conversion to The two second frequency conversion means connected to the first and second signal lines perform frequency conversion so that signals whose phases are orthogonal to each other are input and the center frequency of the output signal becomes a desired frequency. Features.
According to such a configuration, it is possible to accurately measure the band characteristics of the target band.

In addition, the present invention is characterized in that it further includes a removing unit that is disposed after the first frequency converting unit and removes a component in the vicinity of a direct current.
According to such a configuration, power can be accurately measured by attenuating spurious and the like appearing near the direct current.

Further, the present invention is characterized in that each of the first frequency conversion means, the second filter, and the second frequency conversion means includes a pair of elements for processing a differential signal. .
According to such a configuration, the common mode noise can be canceled and attenuated, so that the power can be accurately measured.

At least one of the subsequent stage of the first filter and the subsequent stage of the second filter has amplification means for amplifying an input signal and outputting the amplified signal to the subsequent stage.
According to such a configuration, the range in which the power can be accurately measured can be expanded.

  According to the present invention, it is possible to provide a power measuring apparatus capable of accurately measuring the power of a broadband signal with a simple circuit configuration and low cost.

It is a figure which shows the structural example of the electric power measurement apparatus which concerns on 1st Embodiment of this invention. It is a figure explaining operation | movement of 1st Embodiment shown in FIG. It is a figure explaining operation | movement of 1st Embodiment shown in FIG. It is a figure which shows the structural example of the electric power measuring apparatus which concerns on 2nd Embodiment of this invention. It is a figure explaining operation | movement of 2nd Embodiment shown in FIG. It is a figure which shows the structural example of the electric power measurement apparatus which concerns on 3rd Embodiment of this invention. It is a figure which shows the structural example of the electric power measurement apparatus which concerns on 4th Embodiment of this invention. It is a figure which shows the structural example of the electric power measurement apparatus which concerns on 5th Embodiment of this invention. It is a figure explaining operation | movement of 5th Embodiment shown in FIG. It is a figure explaining operation | movement of 5th Embodiment shown in FIG. It is a flowchart explaining the operation | movement of 5th Embodiment shown in FIG. It is a figure which shows the structural example of the electric power measurement apparatus which concerns on 6th Embodiment of this invention. It is a figure which shows the structural example of the conventional electric power measuring apparatus. It is a figure which shows the other structural example of the conventional electric power measuring apparatus.

  Next, an embodiment of the present invention will be described.

(A) Description of Configuration of First Embodiment of the Present Invention FIG. 1 is a diagram illustrating a configuration example of a power measuring apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the power measuring apparatus according to the first embodiment includes an input terminal 10, a first filter 11, a mixer 12, a local oscillator signal generator 13, a filter 14a, a mixer 15, a local oscillator signal generator 16, A third filter 17 and a detector 18 are provided.

  Here, for example, a signal having a band of 70 to 770 MHz shown in FIG. 2A is a signal used for CATV (Cable Television), for example, and has a plurality of channels having a bandwidth of 6 MHz, for example, in a band of 70 to 770 MHz. Yes. The signal of each channel is a signal subjected to modulation such as OFDM modulation, for example.

  The first filter 11 passes a signal in a predetermined band including a channel (target band) to be measured from the signal input from the input terminal 10, and attenuates and outputs other signals.

  The mixer 12 outputs a signal obtained by multiplying the local signal output from the local signal generator 13 and the signal output from the first filter 11.

  The local oscillation signal generator 13 generates a rectangular wave having a predetermined frequency and supplies it to the mixer 12 as a local oscillation signal.

  The filter 14a passes a signal in a predetermined band from the signal output from the mixer 12, and attenuates and outputs the other signals.

  The mixer 15 outputs a signal obtained by multiplying the local signal output from the local signal generator 16 by the signal output from the filter 14a.

  The local oscillation signal generator 16 generates a sine wave having a predetermined frequency and supplies it to the mixer 15 as a local oscillation signal.

  The third filter 17 is configured by a band pass filter or the like, and passes a signal in a predetermined band from the signal output from the mixer 15, and attenuates and outputs the other signals.

  The detector 18 detects the waveform of the signal output from the third filter 17.

(B) Description of Operation of First Embodiment of the Invention Next, the operation of the first embodiment shown in FIG. 1 will be described. The first embodiment of the present invention is characterized in that a square wave is used as a local oscillation signal supplied to the mixer 12 instead of a general sine wave. This will be described below.

  FIG. 2A shows an example of a signal input to the power measurement apparatus according to the first embodiment as described above. In this example, the input signal has a bandwidth of 70 to 770 MHz. Consider a case where, for example, an 80 MHz sine wave shown in FIG. 2B is used as a local oscillation signal supplied to the mixer 12 for such an input signal. When an 80 MHz sine wave is used, the local oscillation signal of the mixer 12 generally has a distortion characteristic because a large amount of power is required for the input signal. The sine wave supplied from the local oscillator signal generator 13 has a harmonic component as schematically shown in FIG. In the example of FIG. 2C, the fundamental frequency component of 80 MHz has second-order (160 MHz), third-order (240 MHz), fourth-order (320 MHz),... Harmonic components.

  Here, when the target band is a signal in the vicinity of 70 MHz, the signal is converted into, for example, a low frequency signal (several tens of MHz) by the local signal input to the mixer 12 in FIG. However, since the same conversion is also performed for the harmonic components 160 MHz, 240 MHz, 320 MHz,..., The signals in the vicinity of each of the 150 MHz, 230 MHz, 310 MHz,. It is converted into a frequency signal. In order to prevent the frequency conversion of the band other than the measurement target, for example, a filter having a characteristic of attenuating a signal of 160 MHz or higher as shown by a thick line in FIG. There is a need. However, the low-pass filter for attenuating the second harmonic or higher so as not to be output needs to have a steep cutoff characteristic, so that an expensive filter such as a SAW filter is required.

  On the other hand, in the first embodiment of the present invention, a rectangular wave is used instead of a sine wave as a signal supplied from the local oscillation signal generator 13 to the mixer 12. As schematically shown in FIG. 3B, the rectangular wave is an odd-order harmonic component such as the third, fifth, seventh,... Is a superimposed signal. When such a local oscillation signal is supplied to the mixer 12, even if the rectangular wave is a signal larger than the input signal, the odd-order component is mainly included, and the even-order component is suppressed. . For this reason, for example, since the second-order harmonic component is very small as compared with the case of FIG. 2, the level is sufficiently negligible in the frequency conversion.

  For the reasons described above, in the first embodiment, the mixer 12 can sufficiently ignore even-order and higher-order harmonic components of the local oscillation signal. Therefore, as the first filter 11, for example, FIG. ), It is sufficient to have a characteristic of attenuating the third harmonic component (240 MHz) or more as indicated by a thick line. For this reason, since the cutoff characteristic may be gentler than the characteristic when the sine wave is used as the local oscillation signal (characteristic indicated by the broken line in FIG. 3C), an inexpensive filter is used as the first filter 11. Can do.

  The signal output from the mixer 12 passes through the vicinity of the target band corresponding to the channel to be measured by the filter 14 a and is supplied to the mixer 15. The mixer 15 converts the signal of the channel to be measured output from the filter 14a into a predetermined frequency (for example, several tens of MHz) and outputs the converted signal. The third filter 17 further attenuates and outputs adjacent frequencies other than the target band from the signal output from the mixer 15. The detector 18 detects the waveform of the signal output from the third filter 17. As a result, the waveform of the signal of the desired channel can be detected, and the power can be measured based on the result.

  In the above description, the mixer 12 is configured to convert the signal output from the first filter 11 to several tens of MHz, but may convert the signal to other frequencies (for example, several thousand MHz).

(C) Description of Configuration of Second Embodiment of the Present Invention Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 4, the same reference numerals are given to the portions corresponding to those in FIG.

  4, compared with FIG. 1, the filter 14a is replaced with the second filter 14, and a mixer 22, a mixer 25, a second filter 24, and phase shifters 26 and 27 are added. Other configurations are the same as those in FIG.

  Here, the mixer 22 multiplies the local signal supplied from the phase shifter 26 and the input signal supplied from the first filter 11 and outputs the result.

  The second filter 14 passes a signal of a predetermined frequency from the signal output from the mixer 12, and attenuates and outputs the other band. The second filter 24 passes a signal having a predetermined frequency from the signal output from the mixer 22 and attenuates and outputs the other band.

  The mixer 25 multiplies the local oscillation signal supplied from the phase shifter 27 and the input signal supplied from the second filter 24 and outputs the result.

  The phase shifter 26 adjusts the phase of the rectangular wave signal output from the local oscillation signal generator 13 so as to be different by 90 degrees and outputs it.

  The phase shifter 27 adjusts the phase of the sine wave signal output from the local signal generator 16 so as to be different by 90 degrees and outputs the result.

(D) Description of Operation of Second Embodiment of the Invention Next, the operation of the second embodiment shown in FIG. 4 will be described. Consider a case where, for example, a 73 MHz rectangular wave is used as the first local oscillation signal. When a signal having a bandwidth of 70 to 770 MHz as shown in FIG. 5A is input from the input terminal 10, a signal having a predetermined frequency or less is passed by the first filter 11, and the others are attenuated. . For example, assuming that the characteristic of the first filter 11 is a characteristic indicated by a thick line in FIG. 5A, the first filter 11 outputs a signal having a band as shown in FIG.

  The mixer 12 multiplies the rectangular wave output from the local signal generator 13 and the signal output from the first filter 11 and outputs the result. Further, the mixer 22 multiplies the rectangular wave output from the local signal generator 13 and whose phase is shifted by 90 degrees by the phase shifter 26 and the signal output from the first filter 11 and outputs the result. As a result, the quadrature demodulated signals are output from the mixers 12 and 22.

  As shown in FIG. 5C, the signals output from the mixers 12 and 22 are frequency-converted so that the center frequency of the target band becomes a direct current component. At this time, in the region corresponding to the negative frequency component (the region subjected to cross-hatching), the signal output from the mixers 12 and 22 has a complex signal component by orthogonal demodulation. Hold in state.

  In the second filters 14 and 24, the signal of the target band to be measured is passed from the signals output from the mixers 12 and 22, and the other bands are attenuated. As a result, the second filters 14 and 24 output signals that are attenuated except for the target band to be measured by the filter characteristics indicated by the thick lines in FIG.

  The mixer 15 multiplies the sine wave signal having the frequency F2 output from the local signal generator 16 and the signal output from the second filter 14 and outputs the result. The mixer 25 multiplies the signal output from the second filter 24 by multiplying the sine wave signal output from the local signal generator 16 and whose phase is shifted by 90 degrees by the phase shifter 27 with the frequency F2. To do. As a result, as shown in FIG. 5E, the signals output from the mixers 15 and 25 are signals obtained by frequency-converting the signal shown in FIG. 5D by the frequency F2.

  The signals output from the mixers 15 and 25 suppress the adjacent bands that have passed through the second filters 14 and 24 by the third filter 17, and the band signal (the signal of the channel to be measured) shown in FIG. ) Is passed, and the others are attenuated and output. The detector 18 detects the waveform of the signal output from the third filter 17.

  As described above, according to the second embodiment of the present invention, the frequency conversion is performed by the rectangular wave as in the first embodiment, so that the first filter 11 having a non-steep cutoff characteristic is used. As a result, manufacturing costs can be reduced.

  In the second embodiment, since quadrature demodulation and quadrature modulation are performed, the center frequency of the input signal and the frequency of the local oscillation signal can be made the same frequency, so that the target band can be converted to a frequency near DC. Therefore, the power can be detected accurately.

  In the second embodiment, the mixers 12 and 22 convert the signal including the target band into a signal near DC. The element values of the elements (coils and capacitors) constituting the second filters 14 and 24 change with temperature, but the rate of change is proportional to the frequency. For this reason, since the element used for the 2nd filters 14 and 24 which pass the frequency near direct current changes little with temperature, it can measure correctly regardless of a temperature change.

(E) Description of Configuration of Third Embodiment of the Present Invention Next, a third embodiment of the present invention will be described with reference to FIG. In FIG. 6, parts corresponding to those in FIG.

  In FIG. 6, compared with FIG. 4, DC component removal elements 31 and 41 are added after the second filters 14 and 24. The rest of the configuration is the same as in FIG.

  Here, the DC component removing element 31 is constituted by, for example, a capacitor, removes a component near the DC included in the signal output from the second filter 14, and supplies the component to the subsequent mixer 15. Similarly, the DC component removing element 41 is constituted by, for example, a capacitor, removes a component near the DC included in the signal output from the second filter 24, and supplies it to the mixer 25 at the subsequent stage.

(F) Description of Operation of Third Embodiment of the Invention Next, the operation of the third embodiment will be described. The outputs of the mixers 12 and 22 may contain spurious signals. That is, spurious may occur in the vicinity of the DC component due to an imbalance in quadrature demodulation or a quadrature component phase shift caused by a phase shift generated by the phase shifter 26. This spurious component near the DC component is observed as a signal in the target band, and an error may occur in the measurement result. Therefore, by inserting an element such as a capacitor before the mixers 15 and 25 that perform quadrature modulation, it is possible to remove spurious components near the DC component. For this reason, it is possible to prevent measurement errors due to spurious.

  In the example illustrated in FIG. 6, the capacitor has been described as an example of the DC component removing element, but other elements (for example, a diode or the like) may be used.

(G) Description of Configuration of Fourth Embodiment of the Present Invention Next, a fourth embodiment of the present invention will be described with reference to FIG. In FIG. 7, the same reference numerals are given to the portions corresponding to those in FIG.

  7, compared with FIG. 6, phase shifters 51 and 52 are added, and the mixers 12 and 22, the second filters 14 and 24, the DC component removing elements 31 and 41, and the mixers 15 and 25 are mixed with the mixer 112. , 122, second filters 114, 124, DC component removing elements 131, 141, and mixers 115, 125, respectively. Further, the signal line between the phase shifter 51 and the phase shifter 52 is replaced with a balanced line.

  Here, the phase shifter 51 distributes the signal output from the first filter 11 into two, adjusts each phase difference to be 180 degrees, and outputs it as a differential signal.

  The mixer 112 is constituted by a pair of adjacently arranged mixers, and is supplied from the local signal generator 13 for each of two signals output from the phase shifter 51 and having a phase difference of 180 degrees. Multiply square wave and output. Signal lines connecting the phase shifter 51 and the mixer 112 are arranged adjacent to each other. The mixer 122 is composed of a pair of mixers arranged adjacent to each other, and is supplied from the local signal generator 13 for each of the two signals output from the phase shifter 51 that are 180 degrees different in phase. The rectangular wave phase shifted by 90 degrees by the phase shifter 26 is multiplied and output. Signal lines connecting the phase shifter 51 and the mixer 122 are arranged adjacent to each other.

  The second filter 114 is composed of a pair of adjacent low-pass filters, and passes a signal in a predetermined frequency band included in the signal output from the mixer 112 and supplies the signal to the DC component removal element 131. Note that signal lines connecting the mixer 112 and the first filter 114 are arranged adjacent to each other. The second filter 124 includes a pair of low-pass filters arranged adjacent to each other, passes a signal in a predetermined frequency band included in the signal output from the mixer 122, and supplies the signal to the DC component removal element 141. Note that signal lines connecting the mixer 122 and the second filter 124 are arranged adjacent to each other.

  The direct current component removing element 131 is configured by a pair of adjacent direct current component removing elements, removes a component near the direct current contained in the signal output from the second filter 114 and supplies it to the mixer 115. Note that signal lines connecting the second filter 114 and the DC component removing element 131 are arranged adjacent to each other. The direct current component removing element 141 is configured by a pair of adjacent direct current component removing elements, and removes a component near the direct current contained in the signal output from the second filter 124 and supplies it to the mixer 125. Signal lines connecting the second filter 124 and the DC component removing element 141 are arranged adjacent to each other.

  The mixer 115 is composed of a pair of mixers arranged adjacent to each other, and multiplies the signal supplied from the DC component removing element 131 by the sine wave supplied from the local signal generator 16 and outputs the result. Note that signal lines connecting the DC component removing element 131 and the mixer 115 are arranged adjacent to each other. The mixer 125 is composed of a pair of mixers arranged adjacent to each other. The mixer 125 is supplied from the DC component removing element 131 and the local signal generator 16 and is phase-shifted 90 degrees by the phase shifter 27. Multiply by the sine wave and output. Note that signal lines connecting the DC component removing element 141 and the mixer 125 are arranged adjacent to each other.

  The phase shifter 52 inverts and synthesizes one phase of the differential signal output from the mixer 115, and inverts and synthesizes one phase of the differential signal output from the mixer 125. Then, the synthesized differential signal from the mixer 115 and the synthesized differential signal from the mixer 125 are synthesized and output to the third filter 17. The signal lines connecting the mixer 115 and the phase shifter 52 are arranged adjacent to each other, and the signal lines connecting the mixer 125 and the phase shifter 52 are arranged adjacent to each other.

(H) Description of Operation of the Fourth Embodiment of the Present Invention In the fourth embodiment, each of the mixers 112 and 122, the second filters 114 and 124, the DC component removing elements 131 and 141, and the mixers 115 and 125 is 1 A pair of elements are arranged adjacent to each other. Further, signal lines connecting these pair of elements are also arranged adjacent to each other. Since the differential signal passing through the pair of elements or signal lines is finally inverted and synthesized by the phase shifter 52, when noise is added to the pair of elements or signal lines, the noise Is added to the differential signal as an in-phase signal, and is canceled when the differential signal is inverted and synthesized by the phase shifter 52. For this reason, in 4th Embodiment, generation | occurrence | production of the error resulting from the noise etc. which generate | occur | produced by the leakage from a power supply circuit or a local signal generator can be suppressed.

(I) Description of Configuration of Fifth Embodiment of the Invention Next, a fifth embodiment of the invention will be described with reference to FIG. In FIG. 8, the same reference numerals are given to the portions corresponding to those in FIG.

  In FIG. 8, compared with FIG. 7, the first filter 11 is replaced with switches 61 to 64 and low-pass filters 65 to 67 for stepping out the target band from a predetermined band. Other configurations are the same as those in FIG.

  Here, the switches 61 to 64 are controlled by a control unit (not shown) and have a function of connecting any one of the low-pass filters 65 to 67 between the input terminal 10 and the phase shifter 51. More specifically, the switch 61 connects the output of the input terminal 10 to one of the input of the switch 62 and the input of the low-pass filter 67. The switch 62 connects the output of the switch 61 to one of the input of the low pass filter 65 and the input of the low pass filter 66. The switch 63 connects either the output of the low-pass filter 65 or the output of the low-pass filter 66 to the input of the switch 64. The switch 64 connects either the output of the switch 63 or the output of the low-pass filter 67 to the input of the phase shifter 51.

  The low-pass filters 65 to 67 pass signals of different bands from the signal having a predetermined bandwidth input from the input terminal 10 and output the signals. More specifically, for example, the low-pass filter 65 has a characteristic indicated by a thick line passing through the first band shown in FIG. 9D. The low pass filter 66 has a characteristic indicated by a thick line passing through the second band. Further, the low pass filter 67 has a characteristic indicated by a thick line passing through the third band.

(J) Description of Operation of Fifth Embodiment of the Invention Next, the operation of the fifth embodiment will be described. For example, assume that a signal having a bandwidth of 70 to 770 MHz as shown in FIG. Note that this input signal includes a plurality of target bands having a bandwidth of 6 MHz.

  A control unit (not shown) specifies a band including a channel (target band) to be measured, and selects a low-pass filter that passes the band. For example, when the target channel belongs to the range of 70 to 210 MHz, the switches 61 to 64 are controlled so as to select the low pass filter 65 that passes through the first band. When the target channel belongs to the range of 210 to 630 MHz, the switches 61 to 64 are controlled so as to select the low pass filter 66 that passes through the second band. Further, when the target channel belongs to the range of 630 to 770 MHz, the switches 61 to 64 are controlled so as to select the low pass filter 67 that passes through the third band. For example, when a channel belonging to 70 to 210 MHz is selected as a measurement target, the switches 61 to 64 are controlled so as to select the low pass filter 65 that passes through the first band.

  An input signal that has passed through any of the low-pass filters 65 to 67 and is band-limited (in this example, a signal having a bandwidth of 70 to 210 MHz) is differentiated by the phase shifter 51, and one of the signals remains as it is. Is output as a positive phase signal, and the other is output as a negative phase signal with the phase inverted. The signal generated in this way is supplied as a differential signal to mixers 112 and 122 composed of a pair of elements.

  The mixers 112 and 122 orthogonally demodulate the band-limited signal supplied from the phase shifter 51 with the local signals supplied from the local signal generator 13 and the phase shifter 26. For example, assuming that the channel to be measured is a band of 70 to 76 MHz, a control unit (not shown) controls the local signal generator 13 to generate a local signal (rectangular wave) of 73 MHz. As a result, a signal of 70 to 210 MHz is output as a signal of −3 to 137 MHz.

  The second filters 114 and 124 pass signals of approximately −3 to approximately +3 MHz corresponding to one channel from the signals output from the mixers 112 and 122, and attenuate and output the other bands. As a result, only a signal having a bandwidth corresponding to one channel is passed and supplied to the DC component removing elements 131 and 141.

  The DC component removing elements 131 and 141 remove components near the DC included in the signals output from the second filters 114 and 124 and supply them to the mixers 115 and 125. Thereby, the spurious component converted into the component near the direct current is removed. The DC component removing elements 131 and 141 remove not only the spurious component but also a part of the input signal. However, since the removed signal is very small compared to the whole, the power measurement error is small. .

  The mixers 115 and 125 orthogonally modulate the signal having a bandwidth of −3 to +3 MHz supplied from the DC component removing elements 131 and 141 with, for example, a local oscillator signal (sine wave signal) of 50 MHz. As a result, a signal with a bandwidth of −3 to +3 MHz supplied from the DC component removing elements 131 and 141 is output as a signal with a bandwidth of 47 to 53 MHz. In addition, the frequency of the local oscillation signal of the mixers 115 and 125 can be arbitrarily set according to the circuit at the subsequent stage.

  The phase shifter 52 receives the differential signals output from the mixers 115 and 125, synthesizes and outputs a normal phase signal and a negative phase signal. Thereby, the noise superimposed in the common mode can be canceled and reduced.

  The third filter 17 passes a signal having a bandwidth of 47 to 53 MHz from the signal output from the phase shifter 52, and further suppresses and outputs other signals, particularly signals adjacent to the target band.

  The detector 18 detects the signal output from the third filter 17. As a result, the waveform of a signal in the 70 to 76 MHz band, which is a desired channel, can be observed and the power can be measured.

  As described above, according to the fifth embodiment of the present invention, since the low-pass filters 65 to 67 are selected by the switches 61 to 64, an optimum low-pass filter is selected according to the channel to be measured. It is possible to easily select and accurately measure the target band within a predetermined band.

  In the fifth embodiment, since a rectangular wave is used as a local signal for quadrature demodulation, a low-pass filter 65 to 67 having a gentle cutoff characteristic can be used, and the number of low-pass filters can be reduced. Can be reduced. That is, when a sine wave is used as a local oscillation signal for quadrature demodulation, for example, when the local oscillation signal is 70 MHz shown in FIG. 10B, the mixers 112 and 122 are as shown in FIG. The second, third, fourth,... Harmonics are generated by the distortion characteristics. Since the input signal is a broadband signal of 70 to 770 MHz, the signal is also present at the position where these harmonics exist. For this reason, quadrature demodulation is also performed with harmonics, and the signal generated by this quadrature modulation is frequency-converted to the desired band, which causes measurement errors. It needs to be attenuated by a low-pass filter. When the local oscillation signal is 70 MHz, the lowest harmonic is 140 MHz, which is the second harmonic. Therefore, it is necessary to sufficiently suppress the input signal by a low-pass filter that attenuates 140 MHz or more as shown in FIG. Occurs. On the other hand, when a rectangular wave is used as the local oscillation signal, when the local oscillation signal is 70 MHz, the lowest harmonic is the third harmonic, and therefore, as shown in FIG. The characteristic may be attenuated at 210 MHz or higher. For this reason, as is clear from a comparison between FIG. 9D and FIG. 10D, the cutoff characteristic of the low-pass filter can be made gentler in the fifth embodiment.

  When a sine wave is used as a local oscillation signal, the cutoff frequency of the low-pass filter when a 140 MHz local oscillation signal is used is 280 MHz. Similarly, when the 280 MHz local oscillation signal is used, the cutoff frequency of the low-pass filter is 560 MHz. The cutoff frequency of the low-pass filter when using a 560 MHz local oscillation signal is 1120 MHz. Therefore, when a sine wave is used, four low-pass filters are required as shown in FIG. On the other hand, when a rectangular wave is used, three low-pass filters may be used as shown in FIG. For this reason, in the fifth embodiment, by using a rectangular wave as a local oscillation signal, it is possible to use a filter having a gentle cutoff characteristic as the low-pass filters 65 to 67 and to reduce the number of filters.

  Moreover, the cutoff frequency of the low-pass filters 65 to 67 may be set as appropriate if the components in the cutoff band do not pass.

  Next, an example of processing executed in the fifth embodiment will be described with reference to FIG. The following processing is an example, and such processing may be executed using a logic circuit, for example. When the process of FIG. 11 is started, the following steps are executed.

  In step S10, a measurement target band is designated. For example, a predetermined target band having a bandwidth of 70 to 76 MHz is designated by the measurer.

  In step S11, the band to which the target band belongs is specified. For example, in the case of the target band having a bandwidth of 70 to 76 MHz as described above, the first band shown in FIG. 9D is specified.

  In step S <b> 12, a local oscillation signal having a frequency corresponding to the target band is output from the local oscillation signal generator 13. For example, the local signal generator 13 generates and outputs a rectangular wave having a frequency corresponding to the center frequency of the target band.

  In step S13, if the band specified in step S11 is the first band, the process proceeds to step S14. If the band is the second band, the process proceeds to step S15. If the band is the third band, the process proceeds to step S16.

  In step S14, a low-pass filter that passes through the first band shown in FIG. 9D is selected. More specifically, the low pass filter 65 shown in FIG. 8 is selected.

  In step S15, a low-pass filter that passes through the second band shown in FIG. 9D is selected. More specifically, the low pass filter 66 shown in FIG. 8 is selected.

  In step S16, a low-pass filter that passes through the third band shown in FIG. 9D is selected. More specifically, the low pass filter 67 shown in FIG. 8 is selected.

  In step S17, detection processing is executed. As a result, a signal in the target band is extracted, and detection processing is executed.

  In step S18, it is determined whether or not the measurement is to be terminated. If the measurement is to be continued (step S18: N), the process returns to step S10 and the same processing as described above is repeated, otherwise (step S18). : Y) ends the process.

  According to the processing of the above flowchart, the power of a predetermined channel designated by the measurer can be measured.

  In the flowchart shown in FIG. 11, the power of the channel designated by the measurer is measured. For example, the same measurement is repeated for other channels, and the power of all channels is automatically measured. May do

(K) Description of Configuration of Sixth Embodiment of the Present Invention Next, a sixth embodiment of the present invention will be described with reference to FIG. In FIG. 12, parts corresponding to those in FIG.

  In FIG. 12, an amplifier 70 is added between the switch 64 and the phase shifter 51 as compared with FIG. 8. Further, the DC component removing elements 131 and 141 are replaced with the DC component removing elements 133 and 143, and amplifiers 116 and 126 are added between the second filters 114 and 124 and the DC component removing elements 133 and 143, respectively. Other configurations are the same as those in FIG.

  Here, the amplifier 70 amplifies the signal output from the switch 64 with a predetermined gain and outputs the amplified signal. The amplifier 116 amplifies the signal output from the second filter 114 with a predetermined gain and outputs the amplified signal. The amplifier 126 amplifies the signal output from the second filter 124 with a predetermined gain and outputs the amplified signal.

  In the DC component removing element 133, a coil is connected to the output of the capacitor, and a desired DC bias can be applied by applying a DC voltage to the coil. In the DC component removing element 143, a coil is connected to the output of the capacitor, and a desired DC bias can be applied by applying a DC voltage to the coil.

(L) Description of Operation of Sixth Embodiment of the Invention Next, the operation of the sixth embodiment will be described. The operation of the sixth embodiment is substantially the same as that of the fifth embodiment, and therefore will be described by focusing on the differences.

  In the sixth embodiment, the range in which the power can be accurately measured can be expanded by amplifying the input signal using the amplifier 70. That is, since the signal in the target band is lost by the low-pass filters 65 to 67 and the switches 61 to 64, it may be buried in the noise component and accurate power measurement may not be performed, but is input to the mixers 112 and 122 by the amplifier 70. By amplifying the previous input signal, the signal level can be increased and an accurate measurement can be performed.

  Further, by amplifying the output signals of the second filters 114 and 124 by the amplifiers 116 and 126, the loss due to the phase shifter 51 and the quadrature demodulation can be compensated, so that accurate measurement can be executed.

  Further, by applying a desired DC bias to the signals output from the DC component removing elements 133 and 143 in the previous stage of performing the orthogonal modulation by the mixers 115 and 125 by the DC component removing elements 133 and 143, the orthogonal modulation is performed. The phase balance can be maintained with high accuracy. More specifically, the imbalance caused by the phase shift of the mixers 112 and 122 can be eliminated by adjusting the DC bias.

  Further, by performing quadrature modulation in a highly versatile frequency band by the mixers 115 and 125, the third filter 17 having high versatility and low cost sufficiently suppresses adjacent signals in the target band, and the power of the signal in the target band. Can be measured accurately.

(M) Description of Modified Embodiment Each of the above embodiments is an example, and it is needless to say that the present invention is not limited to the case described above. For example, in each of the embodiments described above, the signal output from the mixer 12 is converted so that the center frequency of the target channel is a DC component, but may be a frequency other than this.

  In the above third to fifth embodiments, the DC component removing elements 31, 41, 131, 141, 133, and 143 are provided at the subsequent stage of the second filters 14, 24, 114, and 124. You may make it provide in.

  In the sixth embodiment described above, the second filters 114 and 124 are provided after the mixers 112 and 122, but may be provided after the DC component removing elements 113 and 143.

  Also in the first embodiment, two mixers 12, two filters 14a, and two mixers 15 may be provided, and a signal may be transmitted between them by a differential signal.

  In the sixth embodiment, the amplifiers 70, 116, and 126 are arranged in both the subsequent stage of the switch 64 and the subsequent stage of the second filters 114 and 124, respectively. However, the subsequent stage of the switch 64 and the second filters 114 and 124 are arranged. You may make it arrange | position only in either one of the back | latter stage.

  Further, in each of the above embodiments, the frequency band of the input signal is 70 to 770 MHz, but may be a frequency band other than this. Note that the effect of the present invention can be expected if the frequency on the high band side (770 MHz in the illustrated example) is three times or more the frequency on the low band side (70 MHz in the illustrated example).

  In each of the above embodiments, a filter having a characteristic other than a low pass, such as a band pass filter, may be used as the filter in the previous stage of the mixer 12.

  In each of the above embodiments, the local signal generator 13 outputs a rectangular wave, and the rectangular wave is input to the mixers 12, 22, 112, 122. However, the local signal generator outputs the rectangular wave. You may make it input into these mixers using the means which converts the signal which is not a rectangular wave into a rectangular wave.

10 Input terminal 11 First filter 12, 22, 112, 122, 125 Mixer (first frequency conversion means)
15, 25, 115, 125 Mixer (second frequency conversion means)
13, 16 Local signal generator 14a Filter 14, 24, 114, 124 Second filter (low-pass filter)
17 Third filter (bandpass filter)
18 detector 26, 27 phase shifter 31, 41, 131, 141, 133, 143 DC component removal element (removal means)
51, 52 Phase shifter 61-64 Switch 65-67 Low pass filter (first filter)
70, 116, 126 Amplifier (amplifying means)

Claims (6)

In a power measurement device that inputs a signal having a predetermined band and measures the power of a signal in a target band included in the predetermined band,
A first filter that passes a signal in a band including the target band and attenuates a signal in the other band;
First frequency conversion means for converting the signal in the target band that has passed through the first filter into a predetermined frequency by the input first signal;
A second filter that passes the signal in the target band from the signal output from the first frequency conversion means and attenuates the other bands;
Second frequency conversion means for converting a signal output from the second filter into a signal of a desired frequency,
The power measuring apparatus according to claim 1, wherein the first signal is a rectangular wave.   The power measuring apparatus according to claim 1, wherein the signal having the predetermined band has a bandwidth in which a frequency on a high frequency side of the band is three times or more of a frequency on a low frequency side. Two each of the first frequency converting means, the second filter, and the second frequency converting means,
A first signal line in which one of the first frequency conversion means, one of the second filters, and one of the second frequency conversion means are connected in series;
A second signal line different from the first signal line, wherein the other first frequency conversion means, the other second filter, and the other second frequency conversion means are connected in series;
Have
The first and second signal lines are respectively connected in parallel to the output of the first filter,
The two first frequency converters connected to the first and second signal lines receive the first signals whose phases are orthogonal to each other, and the center frequency of the output signal becomes a DC component. Frequency conversion and so on
The two second frequency conversion means connected to the first and second signal lines perform frequency conversion so that signals whose phases are orthogonal to each other are input and the center frequency of the output signal becomes a desired frequency. The power measuring device according to claim 1 or 2, wherein   4. The power measuring apparatus according to claim 1, further comprising a removing unit that is disposed downstream of the first frequency converting unit and removes a component in the vicinity of a direct current. 5.   5. The first frequency converting means, the second filter, and the second frequency converting means are each composed of a pair of elements for processing a differential signal. The power measuring device according to any one of the preceding claims.   6. The amplifier according to claim 1, further comprising an amplifying unit that amplifies an input signal and outputs the amplified signal to a subsequent stage at least one of the subsequent stage of the first filter and the subsequent stage of the second filter. The power measuring device described.

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