TWI474558B - Signal processing circuit - Google Patents

Description

Signal processing circuit

The present invention relates to a signal processing circuit, and more particularly to a signal processing circuit for use in a multi-antenna wireless communication device.

In a wireless communication system, multiple antenna transmissions can be used to achieve space diversity and multiple-input-multiple-output (MIMO) functions, which can effectively improve system performance. For example, devices that support industry standards such as IEEE 802.11n or long term evolution have employed multiple antennas to provide multiple input and multiple output functions.

However, the use of multiple antennas can also have a negative impact. For example, a signal transmitted by one antenna may be coupled to another antenna to become a noise or interference signal when the receiving circuit processes the signal. Therefore, when multiple antennas are used, the signal coupled between the antennas is too large, which may degrade the performance of the system.

In some devices, the effect of the coupled signal can be reduced by increasing the distance between the antennas or by using an isolator or the like. However, modern electronic devices are not only compact in size, but also often need to integrate more components. The influence of the coupled signals is bound to be more serious, and the performance of the system is further deteriorated. Since the space available for electronic devices is limited, it is not feasible to increase the distance between the antennas. Isolator on the other hand Not only does it take up a lot of space, but the isolator's bandwidth is limited and often does not provide enough isolation.

Therefore, how to design an apparatus and method capable of reducing the influence of a coupled signal in a multi-antenna communication device has been a problem that has been encountered in the industry for a long time.

The present specification provides an embodiment of a signal processing circuit, including: a first node coupled to a first antenna; a second node coupled to a second antenna; a third a node for receiving a first signal transmitted by a transmitting circuit; a signal separating circuit coupled to the first node and the third node, configured to separate the first signal into a second signal and a first a third signal, and the second signal is transmitted to the first antenna; a phase shifting circuit coupled to the signal separating circuit for changing a phase of the third signal to generate a fourth signal; a signal combining circuit And coupled to the phase shifting circuit and the second node for combining the fourth signal and a fifth signal received from the second antenna; and a fourth node for transmitting the fifth signal And a receiving circuit, wherein the fourth signal is usable to cancel at least a portion of a coupled signal between the third node and the fourth node.

The present specification further provides an embodiment of a communication method, including: separating a first signal into a second signal and a third signal; transmitting the second signal to a first antenna; and changing the third signal Phase to generate a fourth signal; receive a fifth signal from a second antenna; combine the fourth signal and the fifth signal; and use the fourth signal to cancel the first antenna and the second antenna At least a portion of a coupled signal.

The present specification further provides an embodiment of a communication device, including: a first node For coupling to a first antenna, a second node for coupling to a second antenna, a third node for coupling to a transmitting circuit, and a fourth node for coupling a receiving circuit; and a signal processing circuit coupled to the first, the second, the third, and the fourth node, for receiving a first signal from the transmitting circuit, separating the first signal into a a second signal and a third signal, changing a phase of the third signal to generate a fourth signal, combining the fourth signal, and a fifth signal received from the second antenna, and transmitting the combined signal To the receiving circuit, wherein the fourth signal is usable to cancel at least a portion of a coupled signal between the third node and the fourth node.

One of the advantages of the foregoing embodiments is that the device for reducing the coupled signal is compact in size and can be applied to more application environments.

Another advantage of the foregoing embodiments is that such a device that reduces the coupling signal is easy to adjust and can be adjusted to the most appropriate settings for different applications.

100‧‧‧Communication device

120, 140‧‧‧ antenna

160‧‧‧Signal Processing Circuit

162‧‧‧Signal separation circuit

164‧‧‧ Phase shifting circuit

166‧‧‧Signal combining circuit

170‧‧‧Transmission circuit

190‧‧‧ receiving circuit

211, 212, 213, 311-316, 411-416‧‧ ‧ capacitor

221, 222, 321, 322, 421-424‧‧ ‧ inductance

231,331,431‧‧‧resistance

1 is a simplified functional block diagram of an embodiment of a communication device of the present invention.

FIG. 2 is a simplified functional block diagram of an embodiment of the signal separation circuit of FIG. 1. FIG.

3 is a simplified functional block diagram of another embodiment of the signal separation circuit of FIG. 1.

4 is a simplified functional block diagram of another embodiment of the signal separation circuit of FIG. 1.

Embodiments of the present invention will be described below in conjunction with the associated drawings. In the drawings, the same reference numerals indicate the same or similar elements. Certain terms are used throughout the description and following claims to refer to particular elements, and those of ordinary skill in the art should understand that there may be different terms used to refer to the same elements. Ben said The scope of the patent application and the subsequent patent application does not use the difference in name as the way to distinguish the components, but the difference in function of the components as the basis for differentiation. The words "including..." mentioned in the entire specification and subsequent claims are open-ended terms and should be interpreted as "including but not limited to...". In addition, the term "coupled" includes any direct and indirect means of attachment. Therefore, if the first device is described as being coupled to the second device, the first device can be directly connected (including a signal connection through electrical connection, wired/wireless transmission, or optical transmission) to the second device, or The indirect electrical or signal of other devices or connections is connected to the second device.

1 is a simplified functional block diagram of a multi-antenna communication device 100 in accordance with an embodiment of the present invention. The communication device 100 includes antennas 120 and 140, a signal processing circuit 160, a transmitting circuit 170, and a receiving circuit 190. The signal processing circuit 160 includes a signal separation circuit 162, a phase shift circuit 164, and a signal combining circuit 166. For the sake of brevity, other components and connection relationships are omitted in FIG.

Antennas 120 and 140 may employ any suitable form of antenna, such as a dipole antenna, a printed antenna, a stereo antenna or an antenna array, and the like. The circuits 160, 162, 164, 166, 170, and 190 can be implemented by discrete circuits, integrated circuits, processors, other suitable hardware, software, or by hardware with hardware.

Antennas 120 and 140 can transmit and/or receive signals separately or in combination. The transmitting circuit 170 is configured to generate a signal to be transmitted, and the receiving circuit 190 is configured to process the received signal.

As shown in FIG. 1, the communication device 100 transmits the signal St by the antenna 120, and receives the signal Sr by the antenna 140. Transmit circuit 170 transmits signal S0 to signal separation circuit 162. this In addition, the coupling signal Sc represents a portion of the signal S0 coupled by the transmitting circuit 170 to the receiving circuit 190. The coupling signal Sc drawn in FIG. 1 is only for ease of description. In fact, the signal S0 may be via the antenna 120 and the antenna 140, by the ground of the transmitting circuit 170 and the receiving circuit 190, or by other coupling. The path is coupled to the receiving circuit 190 by the transmitting circuit 170.

The signal separation circuit 162 receives the signal S0 from the transmission circuit 170 and separates the signal S0 into a signal St and a signal S1. In the present embodiment, the signal St and the signal S1 are signals obtained by decreasing the signal value of the signal S0. Signal separation circuit 162 transmits signal St to antenna 120 and transmits signal S1 to phase shift circuit 164. Signal S1 is set to have substantially the same signal value (eg, voltage value, current value, or may also be converted to a suitable signal form) as coupled signal Sc. Phase shifting circuit 164 receives signal S1 and changes the phase of signal S1 to produce signal S2 to set signal S2 to have substantially the same signal value as coupling signal Sc and to have a phase difference of approximately 180 degrees. In another embodiment, the signal St and the signal S1 may be respectively set to have the same signal value as the signal S0, the signal whose signal value of the signal S0 is decreased, or the signal whose signal value of the signal S0 is increased.

Antenna 140 receives signal Sr and transmits signal Sr to signal combining circuit 166. Signal combining circuit 166 combines signal Sr and signal S2 into signal S3 and transmits signal S3 to receiving circuit 190. The signal received by the receiving circuit 190 includes the coupling signal Sc and the signal S3 because the signal S3 includes the signal Sr and the signal S2, and the signal S2 and the coupling signal Sc have substantially the same signal value and a phase difference of about 180 degrees. Therefore, the signal S2 can reduce or cancel the influence of the coupled signal Sc, so that the receiving circuit 190 can process the signal Sr that really needs to be processed, and can obtain better performance.

In an embodiment, the phase shifting circuit 164 uses a resistor-capacitor circuit ( A resistor-capacitor circuit) produces a desired phase change to signal S1 to produce signal S2. In another embodiment, phase shifting circuit 164 can generate a desired phase change to signal S1 to produce signal S2 using one or more transmission lines, or a circuit composed of passive components and/or active components.

In an embodiment, signal combining circuit 166 directly couples the transmission paths of signal S2 and signal Sr to combine signal S2 and signal Sr into signal S3. In another embodiment, signal combining circuit 166 converts signal S2 and/or signal Sr into an appropriate form (eg, into a voltage or current form, etc.) and combines the converted signals into signal S3.

In one embodiment, the signal value of the coupled signal Sc and the phase difference between the coupled signal Sc and the signal S0 can be measured in a low-interference or non-interfering laboratory, or by software simulation. The signal separation circuit 162 can be set by measuring or simulating the signal value of the coupled signal Sc obtained by using the measurement or simulation. The phase shift circuit 164 is set by using the phase difference between the coupled signal Sc and the signal S0 obtained by measurement or simulation, so that the signal S2 is The coupled signal Sc has substantially the same signal value and a phase difference of approximately 135 degrees to 225 degrees, and can reduce or cancel the effect of the coupled signal Sc. In another embodiment, the signal S2 can be set to have substantially the same signal value as the coupled signal Sc, and the signal S2 is set to have a phase difference of 180 degrees from the coupled signal Sc.

In another embodiment, the communication device 100 transmits the signal St by the antenna 140 and the signal Sr is received by the antenna 120. The transmitting circuit 170 is coupled to the antenna 140 to transmit a signal St, and the receiving circuit 190 is coupled to the antenna 120 to receive the signal Sr.

In another embodiment, if there are multiple coupling paths between the transmitting circuit 170 and the receiving circuit 190, the signal value and the coupling signal of the coupled signal Sc obtained according to the measurement or simulation are obtained. The phase difference between the number Sc and the signal S0, the communication device 100 can use the signal processing circuit 160 or use other signal processing circuits to reduce or cancel the effect of the coupling signal between the transmitting circuit 170 and the receiving circuit 190 on system performance. For example, if the coupling signals of the two coupling paths are to be eliminated, the signal processing circuit 160 can be used to generate a corresponding cancellation signal for the coupled signals of the two coupling paths to reduce or cancel the effects of the coupling signals on the receiving circuit 190. In another embodiment, a plurality of signal processing circuits can be used to generate a cancellation signal corresponding to the coupled signal Sc to reduce or cancel the effects of the coupled signal Sc at the receiving circuit 190.

2 is a simplified functional block diagram of an embodiment of the signal separation circuit 162 of FIG. 1. In the embodiment of FIG. 2, a partial or full function of the signal separation circuit 162 is implemented using a Wilkinson power dividing circuit. As shown, the signal separation circuit 162 includes capacitors 211, 212, and 213, inductors 221 and 222, and a resistor 231. The signal separation circuit 162 is coupled to the transmission circuit 170, the antenna 120, and the phase shift circuit 164 to receive and transmit corresponding signals.

In one embodiment, the signal value of the coupled signal Sc is approximately 1/√2 of the signal value (eg, voltage value, current value, etc.) of the signal S0, and thus the signal separation circuit 162 can employ an equally splitting The Kinsen signal separation circuit separates the signal S0 into two substantially identically sized signals St and S1. For example, when the communication device 100 transmits and receives signals at a frequency near 2.4 GHz, the capacitances 211, 212, and 213 of the signal separation circuit 162 can be set to about 1.9 pF, 1.0 pF, and 1.0 pF, respectively, and the inductors 221 and 222 can be set to Approximately 4.6 nH, and resistor 216 can be set to about 100 ohms to produce two substantially identically sized signals St and S1.

In another embodiment, the signal value of the coupling signal Sc is less than 1/√2 of the signal value of the signal S0, so the signal separation circuit 162 can adopt an inequality (unequally Splitting) The Wigginson signal separation circuit separates the signal S0 into two substantially different sized signals St and S1. In some preferred embodiments, the signal value of the signal S1 generated by the signal separation circuit 162 can be set to be between 1/√2 and 1/100 of the signal value of the signal S0.

3 is a simplified functional block diagram of another embodiment of the signal separation circuit 162 of FIG. 1. In the embodiment of FIG. 3, a partial or full function of signal separation circuit 162 is implemented using a directional coupler circuit to generate signals St and S1 in accordance with signal S0. The signal separation circuit 162 in this embodiment includes six capacitors 311-316, inductors 321 and 322, and a resistor 331.

4 is a simplified functional block diagram of another embodiment of the signal separation circuit 162 of FIG. 1. In the embodiment of FIG. 4, a partial or full function of signal separation circuit 162 is implemented using a hybrid coupler circuit to generate signals St and S1 in accordance with signal S0. The signal separation circuit 162 in this embodiment includes six capacitors 411-416, four inductors 421-424, and a resistor 431.

The above drawings and embodiments have been simplified for ease of illustration and are not intended to limit the scope of the invention. For example, the circuits 160, 162, 164, 166, 170, and/or 190 can be implemented using one or more circuits, and the communication device 100 can also include more antennas and corresponding circuits and the like.

In the various embodiments described above, the values of the passive components of the signal separation circuit 162 can be appropriately set depending on various design considerations. For example, the value of the passive component is adjusted correspondingly according to the size of the coupled signal Sc, the frequency and bandwidth of the transmitted signal, the frequency and bandwidth of the received signal, and/or the required bandwidth of the signal separation circuit 162. Therefore, circuit designers can divide the signal for different application environments. The circuit 162 is adjusted to the most suitable setting.

Since the signal processing circuit 160 can be implemented using only a circuit composed of passive components (eg, capacitors, resistors, and/or inductors, etc.), the occupied area can be reduced. In addition, according to the design considerations such as the size of the coupled signal and the required bandwidth, the required signal processing circuit 160 can be obtained by appropriately setting the value of the passive component, and thus has greater design flexibility. Signal processing circuit 160 can also be used in conjunction with other means of removing coupling effects (eg, spacers and increasing the distance between antennas, etc.) to improve system performance.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should fall within the scope of the present invention.

100‧‧‧Communication device

120, 140‧‧‧ antenna

160‧‧‧Signal Processing Circuit

162‧‧‧Signal separation circuit

164‧‧‧ Phase shifting circuit

166‧‧‧Signal combining circuit

170‧‧‧Transmission circuit

190‧‧‧ receiving circuit

Claims (6)

A signal processing circuit includes: a first node coupled to a first antenna; a second node coupled to a second antenna; and a third node configured to receive a transmission a first signal transmitted by the circuit; a signal separation circuit coupled to the first node and the third node, configured to separate the first signal into a second signal and a third signal, and Transmitting a signal to the first antenna; a phase shifting circuit coupled to the signal separating circuit for changing a phase of the third signal to generate a fourth signal; and a signal combining circuit coupled to the phase shifting a second node for combining the fourth signal and a fifth signal received from the second antenna; and a fourth node for transmitting the fifth signal to a receiving circuit, wherein the The fourth signal can be used to cancel at least a portion of a coupled signal between the third node and the fourth node. The signal processing circuit of claim 1, wherein the signal separation circuit comprises: a first capacitor, comprising a first end for coupling to the transmitting circuit; and a second capacitor comprising a first end for The first capacitor is coupled to the first antenna. The third capacitor includes a first end for coupling to the phase shifting circuit. The resistor includes a first end coupled to the first end of the second capacitor. The first antenna is coupled to the first antenna, and includes a second end coupled to the first end of the third capacitor, and coupled to the phase shifting circuit; The first inductor includes a first end coupled to the first end of the second capacitor and the first end of the resistor, and is coupled to the first antenna, and includes a second end coupled The first end of the first capacitor is coupled to the transmitting circuit; and the second inductor includes a first end coupled to the first end of the third capacitor and the second end of the resistor The second end is coupled to the first end of the first capacitor and the second end of the first inductor, and is coupled to the transmitting circuit. The signal processing circuit of claim 1, wherein the signal separation circuit comprises: a first capacitor, comprising a first end for coupling to the phase shifting circuit; and a second capacitor comprising a first end The first capacitor is coupled to the first antenna; a fourth capacitor is coupled to the first antenna; a fourth capacitor; a resistor; a fifth capacitor includes a first end coupled to the first The first end of a capacitor is coupled to the phase shifting circuit, and includes a second end coupled to the first end of the third capacitor and coupled to the first antenna; The sixth capacitor includes a first end coupled to the first end of the second capacitor and coupled to the transmitting circuit, and a second end coupled to the fourth capacitor and the resistor; The inductor includes a first end coupled to the first end of the first capacitor and the first end of the fifth capacitor, and coupled to the phase shifting circuit, and a second end coupled to the The first end of the second capacitor and the first end of the sixth capacitor are coupled to the first end a transmitting circuit; and a second inductor includes a first end coupled to the first end of the third capacitor and the The second end of the fifth capacitor is coupled to the first antenna, and includes a second end coupled to the fourth capacitor, the resistor, and the second end of the sixth capacitor. The signal processing circuit of claim 1, wherein the signal separation circuit comprises: a first capacitor, comprising a first end for coupling to the phase shifting circuit; and a second capacitor comprising a first end The first capacitor is coupled to the first antenna; the fourth capacitor is coupled to the first antenna; a fourth capacitor; a resistor; a first inductor includes a first end coupled to the first The first end of the first capacitor is coupled to the phase shifting circuit, and includes a second end coupled to the first end of the third capacitor and coupled to the first antenna; The second inductor includes a first end coupled to the first end of the second capacitor and coupled to the transmitting circuit, and a second end coupled to the fourth capacitor and the resistor; The third inductor includes a first end coupled to the first end of the first capacitor and the first end of the first inductor, and coupled to the phase shifting circuit, and including a second end coupled The first end of the second capacitor and the first end of the second inductor are coupled to each other In the transmitting circuit, a fifth capacitor includes a first end coupled to the first end of the third capacitor and the second end of the first inductor, and coupled to the first antenna, and The second capacitor includes a second end coupled to the second end of the fifth capacitor, and a second end coupled to the fourth capacitor, the resistor, and the second inductor The second end of the fifth capacitor includes a first end coupled to the second end of the fifth capacitor and the The first end of the sixth capacitor. The signal processing circuit of claim 1, wherein the signal separation circuit comprises at least one of a Wigginson signal separation circuit, a directional coupler circuit, and a hybrid coupler circuit. The signal processing circuit of claim 1, wherein the phase shifting circuit comprises one or more transmission lines, and/or one or more resistor-capacitor circuits.