Signal strength detecting device and related method

• US 8,121,572 B2
• Filed: 07/23/2010
• Issued: 02/21/2012
• Est. Priority Date: 03/10/2010
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: Lin, Ying-Yao, Liu, Ren-Chieh
• Primary Examiner(s): Jackson, Blane J
• Application Number:
  US12/842,054
• Publication Number:
  US 20110223878A1
• Time in Patent Office: 578 Days
• Field of Search: 455/226.1, 455/226.2, 455/226.3, 455/232.1, 455/234.1, 455/234.2, 455/241.1, 455/245.2, 455/250.1, 455/323, 455/324, 455/334
• US Class Current: 455/232.1
• CPC Class Codes: H03G 3/3068 Circuits generating control signals for both R.F. and I.F. stages
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 17/318 Received signal strength

Abstract

A signal strength detecting device of a communication system is disclosed. The signal strength detecting device is coupled to a frequency down mixer of the communication system and the frequency down mixer is used for receiving and converting a first signal to a second signal whose frequencies are lower than frequencies of the first signal. The signal strength detecting device comprises a frequency up converter for receiving and converting the second signal to a third signal whose frequencies are higher than the frequencies of the second signal and a detecting unit for detecting strength of the third signal and generating a signal strength indicator to the communication system according to a detecting result corresponding to the strength of the third signal, wherein the signal strength indicator represents the strength of the first signal received by the frequency down mixer.

Claims

1. A signal strength detecting device of a communication system, the signal strength detecting device coupled to a frequency down mixer of the communication system, the frequency down mixer used for receiving and converting a first signal to a second signal whose frequencies are lower than frequencies of the first signal, the signal strength detecting device comprising:

a frequency up converter for receiving and converting the second signal to a third signal whose frequencies are higher than the frequencies of the second signal; and

a detecting unit for detecting strength of the third signal and generating a signal strength indicator to the communication system according to a detecting result corresponding to the strength of the third signal, wherein the signal strength indicator represents the strength of the first signal received by the frequency down mixer.

2. The signal strength detecting device of claim 1, wherein the communication system comprises an auto gain control (AGC) circuit for adjusting the strength of the first signal received by the frequency down mixer according to the signal strength indicator.

3. The signal strength detecting device of claim 1, wherein the frequency down mixer converts the first signal to the second signal by a central frequency, and the frequency up mixer converts the second signal to the third signal by the central frequency, wherein the central frequency is a central frequency of a received signal corresponding to the first signal.

4. The signal strength detecting device of claim 1, wherein the frequency down mixer further executes single-sideband modulation (SBB) for the second signal, and the frequency up mixer further executes the SBB for the third signal.

5. The signal strength detecting device of claim 1, wherein the detecting unit comprises;

an amplifier having a first input terminal for receiving the third signal, a second input terminal and an output terminal;

a transistor having a gate coupled to the output terminal of the amplifier, a drain and a source coupled to the second input terminal;

a current source coupled between a ground and the source of the transistor;

a resistor having a first terminal coupled to the source of the transistor and a second terminal; and

a capacitor having a first terminal coupled to the ground and a second terminal coupled to the second terminal of the resistor, the second terminal for outputting peak strength of the third signal.

6. A signal strength detecting method for a signal strength detecting device of a communication system, the signal strength detecting device coupled to a frequency down mixer for receiving and converting a first signal to a second signal whose frequencies are lower than frequencies of the first signal, the signal strength detection method comprises :

receiving and converting the second signal to a third signal whose frequencies are higher than frequencies of the second signal;

detecting strength of the third signal; and

generating a signal strength indicator to the communication system according to a detecting result corresponding to the strength of the third signal, wherein the signal strength indicator represents strength of the first signal received by the frequency down mixer.

7. The signal strength detecting method of claim 6, wherein the communication system comprises an auto gain control (AGC) circuit for adjusting strength of the first signal received by the frequency down mixer according to the signal strength indicator.

8. The signal strength detecting method of claim 6, wherein the first signal is converted to the second signal according to a central frequency and receiving and converting the second signal to a third signal comprises receiving and then converting the second signal to the third signal by the central frequency, wherein the central frequency is a central frequency of a received signal corresponding to the first signal.

9. The signal strength detecting method of claim 6 further comprises executing single-sideband modulation (SBB) for the second signal and the third signal.

10. A communication system comprising:

a signal reception circuit;

a signal transmission circuit;

a frequency down mixer installed in the signal transmission circuit, for receiving and converting a first signal to a second signal whose frequencies are lower than frequencies of the first signal;

a frequency up mixer installed in the signal transmission circuit and coupled to the frequency down mixer, for receiving and converting the second signal to a third signal whose frequencies are higher than frequencies of the second signal when the communication system does not transmit any signal; and

a detecting unit coupled to the frequency up mixer, for detecting strength of the third signal and generating a signal strength indicator according to a detecting result corresponding to the strength of the third signal, wherein the signal strength indicator represents a strength of the first signal received from the frequency down mixer.

11. The communication system of claim 10 further comprising an auto gain control (AGC) circuit coupled to the detecting unit and the frequency down mixer, for adjusting strength of the first signal received by the frequency down mixer according to the signal strength indicator.

12. The communication system of claim 10, wherein the frequency down mixer converts the first signal to the second signal by a central frequency and the frequency up mixer converts the second signal to the third signal by the central frequency, wherein the central frequency is a central frequency of a received signal corresponding to the first signal.

13. The communication system of claim 10, wherein the frequency down mixer further executes single-sideband modulation (SBB) for the second signal and the frequency up mixer further executes SBB for the third signal.

14. The communication system of claim 10, wherein the detecting unit comprises:

an amplifier having a first input terminal for receiving the third signal, a second input terminal and an output terminal;

a transistor having a gate coupled to the output terminal of the amplifier, a drain and a source coupled to the second input terminal;

a current source coupled between a ground and the source of the transistor;

a resistor having a first terminal coupled to the source of the transistor and a second terminal; and

a capacitor having a first terminal coupled to the ground and a second terminal coupled to the second terminal of the resistor, the second terminal for outputting peak strength of the third signal.

15. A signal strength detecting method for a communication system, the signal strength detecting method comprises:

receiving and converting a first signal to a second signal whose frequencies are lower than frequencies of the first signal, in a signal reception circuit of the communication system;

receiving and converting the second signal to a third signal whose frequencies are higher than frequencies of the second signal when the communication system does not transmit any signal, in a signal transmission circuit of the communication system;

detecting strength of the third signal; and

generating a signal strength indicator according to a detecting result corresponding to the strength of the third signal, wherein the signal strength indicator represents strength of the first signal received by a frequency down mixer of the signal transmission circuit.

16. The signal strength detecting method of claim 15, wherein the communication system comprises an auto gain control (AGC) circuit for adjusting strength of the first signal received by the frequency down mixer according to the signal strength indicator.

17. The signal strength detecting method of claim 15, wherein receiving and converting the first signal to the second signal comprises converting the first signal to the second signal by a central frequency;

and receiving and converting the second signal to the third signal comprises converting the second signal to the third signal by the central frequency, wherein the central frequency is a central frequency of a received signal corresponding to the first signal.

18. The signal strength detecting method of claim 15 further comprises:

executing single-sideband modulation (SBB) for the second signal in the signal reception circuit; and

executing SBB for the third signal in the signal transmission circuit.

19. A signal strength detecting device of a communication system comprising a signal reception circuit including a frequency down mixer and a signal transmission circuit including a frequency up mixer, the signal strength detecting device coupled to the frequency down mixer for receiving and converting a first signal to a second signal whose frequencies are lower than frequencies of the first signal, the signal strength detecting device comprising:

a frequency up mixer for receiving and converting the second signal to a third signal whose frequencies are higher than frequencies of the second signal; and

a detecting unit for detecting strength of the third signal and generating a signal strength indicator to the communication system according a detecting result corresponding to the strength of the third signal, wherein the strength of the third signal represents strength of the first signal received by the frequency down mixer.

20. The signal strength detecting device of claim 19, wherein the communication system has an auto gain control (AGC) mechanism and adjusts the strength of the first signal received by the frequency down mixer according to the signal strength indicator.

21. The signal strength detecting device of claim 19, wherein the frequency down mixer converts the first signal to the second signal by a central frequency and the frequency up mixer converts the second signal to the third signal by the central frequency, wherein the central frequency is a central frequency of a received signal corresponding to the first signal.

22. The signal strength detecting device of claim 19, wherein the frequency down mixer further executes single-sideband modulation (SBB) for the second signal and the frequency up mixer further executes SBB for the third signal.