JP2005020157A - Wireless circuit - Google Patents

Abstract

An inexpensive wireless circuit having good performance is provided.
A radio circuit includes a power amplifier circuit that amplifies a transmission signal, a directional coupler circuit that receives an output of the power amplifier circuit, and a transmission that is output from the directional coupler circuit. A selection circuit 150 having n tuning circuits 141 to 14n having different tuning frequencies for performing impedance matching of signals, a tuning switch 151 to 15n for selecting any one of the n tuning circuits, and a selection circuit 150 And an antenna for transmitting a transmission signal output from the tuning circuit selected by the above. As a result, a high-performance wireless circuit can be provided without using expensive parts such as an isolator.
[Selection] Figure 1

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radio circuit for amplifying a transmission signal and transmitting it from an antenna.
[0002]
[Prior art]
FIG. 3 is a diagram showing a schematic configuration of a radio circuit of a conventional mobile phone.
The radio circuit 300 includes a power amplifier circuit 31, a coupler circuit 32, a tuning circuit 33, an isolator 34, an antenna switching unit 35 having a transmission / reception switch 351, an antenna 36, a filter circuit 37, and a low noise amplifier circuit. 38.
[0003]
In the radio circuit 300 configured as described above, at the time of transmission, the transmission signal input from the transmission terminal TX is amplified to a desired power level by the power amplifier circuit 31, and the amplified transmission signal is tuned via the coupler circuit 32. Input to the circuit 33. At this time, the output of the coupler circuit 32 is propagated to the detection terminal D for power level detection. The transmission signal input to the tuning circuit 33 is input / output impedance matched (here, optimization of adjacent channel leakage power) and then input to the isolator 34.
[0004]
In the transmission signal input to the isolator 34, power loss in the traveling direction (direction from the tuning circuit 33 toward the antenna switching unit 35) is suppressed, and power in the reverse direction (direction from the antenna switching unit 35 toward the tuning circuit 33) is reduced. It can be suppressed. The isolator 34 prevents further intrusion of the interference wave input from the antenna 36. The transmission signal output from the isolator 34 is propagated to the antenna 36 via the transmission / reception switch 351 and is transmitted to the outside here.
[0005]
On the other hand, at the time of reception, the signal received by the antenna 36 is propagated to the filter circuit 37 via the transmission / reception switch 351 of the antenna switching unit 35. The received signal propagated to the filter circuit 37 is input to the low noise amplifier circuit 38 with power loss suppressed only in a desired band. The reception signal input to the low noise amplifier circuit 38 is amplified to a desired power level and output to the reception terminal RX (see, for example, Patent Document 1).
[0006]
Thus, in the conventional radio circuit, by providing the isolator 34, it is possible to reduce the influence of the interference wave input from the antenna 36 at the time of transmission. Further, by providing the tuning circuit 33 and performing impedance matching, it is possible to optimize the adjacent channel leakage power. With the configuration as described above, a wireless circuit having good performance is realized.
[0007]
[Patent Document 1]
Japanese translation of PCT publication No. 2002-528946
[Problems to be solved by the invention]
However, in the above-described conventional wireless circuit, the cost of manufacturing the wireless circuit increases because the cost of the isolator component is high.
[0009]
The present invention has been made in view of the above circumstances, and an object thereof is to provide an inexpensive wireless circuit having good performance.
[0010]
[Means for Solving the Problems]
The radio circuit according to the present invention performs impedance matching of a power amplification circuit that amplifies a transmission signal, a directional coupler that receives an output of the power amplification circuit, and a transmission signal that is output from the directional coupler. A plurality of tuning circuits having different tuning frequencies, a selection circuit for selecting any one of the plurality of tuning circuits according to the frequency of the transmission signal, and a transmission output from the tuning circuit selected by the selection circuit And an antenna for transmitting a signal.
[0011]
With this configuration, since the interference wave input from the antenna is reduced by the directional coupler, expensive components such as an isolator can be eliminated. In addition, since impedance matching is performed by selecting one of a plurality of tuning circuits according to the frequency of the transmission signal, impedance can be corrected for each desired transmission frequency, and deterioration of IM (intermodulation) characteristics can be prevented. Can do. Therefore, an inexpensive wireless circuit having favorable characteristics can be provided.
[0012]
Further, the radio circuit of the present invention includes a switching unit that switches the antenna between a transmission system and a reception system, the switching unit includes the selection circuit, and the plurality of tuning circuits include the switching unit and the switching unit. It is arrange | positioned between the said directional couplers.
[0013]
With this configuration, a plurality of tuning circuits are arranged outside the switching means, and the constants of the tuning circuit can be easily changed in accordance with the frequency band of the transmission signal.
[0014]
The radio circuit of the present invention includes switching means for switching the antenna between a transmission system and a reception system, and the switching means incorporates the plurality of tuning circuits and the selection circuit.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 is a diagram showing a schematic configuration of a radio circuit mounted on a mobile communication device or the like for explaining a first embodiment of the present invention.
The radio circuit 100 includes a power amplifier circuit 11, a directional coupler circuit 12, an antenna switching unit 13, an antenna 14, a filter circuit 15, and a low noise amplifier circuit 16. The antenna switching unit 13 includes a transmission / reception switch (SW) 131, n (n is a plurality) tuning circuits 141 to 14n formed of π-type chip capacitors and chip coils, and n tuning switches (SW). ) 151 to 15n.
[0016]
The power amplification circuit 11 amplifies the transmission signal input to the transmission terminal TX to a desired power level. The directional coupler circuit 12 propagates the transmission signal amplified by the power amplifier circuit 11 to the tuning circuits 141 to 14n and propagates the transmission signal to the detection terminal D for detecting the power level. The directional coupling circuit 12 performs an operation of returning a part of the signal detected at the detection terminal D to the input in order to maintain and control the output gain of the power amplifier circuit 11 to be constant.
[0017]
Each of the tuning circuits 141 to 14n performs impedance matching of the transmission signal output from the directional coupler circuit 12. Impedance matching here refers to optimization of adjacent channel leakage power. The tuning circuits 141 to 14n each have a different frequency to be tuned, and when the frequency to be tuned matches the transmission frequency of the transmission signal, appropriate input / output impedance matching can be achieved.
[0018]
The selection circuit 150 selects one tuning circuit that can perform appropriate impedance matching, and propagates the output signal of the selected tuning circuit to the input terminal (1) of the transmission / reception switch. The antenna switching unit 13 switches the transmission / reception switch 131 between the input terminal (1) and the output terminal (2) during communication, and switches between the transmission system and the reception system. The antenna 14 sends the transmission signal propagated to the input terminal (1) to the outside, and inputs the reception signal received from the outside to the output terminal (2).
[0019]
Next, the operation of the radio circuit 100 will be described.
At the time of transmission, the transmission signal input from the transmission terminal TX is amplified by the power amplifier circuit 11 and then input to the antenna switching unit 13 through the directional coupler circuit 12.
[0020]
The directional coupler circuit 12 is configured so that the interference wave input from the antenna 14 is propagated to the detection terminal D than the power level when the transmission signal input from the power amplifier circuit 11 is propagated to the detection terminal D. The power level is set to be lower. For this reason, the power level detected at the detection terminal D depends on the power level of the signal output from the power amplifier circuit 11, and the influence of the interference wave from the antenna 14 can be reduced. Further, the directional coupler circuit 12 can propagate the power output from the power amplifier circuit 11 to the tuning circuits 141 to 14n with almost no loss.
[0021]
The transmission signal propagated from the directional coupler circuit 12 is subjected to input / output impedance matching in each of the tuning circuits 141 to 14n, and only the output of the tuning circuit selected by the selection circuit 150 is transmitted to the transmission / reception switch 131. Propagated to the input terminal (1). Thereby, impedance matching suitable for each frequency band designated in advance can be performed, and deterioration of IM characteristics can be prevented. The transmission signal propagated to the input terminal (1) is propagated to the antenna 14 via the transmission / reception switch 131, and is transmitted to the outside here.
[0022]
On the other hand, at the time of reception, a reception signal received by the antenna 14 is input from the input / output terminal (3) of the transmission / reception switch 131 to the filter circuit 15 via the input terminal (2), and power is supplied only in a desired band. Loss is suppressed. The reception signal in the desired band output from the filter circuit 15 is amplified to a desired power level by the low noise amplifier circuit 16 and then output to the reception terminal RX.
[0023]
As described above, according to this embodiment, since the influence of the interference wave from the antenna 14 is suppressed by the directional coupler circuit 12, it is not necessary to use an expensive component such as an isolator. The tuning circuits 141 to 14n are also composed of inexpensive parts. Therefore, the manufacturing cost of the radio circuit can be kept low.
[0024]
In addition, since only the tuning circuits 141 to 14n that perform proper impedance matching are selected and the output signal of the selected tuning circuit is transmitted from the antenna 14, impedance matching suitable for each designated frequency band is performed. It is possible to prevent degradation of performance as a wireless circuit such as IM characteristics, adjacent channel leakage power, and transmission efficiency.
[0025]
In the above description, the selection circuit 150 is provided in the subsequent stage of the tuning circuits 141 to 14n. However, only the tuning circuit selected by the selection circuit 150 is provided by providing the selection circuit 150 in the previous stage of the tuning circuits 141 to 14n. The impedance matching of the transmission signal may be performed.
[0026]
(Second Embodiment)
FIG. 2 is a diagram showing a schematic configuration of a radio circuit mounted on a mobile communication device or the like for explaining a second embodiment of the present invention. However, the same parts as those in the configuration shown in FIG.
[0027]
The configuration of the radio circuit 200 shown in FIG. 2 is substantially the same as that shown in FIG. 1 except that the n tuning circuits 141 to 14n are provided not on the antenna switching unit 13 but on the outside. For this reason, the operation of the radio circuit 200 is the same as that of the first embodiment and has the same effect. However, by providing the tuning circuits 141 to 14n outside the antenna switching unit 13, the constants of the tuning circuits 141 to 14n can be easily set. Therefore, it is possible to easily cope with the change of the frequency band of the transmission signal.
[0028]
In the first and second embodiments, one transmission / reception switch 131 has been described. However, the present invention can be similarly implemented even when there are a plurality of transmission / reception switches such as a dual band.
[0029]
【The invention's effect】
According to the present invention, an inexpensive wireless circuit having good performance can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a radio circuit mounted in a mobile communication device for explaining a first embodiment of the present invention. FIG. 2 is a mobile for explaining a second embodiment of the present invention. FIG. 3 is a diagram showing a schematic configuration of a radio circuit mounted on a communication apparatus. FIG. 3 is a diagram showing a schematic configuration of a radio circuit of a conventional mobile phone.
DESCRIPTION OF SYMBOLS 11 Power amplifier circuit 12 Directional coupler circuit 13 Antenna switching part 14 Antenna 15 Filter circuit 16 Low noise amplifier circuit 131 Transmission / reception switch 141-14n Tuning circuit 150 Selection circuit 151-15n Tuning switch D Detection terminal RX Reception terminal TX Transmission terminal

Claims (3)

A power amplifying circuit for amplifying a transmission signal;
A directional coupler having the output of the power amplifier circuit as an input;
A plurality of tuning circuits having different tuning frequencies for impedance matching of a transmission signal output from the directional coupler;
A selection circuit that selects any one of the plurality of tuning circuits according to the frequency of the transmission signal;
A radio circuit comprising: an antenna for transmitting a transmission signal output from a tuning circuit selected by the selection circuit. The radio circuit according to claim 1,
Comprising switching means for switching the antenna between a transmission system and a reception system;
The switching means incorporates the selection circuit,
The plurality of tuning circuits is a radio circuit arranged between the switching means and the directional coupler. The radio circuit according to claim 1,
Comprising switching means for switching the antenna between a transmission system and a reception system;
The switching means is a radio circuit including the plurality of tuning circuits and the selection circuit.

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