WO2008152579A1

WO2008152579A1 - System to increase the efficiency of an amplifier and the amplifier so obtained

Info

Publication number: WO2008152579A1
Application number: PCT/IB2008/052286
Authority: WO
Inventors: Antonio Sebastiano Abbadessa
Original assignee: Antonio Sebastiano Abbadessa
Priority date: 2007-06-13
Filing date: 2008-06-10
Publication date: 2008-12-18
Also published as: ITPI20070073A1

Abstract

System to improve the efficiency of an amplifier that comprises the application to an existing amplifier of a number of electronic devices that increase the efficiency. In particular it comprises the insertion of a Lin inductance (6) placed at the input of the active component (1). An electrolytic condenser ClA (12) and a diode DlA (11) result to be both inserted between the pole of the Lin inductance (6) not connected to the active element and. the earth. Equally, a C2A electrolytic condenser (15) and a D2A diode (14), both inserted between the connection point of said Lout inductance (7) and the polarization circuits (4), and the earth. A D4A (16) diode is then inserted between the connection point of the polarization circuits (4) to the power supply (8), or to the lead through capacitor, and the earth. A D3A diode (13) is inserted at the polarization circuit's downstream (4), before its connection with said Lin inductance (6) and the zener diode D5A (17) is inserted in parallel to said D4A diode (16).

Description

TITLE

SYSTEM TO INCREASE THE EFFICIENCY OF AN AMPLIFIER AND AN AMPLIFIER SO OBTAINED

Technical Field

The present invention refers to the technical field relative to the electronic devices for telecommunications and in particular it refers to an innovative type of radio-frequency amplifiers.

State of the Art

The equipments for the transmission and the reception of television signals use radio-frequency amplifiers, or rather devices that allow to increase the capacity of the signal transmitted or received with frequency of this signal comprised between 40 and 860 Mhz . With such signals, commonly called VHF-UHF band frequency, we work in class A (ultra linear) , where the gain and the output capacity are notably reduced. These amplifiers are mainly characterized from the gain and passband factors, or rather the ratio between the input capacity and the output capacity expressed in decibel, and the frequency spacing within which such gain does not step down a certain value. Other features of such amplifiers, as for example the noise figure, supply a measure of the unavoidable alteration of the signal that comes with the amplification .

For all the amplifiers the gain, besides depending from the features of the active elements used and in part from the quality of the input signal applied, it is strictly depending from the passing bandwidth. If it is requested, thus, that the amplifier works on a wider frequency band, corresponding for example to a greater number of tv channels, then a lower gain shall be accepted and vice versa .

The band, the gain and the fidelity signal amplified respect to the incoming one depend, beyond from the active elements used, on the scheme of the amplificatory, and in particular from some components that have the function of filtering and stabilizing the signals inside the circuit. In particular, the output signal with higher capacity, respect to the input signal, is obtained thanks to the capacity supplied by means of the input. Obviously only a part of the capacity supplied by the input is given the to output signal, while great part of it is loss of heat. The efficiency (percentage ratio between the capacity of the output signal and the capacity supplied by the input) of the canalised TV amplifiers found in the market, used in the TV repeaters as capacity terminals, is of 25-30%. Disclosure of invention-

Thus, it is the aim of the present invention to supply a particular circuit layout that allows to improve the efficiency of this kind of amplifiers (also for frequencies different from the VHF-UHF band and for different applications as for example radio, telephony, data transmission, etc.) respect to what is found today in the market, increasing considerably the output capacity on equal capacity consumption.

It is also the aim of the present invention to supply a circuit layout where the gain remains unchanged despite the increase of capacity, but the amplifier can accept in input a higher signal with a resulting higher level of output.

These and other aims are obtained through the present system to improve the efficiency of an amplifier which electronic diagram comprises:

^■ at least an active element (1) ;

^■ polarization circuits (4) of the active element connected to the output and/or to the input of the active element (1) ;

^■ At least a Lout inductance connection (7) between the output point of the signal of the active element (1) and the polarization circuit (4) ; ■ At least a power supply (8); and characterized by the fact that it comprises at least the following components: a Lin inductance (6) inserted on the input of the active element (1) ; - an electrolytic condenser ClA (12) and a DlA diode

(11) both inserted between the pole of the Lin inductance (6) not connected to the active element and earth. an C2A electrolytic condenser (15) and a D2A diode (14), both inserted between the connection point of said Lout inductance (7) and the polarization circuits (4), and the earth; a D4A (16) diode inserted between the connection point of the polarization circuits (4) to the power supply (8), or to the lead through capacitor, and the earth; a D3A diode (13) , inserted at the polarization circuit's downstream (4), before its connection with said Lin inductance (6); - a Zener diode D5A (17), inserted in parallel to said D4A diode (16) .

Advantageously the added electrolytic condenser ClA (12) is dimensioned according to the ratio The capacity in micro-farad equals to the output capacity of the amplifier before the amendment expressed in watt multiplied to a value greater or equal to 4 and compatible voltage rating.

Moreover also the electrolytic condenser C2A (15) is dimensioned according to the relation (function???): The capacity in micro-farad equals to the output capacity of the amplifier before the amendment expressed in watt multiplied to a value greater or equal to 5 and compatible voltage rating.

Advantageously the diodes DlA (11), D2A (14) and D3A (13) are components with features adequate to the voltage and current values found in the circuit. Moreover the zener diode D5A (17) is calculated in a way to guarantee a voltage equal to the input voltage of the amplifier. Advantageously the present system comprises also the following components: One or more ceramic capacitors with capacity between few nanofarad and one hundred or so nanofarad (19) (20), inserted in parallel to ClA (12) . - One or more ceramic capacitors with capacity between few nanofarad and one hundred or so nanofarad (21) (22), inserted in parallel to C2A (15) .

Advantageously the active component is a transistor Bjt with common emitter, for which the base constitutes the input of the signal and the output collector, or the active component is a transistor with common source field-effect, for which the Gate constitutes the input of the signal and the Drain the output. The active component can also be an integrated circuit with the input and output pins used as already said, or the active component could be a cathode tube where the input and output correspond to the control electrode and to the anode. Advantageously the system comprises: an Hf chocke LlA inductance (5) inserted between the Lin inductance (6) and the diode D3A (13), with a value that is greater or equal respect to Lin; - an electrolytic condenser (27) with capacity equal to 40% of said ClA capacity (12), and a ceramic condenser (28), preferably a disc type, both said condensers inserted between the pole of connection of D3A to the new inductance LlA and the earth. Advantageously the active component is a transistor polarized through circuits that comprise a second active component (40) and the system comprises also a diode (42) inserted between the collector of the transistor (40) of the polarization circuit and the earth. Moreover an electrolytic condenser (41) is inserted between the base of the transistor of the polarization circuit (40) and the earth and eventually a resistor (23) is inserted between the inductance (5) and the ceramic condenser (20) .

An amplifier congruent to the present invention is realized according to the scheme of fig. 6, or according to the scheme of fig. 7 or according to the scheme of fig. 9.

Brief description of drawings

Further features and advantages of this system to improve the efficiency of an amplifier, according to the invention, will be clearer with the description of one of its pattern realization that follows, made to illustrate but not limit, with reference to the annexed drawings, in which: Fig. 1 shows a block diagram of the devices to which the invention is applicable.

Fig. 2, fig. 3 and fig. 4 show layout example of devices to which the invention is applicable.

Fig. 5 and fig.6 show the block diagrams of devices modified according to the invention. fig.6, fig. 7 and fig. 9 show layout example of devices to which the invention is applicable.

The fig. 10 show a graphic representation of the advantage obtained through the invention.

Description of a preferred pattern realization The system is based on the principle of filtering and stabilization of the voltages and currents supply- given to the active component that amplifies the signal (for example a transistor) , and through input and output polarization circuit, giving much attention to the input circuits. This is obtained through a number of diodes and reactive elements inserted in some strategic points of the circuit, being the reactive elements dimensioned according to specific relations, this because of the usage of a great power supply.

The undertaken system, object of the invention, applies to RF amplifiers that can be represented according to the described scheme in figure 1. In particular, in the circuit scheme of an RF amplifier (10) there can be distinguished:

- an active element (1) ;

- a stage of the circuit 2 used for the conditioning and filtering of the input signal and adaptation of the input impedance; - a section of the circuit used for the conditioning and filtering of the input signal and adaptation of the output impedance 3;

- Circuit of polarization of the active component 4, placed between the input of the active component and the earth.

Alternatively there are solutions where the polarization circuits are placed between the input of the active component and the alimentation 8, and connected to the input of the active component though an inductance 6 (look at figure 1) . In other cases, moreover, the polarization circuit of the active component are placed between its output and the power supply, connected to said output also in this case through an inductance 7. Most RF amplifiers are designed according to this kind of scheme, except few cases where it is not present one or both the circuits of conditioning and adapting of the signal (2 and 3) or the connection of the input of the active component to the polarization circuit.

The active component can be in the different cases a bipolar transistor, a Mosfet, an integrated circuit, or a cathode tube. According to the prior art, the results with the Mosfet are lower, but some improving are obtained when the amplifiers, which are usually transistor, that conduct them are supplied with them.

In the case the active component is a bipolar transistor, the input and output are respectively intended as the base and the collector. On the other hand, in the case the active component is a Mosfet,^' the input and the output are respectively intended as the gate and the drain, while in the case of the cathode tube the input and the output correspond to the control electrode and to the anode. The polarization circuits can in turn comprise active components with the function of stabilizer and regulator of the current and voltage of power supply. Typical amplifier of the described type are represented in fig. 2, 3 and 4. The first circuit 30 is relative to an RF transistor amplifier (VHF-UHF amplifier, and output capacity lower or equal to IW) that uses a very common transistor in class A with commercial denomination BFQ68.

The second circuit 31 is similar to the preceding, but in a more complete and powerful version. It uses the transistor TPV598 (UHF band, with capacity in output 5W in canalised version) , and the polarization circuit comprises a second active component.

The third circuit 32 is relative to an RF amplifier, a MMIC (UHF band) that uses the integrated circuit with commercial denomination MSA 0886.

The amplifier 31 for example, supplies in output a capacity of 5W against an absorbed capacity of 24W, thus an efficiency of about 21%. The increasing system of the efficiency, according to the present invention, consists in inserting on the scheme 10 of fig. 1 a set of discrete elements dimensioned according to precise relations (look at figure 5) . The presence of the Lin inductor (6) in the circuit is fundamental. In case an amplifier comprises in this position a resistance, it must be pre-emptively substituted with an inductance in order to correctly apply the modification. An amplifier that can be represented according to the proposed scheme 10 can therefore be modified according to the invention, and the amplifier so obtained responds to scheme 100 described in figure 5.

Practically the invention comprises the insertion in the circuit, in case not present, of a Lin inductance (6) on the input of the active element. Moreover, an electrolytic condenser ClA (12) and a diode DlA (11) are inserted on the terminal of the Lin inductance (6) not connected to the input of the active component. The positive pole of the diode and the plate of the condenser are connected to the earth.

The condenser 12 has a capacity expressed in microfarad, equal to the capacity of the amplifier before the modification and expressed in watt, multiplied by 100, with a 20% tolerance and working voltage equal or greater than 25 Volt. With this dimensioning the best performance is obtained, but the advantages start from the 10% of the calculated value. The condenser that sometimes is found on some amplifiers, for example C9 in the circuit (35), varies from 4,7 to 10 microfarad and it's needed to eliminate the added sound from the polarizing circuit, with the output capacity that remains equal at 5W.

An electrolytic condenser C2A (15) and a diode D2A (14) are inserted on the terminal of the Lout inductance (7) not connected to the output of the active component. The positive pole of the diode and the plate of the condenser are connected to the earth. The condenser 15 has a capacity expressed in microfarad, equal to one-fifth of the capacity of the amplifier before the modification and expressed in watt, multiplied by 100, with a 20% tolerance.

In case there are polarizing circuits 4 on the input of the active component, a diode D3A (13) is inserted downstream of this circuit, before its connection to the Lin 6. The positive pole of the diode is connected to the polarization circuit 4. A diode D4A (16) is inserted on the connection to the power supply 8, eventually between the passing condenser 18 and the polarizing circuits 4, with the positive pole of the diode connected to earth. Other components could also be added to have a further improvement, but they do not result fundamental for a greater efficiency.

For this aim, as always described in figure 5, a protection diode Zener D5A (17) is inserted on the connection to the power supply 8, in parallel to the diode 16. In case they are not present, two ceramic condensers 19 and 20 with a small capacity (nanofarad) , are inserted in parallel to the electrolytic condenser 12. Moreover two ceramic condenser 21 and 22 still with a small capacity (nanofarad) , are inserted in parallel to the electrolytic condenser 15.

Practical example of modified amplifier according to what has been described, are represented in fig.6 and fig. 7. The undertaken amplifiers 33 and 34 are the ones described before.

In the case of a more complex amplifier, with an active component also inside the polarizing circuit 40, there can be inserted further components, still not fundamental for the improvement, but helpful for a well functioning. With reference to the circuit 101 in fig. 8 these components are:

- a second inductance 5 of greater or equal value to Lin (6) inserted in series to Lin, between this and the diode of connection to the polarization circuit 13. - In case not present, a resistor 23 inserted between the inductance 5 and the ceramic condenser 20. - an electrolytic condenser 27 and a ceramic condenser 28 inserted on the connection between said second inductance 5 and the diode D3A (13) , and connected to earth. - an electrolytic condenser 41 inserted on the base of the active component of the polarization circuit, the plate of the condenser is connected to earth.

- a diode 42 inserted on the collector of the active component of the polarization circuit. the positive pole of the diode connected to earth. the amplifier 35 in figure 9 represents a practical example of what has been described. With reference to this last circuit 35, the features of the active component, in detail the transistor denominated TPV598, given by the constructor are the following:

- IV - V band (470 - 860 MHz)

- VCE= 25V, Ic= 850 mA

- gain min. 7.0 dB in class A , f= 860 MHz

- P out=4.0W, f= 860 MHz. - Absorbed capacity = VCE x IC = 25 x 850= 21250 mW (21,25 W)

- given capacity= 4000 mW (4W)

- Efficiency = 100 x 4000 / 21250 = 18,82%

Taking into account the real values of a canalised amplifier among the best in the market, where usually is used a power supply with +24V output, with the presence of the resistance on the collector (Rc) we have a VCE of about 21V and an Ic of about IA. Using directly the +24V of the power supply for the calculation we have:

- Output level in dBμV 146 (+37,2dBm) - Absorbed capacity = 24 x 1000= 24000 mW (24 W)

- given capacity= 5000 mW (5W)

- Efficiency ratio = 100 x 5000 / 24000 = 20,83

With some more modern transistors that have particular features and supported by great electronic circuits it is closely reached to 25-28%.

In the case of the circuit modified according to the invention, on the other hand is obtained:

- Output level in dBμV >= 150 (>= +41,2dBm) - Absorbed capacity = VCE x IC = 24 x 1000= 24000 mW (24 W)

- given capacity= 13300 mW (13,3 W)

- Efficiency = 100 x 13300 / 24000 = 55,42 %

The graphic 102 in fig. 10 shows graphically the increase of the obtained efficiency.

(The measures of the output level in dBμV, have been made with the field meter ROVERSAT HP4-TS with the addition of an external attenuator of 10 dB) .

In the undertaken circuit 35 are used the following components:

- DlA, is used as a filter, being not passed by current, it is sufficient the diode BYV10-40 or an equivalent diode.

- D2A, for capacity that reach the 15W is equal to DlA, while for higher capacities it is better to use the 1N5061 or an equivalent diode.

- D3A is sufficient the BYV10-40 with capacity until 2OW, if the capacity is higher then it is used a diode 2A 1000V, for different values it is proportioned to the other components of the circuit . - D4A it is used with a double function, beyond discharging to earth the eventual negative component, it is used against the polarity switching, indeed if that would happen it would put the power supply into short circuit saving the amplifier, for this reason it is better a diode with amperage at least equal to the amplifier, in this case it is a BY399.

- D5A is a zener, also in this case beyond controlling the value of the voltage, if there is an anomalous increase, it would go into short circuit protecting this way the amplifier, its value in V should be equal to the power supply voltage and the capacity proportioned to the one of the absorption of the amplifier.

- D6A is used as a filter, same type of the DlA and D2A the BYV10-40.

- ClA: the value of this electrolytic condenser is given, as already mentioned, with reference to the output capacity of the transistor in Watt before the modification, in this ca 5W. The needed condenser is the 470μF 25V, the working voltage shouldn't be less than 25V otherwise a greater capacity is needed. - C2A electrolytic condenser, its value is about 1/5 respect to ClA, in this case it is obtained lOOμF with working voltage of 50V or 63V.

- C3A, if the same value of ClA is used then it seems there is a balance, but it is sufficient a capacity of 40% respect to the first one. - C4A is a ceramic condenser of InF preferably a disk one.

- C5A is an electrolytic filter condenser, it improves the features of the controlling transistor Q2.

- LlA inductance (HF choke) with a value equal or greater than L2A.

Logically there can be used also smd components.

Claims

1. System to improve the efficiency of an amplifier which electronic diagram comprises: " at least an active element (1);

^■ polarization circuits (4) of the active element connected to the output and/or to the input of the active element (1);

^■ At least a Lout inductance connection (7) between the output point of the signal of the active element (1) and the polarization circuit (4 ) ;

^■ At least a power supply (8); characterized by the fact that it comprises at least the following components: a Lin inductance (6) inserted on the input of the active element (1) ; an electrolytic condenser ClA (12) and a DlA diode (11) both inserted between the pole of the Lin inductance (6) not connected to the active element and earth. an C2A electrolytic condenser (15) and a D2A diode (14), both inserted between the connection point of said Lout inductance (7) and the polarization circuits (4), and the earth; a D4A (16) diode inserted between the connection point of the polarization circuits (4) to the power supply (8), or to the lead through capacitor, and the earth; a D3A diode (13), inserted at the polarization circuit's downstream (4), before its connection with said Lin inductance (6); a Zener diode D5A (17), inserted in parallel to said D4A diode (16) .

2. System to improve the efficiency of an amplifier according to the previous claim characterized by the fact that the added electrolytic condenser ClA (12) is dimensioned according to the ratio: The capacity in micro-farad equals to the output capacity of the amplifier before the amendment expressed in watt multiplied to a value greater or equal to 4 and compatible voltage rating.

3. System to improve the efficiency of an amplifier according to the previous claims characterized by the fact that the added electrolytic condenser C2A (15) is dimensioned according to the ratio: The capacity in micro-farad equals to the output capacity of the amplifier before the amendment expressed in watt multiplied to a value greater or equal to 5 and compatible voltage rating.

4. System to improve the efficiency of an amplifier according to the previous claims characterized by the fact that the diodes DlA (11), D2A (14) and D3A (13) are components with features adequate to the values of voltage and current found in the circuit.

5. System to improve the efficiency of an amplifier according to the previous claims characterized by the fact that said zener diode D5A (17) is dimensioned in a way to guarantee a voltage equal to the voltage of the power supply of the amplifier.

6. System to improve the efficiency of an amplifier according to the previous claims characterized by the fact that it comprises the following components:

- One or more ceramic capacitors with capacity between few nanofarad and one hundred or so nanofarad (19) (20), inserted in parallel to ClA (12) .

- One or more ceramic capacitors with capacity between few nanofarad and one hundred or so nanofarad (21) (22), inserted in parallel to C2A (15) .

7. System to improve the efficiency of an amplifier according to one or more of the previous claims characterized by the fact that the active component is a Bjt transistor with a common emitter, for which the base constitutes the input of the signal and the collector the output.

8. System to improve the efficiency of an amplifier according to one or more of the previous claims characterized by the fact that the active component is a transistor with common source field-effect, for which the Gate constitutes the input of the signal and the Drain the output.

9. System to improve the efficiency of an amplifier according to one or more of the previous claims characterized by the fact that the active component is an integrated circuit with the input and output pins used in the provided manner.

10. System to improve the efficiency of an amplifier according to one or more of the previous claims characterized by the fact that the active component is an integrated circuit with the input and output pins used in the provided manner.

11. System to improve the efficiency of an amplifier according to one or more of the previous claims characterized by the fact that it comprises: an Hf chocke LlA inductance (5) inserted between the Lin inductance (6) and the diode D3A (13), with a value that is greater or equal respect said Lin inductance; - an electrolytic condenser (27) with capacity equal to 40% of said ClA capacity (12), and a ceramic condenser (28), preferably a disc type, both said condensers inserted between the pole of connection of D3A to the new inductance LlA and the earth.

12. System to improve the efficiency of an amplifier according to one or more of the previous claims characterized by the fact that the active component is a transistor polarized through circuits that comprise a second active component (40) .

13. System to improve the efficiency of an amplifier according to one or more of the previous claims characterized by the fact that the system comprises also a diode (42) inserted between the collector of the transistor (40) of the polarization circuit and the earth.

14. System to improve the efficiency of an amplifier according to claim 13 and 14 characterized by the fact that the system comprises also an electrolytic condenser (41) inserted between the base of the transistor of the polarization circuit (40) and the earth and eventually a resistor (23) inserted between the inductance (5) and the ceramic condenser (20)

15. Amplifier according to one or more of the previous claims characterized by the fact that it is realized according to scheme of fig. 6

16. Amplifier according to one or more of the previous claims characterized by the fact that it is realized according to scheme of fig. 7

17. Amplifier according to one or more of the previous claims characterized by the fact that it is realized according to scheme of fig. 9