Self-calibrating signal strength detector

• US 4,619,002 A
• Filed: 07/02/1984
• Issued: 10/21/1986
• Est. Priority Date: 07/02/1984
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Thro, Stuart W.
• Primary Examiner(s): Bookbinder, Marc E.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/627,270
• Time in Patent Office: 841 Days
• Field of Search: 455/50, 455/52, 455/54, 455/56, 455/254, 455/226, 455/242, 455/246, 455/200, 455/239, 455/219, 455/234, 375/76, 375/98 B, 307/362, 307/358, 324/130
• US Class Current: 455/226.2
• CPC Class Codes: H03G 3/341 Muting when no signals or only weak signals are present H03G3/344, H03G3/345 take precedence
• CPC Class Codes: H04B 7/0851 using training sequences or error signal minimizing error signal H04B7/0854

Abstract

A self-calibrating signal strength detector is described. The present invention utilizes a relatively narrow dynamic range receiver sensitivity threshold indicator circuit to calibrate the output signal of a relatively wide dynamic range signal strength detector. In accordance with the present invention, a processing device monitors the outputs of the signal strength detector and receiver sensitivity threshold indicator circuit simultaneously, and determines a correction factor to be applied to the output of the signal strength detector when the receiver sensitivity threshold indicator circuit indicates that a received signal is at the receiver sensitivity threshold.

Claims

1. A self-calibrating signal strength detector for use in an RF receiver having an output, comprising:

(a) an RF signal strength detector coupled to the output of said receiver having a relatively wide dynamic range and an adjustable output signal;

(b) a receiver sentivity threshold indicator circuit coupled to the output of said receiver circuit having a relatively narrow dynamic range, said receiver sensitivity threshold indicating circuit providing an output signal indicating when a received signal is at the receiver sensitivity threshold; and

(c) processing means coupled to each of said signal strength detector and said signal sensitivity threshold indicator circuit for monitoring the outputs thereof and adjusting the output signal of said signal strength detector means to a predetermined value when said signal sensitivity threshold indicator indicates a received signal is at the received threshold.

2. The self-calibrating signal strength detector of claim 1 wherein said receiver sensitivity threshold indicator is a squelch type circuit which may have a two-state output signal.

3. The self-calibrating signal strength detector of claim 1 wherein said receiver sensitivity indicator circuit is a bit noise flag generator.

4. The self-calibrating signal strength detector of claim 1 wherein said processing device is a microcomputer.

5. An adaptive self-calibrating signal strength detector for indicating the signal level of a received RF signal in a receiver comprising:

(a) a receiver having RF, IF, and detector stages capable of receiving a transmitted data signal and producing a data signal at baseband;

(b) a signal strength detector coupled to the IF stage of said receiver having a signal strength detector output signal related to the signal strength of said received data signal;

(c) a receiver sensitivity threshold indicator having a digital output indicating when said received signal is at said receiver'"'"'s signal sensitivity threshold; and

(d) processing means coupled to said signal strength detector output signal and said signal strength threshold indicator output for determining a correction factor to be applied to said signal strength detector output signal based on the output of said receiver sensitivity threshold indicator.

6. The adaptive signal strength detector of claim 5 wherein sid receiver sensitivity threshold indicator is a squelch type circuit which may have a two-state output signal.

7. The adaptive signal strength detector of claim 5 wherein said receiver sensivity indicator is a bit noise flag generator.

8. The adaptive signal strength detector of claim 5 wherein said processing device is a microcomputer.

9. A method for adaptively correcting the output of a signal strength indicator circuit in a RF receiver, said method comprising the steps of:

(a) receiving an RF signal;

(b) measuring the received RF signal strength with a relatively wide dynamic range signal strength detector having an adjustable output signal;

(c) measuring the received RF signal level with a relatively narrow dynamic range signal sensitivity indicator which provides an output indicating whether said received RF signal is at or near the receiver'"'"'s sensitivity threshold; and

(d) adjusting the output level of said wide dynamic range signal strength detector to a predetermined value when said narrow dynamic range detector indicates said received signal is at or near the receiver'"'"'s signal strength threshold.

10. A method of adjusting the output signal of a relatively wide dynamic range signal strength detector in an RF receiver, said method comprising the steps of:

(a) receiving an RF data signal comprising a plurality of individual data bits;

(b) generating a digitized signal which is related to the signal strength of said received RF signal;

(c) generating a noise flag bit for each data bit wherein a noise flag indicates whether a particular data bit is good or bad;

(d) accumulating noise flag bits and data bits over a predetermined period;

(e) adding the number of noise flags accumulated during a particular period to determine the total number of noise flags for that period;

(f) averaging said digitized signal over a predetermined period said averaged digitized signal comprising the unadjusted signal strength level;

(g) determining whether the number of accumulated noise flag bits are within a predetermined range indicating that said received RF signal is at the receiver sensitivity threshold;

(h) determining a signal strength detector output level correction factor if the unadjusted signal strength level does not indicate an average signal strength level within a predefined range.