Abstract:
Provided is a non-radiative dielectric (NRD) waveguide modulator having a waveguide type hybrid coupler, in which by forming a waveguide type 180° hybrid coupler and waveguides as a single body, the structure is simplified and manufacturing processes are reduced such that consistency of characteristics is maintained, manufacturing time and cost are reduced, and consequently, manufacturability is improved. The NRD waveguide modulator comprises a conducting housing which comprises a lower conducting plate and an upper conducting plate; a hybrid coupler which is processed in the form of conduit lines inside the conducting housing, and comprises a ring portion and a plurality of waveguides extended from the ring portion in the radius direction, in which according to the phase differences of the waveguides, a local oscillation signal input from a local oscillator through any one side waveguide is distributed to at least two waveguides and propagated; a modulator which comprises dielectric line which is disposed in an internal space formed in the conducting housing and receives a local oscillation signal from the hybrid coupler and a diode mount which is disposed on a predetermined point and on which a Schottky diode is mounted; and a termination which is connected to an isolation port that is an end of any one waveguide of the hybrid coupler and terminates a signal reflected by the modulator by consuming the signal internally.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a modulator using a non-radiative dielectric waveguide, and more particularly, to a non-radiative dielectric waveguide modulator having a waveguide type hybrid coupler in which a hybrid coupler, which distributes and propagates a local oscillation signal entered from a local oscillator to a mixer of a reception unit and a modulator, is formed with conduit-shape waveguides in a conducting housing, and dielectric lines combined with the waveguides as a single body are accommodated and disposed in the conducting housing such that the structure is simplified and the manufacturing processes are reduced.  
         [0003]     2. Description of the Related Art  
         [0004]     Recently, research efforts have been made to implement wireless communications using transceivers in a millimeter wave band area for high speed large capacity wireless communications. As wireless communications system used in a millimeter wave band, systems mainly using waveguides had been widely used, but more recently, thanks to the semiconductor technology development, the system has been developed as a single chip called monolithic microwave integrated circuit (MMIC). The method using a waveguide, which can be referred to as a hybrid type, falls behind the MMIC in mass production and market price, but is more advantageous in small volume production.  
         [0005]     Since a non-radiative dielectric (NRD) waveguide having less transmission loss than this method using a waveguide has been introduced first in the early 1980s, a lot of efforts to commercialize the NRD waveguide have been made and transceivers using the NRD waveguide have been actively manufactured. The NRD waveguide transfers a signal at a low loss rate through a longitudinal section magnetic (LSM) mode and by using this NRD waveguide, a circuit which provides easy compatibility with existing waveguides while maintaining the advantages of both type waveguides.  
         [0006]      FIGS. 1   a  and  1   b  are a perspective view and a plan view, respectively, of the structure of a prior art modulator using NRD waveguides.  
         [0007]     As shown, the prior art modulator comprises a directional coupler  10 , a circulator  20 , and a modulator  30 . The directional coupler  10  transfers a local oscillation signal to a transmission unit and a reception unit in a transceiver, and is formed by disposing a pair of dielectric lines  12  and  14  between an upper conducting plate  40  and a lower conducting plate  50 . At this time by adjusting the gap between the two dielectric lines  12  and  14 , the coupling amount of the directional coupler  10  is adjusted and in order to obtain a wider bandwidth, the dielectric lines  12  and  14  should be curved as shown. A local oscillation signal generated in a local oscillator (not shown) is entered into a signal input port  12   a , and this signal is propagated to the circulator  20  and a mixer port of the reception unit, respectively, by the directional coupler  10 . An isolation port of this directional coupler  10  should be terminated by using a termination  16  and this termination  16  is formed by inserting a resisting sheet  16  into the dielectric line  14 . Because it is very difficult to manufacture this curved dielectric line  14  and termination  16  and to obtain uniform characteristics, these are not appropriate for mass production.  
         [0008]     The circulator  20  is a unidirectional device providing a signal path only in one direction. This circulator  20  is connected to three dielectric lines  12 ,  22 , and  24  so that the local oscillation signal transferred from the directional coupler  10  is transferred to the modulator  30 . More specifically, the local oscillation signal is input to the circulator  20  through the directional coupler  10 , this signal is entered into the modulator  30  by the circulator  20 , and the modulated signal reflected at the modulator  30  is output to a modulated signal output port  24   a.    
         [0009]     This circulator  20  is formed by disposing the three dielectric lines  12 ,  22 , and  24  at each 120° angle interval, and disposing an annular dielectric resonator  26  at the point where the three dielectric lines  12 ,  22 , and  24  come together. Ferrite or rubber magnets are placed on the top and bottom of the annular dielectric resonator  26  and then, by using a permanent magnet, are magnetized such that the unidirectional characteristic can be obtained. In order to suppress generation of a longitudinal section electric (LSE) mode occurring in these three dielectric lines  12 ,  22 , and  24  in addition to the LSM mode that is the basic mode, an LSE mode suppressor is inserted into the center of the dielectric lines  12 ,  22 , and  24 . Because it is difficult to manufacture the circulator  20  with the structure described above and to obtain uniform characteristics, the circulator  20  is not appropriate for mass production.  
         [0010]     The modulator  30  comprises a Schottky diode (not shown) and by switching the local oscillation signal entered through the circulator  20  by the switching operation of the Schottky diode, modulation is performed. To this Schottky diode, a predetermined bias voltage is input and by grounding, a closed circuit is formed. That is, when the Schottky diode is on, a local oscillation signal entered into the modulator  30  is transferred to the ground and when the Schottky diode is off, is totally reflected and is output to the modulated signal output port  24   a  through the circulator  20 , and thus amplitude shift keying (ASK) modulation is performed. A digital pulse signal that is an information signal is entered into an information signal entrance hole  32  connected to a Schottky diode mount  33 , and switches the Schottky diode mounted on the Schottky diode mount  33 . At this time, in order to match the Schottky diode mount  33  and a local oscillation signal, an air gap  34 , a front side dielectric line  35 , a high dielectric constant sheet  36 , and a back side dielectric line  37  are used. Also, a patch antenna  33   a  of the diode mount  33  should be designed to fit the frequency of a local oscillation signal. Because the sizes of the air gap  34 , the front side dielectric line  35 , the high dielectric constant sheet  36 , and the back side dielectric line  37  are very small, and consequently it is very difficult to manufacture these modules and to obtain uniform characteristics, these are not appropriate for mass production.  
         [0011]     By using the principle of a parallel dielectric line coupler, a dielectric line is made to be bent and data on linewidths of dielectric lines  12  and  14  appropriate to each bend angle are established and then the directional coupler  10  as described above is designed. However, in this dielectric coupler  10 , when it is desired to make a small-sized one, the bend angle cannot be reduced and if the bend is more curved, loss occurs unless the linewidths of the dielectric lines  12  and  14  should be reduced by different width with respect to angles corresponding to respective frequencies. However, it is very difficult to apply this constraint to the actual manufacturing. Also, when this directional coupler is to be mass produced, it is difficult to obtain an accurate dielectric line interval or bending angle and the isolation degree between ports is degraded. Furthermore, when in order to implement a lighter and smaller product it is desired to reduce the size further, the linewidth of the bend part should be reduced in order to increase the bending angle. However, it is difficult to accurately reduce the linewidth of the dielectric line made of Teflon and the like and therefore the actual implement is very difficult.  
       SUMMARY OF THE INVENTION  
       [0012]     The present invention provides a non-radiative dielectric (NRD) waveguide modulator having a waveguide type hybrid coupler, in which by forming a waveguide type 180° hybrid coupler and waveguides as a single body, the structure is simplified and manufacturing processes are reduced such that consistency of characteristics is maintained, manufacturing time and cost are reduced, and consequently, manufacturability is improved.  
         [0013]     According to an aspect of the present invention, there is provided a non-radiative dielectric (NRD) waveguide modulator comprising: a conducting housing which comprises a lower conducting plate and an upper conducting plate combined with the lower conducting plate; a hybrid coupler which is disposed inside the conducting housing and is formed in a structure in which a plurality of waveguides processed as conduit-shape cavities are connected to the outer surface of a ring portion processed as a ring-shape cavity, with having a predetermined phase difference, and are extended in the radius direction, and a local oscillation signal input through any one of the plurality of waveguides is distributed to at least two waveguides and propagated; a modulator in which a dielectric line, which includes a diode mount on which a Schottky diode is mounted, is solidly disposed inside a modulator cavity inside the conducting housing, and the dielectric line is connected to any one waveguide of the hybrid coupler, and which modulates a local oscillation signal input through the dielectric line by using the Schottky diode and outputs the modulated signal to the outside; and a termination which is connected to an end of any one waveguide terminating the local oscillation signal, among the plurality of waveguides of the hybrid coupler, and terminates a signal reflected by the modulator by consuming the signal internally. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The above objects and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which:  
         [0015]      FIG. 1   a  is a perspective view of the structure of a prior art modulator using a non-radiative dielectric (NRD) waveguide;  
         [0016]      FIG. 1   b  is a plan view of the structure of  FIG. 1   a;    
         [0017]      FIG. 2   a  is an exploded perspective view of the entire structure of an NRD waveguide modulator having a waveguide type coupler according to the present invention;  
         [0018]      FIG. 2   b  is a plan view of a lower conducting plate of  FIG. 2   a  which is seen from the upside;  
         [0019]      FIG. 3  is a partially extracted detailed perspective view of a waveguide type hybrid coupler shown in  FIG. 2   a;    
         [0020]      FIG. 4   a  is a partially extracted detailed perspective view of the structure of a termination shown in  FIG. 2   a;    
         [0021]      FIG. 4   b  is a side view of the termination of  FIG. 4   a;    
         [0022]      FIG. 5   a  is a partially extracted detailed perspective view of the structure of a modulator part shown in  FIG. 2   a;    
         [0023]      FIG. 5   b  is a side view of the modulator part of  FIG. 5   a ; and  
         [0024]      FIG. 6  is a partially extracted sectional perspective view showing the combination structure of a diode mount and dielectric lines in detail. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]     A modulation method applied to the embodiments of the present invention is an amplitude shift keying (ASK) modulation. In the present apparatus, in order to modulate a high speed large capacity signal into an ASK modulated signal, a Schottky diode which is a high speed switching device is used and by using this, a local oscillation (LO) signal is switched to perform ASK modulation. In particular, the present modulator is manufactured by applying a non-radiative dielectric (NRD) waveguide technology which is easy to manufacture and has a less transmission loss. At this time, in order to transfer an input local oscillation signal to a Schottky diode, a hybrid coupler is formed in the form of a waveguide in a conducting housing as a single body such that the structure of the modulator is simplified. In addition, a termination connected to the hybrid coupler is also formed as a waveguide in the conducting housing and a modulator is also formed in the conducting housing. Referring to  FIGS. 2   a  through  6 , this will now be explained in detail.  
         [0026]      FIG. 2   a  is an exploded perspective view of the entire structure of an NRD waveguide modulator having a waveguide type coupler according to the present invention, and  FIG. 2   b  is a plan view of a lower conducting plate of  FIG. 2   a  which is seen from the upside.  
         [0027]     The modulator has a conducting housing  100  comprising a lower conducting plate  110  and an upper conducting plate  120  combined with the lower conducting plate  110 , and has a hybrid coupler  200 , a termination  300 , and a modulator  400  embedded in this conducting housing  100 . In the present embodiment, the hybrid coupler  200 , termination  300 , and modulator  400  are formed on the lower conducting plate  110  and the upper conducting plate  120  functions as a cover. However, inversely, these elements may be formed on the upper conducting plate  120  and the lower conducting plate  110  may be used as a cover. The structure of the core elements of the present invention, the hybrid coupler  200 , the termination  300 , and the modulator  400 , will now be explained in detail.  
         [0028]     The hybrid coupler  200  is formed in the form of waveguides as an integral part in the lower conducting plate  110  by mechanical processing, and preferably, is formed as a 180° hybrid coupler  200  which changes the direction of a local oscillation signal input through a signal input port  112  by 180° and then transfers to the modulator  400 . This 180° hybrid coupler  200  has four branches connected to waveguides  210  through  240 . More specifically, a signal input port  112  to which a local oscillation signal is input is formed at the end of a first waveguide  210 , the modulator  400  is connected to the end of a second waveguide  220 , a mixer input port  114  which is connected to a mixer of a reception unit (not shown) is formed at the end of a third waveguide  230 , and an isolation port  116  which is connected to the termination is formed at the end of a fourth waveguide  240 . Accordingly, a local oscillation signal input to the signal input port  112  of the 180° hybrid coupler  200  is distributed to the mixer input port  114  and the modulator input port  118  and the isolation port  116  is terminated by the termination  300 . This termination  300  is an element terminating the isolation port  116  and the detailed structure will be explained in detail referring to  FIGS. 4   a  and  4   b.    
         [0029]     The 180° hybrid coupler  200  described above has a waveguide shape and the part of the modulator  400  connected to the hybrid coupler  200  is a dielectric line. Accordingly, there is a transition unit to change a line when a local oscillation signal distributed by the hybrid coupler  200  is transferred to the dielectric line of the modulator  400 . This transition unit is made in the form of a transformer with a length of λg/4 and low impedance reduced by shortening the distance between the dielectric line  410  and both side surfaces of conductor, and is disposed at the input end and output end of the modulator  400 .  
         [0030]     The modulator  400  connected to the end of the modulator input port  118  of the hybrid coupler  200  is formed by disposing dielectric lines  410  in a modulator cavity  420  formed on the lower conducting plate  110 , connected to the second waveguide  220 , and combining a high dielectric constant sheet  430  for matching of the modulator  400  and a Schottky diode mount  440  having a Schottky diode with the dielectric lines  410 . This modulator  400  will be explained in detail referring to  FIGS. 5   a  through  6 . To the back end of the modulator  400 , a waveguide  450  through which a signal modulated by the Schottky diode is output is connected, and a modulated signal output port  452  through which a modulated signal is output is formed at the end of the waveguide  450 .  
         [0031]     Reference number  340  not described above indicates a termination upper conducting plate and reference number  460  indicates a modulator upper conducting plate and these are integrally formed on the bottom surface of the upper conducting plate  120 .  
         [0032]      FIG. 3  is a partially extracted detailed perspective view of a waveguide type hybrid coupler shown in  FIG. 2   a.    
         [0033]     As shown, at the center of the 180° hybrid coupler  200 , four waveguides  210  through  240  are connected to each other and among them, the first and second waveguides  210  and  220  have a 180° phase difference. The characteristic impedance of each waveguide  210  through  240  is Z 0  and the characteristic impedance of the central part line formed by a ring portion  250  to which the waveguides  210  through  240  are converging is Z0/{square root}{square root over (2)}. In the waveguide type hybrid coupler  200 , the interval between the first and second waveguides  210  and  220  is 3λg/4, and the interval between the first and third waveguides  210  and  230 , that between the third and fourth waveguides  230  and  240 , and that between the fourth and second waveguides  240  and  220  are λg/4 each. Here, λg means the wavelength inside a waveguide. Accordingly, if the interval λg/4 of the first and third waveguides  210  and  230  is subtracted from the interval 3λg/4 of the first and second waveguides  210  and  220 , the interval of the second and third waveguides  220  and  230  becomes λg/2 and consequently the phase difference becomes 180°. A local oscillation signal entered into the first waveguide  210  of the waveguide type 180° hybrid coupler  200  is propagated into the second and third waveguides  220  and  230 , in particular the signal propagated to each direction of the ring portion  250  is transferred to each waveguides  220  and  230  having the same phase from the first waveguide  210  to be divided as each half the power of the signal. In the fourth waveguide  240 , the phase of a signal propagated to each direction of the ring portion  250  becomes an opposite phase and the signal is canceled, and therefore the end part of the fourth waveguide  240  becomes the isolation port  116 . At this isolation port  116 , a waveguide type termination is disposed. This termination plays a role of consuming the signal entered from the modulator described above, to terminate the signal. Also, in signals output to the second waveguide  220  and to the third waveguides  230 , the phase difference of the traveling distances of the signals is 180°, and accordingly the phase of a signal output to the second waveguide  220  and that to the third waveguides  230  are opposite.  
         [0034]     The interval between each waveguide of the hybrid coupler  200  shown in this embodiment is just a preferred embodiment and the interval can be adjusted in any appropriate manners. That is, even though the interval between each waveguide  210  through  240  is increased by half a wavelength (λg/2) or a wavelength (λg), the only requirement is to match the phase difference between waveguides. In addition, changing the position of each waveguide does not matter. For example, if the third waveguide  230  is an input port for a local oscillation signal, each half of the power of the signal is distributed and propagated to either of the first and fourth waveguides  210  and  240  and a port connected to the second port  220  will be an isolation port.  
         [0035]      FIG. 4   a  is a partially extracted detailed perspective view of the structure of a termination shown in  FIG. 2   a , and  FIG. 4   b  is a side view of the termination of  FIG. 4   a.    
         [0036]     At the isolation port of the fourth waveguide  240  formed on the lower conducting plate  110 , the termination  300  is disposed. This termination  300  has a structure in which a waveguide  310  is cut at the center and a resisting sheet  320  is inserted between the two cut parts. More specifically, a resisting sheet mounting portion  330  wider than the width of the waveguide  310  is formed on the lower conducting plate  110  and at a position corresponding to a height half that of the waveguide  310 . By solidly mounting a resisting sheet  320  on this resisting sheet mounting portion  330  and covering the upper conducting plate  120  having the termination upper conducting plate  340  fixed at the bottom surface, the termination  300  is constructed. This termination upper conducting plate  340  may be integrally formed at the bottom surface of the upper conducting plate  120  as in the present embodiment, or may be formed separately. In the termination upper conducting plate  340 , a groove  342  which has the same width as that of the waveguide  310  and a height half that of the waveguide  310 , and forms the upper half of the waveguide  310 , is formed. If the termination upper conducting plate  340  is solidly mounted on the resisting sheet and held in the resisting sheet mounting portion, the groove  342  and the bottom half of the waveguide  310  of the lower conducting plate  110  form a complete waveguide and the resisting sheet  320  is inserted in the middle in the height direction. In the resisting sheet  320  as shown in  FIG. 4   a , a V-shape groove in which the width is narrowing with decreasing distance to the vertex is formed on the front side. The length and shape of this resisting sheet  320  may be changed a little with respect to frequency in order to match impedance. The resisting sheet  320  terminates a signal entered into the termination  300  by consuming the power of the signal.  
         [0037]      FIG. 5   a  is a partially extracted detailed perspective view of the structure of a modulator part shown in  FIG. 2   a , and  FIG. 5   b  is a side view of the modulator part of  FIG. 5   a.    
         [0038]     As shown in  FIG. 5   a , the modulator  400  has a modulator cavity  420  which is connected to the modulator input port  118  of the hybrid coupler and is a widening space in the lower conducting plate  110 , and has a dielectric line  410  connected to the waveguide  220  and mounted on the modulator cavity  420 . This dielectric line  410  is formed with a front side dielectric line  412  and a back side dielectric line  414 , and a diode mount  440  on which a Schottky diode is mounted is disposed between these front and back side dielectric lines  412  and  414 . In particular, a high dielectric constant sheet  430  is disposed at the end part of the front side dielectric line  412  and is in contact with the diode mount  440 . In addition, both ends of the diode mount  440  are connected to an information signal entering hole  422  and a ground hole  424 , by which an operation signal is transferred to the Schottky diode.  
         [0039]     By inserting a predetermined small part of the bottom part of the dielectric line  410  into a line position groove  426  formed on the modulator cavity  420 , the front and back side dielectric lines  412  and  414  are fixed and then, by covering the upper conducting plate  120  on the top part of the front and back side dielectric lines  412  and  414 , the top open part of the modulator cavity  420  is closed by the modulator upper conducting plate  460  formed on the bottom surface of the upper conducting plate  120 . Mounting protrusions  428  and  428   a  for the modulator upper conducting plate  460  to be mounted are formed on both side walls forming the modulator cavity  420 . On the bottom surface of the modulator upper conducting plate  460 , a line support groove  462  corresponding to the line position groove  426  is formed and small part of the top part of the front and back side dielectric lines  412  and  414  is inserted into the line position groove  426  such that the top and bottom part of the dielectric lines are held and support by the line support groove  462  and the line position groove  426 . These line position groove  426  and line support groove  462  contribute to remove assembly errors and maintain consistency in characteristics, as well as to select a position and fix the dielectric lines  412  and  414 . Thus, by disposing the dielectric line  410  between the upper and lower conducting plates  110  and  120 , the modulator  400  is formed as an NRD waveguide type.  
         [0040]     Since the signal propagation path for a local oscillation signal entering into the modulator  400  with the structure described above changes from the waveguide  220  to the NRD line  412 , a transition  429  for transformation is disposed at the input side of the modulator  400 , which is the front part of the modulator  400 . A transition  429   a  is also disposed at the output side of the modulator  400 , which is the back part of the modulator  400 , to change a signal propagation path form the NRD line  414  to the waveguide  450  such that compatibility of the output port  452  of the modulator  400  with other waveguide components is enhanced. This transition  429  and  429   a  is formed with a transformer with a length of λg/4 by shortening the side walls of the NRD waveguide to reduce impedance, and plays a role of matching impedances of waveguides and NRD waveguides.  
         [0041]      FIG. 6  is a partially extracted sectional perspective view showing the combination structure of a diode mount and dielectric lines in detail. A local oscillation signal entering into the modulator  400  is ASK modulated by being switched by the switching operation of the Schottky diode  442 . This switching operation of the Schottky diode  442  is performed by an information signal entered into an information signal entering hole. For smooth switching, matching of the NRD line  410  and the diode mount  440  on which the Schottky diode  442  is mounted at the frequency of an entered local oscillation signal is needed. For this matching, a high dielectric constant sheet  430  is disposed between the front side dielectric line  412  and the diode mount  440 , and a patch antenna  444  to fit the frequency of a local oscillation signal is disposed on the diode mount  440 . At both ends of this patch antenna  444 , RF chokes  444   a  and  444   b  are attached so that a local oscillation signal does not flow into the information signal entering hole or the ground hole. In order to induce matching with respect to the frequency of a local oscillation signal, the positions of the diode mount  440  and the high dielectric constant sheet  430  may be exchanged.  
         [0042]     Referring to attached drawings, the operation of the present invention will now be explained in detail.  
         [0043]     A local oscillation signal oscillated in a local oscillator is entered into the signal input port  112  of the present apparatus. Then, the local oscillation signal propagated to each direction of the ring portion  250  in the 180° hybrid coupler  200  from the first waveguide  210  is propagated to the second and third waveguides  220  and  230  having the same phase, in which the power of the signal is divided into two, each half propagated to one of the waveguides  220  and  230 . The phase of the signal propagated to the fourth waveguide  240  becomes opposite to that of a signal propagated from the ring portion  250  by the termination  300  and the signal is terminated. At this time, the signal propagated to the second waveguide  220  is transferred to the modulator  400  after the signal propagation path changes from a waveguide to an NRD waveguide through the transition  429  disposed at the front end of the modulator  400 . The signal thus transferred to the front side dielectric line  412  is switched and modulated while the Schottky diode  442  performs switching operations according to an information signal entering into the information signal entering hole  422 . Thus modulated signal is transferred to the modulated signal output port  452  through the back side dielectric line  414  in the modulator  400  and the waveguide  450 . At this time, by passing through the transition  429   a  disposed at the back end of the back side dielectric line  414 , the signal propagation path changes into the waveguide  450  and the signal is propagated to the modulated signal output port  452 .  
         [0044]     Optimum embodiments have been explained above. However, it is apparent that variations and modifications by those skilled in the art can be effected within the spirit and scope of the present invention defined in the appended claims. Therefore, all variations and modifications equivalent to the appended claims are within the scope of the present invention.  
         [0045]     Among a variety of possible embodiments, the embodiments disclosed here are selected as preferred examples to help understanding of those skilled in the art. It is noted that the present invention is not limited to the preferred embodiment described above, and it is apparent that variations and modifications by those skilled in the art can be effected within the spirit and scope of the present invention defined in the appended claims.  
         [0046]     As described above, in the NRD waveguide modulator having a waveguide type hybrid coupler according to the present invention, a waveguide type 180° hybrid coupler and waveguides are integrally formed in a conducting housing by mechanical processing such that more consistent and superior characteristics compared to the prior art directional coupler using NRD waveguides can be obtained. Furthermore, a circulator in the prior art apparatus is removed and the modulator part is formed as NRD waveguides such that manufacturing is simplified, transmission loss is reduced, and transmission efficiency is enhanced. Consequently, the consistency of characteristics of an apparatus can be maintained and in addition, the structure is simplified and the manufacturing processes are reduced such that manufacturing time and cost can be reduced.  
         [0047]     Also, by disposing transition units between waveguides and RND waveguides, an amplifier and a diplexer whose I/O ports are waveguides can be mounted on a modulated signal output port such that compatibility between a waveguide apparatus and an NRD waveguide apparatus can be provided.