Method and circuit for filtering disturbances in a radio receiver

• US 5,809,399 A
• Filed: 01/05/1996
• Issued: 09/15/1998
• Est. Priority Date: 01/10/1995
• Status: Expired due to Term

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Inventors: Savolainen, Jorma, Klemetti, Raimo, Tuutijarvi, Mika, Makikallio, Eero
• Primary Examiner(s): Vo, Nguyen
• Assistant Examiner(s): Kincaid, Lester G.
• Application Number:
  US08/583,399
• Time in Patent Office: 984 Days
• Field of Search: 455/254, 455/266, 455/296, 455/306, 455/307, 455/63, 455/67.1, 455/67.3, 455/226.1, 455/226.2, 455/226.3, 375/350
• US Class Current: 455/63.1
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04B 17/391 Modelling the propagation channel

Abstract

The strength of the signal or carrier in one or more transfer channels near the receiving channel of a radio device operating in a radio telephone system is measured, for example, with a MAHO measurement. The measurement result is used to calculate the disturbance caused by the transfer channel to the receiving channel, and, based on the acquired result, the frequency response of a filter included by the receiver is adjusted, for example, by changing the width or slope of the passband.

Claims

1. A method for filtering disturbances in the receiver of a radio device in a radiotelephone system, the system transferring information between the radio device and a base station via a receiving channel assigned by the base station, wherein signal levels in transfer channels assigned by the base station are determined in a receiver of the radio device with a measurement, the method comprising steps of:

providing a receiver of the radio device with an adjustable filter;

measuring a signal strength in a receiving channel of the receiver and a signal strength in at least one neighboring transfer channel having a passband near a passband of the receiving channel;

adjusting a passband characteristic of the adjustable filter in response to a comparison between a difference of the channel signal strengths and a threshold;

determining the bit error rate (BER) for at least some of respective passband characteristics of the adjustable filter obtained in the adjusting step; and

selecting a passband characteristic for the adjustable filter based on measurement of relative signal strength under the condition wherein the difference between signal strengths is less than the threshold, and additionally based on values of the BER under the condition wherein the difference between signal strengths is greater than the threshold.

2. A method according to claim 1, wherein, in the measuring step, the one transfer channel is adjacent to the receiving channel.

3. The method according to claim 1, wherein, in the measuring step, there is a determining of the strength of a receive signal.

4. The method according to claim 1, wherein, in the measuring step there is a determining of the strength of a carrier.

5. A method according to claim 1, further comprising a forming of the control, the forming of the control comprising the steps of:

calculating the average value of the signal level of the receiving channel (RSSI (Tch));

calculating the average value of the signal level of a transfer channel in (RSSI (Nch)) near to the receiving channel;

obtaining the difference between the average value of a signal level of the channel near to the receiving channel (RSSI (Tch)) and the average value of the signal level of the receiving channel (RSSI (Tch));

determining if the difference is greater than a predefined first threshold value (A);

setting the bandwidth of the adjustable filter to a first set value (W1); and

if the difference between the average value of the signal level of the channel near to the receiving channel (RSSI (Nch)) and the average value of the signal level of the receiving channel (RSSI (Tch)) is less than or equal to the predefined first threshold value (A), setting the bandwidth of the adjustable filter to a second set value (W2).

6. A method according to claim 5, wherein said forming of the control additionally comprises the steps of:

if the bandwidth of the adjustable filter equals the first set value (W1), calculating a first average bit error ratio (BER1);

if the bandwidth of the adjustable filter equals the second set value (W2), calculating the second average bit error ratio (BER2) and

if the second average bit error ratio (BER2) is less than the first bit error ratio (BER1), setting the bandwidth of the adjustable filter to the second set value (W2).

7. A method according to claim 1, wherein the filter is an analog filter, the method further comprising a step of adjusting the frequency response of the analog filter by changing a capacitance of the filter.

8. A method according to claim 1, wherein, in said adjusting step. the filter is adjusted in accordance with a characteristic of a base frequency filter or an intermediate frequency filter.

9. The method according to claim 1, wherein, in said step of using measurement results of signal levels of at least one transfer channel, the step is based on a characterization of the radiotelephone system as being based on a time division multiple access (ITDMA) system.

10. The method according to claim 9, wherein. in said measuring step, the measurement is made between receiving (RX) and transmitting (TX) time periods.

11. The method according to Claim 10, wherein, in said measuring stem, the measurement is made during a measurement time period (M1).

12. A circuit for filtering disturbances in the receiver of a radio device in a radio telephone system, wherein information is to be transferred between a radio device and a base station via a receiver channel assigned by the base station, and wherein signal levels in transfer channels assigned by the base station are to be determined in the receiver of the radio device, the circuit comprising:

an adjustable filter having an adjustable frequency response, the radio device including means for adjusting the frequency response of the adjustable filter; and

means for forming a control of the adjustable filter;

wherein said control-forming means is operative in accordance with a procedure comprising steps of;

measuring a signal strength in a receiving channel of the receiver and a signal strength in at least one neighboring transfer channel having a passband near a passband of the receiving channel;

adjusting a passband characteristic of the adjustable filter in response to a comparison between a difference of the channel signal strengths and a threshold;

determining the bit error rate (BER) for at least some of respective passband characteristics of the adjustable filter obtained in the adjusting step; and

selecting a passband characteristic for the adjustable filter based on measurement of relative signal strength under the condition wherein the difference between signal strengths is less than the threshold, and additionally based on values of the BER under the condition wherein the difference between signal strengths is greater than the threshold establishing values of the control based on results of a measurement of the measuring step.

13. The circuit according to claim 12, wherein the means for forming the control comprise at least in part a digital signal processing unit.

14. The circuit according to claim 12, wherein the adjustable filter is at least in part realized in a digital signal processing unit included within the radio device.