Baseband direct sequence spread spectrum transceiver

• US 6,982,945 B1
• Filed: 01/26/2001
• Issued: 01/03/2006
• Est. Priority Date: 01/26/2001
• Status: Expired due to Fees

• Current Assignee: Google Inc. (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Gossett, Carroll Philip
• Primary Examiner(s): NGUYEN, HANH N
• Application Number:
  US09/772,110
• Time in Patent Office: 1,803 Days
• Field of Search: 370/203, 370/204, 370/208, 370/209, 370/335, 370/342, 370/441, 370/276, 370/290, 370/296, 370/320, 370/294, 375/130, 375/135, 375/136, 375/140, 375/142, 375/144, 375/150, 375/219, 375/315, 375/141, 375/146, 343/702
• US Class Current: 370/208
• CPC Class Codes: H04B 1/707 using direct sequence modulation

Abstract

A baseband direct sequence spread spectrum CDMA transceiver. The data signal is modulated with a Hadamard function having pseudorandomly scrambled rows. This data signal is then broadcast baseband, absent a carrier, by a relatively short, mismatched antenna. The baseband signal is spread out across the DC to 30 MHz spectrum. A low noise, high gainbandwidth product amplifier boosts the baseband RF signal. A correlator/servo system is used to actively cancel the transmit signal from the received signal. Consequently, the same antenna can be used to receive incoming baseband RF signals as well as transmit baseband RF signals, thereby providing full duplex operation.

Claims

1. A method for transmiting an RF signal comprising:

modulating a data signal with an orthogonal pseudo random code;

transmitting the data signal as a baseband direct sequence spread spectrum CDMA (Code Division Multiplex Access), wherein no additional modulation is performed on the data signal before transmission and the baseband direct sequence spread spectrum data signal is spread across DC to 30 MHz;

driving a mismatched antenna; and

actively servoing a transmit signal to cancel the transmit signal from a receive signal.

2. The method of claim 1 further comprising the step of using a same antenna to transmit and receive baseband signals in a full duplex mode of operation.

3. A method for transmitting an RF signal, comprising:

modulating a data signal in a single step with a Hadamard function having pseudorandomly scrambled rows;

driving a mismatched antenna; and

transmitting the data signal as baseband direct sequence spread spectrum CDMA (Code Division Multiplex Access) across DC to 30 MHz.

4. The method of claim 3 further comprising the step of converting a digital data signal into an equivalent analog signal which is directly transmitted by an antenna over the air, wherein the antenna is at least ten times shorter than the wavelength of the signal being transmitted.

5. The method of claim 3 further comprising the step of actively servoing a transmit signal to cancel the transmit signal from a receive signal.

6. The method of claim 3 further comprising the step of using a same antenna to transmit and receive baseband signals in a code division duplex mode of operation.

7. The method of claim 3 further comprising the step of transmitting baseband signals for peer-to-peer cellular communications.

8. A baseband direct sequence spread spectrum CDMA transceiver comprising:

a transmitter which modulates data by a Hadamard function having pseudorandomly shuffled rows or columns, wherein the data is only modulated in one single modulation step with no additional modulation before transmission; and

an antenna shorter than transmit signal wavelength for broadcasting baseband signals across DC to 30 MHz spectrum, wherein the antenna is driven mismatched.

9. The baseband direct sequence spread spectrum CDMA transceiver of claim 8 wherein the antenna is at least ten times shorter than the transmit signal wavelength.

10. The baseband direct sequence spread spectrum CDMA transceiver of claim 8 comprising a code division duplex mode of operation.

11. The baseband direct sequence spread spectrum CDMA transceiver of claim 8 further comprising a low noise high gain bandwidth amplifier for boosting a received baseband signal.

12. The baseband direct sequence spread spectrum CDMA transceiver of claim 8 further comprising a lookup table utilized to modulate and demodulate the baseband signal and a pointer for pointing to Walsh/Hadamard codes corresponding to said Hadamard function.

13. The baseband direct sequence spread spectrum CDMA transceiver of claim 8 further comprising an active servo system for canceling transmit signals from receive signals.