JPH0662065A - Orthogonal modulator - Google Patents

Abstract

PURPOSE:To realize the orthogonal modulator used for digital mobile communication small in a carrier component, image component and modulation distortion component, excellent in modulation characteristics and low in current consumption. CONSTITUTION:This device is provided with a 90 deg. distributor 15 for distributing a carrier into two components, in-phase and orthogonal double balance mixers 16 and 17, and output buffer amplifier and espacially, this output buffer amplifier is composed of the two steps of a low current differential amplifier 18 and one-input/one-output buffer amplifier 19. Thus, the orthogonal modulator small in the carrier component, image component and modulation distortion component, excellent in the modulation characteristics and low in the current consumption can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quadrature modulator used for digital mobile communication.

[0002]

2. Description of the Related Art In recent years, with the promotion of digitalization of mobile communications, quadrature modulators have been made into ICs with the aim of realizing good modulation characteristics with low power consumption.

A conventional quadrature modulator will be described below. FIG. 6A is a block connection diagram showing a configuration of a conventional quadrature modulator. In FIG. 6A, 1 is a carrier input terminal, 2 is a modulation output terminal, 3 is an in-phase signal input terminal of a modulation baseband signal, 4 is a quadrature signal input terminal of a modulation baseband signal, and 5 is a carrier. 90 ° distributor for 2 distribution, 6 for double-balanced mixer (DBM) for in-phase signal,
Reference numeral 7 is a quadrature signal double balance mixer (DBM), and 8 is a differential output buffer amplifier.

Incidentally, FIG. 6B shows the circuit configuration of the differential output buffer amplifier. In the figure, 80
Is a power supply voltage terminal, 81 and 82 are input signal terminals for inputting two combined outputs from the DBMs 6 and 7 for in-phase signals and quadrature signals, and 83 and 84 are connected to the collector sides of the transistors 85 and 86, respectively. Resistors 87, 88 are current sources connected to the emitter sides of the transistors 85, 86, respectively, and 89 is a resistor connected between the emitters of the transistors 85, 86.

The operation of the quadrature modulator having the above structure will be described below. First, the carrier input from the carrier input terminal 1 is distributed by the 90 ° distributor 5 into two signals having a phase difference of 90 °.
6 and DBM7 for orthogonal signals. The two 90 ° -divided signals are multiplied by the modulated baseband signals input from the in-phase signal input terminal 3 and the quadrature signal input terminal 4 in the DBMs 6 and 7, respectively. The in-phase and quadrature modulated signals multiplied by the carrier are directly combined, and the image component is canceled at this time. The combined two outputs are input to the differential output buffer amplifier 8,
At this time, since the two-output carrier component and the even-order distortion component are in phase, these components cancel each other and are suppressed. In this way, a carrier-modulated signal is obtained at the output according to the modulated baseband signal, and is taken out from the output terminal 2.

[0006]

However, in the above configuration, when the external output load is low impedance, a large amount of current is passed through the differential output buffer amplifier in order to perform impedance conversion with low distortion. I don't get. Moreover, if two external outputs are not required, half of the current consumption is wasted. Further, since the conventional output buffer amplifier plays a role of suppressing carrier leak and distortion by making it a differential type, one component of the double balance mixer composite output is taken out and the impedance conversion is performed by an emitter follower or the like. do it,
There is a problem that taking out to the outside leads to leakage of carrier components and even-order distortion components.

The present invention solves the above-mentioned problems of the prior art. It is an object of the present invention to provide a quadrature modulator which consumes a small amount of current while keeping a carrier component and a modulation distortion component small and has a circuit configuration suitable for IC implementation. And

[0008]

In order to achieve this object, the present invention provides an output buffer amplifier, a low current differential amplifier, and
A two-stage configuration of a buffer amplifier with one input or two inputs and one output is used, and the two roles of suppressing spurious components such as carrier components and modulation distortion components and extracting the output to a low impedance load are divided into each amplifier. by doing,
The configuration is such that the current consumption can be reduced while maintaining a large suppression ratio of the carrier component and the modulation distortion component.

[0009]

According to the present invention, the differential amplifier connected to the output of the double balance mixer according to the present invention suppresses the carrier component and the even-order distortion component leaked from the double balance mixer, and the buffer amplifier connected in the subsequent stage. Since the input impedance is very high, it is possible to realize a differential amplifier with low current and low distortion. Also, by having separate amplifiers perform the two roles of suppressing spurious components and taking out the output to the outside, it is possible to use only one system of buffer amplifier when two systems of external output are not required. As compared with the case where only the differential amplifier is used as the buffer amplifier, the unnecessary current can be reduced and the current consumption can be reduced.

[0010]

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block connection diagram of a quadrature modulator according to a first embodiment of the present invention. In FIG. 1, 11 is a carrier input terminal, 12 is a modulation output terminal, 13 is an in-phase signal input terminal of a modulation baseband signal, 14 is a quadrature signal input terminal of a modulation baseband signal, and 15 is a carrier that is divided into two. A 90 ° distribution amplifier, 16 is a double balance mixer (DBM) for in-phase signals, 17 is a double balance mixer (DBM) for quadrature signals, 18 is a low current differential amplifier, and 19 is a 1-input 1-output buffer amplifier.

2 and 3 are a low-current differential amplifier 18 and a 1-input 1-output buffer amplifier 19 which are essential parts of FIG. 1, respectively.
2 shows detailed circuits as different embodiments.

The low-current differential amplifier 18 shown in FIG. 2 has the same structure as that shown in FIG. 6B, but the constants thereof are different and the current consumption is small. In FIG. 2, 180 is a power supply voltage terminal, 183 and 184 are transistors 185 and 186.
Of resistors 187, 18 connected to the collector side of
8 is a current source connected to the emitters of the transistors 185 and 186, respectively, and 189 is transistors 185 and 1
A resistor connected between the emitters of 86.

On the other hand, in the 1-input 1-output buffer amplifier 19 in FIG. 2, 20 and 21 are power supply voltage terminals, 22 is a transistor for inputting the output signal of the differential amplifier 18 to the base side, and 23 is a power supply voltage terminal 20. And a load resistance connected between the transistor 24 and 25,
, 26 is a capacitor provided between the resistor 23 and the base of the transistor 27, 28 and 29 are resistors respectively connected to the emitter side of the transistor, 30 is a base bias terminal, Reference numerals 31 and 32 are base bias resistors.

Also in FIG. 3, the low-current differential amplifier 18 is of the same low-current-consumption type as the configuration of FIG. 2, so the details of the same parts will be omitted. The difference is that in the 1-input 1-output buffer amplifier 19, a power supply voltage terminal 40, a transistor 41 for inputting the output signal of the differential amplifier 18 to the base side, and a resistor 42 connected to the emitter side of the transistor 41. It is a point that is a component.

The operation of the quadrature modulator configured as described above will be described below. First, the carrier input from the carrier input terminal 11 is
5 is divided into two signals with a phase difference of 90 °
It is distributed and input to the BM 16 and the orthogonal signal DBM 17. Two signals distributed by 90 ° are DBM16 and 1 respectively.
7, the signal is multiplied by the modulated baseband signal input from the in-phase signal input terminal 13 and the quadrature signal input terminal 14. The in-phase and quadrature modulated signals multiplied by the carrier are directly combined, and the image component is canceled at this time. The combined two outputs are input to the low-current differential amplifier 18, but both the carrier component and the even-order distortion component are in-phase inputs and are suppressed here. Therefore, the 1-input 1-output buffer amplifier 19 does not need the spurious suppressing function, and only needs to take out the output of one system (low impedance load). Both the spurious suppressing and taking out to the low impedance load output are possible. Current consumption can be saved compared to an output buffer amplifier that has one function combined with a differential amplifier.

As described above, according to the present embodiment, the low-current differential amplifier 18 that suppresses the in-phase input components such as the carrier component and the even-order distortion component and contributes to the spurious component suppression has the load of 1 input 1. Input impedance of output buffer amplifier 19
Since the dance can be set high, it is possible to obtain low distortion even with low current consumption. Further, when the output load is low impedance and one system is used, the output of the buffer amplifier 19 is 1.
Since it is output, compared to the differential amplification type buffer amplifier,
Low current consumption can be achieved.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a block connection diagram of a quadrature modulator according to the second embodiment of the present invention, and FIG. 5 is a low current differential amplifier 48 which is a main part of the quadrature modulator according to the second embodiment of the present invention.
And a detailed circuit as an embodiment of the buffer amplifier 49.

In FIG. 4, 11 is a carrier input terminal,
Reference numeral 12 is a modulation output terminal, 13 is an in-phase signal input terminal of a modulation baseband signal, 14 is a quadrature signal input terminal of a modulation baseband signal, 15 is a 90 ° distribution amplifier that divides a carrier into two, 16 is an in-phase signal Double balance mixer (DB
M) and 17 are quadrature signal double balance mixers (DB)
In M), the above is the same as the configuration of FIG. 4 is different from FIG. 1 in that the low current differential amplifier 48 has two inputs and two outputs and the buffer amplifier 49 has two inputs and one output.

The 2-input 1-output buffer amplifier 49 shown in FIG. 5 includes a power supply voltage terminal 50, a base bias terminal 51,
A transistor 52 for directly inputting the output signal of the low current differential amplifier 48, a transistor 53 for inputting the other output signal of the low current differential amplifier 48, a DC blocking capacitor 54, a base bias resistor 55, and an emitter resistor 56. To be done.

The operation of the quadrature modulator configured as described above will be described below. 4, the basic operation of the quadrature modulator is the same as that of FIG. 1, so a detailed description thereof will be omitted. However, the difference from the configuration of FIG. 1 is that the low current differential amplifier 48 is a 2-input / 2-output buffer amplifier 49. Is to be two inputs and one output, and both internal output signals of the low current differential amplifier 48 are utilized to simplify the internal circuit configuration of the buffer amplifier 49. That is, in the embodiment shown in FIG. 2, the same role as the inverting amplifier composed of the transistor 24, the load resistor 23, etc. is obtained from the inverting output of the low current differential amplifier 48 in the preceding stage, as shown in FIG. Thus, the internal circuit configuration of the 2-input 1-output buffer amplifier 49 is simplified.

As described above, the 2-input 1-output buffer amplifier 4
By simplifying the internal circuit configuration of 9, it is possible to reduce the current consumption while maintaining the basic performance of the buffer amplifier.

In the embodiments shown in FIGS. 1 to 5, a circuit using a transistor as a low current differential amplifier and a buffer amplifier is shown, but it goes without saying that the active element is not limited to this. In the embodiments shown in FIGS. 1 to 5, a simple method of blocking direct current with a capacitor and biasing it through a bias resistor is shown as the biasing method of the transistor, but the capacitor is not used and the direct current voltage is shifted. Needless to say, the method is not limited to this method.

[0025]

As described above, according to the present invention, the output buffer amplifier of the quadrature modulator comprises a low current differential amplifier and one input or two.
By adopting the two-stage configuration of the input / output buffer amplifier, the leakage current of the carrier component, the image component and the modulation distortion component can be suppressed to a low level, and the current consumption of the buffer amplifier can be reduced to about half that of the conventional one. It realizes an excellent quadrature modulator.

[Brief description of drawings]

FIG. 1 is a block connection diagram of a quadrature modulator according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a main part of a quadrature modulator according to a first embodiment of the present invention.

FIG. 3 is a circuit diagram of a main part of a quadrature modulator according to a first embodiment of the present invention.

FIG. 4 is a block connection diagram of a quadrature modulator according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram of a main part of a quadrature modulator according to a second embodiment of the present invention.

6A is a block connection diagram of a conventional quadrature modulator, and FIG. 6B is a circuit diagram of a main part of a conventional quadrature modulator.

[Explanation of symbols]

 11 Carrier Input Terminal 12 Modulation Output Terminal 13 In-Phase Signal Input Terminal for Modulation Baseband Signal 14 Quadrature Signal Input Terminal for Modulation Baseband Signal 15 90 ° Distribution Amplifier for Dividing Carrier into 2 16 In-Phase Signal Double Balance Mixer ( DBM) 17 Quadrature signal double balance mixer (DBM) 18, 48 Low current differential amplifier 19 1 input 1 output buffer amplifier 49 2 input 1 output buffer amplifier

Claims (5)

[Claims] 1. A 90 ° distributor for dividing a carrier into two parts,
The outputs of the first and second double balance mixers for multiplying the outputs of the 90 ° distributor by the in-phase and quadrature modulated baseband signals, and the outputs of the first and second double balance mixers are respectively provided with a low current difference. A quadrature modulator comprising a dynamic amplifier and an output buffer amplifier that synthesizes and amplifies by a 1-input 1-output buffer amplifier. 2. The quadrature modulator according to claim 1, wherein the 1-input 1-output buffer amplifier incorporates an inverting amplifier therein. 3. The quadrature modulator according to claim 1, wherein the 1-input 1-output buffer amplifier is an emitter follower circuit. 4. A 90 ° distributor for dividing the carrier into two parts,
The outputs of the first and second double balance mixers for multiplying the outputs of the 90 ° distributor by the in-phase and quadrature modulated baseband signals, and the outputs of the first and second double balance mixers are respectively provided with a low current difference. A quadrature modulator comprising a dynamic amplifier and an output buffer amplifier that synthesizes and amplifies by a 2-input 1-output buffer amplifier. 5. The quadrature modulator according to claim 4, wherein the 2-input 1-output buffer amplifier receives as inputs both inverting outputs of the low-current differential amplifier in the preceding stage.