Hf circuit and front-end circuit comprising an hf circuit

Abstract

An HF circuit is disclosed for use in, for example, front-end circuits, having improved signal quality for a carrier set. To this end, a signal path between a duplexer and a diplexer includes a phase shifter.

Description

Technology Field

[0001] The present invention relates to HF circuits that can be used, for example, in front-end circuits of mobile wireless devices. Background Technology

[0002] The front-end circuits of mobile wireless devices connect one or more receiving or transmitting amplifiers to one or more antennas. These connections are made by signal paths and HF filters that are interconnected so that multiple transmitting systems and transmitting frequencies can be used while the requirements for the signal quality of the mobile wireless devices are met.

[0003] From U.S. Patent No. 7,212,789 B2, HF circuits having a tunable duplexer are known.

[0004] In conventional frequency division duplexing (FDD) systems, transmit and receive frequencies are used simultaneously; however, to increase data transmission speeds, different transmit frequencies may be used simultaneously or different receive frequencies may be used simultaneously (carrier aggregation). In inter-band carrier aggregation systems, two FDD receive frequencies may be used simultaneously with one FDD transmit frequency. It is also possible to use two FDD transmit frequencies simultaneously with one or multiple receive frequencies (Tx carrier aggregation).

[0005] However, such common use of different frequency bands will present problems with conventional HF circuits, because those circuits are not adapted to additional HF power, particularly for the separation of different signal paths.

[0006] Accordingly, the object of the present invention is to provide an HF circuit that allows good separation between different signal paths even when the circuit processes HF signals of different frequency bands. Specifically, interference with the signal paths due to the intermodulation product should be reduced.

[0007] This objective is achieved by the HF circuit according to claim 1. The dependent claims provide advantageous embodiments.

[0008] For this purpose, the HF circuit comprises a diplexer, a first duplexer for a first frequency band, and a first duplexer for a second frequency band. The diplexer has a first port, a common port, and a second port. The first duplexer for the first frequency band has a transmit port, a common port, and a receive port. The first duplexer for the second frequency band also has a transmit port, a common port, and a receive port. The circuit further comprises a first signal path between the common port of the first duplexer for the first frequency band and the first port of the diplexer. The HF circuit further comprises a second signal path between the common port of the first duplexer, the second frequency band, and the second port of the diplexer. Furthermore, the circuit comprises a phase shifter arranged within the second signal path. The phase shifter is provided to adjust the impedances of the first duplexer for the second frequency band and the diplexer for at least one harmonic of one of the frequency bands so that at least one intermodulation product is reduced.

[0009] Impedance control, in particular, relates to the impedance of the common port of the first duplexer and the second port of the diplexer of the second signal path.

[0010] In such cases, the harmonics may be, in particular, second or third harmonics of the transmission frequencies of the first frequency band.

[0011] Therefore, the improved signal separation of such HF circuits is attributed to the reduction of the intermodulation product. In conventional HF circuits of front-end circuits, it has been found that the separation of the diplexer used can be so poor that undesirable HF signals occurring within the signal path can cause an intermodulation product due to nonlinear effects downstream of the duplexer. Their frequencies are within the transmission range of the duplexer. Subsequently, such undesirable HF signals cannot be further removed by conventional HF filters because their frequencies are the same as the frequencies of the desirable signals.

[0012] By the phase shifter, the formation of these intermodulation products is effectively prevented or at least sufficiently reduced so that undesirable but significantly weaker intermodulation products no longer interfere.

[0013] These HF circuits are compatible with conventional switching topologies of front-end circuits, and relatively high gain in signal quality is achieved by relatively low additional circuit complexity.

[0014] The diplexer can be a ceramic diplexer.

[0015] Such a ceramic diplexer may comprise a body made of an insulating material, such as ceramic. The body may be provided with recesses in which the internal surfaces are covered by metallization. Such a diplexer typically already possesses very high linearity.

[0016] The first frequency band may be a 2-gigahertz band, and the second frequency band may be a 1-gigahertz band.

[0017] Subsequently, the first frequency band includes frequencies substantially from 1 GHz to 2 GHz, particularly from 1.4 to 2.2 GHz. Subsequently, the second frequency band includes frequencies substantially ≤ 1 GHz.

[0018] The first frequency band and the second frequency band may also be selected from three frequency ranges: a low band (LB, about 650 to 1000 MHz), a mid band (MB, 1700 to 2200 MHz), and a high band (HB, substantially > 2500 MHz frequencies (f)).

[0019] Specifically, mobile wireless frequency bands (1, 2, 3, 4, 5, 7, 8, 12, 17, 19, 20, 21, 26, or 28) are suitable as a first frequency band or a second frequency band, for example, for a set of carriers at transmission frequencies. Mobile wireless bands (5, 8, 12, 17, 19, 20, 26, 28) are associated with LB. Mobile wireless bands (1, 2, 3, 4, 21) are associated with MB, and frequency band (7) is associated with HB.

[0020] For example, the following frequency band pairs can be used in combination:

[0021] LB and LB: 5 and 12, 5 and 17;

[0022] LB and MB: 3 and 5, 1 and 5, 3 and 20, 1 and 19, 3 and 8, 4 and 12, 4 and 17, 3 and 26, 3 and 19, 19 and 21;

[0023] MB and MB: 1 and 21, 2 and 4;

[0024] MB and HB: 1 and 7, 3 and 7, 4 and 7;

[0025] LB and HB: 7 and 20, 7 and 28, 5 and 7.

[0026] The HF circuit may additionally include a second or more additional duplexers of the first frequency band. Here, the second duplexer or a plurality of additional duplexers of the first frequency band can be interconnected on one hand in parallel with the first duplexer of the first frequency band and on the other hand in the first signal path. This allows transmission operations through different duplexers of the first frequency band—whether simultaneous or sequential.

[0027] The HF circuit may also have a switch array, by which the first port of the diplexer can be interconnected with a second or more additional duplexers of a first frequency band. Subsequently, using the switch array, it is possible to individually control which of the duplexers will be interconnected with the diplexer. Exactly one duplexer may always be connected to the diplexer at any given time. However, it is also possible for no duplexer to be interconnected with the diplexer at any given time, or for multiple duplexers to be interconnected with the diplexer simultaneously.

[0028] In addition, the HF circuit may include a second or more additional duplexers of a second frequency band. The second or more duplexers of the second frequency band can be interconnected on one side in parallel with the first duplexer of the second frequency band and on the other side in a second signal path.

[0029] In this case, the HF circuit may also additionally include an additional switch array, and by means of this switch array, the second port of the diplexer can be interconnected with a second or more additional duplexers of a second frequency band.

[0030] Accordingly, similar to the situation of the first frequency band described above, the number of duplexers in the second frequency band interconnected with the diplexer can also be individually adjusted.

[0031] The phase shifter may be tunable. The tunable phase shifter may, in particular, be a phase shifter in which characteristic frequencies and / or phase offset are adjustable with respect to the relevant frequencies.

[0032] A phase shifter may be provided to the second signal path for each duplexer of the second frequency band.

[0033] If the HF circuit includes multiple phase shifters, they may be arbitrarily selected from the aforementioned alternatives. However, multiple or all phase shifters may also be of the same type.

[0034] A phase shifter can reflect undesirable signals generated from a diplexer back to the diplexer. Desirable signals within a corresponding frequency range can pass through the diplexer without substantial power loss. The phase shifter may, in particular, be a tunable phase shifter in which the degree of phase shift of a signal having a predetermined frequency is adjustable. For example, the phase offset caused by the phase shifter preferably changes linearly with the frequency of the applied signal.

[0035] A phase shifter configured as a phase shifter may, in particular, be a global pass filter composed of inductances and capacitances.

[0036] A stripline can also be used as a phase shifter.

[0037] In particular, the HF circuit can be interconnected to a mobile wireless device, for example, to the front-end circuit of the mobile wireless device. A mobile wireless device having a front-end circuit including such an HF circuit provides the user with increased data rates along with undamaged signal quality.

[0038] The number of duplexers for each of the first frequency band or the second frequency band is not limited. Both the first frequency band and the second frequency band may independently have one, two, three, four, or more duplexers.

[0039] The first frequency band may have one, two, three, four, five, or more duplexers. The second frequency band may also have one, two, three, four, five, or more duplexers.

[0040] In the following, the central principles of the HF circuit and some non-limiting exemplary embodiments will be explained in more detail by way of schematic diagrams. Brief explanation of the drawing

[0041] Figure 1 illustrates the basic structure of an HF circuit. FIG. 2 illustrates an embodiment having multiple duplexers of a first frequency band. FIG. 3 illustrates an embodiment having multiple duplexers in a second frequency band. FIG. 4 illustrates an embodiment having a tunable phase shifter. FIG. 5 illustrates an embodiment having multiple duplexers of a first frequency band and multiple duplexers of a second frequency band. Figure 6 illustrates the characteristic transfer curves of a typical diplexer. Figure 7 illustrates the characteristic transfer curves of a typical diplexer with somewhat improved separation. Figure 8 illustrates the effect of a phase shifter in an HF circuit based on different curves for different values ​​of phase offset—each curve representing a measure of the intermodulation product. Figure 9 illustrates the effect of a phase shifter in an HF circuit with an improved diplexer based on different curves for different values ​​of phase offset—each curve representing a measure of the intermodulation product. Figure 10 illustrates the dependence of the strength of the intermodulation product on phase rotation by the phase shifter at the center frequency. Specific details for implementing the invention

[0042] FIG. 1 illustrates a simple embodiment of an HF circuit (HF-S) having a first duplexer (DU-HB-1) of a first frequency band, a first duplexer (DU-LB-1) of a second frequency band, and a diplexer (DI). The first duplexer (DU-LB-1) of the second frequency band connects a second signal path (SP2) to a second port (P2) of the diplexer (DI). A phase shifter (PS) is interconnected to the second signal path (SP2). The common port (PC) of the first duplexer (DU-HB-1) of the first frequency band connects a first signal path (SP1) to a first port (P1) of the diplexer (DI). The common port (PC) of the diplexer (DI) is interconnected with an antenna of a communication device. Each of the two duplexers has a transmit port (TX) and a receive port (RX). Two duplexers can be interconnected with one or more transceiver circuits of a mobile wireless device through transmit and receive ports.

[0043] The following situation is critical when operating a conventional HF circuit: a transmission signal is coupled to both sides of the transmission ports (TX) of two duplexers and reaches a diplexer (DI) through signal paths (SP1, SP2). Due to the limited separation of the diplexer (DI), a portion of the transmission signal from the first frequency band is coupled to the second signal path (SP2) in the direction of the duplexer of the second frequency band. Typically, the duplexers themselves are circuits with imperfect linear behavior, where different TX signals are gathered at the TX filter of the duplexer of the second frequency band (DU-LB-1) in this case. Due to the non-linear effect of the duplexer of the second frequency band, an intermodulation product is generated that can pass through the receive filter (RX) and may interfere with or even completely prevent simultaneous reception by the communication device. For example, if a communication device needs to transmit simultaneously in bands (3, 5), an intermodulation product can occur at 1710 MHz - 824 MHz = 886 MHz. This is within the receiving frequency band (RX) of band (5) and therefore can pass through a receiving filter with almost no attenuation.

[0044] In the HF circuit (HF-S) of the present invention, the signal leaked from the diplexer (DI) into the second signal path (2) is shifted by a phase shifter at its phase position so that no mixing with the transmitted signal with respect to the second signal path (SP2) can occur in the duplexer. As a result, the occurrence of the intermodulation product at 886 MHz is prevented or its strength is weakened, making reception operation easier.

[0045] FIG. 2 illustrates an embodiment in which three duplexers (DU-HB-1, DU-HB-2, DU-HB-3) are provided for a first frequency band. Each of the duplexers can be coupled to a first signal path (SP1) by an individual switch (SW).

[0046] Essentially similar, FIG. 3 illustrates an embodiment of an HF circuit (HF-S) provided with three duplexers (DU-LB-1, DU-LB-2, DU-LB-3) of a second frequency band. Each of the three duplexers can be individually coupled to a second signal path (SP2) by means of switches. Here, a phase shifter (PS) can be specifically assigned to each of the three duplexers. The switches are preferably interconnected between the phase shifters and the duplexers.

[0047] FIG. 4 illustrates how a single phase shifter, rather than three different phase shifters, can be interconnected to the second signal path (SP2). This phase shifter (PS) is provided and configured to prevent or attenuate the intermodulation product for all three duplexers of the second frequency band.

[0048] FIG. 5 illustrates an embodiment in which three duplexers are provided in each of the first frequency band and the second frequency band.

[0049] Figure 6 shows the characteristic curves of a typical diplexer with relatively low separation.

[0050] Figure 7 illustrates the characteristic curves of a typical diplexer with higher separation.

[0051] FIG. 8 illustrates the intensity of intermodulation interference in carrier sets of two Tx bands (B5, B7) when the diplexer of FIG. 6 is used. Each of the different curves represents a different phase offset by a phase shifter. The intermodulation product has frequency components of approximately 880 MHz:

[0052] B7-Tx (2540 MHz) - 2 x B5-Tx (2 x 830 MHz) = B5-Rx (880 MHz).

[0053] The HF circuit includes a tunable phase shifter as a phase shifter with an adjustable phase offset. Depending on the selected phase offset, a reduction in intermodulation interference of up to about 30 dB can be achieved.

[0054] Correspondingly, FIG. 9 illustrates different separation values ​​of an HF circuit including the "improved" diplexer of FIG. 7 with increased separation—in addition to the tunable phase shifter as a phase shifter. The different curves shown in FIG. 8 represent separation values ​​with a variable phase offset by the phase shifter. Similar to FIG. 7, the reduction of intermodulation interference can be improved by up to 30 dB by selecting a suitable phase offset.

[0055] Overall, FIGS. 6 through 9 show that HF ​​circuits having both a worse diplexer and an improved diplexer benefit significantly from the new circuit topology.

[0056] FIG. 10 illustrates the strength of the intermodulation product for HF circuits each having a phase shifter configured as a phase shifter and one of the two diplexers shown in FIG. 6. It has been found that improved separation actually results in a reduction of the intermodulation product—but only when the phase shifter dimensioning is properly optimized or adjusted accordingly.

[0057] The HF circuit is not limited to the exemplary embodiments described or illustrated. The HF circuit may include, in particular, additional circuit components, signal paths, filters, and switches. Explanation of the symbols

[0058] PB-HP: The high-pass passband of a diplexer PB-LP: The low-pass passband of a diplexer DI: Diplexer DU: Duplexer DU-HB-1: First duplexer of the first frequency band DU-HB-2: Second duplexer of the first frequency band DU-HB-3: Third duplexer of the first frequency band DU-LB-1: First duplexer of the second frequency band DU-LB-2: Second duplexer of the second frequency band DU-LB-3: Third duplexer of the second frequency band HF-S: HF circuit IS: Separation of the diplexer PC: Common Port RX: Listen port PS: Phase Shifter SD: Switch SP1: First signal path SP2: Second signal path TX: Transmission port

Claims

Claim 1 As an HF (high frequency) circuit, a diplexer having a first port, a common port, and a second port; a first duplexer for a first frequency band having a transmitting port, a common port, and a receiving port; a second duplexer for a second frequency band having a transmitting port, a common port, and a receiving port; a first signal path between the common port of the first duplexer for the first frequency band and the first port of the diplexer; and a second signal path between the common port of the second duplexer for the second frequency band and the second port of the diplexer. An HF circuit comprising a phase shifter in the second signal path, wherein having the phase shifter in the second signal path reduces at least one intermodulation product caused by the nonlinearity of the second duplexer for the second frequency band, wherein the at least one intermodulation product is caused by leakage of a transmission signal on the first signal path into the second signal path, and wherein the transmission signal is provided to the transmission port of the first duplexer for the first frequency band, and wherein reducing the at least one intermodulation product adjusts the phase of the transmission signal leaked into the second signal path. Claim 2 In claim 1, the above diplexer is a ceramic diplexer, an HF circuit. Claim 3 An HF circuit according to claim 1, wherein the first frequency band is a 2 GHz band and the second frequency band is a 1 GHz band. Claim 4 An HF circuit according to claim 1, wherein the first frequency band is a 2.5 GHz band and the second frequency band is a 1 GHz band. Claim 5 An HF circuit according to claim 1, further comprising a plurality of additional duplexers for the first frequency band that are interconnected with the first signal path and in parallel with the first duplexer for the first frequency band. Claim 6 An HF circuit according to claim 5, further comprising a switch array that enables the first port of the diplexer to be interconnected with one or more of the plurality of additional duplexers for the first frequency band. Claim 7 An HF circuit according to claim 1, further comprising a plurality of additional duplexers for the second frequency band that are interconnected with the second signal path and in parallel with the second duplexer for the second frequency band. Claim 8 An HF circuit according to claim 7, further comprising a switch array that enables the second port of the diplexer to be interconnected with one or more of the plurality of additional duplexers for the second frequency band. Claim 9 In claim 1, the phase shifter is an HF circuit tunable within its phase offset. Claim 10 An HF circuit according to any one of claims 1 to 9, wherein one phase shifter per duplexer for the second frequency band is provided within the second signal path. Claim 11 A mobile wireless device comprising an HF (high frequency) circuit, the device comprising: a diplexer having a first port, a common port, and a second port; a first duplexer for a first frequency band having a transmitting port, a common port, and a receiving port; a second duplexer for a second frequency band having a transmitting port, a common port, and a receiving port; a first signal path between the common port of the first duplexer for the first frequency band and the first port of the diplexer; and a second signal path between the common port of the second duplexer for the second frequency band and the second port of the diplexer. A mobile wireless device comprising a phase shifter in the second signal path, wherein having the phase shifter in the second signal path reduces at least one intermodulation product caused by the nonlinearity of the second duplexer for the second frequency band, wherein the at least one intermodulation product is caused by leakage of a transmission signal on the first signal path into the second signal path, and wherein the transmission signal is provided to the transmission port of the first duplexer for the first frequency band, and wherein reducing the at least one intermodulation product adjusts the phase of the transmission signal leaked into the second signal path. Claim 12 A wireless communication method comprising: providing a first transmission signal to a transmission port of a first duplexer for a first frequency band — the first duplexer for the first frequency band includes the transmission port, a common port, and a reception port, and there is a first signal path between the common port of the first duplexer for the first frequency band and a first port of a diplexer, and the diplexer has the first port, a common port, and a second port —; and providing a second transmission signal to a transmission port of a second duplexer for a second frequency band — the second duplexer for the second frequency band has the transmission port, a common port, and a reception port, and there is a second signal path between the common port of the second duplexer for the second frequency band and a second port of the diplexer —; A wireless communication method comprising the step of reducing at least one intermodulation product caused by the nonlinearity of the second duplexer for the second frequency band by having a phase shifter in the second signal path, wherein the at least one intermodulation product is caused by leakage of the first transmission signal on the first signal path into the second signal path, and reducing the at least one intermodulation product includes adjusting the phase of the first transmission signal leaked into the second signal path.

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