JP3585109B2 - High frequency coupling circuit - Google Patents

Description

【００１８】
図２は本発明の高周波結合回路の第２の実施形態を説明するための回路図である。この第２の実施形態では、共通ノードｃにアンテナに代えて第３高周波回路５１が接続され、高周波回路間に本発明の高周波結合回路２８が介在される。高周波結合回路２８の具体的構成は上記第１の実施形態と全く同一であり、切り替え回路４１で整合回路３１の形態を変えることにより、片方の高周波回路が動作するときと両方の高周波回路が動作するときの両方で整合回路の挿入損失を最適かつ最低の値とすることができる。
【００１９】
ただし、この第２の実施形態では、第１高周波回路２７１が常時動作する。したがって、ＣＰＵ１１は第２高周波回路２７２の動作／非動作を制御して、両方の高周波回路が動作する状態、片方の高周波回路が動作する状態に設定している。また、このように第２高周波回路２７２を制御するＣＰＵ出力を抵抗４７を介してＰＮＰトランジスタ４５のベースに供給して、第２高周波回路２７２の動作／非動作に対応してＰＮＰトランジスタ４５をオン／オフ制御することにより、上記第１の実施形態と同様に、両方の高周波回路が動作するときにＰＮＰトランジスタ４５をオン状態、片方の高周波回路が動作するときにＰＮＰトランジスタ４５をオフ状態に設定している。これにより切り替え回路４１および整合回路３１が上記第１の実施形態と同様に動作し、第１の実施形態と同様の効果を得ることができる。
【００２０】
なお、以上の実施形態は送信時を想定して説明したが、受信時は図１のアンテナ２９、図２の第３高周波回路５１側から信号が高周波結合回路２８を介して第１、第２高周波回路２７１，２７２に入力され、この第１、第２高周波回路２７１，２７２の出力がコンパンダＩＣ２６１，２６２に供給される。また、上記の実施の形態では、整合回路３１の抵抗３６と直列に挿入されるスイッチング素子としてダイオード４２を使用したが、高周波スイッチなどその他のスイッチング素子を使用することもできる。さらに、上記実施形態は、本発明の高周波結合回路をアナログコードレス電話機の親機に用いた場合であるが、本発明の高周波結合回路はその他の電子機器の高周波回路に対しても用いることができる。
【００２１】
【発明の効果】
以上詳細に説明したように本発明の高周波結合回路によれば、２つの高周波回路の片方が動作するときと両方が動作するときの両方で整合回路の挿入損失を最適かつ最低の値とすることができ、信号レベルに対する整合回路の影響を少なくすることができる。
【図面の簡単な説明】
【図１】本発明による高周波結合回路の第１の実施形態を示す回路図。
【図２】本発明による高周波結合回路の第２の実施形態を示す回路図。
【図３】本発明の高周波結合回路が使用されるコードレス電話機の親機を示すブロック図。
【図４】従来の整合回路の第１の例を示す回路図。
【図５】従来の整合回路の第２の例を示す回路図。
【符号の説明】
１１ ＣＰＵ
２７１，２７２ 第１、第２高周波回路
２８ 高周波結合回路
２９ アンテナ
３１ 整合回路
３２，３４，３７ コンデンサ
３３，３５ コイル
３６ 抵抗
４１ 切り替え回路
４２ ダイオード
４５ ＰＮＰトランジスタ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-frequency coupling circuit used for a high-frequency circuit of a home analog cordless telephone.
[0002]
[Prior art]
In a home analog cordless telephone equipped with two high-frequency circuits to communicate with two slave units and only one antenna, in order to transmit transmission output to the antenna efficiently, two high-frequency circuits are used. The outputs are commonly connected via a matching circuit and connected to one antenna.
[0003]
FIG. 4 is a circuit diagram showing a first example of a conventional matching circuit. In this figure, reference numeral 61 denotes a first high-frequency circuit, and 62 denotes a second high-frequency circuit. Each of the first and second high-frequency circuits 61, 62 has a compander IC 63, to which an audio signal and an MSK signal are input. 64 outputs are connected. The first high-frequency circuit 61 and the second high-frequency circuit 62 are controlled by the CPU 65 in a state in which one of them operates to communicate with one slave unit or a state in which both operate to communicate with two slave units. Is done. A matching circuit 67 is connected between the outputs of the first and second high-frequency circuits 61 and 62 and the common node c (the antenna 66 is connected to the common node c). The matching circuit 67 includes a capacitor 68 connected between the output of the first high-frequency circuit 61 and the ground, a coil 69 connected between the output of the first high-frequency circuit 61 and the common node c, and an output of the second high-frequency circuit 62. A capacitor 70 connected between the ground, a coil 71 connected between the output of the second high-frequency circuit 62 and the common node c, a resistor 72 connected between the output of the first high-frequency circuit 61 and the output of the second high-frequency circuit 62 , A capacitor 73 connected between the common node c and the ground. This matching circuit 67 is called a Wilkinson coupling (distribution) circuit and is well known.
[0004]
FIG. 5 is a circuit diagram showing a second example of the conventional matching circuit. This matching circuit 81 is the same as the circuit in which the resistor 72 is removed from the matching circuit 67 of FIG. 1, and is common to the output of the first high-frequency circuit 61 and the capacitor 68 connected between the ground and the output of the first high-frequency circuit 61. A coil 69 connected between the nodes c, a capacitor 70 connected between the output of the second high-frequency circuit 62 and the ground, a coil 71 connected between the output of the second high-frequency circuit 62 and the common node c, It comprises a capacitor 73 connected between the grounds. In FIG. 5 as well, outputs of compander ICs 63 and 64 are connected to respective inputs of the first and second high-frequency circuits 61 and 62, and the first and second high-frequency circuits 61 and 62 are controlled by the CPU 65. In order to communicate with one slave unit or two slave units, a state is set in which either one operates or a state in which both operate.
[0005]
[Problems to be solved by the invention]
However, in the matching circuit 67 of FIG. 4, the insertion loss is 3 dB in both the state where both the first and second high-frequency circuits 61 and 62 operate and the state where one of them operates. On the other hand, in the matching circuit 81 of FIG. 5, when only one of the high-frequency circuits operates, the insertion loss can be reduced to 1 to 2 dB. However, when both high-frequency circuits operate, the insertion loss becomes 5 to 6 dB. That is, in the matching circuits 67 and 81 in FIGS. 4 and 5, either one or both of the two high-frequency circuits operate, and the insertion loss is always larger than that of one of the matching circuits. Therefore, in the matching circuits 67 and 81 of FIGS. 4 and 5, the insertion loss cannot always be the optimum and lowest value when one of the two high-frequency circuits is operated and when both are operated. There is room for
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has a high frequency coupling that can make the insertion loss of a matching circuit an optimal and minimum value both when one of two high frequency circuits operates and when both operate. It is intended to provide a circuit.
[0007]
[Means for Solving the Problems]
The high-frequency coupling circuit of the present invention includes a pair of capacitors connected between each signal terminal of the first and second high-frequency circuits and ground, a pair of coils connected between each of the signal terminals and a common node, and A matching circuit including a capacitor connected between ground and a resistor connected between signal terminals of the first and second high-frequency circuits, and a switching element inserted in series with the resistor of the matching circuit; A switching circuit that turns off the switching element when one of the first and second high-frequency circuits operates, and turns on the switching element when both the first and second high-frequency circuits operate. And
[0008]
In the above configuration, a diode or a high-frequency switch can be used as the switching element. In addition, one antenna or a third high-frequency circuit is connected to the common node. Further, both the first and second high-frequency circuits can be selectively operated in one of the states, or one of the first and second high-frequency circuits is always in the operation state. In the latter case, on / off control of the switching element is performed according to the operation state and non-operation state of the other high-frequency circuit.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of a high-frequency coupling circuit according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 3 is a block diagram showing a base unit of an analog cordless telephone using the high-frequency coupling circuit of the present invention. The master device 10 has a CPU 11 for controlling the entire master device, and a dialer IC 25, an LCD display unit 13, and a hook switch 16 are connected to the CPU 11. The dialer IC 25 has a DP / DTMF transmission function and is connected to the key matrix 12. Here, the key matrix 12 has an answering key, a play key, a hands-free key, a registration key, a numeric keypad, and the like, and inputs various information. The LCD display unit 13 displays various information such as the telephone number of the received caller. Hook switch 16 determines whether or not the handset is installed on base unit 10.
[0010]
Reference numeral 17 denotes a line terminal to which an incoming detection circuit 18 for detecting a ringer signal is connected, and an output of the incoming detection circuit 18 is connected to the CPU 11. Reference numeral 19 denotes a rectifier circuit for preventing the inversion of the voltage polarity of the line terminal 17 from affecting the inside of the telephone, reference numeral 20 denotes a DP sending circuit for connecting / disconnecting the line, and reference numeral 21 denotes a speech network IC for performing 2-wire to 4-wire conversion. The line terminal 17 is connected to the CPU 11 via these circuits. A receiver 22, a microphone 23, a speaker 24, and a DSPIC 15 are connected to the speech network IC 21. The DSPIC 15 has recording / playback, hands-free, TONE / VOX detection, caller ID reception functions, Is also connected to the ROM 14. The ROM 14 stores various information such as the telephone number of the received sender, and also stores voice data such as a memory function as a telephone directory, a response message in the answering machine mode, and a received message from the sender.
[0011]
Further, the speech network IC 21 and the CPU 11 are connected to first and second high-frequency circuits 271 and 272 via compander ICs 261 and 262 in order to perform wireless communication with the slave unit. , 272 are connected to an antenna 29 via a high-frequency coupling circuit 28. The high-frequency coupling circuit 28 is connected to the CPU 11.
[0012]
FIG. 1 shows the CPU 11, the compander ICs 261, 262, the first and second high-frequency circuits 271, 272, the high-frequency coupling circuit 28, and the antenna 29 of FIG. 3, and a first embodiment of the high-frequency coupling circuit of the present invention will be described. FIG. In this figure, the operation state of the first and second high-frequency circuits 271 and 272 connected to the outputs of the compander ICs 261 and 262 to which the audio signal and the MSK signal are input is controlled by the CPU 11. That is, the first and second high-frequency circuits 271 and 272 are both controlled to a state in which only one operates or a state in which both operate.
[0013]
The high-frequency coupling circuit 28 according to the present invention connected to the outputs of the first and second high-frequency circuits 271 and 272 includes a matching circuit 31 and a switching circuit 41. The matching circuit 31 is connected between the output of the first high-frequency circuit 271 and the ground, and between the output of the first high-frequency circuit 271 and the common node c (the antenna 29 is connected to the common node c). The coil 33, the capacitor 34 connected between the output of the second high-frequency circuit 272 and the ground, the coil 35 connected between the output of the second high-frequency circuit 272 and the common node c, the output of the first high-frequency circuit 271 and the second It comprises a resistor 36 connected between the outputs of the high frequency circuit 272 and a capacitor 37 connected between the common node c and ground.
[0014]
On the other hand, the switching circuit 41 includes a diode 42 as a switching element, capacitors 43 and 44, a PNP transistor 45, and resistors 46, 47 and 48. The diode 42 has a cathode connected to one end of the resistor 36 of the matching circuit 31 (one end on the output side of the first high-frequency circuit 271), and is connected in series with the resistor 36. The capacitor 43 is connected between the anode of the diode 42 and the output of the first high-frequency circuit 271. The PNP transistor 45 has an emitter connected to the + B voltage, a base connected to the control output of the CPU 11 via the resistor 47, and a collector connected to the anode of the diode 42 via the resistor 46. The capacitor 44 is connected between the collector of the PNP transistor 45 and the ground. Further, a resistor 48 is connected between the other end of the resistor 36 of the matching circuit 31 (the output side of the second high-frequency circuit 272) and the ground.
[0015]
In such a configuration, when one of the first and second high-frequency circuits 271 and 272 is controlled to the operating state by the CPU 11, the PNP transistor control output of the CPU 11 becomes “H” level. Therefore, at this time, the PNP transistor 45 is turned off, and as a result, the diode 42 is also turned off. Therefore, when one of the first and second high-frequency circuits 271 and 272 is in operation, the resistor 36 connected between the outputs of the first and second high-frequency circuits 271 and 272 is connected between the outputs by the diode 42. Separated, the matching circuit 31 becomes the same as the conventional matching circuit shown in FIG. At this time, since one of the first and second high-frequency circuits 271 and 272 is operating, the insertion loss of the matching circuit 31 is 2 dB at the maximum.
[0016]
On the other hand, when both the first and second high-frequency circuits 271 and 272 are controlled to the operating state by the CPU 11, the PNP transistor control output of the CPU 11 becomes "L" level. Therefore, PNP transistor 45 is turned on. Then, the + B voltage is supplied to the anode of the diode 42 via the PNP transistor 45 and the resistor 46, so that the diode 42 is turned on. When the diode 42 is turned on, the resistor 36 is connected between the outputs of the first and second high-frequency circuits 271 and 272 via the diode 42. That is, when both the first and second high-frequency circuits 271 and 272 operate, the matching circuit 31 becomes the same as the conventional matching circuit shown in FIG. Therefore, the insertion loss of the matching circuit 31 is 3 dB.
[0017]
As described above, according to the high-frequency coupling circuit 28 of the present invention, the insertion loss of the matching circuit is 2 dB when one of the high-frequency circuits operates, and the insertion loss of the matching circuit is 3 dB when both the high-frequency circuits operate. obtain. Therefore, as can be seen from the comparison with the prior art in Table 1 below, according to the high-frequency coupling circuit 28 of the present invention, the insertion of the matching circuit is performed both when one of the two high-frequency circuits operates and when both operate. The loss can be optimal and lowest. It has been experimentally confirmed that the insertion loss of the matching circuit in the high-frequency coupling circuit 28 of the present invention has the above value.
[Table 1]

[0018]
FIG. 2 is a circuit diagram for explaining a high-frequency coupling circuit according to a second embodiment of the present invention. In the second embodiment, a third high frequency circuit 51 is connected to the common node c instead of the antenna, and the high frequency coupling circuit 28 of the present invention is interposed between the high frequency circuits. The specific configuration of the high-frequency coupling circuit 28 is exactly the same as that of the first embodiment, and the switching circuit 41 changes the form of the matching circuit 31 so that one of the high-frequency circuits operates and both of the high-frequency circuits operate. In both cases, the insertion loss of the matching circuit can be set to an optimum and minimum value.
[0019]
However, in the second embodiment, the first high-frequency circuit 271 always operates. Therefore, the CPU 11 controls the operation / non-operation of the second high-frequency circuit 272 so that both the high-frequency circuits operate and one of the high-frequency circuits operates. Further, the CPU output for controlling the second high-frequency circuit 272 is supplied to the base of the PNP transistor 45 via the resistor 47, and the PNP transistor 45 is turned on in response to the operation / non-operation of the second high-frequency circuit 272. In this manner, the PNP transistor 45 is turned on when both high-frequency circuits operate, and the PNP transistor 45 is turned off when one of the high-frequency circuits operates, as in the first embodiment. are doing. Thus, the switching circuit 41 and the matching circuit 31 operate in the same manner as in the first embodiment, and the same effects as in the first embodiment can be obtained.
[0020]
Although the above embodiment has been described assuming the time of transmission, at the time of reception, signals from the antenna 29 of FIG. 1 and the third high frequency circuit 51 of FIG. The signals are input to the high frequency circuits 271 and 272, and the outputs of the first and second high frequency circuits 271 and 272 are supplied to the compander ICs 261 and 262. In the above-described embodiment, the diode 42 is used as a switching element inserted in series with the resistor 36 of the matching circuit 31. However, other switching elements such as a high-frequency switch may be used. Furthermore, in the above embodiment, the high-frequency coupling circuit of the present invention is used for a base unit of an analog cordless telephone. However, the high-frequency coupling circuit of the present invention can be used for high-frequency circuits of other electronic devices. .
[0021]
【The invention's effect】
As described above in detail, according to the high-frequency coupling circuit of the present invention, the insertion loss of the matching circuit is set to the optimum and lowest value both when one of the two high-frequency circuits operates and when both operate. Therefore, the influence of the matching circuit on the signal level can be reduced.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a first embodiment of a high-frequency coupling circuit according to the present invention.
FIG. 2 is a circuit diagram showing a second embodiment of the high-frequency coupling circuit according to the present invention.
FIG. 3 is a block diagram showing a base unit of a cordless telephone using the high-frequency coupling circuit of the present invention.
FIG. 4 is a circuit diagram showing a first example of a conventional matching circuit.
FIG. 5 is a circuit diagram showing a second example of a conventional matching circuit.
[Explanation of symbols]
11 CPU
271, 272 First and second high-frequency circuits 28 High-frequency coupling circuit 29 Antenna 31 Matching circuits 32, 34, 37 Capacitors 33, 35 Coil 36 Resistor 41 Switching circuit 42 Diode 45 PNP transistor

Claims (6)

A pair of capacitors connected between each signal terminal of the first and second high-frequency circuits and ground, a pair of coils connected between each signal terminal and a common node, a capacitor connected between the common node and ground, A matching circuit comprising a resistor connected between signal terminals of the first and second high-frequency circuits;
The matching circuit has a switching element inserted in series with the resistor. When one of the first and second high-frequency circuits operates, the switching element is turned off, and both the first and second high-frequency circuits operate. A high frequency coupling circuit, comprising: a switching circuit for setting a switching element to ON when the switching is ON. The high frequency coupling circuit according to claim 1, wherein the switching element is a diode. The high frequency coupling circuit according to claim 1, wherein the switching element is a high frequency switch. The high-frequency coupling circuit according to claim 1, wherein one common antenna or a third high-frequency circuit is connected to the common node. 2. The high-frequency coupling circuit according to claim 1, wherein both the first and second high-frequency circuits selectively enter one operation state. 2. The high-frequency device according to claim 1, wherein one of the first and second high-frequency circuits is always in an operating state, and the switching element is turned on / off in accordance with an operating state and a non-operating state of the other high-frequency circuit. Coupling circuit.

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