CN103580712B - Signal Transceiver and Adaptive Impedance Switching Circuit - Google Patents

Abstract

The invention discloses a signal transceiver, which comprises a connector, a band-pass filter, a front-end module and an adaptive impedance switching circuit, wherein the connector is used for receiving a signal, the band-pass filter is coupled to the connector and used for filtering the signal, the front-end module is used for demodulating the signal, and the adaptive impedance switching circuit is coupled between the band-pass filter and the front-end module and used for switching an impedance value between the band-pass filter and the front-end module.

Description

Signal Transceiver and Adaptive Impedance Switching Circuit

technical field

The present invention refers to a signal transceiver and an adaptive impedance switching circuit, in particular to a signal transceiver and an adaptive impedance switching circuit that can effectively improve return loss (return loss) in a power-off state.

Background technique

Ethernet over Coax (EoC) is a transmission technology of Ethernet signals on coaxial cables. Its purpose is to use the existing cable TV infrastructure to connect to the Internet or broadband data transmission. , Compatible with existing cable TV (or satellite TV) broadcasting signals, achieving the purpose of transmitting data signals on the same coaxial cable at the same time. Among them, the multimedia network standard formulated by the Multimedia over Coax Alliance (MoCA) has high-speed and high-quality-of-service (QoS) functions required for glitch-free streaming media, etc., through the existing The coaxial cable sends the signal to each user end, and the user end only needs a signal transceiver to demodulate the signal to obtain the service content.

Please refer to FIG. 1 , which is a schematic diagram of a conventional signal transceiver 10 . The signal transceiver 10 includes a connector 100 , a band-pass filter (BPF) 102 and a front-end module 104 . Usually, the signal transceiver 10 is realized by a set-top box (set-top box, STB) product. The connector 100 is connected to a coaxial cable, and is used for receiving signals transmitted through the coaxial cable, including signals conforming to Multimedia Coaxial Cable Alliance (hereinafter referred to as MoCA signals). A band-pass filter (band-pass filter, BPF) 102 is used to filter signals, so as to filter out signals within a frequency band. For example, the frequency band of the MoCA signal provided by DIRECTV ^TM , a satellite TV service provider in the United States, ranges from 475 MHz to 625 MHz. If only the MoCA signal needs to be retained, the filtering frequency range of the bandpass filter 102 should be set to 475MHz to 625MHz. The front-end module 104 is used for demodulating the signal passing through the band-pass filter 102 . Generally speaking, the front-end module 104 includes circuits such as a transmission receiver, a power amplifier, and an attenuator, and the front-end module 104 is usually integrated into an integrated circuit (IC).

Please refer to FIG. 2A and FIG. 2B . FIG. 2A and FIG. 2B are the signal transceiver 10 in the power-on state and in the power-off state respectively, and in the frequency band of 475MHz-625MHz, the coaxial cable connected to the connector 100 A schematic diagram of the return loss between (not shown in the figure) and the connector 100 . Comparing FIG. 2A with FIG. 2B, it can be seen that in the frequency band of 475 MHz to 625 MHz, the minimum return loss of the signal transceiver 10 in the power-off state is close to 7.6 dB, which is smaller than the minimum return loss of the signal transceiver 10 in the power-on state ( close to 11dB) about 3.4dB. From the above, it can be seen that if the signal transceiver 10 is operated in the power-off state, the system performance will indeed be deteriorated.

Contents of the invention

Therefore, the main purpose of the present invention is to provide a signal transceiver and an adaptive impedance switching circuit, which can effectively increase the return loss when the power is turned off.

The present invention discloses a signal transceiver, comprising a connector for receiving a signal; a bandpass filter coupled to the connector for filtering the signal; a front-end module for demodulating the signal; and An adaptive impedance switching circuit, coupled between the band-pass filter and the front-end module, is used to switch an impedance value between the band-pass filter and the front-end module.

In addition, the present invention also discloses an adaptive impedance switching circuit for switching an impedance value in a signal transceiver. The adaptive impedance switching circuit includes: an input end for receiving a signal; an output end for to output the signal; a voltage input circuit, used to provide an input voltage; a frequency resonance circuit, coupled to the input terminal and the voltage input circuit, used to adjust the impedance value; and a bias circuit, coupled between the input terminal, a node connected to the voltage input circuit and the frequency resonance circuit, and the output terminal, for converting a voltage of the signal value.

Description of drawings

FIG. 1 is a schematic diagram of a conventional signal transceiver.

FIG. 2A is a schematic diagram of return loss between a coaxial cable connected to a connector and the connector in a specific frequency band when the signal transceiver of FIG. 1 is powered on.

FIG. 2B is a schematic diagram of the return loss between the coaxial cable connected with the connector and the connector in a specific frequency band when the power of the signal transceiver of FIG. 1 is turned off.

FIG. 3 is a schematic diagram of a signal transceiver according to an embodiment of the present invention.

FIG. 4A is a schematic diagram of the adaptive impedance switching circuit of FIG. 3 .

FIG. 4B is a schematic diagram of the direction of current in the adaptive impedance switching circuit of FIG. 3 when the switch is turned on.

FIG. 4C is a schematic diagram of the direction of current in the adaptive impedance switching circuit of FIG. 3 when the switch is switched to an off state.

FIG. 5A is a schematic diagram of the return loss between the bandpass filter and the front-end module in a specific frequency band when the signal transceiver of FIG. 3 is powered on.

FIG. 5B is a schematic diagram of the return loss between the bandpass filter and the front-end module in a specific frequency band when the signal transceiver of FIG. 3 is in a power-off state.

FIG. 6A is a schematic diagram of the return loss between the coaxial cable connected with the connector and the connector in a specific frequency band when the signal transceiver of FIG. 3 is powered on.

FIG. 6B is a schematic diagram of the return loss between the coaxial cable connected with the connector and the connector in a specific frequency band when the power of the signal transceiver of FIG. 3 is turned off.

Description of main component symbols:

10, 30 Signal Transceiver

100, 300 Connectors

102, 302 bandpass filter

104, 306 Front-end modules

304 Adaptive Impedance Switching Circuit

400 input terminal

402 output terminal

404 Voltage input circuit

406 Frequency Resonant Circuit

408 Bias circuit

410 Voltage input terminal

Vcc Input Voltage

SW Switcher

R1, R2, R3, R4 resistors

C1, C2, C3 capacitors

L1 Inductance

D1, D2, D3 switch

Detailed ways

Please refer to FIG. 3 , which is a schematic diagram of a signal transceiver 30 according to an embodiment of the present invention. The signal transceiver 30 includes a connector 300 , a bandpass filter 302 , an adaptive impedance switching circuit 304 and a front-end module 306 . The connector 300 , the bandpass filter 302 , and the front-end module 306 are respectively the same as the connector 100 , the bandpass filter 102 , and the front-end module 104 of the conventional signal transceiver 10 , and will not be repeated here. The adaptive impedance switching circuit 304 is coupled to the bandpass filter 302 and the front-end module 306 for switching the impedance between the bandpass filter 302 and the front-end module 306 .

For an implementation of the adaptive impedance switching circuit 304 , please refer to FIG. 4A . The adaptive impedance switching circuit 304 includes an input terminal 400 , an output terminal 402 , a voltage input circuit 404 , a frequency resonance circuit 406 and a bias voltage circuit 408 . The input terminal 400 is coupled to the band-pass filter 302 for receiving the signal passing through the band-pass filter 302 . The output terminal 402 is coupled to the front-end module 306 for outputting the signal passing through the band-pass filter 302 to the front-end module 306 . The voltage input circuit 404 is used to provide an input voltage Vcc, and includes a voltage input terminal 410, a switch SW and a resistor R1. Wherein, the voltage input terminal 410 is used to receive the input voltage Vcc, the switch SW is used to switch the state of the voltage input circuit 404 , and the resistor R1 is coupled to the switch SW. The frequency resonance circuit 406 is coupled to the input terminal 400 and the voltage input circuit 404 for adjusting the impedance between the bandpass filter 302 and the front-end module 306 . The frequency resonance circuit 406 includes resistors R2, R3, capacitors C1, C2, C3, inductor L1, and switches D2, D3. The bias circuit 408 is coupled between a node connected to the input terminal 400 , the voltage input circuit 404 and the frequency resonance circuit 406 and the output terminal 402 for converting the voltage value of the signal. The bias circuit 408 includes a resistor R4 and a switch D1. The aforementioned switches D1 , D2 , D3 are preferably implemented using diodes, and the resistance value of the resistor R2 can be determined according to an element connected to the connector 300 , such as a coaxial cable.

FIG. 4B and FIG. 4C respectively illustrate the current direction of the adaptive impedance switching circuit 304 when the switch SW is switched to the on state and the off state. As shown in Figure 4B, when the switch SW is switched to the on state (that is, the power is on), the switches D1, D2, and D3 are all in the on state, so the current has two directions (as shown by the arrows), one of which is One is to flow through the switch D1, and the other is to flow through the resistor R2, the switch D2, the capacitor C2, and the switch D3 to the ground. The capacitor C3 can be designed to use a larger capacitance value, and the resistor R3 can be designed to use a larger resistance value to avoid the situation of reverse current flow. As shown in Figure 4C, when the switch SW switches to the open circuit state (that is, the power off state), the switches D1, D2, and D3 are all in a non-conducting state, so the current flows along the direction of the resistor R2, the inductor L1, and the capacitor C1 to The ground terminal (as indicated by the arrow), that is to say, the path formed by the resistor R2, the inductor L1 and the capacitor C1 is in a short circuit state.

The adaptive impedance switching circuit 304 of the embodiment of the present invention is an independent circuit coupled between the bandpass filter 302 and the front-end module 306 . However, it should be noted that the adaptive impedance switching circuit 304 can also be integrated with the front-end module 306 into an integrated circuit.

Please refer to FIG. 5A and FIG. 5B . FIG. 5A and FIG. 5B respectively show the signal transceiver 30 in the power-on state and in the power-off state, and in the frequency band of 475MHz-625MHz, the band-pass filter 302 and the front-end module 306. A schematic diagram of the return loss between. Comparing FIG. 5A with FIG. 5B, it can be seen that in the frequency band of 475 MHz to 625 MHz, the minimum return loss of the signal transceiver 30 in the power-off state is close to 20 dB, which is greater than the minimum return loss of the signal transceiver 30 in the power-on state (approximately 11dB) about 9dB. It can be known from the above that when the signal transceiver 30 operates in the power-off state, the return loss between the bandpass filter 302 and the front-end module 306 will increase.

Please refer to FIG. 6A and FIG. 6B. FIG. 6A and FIG. 6B are the signal transceiver 30 in the power-on state and in the power-off state respectively, and in the frequency band of 475MHz-625MHz, the coaxial cable connected to the connector 300 A schematic diagram of the return loss between (not shown in the figure) and the connector 300 . Comparing FIG. 6A with FIG. 6B, it can be seen that in the frequency band of 475 MHz to 625 MHz, the minimum return loss of the signal transceiver 30 in the power-off state is close to 11.5 dB, which is greater than the minimum return loss of the signal transceiver 30 in the power-on state ( close to 11dB) about 0.5dB. It can be seen from the above that when the signal transceiver 30 operates in the power-off state, the return loss between the bandpass filter 302 and the front-end module 306 can be maintained above the minimum return loss in the power-on state.

It should be noted that the above-mentioned FIG. 5B and FIG. 6B are only shown in the frequency band of 475MHz˜625MHz, and the minimum return loss of the signal transceiver 30 in the power-off state can be effectively increased. Those skilled in the art can adjust the characteristics of each element according to different frequency bands, so that the minimum return loss in different frequency bands can be effectively increased.

It is known that when the power of the signal transceiver is turned off, the return loss will be reduced, resulting in poor system performance. In contrast, the signal transceiver of the present invention can switch the impedance between the band-pass filter and the front-end module in the power-off state through the adaptive impedance switching circuit, thereby effectively improving the return loss.

To sum up, the signal transceiver of the present invention can effectively improve the return loss when the power is turned off, thereby improving the system performance.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the present invention.

Claims (12)

1. A signal transceiver, said signal transceiver comprising:

a connector for receiving a signal;

a band pass filter coupled to the connector for filtering the signal;

a front-end module for demodulating said signal; and

an adaptive impedance switching circuit, coupled between the band-pass filter and the front-end module, for switching an impedance value between the band-pass filter and the front-end module; wherein,

the adaptive impedance switching circuit comprises:

an input terminal coupled to the band pass filter for receiving the signal;

an output end coupled to the front end module for outputting the signal to the front end module;

a voltage input circuit for providing an input voltage;

a frequency resonance circuit, coupled to the input terminal and the voltage input circuit, for adjusting the impedance value; and

a bias circuit coupled between a node of the input terminal, the voltage input circuit, and the frequency resonant circuit and the front-end module for converting a voltage value of the signal.

2. The signal transceiver of claim 1, wherein the voltage input circuit comprises:

a voltage input terminal for receiving said input voltage;

a switch coupled to the voltage input terminal for switching a state of the voltage input circuit; and

a first resistor is coupled to the switch.

3. The signal transceiver of claim 1, wherein the frequency resonant circuit comprises:

a second resistor, one end of which is coupled to the voltage input circuit and the input end;

an inductor, one end of which is coupled to the second resistor;

a first capacitor, one end of which is coupled to the inductor;

a first switch, one end of which is coupled between the second resistor and the inductor;

a second capacitor, one end of which is coupled to the first switch;

a second switch, one end of which is coupled to the second capacitor; and

and a third capacitor, one end of which is coupled between the inductor and the first capacitor and the other end of which is coupled between the second capacitor and the second switch.

4. The signal transceiver of claim 3, wherein said signal transceiver further comprises:

and the third resistor is connected in parallel with the second capacitor.

5. The signal transceiver of claim 3, wherein a resistance value of the second resistor is determined according to an element connected to the connector.

6. The signal transceiver of claim 1, wherein the bias circuit comprises:

a third switch; and

a fourth resistor coupled between the third switch and the output terminal.

7. An adaptive impedance switching circuit for switching an impedance value in a signal transceiver, the adaptive impedance switching circuit comprising:

an input terminal for receiving a signal;

an output terminal for outputting said signal;

a voltage input circuit for providing an input voltage;

a frequency resonance circuit, coupled to the input terminal and the voltage input circuit, for adjusting the impedance value; and

a bias circuit coupled between a node of the input terminal, the voltage input circuit, and the frequency resonant circuit and the output terminal for converting a voltage value of the signal.

8. The adaptive impedance switching circuit of claim 7, wherein the voltage input circuit comprises:

a voltage input terminal for receiving said input voltage;

a switch coupled to the voltage input terminal for switching a state of the voltage input circuit; and

a first resistor is coupled to the switch.

9. The adaptive impedance switching circuit of claim 7, wherein the frequency resonant circuit comprises:

a second resistor, one end of which is coupled to the voltage input circuit and the input end;

an inductor, one end of which is coupled to the second resistor;

a first capacitor, one end of which is coupled to the inductor;

a first switch, one end of which is coupled between the second resistor and the inductor;

a second capacitor, one end of which is coupled to the first switch;

a second switch, one end of which is coupled to the second capacitor; and

and a third capacitor, one end of which is coupled between the inductor and the first capacitor and the other end of which is coupled between the second capacitor and the second switch.

10. The adaptive impedance switching circuit of claim 9, wherein the adaptive impedance switching circuit further comprises:

and the third resistor is connected in parallel with the second capacitor.

11. The adaptive impedance switching circuit of claim 9, wherein a resistance value of the second resistor is determined based on an element connected to the signal transceiver.

12. The adaptive impedance switching circuit of claim 7, wherein the bias circuit comprises:

a third switch; and

a fourth resistor coupled between the third switch and the output terminal.