Signal generator, signal generating system, and signal generating method

To provide a signal generator, a signal generating system, and a signal generating method capable of repeatedly generating an arbitrary waveform and making the phases of the head and tail of the generated waveform continuous with each other, without changing the frequency of the waveform.A signal generator (10, 11, 12) includes phase shift means (30) that receives waveform data which is repeatedly output n times, shifts the phase of each sample data item in an n-th waveform data item by a phase shift amount φn corresponding to the number of times n the waveform data is repeatedly output, and outputs the waveform data to D/A conversion means.

TECHNICAL FIELD

The present invention relates to a signal generator, a signal generating system, and a signal generating method for outputting an RF test signal to a wireless communication device, which is a test target, to test the wireless communication device.

BACKGROUND ART

Signal generators have been known which transmit a test signal of a communication scheme corresponding to a wireless communication device to the wireless communication device in order to test the wireless communication device. For example, there is a signal generator which stores a baseband signal corresponding to the test signal as digital waveform data in a memory unit thereof, repeatedly outputs the stored waveform data, performs D/A conversion on the waveform data, performs frequency conversion on the converted signal, and outputs the frequency-converted signal as an RF test signal.

In the signal generator, since the capacity of the memory unit is limited, the length of the waveform data is finite. In some cases, it is difficult to freely change the length of the waveform data, for example, since the test conditions for the wireless communication device are defined by a standard. Therefore, in the signal generator according to the related art, a phenomenon in which the phase is discontinuous in a connection portion between the head and tail of the waveform data which is repeatedly output occurs. In this case, there is a concern that spurious emissions will occur at the point where the phase is discontinuous and wireless communication will be asynchronous, which makes it difficult to normally test the wireless communication device.

FIG. 13is a conceptual diagram illustrating the phenomenon.FIG. 13shows a waveform when waveform data W including M sample data items D1to DMis repeatedly output three times and is D/A-converted. Since there is a large difference between the phase of the first sample data item D1and the phase of the last sample data item DMin the waveform data W, the phase of the D/A-converted waveform is discontinuous in a connection portion between the first repeated waveform data and the second repeated waveform data and a connection portion between the second repeated waveform data and the third repeated waveform data.

In order to solve the problems, an arbitrary waveform signal generating device has been proposed which generates an FSK (Frequency Shift Keying) signal with a waveform pattern in which the phase is continuous in the connection portion (for example, see Patent Document 1). The arbitrary waveform signal generating device includes a digital data generator that repeatedly outputs a PN (Pseudo-Noise) signal and correction means that separately adds a correction value to each bit of the output data of the digital data generator, and can generate an FSK signal in which the phase is continuous in the connection portion.

RELATED ART DOCUMENT

Patent Document

DISCLOSURE OF THE INVENTION

Problem that the Invention is to Solve

However, the technique disclosed in Patent Document 1 has a problem in that, since data is corrected such that the phase is continuous in the connection portion, the frequency of the output signal is changed and it is difficult to accurately test the wireless communication device.

The invention has been made in view of the above-mentioned problems and an object of the invention is to provide a signal generator, a signal generating system, and a signal generating method capable of repeatedly generating an arbitrary waveform such that the phase of the tail of the generated waveform and the phase of the head of the next waveform which is repeatedly generated are continuous with each other, without changing the frequency of the waveform, in order to accurately test a wireless communication device.

Means for Solving Problem

In order to achieve the object, according to an aspect of the invention, a signal generator (10,11,12) includes: waveform data storage means (20) for storing waveform data of a digital baseband signal including M sample data items and repeatedly and continuously outputting the waveform data; D/A conversion means (40) for performing digital-analog conversion on the waveform data; frequency conversion means (60,70) for performing frequency conversion on the digital-analog-converted baseband signal using a carrier signal with a predetermined frequency and outputting the frequency-converted signal as an RF test signal for testing a wireless communication device; and phase shift means (30) that receives the waveform data which is repeatedly output n times from the waveform data storage means, shifts the phase of each sample data item in an n-th waveform data item by a phase shift amount φncorresponding to the number of times n the waveform data is repeatedly output, and outputs the waveform data to the D/A conversion means. The phase shift amount φnis calculated from a reference phase difference θ, which is a phase difference between an (n−1)-th waveform data item and the n-th waveform data item, and the number of times n the waveform data is repeatedly output in order to obtain a continuous phase change between the tail of the (n−1)-th waveform data item and the head of the n-th waveform data item.

The signal generator according to the above-mentioned aspect of the invention may further include reference phase difference determining means (23) for determining the reference phase difference θ on the basis of the waveform data stored in the waveform data storage means.

In the signal generator according to the above-mentioned aspect of the invention, the reference phase difference determining means may include: phase estimating means (82) for estimating the phase of an (M+1)-th sample data item on the basis of the phase of an M-th sample data item and the phase of an (M−1)-th sample data item from the head of the waveform data; and reference phase difference calculating means (83) for calculating the reference phase difference θ from a difference between the phase of a first sample data item and the phase of the (M+1)-th sample data item in the waveform data.

In the signal generator according to the above-mentioned aspect of the invention, the reference phase difference determining means may include: average phase difference calculating means (81) for calculating an average phase difference per sample data item of the waveform data; phase estimating means (82) for estimating the phase of an (M+1)-th sample data item on the basis of the phase of an M-th sample data item from the head of the waveform data and the average phase difference; and reference phase difference calculating means (83) for calculating the reference phase difference θ from a difference between the phase of a first sample data item and the phase of the (M+1)-th sample data item in the waveform data.

According to another aspect of the invention, a signal generating system includes the above-mentioned signal generator; and a waveform data generating device (90) that generates the waveform data and transmits the waveform data to the signal generator. The waveform data generating device includes: waveform data generating means (92) for generating the waveform data; reference phase difference determining means (93) for determining the reference phase difference θ; and waveform data transmitting means (94) for transmitting the waveform data and the reference phase difference θ to the signal generator.

In the signal generating system according to the above-mentioned aspect of the invention, the reference phase difference determining means may include: phase estimating means (82) for estimating the phase of an (M+1)-th sample data item on the basis of the phase of an M-th sample data item and the phase of an (M−1)-th sample data item from the head of the waveform data; and reference phase difference calculating means (83) for calculating the reference phase difference θ from a difference between the phase of a first sample data item and the phase of the (M+1)-th sample data item in the waveform data.

In the signal generating system according to the above-mentioned aspect of the invention, the reference phase difference determining means may include: average phase difference calculating means (81) for calculating an average phase difference per sample data item of the waveform data; phase estimating means (82) for estimating the phase of an (M+1)-th sample data item on the basis of the phase of an M-th sample data item from the head of the waveform data and the average phase difference; and reference phase difference calculating means (83) for calculating the reference phase difference θ from a difference between the phase of a first sample data item and the phase of the (M+1)-th sample data item in the waveform data.

In the signal generating system according to the above-mentioned aspect of the invention, the waveform data generating means may generate first to M-th sample data items, acquire the phase of an (M+1)-th sample data item, and generate the waveform data using the generated M sample data items. The reference phase difference determining means may include reference phase difference calculating means (83) for calculating the reference phase difference θ from a difference between the phase of the first sample data and the phase of the (M+1)-th sample data item in the waveform data.

According to still another aspect of the invention, a signal generating method includes: a step (S9) of repeatedly and continuously outputting waveform data of a digital baseband signal including M sample data items; a step (S11) of performing digital-analog conversion on the waveform data; a step (S12) of performing frequency conversion on the digital-analog-converted baseband signal using a carrier signal with a predetermined frequency and outputting the frequency-converted signal as an RF test signal for testing a wireless communication device; a step (S7) of, when the number of times the waveform data is repeatedly output is n, calculating a phase shift amount φncorresponding to the number of times n the waveform data is repeatedly output; and a step (S10) of shifting the phase of each sample data item in an n-th waveform data item by the phase shift amount φnwhen the waveform data which is repeatedly output n times is received before the digital-analog conversion step. The phase shift amount φnis calculated from a reference phase difference θ, which is a phase difference between an (n−1)-th waveform data item and the n-th waveform data item, and the number of times n the waveform data is repeatedly output in order to obtain a continuous phase change between the tail of the (n−1)-th waveform data item and the head of the n-th waveform data item.

The signal generating method according to the above-mentioned aspect may further include a step (S3) of determining the reference phase difference θ on the basis of the waveform data.

In the signal generating method according to the above-mentioned aspect of the invention, the step of determining the reference phase difference θ may include: a step (S23) of estimating the phase of an (M+1)-th sample data item on the basis of the phase of an M-th sample data item and the phase of an (M−1)-th sample data item from the head of the waveform data; and a step (S24) of calculating the reference phase difference θ from a difference between the phase of a first sample data item and the phase of the (M+1)-th sample data item in the waveform data.

In the signal generating method according to the above-mentioned aspect of the invention, the step of determining the reference phase difference θ may include: a step (S32) of calculating an average phase difference per sample data item of the waveform data; a step (S34) of estimating the phase of an (M+1)-th sample data item on the basis of the phase of an M-th sample data item from the head of the waveform data and the average phase difference; and a step (S35) of calculating the reference phase difference θ from a difference between the phase of a first sample data item and the phase of the (M+1)-th sample data item in the waveform data.

The signal generating method according to the above-mentioned aspect may further include: a step (S41) of generating first to M-th sample data items and acquiring the phase of (M+1)-th sample data; a step (S42) of generating the waveform data using the generated M sample data items; and a step (S44) of calculating the reference phase difference θ from a difference between the phase of the first sample data item and the phase of the (M+1)-th sample data item in the waveform data.

Advantage of the Invention

The signal generator, the signal generating system, and the signal generating method according to the invention are capable of repeatedly generating an arbitrary waveform such that the phase of the tail of the generated waveform and the phase of the head of the next waveform which is repeatedly generated are continuous with each other, without changing the frequency of the waveform.

BEST MODE FOR CARRYING OUT THE INVENTION

First, the concept of the invention will be described with reference toFIG. 1.FIG. 1shows a waveform when waveform data W including M sample data items D1to DMis repeatedly output three times and is D/A-converted. When the first repeated waveform data W is W1, the second repeated waveform data W is W2, and the third repeated waveform data W is W3, the phase of each of the sample data items D1to DMin the waveform data W is shifted by a phase shift amount φncorresponding to the number of times n the waveform data is repeated. The phase shift amount φnis determined such that the phase is continuous at the tail of the waveform data W1and the head of the waveform data W2and at the tail of the waveform data W2and the head of the waveform data W3. In this way, the waveform data W which is repeated three times becomes the waveform data items W1, W2, and W3with a continuous phase.

Specifically, in the first repeated waveform data W, the phase of each of the sample data items D1to DMis shifted (delayed) by φ1. In this example, since φ1=0 is established, the phase is not actually shifted and the waveform data W is W1. In the second repeated waveform data W, the phase of each of the sample data items D1to DMis shifted by φ2and the waveform data W2including sample data items D1(φ2) to DM(φ2) is obtained. In this example, φ2is π/2. In the third repeated waveform data W, the phase of each of the sample data items D1to DMis shifted by φ3and the waveform data W3including sample data items D1(φ3) to DM(φ3) is obtained. In this example, φ3is π.

The phase shift amount φn=(n−1)×θ is calculated from the number of times n the waveform data is repeated and a reference phase difference θ. The reference phase difference θ is the phase difference between the previous waveform data and the next waveform data when a phase change is continuous at the tail (the last sample data) of the previously output waveform data and the head (first sample data) of the next waveform data which is repeatedly output. Specifically, the reference phase difference θ is the phase difference in which the phase of the last sample data DMin the first repeated waveform data W1and the phase of the first sample data D1(φ2) in the second repeated waveform data W2are continuously changed. In this example, θ is π/2. A method of determining the reference phase difference θ will be described in detail below.

As such, in the invention, the reference phase difference θ is determined, the phase shift amount φnis calculated from the number of times n the waveform data is repeated and the reference phase difference θ, and the phase of each of the sample data items D1to DMin the waveform data W is shifted by the phase shift amount φncorresponding to the number of times n the waveform data is repeated. In this way, it is possible to repeatedly generate an arbitrary waveform by continuously connecting the tail of a generated waveform and the head of the next waveform which is repeatedly generated, without changing the frequency of the waveform and generating spurious emissions.

First Embodiment

FIG. 2shows the structure of a signal generating system100according to the invention. The signal generating system100includes a waveform data generating device90that generates the waveform data W and determines the reference phase difference θ and a signal generator10that generates an RF test signal from the waveform data W and the reference phase difference θ. For example, the waveform data W is of an FSK-modulated signal and the signal generator10generates the RF test signal for testing a wireless communication device corresponding to a communication system using an FSK modulation method. The communication system using the FSK modulation method is, for example, Bluetooth (registered trademark).

The waveform data generating device90includes operation means91, waveform data generating means92, reference phase difference determining means93, and waveform data transmitting means94. The waveform data generating device90includes, for example, a personal computer and software, and implements the functions of the means.

The operation means91is operated by the user to set parameters for generating waveform data. For example, the operation means91includes a display (not shown) that displays a setting screen for setting the parameters and an input device, such as a keyboard or a mouse.

The waveform data generating means92generates the digital waveform data W on the basis of the parameters input by the user through the operation means91. The waveform data W is of a baseband signal and includes M sample data items D1to DM. More accurately, the waveform data W is complex IQ data and includes M I-phase data items (each of which is, for example, 16-bit data) and M Q-phase data items (each of which is, for example, 16-bit data). Therefore, there are M sets of IQ data items. However, in this embodiment, one set of IQ data items is described as one sample data item. The waveform data generating means92transmits information related to the waveform data W to the reference phase difference determining means93and transmits the waveform data W to the waveform data transmitting means94.

The reference phase difference determining means93determines the reference phase difference θ on the basis of the information related to the waveform data W received from the waveform data generating means92. The detailed structure of the reference phase difference determining means93will be described below.

The waveform data transmitting means94transmits the waveform data W received from the waveform data generating means92and the reference phase difference θ received from the reference phase difference determining means93to the signal generator10. In order to transmit the waveform data to the signal generator10, the waveform data generating device90and the signal generator10may be connected to each other by USB, Ethernet (registered trademark), or a wireless LAN, or through a storage medium, such as a CD or an SD card.

The signal generator10includes waveform data storage means20, phase shift means30, D/A conversion means40, quadrature modulation means50, and frequency conversion means60. The signal generator10generates the RF test signal for testing a wireless communication device on the basis of the waveform data W.

The waveform data storage means20stores the waveform data W and the reference phase difference θ received from the waveform data generating device90and repeatedly outputs the I-phase data and the Q-phase data of the waveform data W. In addition, the waveform data storage means20outputs the reference phase difference θ corresponding to the output waveform data W and the number of times n the waveform data W is repeatedly output. Specifically, the waveform data storage means20includes a high-capacity storage unit, such as a hard disk drive (HDD), and a random access memory (RAM) which can read or write data at a high speed, and can store combinations of plural kinds of waveform data W and reference phase difference θ in the storage unit. The waveform data storage means20moves the waveform data W designated by the user to the memory unit and outputs the waveform data W from the memory unit. Therefore, the capacity of the waveform data W does not exceed the storage capacity of the memory unit.

The phase shift means30calculates the phase shift amount φnon the basis of the reference phase difference θ and the number of times n the waveform data is repeatedly output which are received from the waveform data storage means20and shifts the phases of the I-phase data and the Q-phase data of the waveform data W by the calculated phase shift amount.FIG. 3shows the structure of the phase shift means30. The phase shift means30includes digital multipliers31ato31d, digital adders32aand32b, and phase shift amount calculating means33. The phase shift amount calculating means33receives the reference phase difference θ and the number of times n the waveform data W is repeatedly output from the waveform data storage means20, calculates the phase shift amount φn=(n−1)×θ, and outputs phase shift data items cos φnand sin φncorresponding to the calculated phase shift amount. The multipliers31ato31dmultiply each IQ data item of each sample data item in the waveform data W by phase shift data, and the adders32aand32badd (or subtract) the outputs of the multipliers and output IQ data items I′ and Q′ obtained by shifting the phase of each sample data item. Specifically, each sample data item of the waveform data W is represented by Aejφ=A (cos φ+j sin φ), the I-phase data is A cos φ, and the Q-phase data is A sin φ. The phase shift data is ejφnand the phase shift data ejφnis multiplied by each sample data item to shift the phase of each sample data item by the phase shift amount φn. This expression is expanded as follows.

The phase shift means30shown inFIG. 3performs calculation corresponding to this expression and outputs the phase-shifted IQ data items I′ and Q′. The phase shift means30is implemented by an arithmetic process of an arithmetic circuit (FPGA or DSP) or a CPU.

The D/A conversion means40includes two D/A converters41and42and sequentially performs D/A conversion on the IQ data of each of the phase-shifted sample data items.

The quadrature modulation means50is a quadrature modulator including two mixers51and52, a local oscillator53, a 90-degree phase shifter54, and an adder55. The quadrature modulation means50mixes the D/A-converted I-phase signal with a local oscillation signal from the local oscillator53and mixes the D/A-converted Q-phase signal with a signal obtained by shifting the phase of the local oscillation signal from the local oscillator53by 90 degrees (π/2). Then, the quadrature modulation means50adds the mixed signals and outputs the addition result.

The frequency conversion means60includes a local oscillator61and a mixer62and performs frequency conversion on the signal from the quadrature modulation means50using the local oscillation signal from the local oscillator61. The frequency-converted signal is shaped and amplified by a filter (not shown) and an amplifier (not shown) and is then output as the RF test signal.

The signal generator may have the same structure as the signal generator11shown inFIG. 4. InFIG. 4, the frequency conversion means70also has the functions of the quadrature modulation means50and the frequency conversion means60shown inFIG. 2, and the frequency of the local oscillation signal from the local oscillator73is used as the frequency of a carrier wave, which makes it possible to perform quadrature modulation and frequency conversion using the same means.

Next, the operation of the signal generating system100according to this embodiment will be described with reference to the flowchart shown inFIG. 5. First, the operation of the waveform data generating device90will be described. The user operates the operation means91to set the parameters for generating the waveform data W (S1). The parameters include, for example, the content of data before modulation and a data length. The waveform data generating means92generates the waveform data W on the basis of the set parameters (S2). The reference phase difference determining means93determines the reference phase difference θ using the information of the waveform data W (S3). The waveform data transmitting means94transmits the generated waveform data W and the determined reference phase difference θ to the signal generator10(S4).

Next, the operation of the signal generator10will be described. The waveform data storage means20stores the waveform data W and the reference phase difference θ received from the waveform data generating device90(S5). The user operates the operation unit (not shown) to set parameters for outputting the RF test signal (S6). The parameters include, for example, the selection of plural kinds of waveform data W stored in the waveform data storage means20, the carrier frequency of the RF test signal, an output level, and an output relay time (or the number of times the waveform data is repeatedly output and relayed). The phase shift amount calculating means33receives the reference phase difference θ from the waveform data storage means20and calculates the phase shift amount φnfor the number n (n=1, 2, 3, . . . ) of times the waveform data W is output (S7). The phase shift amount φnmay be calculated for all of the predetermined numbers n using the output relay time or the number of times the waveform data is repeatedly output and relayed which is set as the parameter. Alternatively, whenever the waveform data W is repeatedly output, the phase shift amount φnmay be calculated for the number of times n the waveform data W is repeatedly output.

The number of times n the waveform data W is repeatedly output is set to 1 (S8) and the waveform data W from the waveform data storage means20is sequentially output from the first sample data D1to the last sample data DM(S9). The multipliers31and32multiply each of the sample data items D1to DMof the output waveform data W by phase shift data and the phase of each of the sample data items D1to DMis shifted by the phase shift amount φn(S10). The phase shift amount φnvaries depending on the number of times n the waveform data W is repeatedly output.

The D/A converters41and42perform D/A conversion on each of the phase-shifted sample data items (S11), the quadrature modulation means50performs quadrature modulation on each of the phase-shifted sample data items, and the frequency conversion means60performs frequency conversion on each of the phase-shifted sample data items to generate an RF signal and outputs the generated RF signal as the RF test signal (S12). Then, the number of times n the waveform data W is repeatedly output increases (S13) and the next repeated waveform data W is output from the waveform data storage means20. In this way, the operation of Steps S9to S13is repeated until the number of times n the waveform data W is repeatedly output reaches a predetermined value.

Next, the method of determining the reference phase difference θ will be described in detail. First, the concept of the method will be described with reference toFIG. 6and four examples will be described with reference toFIGS. 7 to 10corresponding to the examples.

FIG. 6is a diagram illustrating the concept of the method of determining the reference phase difference θ. Specifically,FIG. 6(A)schematically shows the sample data items arranged along the time axis andFIG. 6(B)shows the sample data items on an IQ plane. As shown inFIG. 6(A), in order to make the phase of the first repeated waveform data W continuous with the phase of the second repeated waveform data W, when attention is focused on the first sample data D1of the second repeated waveform data, the phase of the second repeated waveform data may be shifted such that the phase of the sample data item D1is the same as the phase of a sample data item DM+1of the first repeated waveform data. As shown inFIG. 6(B), the phase difference between the sample data items D1and DM+1is θ and becomes the reference phase difference θ. As another representation, the reference phase difference θ is the difference between the phase of the first sample data item D1of the waveform data W and the phase of the sample data item DM+1which is subsequent to the last sample data item DM.

However, the sample data item DM+1does not originally exist. Therefore, in order to determine the reference phase difference θ, a method is performed which obtains the phase of the sample data item DM+1and determines the reference phase difference θ on the basis of the obtained phase. In the following examples, the method will be described in detail. The first and second examples relate to a method of adding a predetermined phase (ΨAor ΨB) to the phase of the last sample data item DMto obtain the phase of the sample data item DM+1. The third example relates to a method of analyzing the waveform data W to estimate the phase of the sample data item DM+1. The fourth example relates to a method of directly obtaining the phase of the sample data item DM+1.

First Example

FIG. 7(A)is a block diagram illustrating the structure of reference phase difference determining means93(or reference phase difference determining means23which will be described below) according to the first example. The reference phase difference determining means93includes phase estimating means82aand reference phase difference calculating means83.FIG. 7(B)is a flowchart illustrating a method of determining the reference phase difference θ in correspondence withFIG. 7(A).

First, the waveform data generating means92generates the waveform data W including M sample data items D1to DM(S21). The phase estimating means82aacquires information of three phases, that is, the phase Ψ1of the first sample data item D1, the phase ΨM−1of an (M−1)-th sample data item DM−1, and the phase ΨMof an M-th sample data item DMin the waveform data W from the waveform data generating means92(S22). The phase estimating means82acalculates ΨM+1=ΨM+ΨA=ΨM+(ΨM−ΨM−1) (where ΨAis the difference between the phase ΨMof the M-th sample data item DMand the phase ΨM−1of the (M−1)-th sample data item DM−1) to estimate the phase ΨM+1of an (M+1)-th sample data item DM+1(S23). The reference phase difference calculating means83calculates θ=ΨM+1−Ψ1from the phase Ψ1of the sample data item D1and the estimated phase ΨM+1of the sample data item DM+1, thereby calculating the reference phase difference θ (S24). In this way, the reference phase difference θ is determined.

According to this example, the reference phase difference θ is determined by simple calculation from the information of the phases of three sample data items in the generated waveform data W. Therefore, it is possible to determine the reference phase difference θ with ease. In addition, it is possible to determine the reference phase difference θ later even for the waveform data which is generated by the waveform data generating device according to the related art and in which the reference phase difference θ is not determined. The signal generator according to the invention can output the waveform data such that the phases of the head and tail of the waveform are continuous.

Second Example

FIG. 8(A)is a block diagram illustrating the structure of reference phase difference determining means93(or reference phase difference determining means23which will be described below) according to a second example. The reference phase difference determining means93includes average phase difference calculating means81, phase estimating means82b, and reference phase difference calculating means83.FIG. 8(B)is a flowchart illustrating a method of determining the reference phase difference θ in correspondence withFIG. 8(A).

First, the waveform data generating means92generates waveform data W including M sample data items D1to DM(S31). The average phase difference calculating means81receives the phase information of the sample data items D1to DMfrom the waveform data generating means92and calculates an average phase difference ΨBper sample data item, which is the average value of the phase difference between a given sample data item Dmand the next sample data item Dm+1(S32). The phase estimating means82bacquires the information of the phase Ψ1of the first sample data item D1and the phase ΨMof an M-th sample data item DMin the waveform data W (S33). Then, the phase estimating means82bcalculates ΨM+1=Ψm+ΨBto estimate the phase ΨM+1of an (M+1)-th sample data item DM+1(S34). The reference phase difference calculating means83calculates θ=ΨM+1−Ψ1from the phase Ψ1of the sample data item D1and the estimated phase ΨM+1of the sample data item DM+1, thereby calculating the reference phase difference θ (S35). In this way, the reference phase difference θ is determined.

According to this example, the reference phase difference θ is determined from the phase information of the sample data items in the generated waveform data W. Therefore, it is possible to determine the reference phase difference θ later even for the waveform data which is generated by the waveform data generating device according to the related art and in which the reference phase difference θ is not determined. The signal generator according to the invention can output the waveform data such that the phases of the head and tail of the waveform are continuous.

Third Example

FIG. 9(A)is a block diagram illustrating the structure of reference phase difference determining means93(or reference phase difference determining means23which will be described below) according to a third example. The reference phase difference determining means93includes phase estimating means82c, and reference phase difference calculating means83.FIG. 9(B)is a flowchart illustrating a method of determining the reference phase difference θ in correspondence withFIG. 9(A).

First, the waveform data generating means92generates waveform data W including M sample data items D1to DM(S41). The phase estimating means82creceives the waveform data W from the waveform data generating means92, analyzes the waveform data W, and estimates the phase ΨM+1of an (M+1)-th sample data item DM+1(S42). The reference phase difference calculating means83calculates θ=ΨM+1−Ψ1from the phase Ψ1of the sample data item D1and the estimated phase ΨM+1of the sample data item DM+1, thereby calculating the reference phase difference θ (S43). In this way, the reference phase difference θ is determined.

Examples of a method of analyzing the waveform data W in the phase estimating means82cwill be described below.

(a) The frequency of the vicinity of the first data item and the frequency of the vicinity of the last data item in the waveform data W are analyzed. As a result, when the frequencies are substantially equal to each other, the phase is changed at a constant rate during the period from the vicinity of the last data item to the vicinity of the first data item in the next repeated waveform data W for which the frequency is hardly changed. Therefore, it is possible to estimate the phase ΨM+1with ease.

(b) A variation in the frequency of the waveform data W over time is analyzed. As a result, for example, when there is a signal which is alternately changed at frequencies of 1 kHz and 2 kHz over time, the signal may be estimated to an FSK-modulated signal. Since the phase of the FSK-modulated signal is changed at a constant rate during the period for which the frequency of the FSK-modulated signal is not changed, it is possible to estimate the phase ΨM+1with ease.

(c) A variation in the phase of the waveform data W over time is analyzed. As a result, for example, since the phase of a signal with a phase which is proportional to time (linear function with respect to time) is changed at a constant rate, it is possible to estimate the phase ΨM+1with ease. In addition, the method may be combined with a method of performing an FFT process on the waveform data W to analyze a frequency. In this case, it is possible to accurately guess the waveform data W and estimate the phase ΨM+1.

(d) A variation in the amplitude of the waveform data W over time is analyzed. An approximate expression is calculated according to the analysis result and the phase ΨM+1is calculated from the approximate expression.

The phase estimating means82bestimates the phase ΨM+1using any one of the methods (a) to (d) or combinations thereof.

According to this example, the generated waveform data W is analyzed to determine the reference phase difference θ. Therefore, it is possible to determine the reference phase difference θ later even for the waveform data which is generated by the waveform data generating device according to the related art and in which the reference phase difference θ is not determined. The signal generator according to the invention can output the waveform data such that the phases of the head and tail of the waveform are continuous.

Fourth Example

FIG. 10(A)is a block diagram illustrating the structure of reference phase difference determining means93according to a fourth example. The reference phase difference determining means93includes reference phase difference calculating means83.FIG. 10(B)is a flowchart illustrating a method of determining the reference phase difference θ in correspondence with FIG.10(A).

First, the waveform data generating means92generates M sample data items D1to DMand at least the phase information of a sample data item DM+1(the waveform data generating means92may generate all of M+1 sample data items D1to DM+1) (S51) and generates waveform data W including the M sample data items D1to DM(S52). The reference phase difference calculating means83acquires the information of the phase Ψ1of the sample data item D1and the phase ΨM+1of the sample data item DM+1from the waveform data generating means92(S53) and calculates θ=ΨM+1−Ψ1, thereby calculating the reference phase difference θ (S54). In this way, the reference phase difference θ is determined.

According to this example, when the waveform data W including the M sample data items is generated, the phase information of the (M+1)-th sample data item DM+1which is not originally generated is generated and acquired and the reference phase difference θ is determined from the phase information. Since the phase ΨM+1of the (M+1)-th sample data item DM+1is not calculated by estimation, but is actually generated and acquired, it is possible to accurately determine the reference phase difference θ. The signal generator according to the invention can output the waveform data such that the phases of the head and tail of the waveform are continuous.

Second Embodiment

FIG. 11shows the structure of a signal generating system101according to a second embodiment of the invention. The signal generating system101includes a waveform data generating device95that generates waveform data W and a signal generator12that generates an RF test signal on the basis of the waveform data W. Next, the difference between the second embodiment and the first embodiment will be mainly described and a description of components having the same structure as those in the first embodiment will be appropriately omitted.

The waveform data generating device95differs from the waveform data generating device90according to the first embodiment in that the reference phase difference determining means93is not provided. Therefore, the waveform data generating device95does not generate a reference phase difference θ and the information of the reference phase difference θ is not transmitted from the waveform data generating device95to the signal generator12.

The signal generator12differs from the signal generator10according to the first embodiment in that it includes reference phase difference determining means23. The reference phase difference determining means23has the structure of any one of the first example, the second example, and the third example of the first embodiment. The reference phase difference determining means23is implemented by an arithmetic process of an arithmetic circuit (FPGA or DSP) or a CPU. The signal generator12may include frequency conversion means70having the functions of quadrature modulation means50and frequency conversion means60, similarly to the signal generator11shown inFIG. 4.

FIG. 12is a flowchart illustrating the operation of the signal generating system101according to this embodiment. The second embodiment differs from the first embodiment in that there is no step of calculating the reference phase difference θ in the operation of the waveform data generating device from Step S61to Step S63. In addition, the second embodiment differs from the first embodiment in that there is a step (S66) of calculating the reference phase difference θ in the operation of the signal generator from Step S64to Step S73. As described above, the step in any one of the first example, the second example, and the third example of the first embodiment may be used as the step of calculating the reference phase difference θ. The reference phase difference θ may be calculated in any step after the waveform data W is stored and before the phase shift amount φnis calculated.

INDUSTRIAL APPLICABILITY

As such, the signal generator, the signal generating system, and the signal generating method according to the invention can repeatedly generate an arbitrary waveform such that the phases of the head and tail of the generated waveform are continuous. Therefore, they are useful for accurately testing a wireless communication device.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

10,11,12: SIGNAL GENERATOR20: WAVEFORM DATA STORAGE MEANS23: REFERENCE PHASE DIFFERENCE DETERMINING MEANS30: PHASE SHIFT MEANS31,32: MULTIPLIER33: PHASE SHIFT AMOUNT CALCULATING MEANS40: D/A CONVERSION MEANS41,42: D/A CONVERTER50: QUADRATURE MODULATION MEANS51,52: MIXER53: LOCAL OSCILLATOR54: 90-DEGREE PHASE SHIFTER55: ADDER60: FREQUENCY CONVERSION MEANS61: LOCAL OSCILLATOR62: MIXER70: FREQUENCY CONVERSION MEANS73: LOCAL OSCILLATOR81: AVERAGE PHASE DIFFERENCE CALCULATING MEANS82: PHASE ESTIMATING MEANS83: REFERENCE PHASE DIFFERENCE CALCULATING MEANS90: WAVEFORM DATA GENERATING DEVICE91: OPERATION MEANS92: WAVEFORM DATA GENERATING MEANS93: REFERENCE PHASE DIFFERENCE DETERMINING MEANS94: WAVEFORM DATA TRANSMITTING MEANS95: WAVEFORM DATA GENERATING DEVICE100,101: SIGNAL GENERATING SYSTEM