JPS628604A - Broad band power amplifier - Google Patents

Abstract

PURPOSE:To avoid high frequency in a lower limit high frequency by adopting the constitution that a part of an RF signal is fed back at the lower limit only in the frequency band and a switching diode element is changed over by the signal. CONSTITUTION:A part of the RF signal appears at the anode of a detection diode 25 by setting in advance a series resonance circuit comprising an inductor element 23 and a capacitor 24 is resonated in a frequency fL when the RF signal having the lower limit frequency fL of the band is inputted, the signal is detected by a detection diode 25, a switching transistor (TR) 37 is turned on, a switching TR 42 is turned off, a pin diode element 49 is turned off and a pin diode element 55 is turned on. In setting a parallel resonance circuit (comprising an inductive element 48 and a capacitor 47) and a series resonance circuit (comprising an inductive element 53 and a capacitor 54) so as to be resonated in a frequency 2fL in advance, the basic frequency fL is outputted as a gain of an amplifier at an output receptacle 52 and the high frequency 2fL is absorbed in a resistive terminator 58.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an amplifier used in radio equipment and the like, and particularly to an amplifier that has a wide band, high output, and few harmonics.

[Conventional technology]

Conventionally, this type of amplifier has a wide required frequency band a of one octave or more and is required to have a higher output, so it has been difficult to remove many harmonics. For example, set the input of an amplifier to the lower limit of the required frequency σ.

shall be. ), the harmonic 2fL, which is a double of this frequency fL, is within the band of the amplifier, and it is difficult to remove this 2fL using a matching circuit, LPF, etc. It was necessary to select.

[Problem that the invention seeks to solve]

In this way, in conventional wideband amplifiers, the harmonics are determined by the selected transistor elements, and in order to develop an amplifier with extremely low harmonics, we must first start by selecting the transistor elements, which is very important. In addition, transistor elements that suppress harmonics as much as possible are generally expensive9, and amplifiers that use multiple stages of these elements require very expensive inputs. The score was M.

[Failure to solve the problem]

The broadband amplifier of the present invention has one series KL in the output stage of the amplifier.
Connect the C parallel resonant circuit, connect the LC series resonant circuit in parallel, and further connect the resistor and L in parallel (connect the 4-column resonant circuit and the detection diode in series, and insert this output signal into the voltage detection circuit. 2 signal output is obtained, and further depending on this output signal,
It is characterized by a structure in which pin diode elements are switched to switch between parallel and series resonant circuits.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

The figure is a circuit diagram of one embodiment of the present invention. 1 is an input connector, and 2 and 3 are preamplifiers. 4,12゜21.51 is a coupling capacitor, 5,13 is a current limiting resistor, 6,
8, 14 and 16 are voltage dividing resistors, 7.15 is a high frequency blocking capacitor, and 9.17 is a field effect transistor (
(hereinafter referred to as FET), io.

19 is a high frequency blocking capacitor, and 11.18 is a choke coil.

Next, 20, 32, 38 are power supply terminals, 46°5
6 is a coupling capacitor, 23.48.53 is a resonant inductor element, 24, 47.54 is a resonant capacitor, and To
Inductor element 23, capacitor 24, and inductor cable 53. The capacitor 54a and the a-row resonant circuit are connected to the inductor element 48 and the capacitor, and 47 is the parallel resonant circuit.
has been completed.

49.55 is a pin diode element for continuing the parallel resonant circuit of the inductor wire 48 and the capacitor 47 and the series resonant circuit of the inductor element 53 and the capacitor 54, and the resistor 50.57 is the pin diode element. The load resistor 58 is a non-reflective terminator. Terminal 52 is an output connector ◎ Also, resistor 22 is for inputting a part of the F signal output from PE'r 17 to detection diode element 25, and resistor 26 is a resistor for dividing 11 signals. It is. 28
is a negative fr resistance of the detection diode element 25, and 27 is a high frequency blocking capacitor.

Next, the variable resistance element 29 is for setting the DC signal rectified by the detection diode 25 to a predetermined value, the resistors 30, 36, and 40 are for current limiting, and 31 is an operational amplifier; Resistors 33 and 34 are used to determine the gain of this operational amplifier 31, 35 is a constant voltage diode, 39 and 43 are resistors, 37 and 42 are switching transistors, and 41 is generated by the resistor 40 and the base-emitter capacitance of the switching transistor 42. It is a speed-up capacitor that corrects the time constant, and the resistor 44.59 is for current limiting, and the resistor 45
．． 60 is a high frequency blocking capacitor.

In such a circuit, when an RP multiplied signal is input to the input plug 1, it is amplified by the RF multiplied signal preamplifiers 2 and 3, and further amplified by the PET 9.17, and the high power is
It is taken out from the output connector 52. Now, suppose that the band of these amplifiers is designed to be one octave, the lower limit frequency is fL, the upper limit frequency is fHs, the center frequency is fc, and the frequency fL
If an RF multiplied signal with , is input to input connector 1,
The harmonic 2fL of frequency 9 included in this RF multiplied signal is at the upper limit of the band of the amplifier, and it is difficult to remove it. The purpose of the present invention is to remove the above-mentioned harmonics to a desired value. , inductor element 23. capacitor 2
If the series resonant circuit with 4 is set in advance to resonate at the frequency fL, a part of the above RF multiplied signal will appear at the anode measurement of the detection diode 25, and will be detected by the detection diode 25 and converted into a DC signal. becomes. This DC signal is divided into desired values by the variable resistance element 29 and input to the operational amplifier 31 via the resistor 3o. Now, this variable resistance element 2
9. If the resistors 33 and 34 are adjusted so that the output voltage of the operational amplifier 31 is equal to or higher than a predetermined voltage (the combination of the Zener voltage of the constant voltage diode 35 and the base-emitter voltage of the transistor 36), the switching transistor 37 is ON.

The switching transistor 42 is turned off, the pin diode element 49 is turned off, and the pin diode element 5 is turned off.
5 is turned on, and the parallel resonant circuit (inductor element 4
8. If the capacitor 47) and the series resonant circuit (inductor element 53 and capacitor 54) are set to resonate at a frequency of 2fL, the parallel resonant circuit will have the following equation at the input frequency fL:
In the passband and harmonic 2fL, it has an infinite impedance, resulting in a 1g cutoff. Conversely, at the input frequency afL, the series resonant circuit has high impedance and becomes a cutoff region, and at the harmonic 2fL it has an infinitesimal impedance and becomes a passband. In this way, when an RF flaw signal with frequency fLt- appears at input plug 1, the fundamental frequency is
It is output to the output connector 52 with the gain of the amplifier unchanged, and the high frequency 2fL is absorbed by the non-reflection terminator 58.

Next, when the input frequency is gradually increased, the impedance of the series resonant circuit (inductor cord 23, capacitor 24) increases, the DC signal from the detection diode 25 decreases, and the output of the operational term l1li unit 31 increases. The voltage drops,
The constant voltage diode 35 is cut off, the switching transistor 37 is turned off, the switching transistor 42 is turned on, the pin diode element 49 is turned on, the pin diode element 55 is turned off, and the input f
Frequencies from f to f, which are higher than L, are outputted to the output connector 52 through the pin diode cable 49 without loss. Of course, by changing the Q of the series resonant circuit (I/ductor element 23, capacitor 24) and the variable resistance cable 29, the threshold frequency f1. xt- It goes without saying that it can be set freely.

〔Effect of the invention〕

As explained above, the present invention is configured such that a part of the RF flaw signal can be fed back only at the lower limit of the frequency band of the amplifier, and the switching diode wire can be switched depending on this signal. Since frequency harmonics can be removed and no external signals are required, it is easy to design peripheral equipment, and there is no need to use expensive transistors, making it possible to manufacture inexpensive amplifiers.

[Brief explanation of the drawing]

The figure is a circuit diagram of an embodiment of the present invention. l...Input connector, 2,3...Preamplifier, 9゜17...Field effect transistor, 25
...Detection diode, 31...Operation amplifier, 37,42'-...Switching transistor, 49,55...Pin diode, 52.
...Output connector, 58...Non-reflection terminator.

Claims (1)

[Claims] A power amplification circuit that converts a small amount of power into a high output, a circuit in which a pin diode is connected in series to its output stage, an LC parallel resonant circuit is connected in parallel to the pin diode, and an LC parallel resonant circuit is connected in parallel to the input side of the pin diode. A circuit in which a series resonant circuit, a pin diode, and a terminating resistor are connected, a resistor in parallel to the input side of the pin diode, and an LC series resonant circuit are connected in series, and a detection circuit and a voltage detection circuit are connected to the output side of the circuit. , a wideband power amplifier characterized in that the output is applied to each of the two pin diodes individually.