JP2006319511A - Transmission system and its receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission system in which the element intervals of a plurality of receiving antenna elements may not be set in the half-wave length or less of carrier waves, and a receiver for the transmission system. <P>SOLUTION: A transmitter 100 overlaps and transmits a pilot signal to an information signal (an input signal). The receiver has the receiving antenna elements #1 to #4 receiving a signal 110 in which the pilot signal is overlapped with the information signal; receiving-frequency converters #1 to #4 to which signals received by the receiving antenna elements #1 to #4 are input respectively, and which down-converts the information signal 213 by using the pilot signal 212 as a local signal and outputs an output signal 215; and a synthetic circuit 260 synthesizing output signals from the receiving-frequency converters #1 to #4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transmission system including a transmission device and a reception device, and the reception device.

  In the field of communication / broadcasting, it is necessary to select radio waves carrying desired information from radio waves that are mixed and flying. There is a so-called array antenna in which a plurality of antenna elements are arranged so that the amplitude and phase of excitation in each antenna element can be independently controlled as a means for selecting a desired radio wave according to the directivity characteristics of the antenna (non-patent) Reference 1).

A linear (linear) array antenna composed of K elements will be described as an example with reference to FIG. In Figure 1, the antenna element # 1, # is the voltage induced in the 2 · · · #K, after amplitude weights only _{A 1, A} 2 ··· _{A K} respectively amplitude adjuster is adjusted, the variable phase respectively vessel phase shift amount [delta] _1, is shifted by δ ₂ ··· δ _K are combined by the combining circuit sigma. As shown in FIG. 1, when radio waves arrive from the direction of angle θ, the voltage induced in the kth antenna element (k = 1, 2,... K) is a received signal at a reference point on the baseline. Is E _0, and the reception characteristics of each antenna element are equal, the following equation is given. Here, f is the carrier frequency, λ is the wavelength of the carrier, c is the propagation velocity, and d _k is the position of the kth element measured from the reference point. The path length difference l (= d _k sin θ) shown in FIG. 1 is l = cτ _k from the following equation (2). τ _k is a time difference (delay time) from when the radio wave arrives at the reference point until the radio wave having the same phase arrives at the position of the k-th element.

各素子出力の移相量を可変移相器で位相が揃うように調整して合成回路Σで加算すると、合成出力Ｅ_ｓｕｍは次式となる。

When the phase shift amount of each element output is adjusted by the variable phase shifter so that the phases are aligned and added by the synthesis circuit Σ, the synthesized output E _sum is expressed by the following equation.

ここで、Ａ_ｋ、δ_ｋはそれぞれｋ番目の素子に掛ける重みと移相量である。移相量δ_ｋは、所望の方向をθ_０とすると、

Here, A _k and δ _k are a weight and a phase shift amount to be applied to the k-th element, respectively. The phase shift amount δ _k is given as θ _{0 in the} desired direction.

に選ぶ。このようにすると、角度θ_０方向の所望信号は同相で加算される一方、それ以外の方向では、各素子の出力の位相が一致せず互いにある程度の相殺が行われる。したがって、アンテナのメインローブを向けて所望信号を取り出すことができる。
しかし、ｄ_ｋが大きい場合には、

Choose to. In this way, the desired signals in the direction of the angle θ ₀ are added in phase, while in the other directions, the phases of the outputs of the elements do not match and a certain amount of cancellation is performed. Therefore, a desired signal can be taken out with the main lobe of the antenna directed.
However, if d _k is large,

を満足するような角度θ_ｇｍ（ｍ＝±１，±２・・・）でも、メインローブと同様に同相になって加算されて大きな応答を生じる。これはグレーティングローブと呼ばれており、所望の方向以外からも電波を受信してしまうことになるので、設計段階から防止策が取られるのが普通である。

Even at an angle θ _gm (m = ± 1, ± 2...) _That satisfies the above, a large response is generated by adding the same phase in the same manner as the main lobe. This is called a grating lobe, and radio waves are received from directions other than the desired direction. Therefore, it is usual to take preventive measures from the design stage.

As a measure for preventing grating lobes, “the value of the angle θ ₀ is limited to a certain range (the direction in which a desired radio wave arrives) is limited” or “the antenna element interval is equal to or less than a half wavelength of the carrier wave (0.5λ or less). ) ”Can be considered. In the array antenna, the latter “restricting the antenna element interval to 0.5λ or less of the carrier wave” is often performed.

  As described above, in the field of communication / broadcasting, it is necessary to select radio waves carrying desired information from radio waves that are mixed and flying. It is possible to select a desired radio wave according to characteristics. Direction-of-arrival estimation technology using an array antenna arranges a plurality of antenna elements in order to select a desired radio wave according to the directivity characteristics of the antenna, and determines the desired wave direction vector (arrival direction) from the phase difference of each antenna element. Is estimated.

The direction of arrival estimation technique will be described with reference to FIG. 1 where K = 2, that is, a linear (linear) array antenna composed of two elements. When the radio wave arrives from the direction of the angle θ, the voltage E _k induced in the k-th receiving antenna element (k = 1, 2) is the received signal at the reference point on the baseline as E _0. Are equal to each other, the above equation (1) is given.

The element interval d (= d ₂ −d ₁ ) between the two receiving antenna elements # 1 and # 2 is set to be equal to or less than the half wavelength interval of the carrier wave. Thus, when the antenna element interval is set to be equal to or less than the half-wavelength interval of the carrier wave, assuming that the arrival direction of the desired wave is θ ₀ , the phase shift amount δ (in this example, the level between the two receiving antenna elements). Represents a phase difference)

で一意に求めることができる。

Can be obtained uniquely.

FIG. 2 shows a transmission system for direction of arrival estimation using a linear (linear) array antenna composed of two elements. On the transmission side, the information signal to be transmitted (frequency f _i ) is frequency-converted (usually up-converted to a frequency suitable for transmitting radio waves) and is sent out as radio waves from the transmission antenna. The frequency of the local signal for up-conversion and f _u (in the case of frequency conversion in multiple stages, means for the frequency of the total) and the carrier frequency of the transmission signal is a _(f i ₊ f _u). The reception frequency conversion units # 1 and # 2 perform frequency conversion (usually down-conversion) on the signals received by the reception antenna elements # 1 and # 2 to frequencies that can be easily processed. Assuming that the frequency of the local signal for down-conversion is f _d (in the case of multi-stage frequency conversion, this means the total frequency), the frequency of the output signal is (f _i + f _u −f _d ). Become. Under the condition that the phase of the local signal used for down-conversion is the same between antenna elements # 1 and # 2, the phase difference of the signal (f _i + f _u ) received by the receiving antenna becomes the down-converted output signal (f _i + F _u −f _d ), the phase difference is detected using the down-converted output signal, and the arrival direction of the radio wave can be estimated based on this information.

  However, if the antenna element spacing is set wider than the half-wavelength spacing, the phase shift amount δ may exceed 2π (the path length difference becomes one wavelength or more),

で、ｍ＝０以外の場合でも式（７）が成り立つことになり、解が１つには定まらならなくなる。一意に解を定めることを優先しｍ＝０の場合を強制的に選択すると、正しい移相量では無いため（例えば移相量δが３９０度のとき、３０度と強制的に設定してしまう）、所望信号の到来方向を推定することができなくなってしまうことがある。

Thus, even when m = 0, Equation (7) is satisfied, and the solution cannot be determined as one. If priority is given to determining a solution uniquely and the case of m = 0 is forcibly selected, it is not the correct phase shift amount (for example, when the phase shift amount δ is 390 degrees, it is forcibly set to 30 degrees) ), It may become impossible to estimate the direction of arrival of the desired signal.

  In the above, for the sake of simplicity, the case where only a desired wave can be received as a radio wave has been described. On the other hand, when radio waves other than the desired wave such as multipath are received at the same time, two antenna elements are obtained by performing correction processing using the pilot signal of the OFDM signal as in Non-Patent Document 2. It is possible to obtain the phase difference between the two. However, even in this case, if the interval between the two antenna elements is not set to 0.5λ or less, an erroneous phase difference (for example, when the phase shift amount δ is 390 degrees, it is determined to be 30 degrees) is detected. Will not work properly.

Nobuyoshi Kikuma, “Adaptive Antenna Technology”, Ohm, October 10, 2003, pages 11-15 Kazuhiko Mitsuyama and four others, “Direction of Arrival Estimation Using OFDM Received Waves -Effect of Correlated Interference Waves in Estimation”, 2004 Annual Conference of the Institute of Image Information and Television Engineers, 16-1

As described above, in the array antenna, by adjusting the weights A _k and phase shift [delta] _k to be applied to the k-th element, it is necessary to synthesize in phase the output of each element in the desired direction theta _0. Here, the weight A _k is generally realized by an amplitude adjuster (variable amplifier or variable attenuator), and the phase shift amount δk is generally realized by a variable phase shifter. At this time, as described above, it is necessary to set the antenna element interval to a half wavelength or less of the carrier wave.

  In order to keep it below the half wavelength of the carrier wave, an antenna element with a low directivity such as a patch antenna, that is, a physically small antenna is used, and the output signal is down-converted and taken out with a cable. For example, digital signal processing for weighting and phase shift amount correction is performed. However, since it is necessary to maintain the phase relationship when received by the antenna element in all the systems to be down-converted, it is necessary to make the electrical length of each system strictly equal (including making it equal by correction) There is a problem that circuit adjustment becomes difficult.

  Even in a receiving antenna that performs direction-of-arrival estimation, it is necessary to set the antenna element interval to be equal to or less than a half wavelength of the carrier wave. The antenna element shown in FIG. 2 does not need to depend on its gain, but if an antenna with sharp directivity, that is, an antenna gain (such as a horn antenna) is used, the antenna element physically has a half-wavelength interval. There was a problem that it could not be installed. On the other hand, when using an antenna with a low directivity such as a patch antenna as an antenna element, although it can be physically installed, it is difficult to correct the amount of phase shift due to mutual coupling between the antenna elements. However, there is a problem that the level that can be received becomes low, and it becomes impossible to secure a large CN ratio.

  An object of the present invention is to provide a transmission system and a receiving apparatus thereof that do not require the element spacing of a plurality of receiving antenna elements to be set to a half wavelength or less of the carrier frequency.

The outline of the invention disclosed in the present application will be briefly described as follows.
(1) A transmission system including a transmission device and a reception device, wherein the transmission device includes means for transmitting a pilot signal superimposed on an information signal, and the reception device includes a pilot signal superimposed on the information signal. A plurality of receiving antenna elements for receiving the received signals and signals received by the plurality of receiving antenna elements, respectively, and using the pilot signal as a local signal, downconverting the information signal and outputting an output signal A plurality of down-converting means; and a synthesizing means for synthesizing the output signals of the plurality of down-converting means.

  (2) A transmission system including a transmission device and a reception device, wherein the transmission device includes means for transmitting a pilot signal superimposed on an information signal, and the reception device includes a pilot signal superimposed on the information signal. A plurality of receiving antenna elements for receiving the received signals and signals received by the plurality of receiving antenna elements, respectively, and using the pilot signal as a local signal, downconverting the information signal and outputting an output signal A plurality of down-converting means; and a phase difference detecting means for detecting a phase difference between the receiving antenna elements using output signals of the plurality of down-converting means.

  (3) A reception device that receives a signal in which a pilot signal is superimposed on an information signal, and a plurality of reception antenna elements that receive a signal in which a pilot signal is superimposed on the information signal, and the plurality of reception antenna elements Each received signal is input, and a plurality of down-converting means for down-converting the information signal using the pilot signal as a local signal and outputting an output signal, and an output signal of the plurality of down-converting means are combined Combining means.

  (4) A receiving device that receives a signal in which a pilot signal is superimposed on an information signal, and a plurality of receiving antenna elements that receive a signal in which a pilot signal is superimposed on the information signal; and the plurality of receiving antenna elements Each received signal is input, using the pilot signal as a local signal, down-converting the information signal to output an output signal, and using the output signals of the plurality of down-convert means And a phase difference detecting means for detecting a phase difference between the receiving antenna elements.

  (5) In the receiver of (3) or (4), the signal in which the pilot signal is superimposed on the information signal is a signal that is up-converted using a local signal of the first frequency on the transmission side. is there.

  (6) In the receivers of (3) to (5), the down-conversion unit temporarily down-converts a signal in which a pilot signal is superimposed on the information signal using a local signal of a second frequency, The information signal once down-converted is down-converted using the pilot signal once down-converted as a local signal.

  (7) In the receivers of (3) to (6), the interval between the receiving antenna elements is larger than a half wavelength at a carrier frequency, and more than a half wavelength at a frequency that is a difference between the pilot signal and the information signal. It is the value that is installed at a shorter value.

  (8) In the receiving apparatus of (3), the frequency of the information signal or the pilot signal is set so that the maximum value of the phase difference in the receiving antenna element is equal to or less than a predetermined value in the frequency of the output signal of the down-converting means. The frequency, the interval between receiving antenna elements, or the number of elements to be combined are set.

  (9) In the receivers (3) to (8), the receiving antenna element has an aperture diameter larger than a half wavelength of the carrier wave.

  (10) In the receivers of (3) to (9), the receiving antenna elements are two-dimensionally or three-dimensionally arranged.

  The present invention down-converts the received information signal using the received pilot signal as a local signal, thereby making the phase shift amount proportional to the frequency that is the difference between the information signal and the pilot signal. As a result, it is not necessary to set the antenna element spacing to be equal to or less than a half wavelength of the carrier frequency, so that it is possible to avoid physical size restrictions in circuit creation. Therefore, an antenna having an antenna gain (for example, a horn antenna) can be used as the antenna element.

  In addition, the circuit elements used before the down-conversion do not cause a problem even if the phase differences of the antenna, amplifier, filter, etc. are within one wavelength, and therefore, at high frequencies (microwaves and millimeter waves). The degree of freedom of component selection can be increased.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings for explaining the embodiments, the same reference numerals are given to those having the same function.

(Embodiment 1)
FIG. 3 is a configuration diagram of a transmission system according to the first embodiment. The transmission system of the present embodiment includes one transmission apparatus 100 having a transmission antenna 101, four reception frequency conversion units # 1 to # 4 and reception frequency conversion units # each having reception antenna elements # 1 to # 4. 1 to # 4 output signals f _{1O to} f _4O and a combining circuit 260 that _combines the output signals f _{1O to} f _4O . This figure does not show a specific circuit configuration but is a configuration diagram conceptually showing the operation of the apparatus, and a filter for selecting a frequency and an amplifier for adjusting a level are omitted. In the present embodiment, the description will be made assuming that there are four reception antenna elements and reception frequency conversion units, but the number of reception antenna elements and reception frequency conversion units is not limited to four, and there may be a plurality.

In the transmission apparatus 100, a pilot signal (frequency f _p ) is added to an input signal, that is, an information signal to be transmitted (frequency f _i ) by an adder circuit 102 and frequency-multiplexed, and a local signal (frequency f _u ) is mixed by a frequency mixer 103. Then, up-convert and radiate from the transmitting antenna 101. Thus, as shown in 110 in the figure, up-converted pilot signal (frequency f _{p +} f _u) and upconverted information signal (frequency f _{i +} f _u) is transmitted together with a radio wave. Carrier frequency f, it is considered that the center frequency of the information _signal, which is f i + _{f u.}

In the receiving device, receiving antenna elements # 1, # 2, # 3, and # 4 are arranged. These receiving antenna element is assumed to be arranged at a sufficiently narrower than the half wavelength of the output signal to be described later (f i _{-f p).}

The outputs of the receiving antenna elements # 1 to # 4 are connected to the respective receiving frequency converters # 1 to # 4. The configurations of the reception frequency conversion units # 1 to # 4 are all the same except that the frequencies f _d1 , f _d2 ,... Of the local signal for down-conversion are not the same (may be the same). Only the reception frequency converter # 1 (210) will be described in detail. In the reception frequency conversion unit 210, the signal received by the reception antenna element # 1 is mixed with the local signal (frequency f _d1 ) by the frequency mixer 211 and temporarily down-converted to a frequency that allows easy signal processing. Further, the frequency-converted pilot signal (frequency f _p + _fu −f _d1 ) 212 and the frequency-converted information signal (frequency f _i + _fu −f _d1 ) 213 are divided and then the frequency-converted pilot. The signal (frequency f _p + _fu −f _d1 ) 212 is mixed as a local signal by the frequency mixer 214, and the frequency-converted information signal (frequency f _i + _fu −f _d1 ) 213 is down-converted. As a result, an output signal 215 having a frequency converted to (f _i −f _p ) is obtained from the output of the reception frequency conversion unit 210. Reception frequency conversion unit # 2, # 3, also in # 4, transformed output signals to a frequency in the same manner as the reception frequency conversion unit # 1 (f i _{-f p)} is obtained.

The reception frequency converters # 1, # 2, # 3, and # 4 are connected to the synthesis circuit 260 through lines designed to have substantially equal path lengths at the frequency (f _i −f _p ). A composite output is obtained from 260.

Hereinafter, the relationship including the phase will be described with equations. If the pilot signal and information signal received at the reference point are E _0p and E _0i , the pilot signal E _kp and information signal E _ki received by the receiving antenna element #k are given by the following equations.

アンテナ素子間の移相量は、電波で伝搬する周波数に比例する。ｆ_ｕは、ｆ_ｉ、ｆ_ｐに比べて十分に大きくするのが通常であるので、ほぼ２πｆ_ｕに比例することになる。

The amount of phase shift between the antenna elements is proportional to the frequency propagated by the radio wave. f _{u is,} f i, so to sufficiently larger than the _{f p} is a usually be approximately proportional to 2 [pi] f _u.

When the local signal E _kd (t) for down-conversion in the reception frequency conversion unit #k is given by the following equation:

ダウンコンバートされたパイロット信号Ｅ_ｋｐｄ、及び情報信号Ｅ_ｋｉｄは、

The down-converted pilot signal E _kpd and information signal E _kid are

で記すことができる。ここで、Ｄ_ｋ、ｆ_ｄｋ、α_ｋｄは受信周波数変換部＃ｋでのローカル信号の振幅、周波数、位相であり、Ｅ_０ｋｐｄ、Ｅ_０ｋｉｄは基準点で受信されるパイロット信号、情報信号をダウンコンバートしたパイロット信号、情報信号である。

It can be described with. Here, D _k , f _dk , and α _kd are the amplitude, frequency, and phase of the local signal at the reception frequency converter #k, and E 0 _kpd and E _0kid are the pilot signals and information signals received at the reference point. This is a converted pilot signal and information signal.

When the information signal is down-converted using the pilot signal obtained above as a local signal, the signal E _kO obtained is expressed by the following equation. Here, E 0 _kO is a signal obtained by down-converting the information signal received at the reference point using the pilot signal received at the reference point as a local signal.

ここで得られる各受信系統間の移相量は、（ｆ_ｉ−ｆ_ｐ）に比例し、電波で搬送波を受信したときに比べて、（ｆ_ｉ−ｆ_ｐ）／（ｆ_ｉ＋ｆ_ｕ）倍になっている。

Phase shift between the receiving systems obtained here _is proportional to _(f i -f _p), as compared to when it receives the carrier wave with _{radio, (f i -f p) /} (f i + f u) It has doubled.

This will be described with specific numerical values. 1000MHz center frequency _{f i} of the information signal, the frequency _{f p} of the pilot signal and 900 MHz, the frequency _{f u} of the local signal for up-conversion to 59 GHz. As a result, the carrier frequency is 60 GHz. The center frequency of the output signal of the reception frequency converter is 100MHz in _(f i -f _p), which is 1/600 of the carrier frequency 60 GHz.

  When antenna elements are installed at intervals of 2.5 mm, which is a half wavelength of a carrier wave, the phase difference between adjacent antenna elements takes a value from 0 degrees to 360 degrees. This can be reduced to 1/600 of the output signal from the reception frequency converter of this embodiment.

For example, even if the interval between the receiving antenna elements is 2.5 cm, which is the five wavelengths of the carrier wave, the phase between adjacent antenna elements changes only 6 degrees at the maximum. If signals of equal amplitude are obtained from 4 elements, there will be a phase difference of 18 degrees at the maximum, but a combined gain of 4 combined is obtained as 5.9 dB. The degradation from is less than 0.1 dB. Further, when the allowable value of the amplitude degradation in the four synthesis is 1 dB down from the case of the equiamplitude in-phase synthesis, the phase difference between the adjacent antenna elements may be set to 20 degrees or less. That is, the frequency f _{i of the} information signal, the frequency f _{p of the} pilot signal, the spacing between the antenna elements, so that the maximum value of the phase difference in the receiving antenna element is equal to or less than a predetermined value in the frequency of the output signal of the reception frequency converter. If the number of elements to be combined is determined, the elements can be combined with almost no deterioration in amplitude without using a phase adjustment circuit.

  In this embodiment, since the phase difference in the circuit before down-converting the pilot signal as a local signal is canceled, the phase characteristics of components such as amplifiers, filters, and line lengths are shifted by one wavelength in each receiving system. If it is within, there will be no problem. Conventionally, in order to preserve the phase difference when received as radio waves by an antenna element, it is necessary to strictly align the electrical lengths of the respective systems. In this embodiment as well, in the circuit after down-converting the pilot signal as a local signal, the line length needs to be equal, but the frequency after down-conversion is considerably higher than the carrier frequency. Since it is small, it is not so difficult to align the line length (phase) at this frequency.

Here, an example is described in which the pilot signal is up-converted on the transmission side and down-converted once at the frequency f _dk so that the signal processing is easy on the reception side. However, as can be seen from the equations shown so far, if the receiving device has a part that downconverts the information signal using the pilot signal sent from the transmitting side as a local signal, the same effect can be obtained. It is done. Therefore, the same effect can be obtained with a configuration other than up-conversion on the transmission side or down-conversion once on the reception side. That is, the reception frequency converting unit may be any down-converting unit that down-converts an information signal using a pilot signal as a local signal and outputs an output signal.

  Here, an example in which the phase adjustment circuit is not included in the synthesis circuit has been described. However, since the phase control range is significantly narrowed, a variable phase shifter with a narrow phase adjustment range is used with this embodiment. It is also possible.

  The one-dimensional antenna arrangement has been described above by taking a linear array antenna as an example. This embodiment is a technique that is also effective in two-dimensional and three-dimensional antenna arrangements. In the case of a one-dimensional antenna arrangement, even in the prior art, even if it is possible to avoid physical size restrictions by arranging circuits using extra dimensions, two-dimensional or three-dimensional This is because there is no room for spatial arrangement in the synthesis of a typical antenna arrangement.

  As an application example of the present embodiment, use of a microwave or millimeter wave transmission device can be considered. In a millimeter wave transmission apparatus, there are many cases where there is sufficient bandwidth for transmission and there is a degree of freedom in setting pilot signals. By using a gain antenna such as a horn antenna, a synthesis circuit using a linear array antenna having four elements or less, a 2 × 2 element two-dimensional array antenna, or the like can be easily realized.

(Embodiment 2)
FIG. 4 is a configuration diagram of a transmission system for direction of arrival estimation according to the second embodiment. In the transmission system of the present embodiment, the phase difference between the antenna elements can be accurately measured without setting the antenna element interval to a half wavelength or less at the carrier frequency transmitted by radio waves. FIG. 4 does not show a specific circuit configuration, but is a configuration diagram conceptually showing the operation of the apparatus, omitting a filter for selecting a frequency, an amplifier for adjusting a level, and the like.

  The transmission system of the present embodiment includes a single transmission apparatus 100 having a transmission antenna 101, two reception frequency conversion units # 1 and # 2 having reception antenna elements # 1 and # 2, and a reception frequency conversion unit # 1. , # 2 includes a receiving device including a phase difference detection circuit 270 that detects the phase difference of the output signal. In the present embodiment, the description will be made assuming that there are two reception antenna elements and frequency conversion units, but the number of reception antenna elements and frequency conversion units is not limited to two, and there may be a plurality.

In the transmission apparatus 100, a pilot signal (frequency f _p ) is added to an input signal, that is, an information signal (frequency f _i ) to be transmitted by an adder circuit 102 and frequency-multiplexed, and a local signal (frequency f _u ) is mixed by a frequency mixer 103. Up-convert and radiate from the transmitting antenna 101. Thus, as shown in 110 in the figure, up-converted pilot signal (frequency f _{p +} f _u) and upconverted information signal (frequency f _{i +} f _u) is transmitted together with a radio wave. The carrier frequency f, given the center frequency of the information _signal, which is f i + _{f u.}

In the receiving apparatus, receiving antenna elements # 1 and # 2 are arranged. The outputs of receiving antenna elements # 1 and # 2 are connected to receiving frequency converters # 1 and # 2, respectively. Since the reception frequency conversion units # 1 and # 2 have the same configuration, only the reception frequency conversion unit # 1 (210) will be described in detail. In the reception frequency conversion unit 210, the signal received by the reception antenna element # 1 is mixed with the local signal (frequency f _d ) by the frequency mixer 211 and temporarily down-converted to a frequency at which signal processing is easy. Further, the frequency-converted pilot signal (frequency f _p + f _u −f _d ) 222 and the frequency-converted information signal (frequency f _i + f _u −f _d ) 223 are divided, and then the frequency-converted pilot signals are mixed in a frequency mixer 214 (frequency _{f p + f u -f d)} 222 as a local signal, down-converts the frequency-converted information signal (frequency _{f i + f u -f d)} 223. As a result, an output signal 215 having a frequency converted to (f _i −f _p ) is obtained from the output of the reception frequency conversion unit 210. Also in the reception frequency converter # 2, converted output signal frequency in the same manner as the reception frequency conversion unit # 1 is a (f i _{-f p)} is obtained.

In the present embodiment, the configuration of the reception frequency conversion unit # 2 is illustrated as being the same as that of the reception frequency conversion unit # 1, but for the reason described later, the frequency f _d of the local signal for down-conversion is It does not have to coincide with the reception frequency conversion unit # 1.

The receiving antenna element # 1 and the receiving antenna element # 2, the output signal (f i _{-f p)} assumed to be arranged at an interval smaller than a half wavelength of the reception frequency conversion unit # 1 and the reception frequency conversion The phase difference is accurately detected by the phase difference detection circuit 270 from the output signal of the part # 2.

This will be described with specific numerical values. The center frequency f _i of the information signal is 1000 MHz, the frequency f _{p of the} pilot signal is 900 MHz, the frequency f _u of the local signal for up-conversion is 59 GHz, and the frequency f _d of the local signal for down-conversion is 56 GHz. As a result, the carrier frequency is 60 GHz and the wavelength is 5 mm. On the other hand, the center frequency of the output signal of the reception frequency conversion unit becomes 100MHz in _(f i -f _p), it becomes 1/600 of the carrier frequency of the radio waves. In terms of wavelength, it is 600 times (3 m). Therefore, the distance between the receiving antenna element # 1 and the receiving antenna element # 2 may be set to 1.5 m or less which is the half wavelength. However, in reality, it is conceivable that the distance between the antennas is made smaller than 1.5 m in order to correlate the received signals at the two receiving antenna elements. However, it can be set to a larger value than 2.5 mm, which is the half wavelength of the carrier wave.

  Although the frequency relationship has been described above, the relationship including the phase will be described using equations. It is assumed that the signal received by the receiving antenna element # 2 is delayed by the delay time τ compared to the signal received by the receiving antenna element # 1.

A signal received by the receiving antenna element # 1 is given by the following equation, where E _{1p is} an up-converted pilot signal and E _1i is an up-converted information signal. Here, A _01p and A _01i are the amplitudes of the respective signals.

受信アンテナ素子＃２で受信される信号は、アップコンバートされたパイロット信号Ｅ_２ｐ、アップコンバートされた情報信号をＥ_２ｉとすると、次式で与えられる。ここで、Ａ_０２ｐ、Ａ_０２ｉはそれぞれの信号の振幅である。

The signal received by the receiving antenna element # 2 is given by the following equation, where the up-converted pilot signal E _2p and the up-converted information signal are E _2i . Here, A _02p and A _02i are the amplitudes of the respective signals.

アンテナ＃１とアンテナ＃２での情報信号の移相量は、２π（ｆ_ｉ＋ｆ_ｕ）τになる。

The amount of phase shift of the information signal at antenna # 1 and antenna # 2 is 2π (f _i + f _u ) τ.

The local signals E _1d (t) and E _2d (t) for down-conversion with the antennas # 1 and # 2 have different phases and frequencies, and are given by the following equations. Here, D ₀₁ and D ₀₂ are the amplitudes of the respective local signals, f _d1 and f _d2 are the frequencies, and α _1d and α _2d are the phases.

ダウンコンバートされたパイロット信号Ｅ_１ｐｄ、Ｅ_２ｐｄ、情報信号Ｅ_１ｉｄ、Ｅ_２ｉｄは、

The down-converted pilot signals E _1pd , E _2pd , information signals E _1id , E _2id are

である。ここで、Ａ_０１ｐｄ、Ａ_０１ｉｄ、Ａ_０２ｐｄ、Ａ_０２ｉｄはそれぞれの信号の振幅である。

It is. Here, A _01pd , A _01id , A _02pd , and A _02id are the amplitudes of the respective signals.

When the pilot signal obtained above is used as a local signal and the information signal is down-converted, the signals E _1O and E _2O obtained are as follows. Here, A _01O and A _02O are the amplitudes of the respective signals.

E _1O (t) is an output signal of the reception frequency conversion unit # 1, and E _2O (t) is an output signal of the reception frequency conversion unit # 2. These output signals are input to the phase difference detection circuit 270 to detect the phase difference. The amount of phase shift of the information signal obtained by the phase difference detection circuit 270 is 2π (f _i −f _p ) τ, which is (f _i −f _p ) / (f _i + f _u ) compared to when received by radio waves. ) It has doubled. In addition, since the frequency and phase terms of the local signal for down-conversion do not remain, as described above, the local signal used for down-conversion in the receiving device has a different frequency at each reception frequency conversion unit. May be. Furthermore, since the phase difference in the circuit before down-converting the pilot signal as a local signal is canceled, the phase characteristics of components such as amplifiers, filters, and line lengths can be shifted within one wavelength in the total receiving system. It can be seen that it is acceptable.

Here, so as to facilitate the processing of the signals at the receiving side, once noted example to down-convert a frequency f _d. However, as can be seen from the above equation, the amount of phase shift can be greatly reduced at the portion where the information signal is down-converted using the pilot signal sent from the transmission side as the local signal, and the frequency f _d Even if the configuration is not down-converted, the same effect can be obtained. That is, the reception frequency converting unit may be any down-converting unit that down-converts an information signal using a pilot signal as a local signal and outputs an output signal.

  This embodiment is an effective technique even in a two-dimensional or three-dimensional antenna arrangement. For example, in the embodiment shown in FIG. 4, if the arrangement of the receiving antenna is the same as that in FIG. 1, only the θ direction in the paper surface in FIG. 1 is detected, but it is necessary to detect the direction perpendicular to the paper surface. In some cases, antenna elements may be arranged in a direction perpendicular to the paper surface. In addition, since this embodiment detects a phase difference between antenna elements, it can be implemented with two antenna elements in a certain direction. However, if three or more antenna elements are used, detection accuracy is improved. Can be raised.

  As an application example of the present embodiment, use of a microwave or millimeter wave transmission device can be considered. Particularly in the millimeter wave transmission apparatus, the transmission bandwidth is sufficient and the pilot signal setting is flexible, but it is effective for a system that wants to secure a gain as a receiving antenna.

  In the present embodiment, since a conventional method is used as the phase difference detection method, no particular description is given. For example, a method using a phase comparator, a method by signal processing described in Non-Patent Document 2, and the like can be considered.

In the first and second embodiments, the configuration on the transmission side is illustrated by up-converting the pilot signal together with the information signal. However, if the information signal and the pilot signal can be transmitted as radio waves, the above configuration is used. Is not limited. That is, the information signal f _i is up-converted with the local signal f _u together with the pilot signal f _p in substantially the same frequency band and transmitted from the transmission apparatus (FIG. 5A). When only f _i is up-converted with the local signal f _u and a pilot signal f _p having substantially the same frequency as the up-converted information signal (frequency f _i + f _u ) is superimposed (FIG. 5B), the information signal In the case where only f _i is up-converted with the local signal f _u and the local signal used for the up-conversion is superimposed on the up-converted information signal (frequency f _i + f _u ) as a pilot signal (f _p = f _u ) (FIG. 5 (c)) or the like. The same effect can be obtained with these transmission apparatuses. Further, the same effect can be obtained regardless of which of the pilot signal and the information signal is located above or below.

  In the first and second embodiments, the same effect can be obtained by changing the frequency and combination of up-conversion and down-conversion in the frequency conversion between the transmission device and the reception device.

  In the first and second embodiments, the element spacing of the receiving antenna may be sufficiently smaller than the half wavelength at the frequency that is the difference between the pilot signal and the information signal, and sufficiently larger than the half wavelength of the carrier frequency. be able to. Therefore, a receiving antenna having a larger aperture diameter than the half wavelength of the carrier wave, such as a horn antenna or a Cassegrain antenna, can be used as the receiving antenna.

  In the first and second embodiments, the pilot signal superimposed on the information signal in the transmission apparatus is not limited to the pilot signal superimposed for each embodiment, and the pilot signal superimposed on the information signal for other purposes. It may be a signal. For example, a pilot signal that can be separated from an information signal by a filter or other means at the reception frequency converter, and can be used as long as the information signal can be down-converted using the pilot signal as a local signal.

  In the first and second embodiments, the transmission device and the reception frequency conversion unit may be configured by a circuit or a program stored in a computer and a storage device. Further, the same function may be realized by using a program stored in a computer and a storage device instead of the synthesis circuit of the first embodiment and the phase difference detection circuit of the second embodiment.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Of course.

Diagram for explaining a conventional array antenna system Conceptual configuration diagram of a conventional transmission system for direction of arrival estimation 1 is a conceptual configuration diagram of a transmission system according to a first embodiment of the present invention. Conceptual configuration diagram of a transmission system for direction-of-arrival estimation according to Embodiment 2 of the present invention. 1 is a conceptual configuration diagram of a transmission side according to an embodiment of the present invention.

Explanation of symbols

100 ... transmitting apparatus, 101 ... transmitting antenna, 102 ... adder circuit, 103 ... frequency mixer, 110 ... upconverted pilot signal (frequency _f p + _{f u)} and upconverted information signal (frequency _f i _{+ f} u), 210 ... reception frequency conversion unit, 211 ... frequency mixer, 212 ... frequency-converted pilot signal (frequency _{f p + f u -f d1)} , 213 ... frequency-converted information signal (frequency _{f i + f u -f d1)} , 214 ... frequency mixer, 215 ... output signal (frequency f _i -f _p ) of the frequency converter, 222 ... frequency-converted pilot signal (frequency f _p + f _u -f _d ), 223 ... frequency-converted information signal ( frequency _{f i + f u -f d)} , 260 ... synthetic circuit, 270 ... phase difference detecting circuit

Claims (10)

A transmission system having a transmitter and a receiver,
The transmitter comprises means for transmitting a pilot signal superimposed on an information signal,
The receiving device is:
A plurality of receiving antenna elements for receiving a signal in which a pilot signal is superimposed on the information signal;
A plurality of down-converting means for receiving signals respectively received by the plurality of receiving antenna elements, down-converting the information signal using the pilot signal as a local signal, and outputting an output signal;
Combining means for combining the output signals of the plurality of down-converting means;
A transmission system comprising: A transmission system having a transmitter and a receiver,
The transmitter comprises means for transmitting a pilot signal superimposed on an information signal,
The receiving device is:
A plurality of receiving antenna elements for receiving a signal in which a pilot signal is superimposed on the information signal;
A plurality of down-converting means for receiving signals respectively received by the plurality of receiving antenna elements, down-converting the information signal using the pilot signal as a local signal, and outputting an output signal;
A phase difference detecting means for detecting a phase difference between receiving antenna elements using output signals of the plurality of down-converting means;
A transmission system comprising: A receiving device for receiving a signal in which a pilot signal is superimposed on an information signal,
A plurality of receiving antenna elements for receiving a signal in which a pilot signal is superimposed on the information signal;
A plurality of down-converting means for receiving signals respectively received by the plurality of receiving antenna elements, down-converting the information signal using the pilot signal as a local signal, and outputting an output signal;
Combining means for combining the output signals of the plurality of down-converting means;
A receiving apparatus comprising: A receiving device for receiving a signal in which a pilot signal is superimposed on an information signal,
A plurality of receiving antenna elements for receiving a signal in which a pilot signal is superimposed on the information signal;
A plurality of down-converting means for receiving signals respectively received by the plurality of receiving antenna elements, down-converting the information signal using the pilot signal as a local signal, and outputting an output signal;
A phase difference detecting means for detecting a phase difference between receiving antenna elements using output signals of the plurality of down-converting means;
A receiving apparatus comprising:   5. The reception apparatus according to claim 3, wherein the signal in which a pilot signal is superimposed on the information signal is a signal up-converted using a local signal having a first frequency on the transmission side. apparatus.   6. The receiving apparatus according to claim 3, wherein the down-conversion unit temporarily down-converts a signal in which a pilot signal is superimposed on the information signal using a local signal having a second frequency. Thereafter, the information signal once down-converted is down-converted using the pilot signal once down-converted as a local signal.   7. The receiving apparatus according to claim 3, wherein an interval between receiving antenna elements is larger than a half wavelength at a carrier frequency, and a half wavelength at a frequency that is a difference between the pilot signal and the information signal. A receiving apparatus characterized in that the receiving apparatus is installed at a value that is shorter than that.   The receiving apparatus according to claim 3, wherein the frequency of the information signal or the frequency of the pilot signal is such that the maximum value of the phase difference in the receiving antenna element is equal to or less than a predetermined value in the frequency of the output signal of the down-conversion means. Alternatively, a receiving apparatus in which an interval between receiving antenna elements or the number of elements to be combined is set.   9. The receiving apparatus according to claim 3, wherein the receiving antenna element has an aperture diameter larger than a half wavelength of a carrier wave. The receiving apparatus according to any one of claims 3 to 9, wherein the receiving antenna elements are arranged two-dimensionally or three-dimensionally.

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