JPH0595380A - Orthogonal modulator - Google Patents

Abstract

PURPOSE:To provide a small-sized orthogonal modulator by simplifying an addition circuit for the transmission of a non-modulation carrier wave signal by providing two selection circuits for alternatively selecting two variable DC voltage generation circuit, a DC voltage signal and a base band signal. CONSTITUTION:When a non-modulation carrier wave is outputted, the output signal of a balanced mixer 7 is outputted as it is via an adder 11 and a non- modulation carrier wave of a constant amplitude is obtained since the output voltage of a balanced mixer 8 also becomes 0 when both of switches 5, 6 are switched to a DC voltage side b, the output of a variable DC voltage generator 1 is defined as the constant amplitude and the output voltage of the other variable DC voltage generator 3 is set to 0. When a modulation wave is outputted, the modulation wave can be outputted in the same way as in conventional orthogonal modulator by setting the both of the switches 5, 6 to a base band signal side a.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a quadrature modulator for generating an unmodulated carrier signal.

[0002]

2. Description of the Related Art FIG. 4 shows a basic configuration example of a conventional quadrature modulator using a balanced mixer. In the figure, both signals of the in-phase (I) component and the quadrature (Q) component of the baseband signals generated by the baseband signal generators 2 and 4 are input to the balanced mixers 7 and 8, respectively, and a phase difference of π / 2 is generated. After multiplication with the carrier signal thus held, each multiplication output is added by the adder 11 to obtain a quadrature modulated wave output.

However, in general, it is often necessary for a modulator to output an unmodulated carrier signal, such as when measuring a carrier frequency or outputting a reference level signal, in addition to the above-mentioned modulated wave signal. Therefore, conventionally, as shown in FIG.
An additional circuit is provided in the basic circuit of FIG. 4 so that the quadrature modulated wave signal and the unmodulated carrier signal can be switched and output.

As shown in FIG. 3, as an additional circuit, a switch 22 for switching between a modulated wave and an unmodulated carrier, an attenuator 20 for adjusting the output level of the unmodulated carrier, a balanced mixer input and an unmodulated carrier are used as the carrier. It requires a distributor 21 for distributing to. In the figure, switch 22
Is set to the b side, the level of the carrier wave distributed by the distributor 21 is adjusted by the attenuator 20 and an unmodulated carrier wave is output via the switch 22.

[0005]

In the above-mentioned prior art, when the carrier wave has a high frequency, since an additional circuit is provided in the high frequency section, it is necessary to take measures against matching and reflection of the high frequency signal, so that the circuit scale increases and the device It was hindering miniaturization. The present invention has been made to eliminate this drawback, and an object thereof is to provide a small quadrature modulator in which an additional circuit for transmitting an unmodulated carrier signal is simplified.

[0006]

In order to achieve the above object, the present invention is intended to selectively select two variable DC voltage generating circuits and the DC voltage signal and the baseband signal in a quadrature modulator. The above two selection circuits are provided, and the output of this selection circuit is multiplied by the carrier signal.

[0007]

The operation of the present invention will be described. When outputting an unmodulated carrier, both of the two selection circuits are set to the DC voltage side, and one output voltage of the two DC voltage generators is set to 0 and the other is set. Is set to a constant voltage, one of the outputs of the two multipliers is set to 0, and the unmodulated carrier signal of constant amplitude obtained from the output of the other multiplier is directly output via the adder.

Further, when outputting the modulated wave, the modulated wave can be outputted similarly to the conventional quadrature modulator by setting both of the selection circuits on the side of the baseband signal.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 and 3 are variable DC voltage generators,
Switches 5 and 6 are the same as those in FIG. 3 except the above.

When outputting a modulated wave, both the switches 5 and 6 are set to a on the baseband signal side so that the balanced mixers 7 and 8 are orthogonal to the in-phase component signal A _I (t) of the baseband signal. The component signals A _Q (t) are applied, multiplied by the respective carrier signals, and then added by the adder 11 to obtain a quadrature modulated wave represented by the following equation (1).

[0011] _{S (t) = A I (} t) cos2πf c t + A Q (t) sin2πf c t ‥‥‥ (1) where, f _c denotes the carrier frequency.

Next, when outputting an unmodulated carrier, both the switches 5 and 6 are switched to b on the DC voltage side, for example, the output of the DC voltage generator 1 is set to a constant amplitude A _I m, and the other constant voltage generator is set. When the output voltage of 3 is set to 0, the output voltage of the balanced mixer 8 also becomes 0, so the output signal of the balanced mixer 7 is output as it is via the adder 11, and is shown in the following equation (2). An unmodulated carrier is obtained.

[0013] _{S (t) = A I mcos2πf} c t ‥‥‥ (2)

FIG. 2 shows an example of a digital modulation quadrature modulator according to another embodiment of the present invention. When outputting a quadrature modulated wave, by setting the data selectors 23 and 24 to the a side, the digital baseband signal in-phase component and quadrature component signals are input to the D / A converters 16 and 17, respectively. The baseband signal is converted into an analog signal by the D / A converters 16 and 17, then applied to the balanced mixers 7 and 8 and multiplied by the carrier signals respectively, and then added by the adder 11 to obtain a quadrature modulated wave output. ..

Further, by switching the data selectors 23 and 24 to the b side, constant data set by the address switch 12 is input to the D / A converter 16 and a DC voltage signal for operating the balanced mixer 7 is output. .. Further, the D / A converter 17 is the address switch 1
The output voltage is set to 0 according to the data set in 3.
The output voltage of the balanced mixer 8 is set to 0. Therefore, the unmodulated carrier signal output from the balanced mixer 7 is directly output from the adder 11, and an unmodulated carrier signal having a constant amplitude can be obtained.

[0016]

As described above, according to the present invention, in a quadrature modulator, a low frequency circuit having a small circuit scale can be provided without adding a distributor and an attenuator having a large circuit scale and a large size for high frequency as in the conventional case. An unmodulated carrier can be obtained with only a DC additional circuit, and a small quadrature modulator can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a block diagram showing an example of a conventional quadrature modulator.

FIG. 4 is a block diagram showing a basic configuration of a quadrature modulator.

[Explanation of symbols]

 1,3 Variable DC voltage generator 2 Baseband in-phase analog signal generator 4 Baseband quadrature analog signal generator 5,6 Switch 7,8 Balanced mixer 9 π / 2 Phase shifter 10 Carrier wave signal generator 11 Adder 12, 13 Address switch 16, 17 D / A converter 20 Attenuator 21 Distributor 23, 24 Data selector 14 Baseband in-phase digital signal generator 15 Baseband quadrature digital signal generator

Claims (1)

[Claims] 1. A quadrature modulator for multiplying a two-component signal of an in-phase component and a quadrature component of a baseband signal by a carrier signal and adding the multiplied outputs to obtain a modulated wave signal A circuit and two selection circuits that are connected to the other input of the multiplier that receives the carrier signal as one input and that selectively select and output the DC voltage signal and the baseband signal. And a quadrature modulator.