Wideband polyharmonic generator

FIELD: power engineering.

SUBSTANCE: wideband polyharmonic generator comprises an active element, an outlet circuit, which matches an active element with a load, and a wideband inlet circuit, at the same time parameters of the outlet circuit in the working band of frequencies from the set ratios.

EFFECT: increased efficiency in working frequency band.

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The invention relates to the field of radio and can be used in radio transmitting devices.

A common drawback of existing polyharmonically generators (PG) with high efficiency is a narrow band of operating frequencies. This disadvantage stems from the fact that in PG when the operating frequency tuning there is a change in impedance not only at the fundamental frequency, but also at the harmonics.

Known technical solution GHG containing the active element, to the output electrode of which is connected to the output circuit, the parameters which guarantee the coordination of the active element with the load, and between the output electrode and a common bus to provide a low impedance value at the 2nd harmonic when the generator is at the center frequency (T.Nojima, S.Nishiki, K.Chiba, High-efficiency quasimicrowave GaAs FET Power amplifier. El.Letters, 7-th May 1987, vol.23, N10, pp.512-513). Implementation of high-performance mode and the achievement of high efficiency in the generator it is possible in a relatively narrow band of frequencies equal to 3%.

Also known PG, running at an angle cutoff of the output current is close to 90°, containing the active element, to the output electrode of which is connected to the output circuit, the parameters which guarantee the coordination of the active element with the load, and between the output electrode and a common bus to provide a low impedance value at the 2nd harmonic and high Zn is an increase in the impedance at the 3rd harmonic when the generator is at the center frequency. This generator also has a narrow band of frequencies, comprising 5% (S.Toyoda, High Efficiency Amplifiers, JEEE MTT-S Digest, 1994, pp.253-256).

The closest to the technical nature of the claimed device is a broadband polyharmonically generator (patent for invention №2210175, H03B 11/10, publ. 10.08.2003, bull. No. 22). It contains an active element, is performed on the transistor to the output electrode of which is connected to the output circuit, which decides the active element with the load, and broadband input circuit connected to the base of the transistor, while under the influence of the input transistor generates pulses of collector current cutoff angle of 90°. Parameters in the output circuit in the operating frequency band selected from the following formulas:

$$\frac{\left|X_2\right|}{R_n}\le \mathrm{0,5};$$$$\frac{\left|X_3\right|}{R_n}\ge \mathrm{2,}$$

where |X₂| is the absolute value of the reactance at the 2nd harmonic of the Central frequency of the operating range;

|X₃| is the absolute value of the reactance at the 3rd harmonic Central is astate operating range;

R_nactive load resistance.

Construction of this generator in relative frequency, equal to 25%, has an output power of 5 watts minimum with a minimum efficiency of 73%. This solution has a relatively low value of efficiency.

The present invention aims to increase the efficiency of GHG in the band of operating frequencies. This is achieved by the fact that GHG containing the active element, to the output electrode of which is connected to the output circuit, which decides the active element with the load, and broadband input circuit connected to the input of the active element, while under the influence of the input signal active element generates a current pulse, the cutoff angle of the current pulses of the active element is within (100-110)°, and the output circuit in the operating frequency band provide between the output electrode of the active element and the common bus, the following relative values of the reactive impedance for harmonics:

$$\frac{\left|X_2\right|}{R_n}\ge 2;$$$$\frac{\left|X_3\right|}{R_n}\le \mathrm{1,}$$

where |X₂|, |X₃| is the absolute value of the reactance on the 2nd and 3rd harmonics, respectively;

R_nthe value of resistance of the load on the 1st harmonic between the output electrode of the active element and a common bus.

This choice of parameters output circuit creates favorable conditions for achievement in frequency high efficiency, exceeding the values of the efficiency of the prototype. This is due to the fact that in the proposed device the current pulses of the active element are simplified trapezoidal shape, and the shape of the output voltage of the active element is close to the cosine pulses. Such forms of voltage and current are stored in the working frequency band, which determines the possibility of obtaining high efficiency.

Figure 1 presents the scheme of PG, and figure 2 - frequency characteristics of GHGs.

The proposed GHG contains a broadband input circuit (1)connected to the input of the active element (2), the output of which is connected to the power source through the circuit junction (3) and is connected to the output circuit (4). Private form of implementation of the output circuit consisting of elements (5)-(15), is given in figure 1. Parameters output circuit is selected so that in the working bandwidth they provide coordination of the active element with the load on the 1st harmonic, and the 2-nd and 3-rd ha is monicah impedances between the output electrode of the active element and a common bus correspond to the above inequalities. PG works as follows. When the above-mentioned selection of the impedance in the operating frequency band creates the necessary conditions for obtaining such forms of voltage and current, which minimizes the time intervals when the voltage at the output electrode of the active element flows through the current. Thus, the amount of thermal energy dissipated by the active element on its resistance saturation during the oscillation period in the proposed device, much smaller than the prototype, with the same output power. This is due to the fact that the current pulses of the active element in the proposed device are simplified trapezoidal shape, while in the prototype of the current pulses similar in shape to the positive half-wave cosinusoid. In the proposed GHG polyharmonically mode with high efficiency is maintained in relative operating frequency band, amounting to at least 20%.

The proposed device has been tested in a specific design implementation. As the active element used MOS transistor MRF1517NT1, nominal values of the elements of the output circuit is given in figure 1. Frequency response (figure 2) show that the relative bandwidth of 20%, PG has an efficiency (76-79)%. Thus the average power is 6.5 W in non-uniformity in the band of the hour is 0.8 dB. A device built according to the characteristics of the prototype on the same transistor with the same average power in the same frequency band, has an efficiency of 70 to 73%.

Polyharmonically generator containing an active element, to the output electrode of which is connected to the output circuit, which decides the active element with the load, and broadband input circuit connected to the input of the active element, while under the influence of the input signal active element generates current pulses, characterized in that the cutoff angle of the current pulses of the active element is within (100-110)°, and the output circuit in the operating frequency band provide between the output electrode of the active element and the common bus, the following relative values of the reactive impedance at the harmonics

where |X₂|, |X₃| is the absolute value of the reactance on the 2nd and 3rd harmonics, respectively;
R_nthe value of resistance of the load on the 1st harmonic between the output electrode of the active element and a common bus.