Approximating signal power and noise power in a system

• US 6,975,693 B1
• Filed: 04/25/2000
• Issued: 12/13/2005
• Est. Priority Date: 03/11/1998
• Status: Expired due to Term

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Hillery, William J., Sattiraju, V. Rao
• Primary Examiner(s): Bayard, Emmanuel
• Application Number:
  US09/558,302
• Time in Patent Office: 2,058 Days
• Field of Search: 375/340, 375/316, 375/345, 375/324, 375/329, 375/298, 375/281, 375/330, 375/331, 375/350, 375/346, 375/349, 455/63, 455/203, 455/204, 455/276.1, 455/283, 455/295, 455/304, 455/303, 329/304, 329/345, 329/353, 708/445, 708/200, 708/201
• US Class Current: 375/350
• CPC Class Codes: G06F 7/552 Powers or roots , e.g. Pythagorean sums

Abstract

An electronic system with power approximation for circuit savings. Power approximation is provided by means for generating an absolute value of a real part of a signal, means for generating an absolute value of an imaginary part of the signal, means for generating a sum of the absolute values, and means for performing an averaging function on the sum such that a result of the averaging function provides an approximate power which indicates an actual power of the signal. The approximate power enables a determination of actual signal-to-noise ratio in the electronic system and a determination of a variety of other signal-to-noise determinations without the use of multipliers.

Claims

1. A demodulator having a power approximation circuit coupled to receive a real and imaginary component of a complex signal, the power approximation circuit generating an approximate power value which indicates an actual power value for the complex signal by combining absolute values of the real and imaginary components and then applying an expectation function to the combined absolute values.

2. The demodulator of claim 1, wherein the approximate power value is used to detect at least one signal-to-noise ratio threshold in the demodulator.

3. The demodulator of claim 1, wherein the approximate power value is provided to an external processor which includes a lookup table that maps the approximate power value to an actual signal-to-noise ratio value.

4. The demodulator of claim 1, further comprising a lookup table which maps the approximate power value to an actual signal-to-noise ratio value.

5. The demodulator of claim 4, further comprising:

blind adaptive equalizer that generates a filter output signal in response to an information signal according to a transfer function which adapts in response to a selected error indication;

circuitry for providing the selected error indication by switching among a set of differing error indications in response to a determination of a relationship between the actual signal-to-noise ratio value and a threshold signal-to-noise ratio.