RU2685387C1 - Tunable harmonics self-oscillator - Google Patents

Abstract

FIELD: radio equipment.SUBSTANCE: invention relates to radio engineering and can be used in various receiving-transmitting radio equipment. Tunable harmonics self-oscillator is made on bipolar transistor connected by common base circuit. In the generator there used are in-series connected inductances 19, 20, 21, 22 and capacitors 23, 24, 26, 25, accordingly. Second plates of capacitors are connected to the bus, and common points of each pair of elements are connected to terminals of supply sources of supply voltages to electrodes of transistor 34 and control of varicap 39. Device comprises three circuits: emitter, basic and collector. Emitter circuit includes parallel connection of inductance 20 and total capacitance of in-series connected varicap and capacitor 35. Basic circuit includes inductance 40 and capacitors 36, 37. Collector circuit includes series-connected inductance 41 and capacitor 38. Collector circuit is connected to 50-ohm output through capacitor 29.EFFECT: technical result consists in improvement of power level of the selected harmonics of tunable generators relative to output power of oscillations of their main frequency.1 cl, 10 dwg

Description

The proposed device relates to the field of radio engineering and can be used in various receiving and transmitting radio equipment operating up to the microwave range. In particular, this device relates to voltage-controlled microwave oscillators (VCOs), which simultaneously form oscillations of the fundamental frequency and frequency of the kth harmonic and are intended for operation in modern frequency synthesizers.

The microwave oscillator oscillator is known (See Malyshev, VA Microwave harmonic oscillator / V.A. Malyshev, S.P. Brovchenko // USSR Author's Certificate No. SU 1054864 A. - Publ. 15.11.83 in BI No. 42). This device, the block diagram of which is shown in FIG. 1, consists of an auto-oscillator (AG) 1 on a transistor connected according to a common base circuit, an idling filter (PCF) 2 and an extractable harmonic filter (CVF) 3. The auto-oscillator 1 is represented as a generalized circuit containing active 4 and passive 5 elements , which is described by the complex transmission coefficients G (jω) and H ₁ (jω). The nonlinear mode of AG operation leads to the generation of oscillations of the fundamental frequency and its harmonics. With respect to the output power of the main ("carrier") oscillations, typical power levels of the second and third harmonics are usually in the range of - (10-20) and - (20-35) dBc, respectively (See, for example, Fig. 5-28 and 5-29 in [1]). This device implements the “idle” mode at the fundamental frequency ƒ ₀ , and with the help of the HFG filter, the output power of the k-th harmonic is allocated - kƒ ₀ . The use of filter 3 leads here to an increase in the output power of the harmonic by (30–40)%, since if there is an unloaded circuit in the collector circuit of the transistor, not only direct, but also intermediate conversion of the first harmonic power into the output harmonic power occurs.

The disadvantage of this analog is the relatively low power level of the emitted harmonics.

The oscillator integrated in the microstrip microwave antenna is known (See Lyubchenko, VE. Generation of harmonics in a microstrip antenna-generator circuit integrated with a waveguide embedded in a dielectric substrate) / V.E. Lyubchenko, V.I. Kalinin, V.D. Kotov, DE Radchenko, SA Telegin, EO Yunevich // Journal of Radio Electronics. - № 2. - 2016). This device corresponds to the block diagram in FIG. 1, where the functions of filters FHH and FVG are performed by a waveguide, which is beyond the limits for the first harmonic, and the second harmonic in it spreads freely.

This analog has the same drawback - the relatively low power level of the emitted harmonics.

Known microwave harmonic oscillator (See Yabuki, H. Y. Yaguki, M. Sagawa, M. Makimoto). IEEE MTT-S Int. Microwave Symp. Dig. - 1992. - P. 1085 - 1088). Its block diagram is shown in FIG. 2. This device contains two oscillation outputs at the fundamental ƒ ₀ and twice the 2ƒ ₀ frequencies. It consists of two AGs 6 and 7, where the active elements 8, 9 operate on a common resonant system 10, the main elements of which are connected first and second segments of long microstrip lines. With identical modes of operation of transistors in AG 6 and 7 and the exact connection of their load to the midpoint of the first segment of the long line, the addition of even harmonic components occurs and the device works as a frequency multiplier by two [2]. In this case, from the output of the second segment of the long line, the oscillation of the fundamental frequency ƒ ₀ with a power of -5 dBm is released. However, at the other output of the device, the output power of the second harmonic 2ƒ ₀ is only -9 dBm, even with the use of the amplifier 11.

The disadvantage of this device, as well as other “push-push” generating systems similar to it [3, 4], is the relatively low level of harmonic power.

The closest to the proposed technical solution is a voltage-controlled microwave generator (See Obregon, J. Ultrabroadband electronically tunable oscillators / J. Obregon, PG Marechal, Y. Le Tron, R. Funck // Proceedings of the 11th European Microwave Conference, 7 -11 Sept., 1981, Amsterdam, Netherlands. - 1981. - P. 475 - 479). The generator (See. Fig. 3) is made on a bipolar transistor 12 connected in accordance with a common base circuit. At its input, the negative resistance necessary for oscillation generation is realized. Thus, in the selected model of the transistor [5], where its base is loaded on inductance 13, and the collector is on capacitance 14, the emitter circuit of the transistor is the sum of conductivities formed by equivalent negative resistance and capacitance. To compensate for the latter, additional inductive elements 15 and 16 are used in the input circuit. Together with them, the capacitance of the varicap 17 and the capacitor 18 also participate in the compensation process of the capacitor. The oscillator in FIG. 3 contains inductive 19-22 and capacitive 23-28 elements of the isolation of the microwave power supply circuits, as well as the separation capacitor 29 at the 50-ohm output. Terminal 30 is used to apply the blocking voltage to varicap 17, and terminals 31-33 are used to enter the supply voltage to the transistor electrodes.

The disadvantage of the prototype device is the relatively low power level of the emitted harmonics.

The technical effect that the proposed solution aims to achieve is to increase the power level of the allocated k-th harmonic of the tunable generators with respect to the output power of their oscillations of the main frequency (k≥2).

This effect is achieved by the fact that in a tunable harmonic oscillator containing a transistor 34 connected in a common base circuit, inductances and capacitors numbered in series 19 and 23, 20 and 24, 21 and 26, 22 and 25, respectively, where the second plates of all capacitors 23-26 are connected to a common bus, and the common points of each pair of elements are connected to terminals 30 and 32, 31, 33 of the varicap control voltage supply sources 39 and the supply voltages to the electrodes of the transistor 34, and the varicap cathode 39 is connected to the free water inductance 19, as well as to capacitor 35, inductance 41, connected by a single plate to a common bus, capacitors 36 and 38, a series-connected capacitor 37 and inductance 40, the common point of which is connected to the free inductance terminal 21, and they are connected between the common bus and the base of the transistor 34, the emitter and the collector of which are connected respectively to the free inductance terminals 20 and 22, the output of the last of them is additionally connected via a capacitor 29 to the output of the device, according to the invention, the second facing the capacitor 35 is connected to the emitter of the transistor 34, and the varicap 39 anode is connected to the common bus, the second plate of the capacitor 36 is connected to the base of the transistor 34, and the second plate of the capacitor 38 is connected to the inductance 41, the other terminal of which is connected to the collector of the transistor 34, and the values of the main elements harmonic oscillator satisfy the following relationship:

where ƒ ₀ - fundamental frequency generating device, k = 2, 3, ... - number allocated harmonic, C _AE - junction capacitance of the collector-emitter of the selected transistor 34, C _OS - the equivalent capacitance operating at the fundamental frequency connected in emitter and base loops: an emitter the circuit is formed by the inductance 20 and the capacitances of the varicap 39 and the capacitor 35, the base circuit is formed by the inductance 40 and the capacitors 36 and 37, L _QC is the equivalent inductance of the serially connected base and collector circuits, the latter is formed by the inductive 41 and the capacitor 38 and operates at the main frequency, C _OE is the equivalent capacitance of the emitter circuit connected when operating at the k-th harmonic of the main oscillation with the collector circuit using a capacitor C _AE , L _B equivalent inductance of the basic circuit operating at the k-th harmonic of the main oscillation, L _K - equivalent inductance of the collector circuit,

associated with a capacitor C _AE with an emitter circuit during operation at the k-th harmonic of the main oscillation.

A schematic diagram of the proposed device is presented in FIG. 4. Tunable harmonic oscillator is made on a bipolar transistor 34, included in the scheme with a common base. In the microwave range, the main frequency-generating elements are the capacitor-emitter transistor junction capacitance C _CE , capacitor capacitors 35-38, varicap 39 and inductance 40 and 41. In addition, the device contains inductive 19-22 and capacitive 23-26 elements of the junction of the microwave circuits nutrition, which may also have a slight effect on the frequencies, to a greater extent, of the main and, to a lesser extent, harmonic oscillations. Due to the nature of the device, we will take into account the influence of only one decoupling element 20, neglecting the influence of the others. The generator is connected to the 50-ohm output through the separation capacitor 29. Terminal 30 is used to supply the blocking voltage to the varicap 39, and terminals 31 - 33 are used to enter the supply voltages to the electrodes of the transistor.

The proposed device operates as follows. Let us estimate the fundamental possibilities for the simultaneous generation of oscillations of the fundamental frequency and its kth harmonic. To this end, in FIG. 5, we consider a generalized model of an oscillatory system, where one amplifying element 42 with a transmission coefficient G (jω) operates simultaneously on two circuits (43 and 44) with transmission coefficients H ₁ (jω) and H _k (jω), one configured to generate oscillations the main frequency, and the other - to generate its k-th harmonic. For this case, we establish the relationship of the input V _in (ω) and output V ₀ (ω) voltage in the form:

From equation (1) it follows that even when V _in (ω) = 0, the output voltage V ₀ (ω) of the oscillatory system in FIG. 5 may be non-zero under the following conditions:

The obtained conditions (2) and (3) generalize the Barkhausen criterion [3, 4] for any cases when oscillatory systems simultaneously generate oscillations of the fundamental frequency and its kth harmonic. For a particular case, when generation takes place, both at the fundamental frequency and at its harmonic, that is, when the following system is valid:

the multiplicity of 2π in expression (3) is preserved and condition (3) is also automatically satisfied.

Thus, the obtained expressions (2) and (3) confirm the possibility of the simultaneous generation of oscillations of the fundamental frequency and its kth harmonic. In other words, if conditions (4) are created for generating oscillations at the fundamental frequency and at its kth harmonic, then at these frequencies it is possible to obtain oscillations with approximately equal levels of their output powers. This level equality can be achieved if the transmission ratios of the active and passive circuits in FIG. 5, as well as the dynamic range in the output power of the selected transistor will differ little from each other at the fundamental frequency and at its kth harmonic.

We realize the described possibilities in the one proposed in FIG. 4 device. Let us explain the operation of this generator using the simplified scheme, which is shown in FIG. 6. In the simplified generator model, two three-point schemes are distinguished: triangular (See. Fig. 7a)) and star-shaped (See. Fig. 7b)). A triangular circuit is a conventional three-point capacitive circuit whose points are marked with the letters a, b, and c. The star-shaped circuit was obtained in [6] from a typical triangular circuit of an inductive three-point based on the general reciprocal conditions of equivalent transformations of a resistance triangle into a star and vice versa - transformation of a star's resistance into a triangle. In the star schema in FIG. 7b) the points are also marked with the letters a, b and c, and the instrument case is used as the center point of the star.

The triangular three-point generator circuit in FIG. 6 is implemented if, under elements 45, 46 and 47 in FIG. 7a) understand the following reactivity. The element 45 is formed by the transition capacitance "active element" 48 - C _AE or capacity "collector-emitter" of the transistor C _CE . Element 46 is a feedback capacitance — C _OS or equivalent capacitance operating at the main frequency of serially connected emitter and base circuits (see FIG. 6). The emitter circuit here is formed by the inductance 20 and the capacitances of the varicap 39 and the capacitors 24, 35, and the base circuit is formed by the inductance 40 and the capacitors 36, 37. The element 47 in FIG. 7a) is the inductance of an “oscillatory circuit” L _KK , which is the equivalent inductance of series-connected basic and collector circuits (see Fig. 6). Moreover, the collector circuit is formed by an inductance 41 and a capacitor 38 and operates at the main frequency.

In this case, the generation frequency is found from the condition: X _AE + X _OS + X _KK = 0 [7],

, и равна:where X _KK = 2πƒ ₀ L _KK ,

, and is equal to:

The star-shaped three-point generator circuit in FIG. 6 is implemented if, under items 54-56 in FIG. 7b) understand the following reactivity. Element 54 is an equivalent capacitance C _E emitter circuit connected during operation to k-th harmonic of the fundamental oscillation to the collector circuit by means of the capacitor C _FE in FIG. 6. Elements 55, 56 represent the equivalent inductance L _{B of the} basic circuit operating on the k-th harmonic of the main oscillation, and, accordingly, the equivalent inductance L _{K of the} collector circuit connected by means of the capacitor C _CE in FIG. 6 with an emitter circuit during operation at the kth harmonic of the fundamental oscillation.

For a star generator circuit, its frequency kƒ ₀ is found from the condition:

, Х_К=2πkƒ₀L_К, Х_Б = 2πkƒ₀L_Б, и равна:Х _К Х _Э + Х _Э Х _Б + Х _К Х _Б = 0 [8], where

, X _K = 2πkƒ ₀ L _K , X _B = 2πkƒ ₀ L _B , and is equal to:

If the harmonic oscillator operates at high frequencies, then in order to observe ratios (5) and (6), it is necessary to fulfill additional conditions under which the connection points of the “earth” contacts 49, 50, 51, 52 and 53 to the common bus in FIG. 6 should be located as close as possible to each other. Otherwise, constructive inductances that occur between the specified points should be taken into account when calculating the values of the elements included in formulas (5) and (6).

Simultaneous fulfillment of conditions (5) and (6) assumes that the reactivity sign of the equivalent resistances of the basic circuit operating at the fundamental frequency and its kth harmonic must be fundamentally different: negative at the fundamental frequency and positive at the kth harmonic. In other words, at the fundamental frequency and its k-th harmonic, the equivalent impedance of the basic circuit must be capacitive and inductive in nature, respectively.

Thus, when choosing the ratings of the frequency-setting elements in accordance with formulas (5) and (6) or in accordance with the expression:

conditions for the simultaneous generation of oscillations of the fundamental frequency and its kth harmonic are realized. As a result of the generation at these frequencies, one can expect an increase in the output power of the kth harmonic, at least to the output power level of the oscillation of the fundamental frequency. Moreover, this positive effect is achieved here without the need to tune various (unloaded, loaded, transcendent, and other) circuits at the outputs of similar harmonic autogenerators.

An example of a specific implementation of the device. Consider a tunable harmonic oscillator that simultaneously generates oscillations at the fundamental frequency and at the second harmonic (k = 2) in the vicinity of frequencies 5 and 10 GHz. In accordance with the scheme in FIG. 4, the generator is implemented using hybrid-integrated technology on a polycore substrate 10 × 12.5 × 0.5 mm in size, which is located in a housing with dimensions of 12.5 × 20 × 5 mm (see Fig. 8). This generator is made on a silicon bipolar transistor 34 of type 2T648A-5, which in a common base circuit operates up to 12 GHz, that is, it has a gain characteristic of technical conditions [9] for oscillation gain, both at the fundamental frequency and at its harmonic. From the equivalent circuit of the package transistor given in technical conditions [9], we use only the collector-emitter junction capacitance C _CE = 0.1 pF, since there are no other parasitic structural elements in the transistor crystal. As a diode with a variable capacitance 39, a silicon varicap crystal 2B174A9 is used, whose capacitance varies in the range from 0.7 to 2.5 pF. In the generator under consideration, ceramic chip capacitors K10-71 with the smallest possible dimensions and the following values are used as capacitive elements: ≈0.2 pF (for elements 35, 36), 1.5 pF (for elements 37, 38), 47 pF (for elements 23 - 26), 15 pF (for element 29). Gold wires 15 μm thick and 4.5 to 5.5 mm long with calculated inductances from 5.5 to 6.5 nH are used as inductive elements 19-22 in the circuit in FIG. 4. The magnitudes of the inductive elements 40 and 41 (in the form of 15 μm gold wires) are also calculated and are ≈0.6 and ≈2.5 nH, respectively. Using in formulas (5) - (7) the selected and calculated values of the circuit elements in FIG. 4, the fundamental frequency and its second harmonic were estimated. Their values are 5.6 and 10.2 GHz. When conducting frequency evaluations, spurious inductances between the points of connection of the “earth” contacts 49, 50, 51, 52 and 53 to the common busbar were taken into account.

The developed device generates oscillations of the fundamental frequency (≈4.91 GHz) and the second harmonic (≈9.82 GHz) with a total power of ≈5 dBm at a collector supply voltage of +6 V and a current consumption of ~ 25 mA. When the control voltage varies from 0 to 12 V, the frequency of the second harmonic changes from 9.75 to 10 GHz. For the considered model operating at a control voltage of +2.5 V, Fig. 9 shows the spectrum of its output oscillation, which is obtained using the FSUP-26 spectrum analyzer (ROHDE & SCHWARZ). From FIG. 9 that the second harmonic level is approximately 5 dB higher than the output power level of the fundamental frequency oscillations, which experimentally confirms the declared positive effect.

Thus, the given example of a specific implementation of a tunable harmonic oscillator confirms the possibility of obtaining elevated power levels of the allocated kth harmonic with respect to the output power of the oscillations of the fundamental frequency (k≥2). Theoretically, at the fundamental frequency and at its kth harmonic, it is possible to receive oscillations with approximately equal levels of their output powers. It was established experimentally that the levels of the output power of oscillations with the frequency of the k-th harmonic can be relatively higher.

Information sources

1. R & S FSUP Signal source analyzer / Quick start guide // Rohde & Schwarz GmbH & Co. -Germany, Munich. - 2011.

2. Grebennikov, A.B. Octave oscillators of the UHF range on MOS transistors / A.V. Grebennikov, V.V. Nikiforov // Semiconductor electronics in communication technology; by ed. I.F. Nicholas. - M .: Radio and Communication. - 1986. - Vol. 26. - p. 188-194.

3. Rohde, U.L. Oscillators for wireless applications / U.L. Rohde, A.K. Poddar, G. Bock. - New Jersey, USA: John Wiley & Sons, Inc., 2005. - 543 p.

4. Grebennikov, A. RF and microwave transistor oscillator design / A. Grebennikov. - Chichester, England: John Wiley & Sons, Ltd, 2007. - 441 p.

5. Marechal, P.G. 1.5 to 4.5 GHz varactor-tuned transistor oscillator / P.G. Marechal, J. Obregon // Proceedings of the 9th European Microwave Conference, 1979, Brighton, U.K. - 1979. P. 621-624)

6. Rams, A.B. Private and generalized equivalent three-point circuits for microwave oscillators / A.V. Baranov // Electronic equipment. Ser. 1. Microwave technology. - 2017. - Vol. 1 (532). - p. 18-25.

7. Radio transmitting devices / Ed. Mv Blagoveshchenskogo, G.M. Utkin. - M .: Radio and communication, 1982. - 408 p.

8. Baranov, A.V. Voltage controlled system of two mutually synchronized microwave oscillators / AV Baranov // Proceedings of the XIXth Coordination Scientific and Technical Seminar on Microwave Engineering, Khakhali, Nizhny Novgorod Region, (05-07). 09.2017. - Nizhny Novgorod, 2017. - p. 55-57.

9. Devices semiconductor unpackaged. Transistor 2T 648 A-5. Private technical conditions AAO. 339.266 TU / D1. - 1981.

Claims (3)

Tunable harmonic oscillator containing a transistor 34, connected according to a common base circuit, inductors connected in series and capacitors numbered 19 and 23, 20 and 24, 21 and 26, 22 and 25, respectively, where the second plates of all capacitors 23-26 are connected to a common bus, and the common points of each pair of elements are connected to terminals 30 and 32, 31, 33 of the voltage supply sources of the varicap control 39 and the supply voltages to the electrodes of the transistor 34, with the cathode of the varicap 39 connected to the free inductance terminal 19, as well as to the capacitor 35, inductance 41, connected by one plate to a common bus, capacitors 36 and 38, a series 37 capacitor 37 and an inductance 40, the common point of which is connected to the free inductance 21, and they are connected between the common bus and the base of the transistor 34, emitter and collector which are connected respectively with the free inductance pins 20 and 22, the output of the latter is additionally connected through the capacitor 29 to the output of the device, characterized in that the second plate of the capacitor 35 is connected to the emitter the transistor 34 transducer, and the varicap 39 anode to the common bus, the second capacitor 36 lining is connected to the transistor 34 base, and the second capacitor 38 lining to the inductance 41, the other output of which is connected to the collector of the transistor 34, and satisfy the following main ratio:

where ƒ ₀ is the main generation frequency of the device, k = 2, 3, ... is the number of the extracted harmonic, C _AE is the collector-emitter junction capacitance of the selected transistor 34, C _OC is the equivalent capacitance of the emitter and base circuits operating at the main frequency: emitter circuit 20 is formed by the inductance and capacitance of varactor 39 and capacitor 35, the basic circuit - inductance 40 and the capacitors 36 and 37, L _QC - equivalent inductance series connected base and collector circuits, the latter is formed by the inductive spine 41 and the capacitor 38, and operates at the fundamental frequency, C _e - the equivalent capacitance of the emitter circuit, associated with work on a k-th harmonic of the fundamental oscillation to the collector circuit by means of the capacitor C _AE, L the inductance of the base _B -equivalent circuit operating at k- th harmonic of the main oscillation, L _K - equivalent inductance of the collector circuit, connected with the help of the capacitor C _AE with the emitter circuit during operation on the k-th harmonic of the main oscillation.

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