JPS5851602A - Orthogonal modulation circuit - Google Patents

Abstract

PURPOSE:To keep the orthogonality independently of an error caused at a 90 deg.- phase shifter, by producing a canceling component for a modulated signal before the orthogonal modulation of the signal and zeroing the error produced at the orthogonal modulation. CONSTITUTION:A modulated signal Y to be orthogonally modulated is applied to one input of an addition circuit 8 via a coefficient device 7 and another modulated signal X is applied to another input of a circuit 8 and they are synthesized. This synthesis signal and the signal Y are respectively applied to balanced modulators 2 and 3. A carrier wave applied to a modulator 2 is phase-shifted at a 90 deg. phase shifter 1 to the carrier wave applied to the modulator 3. The coefficient device 7 adjusts the weighting to the signal Y. This, the error component produced at the phase shifter 1 can be adjusted to be canceled at the coefficient device 7, then an orthogonal modulation signal having 90 deg. of orthogonality can be outputted from a hybrid circuit 4 without adjusting the phase shifter 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a quadrature modulation circuit capable of canceling errors occurring in a 90 phase shifter and maintaining orthogonality.

A conventional quadrature modulation circuit is configured as shown in FIG.

When an error occurs in the degree of orthogonality between orthogonally modulated signal components, a means is adopted to maintain the degree of orthogonality by adjusting the 9C phase shifter +1).

In Figure 1, (2) and (3) are mixers (balanced modulators), and the chrysanthemum (chrysanthemum) is a hybrid circuit.

Adjustment of orthogonality using the above means is difficult or impossible due to manufacturing reasons for the 9C phase shifter, such as modularization and mass production of modulation circuits. Due to this fact, the degree of orthogonality of the orthogonal modulation signal cannot be maintained at 9C, and the desired orthogonal modulation signal cannot be transmitted.

The present invention was devised to solve the drawbacks of conventional circuits such as Shiku Tsuchiura's.The purpose of the present invention is to generate a cancellation component in the modulated signal prior to orthogonal modulation of the signal to compensate for the error caused by the orthogonal modulation. An object of the present invention is to provide an orthogonal modulation circuit that can maintain the orthogonality of an orthogonal modulation signal by making it zero irrespective of the error generated in a 9σ phase shifter.

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 2 shows an embodiment circuit of the present invention. This circuit (2) supplies one modulated signal to be orthogonally modulated, such as a Y signal, to the - input of the adder circuit (8) via the coefficient unit α), and also supplies the other input of the adder circuit (8) to the - input of the adder circuit (8). The modulated signal, for example, the X signal, is supplied and combined, and the combined signal and the one modulated signal are supplied to respective inputs of the orthogonal modulation circuit (2) in FIG. This circuit (
In the field, the coefficient multiplier is preferably constructed as a weight-adjustable coefficient multiplier that can adjust the weighting applied to the Y signal.

Next, the operation of the circuit of the present invention having the above configuration will be explained.

When the 9σ phase shifter (+1) in the circuit in Figure 2 has a large error and the output of the coefficient multiplier (7) is also adjusted to zero, the modulated signals (X) and (Y) are as shown in Figure 1. The output of the hybrid circuit (4), that is, the output of the orthogonal modulation circuit is expressed as A = X + Y6 2, and the degree of orthogonality is 9 perfect. is maintained.

Assuming that an error of δ occurs in the 9C phase shifter (1) of the modulation circuit that produces orthogonal modulation as shown in 9,
The orthogonal modulation signal A becomes a signal expressed by A = X + Yej (2+δ), and the orthogonality of the orthogonal modulation signal shifts by δ.

At this time, the weighting amount of the coefficient unit η to the signal (Y) is set as xi
When adjusted so that sδ becomes sδ, the orthogonal modulation signal A at that time
is A = X + Ys(sδ ten Yej(-;
−M)=X+Yjcoaδ, that is, the orthogonality of this orthogonal modulation signal is maintained at 9f.

Thus, maintaining orthogonality according to the present invention is achieved without any adjustment of the 9σ phase shifter.

Therefore, even if the 9f phase shifter has no adjustment function at all, or even if it is placed in an environment where adjustment using the adjustment function is difficult or impossible, the orthogonality of the orthogonal modulation signal can be maintained at a desired value. .

In the above embodiment, two modulated signals have been described, but the present invention can also be applied to three or more modulated signals that are mutually orthogonally modulated.

In summary, according to the present invention, the degree of orthogonality of the orthogonal modulation signal can be maintained at a desired value without making any adjustments to the 9C phase shifter. This is especially useful when quadrature modulators become modular and integrated circuits and can no longer rely on adjustment by a 9σ phase shifter.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a known quadrature modulation circuit, and FIG. 2 is a diagram of a quadrature modulation circuit according to the present invention. In the figure, (1) is a 9σ phase shifter, (2), (3) is a mixer, (4 is a hybrid circuit, ff) is a coefficient unit, (8)
is an adder circuit. Figure 1 Figure 2

Claims (2)

[Claims] (1) One modulated signal whose orthogonality I4 should be decreased is supplied to an adder circuit via a coefficient unit and combined with the other modulated signal, and the combined signal and the above-mentioned one modulated signal are orthogonally modulated. A quadrature modulation circuit characterized by being configured as follows. (2) The orthogonal modulation circuit according to claim 1, wherein the coefficient unit is constructed as a weight-adjustable coefficient unit.