Multi-band-high-frequency circuit, multi-band high-frequency circuit component and multi-band communication apparatus using same

A high-frequency circuit comprising a high-frequency switch circuit for switching the three-way connection of an antenna to a transmitting circuit for the first communications system, a receiving circuit for a first communications system, and a transmitting/receiving circuit for a second communications system; a first bandpass filter disposed between the antenna and the high-frequency switch circuit; and a balanced-unbalanced conversion circuit disposed between the receiving circuit of the first communications system and the high-frequency switch circuit.

FIELD OF THE INVENTION

The present invention relates to a wireless communications apparatus for performing wireless transmission between electronic or electric equipments, particularly to a high-frequency circuit commonly usable in at least two communications systems using substantially the same frequency band, a high-frequency device comprising such a high-frequency circuit, and a communications apparatus comprising such a high-frequency device.

BACKGROUND OF THE INVENTION

An industrial, scientific and medical (ISM) band at 2.4 GHz is used in wireless LAN (WLAN) communications according to the IEEE 802.11 standard, such as direct sequence spread spectrum (DSSS) wireless communications, etc. Also proposed is a short-distance wireless standard Bluetooth™, an extremely convenient technology capable of making connection between associated electronic equipments without using a cable, in an ISM band of 2.4 GHz, the same as in the wireless LAN (WLAN).

A major wireless LAN standard utilizing an ISM band of 2.4 GHz has IEEE 802.11b and IEEE 802.11g. The IEEE 802.11b is a DSSS system, supporting high-speed communications at 5.5 Mbps and 11 Mbps. The IEEE 802.11g uses an orthogonal frequency division multiplex (OFDM) modulation system, supporting high-speed data communications at 54 Mbps at maximum.

Bluetooth divides the ISM frequency band of 2.4 GHz to pluralities of wireless channels, each of which is then divided by a unit time ( 1/1600 seconds) to time slots. The wireless channels used are switched by the time slots to provide a frequency-hopping system with excellent noise resistance.

Wireless LAN utilized by small groups in a short distance range within about 50-100 m has such a high data transmission speed as several Mbps to several tens of Mbps, consuming power of about 100 mW. In Bluetooth utilized in a relatively narrow area such as the same compound or building, etc., however, the reach of electromagnetic waves is as short as about 10 m, and its transmission speed is 2 Mbps at most, with as small power consumption as about 10 mW. Because wireless LAN and Bluetooth are different in transmission speed and reach, etc., both of them may be used in one communications apparatus, so that a more advantageous one is used depending on applications.

Explanation will be made below, for instance, with wireless LAN (IEEE 802.11b, IEEE 802.11g) as a first communications system, and Bluetooth as a second communications system.

JP2001-24579 A discloses a circuit usable for both circuits of wireless LAN and Bluetooth, which comprises a first switch circuit for switching the connection of a first antenna port to a transmitting circuit for a first communications system and a second switch circuit, the second switch circuit switching the connection of the receiving circuit of the first communications system to the first switch circuit and a third switch circuit, the third switch circuit switching the connection of the second antenna port to a transmitting/receiving circuit for the second communications system and the second switch circuit; a first filter disposed between the first switch circuit and a transmitting circuit for the first communications system; and a second filter disposed between the second switch circuit and the receiving circuit of the first communications system, as shown inFIG. 35.

With the circuit described in JP2001-24579 A, however, the miniaturization of communications apparatuses is difficult, (a) because it needs two filters, a first filter between the first switch circuit and the transmitting circuit for the first communications system, and a second filter between the second switch circuit and the receiving circuit of the first communications system, and (b) because the receiving circuit of the first communications system is constituted such that it is connected to the first and second antenna ports, resulting in a complicated circuit.

JP2002-208874 A discloses composite wireless device using substantially the same frequency band, which comprises a first splitter for inputting first and second outputs, a power amplifier for inputting the output of the first splitter, an antenna switch for inputting the output of the power amplifier, a low-noise amplifier on the receiving side of the antenna switch, and a second splitter for inputting the output of the low-noise amplifier, the transmitting circuit having such a structure that an output one of different two transmitting signals is selected by the first splitter and then amplified by the power amplifier, and the receiving circuit having such a structure that received waves are distributed to two signals by the second splitter disposed on the output side of the low-noise amplifier, as shown inFIG. 36. In this composite wireless device, the power amplifier and the low-noise amplifier are used for both signals. Specifically, the power amplifier is used for both the transmitting waves of wireless LAN and the transmitting waves of Bluetooth. However, because recent Bluetooth having low transmitting output power does not need a power amplifier, such common use has become unnecessary.

OBJECTS OF THE INVENTION

Accordingly, an object of the present invention is to provide a high-frequency circuit capable of being used for both wireless LAN and Bluetooth, particularly to a high-frequency circuit that can be miniaturized because of a small number of parts, and a high-frequency circuit device and a communications apparatus comprising such a high-frequency circuit.

DISCLOSURE OF THE INVENTION

The first high-frequency circuit of the present invention, which is disposed between an antenna capable of transmitting and receiving in at least two different communications systems and transmitting/receiving circuits for at least two different communications systems, comprises a high-frequency switch circuit for switching the three-way connection of the antenna to the transmitting circuit and receiving circuit of the first communications system, and the transmitting/receiving circuit of the second communications system; a first bandpass filter disposed between the antenna and the high-frequency switch circuit; and a balanced-unbalanced conversion circuit disposed between the receiving circuit of the first communications system and the high-frequency switch circuit.

In the first high-frequency circuit, a balanced-unbalanced conversion circuit is preferably disposed between the transmitting/receiving circuit for the second communications system and the high-frequency switch circuit.

The second high-frequency circuit of the present invention, which is disposed between an antenna capable of transmitting and receiving in at least two different communications systems and transmitting/receiving circuits for at least two different communications systems, comprises: a high-frequency switch circuit for switching the three-way connection of the antenna to a transmitting circuit for the first communications system, a transmitting circuit for the second communications system, and a receiving circuit for both of the first and second communications systems; a first bandpass filter disposed between the antenna and the high-frequency switch circuit; a splitter or coupler circuit disposed in a path connected to both circuits for splitting or branching a received signal to the receiving circuit for the first communications system and the receiving circuit for the second communications system; and a balanced-unbalanced conversion circuit disposed between the splitter or coupler circuit and the receiving circuit for the first communications system.

In the second high-frequency circuit, a balanced-unbalanced conversion circuit is preferably disposed between the splitter or coupler circuit and the receiving circuit for the second communications system, and a balanced-unbalanced conversion circuit is preferably disposed between the transmitting circuit for the second communications system and the high-frequency switch circuit.

The third high-frequency circuit of the present invention, which is disposed between an antenna capable of transmitting and receiving in at least two different communications systems and transmitting/receiving circuits for at least two different communications systems, comprises a high-frequency switch circuit for switching the two-way connection of the antenna to a transmitting circuit for the first communications system, and a path connected to both of a receiving circuit for the first communications system and a transmitting/receiving circuit for the second communications system; a first bandpass filter disposed between the antenna and the high-frequency switch circuit; and a splitter or coupler circuit disposed in the path connected to both of the receiving circuit for the first communications system and the transmitting/receiving circuit for the second communications system to split or branch a signal to both circuits.

In the third high-frequency circuit, a balanced-unbalanced conversion circuit is preferably disposed between the splitter or coupler circuit and the receiving circuit for the first communications system, and a balanced-unbalanced conversion circuit is preferably disposed between the splitter or coupler circuit and the transmitting/receiving circuit for the second communications system.

The fourth high-frequency circuit, which is disposed between an antenna capable of transmitting and receiving in at least two different communications systems and transmitting/receiving circuits for at least two different communications systems, comprises a high-frequency switch circuit for switching the two-way connection of the antenna to a transmitting circuit for the first communications system and a receiving circuit for the first communications system; a first bandpass filter disposed between the antenna and the high-frequency switch circuit; and a splitter or coupler circuit disposed between the first bandpass filter and the high-frequency switch circuit, or between the first bandpass filter and the antenna to split or branch a signal to the transmitting/receiving circuit for the second communications system.

In the fourth high-frequency circuit, a balanced-unbalanced conversion circuit is preferably disposed between the receiving circuit for the first communications system and the high-frequency switch circuit, and a balanced-unbalanced conversion circuit is preferably disposed between the transmitting/receiving circuit for the second communications system and the splitter or coupler circuit.

In each of the first to fourth high-frequency circuits, a high-frequency power amplifier circuit is preferably disposed between the transmitting circuit for the first communications system and the high-frequency switch circuit, and a second bandpass filter is preferably disposed between the high-frequency power amplifier circuit and the transmitting circuit for the first communications system. Further, a balanced-unbalanced conversion circuit is preferably disposed between the transmitting circuit for the first communications system and the high-frequency power amplifier circuit.

The high-frequency circuit device of the present invention having the above high-frequency circuit is constituted by a laminate of dielectric ceramics and electrode patterns, and at least one semiconductor element mounted on the laminate; (a) the electrode patterns constituting at least part of inductance elements and/or capacitance elements, which mainly constitute (1) at least one of the first bandpass filter and the balanced-unbalanced conversion circuit, (2) at least one of the first bandpass filter and the splitter or coupler circuit, or (3) at least one of the first bandpass filter, the balanced-unbalanced conversion circuit and the splitter or coupler circuit, and (b) the semiconductor elements constituting (1) the high-frequency switch circuit, or (2) the high-frequency switch circuit and/or the high-frequency power amplifier circuit.

When the second bandpass filter is used, it is preferably constituted by the electrode patterns in the laminate.

Although the inductance elements and/or capacitance elements for the circuits may be constituted by electrode patterns in the laminate or mounted on the laminate, they are preferably disposed in the laminate for the miniaturization of the high-frequency circuit device and the reduction of the number of parts.

The high-frequency switch circuit may be structured as one semiconductor element and mounted on the laminate. Alternatively, the high-frequency switch circuit may be constituted by semiconductor elements, and inductance elements and/or capacitance elements, with at least part of the inductance elements and/or the capacitance elements formed by electrode patterns in the laminate.

A semiconductor element constituting the high-frequency power amplifier circuit may be mounted on the laminate, and its control power source circuit, a matching circuit, etc. may be constituted by inductance elements, capacitance elements and/or resistance elements, with at least part of the inductance elements and/or the capacitance elements formed in the laminate.

In addition to the high-frequency power amplifier circuit, resistance elements may be used and mounted on the laminate.

The communications apparatus of the present invention comprises any one of the above high-frequency circuits, or any one of the above high-frequency circuit devices. The communications apparatus of the present invention are personal computers (PCs), PC peripherals such as PCMCIA cards, printers, hard disk drives and broadband rooters, FAXs, refrigerators, standard-definition televisions (SDTVs), high-definition televisions (HDTVs), digital cameras, digital video cameras, mobile phones, etc.

DESCRIPTION OF THE BEST MODE OF THE INVENTION

The embodiments of the present invention will be explained in detail referring to the attached drawings, but the structure explained with respect to each embodiment is not restrictive thereto but may be applied to other embodiments, if necessary.

FIG. 1shows the circuit of a communications apparatus usable for both wireless LAN and Bluetooth according to an embodiment of the present invention. Taking for example a case where a first communications system is wireless LAN usable for IEEE 802.11b and/or IEEE 802.11g, and a second communications system is Bluetooth, explanation will be made below. In the figure, the same reference numerals are assigned to parts with the same or similar functions. Accordingly, the same reference numerals do not necessarily mean completely the same parts.

The high-frequency circuit shown inFIG. 1comprises an antenna ANT capable of transmitting and receiving in wireless LAN and Bluetooth, a high-frequency switch circuit1for switching the three-way connection of the antenna ANT to a transmitting circuit11bg-T of wireless LAN, a receiving circuit11bg-R of wireless LAN, and a transmitting/receiving circuit BLT-TR of Bluetooth, a first bandpass filter2disposed between the antenna ANT and the high-frequency switch circuit1, a balanced-unbalanced conversion circuit3disposed between the receiving circuit11bg-R of wireless LAN and the high-frequency switch circuit1, a high-frequency power amplifier circuit6disposed between the transmitting circuit11bg-T of wireless LAN and the high-frequency switch circuit1, and a second bandpass filter7disposed between the transmitting circuit11bg-T of wireless LAN and the high-frequency power amplifier circuit6.

In the high-frequency circuit in this embodiment, a bandpass filter that was necessary between the high-frequency power amplifier circuit6and the antenna ANT to suppress harmonics and thermal noise from the high-frequency power amplifier circuit6, a bandpass filter that was necessary between the antenna ANT and the balanced-unbalanced conversion circuit3to suppress signal components other than a received signal to enhance the receiving sensitivity, and a bandpass filter that was necessary between the antenna ANT and the transmitting/receiving circuit BLT-TR of Bluetooth are integrated into one first bandpass filter2, through which the transmitting and receiving signals of wireless LAN and the transmitting and receiving signals of Bluetooth pass, between the high-frequency switch circuit1and the antenna ANT. Thus, it has a simplified circuit structure. To suppress noise generated from the transmitting circuit11bg-T of wireless LAN, a second bandpass filter7may be disposed, if necessary, between the transmitting circuit11bg-T of wireless LAN and the high-frequency power amplifier circuit6. Also, the arrangement of a balanced-unbalanced conversion circuit3in a path between the high-frequency switch circuit1and the receiving circuit11bg-R of wireless LAN has the circuit balanced to improve the noise resistance of the receiving circuit11bg-R of wireless LAN, without increasing loss in a path between the antenna ANT and the transmitting circuit11bg-T of wireless LAN, and in a path between antenna ANT and the transmitting/receiving circuit BLT-TR of Bluetooth.

To turn the transmitting/receiving circuit BLT-TR of Bluetooth needing small signal-transmitting power to a balanced circuit, without increasing loss in a path for the transmitting signal of wireless LAN between the antenna ANT and the transmitting circuit11bg-T of wireless LAN, a balanced-unbalanced conversion circuit4need only be disposed between the transmitting/receiving circuit BLT-TR of Bluetooth and the high-frequency switch circuit1, as shown inFIG. 2.

FIG. 3shows a high-frequency circuit according to another embodiment of the present invention, which may be contained in a communications apparatus usable for both wireless LAN and Bluetooth. This high-frequency circuit comprises a high-frequency switch circuit1for switching the three-way connection of an antenna ANT capable of transmitting and receiving signals of wireless LAN and Bluetooth to a transmitting circuit11bg-T of wireless LAN, a transmitting circuit BLT-T of Bluetooth, and a connecting point P1of a receiving circuit of wireless LAN and a receiving circuit of Bluetooth, a first bandpass filter2disposed between the antenna ANT and the high-frequency switch circuit1, a splitter circuit9disposed between the connecting point P1and the receiving circuit11bg-R of wireless LAN and the receiving circuit BLT-R of Bluetooth, a balanced-unbalanced conversion circuit3disposed between the receiving circuit11bg-R of wireless LAN and the splitter circuit9, a balanced-unbalanced conversion circuit4disposed between the receiving circuit BLT-R of Bluetooth and the splitter circuit9, a high-frequency power amplifier circuit6disposed between the transmitting circuit11bg-T of wireless LAN and the high-frequency switch circuit1, and a second bandpass filter7disposed between the transmitting circuit11bg-T of wireless LAN and the high-frequency power amplifier circuit6.

In the high-frequency circuit shown inFIG. 3, a bandpass filter that was necessary between the high-frequency power amplifier circuit6and the antenna ANT to suppress harmonics and thermal noise generated from the high-frequency power amplifier circuit6, a bandpass filter that was necessary between the antenna ANT and the balanced-unbalanced conversion circuit3to suppress signal components other than a received signal to enhance the receiving sensitivity, a bandpass filter that was necessary between the antenna ANT and the balanced-unbalanced conversion circuit4to suppress signal components other than a received signal to enhance the receiving sensitivity, and a bandpass filter that was necessary between the transmitting circuit BLT-T of Bluetooth and the antenna ANT to suppress harmonics and thermal noise generated from the transmitting circuit BLT-T of Bluetooth are integrated into one first bandpass filter2, through which the transmitting and receiving signals of wireless LAN and the transmitting and receiving signals of Bluetooth pass, between the high-frequency switch circuit1and the antenna ANT. Thus, it has a simplified circuit structure.

To suppress noise from the transmitting circuit11bg-T of wireless LAN, a second bandpass filter7may be disposed between the transmitting circuit11bg-T of wireless LAN and the high-frequency power amplifier circuit6. Also, the arrangement of the splitter circuit9at P1common to the receiving circuit of wireless LAN and the receiving circuit of Bluetooth makes it possible to receive both signals for wireless LAN and Bluetooth. In addition, when the balanced-unbalanced conversion circuit3is arranged between the high-frequency switch circuit1and the receiving circuit11bg-R of wireless LAN, and when the balanced-unbalanced conversion circuit4is arranged between the high-frequency switch circuit1and the receiving circuit BLT-R of Bluetooth, the circuit can be turned to a balanced circuit providing the receiving circuit11bg-R of wireless LAN and the receiving circuit BLT-R of Bluetooth with improved noise resistance, without increasing loss in the path between the antenna ANT and the transmitting circuit11bg-T of wireless LAN, and in the path between the antenna ANT and the transmitting circuit BLT-T of Bluetooth.

To turn the transmitting circuit BLT-T of Bluetooth needing small signal-transmitting power to a balanced circuit without increasing loss in a path between the antenna ANT and the transmitting circuit11bg-T of wireless LAN for transmitting signals of wireless LAN, a balanced-unbalanced conversion circuit5need only be disposed between the transmitting circuit BLT-T of Bluetooth and the high-frequency switch circuit1, as shown inFIG. 4.

FIG. 5shows a high-frequency circuit according to another embodiment of the present invention, which is contained in a communications apparatus usable for both wireless LAN and Bluetooth. This high-frequency circuit comprises an antenna ANT capable of transmitting and receiving signals of wireless LAN and Bluetooth, a high-frequency switch circuit1for switching the two-way connection of the antenna ANT to a transmitting circuit11bg-T of wireless LAN, and a connecting point P1of a receiving circuit11bg-R of wireless LAN and a transmitting/receiving circuit BLT-TR of Bluetooth, a first bandpass filter2disposed between the antenna ANT and the high-frequency switch circuit1, and a splitter circuit9disposed between the connecting point P1and the receiving circuit11bg-R of wireless LAN and the transmitting/receiving circuit BLT-TR of Bluetooth. A balanced-unbalanced conversion circuit3is disposed between the receiving circuit11bg-R of wireless LAN and the splitter circuit9, and a balanced-unbalanced conversion circuit4is disposed the transmitting/receiving circuit BLT-TR of Bluetooth and the splitter circuit9. A high-frequency power amplifier circuit6is disposed between the transmitting circuit11bg-T of wireless LAN and the high-frequency switch1.

In the high-frequency circuit shown inFIG. 5, a bandpass filter that was necessary between the high-frequency power amplifier circuit6and the antenna ANT to suppress harmonics and thermal noise generated from the high-frequency power amplifier circuit6, a bandpass filter that was necessary between the antenna ANT and the balanced-unbalanced conversion circuit3to suppress signal components other than a received signal to enhance the receiving sensitivity, and a bandpass filter that was necessary between the antenna ANT and the transmitting/receiving circuit BLT-TR of Bluetooth are integrated into the first bandpass filter2, through which the transmitting signal of wireless LAN, the received signal of wireless LAN and the transmitting/receiving signals of Bluetooth pass, between the high-frequency switch1and the antenna ANT. Thus, it has a simplified circuit structure.

The arrangement of the balanced-unbalanced conversion circuit3between the splitter circuit9and the receiving circuit11bg-R of wireless LAN is adapted to a balanced circuit for improving the noise resistance of the receiving circuit11bg-R of wireless LAN, without increasing loss in a path between the antenna ANT and the transmitting circuit11bg-T of wireless LAN.

To turn the transmitting/receiving circuit BLT-TR of Bluetooth needing a small signal-transmitting power to a balanced circuit without increasing loss in path a between the antenna ANT and the transmitting circuit11bg-T of wireless LAN, a balanced-unbalanced conversion circuit4need only be disposed between the transmitting/receiving circuit BLT-TR of Bluetooth and the splitter circuit9.

Because the high-frequency circuit shown inFIG. 5is branched by the splitter circuit9to the receiving circuit11bg-R of wireless LAN and the transmitting/receiving circuit BLT-TR of Bluetooth, it can simultaneously receive signals of wireless LAN and Bluetooth. A coupler circuit may be used in place of the splitter circuit9. Even when the coupler circuit is used, the signals of wireless LAN and Bluetooth can be simultaneously received. In the case of using the coupler circuit, a distribution ratio of the receiving circuit11bg-R of wireless LAN to the transmitting/receiving circuit BLT-TR of Bluetooth can be changed to, for instance, 5:1 or 10:1, to properly set the ratio of the signal of Bluetooth to the signal of wireless LAN. For instance, the minimum receiving sensitivity at a short distance is −70 dBm in Bluetooth, much lower than −65 dBm in wireless LAN. Accordingly, the simultaneous receiving of the signal of wireless LAN and the signal of Bluetooth can be efficient conducted by distributing less signals to the receiving circuit of Bluetooth needing only small power and more signals to the receiving circuit of wireless LAN needing large power, using the coupler circuit.

The balanced-unbalanced conversion circuit4between the transmitting/receiving circuit BLT-TR of Bluetooth and the splitter circuit9may be omitted as shown inFIG. 6, and a balanced-unbalanced conversion circuit12may be disposed between the transmitting circuit11bg-T of wireless LAN and the high-frequency power amplifier circuit6as shown inFIG. 7. The balanced-unbalanced conversion circuit12causes a terminal for the transmitting circuit11bg-T of wireless LAN to act as a balance terminal, thereby making it adaptable to a balanced circuit for the improvement of noise resistance. As shown inFIG. 8, a bandpass filter7may be disposed between the transmitting circuit11bg-T of wireless LAN and the high-frequency power amplifier circuit6. With the band filter7, local signal noise generated from the transmitting circuit of RF-IC for wireless LAN can be removed. It is noted that the addition and combination of these circuit elements can be properly modified.

FIG. 9shows a high-frequency circuit according to a still further embodiment of the present invention, which is contained in a communications apparatus usable for both wireless LAN and Bluetooth. This high-frequency circuit comprises an antenna ANT capable of transmitting and receiving signals of wireless LAN and Bluetooth, a high-frequency switch circuit1for switching the two-way connection of the antenna ANT to transmitting and receiving circuits11bg-T,11bg-R of wireless LAN, a first bandpass filter2disposed between the antenna ANT and the high-frequency switch circuit1, a coupler circuit11disposed between the high-frequency switch circuit1and the first bandpass filter2and connected to a transmitting/receiving circuit BLT-TR of Bluetooth, a balanced-unbalanced conversion circuit3disposed between the receiving circuit11bg-R of wireless LAN and the high-frequency switch circuit1, and a high-frequency power amplifier circuit6disposed between the transmitting circuit11bg-T of wireless LAN and the high-frequency switch circuit1.

In the high-frequency circuit shown inFIG. 9, a bandpass filter that was necessary between the high-frequency power amplifier circuit6and the antenna ANT to suppress harmonics and thermal noise generated from the high-frequency power amplifier circuit6, a bandpass filter that was necessary between the antenna ANT and the balanced-unbalanced conversion circuit3to suppress signal components other than a received signal to enhance the receiving sensitivity, and a bandpass filter that was necessary between the antenna ANT and the transmitting/receiving circuit BLT-TR of Bluetooth are integrated into one first bandpass filter2between the high-frequency switch1and the antenna ANT. Thus, it has a simplified circuit structure.

The arrangement of the balanced-unbalanced conversion circuit3between the high-frequency switch circuit1and the receiving circuit11bg-R of wireless LAN makes the receiving circuit11bg-R adaptable to a balanced circuit for improving the noise resistance of the receiving circuit11bg-R of wireless LAN, without increasing loss in a path between the antenna ANT and the transmitting circuit11bg-T of wireless LAN.

Although the coupler circuit11is disposed between the high-frequency switch circuit1and the first bandpass filter2inFIG. 9, it may be disposed between the antenna ANT and the first bandpass filter2, and a splitter circuit may be used in place of the coupler circuit11. Thus, the arrangement of a circuit branching to the transmitting/receiving circuit BLT-TR of Bluetooth in an antenna top portion upstream of the high-frequency switch circuit1makes it possible to simultaneously perform the transmitting and receiving of signals for both communications systems of wireless LAN and Bluetooth, without increasing the number of antennas. The connection of the antenna ANT to the transmitting/receiving circuit BLT-TR of Bluetooth does not need a new switch circuit, thereby avoiding increase in the number of switch control circuits. Further, in the case of using the coupler circuit, as described above, the ratio of the signal of Bluetooth to the signal of wireless LAN can be properly set by changing the distribution ratio of the circuit of wireless LAN to the circuit of Bluetooth. Because the minimum receiving sensitivity is −70 dBm in Bluetooth, much lower than −65 dBm in wireless LAN, the coupler circuit can distribute less signal to the circuit of Bluetooth needing only small power and more signal to the circuit of wireless LAN needing large power to conduct efficient transmission and receiving of signals.

When the transmitting/receiving circuit BLT-TR of Bluetooth needing small signal-transmitting power is made to a balanced circuit, a balanced-unbalanced conversion circuit4may be disposed between the transmitting/receiving circuit BLT-TR of Bluetooth and the coupler circuit11as shown inFIG. 10.

When a balanced-unbalanced conversion circuit is disposed between the transmitting circuit11bg-T of wireless LAN and the high-frequency power amplifier circuit6, and when a terminal for the transmitting circuit11bg-T of wireless LAN is used as a balance terminal, a balanced circuit with improved noise resistance can be obtained. Also, when a bandpass filter is disposed between the transmitting circuit11bg-T of wireless LAN and the high-frequency power amplifier circuit6, noise from the transmitting circuit11bg-T of wireless LAN can be removed. It is noted that the addition and combination of these circuit elements may be properly modified.

FIG. 11shows the equivalent circuit of a high-frequency circuit ofFIG. 1. The first bandpass filter2is disposed between the antenna port ANT and the high-frequency switch circuit1, and constituted by magnetically coupled inductance elements Lp1, Lp2and capacitance elements Cp1, Cp2, Cp3, Cp4, Cp5, Cp6, Cp1. The first bandpass filter2attenuates harmonics generated from the high-frequency power amplifier6or the high-frequency switch circuit1when transmitting, and attenuates signals outside the frequencies used for receiving in wireless LAN and Bluetooth when receiving.

The balanced-unbalanced conversion circuit3is connected to the high-frequency switch circuit1via a matching circuit Lbb. The matching circuit Lbb, which is necessary for matching between the bandpass filter2and the balanced-unbalanced conversion circuit3, is not restricted to the depicted arrangement, but may be disposed between the high-frequency switch circuit1and the bandpass filter2. Part of the balanced-unbalanced conversion circuit3on the side of the high-frequency switch circuit1is an unbalanced circuit constituted by inductance elements Lb1a, Lb1b, and the other part of the balanced-unbalanced conversion circuit3on the side of the receiving circuits11bg-R+,11bg-R− of wireless LAN is a balanced circuit constituted by inductance elements Lb2, Lb3and a capacitance element Cb1. Signals ideally having the same amplitude with 180° phase difference are output from the receiving circuits11bg-R+ and11bg-R− of wireless LAN. A capacitance element Cb1which looks short-circuited at a high frequency is disposed between the connecting point of the inductance elements Lb2and Lb3and the ground, DC voltage is applied from a DC(NC) port, and DC voltage can be output from a11bg-R+port and a11bg-R− port. The balanced-unbalanced conversion circuit3may be provided with an impedance-converting function.

Disposed between the high-frequency switch circuit1and the transmitting circuit11bg-T of wireless LAN are a detection circuit8for monitoring power output from a high-frequency power amplifier circuit6, the high-frequency power amplifier circuit6for amplifying the power of the transmitting signal from the transmitting circuit11bg-T of wireless LAN, and a second bandpass filter7comprising magnetically coupled inductance elements Lt1, Lt2and capacitance elements Ct1, Ct2, Ct3, Ct4, Ct5, Ct6, in this order from the side of the high-frequency switch circuit1. The second bandpass filter7attenuates signals outside the frequencies of the transmitting signal of wireless LAN inputted from the transmitting circuit11bg-T of wireless LAN.

FIGS. 12-16exemplify the equivalent circuits of the high-frequency switches1. These high-frequency switch circuits1are depicted by usual symbols with their explanation omitted. They are mainly constituted by switching elements such as field-effect transistors (FETs), diodes, etc., properly with inductance elements including transmission lines, and capacitance elements.

In the high-frequency switch circuits1shown inFIGS. 12 and 13, as shown in Table 1, ports are connected by voltage applied to the control terminals V1, V2, V3. In Table 1, “High” represents voltage in a range of 2.5-4 V, and “Low” represents voltage in a range of 0-0.5 V.

When isolation is insufficient between the transmitting circuit11bg-T of wireless LAN and the transmitting/receiving circuit BLT-TR of Bluetooth in the high-frequency switch circuits shown inFIGS. 12 and 13, high-frequency switch circuits for switching two paths may be connected in series to improve the isolation, thereby constituting the high-frequency switch circuits1. Examples of such high-frequency switch circuits1are shown inFIGS. 14-16. In the high-frequency switch circuit1shown inFIG. 14, ports are connected by voltage applied to control terminals V1-V4as shown in Table 2. In the high-frequency switch circuit1shown inFIG. 15, ports are connected by voltage applied to control terminals V1and V3as shown in Table 3. In the high-frequency switch circuit1shown inFIG. 16, ports are connected by voltage applied to control terminals V1, V2and V3as shown in Table 4.

When isolation is insufficient between the transmitting circuit11bg-T of wireless LAN and the receiving circuit11bg-R of wireless LAN in the high-frequency switch circuits1shown inFIGS. 14-16, switch circuits for turning on or off one path may be disposed in series or in a grounded manner in a path between a terminal1cconnected to the receiving circuit11bg-R of wireless LAN and a terminal1aconnected to the antenna to improve the isolation.FIG. 17shows an example in which a PIN diode is connected between a terminal1cand the ground. In the high-frequency switch circuit1shown inFIG. 17, ports are connected by voltage applied to control terminals V1, V2, V3, V4as shown in Table 2.

FIG. 18shows one example of the equivalent circuits of the high-frequency power amplifier circuit6connected between the transmitting circuit11bg-T of wireless LAN and the detection circuit8. The high-frequency power amplifier circuit6comprises an input-matching circuit61, a power amplifier circuit62having two-stage transistors, a voltage supply circuit63for supplying a constant voltage, a bias control circuit64for controlling the output power of the high-frequency power amplifier circuit6, and an output-matching circuit65. Inductance elements and capacitance elements are used in the circuits61-65. The circuits61-65may be constituted by a microwave monolithic integrated circuit (MMIC).

FIG. 19shows one example of the equivalent circuits of the detection circuit8connected between the high-frequency switch circuit1and the high-frequency power amplifier circuit6. The detection circuit8comprises a directional coupler81comprising a main line, a sub-line and a resistance element, a matching circuit82comprising a grounded inductance element and a phase circuit, a resistance element83, a Schottky diode84, and a voltage-smoothing circuit85comprising a resistance element and a capacitor element. The coupler81may be constituted by capacitors, and the matching circuit82may be constituted by a phase circuit. DC voltage corresponding to the output power of the high-frequency power amplifier circuit6is output from Vdet. The detection circuit8may be integrated with the high-frequency power amplifier circuit6.

FIG. 20shows the equivalent circuit of a portion10(corresponding to the high-frequency circuit device) encircled by a broken line in the high-frequency circuit shown inFIG. 5. The first bandpass filter2disposed between the antenna port ANT and the high-frequency switch circuit1comprises magnetically coupled inductance elements lrb1, lrb2, and capacitance elements crb1, crb2, crb4, crb5, crb6, crb7. Connected to the first bandpass filter2on the side of the antenna port ANT is a highpass filter2bcomprising an inductance element lh1and capacitance elements ch1, ch3. The highpass filter2b, which attenuates signals outside the passband of the first bandpass filter2, may be regarded as a bandpass filter comprising the highpass filter2band the first bandpass filter2. The highpass filter2band the first bandpass filter2attenuate harmonics generated from the high-frequency power amplifier6or the high-frequency switch circuit1during transmission, and attenuate signals outside the frequencies used in wireless LAN and Bluetooth during receiving.

The bandpass filter2is connected to the high-frequency switch circuit1of SPDT. The first path of the high-frequency switch circuit1is connected to the high-frequency power amplifier circuit6, which is connected to the transmitting circuit11bg-T of wireless LAN via a capacitance element ct.

The second path of the high-frequency switch circuit1is connected to the splitter circuit9comprising inductance elements lsp1, lsp2, a resistance element rsp and a capacitance element csp1, via a capacitance element cs. The splitter circuit9distributes signals to the receiving circuit11bg-R of wireless LAN and the transmitting/receiving circuit BLT-TR of Bluetooth. Connected via the matching circuit lb2to the splitter circuit9on the side of the receiving circuit11bg-R of wireless LAN is a balanced-unbalanced conversion circuit3having balance terminals11bg-R+,11bg-R−. The balanced-unbalanced conversion circuit3comprises inductance elements lb3, lb6, lb11, lb15and a capacitance element cb2. Apart of the balanced-unbalanced conversion circuit3on the side of the receiving circuit11bg-R of wireless LAN is a balanced circuit, balance terminals11bg-R+,11bg-R− of which output signals ideally having the same amplitude with a 180° phase difference. Disposed between the connecting point of the inductance elements lb11and lb15and the ground is a capacitance element cb2, which looks short-circuited in high frequencies. However, a DC port for applying DC voltage to the connecting point may output DC voltage from its balance terminals11bg-R+,11bg-R−. The balanced-unbalanced conversion circuit3may be provided with an impedance-converting function.

Connected via the matching circuit lb21to the splitter circuit9on the side of the transmitting/receiving circuit BLT-TR of Bluetooth is a balanced-unbalanced conversion circuit4having balance terminals BLT-TR+, BLT-TR−. The balanced-unbalanced conversion circuit4comprises inductance elements lb22, lb26, lb31, lb36and a capacitance element cb3.

FIGS. 21-23show the equivalent circuits of the high-frequency switch circuits1. These high-frequency switches1are depicted by usual symbols, with their explanation omitted. They comprise switching elements such as field-effect transistors (FET), diodes, etc. as main components, with proper inductance elements including transmitting lines, and capacitance elements.

In the high-frequency switches1shown inFIGS. 21 and 22, ports are connected by voltage applied from control terminals Vc1, Vc2, as shown in Table 5. In the high-frequency switch1shown inFIG. 23, ports are connected by voltage applied from a control terminal Vc1, as shown in Table 6. In Tables 5 and 6, “High” represents voltage in a range of 2.5-4 V, and “Low” represents voltage in a range of 0-0.5 V.

FIG. 24shows one example of the equivalent circuits of the high-frequency power amplifier circuit6. The high-frequency power amplifier circuit6comprises an input-matching circuit, a power amplifier circuit, a voltage supply circuit, a bias control circuit, an output-matching circuit, and a detection circuit. DC voltage corresponding to the output power of the high-frequency power amplifier circuit6is output from Vdet terminal.

In the equivalent circuit of a high-frequency circuit shown inFIG. 9, the high-frequency switch circuit1, the high-frequency power amplifier circuit6, and the balanced-unbalanced conversion circuit3may be those already explained. Thus, the equivalent circuit of the coupler circuit11will be explained below.FIG. 25shows one example of the coupler circuit11. The coupler circuit11comprises a main line lsc1disposed between a port P3connected to the high-frequency switch circuit1and a port P2connected to the filter circuit2, and a sub-line lsc2coupled to the main line lsc1. The sub-line lsc2has one end connected to the transmitting/receiving circuit BLT-TR of Bluetooth, and the other end connected to a ground electrode via a resistor rc1. The balanced-unbalanced conversion circuit4having the already explained equivalent circuit may be connected between the coupler circuit11and the transmitting/receiving circuit BLT-TR of Bluetooth, as shown inFIG. 10.

The high-frequency circuit device of the present invention comprises a laminate of dielectric ceramic layers with electrode patterns, and at least one semiconductor element mounted on the laminate.FIG. 26shows the appearance of the high-frequency circuit device10having the high-frequency circuit shown inFIGS. 1 and 11,FIG. 27shows a bottom surface of the laminate substrate100of the high-frequency circuit device10, andFIG. 28shows the structure of each layer in the laminate substrate100. This high-frequency circuit device10comprises the high-frequency switch circuit1, the first bandpass filter2, the balanced-unbalanced conversion circuit3, the high-frequency power amplifier circuit6, and the detection circuit8. An upper surface of the laminate substrate100is provided with pluralities of land electrodes, on which chip parts not contained in the laminate substrate100are mounted, and the high-frequency switch circuit1, the high-frequency power amplifier circuit6, the Schottky diode83, the chip capacitors91,94,96, and the chip resistors92,93,95are mounted on the land electrodes as shown inFIG. 26. The land electrodes are connected to connecting lines and circuit elements in the laminate substrate100through via-holes.

The high-frequency switch circuit1may be mounted in a bare state on the land electrode of the laminate substrate100, and sealed with a resin or a pipe. Miniaturization can be achieved by constituting the high-frequency circuit device10by the laminate substrate100and parts mounted thereon. Of course, RF-IC and baseband IC constituting the transmitting/receiving circuit may be integrated in the laminate substrate100.

The laminate substrate100is made of dielectric ceramics sinterable at as low temperatures as, for instance, 1000° C. or lower. The laminate substrate100may be produced by printing each ceramic green sheet as thick as 10-200 μm with a conductive paste of low-resistivity Ag, Cu, etc. to form predetermined electrode patterns, integrally laminating pluralities of green sheets with electrode patterns, and sintering the resultant laminate.

The dielectric ceramics include, for instance, (a) dielectric ceramics comprising Al, Si and Sr as main components, and Ti, Bi, Cu, Mn, Na, K, etc. as sub-components, (b) dielectric ceramics comprising Al, Si and Sr as main components, and Ca, Pb, Na, K, etc. as sub-components, (c) dielectric ceramics comprising Al, Mg, Si and Gd, (d) dielectric ceramics comprising Al, Si, Zr and Mg, etc. The dielectric ceramics preferably have dielectric constants of about 5-15. In addition to the dielectric ceramics, resins, or composites of resins and dielectric ceramic powder may be used. According to an HTCC (high-temperature co-fired ceramic) method, dielectric ceramic substrates based on Al2O3are provided with high-temperature-sinterable metal patterns of tungsten, molybdenum, etc., and integrally sintered.

The internal structure of the laminate substrate100will be explained referring toFIGS. 27 and 28. An uppermost green sheet201is provided with land electrodes, on which parts are mounted, and second to 16th green sheet layers202-216are provided with line electrodes, capacitor electrodes and ground electrodes, which are connected through via-holes (shown by black circles in the figure) formed in the green sheets. The lowermost green sheet216is provided with a wide ground electrode GND, a bottom surface of which has terminal electrodes to be mounted on a circuit board.

If isolation were insufficient among the input-matching circuit, voltage supply circuit and output-matching circuit of the high-frequency power amplifier circuit6, malfunction and oscillation would be likely to occur in the power amplifier. To secure isolation among these circuits, the arrangement of planar ground electrodes and via-holes connected thereto should be optimized. To avoid the influence of unnecessary noise from the high-frequency power amplifier circuit6, electrodes constituting the bandpass filter2connected to the antenna ANT are desirably arranged as distant from the high-frequency power amplifier circuit6as possible. Likewise, electrodes constituting the balanced-unbalanced conversion circuits disposed in the receiving path of wireless LAN and the transmitting/receiving path of Bluetooth are desirably arranged as distant from the high-frequency power amplifier circuit6as possible. Thus, the intrusion of unnecessary noise generated from the high-frequency power amplifier circuit6is reduced, resulting in the improved receiving sensitivity.

Disposed on the bottom surface of the laminate substrate100are, as shown inFIG. 27, two ground electrodes GND in a center portion, an antenna port ANT in a periphery, the transmitting port11gb-T of wireless LAN, the receiving ports11bg-R+,11bg-R− of wireless LAN, a transmitting/receiving port BLT-TR of Bluetooth, a ground port GND, control ports V1, V2, V3for the high-frequency switch circuit1, power source ports Vc, Vb for the high-frequency power amplifier circuit, and a output voltage port Vdet of the detection circuit. Each terminal electrode is depicted by the same symbols as inFIG. 11. Although the terminal electrodes are in a land grid array (LGA) in the embodiment, they may be in a ball grid array (BGA), etc.

FIG. 30shows the appearance of a high-frequency circuit device10comprising a laminate substrate100having the high-frequency circuit (equivalent circuit) shown inFIGS. 5 and 20, andFIGS. 31(a)-(c) show the structure of each layer in the laminate substrate100. The high-frequency circuit device10comprises a high-frequency switch circuit1, a first bandpass filter2, balanced-unbalanced conversion circuits3,4, a high-frequency power amplifier circuit6having a detection circuit, and a splitter circuit9. The high-frequency switch circuit1is as shown inFIG. 21, and the high-frequency power amplifier circuit6is as shown inFIG. 24. Mounted on pluralities of land electrodes on the upper surface of the laminate substrate100are a high-frequency switch circuit1of SPDT, a power amplifier circuit part PA for the high-frequency power amplifier circuit6, chip capacitors cb3, cs, c3, c9, c8, c30, ct, c1, c4, c5, c6, and chip resistors rsp, r1. The land electrodes are connected to connecting lines and circuit elements in the laminate substrate100through via-holes. Although chip capacitors and chip resistors are mounted on the upper surface of the laminate substrate100inFIG. 30, they may be formed in the laminate substrate100.

The high-frequency switch circuit1and the power amplifier circuit part PA may be mounted in a bare state on the land electrodes of the laminate substrate, and sealed with a resin to provide the high-frequency circuit device10. Miniaturization is thus achieved by constituting the high-frequency circuit device in the form of a laminate substrate. Of course, RF-IC and baseband IC constituting the transmitting/receiving circuit parts may be integrated in the laminate substrate100.

The line electrodes for inductance elements, the electrodes for capacitance elements, and the ground electrodes are connected through via-holes formed in the green sheets. The symbols inFIGS. 31(a) to31(c) are substantially identical to those inFIGS. 20 and 24, as shown in Table 7. For instance, the line electrode lh1for an inductance element inFIG. 20is constituted by the electrodes lh1a, lh1b, lh1cinFIGS. 31(a) to31(c). The same is true of the other electrodes.

If isolation were insufficient among the input-matching circuit, voltage supply circuit and output-matching circuit of the high-frequency power amplifier circuit6, malfunction and oscillation would be likely to occur in the power amplifiers. Accordingly, to secure isolation among these circuits, the arrangement of planar ground electrodes and via-holes connected thereto is optimized. To avoid the influence of unnecessary noise generated from the high-frequency power amplifier circuit6, electrodes constituting the bandpass filter connected to the antenna ANT are preferably disposed as distant from the high-frequency power amplifier circuit6as possible. Similarly, electrodes constituting the balanced-unbalanced conversion circuits in the receiving path of wireless LAN and the transmitting/receiving path of Bluetooth are preferably disposed as distant from the high-frequency power amplifier circuit6as possible. This improves the reduction of unnecessary noise generated from the high-frequency power amplifier circuit6, thereby improving the receiving sensitivity.

As shown inFIGS. 31(a) to31(c), the bottom surface of the laminate substrate100is provided with the ground electrode GND in a center portion, the antenna port ANT in a periphery, the transmitting port11bg-T of wireless LAN, the receiving ports11bg-R+,11bg-R− of wireless LAN, the transmitting/receiving ports BLT-TR+, BLT-TR− of Bluetooth, Bluetooth ground port GND, the control ports Vc1, Vc2for the high-frequency switch circuit, the power source ports Vc, Vb, Vdd for the high-frequency power amplifier circuit, and the output voltage port Vdet of the detection circuit.

FIG. 32shows the equivalent circuit of a high-frequency circuit device according to a still further embodiment of the present invention. In this embodiment, the circuit is the same as shown inFIG. 20, except that the splitter circuit9is replaced by a coupler circuit11. The coupler circuit11has a main line connected to the receiving circuit of wireless LAN, and a sub-line connected to the transmitting/receiving circuit of Bluetooth. The coupling ratio of the main line to the sub-line may be arbitrarily set. For instance, a ratio of the receiving circuit of wireless LAN to the transmitting/receiving circuit of Bluetooth may be set at 10:1.

FIG. 33shows the appearance of the high-frequency circuit device ofFIG. 32, andFIGS. 34(a) to34(c) show the layer structure of its laminate substrate101. The circuit in this embodiment is the same as shown inFIGS. 30 and 31(a) to31(c), except that the splitter circuit is replaced by a coupler circuit. Mounted on the laminate substrate101is the resistance element rc of the coupler circuit in place of the resistance element rsp shown inFIG. 30.

The line electrodes for inductance elements, the electrodes for capacitance elements, and the ground electrodes are connected through via-holes. The symbols inFIGS. 34(a) to34(c) are identical to those inFIGS. 32 and 33as much as possible. The coupler circuit lcp1is constituted by lcpla, lcp1bin the laminate, and lcp2is constituted by lcp2a, lcp2b.

In any of the above embodiments, a portion of the laminate substrate100, on which the high-frequency power amplifier circuit6is mounted, is preferably provided with thermal-vias TV for enhancing heat radiation from an upper surface to a bottom surface. To suppress unnecessary noise radiation, the green sheets202,214,216are preferably provided with a wide ground electrode GND. In the laminate substrate100having a three-dimensional circuit, electrode patterns constituting the circuit are preferably separated by via-holes connected to the planar ground electrode GND and the ground electrode GND, and avoid overlapping in a lamination direction, to prevent unnecessary electromagnetic interference with electrode patterns constituting the other circuit.FIG. 29shows an example of the planar arrangement of such a circuit, with positional differences neglected in a lamination direction.

EFFECT OF THE INVENTION

The high-frequency circuit of the present invention commonly usable in at least two different communications systems using substantially the same frequency band, and the high-frequency circuit device and the communications apparatus comprising such high-frequency circuit are suitable for miniaturization, because of small numbers of parts.