JP2004336280A - Digital modulation transmitters - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means of a simplified circuit structure which can be applied to a digital modulation system in a plurality of communication systems without necessity of high precision circuit elements. <P>SOLUTION: The desired digital modulated signal can be obtained through phase modulation in an oscillator 1 by generating a plurality of carrier signals in different phases from the frequency modulated carrier signal through control of oscillation frequency based on the frequency controlled signal 11 and then selecting the carrier signal of a phase using a switch 2 based on the phase controlled signal 12 from these carrier signals. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a digital modulation type transmitter, and more particularly to a digital modulation transmitter used in a wireless or wired communication system and transmitting a digital modulation signal corresponding to a plurality of communication systems by one transmitter.
[0002]
[Prior art]
In a wireless communication system or a wired communication system, various communication systems are used depending on a service intended by the system and an amount of information communicated by the system. For example, there are a number of communication systems used in wireless communication systems.
PDC system that provides mobile phone service using 800 MHz band and 1.5 GHz band,
IMT-2000 system, which is a third generation mobile phone using the 2 GHz band,
A wireless system using the 280 MHz band to provide an information distribution service.
IEEE802.11a and IEEE802.11b, which are communication standards for configuring a wireless LAN,
Bluetooth, a communication standard for short-range wireless communication,
and so on. In addition to these, various communication systems are used depending on purposes and applications.
[0003]
In the conventional technology, one transceiver can support only one communication scheme, and when it is desired to use a plurality of communication schemes, it is necessary to prepare a plurality of transceivers for each communication scheme.
Conventionally, in order to solve such a problem, a method of configuring a transceiver that can support a plurality of communication systems has been proposed. Various methods have been proposed for the method of configuring the transmitter and the method of configuring the receiver, some of which have been put to practical use.However, in the following, particularly for the method of configuring the transmitter according to the present invention, a plurality of communication methods will be described. A description will be given of a conventional example of a technology that can be used.
[0004]
[Prior art 1]
In a first example of the related art, an independent transmitting device corresponding to a plurality of communication systems is built in one transmitter. A transmitter supporting two communication systems is called a dual mode transmitter, and a transmitter supporting more than two communication systems is called a multi-mode transmitter. Examples of products that have actually been put into practical use include, for example,
Dual mode mobile phone compatible with PDC system and PHS system,
Dual-mode mobile phones compatible with W-CDMA and PDC systems,
A wireless LAN module supporting two communication standards of IEEE 802.11a and IEEE 802.11b,
and so on. In any case, by supporting a plurality of communication methods, the user can obtain great convenience.
[0005]
However, in the above three examples, an independent transmitting / receiving device is built in corresponding to two different communication systems, the hardware scale is large and the structure is complicated, and the terminal size is inevitably increased. There is a problem that power consumption increases and manufacturing cost increases because of having a plurality of transmission / reception devices.
As an extension of the conventional technology, there is a technology called a combo chip in which two or more transmitting devices are built in one LSI chip. However, although the size and the manufacturing cost are suppressed, the complexity and consumption of the system are reduced. The increase in power remains a problem.
[0006]
[Prior art 2]
As a second example of the prior art, FIG. 12 shows a configuration method of a wireless transmitter described in Patent Literature 1, and its features will be described below. The transmitter in FIG. 12 includes a signal processing unit 50 that outputs a control signal specifying one of the first and second communication schemes and a baseband signal (BB signal) corresponding to the specified communication scheme, , A synthesizer (oscillator) 51 that outputs a local oscillation signal (LO signal) corresponding to, a quadrature modulator 52 to which a BB signal and an LO signal are input, a first wireless unit corresponding to a first communication scheme, and a second A second wireless unit 55 corresponding to the communication system and a switch 53 for selecting either the first or the second wireless unit according to a control signal are provided.
[0007]
In the signal processing unit 50, 50A and 50B are BB signal terminals for I channel and Q channel, and 50C is a control signal terminal. The IQ signals from the terminals 50A and 50B are mixed with the LO signal from the synthesizer 51 by the quadrature modulator 52, and a modulated signal is output. By switching the switch 53, the modulated signal is output from the terminals 56 and 57 after being processed by the first wireless unit 54 or the second wireless unit 55.
[0008]
Here, the operation of the quadrature modulator 52 used in the transmitter of FIG. 12 will be briefly described by taking an example of a QPSK (Quadrature Phase Shift Keying) modulation method as an example. The QPSK modulation is a method of modulating the phase of a carrier signal with four values having phases different by 90 °. The quaternary phase information can be plotted on a phase plane, and can be decomposed into an I component (In-phase component) and a Q component (Quadrature-phase component). When a trigonometric function is used, the I component is cos φ. (T) and the Q component can be represented as sinφ (t). The quadrature modulator 52 modulates the LO signal cosωt using the I component and the Q component.
[0009]
The quadrature modulator 52 includes two multipliers 52A and 52B and one adder 52C. One multiplier 52A multiplies the LO signal and the I component by cosωt · cosφ (t), and the other multiplier 52B multiplies the LO signal and the Q component by 90 ° out of phase by sinωt · sinφ (t). When these two signals are added by the adder 52C,
cosωt · cosφ (t) + sinωt · sinφ (t) = cos (ωt + φ (t))
And a modulated wave modulated by the phase information is obtained as an output.
As described above, since the quadrature modulator 52 generates the modulation signal using the I channel component and the Q channel component of the BB signal, the BB signal processing unit generates the IQ signal corresponding to the communication system, It has the feature that it can support various modulation schemes.
[0010]
However, in the quadrature modulator 52 shown in FIG. 12, since the modulation is performed using the multiplication and addition represented by the above-described equations, it is necessary that the phase difference between the two LO signals is exactly 90 °. Therefore, a high-precision phase shifter is required, and the quadrature modulator 52 itself requires a high-precision multiplier and adder. Further, the synthesizer 51 and the radio units 54 and 55 corresponding to a plurality of frequency bands are required, so that the hardware scale cannot be avoided. In any case, this may cause an increase in manufacturing cost and power consumption.
[0011]
[Prior art 3]
As a third example of the prior art, FIG. 13 shows a configuration method of a wireless transmitter described in Patent Literature 2, and its features will be described below. A feature of the configuration method of FIG. 13 is that an IQ signal of an intermediate frequency (IF) is generated by digital processing from a baseband IQ signal, and the LO signal is modulated by a quadrature modulator using the IQ signal of the IF. Is a point. The BB signal 60 is mixed with the output of the IF synthesizer 62 by the digital modulation unit 61, and the obtained IQ signal of the IF is D / A converted and filtered, and then output from the LO oscillator 63 by the quadrature modulator (64 to 66). After being mixed and filtered, it is amplified by the power amplifier 68 and output.
[0012]
The feature of this configuration is that the digital IF modulation has a high degree of freedom with respect to the communication system, and the use of a quadrature modulator can support various modulation systems as in the configuration of FIG. is there.
That is, the phase of the LO signal from the LO oscillator 63 is shifted by -90 ° by the phase shifter 67, and the I component of the IQ signal is multiplied by the multiplier 64, and the LO signal from the LO oscillator 63 and the Q component of the IQ signal are Are multiplied by a multiplier 65 and the outputs of the multipliers 64 and 65 are added by an adder 66 to obtain a modulated wave.
[0013]
However, a high-precision phase shifter and a high-precision quadrature modulator are required for the same reason as in the configuration of FIG. Regarding such a problem, Patent Document 2 also deals with another important matter, such as “the fixed frequency local oscillator 63 keeps the balance of the two mixers 64 and 65 at the local oscillator port (LO). 64, 65 must be kept to a tight tolerance to prevent the LO signal from getting inside the transmitted signal. "
[0014]
The applicant has not found any prior art documents related to the present invention other than the prior art documents specified by the prior art document information described in this specification by the time of filing.
[0015]
[Patent Document 1]
JP 2003-008454 A
[Patent Document 2]
JP 2002-526958 A
[Non-patent document 1]
L. Kahn, "Single-sided transmission by environment elimination and restoration," Proc. IRE, pp. 803-806, July 1952
[Non-patent document 2]
P. J. Nagle, D .; P. Burton, E .; P. Heaneyand F. J. McGrath, "A wideband linear amplitude modulator for polar transmitter based on the concept of interleaving delta modulation," 2002 IEEE Information. Solid-State Circuits Conferencing (ISSCC), pp. 296-297, Feb. 2002
[0016]
[Problems to be solved by the invention]
As described above, in the case of considering the application corresponding to a plurality of communication systems with one transmitter, the conventional digital modulation transmitter described above has a complicated hardware configuration of the transmitter. However, there has been a problem that a high-precision circuit operation is required for the element circuit to perform.
The present invention solves such a problem, and a digital modulation transmitter capable of supporting a plurality of communication systems is provided by a simple circuit configuration and a transmitter configuration method that does not require high-precision circuit elements. It is intended to be realized.
[0017]
[Means for Solving the Problems]
In order to achieve such an object, a digital modulation transmitter according to the present invention is used in a communication system, modulates an input signal based on a desired digital modulation scheme, and transmits an obtained digital modulation signal. In a digital modulation transmitter, an oscillating unit that controls an oscillating frequency based on an input frequency control signal and generates a plurality of carrier signals having different phases based on the oscillating frequency, and an oscillating unit based on the input phase control signal And a power amplifier that amplifies the carrier signal from the switch and outputs it as a digital modulation signal.
[0018]
Further, another digital modulation transmitter according to the present invention is used in a communication system, modulates an input signal based on a desired digital modulation method, and transmits the obtained digital modulation signal to a digital modulation transmitter. An oscillator that controls an oscillation frequency based on the frequency control signal and generates a carrier signal based on the oscillation frequency, and a plurality of wireless units that generate and output a desired digital modulation signal from the carrier signal from the oscillator. A frequency divider that divides a carrier signal from an oscillator based on an inputted ratio setting signal and outputs a plurality of carrier signals having different phases; and a frequency divider that is based on an inputted phase control signal. And a switch that selects and outputs one of the carrier signals from the switch, and a digitally modulated signal that amplifies the carrier signal from the switch. In which and a power amplifier that outputs Te.
[0019]
Further, another digital modulation transmitter according to the present invention is used in a communication system, modulates an input signal based on a desired digital modulation method, and transmits the obtained digital modulation signal to a digital modulation transmitter. An oscillation unit that controls the oscillation frequency based on the frequency control signal and generates a plurality of carrier signals having different phases based on the oscillation frequency; and any one of the carrier signals from the oscillation unit based on the input phase control signal. A switch for selecting and outputting a signal, a plurality of radio units for generating and outputting a desired digital modulation signal from the carrier signal from the switch, and a selector for switching and outputting the carrier signal from the switch to any of the radio units The radio section amplifies a carrier signal from the switch and outputs a digitally modulated signal as a power amplifier. It is obtain things.
[0020]
As a specific configuration example of the oscillation unit, an oscillator that controls an oscillation frequency based on an input frequency control signal and generates a carrier signal based on the oscillation frequency, and a carrier signal from the oscillator based on an input ratio setting signal And a frequency divider that outputs a plurality of carrier signals having different phases by dividing the frequency.
The frequency divider may be a multiplier that multiplies the carrier signal from the oscillator based on the ratio setting signal and outputs a plurality of carrier signals having different phases.
[0021]
As the power amplifier, a wideband power amplifier that can amplify carrier signals in different frequency bands obtained from the oscillation unit and the switch may be used, or the gain of the carrier signal is variably controlled based on the input gain control signal. A variable gain type power amplifier may be used.
Further, a frequency modulation signal for frequency-modulating the carrier signal may be used as the frequency control signal, and a phase modulation signal for phase-modulating the carrier signal may be used as the phase control signal. Further, an amplitude modulation signal for amplitude modulating the carrier signal may be used as the gain control signal.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
First, a digital modulation transmitter according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the digital modulation transmitter according to the first embodiment of the present invention.
This digital modulation transmitter includes an oscillating unit 1, a switch 2, a power amplifier 3, and an antenna filter 4.
[0023]
The oscillating unit 1 controls an oscillating frequency based on a frequency control signal 11 input from the outside, and generates a plurality of carrier signals having different phases based on the oscillating frequency.
The switch 2 selects and outputs one of the polyphase carrier signals from the oscillating unit 1 according to the phase control signal 12 input from the outside.
Therefore, the carrier signal selected by the switch 2 is converted to a desired level by the power amplifier 3 as a digital modulation signal based on a desired digital modulation method selected by one or both of the frequency control signal 11 and the phase control signal 12. After being amplified and unnecessary signals outside the band are reduced by the antenna filter 4, the signals are output as transmission signals.
[0024]
Specifically, for example, when the frequency control signal 11 is a binary digital signal corresponding to 0 and 1, the oscillating unit 1 outputs a BFSK (Binary Frequency Shift Keying) modulated carrier signal. At this time, if the signal selected by the switch 2 is fixed, a BFSK modulated wave is transmitted. If the output of the oscillating unit 1 is, for example, a four-phase carrier signal and one of the phases is selected by the switch 2 by the phase control signal 12 without changing the above configuration, a QPSK modulated wave is output. .
Therefore, by selecting either frequency modulation using a frequency modulation signal as the frequency control signal 11 or phase modulation using a phase modulation signal as the phase control signal 12, two BFSK and QPSK signals can be obtained. It can correspond to a modulation method.
[0025]
As described above, in the present embodiment, the oscillating unit 1 that outputs a polyphase carrier signal having an arbitrary frequency and a different phase, and the switch 2 that selects one of the polyphase carrier signals from the oscillating unit 1 are provided. Since these are controlled by one or both of the frequency control signal 11 and the phase control signal 12, the oscillation section 1 realizes the frequency modulation function, and the switch 2 realizes the phase modulation function. A digital modulation transmitter capable of supporting a plurality of communication systems can be realized with a relatively simple circuit configuration and without requiring high-precision circuit elements (claim 1).
The switch 2 for switching the multi-phase carrier signal can be realized with a simple circuit configuration such as a pass transistor using an FET. Further, the oscillation unit 1, the power amplifier 3, and the antenna filter 4 can be realized by a known technique.
[0026]
[Second embodiment]
Next, a digital modulation transmitter according to a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram showing a configuration of a digital modulation transmitter according to a second embodiment of the present invention.
The digital modulation transmitter according to the present embodiment uses a power amplifier 3A having a function of changing an amplification gain, instead of the power amplifier 3, as compared with the above-described first embodiment (see FIG. 1). The difference is that the gain is controlled by the gain control signal 13.
[0027]
As described above, in the present embodiment, the variable gain power amplifier 3A is used in addition to the above-described first embodiment, so that the same effects as those of the above-described first embodiment can be obtained. In addition, the effect of reducing the generation of unnecessary harmonics in the case of phase modulation can be obtained.
Normally, when the carrier signal is phase-modulated, the phase signal is modulated, and the modulated signal has a fluctuated envelope. On the other hand, in the first embodiment, when performing phase modulation, modulation is performed by switching only the phase, and the envelope generates a constant modulated wave. Therefore, the output carrier signal is unnecessary. It contains harmonics.
[0028]
In this regard, if the amplitude of the carrier signal is also controlled according to the phase control signal 12 as in the present embodiment, the carrier signal can be made closer to the original phase-modulated carrier signal, and unnecessary harmonics can be suppressed. it can. This principle is known as an EER (Envelope Elimination and Restoration) method. This is the method proposed by Kahn.
Non-Patent Document 2 discloses a configuration method of a transmitter that applies this method to digital modulation. The configuration disclosed in this document relates to only digital phase modulation, and as in the present embodiment, It cannot support both frequency modulation and phase modulation.
[0029]
Further, as a new effect of the present embodiment, the function of frequency modulation and phase modulation by the control signals 11 and 12 and the function of amplitude modulation using an amplitude modulation signal as the gain control signal 13 are realized at the same time. Can be. If the gain control signal 13 is an analog signal, AM modulation can be realized, and if it is a digital signal, ASK modulation function can be realized.
Further, in principle, by using the phase control signal 12 and the gain control signal 13 simultaneously, it is possible to cope with multi-level QAM modulation.
For example, in the case of the existing 16 QAM, it is considered that the configuration using the quadrature modulator is easier to realize. In the case of supporting the multi-level QAM modulation, the signal point design suitable for the transmitter configuration method of the present embodiment is considered. Need to be considered.
[0030]
Further, as a specific configuration of the oscillation unit 1 in FIGS. 1 and 2, as shown in FIG. 3, an oscillator 1A that controls an oscillation frequency based on a frequency control signal 11 and generates a carrier signal based on the oscillation frequency. And a frequency divider 5 that divides the carrier signal from the oscillator 1A based on the division ratio set by the input ratio setting signal 15 and outputs a plurality of carrier signals having different phases. Alternatively, a polyphase carrier signal can be easily generated with a simple configuration (claim 4).
At this time, the frequency divider 5 may be replaced by a multiplier, and the carrier signal from the oscillator 1A may be multiplied based on the multiplication ratio set by the ratio setting signal to output a plurality of carrier signals having different phases. Claim 5).
[0031]
In FIG. 3, a fixed gain type power amplifier 3 may be used. However, by providing a variable gain type power amplifier 3A and making it possible to modulate the amplitude, a case where The generation of unnecessary harmonics can be reduced, and the amplitude modulation function can be realized together.
[0032]
[Third Embodiment]
Next, a digital modulation transmitter according to a third embodiment of the present invention will be described with reference to FIG. FIG. 4 is a block diagram illustrating a configuration of a digital modulation transmitter according to a third embodiment of the present invention.
This digital modulation transmitter includes an oscillator 1A, a first radio unit 20A, and a second radio unit 20B. Further, the first radio unit 20A and the second radio unit 20B include a frequency divider 5, a switch 2, a power amplifier 3A, and an antenna filter 4.
[0033]
The oscillator 1A, the frequency divider 5, the switch 2, the power amplifier 3A, and the antenna filter 4 are the same as those in the first and second embodiments.
In the first radio section 20A, the frequency divider 5 generates a polyphase carrier signal based on the output of the oscillator 1A. The switch 2 selects a carrier signal of any phase from the multi-phase carrier signal, amplifies the carrier signal with the power amplifier 3A, reduces unnecessary wave components with the antenna filter 4, and outputs the signal as a desired digital modulation signal.
Similarly, in the second radio unit 20B, the output of the oscillator 1A is processed by the frequency divider 5, the switch 2, the power amplifier 3A, and the antenna filter 4, and is output as a desired digital modulation signal.
[0034]
At this time, the carrier signal frequency of the carrier signal output from the first radio unit 20A and the second radio unit 20B is determined by the frequency division ratio of each frequency divider 5. In the frequency dividers 5 of the first radio unit 20A and the second radio unit 20B, different division ratios are set by the individual ratio setting signals 15, respectively. As a result, the first radio unit 20A and the second radio unit 20B The frequency of the carrier signal is different.
The entire transmitter has a function of switching between the first wireless unit 20A and the second wireless unit 20B according to the ratio setting signal 15.
[0035]
Specifically, a differential oscillator that oscillates in the 1.2 GHz band is used as the oscillator 1A, and is multiplied by 2 by the frequency divider (multiplier) 5 in the first radio unit 20A to obtain a 2.4 GHz multiphase carrier signal. Is generated, and one of the carrier signals is selected by the switch 2, and a 2.4 GHz carrier signal is output via the power amplifier 3A and the antenna filter 4.
[0036]
In this case, the signal selection of the switch 2 may be fixed, and the switch 2 may be omitted. In the first wireless unit 20A, by making the frequency of the oscillator 1A variable by the frequency control signal 11, it is possible to transmit in accordance with the Bluetooth standard which is one of the short-range wireless communication standards. The Bluetooth communication system transmits and receives a BFSK modulated wave using frequency hopping spread spectrum. By performing control corresponding to the frequency hopping and the BFSK modulation on the frequency control signal 11, a transmitter for Bluetooth can be obtained.
[0037]
On the other hand, in the second radio section 20B, the output of the oscillator 1A of 1.2 GHz is frequency-divided by the frequency divider 5 to generate a 4-phase carrier signal in the 300 MHz band. The four-phase carrier signal can be modulated by QPSK by switching with the switch 2, and output as a 300 MHz band carrier signal via the power amplifier 3A and the antenna filter 4. In particular, in the 300 MHz band, if the electric field strength at a place 3 m away from the transmitter is 500 μV / m, a weak radio system can be used, and the modulation system can be selected relatively freely.
[0038]
Therefore, in the above example, a transmitter having two functions of a 2.4 GHz band Bluetooth transmitter and a 300 MHz band weak radio QPSK transmitter can be realized with a simple circuit configuration.
As described above, in the present embodiment, the first radio section 20A and the second radio section 20B are provided, and the frequency division ratio of each frequency divider 5 is individually controlled by the ratio setting signal 15, so that the In addition to the effect of the second embodiment, an effect is obtained that a modulation wave can be transmitted by selecting a modulation method of two different frequency bands relatively freely while sharing the oscillator 1A (claim 2). .
[0039]
In FIG. 4, a fixed gain type power amplifier 3 may be used. However, by providing a variable gain type power amplifier 3A so as to be capable of amplitude modulation, the phase modulation is performed in the same manner as described above. The generation of unnecessary harmonics can be reduced, and the amplitude modulation function can be realized together.
Further, one or both of the frequency dividers 5 of the first radio unit 20A and the second radio unit 20B may be multipliers (claim 5).
[0040]
[Fourth Embodiment]
Next, a digital modulation transmitter according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 5 is a block diagram showing a configuration of a digital modulation transmitter according to a fourth embodiment of the present invention.
This digital modulation transmitter includes an oscillating unit 1B, a switch 2, a selector 6, a first wireless unit 21A, and a second wireless unit 21B. As in FIG. 3 described above, the oscillating unit 1B includes an oscillator 1A and a frequency divider 5. In addition, the first wireless unit 21A and the second wireless unit 21B include a power amplifier 3A and an antenna filter 4.
[0041]
The oscillating unit 1B, the switch 2, the power amplifier 3A, and the antenna filter are the same as in the third embodiment. The selector 6 switches and outputs the carrier signal selected by the switch 2 to either the first wireless unit 21A or the second wireless unit 21B.
Note that the number of wireless units is not limited to two, and three or more wireless units may be provided according to the number of frequency bands to be supported, and a selector 6 corresponding to the number of wireless units may be used.
[0042]
As described above, in the present embodiment, the frequency divider 5 and the switch 2 of each wireless unit in the third embodiment described above (see FIG. 4) are shared, and the frequency divider 5 is switched by the ratio setting signal 15. And the selector 6 is switched, and the output of the switch 2 is switched and output to either the first radio unit 21A or the second radio unit 21B according to the carrier signal frequency. , The oscillating unit 1B and the switch 2 can be shared, and carrier signals of two different frequency bands can be generated. Therefore, the same effect as that of the fourth embodiment can be realized by a smaller circuit block.
[0043]
In FIG. 5, a fixed gain type power amplifier 3 may be used. However, by providing a variable gain type power amplifier 3A and making it possible to modulate the amplitude, a case where phase modulation is performed in the same manner as described above. The generation of unnecessary harmonics can be reduced, and the amplitude modulation function can be realized together.
Further, as for the oscillating unit 1B, another known oscillating unit 1 may be used as in the first embodiment (FIG. 1). However, since the oscillating unit 1B includes the oscillator 1A and the frequency divider 5, the oscillating unit 1B is simplified. A polyphase carrier signal can be easily generated with a simple configuration (claim 4). In this case, instead of the frequency divider 5, a frequency multiplier that multiplies the carrier signal from the oscillator 1A based on the ratio setting signal and outputs a plurality of carrier signals having different phases may be used.
[0044]
Next, a digital modulation transmitter according to a fifth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a block diagram showing a configuration of a digital modulation transmitter according to a fifth embodiment of the present invention.
The digital modulation transmitter according to the present embodiment differs from the fourth embodiment (see FIG. 5) in that a wideband power amplifier 3B is used instead of the power amplifier 3A to reduce the power consumption of each radio unit. The amplifier 3A and the antenna filter 4 are shared. Note that the oscillating unit 1B, the switch 2, and the antenna filter 4 are the same as in the fourth embodiment.
[0045]
In the above-described first to fourth embodiments, a narrow band amplifier that amplifies only a signal in a specific frequency band is used as a power amplifier. This is because a narrow band amplifier has a feature that power consumption can be suppressed lower and unnecessary signals outside the band are not amplified.
However, even for a wideband amplifier, by controlling the amplification gain by the gain control signal 13, the generation of unnecessary harmonics can be suppressed, and the output of unnecessary signals can be reduced. This effect is as described in the second embodiment.
[0046]
Narrowband amplifiers have the characteristic of low power consumption.However, having an independent radio unit corresponding to multiple communication systems complicates the hardware configuration and causes interference between different radio units. Problems may occur.
In this embodiment, since the wideband power amplifier 3B is used, a radio unit for each modulation scheme is not required, and the hardware configuration can be simplified, and there is no need to switch a plurality of radio units. The selector 6 used in the above-described fourth embodiment becomes unnecessary (claim 6). According to the present embodiment, one practical solution can be obtained for applications in which the hardware configuration is to be simplified and interference between wireless units is to be avoided prior to an increase in power consumption.
[0047]
In FIG. 6, a fixed-gain power amplifier 3 may be used in a wide band, but by adopting a configuration capable of amplitude modulation using a variable-gain power amplifier in a wide band, phase modulation is performed in the same manner as described above. In this case, unnecessary harmonics can be reduced, and the amplitude modulation function can be realized together.
[0048]
[Oscillator and frequency divider]
The following specific configurations may be used for the oscillator 1A and the frequency divider 5 used in each of the above embodiments.
FIG. 7 shows a specific circuit example of the oscillator 1A. In this example, an LC resonator having a resonance frequency ω = 1 / √LC is constituted by an inductor L and a MOS varactor capacitance C, and an oscillator is formed by combining with a cross-coupled negative resistance element of a MOS transistor M31 and a MOS transistor M32. (Astable multivibrator).
[0049]
That is, in this oscillator, the source terminal of M33 is connected to the power supply voltage V, and two L terminals are connected to its drain terminal. Two capacitors C composed of MOS transistors M34 and M35 are connected in series between the other ends of L, and M31 and M32 are connected between the two other ends of L and the ground potential GND. A negative resistance element is connected. Further, a predetermined potential Vbias is connected to the gates of M34 and M35, which are commonly connected, and M33.
This oscillator can generate 0 ° and 180 ° differential clock signals vp and vn. The transistor M33 also serves to keep the current consumption of the circuit constant and to keep the phase difference between the output differential signals at 180 °.
[0050]
FIG. 8 shows a specific circuit example of the frequency divider 5. This frequency divider is a 1/4 frequency divider using two D flip-flops (D-FF) called a Johnson counter. Here, carrier signals having different phases (π, π / 4, π / 2, 3π / 4) by 90 ° used in the QPSK modulation method are generated.
[0051]
That is, the clock signal vp from the oscillator 1A is input to each of the clk input terminals of the D-FF 36 and the D-FF 37, and vp and 180 ° are respectively applied to the / clk input terminal (the inverted logic of the clk input terminal). The clock signal vn from the oscillator 1A having a phase difference is input.
The D input terminal and the / D input terminal (the inverted logic of the D input terminal) of the D-FF 36 are connected to the Q output terminal and the / Q output terminal (the inverted logic of the Q output terminal) of the D-FF 37, respectively. The D output terminal and the / D input terminal (the inverted logic of the D input terminal) of the FF 37 are connected to the Q output terminal and the / Q output terminal of the D-FF 36, respectively.
[0052]
According to such a configuration, four-phase signals IP, IN, QP, and QN whose clock periods are divided by 1/4 are generated from the differential clock signals vp and vn, and the Q output terminals of the D-FF 36 are respectively generated. It is output from the Q output terminal, the Q output terminal of the D-FF 37, and the / Q output terminal.
Therefore, since the configuration of these D flip-flops and the connection of the circuits are symmetrical, a four-phase carrier signal can be generated with high accuracy by a relatively simple circuit configuration, and the divided output is switched. Thus, a modulated signal of QPSK modulation can be realized.
[0053]
FIG. 9 shows a specific circuit example of the D flip-flop used in the frequency divider 5 of FIG.
This D flip-flop has a CML (Current Mode Logic) configuration in which a plurality of differential amplifiers composed of two MOS transistors are combined, and is capable of high-speed operation and has an analog circuit designed by appropriate circuit design. It can also handle signals and can be used in frequency dividers to generate carrier signals. The D flip-flop in FIG. 7 is based on a known technique, and a detailed description of its configuration and operation will be omitted.
[0054]
10 and 11 show simulation results for the operation of the oscillator 1A and the frequency divider 5. FIG. 10 is an output waveform diagram of the oscillator 1A of FIG. 87, and FIG. 11 is an output waveform diagram of the frequency divider 5 of FIG.
In these output waveform diagrams, the horizontal axis is time (ns), and the vertical axis is output voltage (mV). Here, it can be seen that clock signals vp and vn having a frequency of 1.2 GHz and opposite phases are generated in the oscillator 1A. In addition, it can be seen from the vp and vn that the frequency divider 5 generates four signals IP, IN, QP, and QN having a frequency of 300 MHz and phases different from each other by 90 ° as carrier signals.
[0055]
[Variable gain power amplifier]
For the variable gain power amplifier 3A used in each of the above embodiments, a saturation amplifier circuit may be used.
The saturation amplifier circuit refers to, for example, a circuit that amplifies an input signal by operating an MOS transistor in a saturation region when the amplifier is configured by a MOS transistor. In such a saturated region, the drain voltage V _DS Changes in the drain current I _D And the MOS transistor operates as a current source, so that a highly efficient amplifier can be realized by using this.
[0056]
For details of this type of high-frequency amplifier, see, for example, Yoichiro Takayama, "Microwave Transistor", IEICE, pp192-200, 1998, and Kuroda, "RF Microelectronics", Maruzen, pp325-339, 2002. Etc., and detailed description here is omitted.
Such a saturated amplifier circuit can control gain, for example, by controlling a bias voltage to a transistor in an amplification stage, and can increase power addition efficiency and reduce power consumption as compared with a linear amplifier.
[0057]
When the power supply voltage is changed by the linear amplification circuit, the operating point of the amplifier may change and the linear operation may not be performed, so that the variable range is limited. On the other hand, a saturated amplifier operates when the power supply voltage is a certain level or more, and therefore it is not necessary to consider the linearity of the amplifier. Further, when the gain may be small, the power supply voltage is lowered to lower the amplification gain, so that a transmission device with low power consumption and high power addition efficiency can be configured.
[0058]
As described above, the characteristic that the saturation amplifier is used for signal amplification allows the gain to be controlled by the power supply voltage, and allows the gain control circuit to have a simple circuit configuration and to reduce power efficiency. A good digital modulation transmitter can be constructed.
Further, the saturation amplifier circuit used in the present invention is not limited to an amplifier using a MOS transistor, but includes a bipolar transistor, a compound FET, and circuit elements such as a vacuum tube and an electron tube having the above-described operating characteristics. You may comprise using it.
[0059]
Each of the constituent circuits used in each of the above embodiments may be configured with individual circuit components, or all of the constituent circuits may be mounted on one integrated circuit.
[0060]
【The invention's effect】
As described above, according to the present invention, in the oscillating unit, a plurality of carrier signals having different phases are generated from the carrier signal obtained by controlling the oscillation frequency based on the frequency control signal. A desired digital modulation signal is obtained by selecting one of the carrier signals with a switch based on the control signal, so that by arbitrarily selecting the frequency control signal and the phase control signal, various types of signals can be obtained with the same circuit configuration. A digital modulation signal according to the communication system can be obtained. Therefore, it is possible to realize a digital modulation transmitter that can correspond to various communication systems with a simple circuit configuration including the oscillation unit and the switch and does not require high-precision circuit elements.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a digital modulation transmitter according to a first embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a digital modulation transmitter according to a second embodiment of the present invention.
FIG. 3 is a block diagram illustrating a specific configuration example of an oscillation unit.
FIG. 4 is a block diagram illustrating a configuration of a digital modulation transmitter according to a third embodiment of the present invention.
FIG. 5 is a block diagram showing a configuration of a digital modulation transmitter according to a fourth embodiment of the present invention.
FIG. 6 is a block diagram illustrating a configuration of a digital modulation transmitter according to a fifth embodiment of the present invention.
FIG. 7 is a circuit diagram showing a specific configuration example of an oscillator.
FIG. 8 is a circuit diagram showing a specific configuration example of a frequency divider.
FIG. 9 is a circuit diagram showing a specific configuration example of a D flip-flop used in FIG.
FIG. 10 is a waveform chart showing an oscillation output obtained by a simulation result of the oscillator of FIG. 7;
FIG. 11 is a waveform diagram showing a divided output obtained by a simulation result of the divider of FIG. 8;
FIG. 12 is a block diagram showing a configuration of a conventional transmitter.
FIG. 13 is a block diagram showing a configuration of another conventional transmitter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... oscillation part, 1A ... oscillator, 1B ... oscillation part, 2 ... switch, 3 ... power amplifier, 3A ... power amplifier (variable gain type), 3B ... power amplifier (broadband type), 4 ... antenna filter, 5 ... minute Frequency divider (multiplier), 6 selector, 11 frequency control signal, 12 phase control signal, 13 gain control signal, 15 ratio setting signal, 20A, 21A first radio section, 20B, 21B second Radio section.

Claims (10)

Used in a communication system, the input signal is modulated based on a desired digital modulation scheme, in a digital modulation transmitter that transmits the obtained digital modulation signal,
An oscillation unit that controls an oscillation frequency based on the input frequency control signal and generates a plurality of carrier signals having different phases based on the oscillation frequency;
A switch that selects and outputs one of the carrier signals from the oscillation unit based on the input phase control signal,
A power amplifier for amplifying a carrier signal from the switch and outputting the digital signal as a digital modulation signal. Used in a communication system, a digital modulation transmitter that modulates an input signal based on a desired digital modulation scheme and transmits the obtained digital modulation signal,
An oscillator that controls an oscillation frequency based on the input frequency control signal and generates a carrier signal based on the oscillation frequency;
A plurality of radio units for generating and outputting a desired digital modulation signal from a carrier signal from the oscillator,
The wireless unit,
A frequency divider that divides a carrier signal from the oscillator based on the input ratio setting signal and outputs a plurality of carrier signals having different phases,
A switch that selects and outputs one of the carrier signals from the frequency divider based on the input phase control signal,
A power amplifier for amplifying a carrier signal from the switch and outputting the digital signal as a digital modulation signal. Used in a communication system, a digital modulation transmitter that modulates an input signal based on a desired digital modulation scheme and transmits the obtained digital modulation signal,
An oscillation unit that controls an oscillation frequency based on the input frequency control signal and generates a plurality of carrier signals having different phases based on the oscillation frequency;
A switch that selects and outputs one of the carrier signals from the oscillation unit based on the input phase control signal,
A plurality of radio units for generating and outputting a desired digital modulation signal from the carrier signal from the switch,
A selector for switching and outputting a carrier signal from the switch to any of the wireless units,
The wireless unit,
A digital modulation transmitter comprising a power amplifier that amplifies a carrier signal from the switch and outputs the signal as a digital modulation signal. The digital modulation transmitter according to claim 1 or 3,
The oscillating unit includes:
An oscillator that controls an oscillation frequency based on the input frequency control signal and generates a carrier signal based on the oscillation frequency;
A frequency divider for dividing a carrier signal from the oscillator based on the input ratio setting signal and outputting a plurality of carrier signals having different phases. In the digital modulation transmitter according to claim 2 or 4,
A digital modulation transmitter, wherein the frequency divider multiplies a carrier signal from the oscillator based on the ratio setting signal and outputs a plurality of carrier signals having different phases. The digital modulation transmitter according to claim 1,
The digital modulation transmitter according to claim 1, wherein the power amplifier is a wideband power amplifier that can amplify carrier signals in different frequency bands obtained from the oscillation unit and the switch. The digital modulation transmitter according to any one of claims 1 to 6,
The digital modulation transmitter according to claim 1, wherein the power amplifier comprises a variable gain type power amplifier that variably controls an amplification gain of the carrier signal based on an input gain control signal. The digital modulation transmitter according to any one of claims 1 to 7,
A digital modulation transmitter using a frequency modulation signal for frequency-modulating a carrier signal as the frequency control signal. The digital modulation transmitter according to any one of claims 1 to 8,
A digital modulation transmitter using a phase modulation signal for phase modulating a carrier signal as the phase control signal. The digital modulation transmitter according to claim 7,
A digital modulation transmitter using an amplitude modulation signal for amplitude modulating a carrier signal as the gain control signal.

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