Demodulator having an infinite-duration impulse response filter with dynamic coeffiecient scaling

• US 6,243,410 B1
• Filed: 06/03/1998
• Issued: 06/05/2001
• Est. Priority Date: 03/29/1996
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Carney, Michael John, Becker, Christopher John, LaRosa, Christopher Peter
• Primary Examiner(s): Vo, Don N.
• Application Number:
  US09/089,992
• Time in Patent Office: 1,098 Days
• Field of Search: 375/130, 375/147, 375/150, 375/229, 375/232, 375/233, 375/350, 375/148
• US Class Current: 375/148
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04L 25/0214 of a single coefficient
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity
• CPC Class Codes: H04W 52/60 using different transmission rates for TPC commands

Abstract

By time-sharing demodulator hardware between a primary data path (165), a power control data path (161), and a received signal strength indicator (RSSI) path (163), an entire power control data path (161) can be implemented in a demodulator (140) of a spread spectrum subscriber unit receiver with a low increase in gate count. The primary data path (165) and the power control data path (161) time-share a complex conjugate generator (270), a complex multiplier (280), and a real component extractor (290). Due to timing requirements, though, the channel estimation filter (240) of the primary data path cannot be time-shared with the power control data path. Instead, dynamic coefficient scaling is added to an infinite-duration impulse response (IIR) filter in the RSSI path (163) so that the IIR filter (250) with dynamic coefficient scaling can be time-shared between the RSSI path (163) and the power control data path (161).

Claims

1. A demodulator for producing a received signal strength indicator (RSSI) value signal and a power control data signal comprising:

an infinite-duration impulse response (IIR) filter with dynamic coefficient scaling having;

an adder having an adder output;

a coefficient selection block, coupled to the adder output, for selectively multiplying a signal at the adder output by either a first coefficient set or a second coefficient set; and

a delay block, coupled to the coefficient selection block, for providing a negative feedback signal from the coefficient selection block to the adder.

2. A demodulator having an IIR filter with dynamic coefficient scaling according to claim 1 wherein the coefficient selection block comprises:

a scaler block, coupled to the adder output, having a scaler block output;

a switch, coupled to select either the adder output or the scaler block output, having a switch output; and

a bit shift-and-add block, coupled to the switch output.

3. A demodulator having an IIR filter with dynamic coefficient scaling according to claim 2 wherein the switch is a multiplexer.

4. A demodulator having an IIR filter with dynamic coefficient scaling according to claim 1 wherein the coefficient selection block is controlled by a selection signal.

5. A demodulator having an infinite-duration impulse response (IIR) filter with dynamic coefficient scaling comprising:

an adder;

a delay block, coupled to the adder, having a delay block output; and

a coefficient selection block, coupled to the delay block output, for selectively multiplying a signal from the delay block output by either a first coefficient set or a second coefficient set and providing a negative feedback signal to the adder.

6. A demodulator having an IIR filter with dynamic coefficient scaling according to claim 5 wherein the coefficient selection block comprises:

a scaler block, coupled to the delay block output, having a scaler block output;

a switch, coupled to select either the delay block output or the scaler block output, having a switch output; and

a bit shift-and-add block, coupled to the switch output.

7. A demodulator having an IIR filter with dynamic coefficient scaling according to claim 6 wherein the switch is a multiplexer.

8. A demodulator having an IIR filter with dynamic coefficient scaling according to claim 5 wherein the coefficient selection block is controlled by a selection signal.