Baseband demodulator for polar or rectangular modulated signal in a cordless spread spectrum telephone

• US 5,828,692 A
• Filed: 12/06/1995
• Issued: 10/27/1998
• Est. Priority Date: 12/06/1995
• Status: Expired due to Term

• Current Assignee: Intellectual Ventures I LLC (Intellectual Ventures LLC)
• Original Assignee: Rockwell International Corporation
• Inventors: Walley, John S.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): GLUCK, JEFFREY WILLIAM
• Application Number:
  US08/568,045
• Time in Patent Office: 1,056 Days
• Field of Search: 375/316, 375/322, 375/324, 375/345, 375/200, 375/329, 375/330, 455/144, 455/234.1, 455/239.1, 455/245.1
• US Class Current: 375/130
• CPC Class Codes: H03G 3/3052 in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver H03G3/32, H03G3/34 take precedence
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04L 27/2273 associated with quadrature demodulation, e.g. Costas loop

Abstract

A cordless telephone system connectable to the public switched telephone network having a base station and one or more handsets communicating with the base station by an RF link utilizing a DBPSK I and Q demodulator with a digital AGC loop. When R ∠θ is being received instead of I and Q data, the phase information (∠θ) is connected to the I input of the DBPSK demodulator. The amplitude information (R) and the output of the digital AGC logic are applied as differential inputs to the Q input of the DBPSK demodulator. The I input to the AGC logic is set to zero. The Q input to the AGC logic is supplied with the R data. The AGC servo loop with the differential Q inputs to the DBPSK demodulator creates a high resolution A/D converter for R. The theta information is used to demodulate the incoming bipolar data, which may be either MSK or FSK, if a limiter-discriminator or other FM demodulator is used.

Claims

1. In a spread spectrum communication link, a baseband demodulator connected to receive in-phase and quadrature baseband signals and amplitude and phase angle baseband signals, the baseband demodulator comprising:

a digital AGC logic circuit having an output connected to a DAC;

means for connecting the output of the DAC to a differential Q input of the baseband demodulator when amplitude and phase angle signals are being received;

means for connecting the amplitude components of a received signal to a differential Q input of the baseband demodulator; and

means for connecting the phase angle components of the received signal to the differential I input of a baseband demodulator.

2. The baseband demodulator of claim 1 further comprising:

means for connecting the amplitude components of the received signal to a Q input of the AGC logic circuit.

3. The baseband demodulator of claim 2 further comprising:

means for connecting the output of the DAC to a feedback loop for a radio frequency demodulator when I and Q signals are being received.

4. The baseband demodulator of claim 3 further comprising:

means for connecting received I channel signals to said differential I input of the baseband demodulator; and

means for connecting received Q channel signals to said differential Q input of the baseband demodulator.

5. The baseband demodulator of claim 4 further comprising:

means for connecting received I channel signals to an I input of the AGC logic circuit; and

means for connecting received Q channel signals to the Q input of the AGC logic circuit.

6. In a cordless telephone having a base station connectable to a switched telephone network and at least one handset, said base station and handset communicating over a radio frequency link utilizing spread spectrum modulation, a baseband demodulator in said handset and in said base station, each connected to receive RF demodulated signals in either polar or rectangular form, received over the radio frequency link, the baseband demodulator comprising:

a digital AGC logic circuit having an output connected to a DAC;

means for connecting the output of the DAC to a differential Q input of the baseband demodulator when amplitude and phase angle signals are being received;

means for connecting the amplitude components of the received signal to a differential Q input of the baseband demodulator; and

means for connecting the phase angle components of the received signal to a differential I input of the baseband demodulator.

7. The cordless telephone of claim 6 further comprising:

means for connecting the amplitude components of the received signal to the Q input of a AGC logic circuit.

8. The cordless telephone of claim 7 further comprising:

means for connecting the output of the DAC to a feedback loop for a radio frequency demodulator when I and Q signals are being received.

9. The cordless telephone of claim 8 further comprising:

means for connecting received I channel signals to said differential I input of the baseband demodulator; and

means for connecting received Q channel signals to said differential Q input of the baseband demodulator.

10. The cordless telephone of claim 9 further comprising:

means for connecting received I channel signals to an I input of the AGC logic circuit; and

means for connecting received Q channel signals to the Q input of the AGC logic circuit.