TRANSMITTER AND WIRELESS SYSTEM USING THE SAME

• US 20080266060A1
• Filed: 04/23/2008
• Published: 10/30/2008
• Est. Priority Date: 04/26/2007
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: TAKEI, Ken
• Granted Patent: US 8,542,091 B2
• Time in Patent Office: Days
• US Class Current: 340/10.4
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10217 parameter settings controlling the transmission power of the interrogator

Abstract

When supplying a power from a base station to a terminal station on radio and a distance from a base station to a terminal station is long, it becomes impossible for the terminal station to rectify the power. The feature of the present invention is found in a wireless communication system in which the peak value and duty ratio of a transmission power are controlled simultaneously, keeping the transmission power of a base station below a fixed value, thereby allowing a voltage to be applied to a diode, which is a component of a rectifier circuit possessed by a terminal station, always in excess of a threshold voltage of the diode, and energy is exchanged between the base station and the terminal station below a limit power.

Claims

1. A transmitter comprising:

a unit for performing modulation of a carrier to produce a modulated carrier;

a unit for generating an output signal with an average transmission power not greater than a predetermined value by controlling a peak value and a duty radio of the modulated carrier simultaneously; and

a unit for transmitting the output signal generated.

2. The transmitter according to claim 1, further comprising:

a unit for detecting a change of the transmission output of the output signal due to a communication target outside the transmitter concerned in terms of a reflective wave; and

a unit for controlling the peak value and the duty ratio in accordance with the change.

3. The transmitter according to claim 1,

wherein the modulation is amplitude modulation.

4. The transmitter according to claim 3,

wherein the amplitude modulation is performed by on/off switching of the carrier.

5. The transmitter according to claim 2,

wherein the transmitter employs an electromagnetic wave propagating space as communication media, and

wherein the transmitter further comprises a unit for controlling the peak value and the duty ratio, by using a frequency spectrum of an electromagnetic wave which is generated when the transmission output is reradiated by a communication target outside the transmitter concerned, and of which the frequency spectrum possesses a frequency component not included in a frequency spectrum of transmission power of the transmitter concerned.

6. The transmitter according to claim 2,

wherein the transmitter employs an electromagnetic wave propagating space as communication media, and

wherein the transmitter further comprises:

a unit for tentatively detecting a frequency spectrum of an electromagnetic wave which is generated when the transmission output is reradiated by a communication target outside the transmitter concerned, and of which the frequency spectrum possesses a frequency component not included in a frequency spectrum of transmission power of the transmitter concerned; and

a unit for performing control to increase the peak value of the transmission power and to decrease the duty ratio of intermittent transmission, when the frequency spectrum is not detected, on the condition that an average power value of the transmission power is kept within a predetermined value.

7. The transmitter according to claim 2,

wherein the transmitter employs an electromagnetic wave propagating space as communication media, and

wherein the transmitter further comprises:

a unit for tentatively detecting a frequency spectrum of an electromagnetic wave which is generated when the transmission output is reradiated by a communication target outside the transmitter concerned, and of which the frequency spectrum possesses a frequency component not included in a frequency spectrum of transmission power of the transmitter concerned; and

a unit for performing control to decrease the peak value of the transmission power and to increase the duty ratio of intermittent transmission, when the frequency spectrum is detected, on the condition that an average power value of the transmission power is kept within a predetermined value.

8. A wireless system comprising a base station and a terminal station,

wherein the base station comprises:

a unit for performing modulation of a carrier to produce a modulated carrier;

a unit for generating an output signal possessing an average transmission power not greater than a predetermined value by controlling a peak value and a duty radio of the modulated carrier simultaneously;

a unit for transmitting the output signal generated; and

a unit for controlling the peak value and the duty ratio, in terms of a power of a reflected wave which is generated when the transmission power transmitted by the base station is reradiated by the terminal station.

9. The wireless system according to claim 8,

wherein the terminal station comprises a unit for performing modulation to the transmission power to be radiated by the base station.

10. The wireless system according to claim 8,

wherein the base station further comprises a unit for controlling the peak value of the transmission output received by the terminal station to constantly exceed a threshold value of a rectifying element of the terminal station, and

wherein the wireless system employs an electromagnetic wave propagating space as communication media, and performs a waveform-equalized intermittent transmission between the base station and the terminal station.

11. The wireless system according to claim 8,

wherein the base station further comprises a unit for controlling the peak value and the duty ratio using a frequency spectrum of an electromagnetic wave which is reradiated from the terminal station, and of which the frequency spectrum possesses a frequency component not included in a frequency spectrum of transmission power of the base station concerned.

12. The wireless system according to claim 11,

wherein the base station further comprises:

a unit for tentatively detecting a frequency spectrum of an electromagnetic wave which is reradiated by the terminal station, and of which the frequency spectrum possesses a frequency component not included in a frequency spectrum of transmission power of the base station concerned; and

a unit for performing control to increase the peak value of the transmission power and to decrease the duty ratio of intermittent transmission, when the frequency spectrum is not detected, on the condition that an average power value of the transmission power is kept within a predetermined value.

13. The wireless system according to claim 11,

wherein the base station further comprises:

a unit for tentatively detecting a frequency spectrum of an electromagnetic wave which is reradiated by the terminal station, and of which the frequency spectrum possesses a frequency component not included in a frequency spectrum of transmission power of the base station concerned; and

a unit for performing control to decrease the peak value of the transmission power and to increase the duty ratio of intermittent transmission, when the frequency spectrum is detected, on the condition that an average power value of the transmission power is kept within a predetermined value.

14. The wireless system according to claim 8,

wherein the terminal station comprises a rectifier circuit including a rectifying element, and

wherein the wireless system further comprises a unit for taking in, from a terminal station antenna, the transmission power transmitted by the base station, rectifying with the rectifier circuit a high frequency power which is an actual aspect of the transmission power, and using the rectified high frequency power as a power source for an electronic circuit which composes the terminal station.

15. The wireless system according to claim 14,

wherein the rectifying element is a Schottky barrier diode.

16. The wireless system according to claim 8,

wherein an antenna of the base station and an antenna of the terminal station are a wideband antenna.

17. The wireless system according to claim 8,

wherein the wireless system further comprises a unit in which a frequency spectrum at a feeding point of the base station antenna compensates distortion of a frequency spectrum of transmission power of the base station, the distortion being induced by a frequency spectrum at a feeding point of the terminal station antenna.

18. The wireless system according to claim 16,

wherein the antenna of the base station and the antenna of the terminal station are a circularly-polarized-wave antenna.

19. A wireless system comprising an RFID tag and a reader of the RFID tag,

wherein the reader comprises:

a unit for performing a digital modulation to a carrier to produce a digital-modulated carrier;

a unit for generating an output signal with an average transmission power not greater than a predetermined value, by controlling a peak value and a duty ratio of the digital-modulated carrier;

a unit for transmitting the output signal; and

a unit for controlling the peak value and the duty ratio in terms of a power of a reflected wave of which the transmission power transmitted by the reader is reradiated by the RFID tag.

20. The wireless system according to claim 19,

wherein a size of an antenna possessed by the reader is greater than a size of an antenna possessed by the RFID tag.