JP2000236268A - Software radio set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain software radio set having a transmission and a reception part which can communicate, even with a communication systems having different frequency bands. SOLUTION: For frequency conversion of a transmission part, mixers 5, 8, and 11 are provided in three stages and a high-pass filter 10 and a low-pass filter 7 having fixed cutoff frequencies are provided between the stages to constitute a band-limiting circuit. The mixers 5, 8, and 11 filter IF signal bands after the frequency conversion by both the filters so that the frequencies at the ends of the IF signal band match the cutoff frequencies are supplied from local signal generators 6, 9, and 12. The reception part is also equipped with a high-pass filter 18 and a low-pass filter 21 having fixed cutoff frequencies as well. Each of the mixers 5, 8, and 11 are supplied with frequencies to be converted into IF signals from the local signal generators 6, 19 and 12 as well as the transmission part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a software defined radio capable of communicating in a wide frequency band with a simple configuration.

[0002]

2. Description of the Related Art In recent years, a DSP (Digital Signal Processing) has replaced a signal processing function previously realized by an analog circuit.
A radio called a software radio is attracting attention, which uses a technology of processing with software using a device capable of digital signal processing such as (or). This radio can convert the analog signal into a digital signal and then perform the signal processing by software, so that the signal processing function such as modulation and demodulation of the radio can be flexibly changed.
This has the feature that various communication systems can be supported. FIG. 3A is a schematic configuration diagram showing an example of a conventional software defined radio in a mobile phone or the like, in which a part of the function of the radio is implemented by a DSP. As shown in the figure, the wireless device includes a DSP 31 for performing modulation / demodulation or input / output data processing, a D / A converter 32 for converting a digital modulation signal output from the DSP 31 into an analog signal, and a transmitter / receiver. Unit 33, an antenna 34 for transmitting and receiving high-frequency radio waves, a receiving unit 35, and the receiving unit 35
A / that converts the analog signal output from
It comprises a D converter 36, a memory 37 storing a communication protocol corresponding to the communication system, and a CPU 38 for controlling the operation of the radio device according to the communication protocol.

FIG. 3B is a schematic diagram of the configuration of the transmitting unit 33, and FIG. 3C is a schematic diagram of the configuration of the receiving unit 35.
As shown in FIG. 3B, the transmitting unit 33 includes a band-pass filter 3 that limits the band of the analog-converted signal.
31, a transmission local signal generator 333 that generates a local signal, a mixer 332 that frequency-converts an output signal of the band-pass filter 331 into a high-frequency signal by a signal from the transmission local signal generator 333, and performs power amplification of the high-frequency signal. As shown in FIG. 3C, the receiver 35 includes a transmission RF amplifier 334 that amplifies a received radio frequency signal, and a reception local signal generator 352 that generates a local signal. ,
It comprises a mixer 353 for converting the output signal of the reception RF amplifier 351 into an intermediate frequency signal by a signal from the reception local signal generator 352 and a bandpass filter 354 for limiting the band of the intermediate frequency signal.

When communication is performed using the wireless device having the above-described configuration, a communication protocol corresponding to the communication system stored in the memory 37 is downloaded to the CPU 38, and the CPU 25 controls the wireless device according to the downloaded communication protocol. Then, communication can be performed. Hereinafter, the operation will be described. First, when a user's voice or data is input, the DSP 31 performs data conversion and modulation. The modulated output signal of the DSP 31 is converted into an analog signal by the D / A converter 32 and input to the band-pass filter 331 of the transmitting unit 33. The band-limited signal in the band-pass filter 331 is input to a mixer 332 and mixed with a local signal from a transmission local signal generator 333.
The transmission RF amplifier 33 converts the signal to a predetermined transmission high-frequency signal.
4 is input. Further, the transmission high-frequency signal is power-amplified in the transmission RF amplifier 334 and radiated from the antenna 34.

On the other hand, the high-frequency signal received by the antenna 34 is amplified by the reception RF amplifier 351 of the reception unit 35 and input to the mixer 353. The reception high-frequency signal is converted into a predetermined intermediate frequency signal by mixing with the local signal from the reception local signal generator 352 in the mixer 353, and is input to the band-pass filter 354. The intermediate frequency signal band-limited by the band pass filter 354 is input to an A / D converter 36, which converts the intermediate frequency signal into a digital signal,
1 is input. The digitized intermediate frequency signal is subjected to demodulation and data processing in the DSP 21 to obtain an output signal.

[0006]

However, the frequency band in which communication can be performed in the software defined radio having the above configuration is a specific frequency band which can be supported by the transmitting unit and the receiving unit shown in FIGS. 1B and 1C. Only obi. Therefore, when a signal processing and modulation / demodulation processing corresponding to various communication protocols can be realized only by changing software by the DSP, when a communication system of another frequency band is used, the frequency band of the communication system is used. There is a problem that it is necessary to prepare, as hardware, a transmission / reception unit including a transmission unit and a reception unit that can cope with the problem. The present invention has been made to solve the above-described problem, and has as its object to provide a software defined radio capable of performing communication in a wide frequency band with a simple configuration.

[0007]

According to a first aspect of the present invention, there is provided a digital signal processing means for modulating an input signal by software, and a digital signal processing means for converting a modulated digital signal into an analog signal. / Analog conversion means, filtering means for removing out-of-band unnecessary waves in a signal, transmission frequency conversion means for converting a modulation signal frequency into a transmission high-frequency signal, and control means for controlling the operation thereof. In the software defined radio provided, a filtering unit of the transmitting unit removes an unnecessary wave in a frequency band higher than a frequency band of a desired modulation output in an output signal of the digital / analog conversion unit, a low-pass filtering unit, High-pass filtering means for removing unnecessary low-frequency waves below the frequency band of the desired modulation output; The transmission frequency conversion means comprises first transmission frequency conversion means provided before the low-pass filtering means, and second transmission frequency conversion means provided before the high-pass filtering means. And third transmission frequency conversion means for frequency-converting the output frequency of the high-pass filtering means into a predetermined transmission high-frequency signal, and the modulation output frequency output from the first frequency conversion means is low. The modulation output frequency output from the second frequency conversion means is such that the cut-off frequency of the high-pass filtering means matches the high-frequency end of the frequency band of the modulation output. The frequency set by the control means is such that the lower end of the frequency band of the modulation output coincides with the lower end. According to the second aspect of the present invention, a receiving frequency converting means for converting a received high frequency signal into an intermediate frequency, a filtering means for removing an out-of-band unnecessary wave of the intermediate frequency signal, and an analog / digital converter for converting the intermediate frequency signal into a digital signal. In a software defined radio comprising a receiving section comprising digital conversion means and the digital signal processing means for demodulating a digitally converted signal, and a control means for controlling the operation thereof, the filtering means of the receiving section comprises: High-pass filtering means for removing low-frequency unnecessary waves in the high-frequency signal below the frequency band of the desired communication system, and low-frequency filtering means for removing high-frequency unnecessary waves in the high-frequency signal and above the frequency band of the desired communication system Wherein the reception frequency conversion means is provided before the high-pass filtering means. (1) receiving frequency conversion means, second reception frequency conversion means provided before the low-pass filtering means, and an intermediate unit capable of sampling the output frequency of the low-pass filtering means by the analog / digital conversion means. And a third receiving frequency converting means for converting the frequency of the received signal output from the first receiving frequency converting means into a cutoff frequency of the high-pass filtering means and a frequency band of a desired communication system. The frequency of the reception signal output from the second reception frequency conversion means so that the low-frequency end of the received signal coincides with the cutoff frequency of the second low-pass filtering means and the high-frequency end of the frequency band of the desired communication system. Is a frequency set by the control means so that the frequency of the control signal coincides with the frequency of the control signal.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a schematic configuration diagram showing one embodiment of a software defined radio according to the present invention. As shown in FIG. 1, the software radio includes a CPU 1 for controlling the entire device, a keyboard 2 for inputting a communication system designated by a user to the CPU 1, and a DSP 3 for performing modulation / demodulation or input / output data processing.
A D / A converter 4 for converting a digital input into an analog signal; a first mixer 5 for converting a frequency of an output of the D / A converter 4 into a transmission first IF signal as a transmission system; A first local signal generator 6 for outputting a local signal, a low-pass filter 7 for removing unnecessary harmonics in an output signal of the first mixer 5, and a conversion of a frequency of an output of the low-pass filter 7 to a transmission second IF signal. Mixer 8, a local signal generator 9 for outputting a local signal to the second mixer 8, and a high-pass filter 1 for removing unnecessary low-frequency waves in the output signal of the second mixer 8.
0, a third mixer 11 that converts an output signal of the high-pass filter 10 into a predetermined transmission high-frequency signal, a third local signal generator 12 that outputs a local signal to the third mixer 11, and converts the high-frequency signal to a predetermined power. Transmit RF to amplify
It has an amplifier 13 and a broadband antenna 14 for transmitting and receiving high-frequency radio waves.

The software defined radio includes a reception RF amplifier 15 for amplifying a reception radio wave as a reception system, a first mixer 16 for frequency-converting an output signal of the reception RF amplifier 15 to a reception first IF signal, and a first mixer 16 A first local signal generator 17 for outputting a local signal to the second mixer 16; a high-pass filter 18 for removing unnecessary low-frequency waves in the output signal of the first mixer 16; and an output frequency of the high-pass filter 18 as a received second IF signal. Second mixer 1 for conversion
9. A second output of a local signal to the second mixer 19
A local signal generator 20, a low-pass filter 21 for removing unnecessary high-frequency waves in an output signal of the second mixer 20,
A third IF receiving the output frequency of the low-pass filter 21
A third local signal generator 23 for outputting a local signal to the third mixer 22;
An A / D converter 24 for converting the output signal of the second to a digital signal, a first memory 25 storing communication protocols corresponding to various communication systems, and the first memory by the CPU 1.
And a second memory 26 for storing a communication protocol selected from among the memories 25.

The first, second, and third local signal generators 6, 9, and 12 of the receiving system and the first, second, and third local signal generators 17, 20, and 23 of the transmitting system are each a CPU.
1 is an oscillation frequency variable signal generator capable of outputting an output signal of a preset frequency to a mixer under the control of 1. The transmitting low-pass filter 7 and high-pass filter 10 have fixed cut-off frequencies ftcL and ftcH, respectively, and the receiving low-pass filter 21 and high-pass filter 18 have fixed cut-off frequencies frcL and frcH, respectively. Filter.

When performing communication with the software defined radio having the above configuration, the user inputs a communication method to be used to the CPU 1 through the keyboard 2. The CPU 1 selects a communication protocol of the system from the first memory 25 based on a key input, and writes the communication protocol into a DSP start-up program in the second memory 26. Next, based on the control of the CPU 1, the communication protocol stored in the second memory 26 is downloaded to the DSP 3. The DSP 3 performs data processing according to this protocol. The transmission voice or data signal of the user is converted into a digital modulation wave in accordance with the communication system in the DSP 3 and output to the D / A converter 4. D / A
The signal input to the converter 4 is converted by the D / A converter 4 into an analog modulated wave signal having a center frequency ft0 and a bandwidth Wt, and is output to the mixer 5. The output signal of the D / A converter 4 includes, in addition to the modulated wave signal having the center frequency ft0 and the bandwidth Wt, an image signal of a modulated wave in a high band of the modulated wave and a noise signal in a low band of the modulated wave. Have been.

The signal input to the mixer 5 is converted to a transmission first IF signal having a center frequency of ft0 + ft1, which is a local signal having a frequency ft1 output from a first local signal generator 6, and is output to a low-pass filter 7. Fig. 2 (a)
FIG. 3 is a diagram showing a relationship between the transmission first IF signal and filter characteristics of the low-pass filter 7. As shown in the figure,
The oscillation frequency ft1 is a frequency having a relationship of ft0 + ft1 + Wt / 2 = ftcL, ie, ft1 = ftcL− (ft0 + Wt / 2) (1), with the cutoff frequency ftcL of the low-pass filter 7. , And is output from the first local signal generator 6 based on a control signal from the CPU 1. The high-frequency component of the transmission first IF signal is removed by the low-pass filter 7 and output to the second mixer 8. The signal input to the second mixer 8 is a local signal having a frequency ft2 output from the second local signal generator 9 and is converted into a transmission second IF signal having a center frequency of ft0 + ft1 + ft2, and is output to the high-pass filter 10. . FIG. 2B is a diagram illustrating a relationship between the transmission second IF signal and the filter characteristics of the high-pass filter 10. As shown in the figure, the oscillation frequency ft2 is between the cutoff frequency ftcH of the high-pass filter 10 and ft0 + ft1 + ft2 + Wt / 2 = ftcH, that is, ft2 = ftcH− (ft0 + ft1 + Wt / 2) (2) Is output from the second local signal generator 9 based on a control signal from the CPU 1. From the transmission second IF signal, a low-pass noise component is removed by a high-pass filter 7, and a third modulated signal is obtained as a desired modulated wave signal.
Output to the mixer 11. The modulated wave signal input to the third mixer is converted into a predetermined transmission high-frequency signal by a local signal of frequency ft3 output from the third local signal generator 12 based on a control signal from the CPU 1. The transmission high-frequency signal is amplified to a predetermined power by the transmission RF amplifier 13 and emitted from the broadband antenna 14.

On the other hand, a high-frequency signal received by the broadband antenna 14 is input to a reception RF amplifier 15. The high-frequency reception signal includes a signal of a desired communication system having the center frequency fr0 and the bandwidth Wr, as well as a signal and a noise component of another communication system. The reception signal is amplified by the reception RF amplifier 15 and output to the first mixer 16.
The received signal input to the first mixer 16 is converted to a received first IF signal having a center frequency of fr0 + fr1 with a local signal of a frequency fr1 output from a first local signal generator 17 and output to a high-pass filter 18. FIG. 2 (c)
5 is a diagram illustrating a relationship between a received first IF signal and filter characteristics of the high-pass filter 18. FIG. As shown in the figure, the oscillation frequency fr1 is between the cutoff frequency frcH of the high-pass filter 18 and fr0 + fr1 + Wr / 2 = frcH, that is, fr1 = frcH- (fr0 + Wr / 2) (3) The first local signal generator 17 outputs a frequency having a relationship based on a control signal from the CPU 1. From the received first IF signal, unnecessary waves such as signals of other low-band communication systems are removed by a high-pass filter 18,
It is input to the second mixer 19. The signal input to the second mixer 19 has the frequency from the second local signal generator 20.
The local signal of fr2 is converted into a received second IF signal having a center frequency of fr0 + fr1 + fr2 and input to the low-pass filter 21. FIG. 2D is a diagram illustrating the relationship between the received second IF signal input from the second mixer 19 and the filter characteristics of the low-pass filter 21. As shown in the figure, the oscillation frequency fr2 is between the cutoff frequency frcL of the low-pass filter 21 and fr0 + fr1 + fr2 + Wr / 2 = frcL, that is, fr2 = frcL- (fr0 + fr1 + Wr / 2) (4) ) Is output from the second local signal generator 23 based on the control signal from the CPU 1. The received second IF signal is subjected to low-pass filter 21 to remove signals of other high-band communication systems, noise components, and the like, and is output to the third mixer 22 as a desired demodulated wave signal. In the mixer 22, a local signal having a frequency fr3 output from the third local signal generator 23 based on a control signal from the CPU 1, and a frequency that can be sampled by the A / D converter 24 is a received third IF signal of fr0 + fr1 + fr2 + fr3. And output to the A / D converter 24. The received third IF signal converted to a digital signal by the A / D converter 24 is input to the DSP 3, subjected to demodulation and data processing corresponding to the communication system, and output as voice or data.

When the user uses another communication system, he or she inputs a desired system to the CPU 1 through the keyboard 2. With this input, the communication protocol of the desired system is written from the first memory to the second memory and downloaded to the DSP3. The DSP 3 modulates and demodulates the input signal and performs data processing according to the downloaded protocol. At the same time, the CPU 1
Second local signal generators 6 and 9 and first and second reception systems
For the local signal generators 17 and 20, equation (1)
Control signals are output so as to output preset oscillation frequencies having the relations of (2), (3) and (4). Further, the third local signal generator 12 of the reception system outputs a predetermined oscillation frequency at which the output of the third mixer 11 becomes a predetermined transmission frequency to the third local signal generator 12 of the transmission system. 23, the third mixer 22
Control signals are output so that the output of the A / D converter 24 outputs a preset frequency that can be sampled by the A / D converter 24. Thereafter, by the above-described operation, the software defined radio can communicate with another desired communication system.

[0015]

As described above, the software defined radio according to the present invention makes the fixed cutoff frequency of the high-pass filter coincide with the lower end of the desired signal band, and fixes the fixed cutoff of the low-pass filter. Since the frequency and the high-frequency end of the desired signal band are matched to remove unnecessary waves outside the desired signal band, the user can use a single communication system in different frequency bands. There is a remarkable effect that communication can be performed by the software defined radio.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a software defined radio according to the present invention.

FIG. 2A is a diagram illustrating a relationship between a transmission first IF signal and a filter characteristic of a low-pass filter of a transmission system, and FIG.
FIG. 3C is a diagram showing the relationship between the transmission second IF signal and the filter characteristic of the transmission high-pass filter, and FIG.
FIG. 4D is a diagram illustrating a relationship between a signal and a filter characteristic of a high-pass filter of a reception system.

3A is a schematic configuration diagram illustrating an example of a conventional software defined radio, FIG. 3B is a schematic configuration diagram of a transmitting unit in FIG. 3A, and FIG. 3C is a schematic diagram of a receiving unit in FIG. 3A; Configuration overview

[Explanation of symbols]

1. CPU, 2. Keyboard, 3
··· DSP, 4 ··· D / A converter, 5, 16 ··· First mixer, 17 ··· First local signal generator, 7, 2
1. low pass filter, 8, 19 second mixer,
9, 20,... The second local signal generator, 10,
18. high-pass filter, 11, 22, third
Mixer, 12, 23 ··· Third local signal generator, 13
..Transmission RF amplifiers, 14Broadband antennas, 15
..Reception RF amplifier, 24.A / D converter, 25
··· First memory, 26 ··· Second memory (according to the present invention) 31 ··· DSP, 32 ··· D / A converter, 3
3 ··· transmitting unit, 34 · · antenna, 35 · · · receiving unit, 36 · · · A / D converter, 37 · · · memory,
38, CPU, 331, 354, bandpass filter, 353, mixer, 333, transmission local signal generator, 334, transmission RF amplifier, 351
..Reception RF amplifier, 352..Reception local signal generator

Claims (2)

[Claims] 1. Digital signal processing means for modulating an input signal by software, digital / analog conversion means for converting a modulated digital signal into an analog signal, and filtering means for removing unnecessary out-of-band waves in the signal. A software radio comprising: a transmission unit comprising: a transmission frequency conversion unit for converting a modulation signal frequency into a transmission high-frequency signal; and a control unit for controlling the operation of the transmission unit. Low-pass filtering means for removing unnecessary high-frequency waves above the frequency band of the desired modulation output in the output signal of the conversion means; and high-frequency filtering means for removing unnecessary low-frequency waves below the frequency band of the desired modulation output. And the transmission frequency conversion means comprises the low-pass filtering means. A first transmission frequency conversion means provided at a preceding stage, a second transmission frequency conversion means provided at a stage preceding the high-pass filtering means, and an output frequency of the high-pass filtering means as a predetermined transmission high-frequency signal And a third transmission frequency converting means for converting the frequency of the low-pass filtering means into a cutoff frequency of the low-pass filtering means and a high-frequency end of a frequency band of the modulation output. So that
The modulation output frequency output from the second frequency conversion means is a frequency set by the control means such that the cutoff frequency of the high-pass filtering means matches the low-frequency end of the frequency band of the modulation output. A software defined radio, characterized by: 2. A receiving frequency converting means for converting a received high frequency signal into an intermediate frequency, a filtering means for removing an out-of-band unnecessary wave of the intermediate frequency signal, and an analog / digital converting means for converting the intermediate frequency signal into a digital signal. And a receiving unit comprising: a digital signal processing unit for demodulating a digitally converted signal; and a control unit for controlling the operation of the receiving unit. High-pass filtering means for removing unnecessary low-frequency waves below the frequency band of the desired communication system, and low-frequency filtering means for removing unnecessary high-frequency waves above the frequency band of the desired communication system. A first receiving frequency provided before the high-pass filtering means; Converting means, a second receiving frequency converting means provided before the low-pass filtering means, and converting an output frequency of the low-pass filtering means into an intermediate frequency which can be sampled by the analog / digital converting means. A third reception frequency conversion unit, wherein a frequency of the reception signal output from the first reception frequency conversion unit is a cutoff frequency of the high-pass filtering unit and a low-frequency end of a frequency band of a desired communication system. The frequency of the reception signal output from the second reception frequency conversion means is such that the cutoff frequency of the second low-pass filtering means matches the high frequency end of the frequency band of the desired communication system. A software defined radio, wherein the frequency is set by the control means as described above.