JP5141480B2 - Transmitting apparatus and transmitting method - Google Patents

Description

  The present invention relates to a transmission apparatus and a transmission method, and can be applied to, for example, a transmission signal and a transmission method for combining a plurality of transmission signals and outputting a transmission wave from one antenna. In particular, it is suitable when a communication form called Matrix A in a wireless communication system such as WiMAX (registered trademark) is used.

  In general, WiMAX is a communication system based on a wireless communication technology standardized by IEEE 802.16 and IEEE 802.16e.

  In WiMAX, there is a communication form that uses a technique called space time coding (STC). The STC technology is one embodiment of MIMO (Multiple Input Multiple Output), which is a technology that uses multiple inputs and multiple outputs simultaneously.

FIG. 2 shows a configuration of a normal wireless device. 2 includes a baseband circuit unit 51 having a function of converting transmission / reception data, which is a digital signal, into a baseband analog I / Q signal (hereinafter referred to as an I / Q signal) or reverse conversion. , A transmission circuit unit (represented as Tx) 52 that converts an I / Q signal into a high frequency band signal (hereinafter referred to as an RF signal), and a reception circuit unit (represented as Rx) that converts an RF signal into an I / Q signal. There are one system 53 and a Tx / Rx changeover switch 54 for switching between Tx and Rx, and one antenna 55.

  FIG. 3 is a diagram illustrating a communication form of the two wireless devices A and B having the configuration of FIG. As shown in FIG. 3, the signal transmitted from the antenna of the wireless device A is received by the antenna of the wireless device B, and conversely, the signal transmitted from the antenna of the wireless device B is received by the antenna of the wireless device A. Is done. Therefore, the relationship between Tx and Rx is 1: 1. Here, such a communication form is expressed as 1Tx × 1Rx.

On the other hand, FIG. 4 shows a configuration example of a wireless device in the case of a communication form using STC technology. Configuration of the wireless device shown in FIG. 4, as compared with the configuration shown in FIG. 3, first, a transmission circuit section (Tx) 62- 1 and antenna 65-2 is added 1 line. Further, the baseband circuit unit 61 is provided with a circuit unit (function) that converts transmission data into two systems of I / Q signals (I / Q signal 1 and I / Q signal 2) simultaneously. The two systems of I / Q signal 1 and I / Q signal 2 are converted into RF signal 1 and RF signal 2 at Tx 62-1 and 62-2, respectively, and transmitted simultaneously from antenna 65-1 and antenna 65-2. The

During transmission, the Tx / Rx changeover switch 64 connects the transmission circuit unit 62-1 and the antenna 65-1, and the reception circuit unit 63 stops operating during this time. On the other hand, at the time of reception, the Tx / Rx changeover switch 64 connects the antenna 65-1 and the reception circuit unit 63, and the transmission circuit units 62-1 and 62-2 stop operating in both systems, and only the reception circuit unit 63 is connected. Operate.

  FIG. 5 shows a communication form between the wireless device C having the configuration shown in FIG. 4 and the wireless device B having the configuration shown in FIG. In FIG. 5, in this case, the transmission signals transmitted from the two antennas of the wireless device C are received by the single antenna of the wireless device B. This communication form is called Matrix A in WiMAX, and is expressed as 2Tx × 1Rx here.

Features of the Matrix A communication mode will be described with reference to the drawings. As described above, in FIG. 5, the wireless device C transmits another signal from the two antennas. Therefore, two signals are transmitted at the same time. However, in the STC technique, as shown in FIG. 6, a signal corresponding to the complex conjugate of the first signal is repeatedly transmitted in the second transmission, so the transmission speed itself is It is not different from the communication mode of FIG.

Here, notation S ₁ ^* indicates that S ₁ ^* have the relationship of S ₁ and the complex conjugate, since, unless specified individually, such a case where the notation, both the relationship Shall have.

When a signal is transmitted from the wireless device C in the relationship of FIG. 6, assuming that a signal received by the wireless device B at the first time is r ₁ and a signal received at the second time is r ₂ , the following equation (1) is obtained. The determinant shown holds.

Here, h ₁ is the transfer coefficient of the path 1 in FIG. 5, h ₂ is the transfer coefficient of the path 2 in FIG. 5, and h ₁ and h ₂ are both represented by complex numbers. Further, when H is placed as shown in Equation (2-1) and the complex conjugate transpose matrix H ^* is used, Equation (2-2) is obtained.

Equation ( 2-2 ) shows that the received signal (S ₁ and S ₂ ) can be restored by multiplying the signal (S ₁ and S ₂ ) by (| h ₁ | ² + | h ₂ | ² ) by calculating the received signal. ing. (| H ₁ | ² + | h ₂ | ² ) corresponds to the diversity gain.

  As described above, in the Matrix A communication mode, the transmission rate itself is the same as that of the communication mode of FIG. 3, but there is an effect of obtaining a diversity gain, and an improvement in transmission characteristics is expected.

IEEE 802.16, 8.4.8 Transmit Diversity (Optional), p. 579

  However, when the Matrix A communication mode using the STC technology is implemented using the configuration shown in FIG. 4 described above, two transmission circuits 62-1 and 62-2 and two transmission circuits 62-1 and 62-2 are provided in the wireless device on the transmission side. Antennas 65-1 and 65-2 are required. That is, it is essential to increase the circuit scale of the transmission system. This leads to an increase in the number of components and mounting area, which is a big demerit particularly in an apparatus that is required to be downsized such as a mobile terminal.

  Therefore, there is a demand for a transmission apparatus and a transmission method that can improve transmission characteristics while greatly reducing the circuit scale.

In order to solve such problems, a first transmission device of the present invention, the (1) to generate an in-phase and quadrature signals of the signals of a plurality of systems from the input digital signal a plurality of baseband analog signals A baseband circuit unit that generates simultaneously; and (2) a combined in-phase signal is generated by combining the in-phase signals of the baseband analog signals with a predetermined gain relationship, and quadrature signals of the baseband analog signals are generated. (1) one transmission for generating a transmission signal by performing quadrature modulation using the combined in-phase signal and the combined quadrature signal combined by the adding unit; A circuit unit and (4) one antenna means for transmitting a transmission signal from the transmission circuit unit are provided.

A transmission method according to a second aspect of the present invention is a transmission method of a transmission apparatus including a baseband circuit unit , an adding unit, one transmission circuit unit, and one antenna unit, and (1) the baseband circuit unit is input. Generating in-phase signals and quadrature signals of a plurality of systems from the digital signal, and simultaneously generating a plurality of baseband analog signals; and (2) an adding means is configured to generate in-phase signals of the baseband analog signals. Generating a combined in-phase signal by combining with a predetermined gain relationship, and generating a combined orthogonal signal by combining the quadrature signals of the baseband analog signals with a predetermined gain relationship; part is to send and generating a transmission signal quadrature modulated by using the synthetic phase signal and combining the orthogonal signal synthesized by the addition means, antenna means, a transmission signal from the transmitter unit Characterized by a step.

  According to the present invention, it is possible to improve transmission characteristics while significantly reducing the circuit scale.

(A) 1st Embodiment Below, it demonstrates, referring drawings for 1st Embodiment of the transmitter and transmission method of this invention.

(A-1) Configuration of First Embodiment FIG. 1 is a configuration diagram illustrating a configuration of a wireless device 10 according to the first embodiment. In FIG. 1, a radio apparatus 10 according to the first embodiment includes a baseband circuit unit 11, a transmission circuit unit 12, a reception circuit unit 13, a Tx / Rx changeover switch unit 14, an antenna unit 15, an adder 16, and a modulation unit 17. At least.

  Compared to the configuration of the wireless device shown in FIG. 4, the wireless device 10 shown in FIG. 1 deletes the transmission circuit 62-2 and the antenna 65 that transmit the I / Q signal 2, and instead uses two I / Q signals. The configuration is different in that an adder 16 is added.

  The baseband circuit unit 11 corresponds to a baseband IC such as a baseband signal processing circuit, and generates transmission data that is a digital signal from an in-phase component I component and a quadrature component Q component. One baseband analog I / Q signal is converted and given to the adder 16. At this time, the baseband circuit unit 11 supplies two transmission signals 1 (I / Q signal 1) and transmission signal 2 (I / Q signal 2) to the adder 16 simultaneously from the transmission data. The baseband circuit unit 11 converts the baseband analog I / Q signal from the receiving circuit 13 back to received data that is a digital signal and outputs it.

  The transmission circuit unit 12 includes at least an adder 16 and a modulation unit 17.

  The adder 16 corresponds to a general adder using an OP amplifier, and is added to the transmission circuit unit 12 in the first embodiment.

  Further, the adder 16 takes in the transmission signal 1 (I / Q signal 1) and the transmission signal 2 (I / Q signal 2) from the baseband circuit unit 11, and transmits these transmission signals 1 (I / Q signal 1) and transmission. Signal 2 (I / Q signal 2) is added in a predetermined gain relationship, and a combined I / Q signal is output.

  Here, the adder 16 adds the transmission signal 1 (I / Q signal 1) and the transmission signal 2 (I / Q signal 2) by the relationship of, for example, the expression (3).

I / Q signal 1: I / Q signal 2 = k: 1 (3)
Note that k is a positive real number.

  FIG. 7 is a configuration diagram showing a circuit configuration of the adder 16. FIG. 7 illustrates the simplest configuration of the adder 16 for convenience of explanation.

  7A shows a circuit configuration in which the I component of the I / Q signal 1 and the I component of the I / Q signal 2 are added, and FIG. 7B shows the Q component of the I / Q signal 1 and the I component. / Q signal 2 is a circuit configuration for adding the Q component. As shown in FIGS. 7A and 7B, the adder 16 adds the I and Q components of the I / Q signal 1 and I / Q signal 2 respectively.

  In FIG. 7A, the adder 16 is a circuit that feeds back the output of the OP amplifier 24, and has an input terminal 21 for inputting the I component of the I / Q signal 1 and one end connected to the input terminal 21. A resistor R1 whose other end is connected to the + terminal (non-inverting input terminal) of the OP amplifier 24, an input terminal 22 for inputting the I component of the I / Q signal 2, and one end connected to the input terminal 22 and the other end Is connected to the + terminal (non-inverting input terminal) of the OP amplifier 24, and has one end connected to the output terminal of the OP amplifier 24 and the other end connected to the-terminal (inverting input terminal) of the OP amplifier 24. R3 and a resistor R4 having one end connected to the negative terminal (inverting input terminal) of the OP amplifier 24 and the other end grounded. Note that the structure illustrated in FIG. 7B is also a structure corresponding to FIG. 7A, and a detailed description thereof is omitted here.

  7A and 7B, the resistance value of the resistor R2 satisfies the relationship R2 = k · R1. Thereby, the relationship of said Formula (3) is materialized. When the I / Q signal is a balance signal, an adder for the balance signal is configured.

  The modulation unit 17 receives the synthesized I / Q signal from the adder 16 and converts it into a high frequency band signal (RF signal). The modulation unit 17 corresponds to, for example, a quadrature modulator such as QAM or OFDM.

  The reception circuit unit 13 receives a reception signal (RF signal) captured by the antenna 15 via the Tx / Rx changeover switch 14 and converts it into an I / Q signal. The reception circuit unit 13 corresponds to a general reception circuit, and includes a demodulation processing unit, a filter unit that removes unnecessary components, an amplifier, and the like.

The Tx / Rx changeover switch unit 14 is a switch that switches a route to the transmission circuit unit 12 or the reception circuit unit 13.

The antenna unit 15 transmits a transmission signal from the transmission circuit unit 12 via the Tx / Rx changeover switch unit 14 or captures a radio wave and receives a reception signal via the Tx / Rx changeover switch unit 14. It is something to give to.

(A-2) Operation of the First Embodiment Next, the operation of processing in the wireless device 10 of the first embodiment will be described with reference to the drawings.

  In FIG. 1, first, when transmission data is input to the baseband circuit unit 11, two systems of I / Q signal 1 and I / Q signal 2 are generated by the baseband circuit unit 11.

  Here, the I / Q signal 1 and the I / Q signal 2 generated by the baseband circuit unit 11 have the relationship shown in FIG.

That is, for the I and Q components of I / Q signal 1, the first transmission signal is _SBB1I and _SBB1Q , and the second transmission signal is _-SBB2I and _SBB2Q . Similarly, for the I and Q components of the I / Q signal 2, the first transmission signal is _SBB2I and _SBB2Q , and the second transmission signal is _-SBB1I and _SBB1Q .

  Here, when the relationship shown in FIG. 8 is applied to the conventional radio apparatus shown in FIG. 4, the transmission signal 1 and the transmission signal 2 have the following relationship.

In the first _{transmission,} is input to the _{S BB1I} the transmission circuit unit 62-1, the orthogonal modulation result, the transmission signal _(hereinafter referred to as _{S 1_1)} becomes Equation (4).

  Where fc is the center frequency of the transmission wave.

Also, S _BB2I and S _BB2Q are input to the transmission circuit unit 62-2, and as a result of the orthogonal modulation, a transmission signal (hereinafter, referred to as S _{2_1} ) is expressed by Equation (5).

Next, in the second transmission, when the transmission signal of the transmission circuit unit 62-1 is S _{1_2} and the transmission signal of the transmission circuit unit 62-2 is S _{2_2} , similarly, the I / Q signal shown in FIG. (6) and (7).

  On the other hand, in the first embodiment, two systems of I / Q signal 1 and I / Q signal 2 are input to the adder 16. In the adder 16 having the configuration illustrated in FIGS. 7A and 7B, the I component and the Q component of the I / Q signal 1 and the I / Q signal 2 are added. As a result of addition by the adder 16, the I component and the Q component of the synthesized I / Q signal are expressed by Equation (8) and Equation (9).

I component of the synthesized I / Q signal = A / (1 + k) · (k · S _BB1I + S _BB2I ) (8)
Q component of synthesized I / Q signal = A / (1 + k) · (k · S _BB1Q + S _BB2Q ) (9)
Here, A corresponds to the gain (closed loop gain) of the adder 16, and when the adder 16 has the configuration illustrated in FIGS. 7A and 7B, A = (R3 + R4) / R4.

When the output signal of the adder 16 is given to the transmission circuit unit 12, the modulation unit 17 performs a quadrature modulation of the carrier wave with the I component and the Q component of the synthesized I / Q signal and represents the transmission signal (hereinafter referred to as _ST1 ). ), Which is the expression (10).

Here, when the transmission signals S ₁ and S ₂ in the case of the wireless device having the configuration shown in FIG. 4 are applied to Expression (10), Expression (11) is obtained.

S _T1 = A / (1 + k) · (k · S ₁ + S ₂ ) (11)
From the above equation (11), it can be seen that S ₁ and S ₂ are added at a ratio of k: 1. In the first transmission, the signal S _T1 is output from the modulation unit 17 of the transmission circuit unit 12 and transmitted from the antenna unit 15.

  Similarly, in the case of the second transmission, the output of the adder 16 is expressed by the following equations (12) and (13).

I component of the synthesized I / Q signal = A / (1 + k) · (k · (−S _BB2I ) + S _BB1I ) (12)
Q component of synthesized I / Q signal = A / (1 + k) · (k · S _BB2Q −S _BB1Q ) (13)
Therefore, the second transmission signal (represented as S _T2 ) can be represented by Expression (14).

  In the second transmission, the signal ST2 is output from the modulation unit 17 of the transmission circuit unit 12 and transmitted from the antenna unit 15.

Next, the reception process of the wireless device 10 according to the first embodiment will be described. Assuming that the _first received signal is r ₁ , the second received signal is r ₂ , and the transfer coefficient from the transmitting device to the receiving device is h ₃ , equations (15) and (16) are obtained.

r ₁ = h ₃ · S _T1 = h ₃ · A / (1 + k) · (k · S ₁ + S ₂ ) (15)
r ₂ = h ₃ · S _T2 = h ₃ · A / (1 + k) · {k · (−S ₂ ^* ) + S ₁ ^* } (16)
Here, the relationship of Expression (17) is established from r ₂ ^* = h ₃ ^* · A / (1 + k) · {S ₁ + k · (−S ₂ )}.

This equation (17) has the following relationship with respect to h ₁ and h _{2 in the} following determinant (18-1) in the Matrix A communication mode described above.

  Therefore, in the receiving apparatus, the original signal can be restored by performing arithmetic processing in the same manner as in the case of the conventional radio apparatus shown in FIG.

Further, as described above, when equation (19-1) is set for H, equation (19-2) is obtained using the complex conjugate transpose matrix H ^* .

That is, since the diversity gain is (| h ₁ | ² + | h ₂ | ² ), in the case of the first embodiment, the diversity gain is represented by Expression (20).

When the resistance of the adder 16 is set so that A ² · (1 + k ² ) / (1 + k) ² > 1 holds, the equation (20) has a value greater than or equal to the transmission coefficient | h ₃ | ^{2 of} the transmission path. It shows that. Therefore, the receiving apparatus can be regarded as having obtained one or more diversity gains.

(A-3) Effect of First Embodiment As described above, in the conventional configuration (2Tx × 1Rx), it is necessary to provide the transmission apparatus with two transmission circuits and two antenna units. According to the first embodiment, since it can be realized by one transmission circuit and one antenna unit, the circuit scale can be greatly reduced.

  Further, in the conventional configuration, since transmission is performed by two paths from the two antenna units, even if the propagation loss of one path increases due to fading or the like, there is an antenna diversity effect that is compensated by the other path. In the first embodiment, the effect is lost. Therefore, it is expected that the propagation characteristics are inferior to the original configuration of Matrix A (2Tx × 1Rx). However, according to the first embodiment, the diversity gain by the STC technology can be equivalently obtained when compared with a communication mode that does not use the 1Tx × 1Rx STC technology that transmits by only one antenna unit. The transmission characteristics can be improved.

(B) Second Embodiment Next, a second embodiment of the transmission apparatus and the transmission method of the present invention will be described with reference to the drawings.

(B-1) Configuration and Operation of Second Embodiment FIG. 9 is a configuration diagram showing the configuration of the wireless device 20 of the second embodiment. In FIG. 9, the wireless device 20 according to the first embodiment includes at least a baseband circuit unit 21, a transmission circuit unit 22, a reception circuit unit 13, a Tx / Rx changeover switch unit 14, an antenna unit 15, and a modulation unit 17. It is.

The wireless device 20 of the second embodiment is different from the wireless device 10 of the first embodiment in that the baseband circuit unit 21 has an addition function 211 that combines the generated two systems of I / Q signals into one signal. It is a point to prepare. In addition, the transmission circuit unit 22 is configured not to include the adder 16 of the first embodiment. The receiving circuit unit 13, the Tx / Rx changeover switch unit 14, and the antenna unit 15 are the same as those in the first embodiment, and thus detailed description thereof is omitted here.

As in the first embodiment, the baseband circuit unit 21 corresponds to a baseband IC that performs baseband signal processing, and simultaneously transmits two transmission signals 1 (I / Q signal 1) and transmission signal 2 ( I / Q signal 2) is generated.

  The addition function 211 of the baseband circuit unit 21 combines the I signal of the transmission signal 1 and the I signal of the transmission signal 2 and also combines the Q signal of the transmission signal 1 and the Q signal of the transmission signal 2. When the addition function 211 combines the I signal and the Q signal of the transmission signal 1 (I / Q signal 1) and the transmission signal 2 (I / Q signal 2), the addition function 211 The I / Q signal 2 is combined with a predetermined gain. As a result, a signal obtained by synthesizing the two systems of I / Q signals can be given to the transmission circuit unit 12, so that the same effect as in the first embodiment can be obtained.

(B-2) Effects of the Second Embodiment As described above, according to the second embodiment, an adder is provided to add two systems of I / Q signals with the arithmetic function of the baseband circuit. The effect similar to 1st Embodiment can be show | played without being required. As a result, a more advanced arithmetic processing function is required, but further reduction of the circuit scale can be expected as compared with the first embodiment.

(C) Other Embodiments The first and second embodiments exemplify cases where the present invention is applied to a WiMAX Matrix A communication mode. However, each of the first and second embodiments has two transmission circuits and two I / Q signals. Any communication apparatus that orthogonally modulates a carrier wave and outputs it at the same time can be widely applied regardless of whether it is wireless or wired.

It is a block diagram which shows the structure of the radio | wireless apparatus of 1st Embodiment. It is a block diagram which shows the structure of the conventional radio | wireless apparatus. It is explanatory drawing explaining the communication form between the conventional radio | wireless apparatuses. It is a block diagram which shows the structure of the radio | wireless apparatus using the conventional STC technique. It is explanatory drawing explaining the communication form (Matrix A) between the radio | wireless apparatus using the conventional STC technique, and a normal radio | wireless apparatus. It is explanatory drawing explaining the relationship of the transmission signal in the communication form of Matrix A. FIG. It is a block diagram which shows the structure of the adder of 1st Embodiment. It is explanatory drawing explaining the relationship of the transmission signal in the communication form of 1st Embodiment. It is a block diagram which shows the structure of the radio | wireless apparatus of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 and 20 ... Wireless apparatus, 11 and 21 ... Baseband circuit part , 211 ... Addition function, 12 and 22 ... Transmission circuit part, 13 ... Reception circuit part, 14 ... Tx / Rx changeover switch part, 15 ... Antenna part, 16 ... adder, 17 ... modulation section.

Claims (4)

And a baseband circuit unit for generating simultaneously a plurality of baseband analog signals from the input digital signal to generate an in-phase and quadrature signals of a plurality of systems of signals,
The in-phase signals of the baseband analog signals are combined with a predetermined gain relationship to generate a combined in-phase signal, and the quadrature signals of the baseband analog signals are combined with a predetermined gain relationship to generate a combined quadrature. Adding means for generating a signal;
One transmission circuit unit that generates a transmission signal by performing quadrature modulation using the combined in-phase signal and the combined quadrature signal combined by the adding unit;
One transmission means for transmitting the transmission signal from the transmission circuit section . A transmission apparatus comprising: 2. The transmission apparatus according to claim 1, wherein the adding means is provided in the transmission circuit unit as an adder. 2. The transmission apparatus according to claim 1, wherein the adding means is realized as an arithmetic processing function of the baseband circuit unit . A transmission method of a transmission device including a baseband circuit unit , an adding unit, one transmission circuit unit, and one antenna unit,
A step of the baseband circuit unit generates an in-phase and quadrature signals of the input from the digital signal of the plurality of channels signals to generate a plurality of baseband analog signals at the same time,
The adding means combines the in-phase signals of the baseband analog signals with a predetermined gain relationship to generate a combined in-phase signal, and the quadrature signals of the baseband analog signals with a predetermined gain relationship. Combining to generate a combined orthogonal signal;
The transmission circuit unit generates a transmission signal by performing quadrature modulation using the combined in-phase signal and the combined quadrature signal combined by the adding unit;
The antenna means comprises a step of transmitting the transmission signal from the transmission circuit section .

Images