JP2016125906A - Millimeter waveband spectrum analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress, without enlarging the device, the occurrence of spurious due to the operation in which frequency conversion processing of a whole predetermined frequency range of a millimeter wave band is performed by sharing with a plurality of mixers.SOLUTION: A switch 30 for assigning the output of a filter 21 to mixers 81 and 82 disposed for respective regions including a measuring frequency has a configuration that selectively interconnects, by sliding, a plurality of connection waveguides 61 and 62 disposed between an input waveguide 41 and a plurality of output waveguides 51 and 52. Of the connection waveguides 61 and 62, in a midway of the connection waveguide 62 for connecting, to the input waveguide 41, the mixer 82 corresponding to a region on at least the high band side, a high-pass filter 70 setting the lower limit of the region as a cutoff frequency is formed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for performing spectrum analysis of a millimeter-wave band signal over a wide band.

  A spectrum analyzer that analyzes the spectrum of a high-frequency signal gives a high-frequency signal and a local signal to the mixer to convert the high-frequency signal to be analyzed into a low frequency band that can be processed digitally, and the difference frequency component Heterodyne type frequency conversion processing is performed.

  The problem here is the frequency characteristics of the mixer, and it is difficult to frequency-convert a wide-band millimeter wave band signal, for example, a signal in a wide range of about 110 to 170 GHz, with one mixer.

  For this reason, it is necessary to divide the frequency range that can be analyzed into a plurality of regions and use a mixer that has frequency characteristics corresponding to each region.

  FIG. 9 shows a configuration example of the spectrum analyzer 1 in which the frequency range that can be analyzed is divided into two regions. The signal Sx to be analyzed input from the input terminal 1a is input to the filter 2 and the measured frequency component To extract. This filter 2 is a band-pass filter whose pass center frequency can be continuously varied within a range of, for example, 110 to 170 GHz, and the measurement frequency range specified by the user is swept by control from the control unit 11.

  The signal Sx ′ extracted by the filter 2 is selectively input to either the first mixer 4 or the second mixer 5 via the switch 3.

  Here, the first mixer 4 is for a low band of 110 to 140 GHz, the second mixer 5 is for a high band of 140 to 170 GHz, and while the measurement frequency to be subjected to spectrum analysis is on the low band side, The switch 3 is controlled so that the output of the filter 2 is input to the first mixer 4 and the output of the filter 2 is input to the second mixer 5 while the measurement frequency is on the high frequency side.

  The first mixer 4 mixes the input signal and the first local signal L1 having the frequency f1 output from the local signal generator 6, and converts the input signal into an intermediate frequency band corresponding to the frequency difference between the two. Similarly, the second mixer 5 mixes the input signal and the second local signal L2 having the frequency f2 output from the local signal generator 6, and converts the input signal into an intermediate frequency band corresponding to the frequency difference between the two. Convert to

  Here, for example, if the frequency f1 of the first local signal L1 is 100 GHz and the frequency f2 of the second local signal L2 is 130 GHz, a signal of 110 to 140 GHz on the lower side of the frequency range that can be analyzed, Both 140 to 170 GHz signals on the high frequency side are converted to an intermediate frequency band of 10 to 40 GHz.

  The outputs of both mixers 4 and 5 are selected by a switch 7 that works in conjunction with the switch 3 and input to the spectrum analyzer 8 at the next stage. This spectrum analysis unit 8 obtains the spectrum of the input signal by converting the signal in the intermediate frequency band of 10 to 40 GHz to a lower intermediate frequency band capable of digital signal processing and performing digital signal processing on this signal. This is displayed on the display unit 9.

  The control unit 11 controls the pass center frequency of the filter 2, the switching control of the switches 3 and 7, the frequency conversion process and spectrum analysis of the spectrum analysis unit 8 according to the measurement frequency range and resolution specified by the operation unit 10. Outputs information necessary for processing.

  In this way, a frequency conversion process that cannot be handled by one mixer is performed by sharing a plurality of mixers, whereby a wideband frequency conversion process can be performed.

  Although different from the configuration of FIG. 9 described above, a spectrum analyzer that performs frequency conversion processing of different frequency bands by sharing a plurality of front ends is disclosed in, for example, Patent Document 1. This document technology gives a common local signal to the first-stage frequency converter of the front end corresponding to two different frequency ranges, and extracts signals of different intermediate frequency bands from the output of the first-stage frequency converter. Compared to the configuration shown in FIG. 9, this method is required for each frequency region including the first intermediate frequency amplifier following the first-stage frequency converter, which complicates the configuration and is disadvantageous in terms of cost.

Japanese Utility Model Publication No. 6-64177

  However, as shown in FIG. 9, in the spectrum analyzer configured to perform a common intermediate frequency band conversion of different frequency regions in the first stage frequency conversion, for example, it is slightly lower than the frequency f1 of the local signal (less than the bandwidth of the intermediate frequency). If there is a signal at the frequency f3, the difference frequency Δf = f1−f3 enters the intermediate frequency band, and it appears as if the signal exists at the frequency of f1 + Δf (image spurious).

  Similarly, if there is a signal at a frequency f4 slightly lower than the frequency f2 of the local signal (less than the bandwidth of the intermediate frequency), the difference frequency Δf ′ = f2−f4 enters the intermediate frequency band, It looks as if a signal exists (image spurious) at a frequency of f2 + Δf ′.

  Actually, the filter 2 is inserted in front of both the mixers 4 and 5, and the image spurious can be suppressed by the passband characteristic of the filter 2, but the selection characteristic of the bandpass filter 2 has a limit, If the signal levels of the above-described frequencies f3 and f4 are high, the signal cannot be sufficiently attenuated and accurate spectrum analysis cannot be performed.

  As a method for solving this, a high-pass filter having a cutoff frequency of 110 GHz is inserted into the input portion of the first mixer 4 on the low frequency side to greatly attenuate the signal component lower than the local signal L1, and the second high frequency side second It is conceivable to insert a high-pass filter having a cutoff frequency of 140 GHz into the input section of the mixer 5 to greatly attenuate signal components lower than the local signal L2.

  However, when these high-pass filters are inserted between the switch 3 and the mixers 4 and 5, there is a problem that the apparatus becomes large. In particular, in the millimeter wave band of 100 GHz or more as described above, a waveguide structure is generally used as a signal path, and in addition to the filter 2 and the switch 3, these high-pass filters are configured with a waveguide structure. In view of this, the size of the device will become larger and larger.

  The present invention solves this problem and can suppress the occurrence of spurious noise caused by sharing frequency conversion processing for the entire predetermined frequency range of the millimeter wave band by a plurality of mixers without increasing the size of the apparatus. It aims to provide a millimeter-wave band spectrum analyzer.

In order to achieve the above object, a millimeter waveband spectrum analyzer according to claim 1 of the present invention comprises:
A filter (21) for receiving a signal within a predetermined frequency range of the millimeter wave band and extracting a signal component of a measurement frequency swept within the predetermined frequency range;
A plurality of mixers (81, 82) for dividing the predetermined frequency range into a plurality of regions, and converting the signals of the respective regions into predetermined intermediate frequency bands;
A switch (30) for selectively outputting the output of the filter to a mixer corresponding to a region including the measurement frequency among the plurality of mixers;
In a millimeter wave band spectrum analyzer having a spectrum analysis unit (90) that receives a signal converted into the intermediate frequency band by the plurality of mixers and performs spectrum analysis on the measurement frequency,
The switch,
A base (31);
An input waveguide block (40) fixed to the base portion and formed so that an input waveguide (41) that receives and propagates the output signal of the filter is continuous from the first end face to the second end face; ,
A plurality of output waveguides (51, 52, 53) fixed to the base portion and respectively connected to the plurality of mixers are provided from a third end face parallel to the second end face of the input waveguide block. An output waveguide block (50) formed to be continuous to the fourth end face;
A plurality of connection waveguides (61, 62, 63), which are supported by the base portion and selectively connect between the input waveguide and the plurality of output waveguides, are provided on the input waveguide block. The input waveguide block and the output are formed so as to be continuous from a fifth end surface facing the second end surface to a sixth end surface facing the third end surface of the output waveguide block. A sliding waveguide relative to the waveguide block, and a connection waveguide block (60) for selectively connecting the input waveguide and the plurality of output waveguides at a plurality of different positions;
A high-pass filter having a cut-off frequency at the lower limit of the connection waveguide for connecting the input waveguide to a mixer corresponding to at least the high-frequency region among the plurality of connection waveguides of the switch (70, 71, 72) is formed.

The millimeter waveband spectrum analyzer according to claim 2 of the present invention is the millimeter waveband spectrum analyzer according to claim 1,
The filter has a pair of radio wave half mirrors (25A, 25B) that reflect and transmit a part of the electromagnetic wave in a waveguide that propagates the electromagnetic wave in the predetermined frequency range in a single mode, A structure that selectively allows a frequency component determined by the distance between the pair of half mirrors to pass, and is the lowest of the plurality of regions within the waveguide and outside the pair of radio wave half mirrors. A high-pass filter (75) having a lower limit of the region on the region side as a cutoff frequency is provided.

The millimeter waveband spectrum analyzer according to claim 3 of the present invention is the millimeter waveband spectrum analyzer according to claim 1 or 2,
Positions surrounding the openings of the input waveguide on the second end face side of the input waveguide block of the switch, and openings of the plurality of output waveguides on the third end face side of the output waveguide block. In order to prevent leakage of electromagnetic waves from the gaps between the respective blocks at positions surrounding the openings of the plurality of connection waveguides on the fifth end face side and the sixth end face side of the connection waveguide block A groove (45A, 45B, 55A, 55B, 56A, 56B, 65A, 65B, 66A, 66B, 67A, 67B, 68A, 68B) having a depth corresponding to 1/4 of the in-tube wavelength of the leakage prevention target frequency is provided. It is characterized by that.

  Thus, in the millimeter waveband spectrum analyzer of the present invention, a switch that distributes the output of the filter to the mixer provided for each region including the measurement frequency is provided between the input waveguide and the plurality of output waveguides. A structure in which a plurality of provided connection waveguides are slid and selectively connected, and the connection waveguide for connecting at least the mixer corresponding to the region on the high frequency side to the input waveguide among the connection waveguides. In addition, a high-pass filter having a lower limit of the region as a cutoff frequency is formed.

  As described above, since the high-pass filter is provided in the connection waveguide of the switch for switching the signal path, image spurious can be effectively suppressed without increasing the size of the apparatus.

  Further, if a low-pass high-pass filter is provided in the filter waveguide as in claim 2 of the present invention, there is no need to provide a high-pass filter in the low-pass connection waveguide on the switch side, and the switch structure Simplify.

  Further, as in claim 3, a groove having a depth corresponding to ¼ of the in-tube wavelength of the electromagnetic wave to be prevented from leaking is provided around the opening of the waveguide between the blocks of the switch. Electromagnetic leakage to the unintended waveguide through the gap can be prevented, and high isolation can be obtained.

Overall configuration diagram of an embodiment of the present invention Specific configuration diagram of the main part of the embodiment The figure which shows the example of the characteristic of the high pass filter provided in the filter Operation explanatory diagram of the main part of the embodiment The figure which shows the characteristic example of the high pass filter which is provided in the switch The figure which shows the end surface of the principal part of embodiment Operation explanatory diagram of the embodiment Switch structure diagram when the frequency range that can be analyzed is divided into three regions Configuration diagram of conventional equipment

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the overall configuration of a millimeter waveband spectrum analyzer 20 (hereinafter simply referred to as a spectrum analyzer 20) according to an embodiment of the present invention.

  In FIG. 1, the analysis target signal Sx input to the input terminal 20 a is input to the filter 21. The filter 21 receives a signal in a predetermined frequency range (for example, 110 to 170 GHz) that can be analyzed in the millimeter wave band, and extracts a signal having a measurement frequency that is swept within the predetermined frequency range. A pair of electromagnetic waves having a predetermined aperture (for example, about 2 mm × 1 mm) for propagating electromagnetic waves in a predetermined frequency range in a single mode (TE10 mode) and reflecting part of the electromagnetic waves and transmitting part of the electromagnetic waves. The radio wave half mirrors 25A and 25B are arranged so as to face each other, and a Fabry-Perot type band-pass filter that selectively passes a component of a frequency (resonance frequency) determined by the distance d between the pair of radio wave half mirrors 25A and 25B. The distance d between the pair of radio wave half mirrors 25A and 25B can be changed by the distance varying mechanism 26, and the control is performed by the control unit 100 described later.

  FIG. 2 shows a specific structural example of the filter 21. For example, the radio wave half mirror 25A is installed so as to block one end of the inner waveguide 22 that propagates electromagnetic waves in a range of 110 to 170 GHz in a single mode. The radio wave half mirror 25B is fixed inside the first outer waveguide 23 that receives one end side of the inner waveguide 22 with a slight gap therebetween.

  Here, the inner waveguide 22 can be moved in the length direction with respect to the first outer waveguide 23 by the driving device 26a, and thereby the interval d between the radio wave half mirrors 25A and 25B is set. Variable. However, since it is not preferable to directly connect an external circuit to the movable inner waveguide 22, the second outer waveguide 27 for connecting the outer circuit is used, and the other end side of the inner waveguide 22 is always second. The signal input path (not shown) from the input terminal 20 a is connected to the second outer waveguide 27 so as to exist inside the outer waveguide 27.

  Further, within the waveguide 21a of the filter 21, outside the radio wave half mirrors 25A and 25B, for example, inside the second outer waveguide 27, a predetermined frequency range that can be analyzed (characteristic F in FIG. For example, a high-pass filter 75 having a cut-off frequency as a lower limit (110 GHz) of the lowest frequency region when 110 to 170 GHz) is divided into a plurality of regions is provided.

  The high-pass filter 75 using a waveguide can be configured by narrowing the diameter (particularly the long side dimension) of the waveguide. Here, the relationship between the waveguide diameter (long side a × short side b) and the cut-off frequency fc10 in the TE10 mode is expressed as fc10 = c / 2a, where c is the speed of light. If the lower limit (cut-off frequency fc10) of the region on the band side is set to 110 GHz, the long side a of the waveguide diameter may be set to about c / 2fc10≈1.36 mm. Since the short side has little influence on the cut-off frequency, it may be narrowed at a ratio matched to the long side. However, since the reflection of the electromagnetic wave occurs when the diameter of the waveguide is abruptly narrowed, the reflection is suppressed by gradually changing the diameter before and after the taper.

  In this way, by providing the high-pass filter 75 that uses a part of the waveguide of the filter 21 to set the lower limit of the low-frequency region to the cutoff frequency, the low-frequency image is used in the frequency conversion processing described later. The occurrence of spurious can be effectively suppressed. As a method of changing the pass center frequency of the filter 21, the filter 21 is discretely performed in a predetermined step while covering the measurement frequency while continuously (in fact, depending on the resolution of the driving mechanism) in conjunction with the sweep of the set measurement frequency. Sometimes.

  The output signal of the filter 21 is input to the switch 30. The switch 30 has a predetermined frequency range that can be analyzed, for example, 110 to 170 GHz, and is divided into a low region of 110 to 140 GHz and a high region of 140 to 170 GHz in consideration of frequency characteristics of mixers 81 and 82 described later. However, the input signal is divided into two output paths according to the region including the measurement frequency. In order to efficiently switch the millimeter wave signal path, the electromagnetic wave is guided by a waveguide surrounded by a metal wall. It has a waveguide structure that propagates.

  In this switch 30, the input waveguide block 40 is fixed to one end on the base portion 31, the output waveguide block 50 is fixed to the other end, and the connection waveguide block 60 is disposed therebetween. It has a structure.

  The input waveguide block 40 is formed in a rectangular parallelepiped shape so that an input waveguide 41 having a predetermined diameter that receives and propagates the output signal of the filter 21 is continuous from the first end face 40a to the second end face 40b on the opposite side. Is formed.

  Similarly to the input waveguide block 40, the output waveguide block 50 is also formed in a rectangular parallelepiped shape, and two output waveguides 51 and 52 having two predetermined diameters constituting two signal paths are included in the input waveguide block 40. The second end face 40a is formed so as to continue from the third end face 50a facing in parallel to the second end face 40a to the fourth end face 50b on the opposite side.

  The connecting waveguide block 60 has a rectangular parallelepiped shape, the fifth end surface 60a is opposed to the second end surface 40b of the input waveguide block 40 with a slight gap therebetween, and the third end surface of the output waveguide block 50 is arranged. It is supported by the base 31 with the sixth end face 60b facing the end face 50b with a slight gap, and selectively connects the input waveguide 41 and the two output waveguides 51, 52. For this purpose, connection waveguides 61 and 62 having two predetermined diameters are formed so as to continue from the fifth end surface 60a to the sixth end surface 60b. The connection waveguide block 60 is slidable with respect to the input waveguide block 40 and the output waveguide block 50, and the input waveguide 41 and the output waveguide 51 are at two different positions. , 52 are selectively connected. The apertures of the input waveguide 41, the output waveguides 51 and 52, and the connection waveguides 61 and 62 are set equal to about 2 mm × 1 mm.

  The positional relationship between the waveguides of the switch 30 shown in FIG. 1 will be described. Two output waveguides 51 and 52 are formed symmetrically with an extension line of the input waveguide 41 interposed therebetween, and two connection waveguides 61 and 62 are formed. The opening on the fifth end face 60a side is provided at the same distance L across the extension line of the input waveguide 41, and the opening on the sixth end face 60b side of the two connecting waveguides 61 and 62 is output. The waveguides 51 and 52 are provided at the same distance L on the outer side from the opening on the third end face 50a side.

  Accordingly, when the connection waveguide block 60 is moved by L in the width direction (Y direction) from the position shown in FIG. 1, between the input waveguide 41 and one output waveguide 51 as shown in FIG. Are connected via one connection waveguide 61. When the connection waveguide block 60 is moved by -2L in the width direction (Y direction) from this state, as shown in FIG. The input waveguide 41 and the other output waveguide 52 are connected via the other connection waveguide 62.

  Note that the connection waveguide block 60 is slid and moved by, for example, a driving device 35 provided on the lower surface side of the base portion 31. The drive device 35 can employ a structure in which, for example, a stepping motor is used as a drive source, and the rotational force is converted into a linear motion and transmitted to a member (not shown) that supports the connection waveguide block 60. The structure is arbitrary. The driving device 35 is controlled by the control unit 100 described later, and when the measurement frequency to be subjected to spectrum analysis is on the lower side of the two regions described above, the connecting waveguide block 60 is shown in FIG. When the position is a) and the measurement frequency is on the higher side of the two regions described above, the connecting waveguide block 60 is driven to the position shown in FIG.

  Of the two connection waveguides 61 and 62 of the connection waveguide block 60, the connection waveguide 62 for outputting a signal on the high frequency side has a high frequency (in this case 140) as shown by the characteristic G in FIG. A high-pass filter 70 having a cutoff frequency of a frequency (140 GHz) that is a lower limit of .about.170 GHz is formed.

  The high-pass filter 70 can be configured by narrowing the intermediate aperture of the connection waveguide 62, similarly to the low-pass high-pass filter 75 provided in the filter 21. For example, if the cutoff frequency is 140 GHz, What is necessary is just to make the long side dimension of a caliber into about 1.07 mm, and just to make a short side side narrow according to it. However, when the aperture of the connection waveguide 62 is abruptly narrowed, electromagnetic waves are reflected. Therefore, the aperture is gradually changed in a tapered shape to suppress the reflection.

  As described above, the high-pass filter 70 having the lower limit of the high-frequency region as the cutoff frequency is provided in the connection waveguide 62 that passes the high-frequency signal among the connection waveguides 61 and 62 of the switch 30. Thus, it is possible to effectively suppress the occurrence of high-frequency image spurious in the frequency conversion process described later.

  As described above, in the switch 30 that switches the waveguide by moving the connection waveguide block 60, it is necessary to provide a gap necessary for the movement, and electromagnetic waves leak into the unintended waveguide through this gap. It is expected that the isolation will decrease.

  In order to solve this, the switch 30 of the spectrum analyzer 20 according to the embodiment includes, as shown in FIG. 6, waveguides 41, 51, 52, 61, 62 on the end face side of each block facing each other with a gap therebetween. Double grooves having a predetermined depth that are continuous in a frame shape are provided so as to surround the openings.

  That is, as shown in FIG. 6A, the groove 45A having a predetermined depth D is formed in a frame shape at a position away from the opening of the input waveguide 41 on the second end face 40b of the input waveguide block 40 by a predetermined distance Q1. A groove 45B having a predetermined depth D ′ is formed in a frame shape at a position away from the groove 45A by a predetermined distance Q2.

  The depths D and D ′ of the grooves 45A and 45B are set to ¼ of the in-tube wavelength of the electromagnetic wave to be prevented from leaking, and the electromagnetic waves leaking into the gap from the opening of the input waveguide 41 and reaching the grooves 45A and 45B The phases of the electromagnetic waves that reciprocated inside the grooves 45A and 45B and returned to the entrance of the grooves are reversed, thereby canceling each other and moving outside the electromagnetic wave grooves in the band centered on the frequency corresponding to the depths D and D '. Prevent leakage. Here, the groove is doubled to enhance the leakage prevention effect. However, one groove or three or more grooves may be provided, and the groove depths D and D ′ are made equal to each other to leak. There are a method of increasing the attenuation with respect to the wave and a method of widening the leakage prevention effect by setting the groove depths D and D 'to different values, and these can be used in combination.

  Further, as shown in FIG. 6B, the third end face 50a side of the output waveguide block 50 also has a predetermined depth at a position separated from the openings of the output waveguides 51 and 52 by a predetermined distance Q1. Grooves 55A and 56A having a depth D are formed in a frame shape, and grooves 55B and 56B having a predetermined depth D 'are formed in a frame shape at positions separated from the grooves 55A and 56A by a predetermined distance Q2.

  Further, as shown in FIG. 6C, the fifth end face 60a side of the connection waveguide block 60 is also provided at a predetermined depth Q1 away from the openings of the connection waveguides 61 and 62, respectively. Grooves 65A and 66A having a depth D are formed in a frame shape, and grooves 65B and 66B having a predetermined depth D ′ are formed in a frame shape at positions separated from the grooves 65A and 66A by a predetermined distance Q2, respectively, and the sixth end face 60b. Also on the side, grooves 67A and 68A having a predetermined depth D are formed in a frame shape at positions separated by a predetermined distance Q1 from the openings of the connection waveguides 61 and 62, respectively, and positions separated from the grooves 67A and 68A by a predetermined distance Q2 respectively. In addition, grooves 67B and 68B having a predetermined depth D 'are formed in a frame shape.

Incidentally, the numerical examples of these grooves, the depth D of 140GHz Tosureba groove center transmission frequency of the waveguide, both ^{D ', (300 × 10 6} /140 × 10 9) / 4 ≒ 0 .54 mm may be used. The width of each groove is about 0.2 mm. FIG. 6E is a cross-sectional view taken along line AA of FIG.

  Further, the distance Q1 from the opening of each waveguide to the inner groove is ¼ (for example, an in-tube wavelength of a frequency (for example, 75 GHz) sufficiently lower than the lower limit of the transmission frequency region (for example, 110 to 170 GHz) of the switch 30. 1 mm), the section from the waveguide opening to the inner groove prevents reflection due to functioning as a band rejection filter from occurring in the transmission frequency region.

  Further, the distance Q2 from the inner groove to the outer groove is set to be an odd multiple of 1/4 (for example, 0.54 mm) of the in-tube wavelength of the transmission center frequency (for example, 140 GHz). Between the grooves, it functions as a band rejection filter to enhance the electromagnetic wave leakage prevention effect.

  Note that the upper surface, side surfaces, and lower surface of the switch 30 are covered with a metal case (not shown), and the upper surface and side surfaces of the connection waveguide block 60 are not in contact with the inner wall of the metal case. .

  As described above, in the switch 30 according to the embodiment, since the groove for preventing electromagnetic wave leakage is provided at a position surrounding the opening of the waveguide on the end faces facing each other with the gap between the blocks, even if the gap is provided between the blocks, the electromagnetic wave is provided. Leakage and the reduction of isolation due to this can be prevented, and the durability is not lowered due to wear as in the contact type, and high durability can be provided.

  Mixers 81 and 82 are connected to the openings of the output waveguides 51 and 52 on the fourth end face 50b side of the output waveguide block 50 of the switch 30, respectively.

  Here, the mixer 81 connected to one output waveguide 51 is for low frequency (110 to 140 GHz), and a low frequency signal output from the output waveguide 51 and a predetermined frequency f1 (for example, f1). = 100 GHz) and the first local signal L1 are mixed to convert the input signal into a predetermined intermediate frequency band (for example, 10 to 50 GHz).

  The mixer 82 connected to the other output waveguide 52 is for high frequency (140 to 170 GHz), and a high frequency signal output from the output waveguide 52 and a predetermined frequency f2 (for example, f2 = The second local signal L2 of 150 GHz) is mixed and the input signal is converted into a predetermined intermediate frequency band (for example, 10 to 50 GHz).

  These mixers 81 and 82 are of, for example, a diode mixing type, and are assumed to be substantially flat and have practical conversion efficiency in each band.

  The local signals L1 and L2 are output from the local signal generator 85. In order to generate a local signal exceeding 100 GHz, for example, a stable signal in the order of several tens of GHz is multiplied to obtain an order equal to the local signal frequency. A harmonic signal is generated, and a signal of a required order is extracted from the harmonic signal using a filter having the same configuration as the filter 21.

  The outputs of the mixers 81 and 82 are selected by a switch 87 that is linked to the switch 30 and input to the spectrum analysis unit 90. Since this switch 87 has a frequency as low as several tens of GHz, the switch 87 is not a waveguide type like the switch 30 but can be constituted by a small relay type or a semiconductor switch.

  The spectrum analysis unit 90 performs spectrum analysis on the signal converted into the intermediate frequency band. The frequency conversion unit 91 converts the signal in this frequency band into a low frequency band that can be processed with digital signals, and the frequency conversion unit. A spectrum detection unit 92 that detects the spectrum of the input signal based on the signal converted to a lower frequency by 91 is provided. The frequency converter 91 performs the heterodyne frequency conversion process while sweeping the frequency of the local signal, so that a signal in a desired analysis frequency range designated by the user is continuously applied to a frequency band in which digital processing is possible. It is configured to convert, and the sweep range of the frequency of the local signal is controlled so as to be interlocked with the pass center frequency of the filter 21. The spectrum detecting unit 92 obtains the spectrum of the input signal by converting the output of the frequency converting unit 91 into a digital signal and performing a fast Fourier transform process or the like. The measurement frequency to be subjected to spectrum analysis is determined by the analysis frequency information in the spectrum detector 92, the frequency of the local signal used in the frequency converter 91, and the frequencies of the local signals L1 and L2 given to the mixers 81 and 82.

  Information on the spectrum of the input signal detected by the spectrum analysis unit 90 is output to the display unit 95. For example, a spectrum waveform is displayed on a screen having the measurement frequency as the horizontal axis and the signal level as the vertical axis.

  The operation unit 96 is for a user to specify information such as a desired measurement frequency range and frequency resolution, and the control unit 100 controls each unit based on the specified information. The control unit 100 performs processing such as sweeping of the pass center frequency of the filter 21, switching of the switches 30 and 87, and transmission of information necessary for analysis to the spectrum analysis unit 90 according to the designated measurement frequency range.

  Here, when the measurement frequency range specified by the operation unit 96 is included in only one of the two regions, for example, 110 to 130 GHz of 110 to 140 GHz on the low frequency side is specified as the measurement frequency range. In this case, the input waveguide 41 and the output waveguide 51 of the switch 30 are connected to each other via the connection waveguide 61 and the switch 87 is connected to the mixer 81 side. Swept up to 130 GHz in a predetermined step, signal components up to 110 to 130 GHz of the input signal Sx are converted to an intermediate frequency band of 10 to 30 GHz, and the spectrum analysis unit 90 obtained the signal in the intermediate frequency band. For example, the spectrum is placed on the frequency axis of 110 to 130 GHz of the display unit 95 as shown in FIG. Cause shown.

  Here, assuming that a 90 GHz signal, for example, is included in the input signal Sx at a relatively large level, conventionally, the 90 GHz signal is converted to 10 GHz by a local signal L1 of 100 GHz, as if it exists at 110 GHz. 7 is displayed at a position of 110 GHz as indicated by the dotted line in FIG. 7A. This spectrum analyzer 20 uses a high-pass filter with the lower frequency lower limit frequency as a cutoff frequency. 75 is provided in the filter 21, and the 90 GHz signal can be greatly attenuated by the high-pass filter 75, so that it is possible to prevent the image spurious spectrum indicated by the dotted line from being displayed.

  On the other hand, when 150 to 170 GHz of 140 to 170 GHz on the high frequency side is specified as the measurement frequency range, the control unit 100 connects the input waveguide 41 and the output waveguide 52 of the switch 30 to the connection waveguide. 62, the switch 87 is connected to the mixer 82 side, the center frequency of the filter 21 is swept in a predetermined step from 150 GHz to 170 GHz, and the signal from 150 to 170 GHz of the input signal is swept. The component is converted to an intermediate frequency band of 20 to 40 GHz, and the spectrum obtained by the spectrum analysis unit 90 with respect to the signal of the intermediate frequency band is, for example, 150 to 170 GHz of the display unit 95 as shown in FIG. Display on the frequency axis.

  Here, assuming that the input signal Sx includes, for example, a 110 GHz signal at a relatively large level, conventionally, the 110 GHz signal is converted to 20 GHz by the 130 GHz local signal L2 and exists at 150 GHz. 7 is displayed at a position of 150 GHz as indicated by the dotted line in FIG. 7B. In this spectrum analyzer 20, a high pass having a lower frequency 140 GHz on the high frequency side as a cutoff frequency is displayed. Since the filter 70 is provided in the connection waveguide 62 of the switch 30 and the 110 GHz signal can be greatly attenuated by the high-pass filter 70, it is possible to prevent the display of the image spurious spectrum indicated by the dotted line.

  When the entire frequency range of 110 to 170 GHz that can be analyzed is designated as the measurement frequency range, the control unit 100 first sets the connection waveguide 61 between the input waveguide 41 and the output waveguide 51 of the switch 30. And the switch 87 is connected to the mixer 81 side, the center frequency of the filter 21 is swept in a predetermined step from 110 GHz to 140 GHz, and signal components of 110 to 140 GHz of the input signal are obtained. The signal is converted to an intermediate frequency band of 10 to 40 GHz, and the spectrum analysis unit 90 performs spectrum analysis on the signal in the intermediate frequency band. Subsequently, the input waveguide 41 and the output waveguide 52 of the switch 30 are connected to each other via the connection waveguide 62, the switch 87 is connected to the mixer 82 side, and the pass center frequency of the filter 21 is 140 GHz. To 170 GHz in a predetermined step, the signal component of 140 to 170 GHz of the input signal is converted to an intermediate frequency band of 10 to 40 GHz, and the spectrum analysis unit 90 performs spectrum analysis on the signal of the intermediate frequency band. The spectrum obtained by the spectrum analysis is displayed on the frequency axis of 110 to 170 GHz of the display unit 95, for example, as shown in FIG.

  Even in this case, a frequency component lower than the predetermined frequency range that can be analyzed can be suppressed by the high-pass filter 75 provided in the filter 21, and the image spurious is not displayed large.

  Also, when there is a relatively large level signal at a low frequency, for example, 120 GHz, the spectrum of this signal is converted into an intermediate frequency band by the frequency conversion processing on the low frequency side, as shown in FIG. Although it is recognized as a spectrum with a frequency of 120 GHz, at the stage of moving to the frequency conversion processing on the high frequency side, conventionally, this 120 GHz signal is converted to 10 GHz by the local signal L2 of 130 GHz, as if 140 GHz Is detected as a spectrum of a signal existing in the signal and displayed at a position of 140 GHz as shown by a dotted line in FIG. However, in the spectrum analyzer 20, a high-pass filter 70 having a cutoff frequency of the lower limit frequency 140 GHz on the high frequency side is provided in the connection waveguide 62 of the switch 30, and the high-pass filter 70 greatly attenuates a 120 GHz signal. Therefore, it is possible to prevent the 120 GHz image spurious indicated by the dotted line from being displayed.

  As described above, in the spectrum analyzer 20 of the embodiment, among the image spurious generated by the configuration in which the predetermined frequency range that can be analyzed is divided into a plurality of regions, and the frequency conversion for the signals in each region is performed by a plurality of mixers suitable for the region. Generation of image spurious generated by frequency conversion on at least the high frequency side is suppressed by a high-pass filter 70 provided in the connection waveguide 62 of the switch 30 used for switching the mixer, and the image can be enlarged without increasing the size of the entire apparatus. Spurious can be effectively suppressed.

  In this embodiment, the high-pass filter 75 for suppressing image spurious on the low frequency side is provided in the waveguide of the filter 21, but it may be provided in the connection waveguide 61 on the low frequency side of the switch 30, A high-pass filter 75 may be provided in both the waveguide of the filter 21 and the connection waveguide 61 of the switch 30.

  In this embodiment, the predetermined frequency range that can be analyzed is divided into two regions, a low region and a high region, and the frequency conversion of each region is shared by two mixers. The present invention can also be applied to a spectrum analyzer having a configuration in which a plurality of mixers share the frequency conversion of each region.

  For example, when dividing into three regions, as shown in FIG. 8A, as the switch 30, three output waveguides 51 to 53 are provided in the output waveguide block 50, and the connection waveguide block 60 is also provided. Three connection waveguides 61 to 63 are provided. Here, the intervals between the output waveguides 51 to 53 are made equal, the central output waveguide 52 is positioned on the extension line of the input waveguide 41, and the state in which the central connection waveguide 62 is connected therebetween is defined as an intermediate region. The corresponding connection position. Further, the opening positions of the connection waveguides 61 and 63 on the input waveguide 40 side are a predetermined distance L away from the opening position of the central connection waveguide 62, and the connection waveguides 61 and 63 on the output waveguide 50 side. Are spaced apart from the opening positions of the output waveguides 51 and 53 by a predetermined distance L. Although not shown, it is assumed that the switch 30 shown in FIG. 8 is also provided with a groove for preventing electromagnetic wave leakage as shown in FIG. 6 in each waveguide.

  Therefore, if the connection waveguide block 60 is moved by L in the Y direction from the state of FIG. 8A, the connection between the input waveguide 41 and the output waveguide 51 is connected as shown in FIG. 8B. If it becomes a connection position corresponding to the low band connected via the waveguide 61 and the connection waveguide block 60 is moved by -L in the Y direction from the state of FIG. 8A, as shown in FIG. In addition, the input waveguide 41 and the output waveguide 53 become a connection position corresponding to a high band connected via the connection waveguide 63.

  Further, by providing the connection waveguides 62 and 63 corresponding to at least the intermediate region and the high region with the high-pass filters 71 and 72 having the lower limit of each region as a cut-off frequency, image spurious can be suppressed in the same manner as described above. it can.

  20... Millimeter wave spectrum analyzer, 21... Filter, 25 A, 25 B .. radio wave half mirror, 30... Switch, 31. , 40b... End face, 41... Input waveguide, 45A, 45B... Groove, 50... Output waveguide block, 50a, 50b .. end face, 51, 52, 53 ... output waveguide, 55A, 55B 56A, 56B ... groove, 60 ... connecting waveguide block, 60a, 60b ... end face, 61,62,63 ... connecting waveguide, 55A, 55B, 56A, 56B, 57A, 57B, 58A, 58B ...... Groove, 70, 71, 72, 75..High-pass filter, 81, 82..Mixer, 85 .... Local signal generator, 87 .... Switch, 90..Spectrum analysis unit, 95 .. Radical 113, 96 ...... operation unit, 100 ...... control unit

Claims (3)

A filter (21) for receiving a signal within a predetermined frequency range of the millimeter wave band and extracting a signal component of a measurement frequency swept within the predetermined frequency range;
A plurality of mixers (81, 82) for dividing the predetermined frequency range into a plurality of regions, and converting the signals of the respective regions into predetermined intermediate frequency bands;
A switch (30) for selectively outputting the output of the filter to a mixer corresponding to a region including the measurement frequency among the plurality of mixers;
In a millimeter wave band spectrum analyzer having a spectrum analysis unit (90) that receives a signal converted into the intermediate frequency band by the plurality of mixers and performs spectrum analysis on the measurement frequency,
The switch,
A base (31);
An input waveguide block (40) fixed to the base portion and formed so that an input waveguide (41) that receives and propagates the output signal of the filter is continuous from the first end face to the second end face; ,
A plurality of output waveguides (51, 52, 53) fixed to the base portion and respectively connected to the plurality of mixers are provided from a third end face parallel to the second end face of the input waveguide block. An output waveguide block (50) formed to be continuous to the fourth end face;
A plurality of connection waveguides (61, 62, 63), which are supported by the base portion and selectively connect between the input waveguide and the plurality of output waveguides, are provided on the input waveguide block. The input waveguide block and the output are formed so as to be continuous from a fifth end surface facing the second end surface to a sixth end surface facing the third end surface of the output waveguide block. A sliding waveguide relative to the waveguide block, and a connection waveguide block (60) for selectively connecting the input waveguide and the plurality of output waveguides at a plurality of different positions;
A high-pass filter having a cut-off frequency at the lower limit of the connection waveguide for connecting the input waveguide to a mixer corresponding to at least the high-frequency region among the plurality of connection waveguides of the switch (70, 71, 72) A millimeter-wave band spectrum analyzer characterized by being formed.   The filter has a pair of radio wave half mirrors (25A, 25B) that reflect and transmit a part of the electromagnetic wave in a waveguide that propagates the electromagnetic wave in the predetermined frequency range in a single mode, A structure that selectively allows a frequency component determined by the distance between the pair of half mirrors to pass, and is the lowest of the plurality of regions within the waveguide and outside the pair of radio wave half mirrors. The millimeter waveband spectrum analyzer according to claim 1, further comprising a high-pass filter (75) having a cutoff frequency at a lower limit of the region on the region side.   Positions surrounding the openings of the input waveguide on the second end face side of the input waveguide block of the switch, and openings of the plurality of output waveguides on the third end face side of the output waveguide block. In order to prevent leakage of electromagnetic waves from the gaps between the respective blocks at positions surrounding the openings of the plurality of connection waveguides on the fifth end face side and the sixth end face side of the connection waveguide block A groove (45A, 45B, 55A, 55B, 56A, 56B, 65A, 65B, 66A, 66B, 67A, 67B, 68A, 68B) having a depth corresponding to 1/4 of the in-tube wavelength of the leakage prevention target frequency is provided. 3. The millimeter waveband spectrum analyzer according to claim 1, wherein the millimeter waveband spectrum analyzer.

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