Amplification circuit

Abstract

A technology is provided that enables amplification in lower frequency bands while suppressing performance degradation in higher frequency bands in an amplifier circuit that can operate in multiple frequency bands. In an amplifier circuit (1), an input transformer (16) divides a first input signal in a first frequency band into a first signal and a second signal that are opposite in phase to each other, and divides a second input signal in a second frequency band different from the first frequency band into a third signal and a fourth signal that are in phase to each other. A first amplifying element (18) amplifies the first signal or the third signal divided by the input transformer (16). A second amplifying element (20) amplifies the second signal or the fourth signal divided by the input transformer (16). An output transformer (22) combines the signal amplified by the first amplifying element (18) and the signal amplified by the second amplifying element (20) and outputs the combined signal.

Description

[Technical Field]

[0001] The present invention relates to an amplifier circuit that can operate in multiple frequency bands. [Background technology]

[0002] Some multi-frequency band amplifier circuits used in communication devices, such as transmitters, have multiple amplifiers optimized for each required frequency band, and these amplifiers are switched to operate according to the frequency band being used. Each of the multiple amplifiers has multiple amplifying elements and input / output transformers. This configuration requires multiple sets of expensive amplifying elements and input / output transformers, which increases the cost and requires a large mounting area. Therefore, for example, in commercially available amateur radio devices housed in a single housing, it is desirable to reduce the price and mounting area of ​​the amplifier circuit.

[0003] A known example of a multi-frequency band amplifier circuit with a simpler configuration than the above amplifier circuit is the amplifier circuit disclosed in Patent Document 1. This amplifier circuit divides a first input signal in a first frequency band into +90-degree and -90-degree signals using a phase-shift divider, amplifies the first input signal divided by the phase-shift divider separately using two amplifier elements, and phase-combines the amplified outputs using a phase combiner, thereby causing the two amplifier elements to perform push-pull amplification. This amplifier circuit also divides a second input signal in a second frequency band that is input at a different time from the first input signal using an in-phase divider, amplifies the second input signal divided by the in-phase divider separately using the two amplifier elements, and in-phase-combines the amplified outputs using an in-phase combiner, thereby causing the two amplifier elements to perform parallel amplification. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3508835 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, there is a demand for efficient amplification of signals in a relatively wide frequency band, such as 100 kHz to 70 MHz. In order to amplify signals in such a wide frequency band using the amplifier circuit of Patent Document 1, it is necessary to amplify signals in a relatively high frequency band, such as 1.8 MHz to 70 MHz, using a transformer through push-pull amplification, and to amplify signals in a relatively low frequency band, such as 100 kHz to 500 kHz, using an in-phase splitter.

[0006] To configure an in-phase splitter that operates in the above-mentioned low frequency band, it is necessary to use an inductor, rather than the capacitor disclosed in Patent Document 1. However, an in-phase splitter that uses an inductor requires multiple inductors with large inductance, which tends to increase the size of the amplifier circuit. Furthermore, in the above-mentioned high frequency band, appropriate amplification may be difficult to achieve due to the influence of mismatch and loss caused by the capacitance of the inductor, making it difficult to realize.

[0007] The present invention has been made in consideration of these circumstances, and its purpose is to provide a technology that enables amplification in lower frequency bands while suppressing performance degradation in higher frequency bands in an amplifier circuit that can operate in multiple frequency bands. [Means for solving the problem]

[0008] In order to solve the above problem, an amplifier circuit according to one embodiment of the present invention includes an input transformer that divides a first input signal in a first frequency band into a first signal and a second signal that are opposite in phase to each other, and divides a second input signal in a second frequency band different from the first frequency band into a third signal and a fourth signal that are in phase with each other, a first amplifier element that amplifies the first signal or the third signal divided by the input transformer, a second amplifier element that amplifies the second signal or the fourth signal divided by the input transformer, and an output transformer that combines the signal amplified by the first amplifier element and the signal amplified by the second amplifier element and outputs the combined signal.

[0009] Any combination of the above components and conversion of the present invention into a method, device, system, etc. are also effective aspects of the present invention. [Effects of the Invention]

[0010] According to the present invention, in an amplifier circuit capable of operating in a plurality of frequency bands, it is possible to amplify in lower frequency bands while suppressing performance degradation in higher frequency bands. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram of an amplifier circuit according to a first embodiment. [Figure 2] 2 is a block diagram for explaining the operation of the amplifier circuit of FIG. 1 when a first input signal in a first frequency band is input. [Figure 3] 2 is a block diagram for explaining the operation of the amplifier circuit of FIG. 1 when a second input signal in a second frequency band is input. [Figure 4] FIG. 10 is a block diagram of an amplifier circuit according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the description, the same elements are denoted by the same reference numerals, and duplicate descriptions will be omitted as appropriate.

[0013] (First embodiment) FIG. 1 is a block diagram of an amplifier circuit 1 according to a first embodiment. The amplifier circuit 1 can be mounted in a wireless communication device such as an amateur radio and can amplify wireless signals. The amplifier circuit 1 can amplify signals in multiple frequency bands. The multiple frequency bands include a predetermined first frequency band and a predetermined second frequency band different from the first frequency band. The first frequency band is higher than the second frequency band. The amplifier circuit 1 can also be called a multi-frequency band amplifier circuit.

[0014] The amplifier circuit 1 includes a first input terminal 10, a second input terminal 12, a first switch 14, an input transformer 16, a first amplifying element 18, a second amplifying element 20, an output transformer 22, a second switch 24, a first output terminal 26, a second output terminal 28, and a control unit 30.

[0015] A first input signal in a first frequency band is input to a first input terminal 10. The first input terminal 10 is connected to one end of a primary winding 16a of an input transformer 16. The other end of the primary winding 16a is grounded.

[0016] A second input signal of a second frequency band is input to the second input terminal 12 at a time different from that of the first input signal. In other words, it is assumed that the period during which the first input signal is input is different from the period during which the second input signal is input. The second input terminal 12 is connected to the midpoint tap of a secondary winding 16b of an input transformer 16. One end of the secondary winding 16b is connected to the input terminal of a first amplifying element 18. The other end of the secondary winding 16b is connected to the input terminal of a second amplifying element 20.

[0017] The first amplifying element 18 and the second amplifying element 20 each amplify a signal supplied to their input terminal and output the amplified signal from their output terminal. Various known amplifying elements can be used as the first amplifying element 18 and the second amplifying element 20.

[0018] One end of the primary winding 22a of the output transformer 22 is connected to the output terminal of the first amplifying element 18. The other end of the primary winding 22a is connected to the output terminal of the second amplifying element 20.

[0019] The second output terminal 28 is connected to the midpoint tap of the primary winding 22a of the output transformer 22. The second output terminal 28 outputs a second output signal in the second frequency band.

[0020] The first output terminal 26 outputs a first output signal in a first frequency band. The first output terminal 26 is connected to one end of the secondary winding 22b of the output transformer 22. The other end of the secondary winding 22b is grounded.

[0021] The first switch 14 is connected between one end of the primary winding 16a of the input transformer 16 and ground, and is capable of short-circuiting both ends of the primary winding 16a when turned on. The second switch 24 is connected between one end of the secondary winding 22b of the output transformer 22 and ground, and is capable of short-circuiting both ends of the secondary winding 22b when turned on. The first switch 14 and the second switch 24 can each be configured, for example, by a relay, a diode switch, or a switch IC.

[0022] The control unit 30 controls each of the first switch 14 and the second switch 24 to be on or off, i.e., to be in a short-circuited state or an open state. The control unit 30 can be configured, for example, by a microcomputer.

[0023] For example, the first frequency band may be 1.8 MHz to 70 MHz, and the second frequency band may be 100 kHz to 1.8 MHz, but the frequency ranges can be determined appropriately.

[0024] In the case of the above frequency band, the input transformer 16 may have, for example, a turns ratio between the primary winding 16a and the secondary winding 16b of 4:1, and an inductance ratio between the primary winding 16a and the secondary winding 16b of 16:1. For example, the inductance of the primary winding 16a may be 40 μH, and the inductance of the secondary winding 16b may be 2.5 μH.

[0025] In the output transformer 22, for example, the turns ratio between the primary winding 22a and the secondary winding 22b may be 1:4, and the inductance ratio between the primary winding 22a and the secondary winding 22b may be 1:16. For example, the inductance of the primary winding 22a may be 2.5 μH, and the inductance of the secondary winding 22b may be 40 μH.

[0026] These numerical examples are provided to facilitate understanding of the embodiments, and are not particularly limited. Optimum values ​​for inductance, etc. can be determined appropriately through experiments or simulations.

[0027] Next, the overall operation of the amplifier circuit 1 configured as described above will be described. Fig. 2 is a block diagram for explaining the operation of the amplifier circuit 1 of Fig. 1 when a first input signal in1 of a first frequency band is input. In Fig. 2, the control unit 30 is not shown.

[0028] When a first input signal in1 having a frequency f1 is input from the first input terminal 10 to the input transformer 16, the control unit 30 controls the first switch 14 and the second switch 24 to be open. The frequency f1 is included in the first frequency band. At this time, the second input terminal 12 and the second output terminal 28 are in an electrically floating state.

[0029] The input transformer 16 divides the first input signal in1 into a first signal s1 and a second signal s2, which are opposite in phase to each other. When the first input signal in1 is input to one end of the primary winding 16a of the input transformer 16, the first signal s1 is output from one end of the secondary winding 16b of the input transformer 16, and the second signal s2 is output from the other end of the secondary winding 16b of the input transformer 16.

[0030] Specifically, the input transformer 16 transmits the first input signal in1 from the primary winding 16a to the secondary winding 16b by magnetic coupling, shifts the phase of the first input signal in1 by -90 degrees to output the first signal s1, and shifts the phase of the first input signal in1 by +90 degrees to output the second signal s2.

[0031] The first amplifying element 18 amplifies the first signal s1 distributed by the input transformer 16 and supplies the amplified signal to one end of the primary winding 22a of the output transformer 22. The second amplifying element 20 amplifies the second signal s2 distributed by the input transformer 16 and supplies the amplified signal to the other end of the primary winding 22a of the output transformer 22.

[0032] The output transformer 22 phase-combines the signal amplified by the first amplifying element 18 and the signal amplified by the second amplifying element 20, transmits the combined signal from the primary winding 22a to the secondary winding 22b by magnetic coupling, and outputs the combined signal as a first output signal out1 from the first output terminal 26. In other words, when a first input signal in1 is input to one end of the primary winding 16a of the input transformer 16, the first output signal out1, which is the combined signal, is output from one end of the secondary winding 22b of the output transformer 22.

[0033] In the first frequency band, the input transformer 16 matches the impedance between one end of the primary winding 16a of the input transformer 16 and the input ends of the first amplifying element 18 and the second amplifying element 20. The input transformer 16 forms an input matching circuit.

[0034] In the first frequency band, the output transformer 22 matches the impedance between the output terminals of the first amplifying element 18 and the second amplifying element 20 and one end of the primary winding 22a of the output transformer 22. The output transformer 22 forms an output matching circuit.

[0035] In this way, the first input signal in1 of frequency f1 is phase-shifted by +90 degrees and -90 degrees by the input transformer 16, so that the first signal s1 and the second signal s2, which are out of phase with each other, are input to and amplified by the first amplifying element 18 and the second amplifying element 20, and the amplified signals are combined and output by the output transformer 22. In other words, the first amplifying element 18 and the second amplifying element 20 perform push-pull amplification.

[0036] Fig. 3 is a block diagram for explaining the operation of the amplifier circuit 1 of Fig. 1 when a second input signal in2 of the second frequency band is input. In Fig. 3, the control unit 30 is also omitted.

[0037] When a second input signal in2 of frequency f2 is input from the second input terminal 12 to the input transformer 16, the control unit 30 performs control so that the first switch 14 and the second switch 24 are shorted. The frequency f2 is included in the second frequency band. At this time, it is assumed that the first input signal in1 is not input to the first input terminal 10.

[0038] The input transformer 16 splits the second input signal in2 into a third signal s3 and a fourth signal s4, both of which are in phase with each other. That is, when the second input signal in2 is input to a midpoint tap provided on the secondary winding 16b of the input transformer 16, the third signal s3 is output from one end of the secondary winding 16b of the input transformer 16, and the fourth signal s4 is output from the other end of the secondary winding 16b. The phases of the third signal s3 and the fourth signal s4 are each 0 degrees relative to the phase of the second input signal in2.

[0039] When the first switch 14 is shorted, both ends of the primary winding 16a of the input transformer 16 are shorted and connected to ground. Due to magnetic coupling in the input transformer 16, both ends of the secondary winding 16b are also equivalently shorted, so that the third signal s3 and the fourth signal s4 that are in-phase and distributed are output from both ends of the secondary winding 16b.

[0040] The first amplifying element 18 amplifies the third signal s3 distributed by the input transformer 16 and supplies the amplified signal to one end of the primary winding 22a of the output transformer 22. The second amplifying element 20 amplifies the fourth signal s4 distributed by the input transformer 16 and supplies the amplified signal to the other end of the primary winding 22a of the output transformer 22.

[0041] The output transformer 22 combines the signal amplified by the first amplifying element 18 and the signal amplified by the second amplifying element 20 in phase, and outputs the combined signal as a second output signal out2 from a second output terminal 28 via a midpoint tap of the primary winding 22a. In other words, when a second input signal in2 is input to a midpoint tap provided on the secondary winding 16b of the input transformer 16, the midpoint tap of the output transformer 22 outputs the combined signal, the second output signal out2.

[0042] By shorting the second switch 24, both ends of the secondary winding 22b of the output transformer 22 are shorted and connected to ground. Due to magnetic coupling in the output transformer 22, both ends of the primary winding 22a are also equivalently shorted, and a combined signal is output from the midpoint tap of the output transformer 22. In other words, at this time, the first amplifying element 18 and the second amplifying element 20 operate in phase and perform parallel amplification.

[0043] The reason for providing the first switch 14 on the primary winding 16a side of the input transformer 16 is that, because the impedance on the secondary winding 16b side is low, a low-resistance switch element needs to be connected across the secondary winding 16b to achieve a sufficient short-circuit state, but because the impedance on the primary winding 16a side is higher than that on the secondary winding 16b side, a higher-resistance, less expensive switch element can be used to reliably maintain the short-circuit state.For the same reason, the second switch 24 is provided on the secondary winding 22b side of the output transformer 22, which has a higher impedance.

[0044] When the first input signal in1 of frequency f1 is input from the first input terminal 10 and an amplification operation is performed, the first switch 14 and the second switch 24 are both off, and amplification can be performed without affecting the push-pull amplification operation.

[0045] On the other hand, when the second input signal in2 of frequency f2 is input from the second input terminal 12 and amplification is performed, the first switch 14 and the second switch 24 are both on, and amplification can be performed without affecting the parallel amplification operation.

[0046] As described above, in the amplifier circuit 1, when the first input signal in1 of frequency f1 is input to the first input terminal 10, the input and output are matched with the first amplifying element 18 and the second amplifying element 20 by the input transformer 16 and the output transformer 22, and push-pull amplification is performed by the first amplifying element 18 and the second amplifying element 20. When the second input signal in2 of frequency f2 is input to the second input terminal 12, the input transformer 16 performs in-phase distribution, the output transformer 22 performs in-phase combining, and the first amplifying element 18 and the second amplifying element 20 perform parallel amplification. The pair of first amplifying element 18 and second amplifying element 20, the input transformer 16, and the output transformer 22 are used separately in terms of time for amplifying the second lower frequency band and the first higher frequency band.

[0047] By performing two different amplification operations in this way, it is possible to operate in multiple frequency bands, for example, by operating in a wide first frequency band such as 1.8 MHz to 70 MHz as frequency f1, and by operating in a second frequency band including the 137 kHz band and the 472 kHz band as frequency f2.

[0048] According to the embodiment, in the first frequency band and the second frequency band, a common input transformer 16 is used to distribute the signals, and a common output transformer 22 is used to combine the signals, thereby preventing adverse effects on operation in each frequency band. Therefore, in the amplifier circuit 1 that can operate in multiple frequency bands, it is possible to amplify signals in lower frequency bands while suppressing performance degradation in higher frequency bands.

[0049] Furthermore, by shorting the first switch 14 and the second switch 24 when the second input signal in2 is input, the second input signal in2, which has a higher frequency, can be efficiently amplified, thereby increasing the maximum frequency of the second frequency band.

[0050] The amplifier circuit 1 can be configured by simply adding a small number of components to a push-pull amplifier circuit for one frequency band, and can therefore be configured at low cost with a small mounting area.

[0051] (Second embodiment) The second embodiment differs from the first embodiment in that it does not include the first switch 14 and the second switch 24. The following description will focus on the differences from the first embodiment.

[0052] 4 is a block diagram of an amplifier circuit 1A according to the second embodiment. The amplifier circuit 1A has a configuration in which the first switch 14 and the second switch 24 are removed from the amplifier circuit 1 of FIG.

[0053] The reactance of each winding of the input transformer 16 and the output transformer 22 is set to a necessary and sufficient value in the first frequency band and is set to a negligibly low value in the second frequency band. For example, the inductance of each of the primary winding 16a, the secondary winding 16b, the primary winding 22a, and the secondary winding 22b may be the same as in the first embodiment. In this numerical example, the first frequency band may be 1.8 MHz to 70 MHz, and the second frequency band may be 100 kHz to 500 kHz. In other words, with the same inductance as in the first embodiment, the maximum frequency in the second frequency band may be lower than in the first embodiment.

[0054] Thus, the reactances of the primary winding 16a and secondary winding 16b of the input transformer 16, and the primary winding 22a and secondary winding 22b of the output transformer 22 are set so that both ends of the primary winding 16a of the input transformer 16, both ends of the secondary winding 16b of the input transformer 16, both ends of the primary winding 22a of the output transformer 22, and both ends of the secondary winding 22b of the output transformer 22 are equivalently short-circuited in the second frequency band. For example, the reactance of each of the primary windings 16a, 22a and the secondary windings 16b, 22b may be 1 Ω or less, preferably 0.5 Ω or less, and more preferably 0.1 Ω or less. The reactance of each of the primary windings 16a, 22a and the secondary windings 16b, 22b can be determined appropriately through experiments or simulations.

[0055] The second frequency band is a frequency band in which the reactance of the primary winding 16a and the secondary winding 16b of the input transformer 16 is negligibly low. Therefore, both ends of the primary winding 16a and both ends of the secondary winding 16b of the input transformer 16 can be considered equivalently short-circuited. Therefore, when a second input signal in2 is input from the second input terminal 12 to the midpoint tap of the secondary winding 16b of the input transformer 16, the input transformer 16 splits the second input signal in2 into a third signal s3 and a fourth signal s4, both of which are in phase with each other. The third signal s3 is output from one end of the secondary winding 16b, and the fourth signal s4 is output from the other end of the secondary winding 16b. Note that the illustration of these signals is omitted in FIG. 4 .

[0056] The first amplifying element 18 amplifies the third signal s3 distributed by the input transformer 16 and supplies the amplified signal to one end of the primary winding 22a of the output transformer 22. The second amplifying element 20 amplifies the fourth signal s4 distributed by the input transformer 16 and supplies the amplified signal to the other end of the primary winding 22a of the output transformer 22.

[0057] In the second frequency band, both ends of the primary winding 22a and both ends of the secondary winding 22b of the output transformer 22 can be considered to be equivalently short-circuited. Therefore, the output transformer 22 combines the signal amplified by the first amplifying element 18 and the signal amplified by the second amplifying element 20 in phase, and outputs the combined signal as the second output signal out2 from the second output terminal 28 via the midpoint tap of the primary winding 22a. Therefore, at this time, the first amplifying element 18 and the second amplifying element 20 operate in phase and perform parallel amplification.

[0058] When a first input signal in1 of frequency f1 is input from the first input terminal 10 and amplification is performed, the input transformer 16 and the output transformer 22 have a reactance high enough to perform impedance matching, allowing amplification without affecting the push-pull amplification operation.

[0059] Furthermore, when a second input signal in2 of frequency f2 is input from the second input terminal 12 and amplification is performed, the input transformer 16 and the output transformer 22 have sufficiently low reactance that they can be considered to be in a short-circuited state, and amplification can be performed without affecting the parallel amplification operation.

[0060] As described above, in amplifier circuit 1A, when first input signal in1 of frequency f1 is input to first input terminal 10, input / output matching with first amplifying element 18 and second amplifying element 20 is performed by input transformer 16 and output transformer 22, and push-pull amplification is performed by first amplifying element 18 and second amplifying element 20. When second input signal in2 of frequency f2 is input to second input terminal 12, input transformer 16 performs in-phase distribution, output transformer 22 performs in-phase synthesis, and first amplifying element 18 and second amplifying element 20 perform parallel amplification. These operations are equivalent to those of amplifier circuit 1 in FIG. 1.

[0061] According to the second embodiment, the first switch and the second switch can be omitted, and therefore the circuit configuration can be simplified compared to the first embodiment.

[0062] The present invention has been described above based on the embodiments. These embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of the components and treatment processes, and that such modifications are also within the scope of the present invention. [Explanation of symbols]

[0063] 1,1A...amplifier circuit, 10...first input terminal, 12...second input terminal, 14...first switch, 16...input transformer, 16a...primary winding, 16b...secondary winding, 18...first amplifying element, 20...second amplifying element, 22...output transformer, 22a...primary winding, 22b...secondary winding, 24...second switch, 26...first output terminal, 28...second output terminal.

Claims

1. an input transformer that divides a first input signal in a first frequency band into a first signal and a second signal that are opposite in phase to each other, and divides a second input signal in a second frequency band different from the first frequency band into a third signal and a fourth signal that are in phase to each other; a first amplifying element that amplifies the first signal or the third signal distributed by the input transformer; a second amplifying element that amplifies the second signal or the fourth signal distributed by the input transformer; an output transformer that combines the signal amplified by the first amplifying element and the signal amplified by the second amplifying element and outputs the combined signal; An amplifier circuit comprising:

2. when the first input signal is input to one end of a primary winding of the input transformer, the first signal is output from one end of a secondary winding of the input transformer, and the second signal is output from the other end of the secondary winding of the input transformer; the signal amplified by the first amplifying element is supplied to one end of a primary winding of the output transformer; the signal amplified by the second amplifying element is supplied to the other end of the primary winding of the output transformer; When the first input signal is input to one end of a primary winding of the input transformer, the synthesized signal is output from one end of a secondary winding of the output transformer, when the second input signal is input to a midpoint tap provided in a secondary winding of the input transformer, the third signal is output from one end of the secondary winding of the input transformer, and the fourth signal is output from the other end of the secondary winding of the input transformer; When the second input signal is input to a midpoint tap provided on a secondary winding of the input transformer, the combined signal is output from a midpoint tap of the output transformer.

2. The amplifier circuit according to claim 1 .

3. a first switch capable of short-circuiting both ends of a primary winding of the input transformer; a second switch capable of short-circuiting both ends of a secondary winding of the output transformer; Furthermore, the first frequency band is higher than the second frequency band; When the first input signal is input to the input transformer, the first switch and the second switch are opened; When the second input signal is input to the input transformer, the first switch and the second switch are short-circuited.

3. The amplifier circuit according to claim 2.

4. the first frequency band is higher than the second frequency band; the reactances of the primary winding and secondary winding of the input transformer and the reactances of the primary winding and secondary winding of the output transformer are set so that both ends of the primary winding of the input transformer, both ends of the secondary winding of the input transformer, both ends of the primary winding of the output transformer, and both ends of the secondary winding of the output transformer are short-circuited in the second frequency band; 3. The amplifier circuit according to claim 1, wherein:

5. In the first frequency band, the input transformer matches impedances between one end of a primary winding of the input transformer and each of the input ends of the first amplifying element and the second amplifying element; the output transformer matches impedances between the output terminals of the first amplifying element and the second amplifying element and one end of a primary winding of the output transformer; 4. The amplifier circuit according to claim 1, wherein the first and second input terminals are connected to the first and second input terminals.

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