Control of transmitter peak power and duty ratio in a wireless system to maintain average transmitter power and increase communication range

• US 8,542,091 B2
• Filed: 04/23/2008
• Issued: 09/24/2013
• Est. Priority Date: 04/26/2007
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Takei, Ken
• Primary Examiner(s): Lim, Steven
• Assistant Examiner(s): BURGDORF, STEPHEN R
• Application Number:
  US12/108,505
• Publication Number:
  US 20080266060A1
• Time in Patent Office: 1,980 Days
• Field of Search: 340/10.1, 340/10.3, 340/10.34, 340/10.4, 340/10.5, 340/12.16, 340/12.17, 340/12.51, 340/14.6, 340/14.66, 340/561, 340/572.1, 340/572.4, 340/572.7, 340/567, 340/5.6, 340/5.61, 340/5.64
• US Class Current: 340/5.61
• 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 wireless system comprising:

a base station and a terminal station,

wherein the base station comprises

a modulator which modulates a carrier to produce a modulated carrier;

a signal generator which generates an output signal possessing an average transmission power not greater than a predetermined value by controlling a peak value and a duty ratio of the modulated carrier simultaneously;

a transmitting unit which transmits the output signal generated; and

a controller which controls 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;

wherein both data transmission and power transmission between the base station and the terminal station are performed using a same carrier waveform,

wherein the controller controls 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,

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

wherein the controller controls 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 reradiated frequency spectrum possesses a frequency component not included in a frequency spectrum of the transmission power of the base station,

wherein the base station further comprises a detector configured to detect the reradiated frequency spectrum of the electromagnetic wave from the terminal station, and of which the reradiated frequency spectrum possesses a frequency component not included in the frequency spectrum of transmission power of the base station,

wherein the controller increases the peak value of the transmission power and decreases the duty ratio of the intermittent transmission, when the frequency spectrum is not detected, if an average power value of the transmission power remains within a predetermined value range,

wherein the wireless system further comprises an equalizing base station antenna and a terminal station antenna, and

wherein a transmitted wave from the base station to the terminal station is transmitted by the equalizing base station antenna which produces, in advance, a distortion of an inverse characteristic to a distortion that the terminal station antenna produces.

2. The wireless system according to claim 1,

wherein the terminal station comprises a modulator which modulates the transmission power to be radiated by the base station.

3. The wireless system according to claim 1,

wherein the controller decreases the peak value of the transmission power and increases the duty ratio of intermittent transmission, when the frequency spectrum is detected, if an average power value of the transmission power remains within a predetermined value range.

4. The wireless system according to claim 1,

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

wherein the terminal station further comprises a receiver which receives, from a terminal station antenna, the transmission power transmitted by the base station, rectifies with the rectifier circuit a high frequency power which is an actual aspect of the transmission power, and uses the rectified high frequency power as a power source for an electronic circuit which composes the terminal station.

5. The wireless system according to claim 4,

wherein the rectifying element is a Schottky barrier diode.

6. The wireless system according to claim 1,

wherein the equalizing base station antenna and the terminal station antenna are in the form of a wideband antenna.

7. The wireless system according to claim 6,

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

8. The wireless system according to claim 1,

wherein the terminal station antenna is a resonance type antenna.

9. The wireless system according to claim 1,

wherein the terminal station comprises a rectifier circuit including a diode, and

wherein the controller maintains the transmission power of the base station below a fixed value, thereby allowing a voltage to be applied to the diode which is always in excess of a threshold voltage of the diode, and such that energy is exchanged between the base station and the terminal station below a limit power.