JPS60163506A - Phase modulation circuit - Google Patents

Abstract

PURPOSE:To attain stable and excellent characteristic at a high frequency band and also to attain ease of circuit integration by blocking a DC component and inputting the result to a double balanced differential amplifier circuit after an unbalanced carrier signal is converted into a balanced signal. CONSTITUTION:Two collector outputs of the differential amplifier circuit composisting of transistors (Tr)7, 8 are fed respectively via capacitor C1, C2 as the carrier signal input of the double balanced differential amplifier circuit comprising Trs 1-6. Moreover, the unbalanced carrier signal is inputted from an input terminal CIN to a base of the Tr7 via a bias blocking capacitor C3 and the base of the Tr8 is terminated by a resistor R1 via a bias blocking capacitor C4. Thus, the differential amplifier comprising the Trs 7, 8 is applied with unbalanced signal from one input and there is a difference is the DC operating point between the collectors, the DC component is blocked by the capacitors C1, C2 and no effect is given to the balance of the double balance differential amplifier circuit, and stable phase modulation is attained together with the temperature characteristic.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a balanced modulation circuit based on a differential amplifier circuit composed of transistors, and is particularly suitable for use in a high frequency band such as a wireless communication device. Related to modulation circuits.

[Prior art]

Conventionally, as a phase modulation circuit in a high frequency band.

Ring modulation circuits consisting of diode bridges and balanced transformers were common. However, a circuit using such a transformer has a drawback in that it is not suitable for integration into an integrated circuit.

On the other hand, in recent years, advances in integrated circuit technology have made this possible.

Integrated transistors that can operate at high frequencies have become available, and balanced modulation circuits using integrated circuits that combine differential amplification circuits using high-frequency transistors and resistors have been provided.

This circuit not only does not require a transformer and can be easily obtained, but also has the advantage of being highly accurate since there is no diode bridge and there is no phase change caused by changes in diode capacitance.

However, circuits using transistor differential amplifier circuits have some problems, one of which is the imbalance caused by the difference in junction forward breakdown voltage between two opposing transistors, which are the basic elements of a differential amplifier circuit. There are differences in degree. For this reason, efforts have been made to minimize this difference in balance by making the electrical characteristics of the transistors the same. especially.

When using such a differential amplifier circuit in a phase modulation circuit,
Unless this difference in balance is suppressed to a value that can be ignored, a sufficient suppression ratio of the carrier signal cannot be obtained, which often causes problems in terms of characteristics. To deal with this, a method is usually used, such as adjusting the DC operating point of the differential amplifier circuit and selecting the best point for the carrier wave suppression ratio. Another problem is that the difference in balance generally changes with changes in environmental temperature, and the greater the amount of correction by adjusting the DC operating point, the greater the degree of characteristic deterioration.

On the other hand, in a balanced modulation circuit based on a differential amplifier circuit, in principle, the modulation input signal and carrier wave input signal.

The modulated output signal must be a balanced input/output signal, and when it is an unbalanced input/output signal, a method in which two sides are terminated with a resistor is often used. In contrast, in a high-frequency phase modulation circuit, the modulation input signal is at a relatively low frequency.

Normally, they are handled as balanced signals, but it is difficult to handle them unless the carrier wave signal and modulated output signal are high-frequency, unbalanced signals. Regarding the output signal, one side of the balanced output is terminated with a resistor.

Since a pseudo-balanced load condition is obtained, it is thought that there is almost no effect on the modulation circuit. However, for the carrier signal, the balance of the signal source impedance can be maintained by terminating one side of the balanced input of the differential amplifier circuit with a resistor, but in the operating state, of the two transistors of the differential amplifier circuit, There is a difference in operating conditions between the transistor that receives the carrier wave signal and the transistor that is connected to the termination resistor.

There will be a difference in balance. Therefore, in order to obtain good phase modulation characteristics including temperature characteristics, it is necessary to convert the carrier signal into a balanced signal and input it to the differential amplifier circuit. As mentioned above, if a transformer or the like is used as a means to convert this unbalanced state into a balanced state, it will be difficult to integrate the circuit and it will not be possible to reduce the cost.

[Purpose of the invention]

The present invention was made based on one or more considerations, and an object of the present invention is to provide a phase modulation circuit that exhibits good characteristics even in a high frequency band, is easy to integrate into an integrated circuit, and has stable operation.

This will be explained below with reference to two drawings.

FIG. 1 shows an example in which a balanced modulation circuit is constructed using a transistor differential amplifier circuit, and is a double balanced differential amplifier circuit. In this circuit, the outputs of two sets of differential amplifier circuits, transistors 1°2.5 and 3+4t6, are connected in common with opposite polarities, and transistors 5 and 6 are connected to emitter resistors REI and R, respectively.
It is characterized in that it is connected to a constant current source CC via E2 to form a double balanced differential amplifier circuit. As a result, the balanced signal input to the balanced modulation signal input terminals INI and IN2 can take positive and negative values, and the output is obtained as a balanced signal between the balanced modulation output terminals 0UTI and 0UT2 in proportion to the input terminals 0UTI and 0UT2. It will be done. Therefore, balanced carrier signal input terminal C
By inputting a carrier signal as a balanced signal to INI and ClN2, it can be operated as a two-phase phase modulation circuit.

[Structure of the invention]

The present invention converts an unbalanced carrier signal suitable for use in a high frequency band into a balanced signal using a transistor differential amplifier circuit, and then blocks the DC component using a capacitor and inputs it to a double balanced differential amplifier circuit. It is characterized by being a modulation circuit.

[Embodiments of the invention]

Hereinafter, nine aspects of the present invention will be described in detail.

FIG. 2 shows a circuit according to an embodiment of the present invention, in which transistors 7 and 8 are used as carrier wave signal inputs of a double-balanced differential amplifier circuit composed of transistors 1t2t3, 4, 5, and 6 as in FIG.
The differential outputs, that is, the two collector outputs, of the differential amplifier circuit configured with the circuit are supplied via capacitors C1 and C2, respectively, and the cine balanced carrier signal is supplied to the unbalanced carrier signal input terminal CIN through the bias blocking capacitor C3. The configuration is such that the input is input to the pace of the transistor through the circuit.

The other input of the differential amplifier circuit, the transistor 8, is terminated with a resistor R1 via a bias blocking capacitor C4. B1 to B4 are reader circuits for applying bias.

Is the differential amplifier circuit of transistors 7 and 8 on one side from the input? Since an unbalanced signal is applied, a difference occurs in the degree of balance, and a difference also occurs in the DC operating point between the collectors of transistors 7 and 8, which are differential outputs.
Since the DC component is blocked by this, it does not affect the balance of the double-balanced differential amplifier circuit, and it is possible to operate as a stable phase modulation circuit including temperature characteristics.

〔Effect of the invention〕

According to this phase modulation circuit, the input of the carrier signal from the outside can be an unbalanced signal that is easy to handle in a high frequency band, and by converting the unbalanced carrier signal into a balanced signal, a double balanced differential signal can be input. In the amplifier circuit, characteristic deterioration due to input of unbalanced high frequency signals can be suppressed. In addition, by converting an unbalanced carrier wave signal into a balanced one using a transistor differential amplifier circuit, integration into an integrated circuit is facilitated. Furthermore, by blocking the DC component of the carrier-balanced signal from the transistor differential amplifier circuit using a capacitor, even if one side of the input to the shear transistor differential amplifier circuit is terminated with a resistor, the difference in DC balance that occurs there can be suppressed. It has the advantage of not affecting circuit characteristics.

From the above, it is possible to input an unbalanced carrier signal suitable for use in high frequency bands, and to obtain stable and good characteristics.
Furthermore, by using transistors, resistors, and capacitors as circuit elements, it is easy to integrate the circuit, and by mass producing it, an inexpensive phase modulation circuit can be obtained.

[Brief explanation of the drawing]

Figure 1 shows an example of a double-balanced differential amplifier circuit. FIG. 2 shows a phase modulation circuit according to an embodiment of the present invention. CCI, CC2...constant current source, Bl, B2. B3
゜B4...Bias application leader circuit, INI
, IN2...Balanced modulation signal input terminal, 0UTI
, 0UT2...Balanced modulation signal output terminal, CINI
, ClN2...Balanced carrier signal input terminal, CI
N...Unbalanced carrier signal input terminal. Vco...Circuit power supply, RI...Terminal resistor.

Claims (1)

[Claims] 1. Connecting the emitters of the first and second transistors, connecting the emitters of the third and fourth transistors, and connecting the collectors of the first and third transistors. and the collectors of the second and fourth transistors are connected together, the paces of the first and fourth transistors are connected together, and the second and third transistors are connected together.
It has a double balanced differential amplifier circuit including two sets of differential amplifier circuits in which the paces of transistors are connected to each other.
The emitters of the first and fourth transistors are connected to the two collectors of the differential amplifier circuit through capacitors, respectively. It is connected to the paces of the second and third transistors, one base of the fifth and sixth transistors is terminated with a resistor, and a carrier wave signal is input from the other base. Phase modulation circuit.