JPS627207A - High frequency power amplifier circuit - Google Patents

Abstract

PURPOSE:To improve the stability of operation, especially at a low voltage by connecting diodes connected back-to-back in series with a collector of a high frequency transistor (TR) in parallel with an impedance matching circuit and a capacitor. CONSTITUTION:The two varactor diodes 2 are connected back-to-back in series between the collector and emitter of the high frequency TR 1 and act like the same capacitance to positive and negative high frequency signals. Inductors L36, L47 act like base and collector feeding and the inductance being over several times of the input/output impedance is selected, the inductor L4L is connected to a power terminal 11 and to the other terminal of the inductor L36 via a resistor R43 and a diode 44 is connected to the other terminal of the inductor L36 to constitute an amplifier circuit. The resistor R is used for feeding base bias from the terminal 11 and the diode 14 is used to stabilize the potential. Further, capacitors C18, C69 are placed adjacent respectively to input/output terminals 7, 9 to isolate the base from the input terminal and the collector from the output terminal in terms of DC and transmit high frequency components through them.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention aims to stabilize and improve the operation of a high frequency power circuit, and is used in a transmitting stage of a wireless communication device.

[Technical background of the invention]

A high-frequency power amplifier circuit is designed taking into consideration high-frequency output, efficiency, operational stability, operating frequency, high-frequency input, collector voltage dependence, etc.

A known application example of this high-frequency power amplification circuit is the transmission stage of a wireless communication device, which is prohibited by law from emitting radio waves at frequencies other than those allocated to it. Among these wireless communication devices, the power supply voltage used in the transmission stage of the handheld model is 8V and 12.5V, and the output is 12.5V.
V tare W or more, 8V or more is required.

The requirements for the oscillation of this transmitting stage are that the power supply voltage is in the range from about 5V, which rapidly drops due to battery consumption, to 12.5V during high output operation, and even under load conditions in which 80% of the output radio waves return to the transmitting stage. It is mentioned that there should be no oscillation, which must be said to be an extremely strict condition. The reality is that measures are taken to suppress oscillation of amplifiers under such conditions as much as possible, as this becomes the source of radio interference.

Figure 3 shows the transmitting stage amplifier of a handheld model.

The impedance required for power amplification of the high frequency transistor (30) used is approximately 1Ω between base and emitter on the input side.
The impedance between the collector and emitter on the output side is about 10Ω, while the impedance of the signal source on the input side and the load on the output side is 50Ω. For this reason, an impedance matching circuit is required, L1L2C,C,.

A first impedance matching circuit (31) consisting of L, C, C is formed on the input side, and a second impedance matching circuit (32) consisting of L, C, C is formed on the output side. One end of this first impedance matching circuit is connected to a high frequency transistor (3
An inductor L, (33) for base bias power supply is connected in parallel with this matching circuit, and the other end of the first impedance matching circuit is connected to the input terminal (34) connected to the signal source (34). Capacitor C construction (36) installed in 35)
). The emitter of the high frequency transistor is grounded, and its collector is connected to one end of a second impedance matching circuit (32), which is connected in parallel with a capacitor C (37) for stabilizing high frequency operation. On the other hand, the other end of the second impedance matching circuit (32) is connected to an output end (40) connected to a load (39) via a capacitor (38) corresponding to the input side capacitor (36).

Furthermore, the input side inductor L, (33) corresponds to the collector power supply inductor L, (41) is connected to the capacitor C0.
(37) and the second impedance matching circuit (32) in parallel to the collector of the high frequency transistor (30).

Capacitors C1 (36) and C, (38) connected to the input terminal (35) and output terminal (40) provide direct current isolation between the base and input terminal, collector and output terminal of the high frequency silane resistor, and prevent the propagation of high frequency components. It is a capacitor for

The inductor L4 (41) is connected to the power supply terminal Vcc (42), and is also connected to the other end of the inductor L (33) via the resistor R (43).
A diode (44) was connected to the other end to form an amplifier circuit.

This resistor R is a resistor for supplying base bias power from the power supply terminal Vcc (42), and the diode (44) functions to stabilize its potential.

By the way, since the impedance of the signal source (34) and the load (39) is 50Ω as mentioned above, the first and second
The capacitors and inductors constituting the matching circuits (31) and (32) are selected in consideration of frequency characteristics, and the values of the inductors L, (33), and (41) are selected to be several times the input/output impedance.

[Problems with background technology]

As mentioned above, operational stability is strongly required for the amplifier for the transmitting stage of wireless communication equipment.6 For example, when the collector voltage is 0 V,
to the conditions for obtaining the required output, and the voltage standing wave ratio (Voltage Standing Wave Ratio) of this condition and the output load.
It is strongly required that oscillation does not occur under all combination conditions of all phases within a range of 10 (g Wave Ratio).

In the amplifier circuit shown in Figure 2, the capacitor C, (37) has been chosen to be large to improve stability at low voltages.
In terms of impedance matching, it is difficult to improve stability at low voltages, which is contradictory to what happens at high voltages, and it has not always been sufficient to prevent oscillation.

[Purpose of the invention]

The present invention relates to a novel high-frequency power amplifier circuit that eliminates the above-mentioned drawbacks, and particularly improves stability at low voltages.

[Summary of the invention]

In order to achieve this objective, the high frequency power amplifier circuit according to the present invention employs a method in which, in addition to an impedance matching circuit and a capacitor, diodes connected in series in forward and reverse directions are connected in parallel to the collector of the high frequency transistor. A variable capacitance diode is selected as this diode to prevent a short circuit in a specific phase.

[Embodiments of the invention]

The present invention will be explained in detail with reference to FIGS. 1 and 2.

The circuit configuration that differs from the conventional amplifier circuit is that, as mentioned above, the variable capacitance diode (A) is connected in series to the collector of the high frequency transistor (1) in different directions.

Capacitor (3) and first impedance matching circuit (
4) are connected in parallel.

The input side is the same as the conventional one, with one end of the capacitor (8) and the second impedance matching circuit (dan) connected to the input end (7) connected to the signal source (6), and the other end connected to the high frequency transistor. Connect it to the base of (1) and use it as an input side circuit. The first and second impedance matching circuits (4
) is composed of a capacitor and an inductor, but the impedance of the signal source (6) and the load (described later) is 50Ω, and the base-emitter distance of about 1Ω and the collector-emitter impedance required to amplify the power of the high-frequency transistor (1). In order to convert the impedance between approximately 10Ω and 10Ω, the selection is made taking into account the frequency characteristics.

The input circuit includes a second impedance matching circuit (the other end of the high frequency transistor (1) and the inductor L) connected to the base of the high frequency transistor (1).
3 (6) are connected in parallel.

The output side circuit is a variable capacitance diode (sword).

A capacitor (3), an inductor L4 (7) and a first impedance matching circuit (illustrated) are connected in parallel to the collector of the high frequency transistor (1), and a capacitor C, (9
), the output end (9') and the load (10) are connected in series.

Two variable capacitance diodes are used between the collector and emitter of a high frequency transistor, and they are connected in series with different forward and reverse directions so that they act as the same capacitance for positive and negative high frequencies.

Inductors L, (6), L, and (7) operate as base and collector power supply, and in addition to selecting a value several times higher than the input/output impedance, L and (7) are connected to the Vcc power supply terminal (11). At the same time, inductor L3 (6)
Connected to the other end via the resistor R (43), and connected to the inductor L
A diode (44) is connected to the other end of (6) to form an amplifier circuit. This resistance R is connected to the power supply terminal Vcc (1
1) is a resistance for supplying base bias power, and a diode (44) is for stabilizing its potential. Also capacitor C
□ (8), C, and (9) are installed adjacent to the input end (7) and output end (9), which provides direct current isolation between the base and input end, collector and output end, and high frequency It is a capacitor that propagates components.

〔Effect of the invention〕

FIG. 2 shows the voltage dependence of the variable capacitance diode incorporated in this amplifier circuit. The capacity is this reverse voltage VR is 12
．． At 5V, it shows 6PF, and at 2.5V, it shows 25PF, and the sum of this variable capacitance diode and the capacitor C6(3)5PF connected in parallel to the collector of the high frequency transistor becomes 11PF at L2.5V, and 30PF at 2.5V.

By the way, the characteristics required for the amplifier circuit are: ■Output power cuff W or more 2 frequencies 160-174M) IZ, input power 150mW, collector voltage 12.5V, and ■
As for load stability, the frequency is 160-174MHz,
Input power 50~250mW, collector voltage O~12.
In addition to 5V, there is no oscillation in all combinations of load VSIIIRIO.

However, the amplifier circuit equipped with variable capacitance diodes did not cause oscillation even with all these combinations, and the load stability showed a value that satisfied the above-mentioned standards even when the output power was 8W.

[Brief explanation of drawings]

Fig. 1 is an equivalent circuit diagram of the amplifier circuit according to the present invention, Fig. 2 is a curve diagram showing the relationship between the capacitance on the vertical axis and the diode reverse voltage VR on the horizontal axis, and Fig. 3 is an equivalent circuit diagram of the conventional amplifier circuit. It is a circuit diagram. Agent Patent Attorney Inoue - Male 1st Figure → Jimel'2-1': aRfi Vl? Cv) 2nd
Figure 3

Claims (1)

[Claims] a high-frequency transistor; a first impedance matching circuit having one end as an input terminal and the other end connected to the base of the high-frequency transistor; at least two variable capacitance diodes connected to the collector of the high-frequency transistor; A high-frequency power source comprising: a capacitor and a second impedance matching circuit connected in parallel to the collector of a high-frequency transistor; a power supply terminal connected to the second impedance matching circuit; and a grounded emitter of the high-frequency transistor. Amplification circuit.