EP0470089A1 - Receiver threshold extension - Google Patents
Receiver threshold extensionInfo
- Publication number
- EP0470089A1 EP0470089A1 EP90905988A EP90905988A EP0470089A1 EP 0470089 A1 EP0470089 A1 EP 0470089A1 EP 90905988 A EP90905988 A EP 90905988A EP 90905988 A EP90905988 A EP 90905988A EP 0470089 A1 EP0470089 A1 EP 0470089A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- signal
- receiver
- unmodulated
- received
- threshold
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
Definitions
- This invention relates generally to radio frequency receivers and more particularly to receivers with sensitivity improvement.
- One measure of a receiver's performance is its ability to reject noise while providing a clear desired signal. Typically, this performance is rated by a signal-to-noise ratio. The higher the signal-to-noise ratio, the better the sensitivity (and performance) of the receiver.
- an information signal is received and examined to determine its signal strength.
- the signal strength is at least equal to a threshold, an unmodulated signal is added to the received signal to improve 0 the sensitivity of the receiver.
- FIG. 1 is a block diagram of a receiver in accordance with the present invention. 5
- a receiver 10 having an information signal 11 being received by an antenna 12.
- the received information signal (and received noise) is filtered 0 (bandlimited) via a preselector 14 before being mixed (mixer 16) with an injection signal from an oscillator 18.
- the oscillator 18 is programmed (34) to provide a suitable injection signal by a controller 32 so that a desired information signal can be received.
- the mixer 16 provides an intermediate frequency (IF) signal to an 5 IF amplifier 20 to be amplified prior to being filtered by an IF filter 22.
- the filtered signal is processed by a detector 24 to provide a recovered signal. It will be appreciated that an additional intermediate frequency stage can be added before the mixer 16 along with additional bandpass filters.
- the detected or recovered fj signal is amplified in an optional audio amplifier 26 before being presented via a speaker 28.
- the signal strength of the desired received IF signal is determined and compared to a threshold.
- signal strength detection is accomplished in the IF amplifier 20, which has a receiver signal strength indicator (RSSI) output.
- the IF amplifier 20 comprises an MC 3362 manufactured by Motorola Inc. or its functional equivalent.
- the present invention adds an unmodulated signal to the received IF signal when the received IF signal is below a predetermined threshold (which may be set at the 3dB signal-to- noise ratio). If the RSSI output (30) indicates that the received IF signal is at or below the threshold (set near the noise level), the controller 32 programs (42) the frequency of another oscillator 40 to produce the unmodulated signal. Having its frequency set at the same frequency of the received IF signal, the unmodulated signal is amplified in an amplifier 38 controlled by the controller 32 (via line 36) before being added (summed 39) to the received IF signal at the input to the filter 22.
- a predetermined threshold which may be set at the 3dB signal-to- noise ratio
- the gain of the amplifier 38 is set (36) such that the amplitude of the unmodulated carrier signal is preferably at least 8dB above the threshold (which is set near the noise level). It will be appreciated that the summing node 39 may occur before or after the filter 22.
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Noise Elimination (AREA)
- Circuits Of Receivers In General (AREA)
Abstract
On prévoit un récepteur (10) qui reçoit (12) un signal d'information (11) et qui évalue (20) ledit signal pour déterminer sa valeur lorsque la valeur du signal est au moins égale à un seuil, un signal non modulé (40) est adjoint au signal reçu de manière à améliorer la sensibilité du récepteur.A receiver (10) is provided which receives (12) an information signal (11) and which evaluates (20) said signal to determine its value when the signal value is at least equal to a threshold, an unmodulated signal ( 40) is added to the received signal in order to improve the sensitivity of the receiver.
Description
RECEIVER THRESHOLD EXTENSION
Technics F iς.
This invention relates generally to radio frequency receivers and more particularly to receivers with sensitivity improvement.
Ba ground Art
One measure of a receiver's performance is its ability to reject noise while providing a clear desired signal. Typically, this performance is rated by a signal-to-noise ratio. The higher the signal-to-noise ratio, the better the sensitivity (and performance) of the receiver.
Others skilled in the art have used complicated detector and compensation arrangements that attempt to improve the receiver's sensitivity. However, existing receiver sensitivity improvement techniques (such as "click swallowing") do not function well when the desired information signal has a received amplitude that is near the noise level. This noise barrier resides approximately below a 3dB signal-to-noise ratio, which is often called the noise range. Therefore, a need exists for a simple method to improve the receiver's sensitivity below the noise range.
Summary of the Invention
Accordingly, it is an object of the present invention to improve sensitivity to a receiver when the information signal is near the noise level.
Briefly, according to the invention an information signal is received and examined to determine its signal strength. When the signal strength is at least equal to a threshold, an unmodulated signal is added to the received signal to improve 0 the sensitivity of the receiver.
Brief Description of the Drawings
Figure 1 is a block diagram of a receiver in accordance with the present invention. 5
Detailed Description of the Preferred Embodiment
Referring to Figure 1, a receiver 10 is shown having an information signal 11 being received by an antenna 12. The received information signal (and received noise) is filtered 0 (bandlimited) via a preselector 14 before being mixed (mixer 16) with an injection signal from an oscillator 18. The oscillator 18 is programmed (34) to provide a suitable injection signal by a controller 32 so that a desired information signal can be received. The mixer 16 provides an intermediate frequency (IF) signal to an 5 IF amplifier 20 to be amplified prior to being filtered by an IF filter 22. The filtered signal is processed by a detector 24 to provide a recovered signal. It will be appreciated that an additional intermediate frequency stage can be added before the mixer 16 along with additional bandpass filters. The detected or recovered fj signal is amplified in an optional audio amplifier 26 before being presented via a speaker 28.
According to the present invention, the signal strength of the desired received IF signal (processed at the IF frequency) is
determined and compared to a threshold. Preferably, signal strength detection is accomplished in the IF amplifier 20, which has a receiver signal strength indicator (RSSI) output. Preferably, the IF amplifier 20 comprises an MC 3362 manufactured by Motorola Inc. or its functional equivalent.
The present invention adds an unmodulated signal to the received IF signal when the received IF signal is below a predetermined threshold (which may be set at the 3dB signal-to- noise ratio). If the RSSI output (30) indicates that the received IF signal is at or below the threshold (set near the noise level), the controller 32 programs (42) the frequency of another oscillator 40 to produce the unmodulated signal. Having its frequency set at the same frequency of the received IF signal, the unmodulated signal is amplified in an amplifier 38 controlled by the controller 32 (via line 36) before being added (summed 39) to the received IF signal at the input to the filter 22. The gain of the amplifier 38 is set (36) such that the amplitude of the unmodulated carrier signal is preferably at least 8dB above the threshold (which is set near the noise level). It will be appreciated that the summing node 39 may occur before or after the filter 22.
To compensate for the suppression of the desired signal due to the injection of the unmodulated signal, additional amplification is provided by the audio amplifier 26 by adjusting (44) its gain. The injection of the unmodulated signal suppresses the noise more than the desired signal when the received signal's amplitude resides at a level below the noise threshold. As a result, the recovered signal has a much greater signal-to-noise ratio. Therefore, sensitivity of the receiver increases. What is claimed is:
Claims
1. A method of receiving an information signal, comprising the steps of:
(a) receiving said information signal to provide a received signal;
(b) determining when said received signal has a signal strength at least equal to a threshold; and
(c) adding an unmodulated signal to said received signal when said signal strength is at least equal to said threshold.
2. The method of claim 1 , further comprising the step of controlling a gain of an amplifier stage in response to said step
(b).
3. The method of claim 1 , further comprising the step of detecting said received signal and said unmodulated signal to provide an output signal.
4. The method of claim 3, further comprising the step of amplifying said output signal.
5. The method of claim 1 , further comprising the step of synthesizing a frequency of said unmodulated signal.
6. The method of claim 5, wherein said unmodulated signal has a frequency substantially the same as said information signal's frequency.
7. The method of claim 1 , further comprising the step of adapting an amplitude of said unmodulated signal.
8. The method of claim 7, wherein said amplitude of said unmodulated signal is approximately 8dB above a noise level.
9. A receiver for receiving an information signal, comprising:
means for receiving said information signal to provide a received signal;
means for determining when said received signal has a signal strength at least equal to a threshold; and
means for adding an unmodulated signal to said received signal when said signal strength is at least equal to said threshold.
10. The receiver of claim 9, further comprising means for controlling a gain of an amplifier portion of said receiver as a function of response to said signal strength.
11. The receiver of claim 9, further comprising means for detecting said received signal and said unmodulated signal to provide an output signal.
12. The receiver of claim 11 , further comprising means for amplifying said output signal.
13. The receiver of claim 9, further comprising means for programming a frequency source to provide said unmodulated signal.
14. The receiver of claim 13, wherein said unmodulated signal has a frequency substantially the same as said information signal's frequency.
15. The receiver of claim 9, further comprising means for adapting an amplitude of said unmodulated signal.
16. The receiver of claim 15, wherein said amplitude of said unmodulated signal is approximately 8dB above a noise level.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US34332089A | 1989-04-26 | 1989-04-26 | |
| US343320 | 1994-11-22 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0470089A1 true EP0470089A1 (en) | 1992-02-12 |
| EP0470089A4 EP0470089A4 (en) | 1992-09-16 |
Family
ID=23345613
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP19900905988 Withdrawn EP0470089A4 (en) | 1989-04-26 | 1990-04-09 | Receiver threshold extension |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0470089A4 (en) |
| JP (1) | JPH04504935A (en) |
| WO (1) | WO1990013188A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10024375A1 (en) * | 2000-05-17 | 2001-12-20 | Infineon Technologies Ag | Prevention of parasitic state involves introducing artificial noise signal with noise signal frequency in system processing path, e.g. so signal level exceeds threshold |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS645121A (en) * | 1987-06-27 | 1989-01-10 | Tokyo Gas Co Ltd | Noise suppression device for fm transmitter-receiver |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3588705A (en) * | 1969-11-12 | 1971-06-28 | Nasa | Frequency-modulation demodulator threshold extension device |
| US3983488A (en) * | 1974-06-17 | 1976-09-28 | California Microwave, Inc. | Frequency-modulation demodulator threshold extension device |
| FR2452208A1 (en) * | 1979-03-20 | 1980-10-17 | Thomson Csf | HEAD HEAD WITH SELF-ADAPTIVE DYNAMIC AND RECEIVER COMPRISING SUCH A HEAD |
| JPS56147525A (en) * | 1980-04-18 | 1981-11-16 | Hitachi Ltd | Reception playback system |
| US4672632A (en) * | 1984-02-03 | 1987-06-09 | Motorola, Inc. | Optimized communications system and method employing channel synthesis and phase lock detection |
-
1990
- 1990-04-09 JP JP50573090A patent/JPH04504935A/en active Pending
- 1990-04-09 WO PCT/US1990/001830 patent/WO1990013188A1/en not_active Application Discontinuation
- 1990-04-09 EP EP19900905988 patent/EP0470089A4/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS645121A (en) * | 1987-06-27 | 1989-01-10 | Tokyo Gas Co Ltd | Noise suppression device for fm transmitter-receiver |
Non-Patent Citations (2)
| Title |
|---|
| PATENT ABSTRACTS OF JAPAN vol. 13, no. 176 (E-749)(3524) 25 April 1989 & JP-A-1 005 121 ( TOKYO GAS CO ) * |
| See also references of WO9013188A1 * |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04504935A (en) | 1992-08-27 |
| EP0470089A4 (en) | 1992-09-16 |
| WO1990013188A1 (en) | 1990-11-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
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| 17P | Request for examination filed |
Effective date: 19911014 |
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| A4 | Supplementary search report drawn up and despatched |
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| 17Q | First examination report despatched |
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| STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
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| 18D | Application deemed to be withdrawn |
Effective date: 19970903 |