JP6124355B2 - Wireless transmission device and wireless transmission system - Google Patents

Description

  The present invention relates to a wireless transmission device and a wireless transmission system.

  The transmission power efficiency of the wireless transmission device is represented by the ratio of the power of the electromagnetic wave actually radiated from the antenna to the space out of the operation power supply power supplied from the operation power source such as a DC power source to the wireless transmission device. As a technique for improving transmission power efficiency, Non-Patent Document 1 describes a technique for improving the power efficiency of a power amplifier that consumes the most power in a wireless transmission device by a high-efficiency power amplifier configuration method.

  In order to improve the transmission power efficiency of the wireless transmission device, in addition to improving the power efficiency of the above-described power amplifier, the power of the radio frequency input to the antenna and the power of the electromagnetic wave radiated from the antenna to the space It is also important to improve the antenna radiation efficiency expressed by the ratio of. The antenna radiation efficiency depends on whether or not the input impedance matching of the antenna is achieved. If the input impedance matching is achieved, the antenna radiation efficiency increases. If the input impedance matching is not achieved, the antenna radiation efficiency decreases. To do. In general, in order to radiate electromagnetic waves into the space with high efficiency by resonance of the radiating conductor of the antenna, the physical size of the radiating conductor is set to a certain size determined by the resonance frequency of the radiating conductor, and input impedance matching is achieved. It has been.

F. H. Raab, “Maximum efficiency and output of Class-F power amplifiers,” IEEE Trans. On Microwave Theory and Techniques, Vol. 49, No. 6, pp.1162-1166, June 2001. S. Nishiki and T. Nojima, "Harmonic Reaction Amplifier-A Novel High-Efficiency and High-Power Microwave Amplifier," Microwave Symposium Digest, 1987 IEEE MTT-S International, vol.2, no., Pp.963-966, May 9 1987-June 11 1987.

  In recent years, as represented by mobile terminals, miniaturization of wireless communication devices has been promoted. In order to reduce the size of the wireless communication device, it is necessary to realize a wireless transmission device having a small and integrated antenna. In addition, it is necessary to realize a wireless transmission apparatus having a small and integrated antenna even when the gain of the antenna is improved by arraying or when the radiation directivity of the antenna is controlled.

  However, in order to reduce the size of the antenna, it is necessary to reduce the physical size of the radiation conductor. If the physical size of the radiation conductor is reduced, it is difficult to match the input impedance of the antenna in relation to the wavelength of the radio frequency signal. become. Without matching the input impedance of the antenna, the resonance of the radiation conductor cannot be obtained at radio frequencies. Therefore, if the input impedance matching of the antenna cannot be achieved, the antenna radiation efficiency is lowered. As a result, the transmission power efficiency of the wireless transmission device is reduced.

This will be described more specifically.
FIG. 5 is a characteristic diagram showing an example of the relationship between the length of the radiation conductor of the antenna and the input resistance. FIG. 5A is a characteristic diagram showing the relationship between the antenna length of the dipole antenna and the input resistance. ) Is a characteristic diagram showing the relationship between the loop length of the loop antenna and the input resistance. In FIG. 5A, the horizontal axis represents the value (L / λ) obtained by normalizing the antenna length L, which is the length of the radiation conductor of the dipole antenna, with the wavelength λ, and the vertical axis represents the input resistance of the dipole antenna. Represent. In FIG. 5B, the horizontal axis represents a value (D / λ) obtained by normalizing the loop length D, which is the length of the radiation conductor of the loop antenna, with the wavelength λ, and the vertical axis represents the input of the loop antenna. Represents resistance.

  Usually, in the case of a dipole antenna, the total length of the rod-shaped radiation conductor is set to, for example, a half wavelength of the input radio frequency signal, and the radiation conductor resonates at the frequency of the radio frequency signal. The input impedance of the dipole antenna is about 73 ohms, for example.

  As understood from FIG. 5A, when the antenna length (L / λ) of the dipole antenna is made shorter than a half wavelength of the radio frequency signal, the input resistance of the dipole antenna tends to be significantly reduced. For this reason, it becomes difficult to realize input impedance matching by an external matching circuit. If the output of the power amplifier of the wireless transmission device and the input resistance of the dipole antenna do not match, resonance of the radiation conductor cannot be obtained. For this reason, it becomes difficult to efficiently supply power to the dipole antenna, and the antenna radiation efficiency is greatly deteriorated. As can be understood from FIG. 5B, as with the dipole antenna, the loop antenna also has a significantly reduced input resistance when the loop length (D / λ) is shortened. It becomes difficult to realize.

  Thus, reducing the size of the antenna by reducing the size of the radiation conductor of the antenna to be less than a half wavelength of the radio frequency signal degrades the input impedance matching of the antenna. When the input impedance matching of the antenna deteriorates, most of the power of the radio frequency signal supplied to the antenna from the power amplifier of the wireless transmission device is reflected by the antenna, and the power of the electromagnetic wave actually radiated from the antenna to the space is reduced. . For this reason, antenna radiation efficiency falls and the transmission power efficiency of a wireless transmitter falls. Except for applications where the required signal strength can be obtained even when the antenna transmission efficiency is sufficiently short and the antenna radiation efficiency is reduced, such as the antenna and wireless tag of a cordless telephone, it is much larger than the half wavelength of the radio frequency signal. It is not preferable to use a small radiating conductor having a small size from the viewpoint of antenna radiation efficiency and transmission power efficiency.

  In addition, there is a case where the transmission power efficiency is deteriorated also by a second harmonic (harmonic) generated due to nonlinear characteristics of an amplification element such as a transistor constituting a power amplifier of the wireless transmission device. As a technique for preventing such deterioration of transmission power efficiency due to the second harmonic, a harmonic matching reflection amplifier (HMRA) disclosed in Non-Patent Document 2 can be used.

FIG. 6 is a diagram illustrating a configuration example of a wireless transmission device according to the related art provided with the harmonic matching reflection type amplifier disclosed in Non-Patent Document 2 as a power amplifier 920.
The power amplifier 920 includes a driver 921, a fundamental wave suppression filter 922, a phase shifter 923, and a harmonic wave suppression filter 924. The driver 921 is composed of an amplifying element such as a transistor. In the wireless transmission device shown in FIG. 6, the power amplifier 920 amplifies the radio frequency signal input through the input terminal 910. The radio frequency signal amplified by the power amplifier 920 is supplied to the antenna 930 through the connection point 930a. The antenna 930 converts the radio frequency signal input from the power amplifier 920 into an electromagnetic wave and radiates it to space.

  Here, in the power amplifier 920, the second harmonic generated in the amplifier due to the nonlinear characteristic of the amplifier of the driver 921 is separated from the fundamental by the fundamental wave suppression filter 922 and the harmonic suppression filter 924. The separated second harmonic wave is reflected by the branched short-circuited or short-circuited stub, returned to the amplifying element of the driver 921, and converted into a fundamental wave by the amplifying element. In this way, the double wave generated in the amplifying element is returned to the amplifying element and converted into a fundamental wave, thereby improving the transmission power efficiency.

  However, as understood from this example, when a high frequency signal is input to the output section of the amplification element included in the power amplifier of the wireless transmission device, the frequency component of the sum or difference is caused by the mixing effect based on the nonlinear characteristic of the amplification element. Can be generated. Therefore, not only when the second harmonic wave is input to the output section of the amplifying element, but also because the input impedance matching of the antenna that is the load circuit of the amplifying element is not taken, the fundamental wave of the radio frequency signal is reflected by the antenna. Even when input to the output section of the amplifying element, the amplifying element can convert the fundamental wave to a harmonic including a second harmonic. For this reason, the case where the improvement effect of transmission power efficiency reduces may occur.

FIG. 7 is a characteristic diagram illustrating an example of the relationship between the input power of the power amplifier provided in the wireless transmission device according to the conventional technology and the output power of the second harmonic. In this example, a power amplifier using a microwave field effect transistor is used as the power amplifier. In FIG. 7, the characteristic line indicated by the dotted line indicates the characteristic when the impedance matching of the load of the power amplifier is taken, and the load impedance _RL is set to 50 ohms. In FIG. 7, the characteristic line indicated by the solid line indicates the characteristic when the load impedance matching of the power amplifier is deteriorated, and the load impedance _RL is set to 0.0001 ohm.

  As understood from the example of FIG. 7, when the load impedance matching of the power amplifier is deteriorated as compared with the case where the load impedance matching of the power amplifier is achieved (that is, between the antenna serving as a load and the power amplifier). (2), the output power of the second harmonic is increased. As described above, the cause of the increase in the output power of the second harmonic wave is the fundamental wave that is reflected by the antenna and input to the amplification element of the power amplifier due to the mixing effect based on the nonlinearity of the amplification element of the power amplifier. This is because the power of 2 is converted into the power of the second harmonic. For this reason, transmission power efficiency falls.

  The present invention has been made in view of such circumstances, and the object thereof is wireless transmission capable of improving transmission power efficiency without depending on transmission frequency even when input impedance matching is deteriorated. It is to provide an apparatus and a wireless transmission system.

  A wireless transmission device according to an aspect of the present invention includes an amplifier that amplifies and outputs a radio frequency signal, an antenna unit that converts a radio frequency signal input from the amplifier through a transmission line into an electromagnetic wave, and radiates the electromagnetic wave to the space; Provided on the transmission line, supplying the fundamental wave of the radio frequency signal to the antenna unit, and separating the frequency component other than the fundamental wave of the radio frequency signal output from the amplifier from the radio frequency signal A frequency separation unit that outputs to the line, and a frequency component other than the fundamental wave separated by the frequency separation unit is input via the branch line, and rectifies the frequency component other than the fundamental wave and outputs DC power. When the DC power is output from the rectifying unit and the power obtained from a predetermined power source is supplied to the amplifier as the operating power source power of the amplifier. Having a configuration of a radio transmitting apparatus and a supply power control unit to said amplifier as an operating power supply power of the amplifier to the DC power while limiting the power supplied to the amplifier from the predetermined power.

  In the wireless transmission device, for example, the frequency separation unit is a harmonic suppression filter, an input unit of the harmonic suppression filter is connected to an output unit of the amplifier, and an output unit of the harmonic suppression filter is connected to the output unit of the harmonic suppression filter. The antenna unit is connected, the output unit of the amplifier is connected to the input unit of the fundamental wave suppression filter via the branch line, and the output unit of the fundamental wave suppression filter is input to the rectifier unit The power supply control unit is connected to the output unit of the rectification unit.

  The wireless transmission device may further include, for example, a power storage unit that stores DC power output from the rectification unit.

  A wireless transmission system according to an aspect of the present invention is a wireless transmission system including a plurality of wireless transmission devices connected in parallel, and in which antenna units of the plurality of wireless transmission devices are arranged in an array. Each of the transmission devices is a wireless transmission device according to one aspect of the present invention.

  According to one aspect of the present invention, the radio frequency signal reflected from the antenna unit due to impedance mismatch in the antenna unit is used to output the amplifier (when the amplifier element is a field effect transistor, for example, its drain). Is converted to a second harmonic generated by the mixing effect due to the nonlinear effect of the amplifier amplifier element, and the second harmonic is inserted between the antenna and the antenna to form a harmonic circuit that forms the amplifier load circuit. The frequency separation unit such as a filter) converts the double wave from the fundamental wave and outputs it to the rectification unit to convert it into DC power, which is reused as operating power (DC power) for the amplifier. . Thereby, even if the input impedance matching is deteriorated, it is possible to improve the transmission power efficiency without depending on the transmission frequency.

  According to the present invention, even if input impedance matching is deteriorated, it is possible to improve transmission power efficiency without depending on the transmission frequency.

It is a figure which shows the structural example of the radio | wireless transmitter by 1st Embodiment of this invention. It is a figure for demonstrating the operation example of the radio | wireless transmitter by 1st Embodiment of this invention, and is a figure which shows the flow of electric power. It is a figure for supplementarily explaining the structural example of the radio | wireless transmitter by 1st Embodiment of this invention shown in FIG. It is a figure which shows the structural example of the radio | wireless transmitter by 2nd Embodiment of this invention. It is a characteristic view which shows an example of the relationship between the length of the radiation conductor of an antenna part, and input resistance, (A) is a characteristic view which shows the relationship between the antenna length of a dipole antenna, and input resistance, (B) is It is a characteristic view which shows the relationship between the loop length of a loop antenna, and input resistance. It is a figure which shows the structural example of the wireless transmitter by a prior art. It is a characteristic view which shows an example of the relationship between the input power and output power of the power amplifier with which the wireless transmitter by the prior art was equipped.

Embodiments of the present invention will be described below with reference to the drawings.
<First Embodiment>
FIG. 1 is a diagram illustrating a configuration example of a wireless transmission device 100 according to the first embodiment of the present invention.
The wireless transmission device 100 according to the first embodiment separates the second harmonic generated by the amplifying element of the transmission amplifier (power amplifier) 120 by a harmonic suppression filter (frequency separation unit) 130, and converts the second harmonic power into direct current. It has a function of converting to electric power and reusing it.

  Specifically, the wireless transmission device 100 includes an input terminal 110, a transmission amplifier (power amplifier) 120, a harmonic suppression filter 130, an antenna unit 140, a fundamental wave suppression filter 150, a rectification unit 160, a power control unit 170, a battery, A predetermined power source 180 such as a commercial power source is provided.

  An input terminal 110 is connected to an input portion of the transmission amplifier 120, and a radio frequency signal Ss having power Ps is input to the transmission amplifier 120 through the input terminal 110. An input part of the harmonic suppression filter 130 is connected to the output part of the transmission amplifier 120 via a transmission line, and an antenna part 140 is connected to the output part of the harmonic suppression filter 130 via the transmission line. . That is, the harmonic suppression filter 130 is provided on the transmission line for transmitting the radio frequency signal St output from the transmission amplifier 120 to the antenna unit 140.

  In addition, the input section of the fundamental wave suppression filter 150 is connected to the output section of the transmission amplifier 120 via a branch line 130a branched from the harmonic suppression filter. The output unit of the fundamental wave suppression filter 150 is connected to the input unit of the rectification unit 160, and the output unit of the rectification unit 160 is connected to the detection unit 172 of the power supply control unit 170. In the present embodiment, in order to handle a signal in a high frequency region, the harmonic suppression filter 130, the branch line 130a, the fundamental wave, as well as the transmission line for transmitting the radio frequency signal St output from the transmission amplifier 120 to the antenna unit 140 are used. Although the suppression filter 150 is configured using a microstrip line, the present invention is not limited to this example, and an arbitrary filter can be used according to the frequency domain of the signal.

  Here, the transmission amplifier 120 is a power amplifier that amplifies the radio frequency signal Ss with the power Ps input through the input terminal 110 and outputs the radio frequency signal St with the power Pt. The operating power supply power Pdcin is supplied from the power supply controller 170 to the transmission amplifier 120. The transmission amplifier 120 operates using the operating power supply power Pdcin supplied from the power supply controller 170 as a power supply, amplifies the radio frequency signal Ss input through the input terminal 110, and outputs a radio frequency signal St of power Pt.

  The harmonic suppression filter 130 suppresses harmonics including the second harmonic contained in the radio frequency signal St output from the transmission amplifier 120 and passes the fundamental wave of the radio frequency signal St. The harmonic suppression filter 130 supplies a fundamental wave of the radio frequency signal St to the antenna unit 140 and separates frequency components other than the fundamental wave of the radio frequency signal St output from the transmission amplifier 120 from the radio frequency signal St. It functions as a frequency separation unit that outputs to the branch line 130a. The harmonic suppression filter 130 and the fundamental wave suppression filter 150 are connected via the branch line 130a. The frequency components other than the fundamental wave of the radio frequency signal St separated by the harmonic suppression filter 130 (frequency separation unit) are input to the fundamental wave suppression filter 150 through the branch line 130a.

  The antenna unit 140 is a component for converting the radio frequency signal St input from the transmission amplifier 120 through the transmission line provided with the harmonic suppression filter 130 into an electromagnetic wave and radiating it to the space. The length of the radiation conductor of the antenna unit 140 is not necessarily set on the assumption that input impedance matching is taken. The antenna unit 140 can be composed of any type of antenna as long as it can radiate electromagnetic waves required for desired wireless communication into the space, and the length of the radiation conductor is also arbitrarily set. obtain.

  The fundamental wave suppression filter 150 is a constituent element for suppressing the frequency component of the fundamental wave among the frequency components separated by the harmonic suppression filter 130 and output to the branch line 130a. If the frequency component of the fundamental wave remaining in the frequency component separated by the harmonic suppression filter 130 is sufficiently small, the fundamental wave suppression filter 150 can be omitted. In this case, the frequency component separated by the harmonic suppression filter 130 is directly input from the harmonic suppression filter 130 to the rectifying unit 160.

  The rectifying unit 160 is a component for rectifying frequency components other than the fundamental wave of the radio frequency signal St separated by the harmonic suppression filter 130 (frequency separating unit) and outputting DC power Pdcret. The DC power Pdcret is output to the power supply control unit 170.

  The power supply control unit 170 is a component for supplying the operating power supply power Pdcin for the transmission amplifier 120. Basically, the power supply control unit 170 supplies power Pdc obtained from a predetermined power supply 180 such as a battery or a commercial power supply to the power supply terminal (not shown) of the transmission amplifier 120 as the operation power supply power Pdcin of the transmission amplifier 120. In addition, when the DC power Pdcret is output from the rectifying unit 160, the power supply control unit 170 limits the power supplied from the predetermined power supply 180 to the transmission amplifier 120 as the operation power supply power Pdcin, and uses the DC power Pdcret. The operation power supply power Pdcin of the transmission amplifier 120 is supplied to a power supply terminal (not shown) of the transmission amplifier 120.

Next, the operation of the wireless transmission device 100 according to the first embodiment will be described with reference to FIG.
FIG. 2 is a diagram for explaining an operation example of the wireless transmission device 100 according to the first embodiment of the present invention, and schematically shows a flow of power in the wireless transmission device 100. The apparatus configuration shown in FIG. 2 is the same as the apparatus configuration shown in FIG.
Here, the power of the double wave generated by the amplifying element of the transmission amplifier 120 that operates using the operation power supply power Pdcin as a power supply is recovered, and this double wave power is reused as the operation power supply power Pdcin of the transmission amplifier 120. The operation of the wireless transmission device 100 will be described.

  In a state where the radio frequency signal Ss is not input to the transmission amplifier 120, the power supply control unit 170 obtains the operating power supply power Pdcin of the transmission amplifier 120 from the power Pdc of a predetermined power supply 180 such as a battery or a commercial power supply. That is, the power supply controller 170 supplies the power Pdc obtained from the power supply 180 to the transmission amplifier 120 as the operation power supply power Pdcin. From this state, when the radio frequency signal Ss having the power Ps is input to the transmission amplifier 120 through the input terminal 110, the transmission amplifier 120 amplifies the radio frequency signal Ss and outputs the radio frequency signal St having the power Pt.

  The radio frequency signal St output from the transmission amplifier 120 is supplied to the antenna unit 140 through the harmonic suppression filter 130. Here, when the input impedance matching of the antenna unit 140 is not achieved, as illustrated in FIG. 2, most of the power Pt of the radio frequency signal St supplied to the antenna unit 140 is obtained from the harmonic suppression filter 130 and the antenna. A part of the power Pt of the radio frequency signal St reflected at the connection point 140a between the antenna unit 140 and supplied to the antenna unit 140 is converted into an electromagnetic wave and radiated from the antenna unit 140 to the space.

  In the example of FIG. 2, for convenience of explanation, it is assumed that most of the power Pt of the radio frequency signal St supplied to the antenna unit 140 is reflected at the connection point 140a. The reflected wave at the connection point 140a increases as the input impedance matching level of the antenna unit 140 is lower (as the input impedance matching is not achieved).

  The fundamental wave of the radio frequency reflected at the connection point 140a of the antenna unit 140 is input to the output unit of the transmission amplifier 120 through the harmonic suppression filter 130 as a reflected wave as illustrated in FIG. The reflected wave (fundamental wave) input to the output section of the transmission amplifier 120 is converted to a double wave by a mixing effect based on the nonlinear characteristics of an amplification element such as a transistor constituting the transmission amplifier 120. Therefore, the harmonic wave Sw having the second harmonic as the main frequency component is output from the transmission amplifier 120.

  The power Pw of the harmonic wave Sw including the second harmonic wave output from the transmission amplifier 120 is not transmitted to the direction of the antenna unit 140 due to the filter characteristic of the harmonic wave suppression filter 130, and as illustrated in FIG. The signal is transmitted in the direction of the branch line 130 a connected to the suppression filter 150. The harmonic wave Sw including the second harmonic passes through the fundamental wave suppression filter 150 and a phase shifter (not shown) and is input to the rectifying unit 160. The rectification unit 160 rectifies the power Pw of the harmonic wave Sw including the second harmonic input from the fundamental wave suppression filter 150 to generate DC power Pdcret, and supplies the DC power Pdcret to the detection unit 172 of the power supply control unit 170. To do.

  When the DC power Pdcret is input from the rectification unit 160, the detection unit 172 of the power supply control unit 170 detects the DC power Pdcret. When the detecting unit 172 detects the DC power Pdcret, the current limiting unit 171 limits the operating power source power Pdcin supplied from the power source 180 to the transmission amplifier 120 and also the DC power Pdcret to the operating power source power Pdcret of the transmitting amplifier 120. Give instructions to use.

  Upon receiving the above instruction from the detection unit 172, the current limiting unit 171 limits the current amount of the power Pdc from the predetermined power supply 180 by an amount corresponding to the current capacity of the DC power Pdcret supplied from the rectifying unit 160. . In this case, the current limiting unit 171 receives the DC power Pdcret from the rectifying unit 160 and generates the operating power supply Pdcin for the transmission amplifier 120 using the DC power Pdcret.

  Specifically, when the DC power Pdcret supplied from the rectifying unit 160 is less than the power required for the operation of the transmission amplifier 120, the current limiting unit 171 uses all of the DC power Pdcret as the operating power supply power Pdcin. While being used, the power shortage is obtained from the power Pdc of the predetermined power supply 180. In this case, the amount of power Pdc extracted from the predetermined power supply 180 is reduced by the amount of DC power Pdcret output from the rectifying unit 160, so that consumption of the power Pdc of the power supply 180 is suppressed. Note that, from the energy conservation law, the DC power Pdcret does not exceed the power required for the operation of the transmission amplifier 120.

  As described above, the fundamental wave (reflected wave) of the radio frequency signal reflected by the antenna unit 140 is converted into the harmonic wave Sw including the second harmonic in the transmission amplifier 120. Then, the power Pw of the harmonic wave Sw including the second harmonic is supplied from the harmonic suppression filter 130 installed as a load circuit of the transmission amplifier 120 to the rectifier 160 through the branch line 130a, and from the rectifier 160 as DC power Pdcret. Returned to the power supply controller 170. In addition, the current limiting unit 171 of the power supply control unit 170 limits the use of the power Pdc of the predetermined power supply 180 according to the DC power Pdcret supplied from the rectifying unit 160, and the power Pw of the harmonic Sw including the second harmonic. Is reused as the operating power supply power Pdcin of the transmission amplifier 120. Therefore, the transmission power efficiency represented by the ratio (Pout / Pdc) between the power Pdc of the power supply 180 and the power Pout of the electromagnetic wave radiated from the antenna unit 140 can be improved, and the power consumption of the entire wireless transmission device 100 can be improved. Can be reduced.

  In addition, according to the first embodiment, when a radiation conductor of a minute size (for example, a size equal to or less than a half wavelength of a radio frequency signal) that is difficult to match the input impedance is used as the radiation conductor of the antenna unit 140, Similar to a general antenna unit, most of the incident wave of the antenna unit 140 is reflected, and the antenna radiation efficiency is reduced. However, according to the first embodiment, the reflected wave from the antenna unit 140 is converted into the harmonic wave Sw including the second harmonic wave in the transmission amplifier 120, and the power Pw of the harmonic wave Sw is converted to the operating power supply power Pdcin of the transmission amplifier 120. Therefore, even if the input impedance matching of the antenna unit 140 is deteriorated, it is possible to improve the transmission power efficiency of the entire wireless transmission device 100 without depending on the transmission frequency (frequency of the radio frequency signal). .

  Further, according to the first embodiment, since the power of the reflected wave at the antenna unit 140 is used as the operating power supply power Pdcin of the transmission amplifier 120, it has a very small size (for example, a size less than a half wavelength of the radio frequency signal). By using the antenna unit 140, even if the input impedance matching of the antenna unit 140 is not achieved, a minute antenna having excellent transmission power efficiency can be realized.

  Further, according to the first embodiment, when the antenna unit 140 having a very small size (for example, a size equal to or less than a half wavelength of the radio frequency signal) is used (that is, when the input impedance matching of the antenna unit 140 is not achieved). Since the resonance phenomenon of the antenna unit 140 is not used, the dependency of the antenna radiation efficiency and the transmission power efficiency on the transmission frequency can be suppressed.

  Further, according to the first embodiment, the antenna unit 140 can be configured from a small-sized radiation conductor, and the antenna unit 140 can be configured in a small size, so that the wireless transmission device 100 can be highly integrated.

  Further, according to the first embodiment, the antenna unit 140 having a minute size (for example, a size equal to or smaller than a half wavelength of the radio frequency signal) can be arrayed. Therefore, it is possible to realize a so-called pattern control antenna that can flexibly control not only the amplitude of the electromagnetic wave radiated into space but also the phase radiation directivity. In this case, the power of the electromagnetic waves radiated to the space from the individual antenna portions forming the array is reduced, but the radiation is radiated to the space by arranging a large number of antenna portions in parallel as in the third embodiment described later. As the electromagnetic wave power, it is possible to obtain the same electric power as when a resonant antenna or the like is used.

Next, for reference, the effects of the first embodiment will be described by comparing the transmission power efficiency according to the first embodiment with the transmission power efficiency according to the conventional technique.
In a circuit with a reference impedance of 50 ohms, when the input resistance of the antenna part 140 (electromagnetic radiation part) is 1 ohm, the reflection coefficient R of the antenna part 140 is 0.961, so the return loss is only 0.346 dB. .

Therefore, it is assumed that the reflection coefficient R of the antenna unit 140 is 0.961. In addition, the rectification efficiency η _CV of the rectification unit 160, the conversion efficiency η _h when the fundamental wave is converted into the double wave in the transmission amplifier 120, and the power efficiency η _PA of the transmission amplifier 120 are assumed as follows.
η _CV = 0.9
η _h = 0.9
η _PA = 0.7

If the power of the electromagnetic wave radiated into the space by the wireless transmission device according to the conventional technique is Pout ′, the transmission power efficiency η ₀ of the wireless transmission device according to the conventional configuration is calculated by the following equation (1).

η ₀ = Pout ′ / Pdcin
= Η _PA × (1-R)
= 0.7 x (1-0.961)
= 0.027 (1)

  On the other hand, if the power of the electromagnetic wave radiated into the space by the wireless transmission device 100 according to the first embodiment is Pout, the transmission power efficiency η of the wireless transmission device 100 is calculated from Equation (2).

η = Pout / Pdcin
= {Η _PA × (1-R)} / {1-η _PA × η _h × η _CV × R}
= 0.7 x (1-0.961) / (1-0.7 x 0.9 x 0.9 x 0.961)
= 0.060 (2)

In the above-described example, the ratio (η / η ₀ ) between the transmission power efficiency η of the wireless transmission device 100 according to the first embodiment and the transmission power efficiency η ₀ of the wireless transmission device according to the conventional technique is about 2.2. The power efficiency η is improved about 2.2 times. Therefore, according to the first embodiment, the transmission power efficiency η of the wireless transmission device 100 can be improved as compared with the conventional technique.

  FIG. 3 is a diagram for supplementarily explaining a configuration example of the wireless transmission device 100 according to the first embodiment of the present invention shown in FIG. 1, and corresponds to a conventional device configuration. In the radio transmission apparatus shown in FIG. 3, power Pdc is supplied from the predetermined power supply 180 to the transmission amplifier 120 as the operation power supply power of the transmission amplifier 120. Further, the radio frequency signal St of power Pt output from the transmission amplifier 120 is supplied to the antenna unit 140 through a low-pass filter (LPF) 830 and an isolator 840.

  According to the conventional apparatus configuration of FIG. 3, the fundamental wave power of the radio frequency signal reflected by the antenna unit 140 is consumed by the dummy load provided in the isolator 840. Thereby, most of the reflected wave (fundamental wave) reflected by the antenna unit 140 is absorbed by the isolator 840, but a part of the reflected wave passes through the isolator 840 and is input to the output unit of the transmission amplifier 120. The For this reason, harmonics including the second harmonic are generated in the amplification element of the transmission amplifier 120 due to the mixing effect based on the nonlinearity of the amplification element of the transmission amplifier 120. Harmonics including the second harmonic generated by the amplifying element are blocked by the low-pass filter 830. As a result, only the fundamental wave of the radio frequency signal not including the second harmonic is transmitted to the antenna unit 140, and the influence of the second harmonic generated by the amplification element of the transmission amplifier 120 on the communication can be suppressed.

  However, according to the conventional apparatus configuration shown in FIG. 3, most of the reflected wave at the antenna unit 140 is consumed by the dummy load of the isolator 840 and is not used as the operating power supply power of the transmission amplifier 120. Therefore, in this case, the power due to the reflected wave at the antenna unit 140 does not contribute to the improvement of the transmission power efficiency. On the other hand, according to the wireless transmission device 100 shown in FIG. 1 according to the first embodiment, as described above, the reflected wave from the antenna unit 140 is converted into a double wave by the amplification element of the transmission amplifier 120. The double-wave power is rectified to generate DC power Pdcret, and the DC power Pdcret is used as operating power supply power for the transmission amplifier 120. Thereby, the transmission power efficiency of the wireless transmission device 100 can be improved.

Second Embodiment
Next, a second embodiment of the present invention will be described.
FIG. 4 is a diagram illustrating a configuration example of a wireless transmission device 200 according to the second embodiment of the present invention.
The wireless transmission device 200 according to the second embodiment includes a power control unit 270 instead of the power control unit 170 in the configuration of the wireless transmission device 100 shown in FIG. 1 according to the first embodiment described above.

The power supply control unit 270 stores the DC power Pdcret output from the rectifying unit 160 between the current limiting unit 171 and the detection unit 172 in the configuration of the power supply control unit 170 illustrated in FIG. 1 according to the first embodiment described above. The power storage unit 173 is further provided. The power storage unit 173 is, for example, a secondary battery. The power supply control unit 270 has a function of storing DC power Pdcret as energy in the secondary battery, that is, a function of charging the secondary battery.
Others are the same as in the first embodiment.

  According to the second embodiment, when the power supply control unit 270 includes the power storage unit 173, when the transmission amplifier 120 requires large power exceeding the capacity of the power supply 180, the energy stored in the power storage unit 173 is collected. The power required by the transmission amplifier 120 can be stably secured.

<Third Embodiment>
In the third embodiment, in the first embodiment or the second embodiment described above, the antenna unit 140 is configured by an ultra-small dipole antenna ignoring the resonance wavelength, and the length of the radiation conductor is, for example, a radio frequency. Is set to 1/10 or less of the wavelength in the radio wave propagation space. Others are the same as those in the first embodiment or the second embodiment.

  According to the third embodiment, the antenna unit 140 can be configured in a small size, and even if the input impedance matching of the antenna unit 140 is not achieved, a wireless transmission device excellent in transmission power efficiency can be realized. .

<Fourth embodiment>
The radio transmission system according to the fourth embodiment includes a plurality of radio transmission apparatuses according to the first embodiment or the second embodiment described above connected in parallel. In the wireless transmission system according to the fourth embodiment, the antenna units 140 of a plurality of wireless transmission devices are arranged in an array.

  According to the fourth embodiment, a radio transmission system capable of controlling the phase directivity of the antenna unit 140 can be realized by providing a large number of antenna units 140 in an array. As described above, when the physical size of the radiation conductor of the antenna unit 140 is reduced, the transmission power efficiency η is degraded. However, by using the plurality of antenna units 140 arrayed according to the third embodiment, the transmission power is reduced. Make up for the decline. Therefore, according to the fourth embodiment, even if the physical size of the radiation conductor of the antenna unit 140 is reduced, the antenna unit 140 is arrayed, so that the power Pout of the electromagnetic wave radiated from the antenna unit 140 to the space is reduced. It is possible to suppress the decrease.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and arbitrary modifications and corrections can be made without departing from the gist of the present invention.

  DESCRIPTION OF SYMBOLS 100,200 ... Wireless transmitter, 110 ... Input terminal, 120 ... Transmission amplifier, 130 ... Harmonic suppression filter, 130a ... Branch line, 140 ... Antenna part, 140a ... Connection point, 150 ... Fundamental wave suppression filter, 160 ... Rectification Unit, 170, 270 ... power source control unit, 171 ... current limiting unit, 172 ... detection unit, 173 ... power storage unit, 180 ... power source.

Claims (4)

An amplifier for amplifying and outputting a radio frequency signal;
An antenna unit that converts a radio frequency signal input from the amplifier through a transmission line into an electromagnetic wave and radiates it into space;
Provided on the transmission line, supplying a fundamental wave of the radio frequency signal to the antenna unit, and separating frequency components other than the fundamental wave of the radio frequency signal output from the amplifier from the radio frequency signal. A frequency separator that outputs to the branch line;
A frequency component other than the fundamental wave separated by the frequency separation unit is input via the branch line, a rectification unit that rectifies the frequency component other than the fundamental wave and outputs DC power; and
The power obtained from a predetermined power source is supplied to the amplifier as the operating power source power of the amplifier, and when the DC power is output from the rectifier, the power supplied from the predetermined power source to the amplifier is limited. A power supply controller that supplies the DC power to the amplifier as operating power supply power of the amplifier;
A wireless transmission device comprising: The frequency separation unit is a harmonic suppression filter,
The output part of the amplifier is connected to the input part of the harmonic suppression filter,
The antenna unit is connected to the output unit of the harmonic suppression filter,
The input part of the fundamental wave suppression filter is connected to the output part of the amplifier via the branch line,
The input unit of the rectifier unit is connected to the output unit of the fundamental wave suppression filter,
The wireless transmission device according to claim 1, wherein the power supply control unit is connected to an output unit of the rectification unit.   The wireless transmission device according to claim 1, further comprising a power storage unit that stores DC power output from the rectification unit. A wireless transmission system comprising a plurality of wireless transmission devices connected in parallel, wherein antenna portions of the plurality of wireless transmission devices are arranged in an array,
4. The wireless transmission system according to claim 1, wherein each of the plurality of wireless transmission devices is the wireless transmission device according to claim 1.

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