JP3105846B2 - Broadband power amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wide band power amplifier, and more particularly to a wide band power amplifier for amplifying a radio frequency band (RF) high frequency signal.

[0002]

2. Description of the Related Art Conventionally, this kind of amplifier is used in a high frequency band of an RF band, and a required frequency band is as wide as one octave or more and high output is required. In particular, if the output-side impedance and load-side impedance are not sufficiently matched, the efficiency will deteriorate, the oscillation stability will decrease due to the reflected power of the high-frequency output signal, or if the lower-limit frequency is close to the upper-limit frequency, the harmonic will increase. Problems such as an increase in waves occur.

For this purpose, an output matching circuit is provided to match the output impedance with the load impedance. FIG. 1 shows an example of this type of amplifier. FIG. 1 is a block diagram showing a conventional example.

In FIG. 1, an input matching circuit 1 for impedance matching with an input side, an amplifying circuit 2 using a plurality of transistors, and impedance conversion of an output stage of the amplifying circuit 2 are performed to match with a load side impedance. An output matching circuit 7 is provided. The output matching circuit 7 includes fixed capacitors 71 and 73 for matching, a strip line 72 having a distributed constant, a semi-fixed capacitor 75 for matching, and a transformer 76 for an output transformer.

In this configuration, an input RF signal is input from an IN terminal.
The signal is impedance-converted by the input matching circuit 1 and input to the amplifier circuit 2. The amplifying circuit 2 includes a preamplifier and a power amplifier, and amplifies an input RF signal to a predetermined power level. Next, after the output matching circuit 3 performs impedance conversion, the output RF signal whose power has been amplified is output from the OUT terminal to the load side.

Here, it is difficult for the output matching circuit 3 to cover and match the output impedance of the power amplification stage of the amplifier circuit 2 over the entire frequency band. It is divided into three bands, a band B of a wave number band and a band C of a high frequency band, and the semi-fixed capacitor 75 is changed to an optimum constant for each band to cope therewith. When it is difficult to change the constant of the capacitor 75, or when there is no time to change the constant, an amplifier having a different capacitor constant for each divided frequency band is prepared and switched. .

[0007]

As described above, in the conventional example, the constant of the capacitor 75 differs depending on the bands A, B, and C obtained by dividing the entire frequency band.
It is necessary to select the bands A, B, and C according to the band used by the F signal. When it is desired to change the bands of A, B, and C, it is necessary to change the capacitor 75, and there is a problem that it takes time to change the capacitor mounted inside.

Normally, the entire frequency band is not used at the same time, and the used band is selected from the bands A, B and C.
This use band is often determined at the site of use, and it is particularly difficult to perform this change operation at the site of use. Alternatively, three amplifiers of bands A, B, and C may be arranged and switched in advance, but there is a problem that three amplifiers must be prepared.

[0009]

A wideband power amplifier according to the present invention divides the entire frequency band of an input RF signal into a plurality of bands by dividing some component constants of an output matching circuit for matching with a load side impedance. In the band division type broadband power amplifier corresponding to a wide band by changing for each divided frequency band, the change of the component constant is automatically changed by turning on and off the connection of the corresponding component by a switching signal from the outside. I have.

[0010] Further, a switching signal generation circuit for detecting the frequency of the input RF signal, identifying the corresponding divided frequency band, and automatically generating the switching signal may be provided.

[0011] Further, a display unit for displaying the divided frequency band used by the cutoff band switching signal may be provided.

Further, a pin diode may be used as the switching element for turning on / off the connection of the components.

[0013]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram of a band switching signal generation circuit of FIG.

In FIG. 1, an input matching circuit 1 for impedance matching with an input side, an amplifier circuit 2 using a plurality of transistors, and an output matching circuit 3 for performing impedance conversion and matching with a load side impedance.
And a band switching signal generating circuit 5 for generating a band switching signal.
And a band display section 6 for displaying the switched band.

The output matching circuit 3 includes fixed capacitors 31 and 36 for matching, a microstrip line 32 having a distributed constant, a capacitor 35 used for band C for matching, and a capacitor 33 added for band B for matching. And a capacitor 34 to be added at the time of band A
And pin diodes 37 and 38 for band switching elements, resistors 42 and 43 for increasing the impedance of the band switching signal line, coils 40 and 41, and a transformer 39 of an output transformer. .

In this configuration, the input R from the IN terminal
The F signal is impedance-converted by the input matching circuit 1 and input to the amplifier circuit 2. The amplifying circuit 2 includes a preamplifier and a power amplifier, and amplifies an input RF signal to a predetermined power level. Next, an output RF signal whose impedance has been converted by the output matching circuit 3 and whose power has been amplified is output from the OUT terminal.

As described with reference to FIG. 1, it is difficult for the output matching circuit 3 of the present amplifier to cover all frequency bands with the same constant and perform matching.
And the optimal constants are set for each.

That is, in the output matching circuit 3, only the capacitor 35 is used for the high frequency band C,
In the case of the band B of the intermediate frequency band, the capacitor 33 is added in parallel to the capacitor 35, and in the case of the band A of the low frequency band, the capacitor 34 is added to the capacitor 35. This switching is performed by the pin diodes 37 and 38. For example, when the band switching signal 102a is output from the band switching signal generation circuit 5, a direct current flows through the pin diode 38 via the resistor 42 and the coil 41, and the high-frequency impedance of the pin diode 38 decreases and the capacitor 34
Are connected in parallel to the capacitor 35.

The band switching signal generation circuit 5 receives a part of the output signal of the amplification circuit 2 and detects the frequency to identify which of the bands A, B and C the input RF signal belongs to. The switching signals 102a and 102b are output. However, in the case of band C, no band switching signal is output. That is,
Switching between the bands A, B, and C is automatically performed according to the frequency of the input RF signal. Also, the band switching signal 102a,
102b is input to the band display unit 6 at the same time, and turns on LEDs for displaying the switched bands.

Next, referring to FIG.
Will be described. In FIG. 2, frequency detectors 51a and 51 which receive an output signal 101 of an amplifier circuit 2 and detect center frequencies of bands A, B and C, respectively.
b, 51c and a level detector 5 for removing noise
2a, 52b, and 52c, and latch circuits 53a and 53b that latch each detection signal and output continuous DC switching signals 102a and 102b.

When there is no input of output signal 101, band switching signal 102 is not output. Therefore, in this state, the output matching circuit 3 and the band display section 6 are in the switching state of the band C. This state does not change when the frequency of the band C is detected. When the frequency of band B or A is detected from output signal 101, band switching signal 102a
Alternatively, 102b is output.
Are reset by another band switching signal, so that the last band switching signal remains. That is, for example, if the frequency of the band B is detected in the state of the band C, the band switching signal 102a of the band B is output immediately.

When it is not necessary to frequently switch the band, the band switching generation circuit 5 is unnecessary, and a manual switch may be provided instead, and the band switching signal 102 may be directly transmitted from this switch. .

[0023]

As described above, the wide-band power amplifier of the present invention does not need to prepare an amplifier for each divided band, and is particularly advantageous in that it is small, light, and inexpensive. Further, since the switching of each of the divided bands is performed automatically, there is an effect that the trouble of the band switching can be simplified. In particular, since the frequency of the input RF signal is detected and the band is automatically switched based on the detection result, the frequency can be used without being conscious of the frequency of the input RF signal.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of a band switching signal generation circuit in FIG. 1;

FIG. 3 is a block diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input matching circuit 2 Amplifying circuit 3 Output matching circuit 31, 33, 34, 35, 36 Capacitor 32 Stripline 37, 38 pin diode 39 Transformer 40, 41 Coil 42, 43 Resistor 5 Band switching signal generation circuit 6 Band display 51a, 51b, 51c Frequency detector 52a, 52b, 52c Level detector 53a, 53b Latch circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03F 1/42-1/56 H03F 3/189 H03F 3/60

Claims (4)

(57) [Claims] 1. A part of a part of an output matching circuit for matching with a load side impedance is changed for each divided frequency band obtained by dividing the entire frequency band of an input RF signal into a plurality of bands. In the above-mentioned band-divided broadband power amplifier, the change of the component constant is automatically changed by turning on / off the connection of the corresponding component by a switching signal from the outside. 2. The wide band power according to claim 1, further comprising a switching signal generation circuit that detects a frequency of the input RF signal, identifies the corresponding divided frequency band, and automatically generates the switching signal. amplifier. 3. The wide-band power amplifier according to claim 1, further comprising a display unit that displays the divided frequency band used by the switching signal. 4. The wide-band power amplifier according to claim 1, wherein the switching element for turning on / off the connection of the component uses a pin diode.