Apparatus and method for sensing a rearward facing child seat using beat frequency detection

• US 6,266,592 B1
• Filed: 10/11/1996
• Issued: 07/24/2001
• Est. Priority Date: 10/11/1996
• Status: Expired due to Fees

• Current Assignee: TRW Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: TRW Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: LeMense, Thomas John
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Arthur, Gertrude
• Application Number:
  US08/730,674
• Time in Patent Office: 1,747 Days
• Field of Search: 701/45, 701/49, 280/734, 280/735, 180/273, 180/272, 180/271, 340/436, 340/903, 307/10.1, 342/72, 342/107
• US Class Current: 701/45
• CPC Class Codes: B60N 2/0268 using sensors or detectors for adapting the seat or seat part, e.g. to the position of an occupant
• CPC Class Codes: B60N 2/0276 reaction to emergency situations, e.g. crash
• CPC Class Codes: B60N 2/28 Seats readily mountable on, and dismountable from, existing seats or other parts of the vehicle
• CPC Class Codes: B60N 2/2863 backward facing
• CPC Class Codes: G01S 13/04 Systems determining presence of a target based on relative movement of target G01S13/56
• CPC Class Codes: G06F 7/68 using pulse rate multipliers or dividers pulse rate multipliers or dividers per seG06F7/70 takes precedence ; frequency division in electronic watches G04G3/02; frequency multiplication or division in oscillators H03B19/00; frequency dividing counters per se H03K23/00 - H03K29/00

Abstract

An apparatus (52) senses the presence of a rearward facing child restraint seat (34) in a vehicle. Signal generating components (80, 84 and 90) of a driver/receiver circuit (64) provide an electrical transmit signal, at a first frequency, which is applied to an antenna (60) during a first time period. The antenna (60) transmits an electromagnetic (EM) signal (62) at the first frequency during the first time period. At the end of the first time period, the EM transmit signal (62) is terminated. During a second time period, a component (84) of the driver/receiver circuit (64) provides a signal at a second, different frequency. An identification tag (54) is securable to the child restraint seat (34) and provides an EM return signal (68) in response to the EM transmit signal (62). The EM return signal (68) has the same frequency as the EM transmit signal (62) and continues past the termination of the EM transmit signal into the second time period. The antenna (60) receives the EM return signal (68) and provides an electrical return signal in response to the EM return signal. A mixer (122) is coupled to receive both the second frequency signal and the electrical return signal in the second time period, and provides a beat frequency signal. The presence and duration of the best frequency signal is indicative of the presence of the identification tag (54).

Claims

1. An apparatus for sensing the presence of an object, said apparatus comprising:

transmitter means for providing a transmitted electromagnetic signal;

receiver means for receiving an electromagnetic return signal;

identifier means securable to the object for providing said electromagnetic return signal at a first frequency in response to said transmitted electromagnetic signal;

second signal means for providing a signal at a second frequency, different from said first frequency;

combiner means for mixing signals having said first frequency from said return signal and said second frequency to provide a beat signal having a beat frequency; and

processor means coupled to receive said beat signal for determining the presence of said identifier means when a predetermined beat frequency is received and providing a signal indicative thereof.

2. An apparatus as set forth in claim 1 further including means to secure said identifier means to a child restraining seat.

3. An apparatus as set forth in claim 1, wherein said transmitter means includes signal provider means for providing an electrical signal having said first frequency for a first time period and an electrical signal having said second frequency for a second, different time period, said signal provider means being said second signal means.

4. An apparatus as set forth in claim 3, wherein said receiver means includes means for providing an electrical signal having said first frequency responsive to said electromagnetic return signal, and said combiner means includes means for mixing said electrical signal having said second frequency provided by said signal provider means and said electrical signal having said first frequency provided by said receiver means.

5. An apparatus as set forth in claim 4, wherein said beat signal provided by said combiner means exists for at least a predetermined duration.

6. An apparatus as set forth in claim 1, wherein said beat frequency is approximately equal to the difference between said first and second frequencies.

7. An apparatus as set forth in claim 1, wherein said beat signal provided by said combiner means has a duration longer than a predetermined time duration when said identifier means is present.

8. An apparatus as set forth in claim 1 further includes means for disabling an actuatable restraining device in a vehicle when said identifier means is determined to be present.

9. A method for sensing the presence of an object, said method comprising:

securing an identifier means to the object;

transmitting an electromagnetic signal;

providing an electromagnetic return signal from the identifier means in response to the transmitted electromagnetic signal, the electromagnetic return signal having a first frequency;

receiving the electromagnetic identifier return signal;

providing a signal at a second frequency, different from said first frequency;

mixing signals having the first frequency from said return signal and the second frequency to provide a beat signal having a beat frequency;

receiving the beat signal;

determining the presence of the identifier means when a predetermined beat frequency in the beat signal is present; and

providing a signal indicative of the presence of the identifier means.

10. A method as set forth in claim 9, wherein the step of securing includes securing the identifier means to a child restraining seat.

11. The method of claim 9, wherein said step of determining includes the step of determining if said beat frequency is approximately equal to the difference between said first and second frequencies.

12. The method of claim 9, wherein said step of determining determines whether said beat frequency is equal to a predetermined frequency.

13. The method of claim 12, wherein said determining step further includes determining if said beat frequency exists for a predetermined time period.

14. An apparatus for sensing the presence of an object, said apparatus comprising:

signal means for providing a first electrical signal having a first frequency during a first time period and a second electrical signal having a second frequency during a second, different time period;

antenna means for transmitting an electromagnetic signal at the first frequency during the first time period in response to said first electrical signal and for providing an electrical return signal in response to a received electromagnetic return signal;

identifier means securable to the object for providing said electromagnetic return signal in response to said transmitted electromagnetic signal, said electromagnetic return signal continuing for a time duration past the termination of said transmitted electromagnetic signal;

combiner means for mixing said second electrical signal provided by said signal means and said electrical return signal to provide a beat signal having a beat frequency; and

means coupled to receive said beat signal for determining the presence of said identifier means when a predetermined beat frequency is received for at least a predetermined duration after the termination of said transmitted electromagnetic signal and providing a signal indicative thereof.

15. An apparatus as set forth in claim 14 further including means to secure said identifier means to a child restraining seat.

16. An apparatus as set forth in claim 14 further including a band-pass filter for filtering said electrical return signal from said antenna means.

17. An apparatus as set forth in claim 14 further including a band-pass filter for filtering said beat signal from said combiner means.

18. An apparatus as set forth in claim 17, wherein said band-pass filter has a center pass frequency approximately equal to the difference between said first and second frequencies.

19. An apparatus as set forth in claim 14, wherein said means coupled to receive said beat signal includes a comparator for receiving said beat signal and providing a pulsing signal having a frequency equal to said beat frequency.

20. An apparatus as set forth in claim 19, wherein said means coupled to receive said beat signal further includes processor means for receiving said pulsing signal and determining the presence of said identifier means by counting the number of pulses.