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Browse Prior Art Database

Channel spacing recognition code

IP.com Disclosure Number: IPCOM000129194D
Original Publication Date: 2005-Sep-30
Included in the Prior Art Database: 2005-Sep-30
Document File: 5 page(s) / 333K

Publishing Venue

Motorola

Related People

Hooi Woi Jie: AUTHOR [+2]

Abstract

Large frequency spectrum has been allocated to radios with different frequency bands, such as VHF, UHF range 1 and range 2. With the increasing need of wireless communication, frequency bandwidth has become one of the limitations. Going forward, there might be a need to reduce the channel spacing to be smaller than 12.5 kHz to ensure efficient use of frequency bandwidth. By introducing channel spacing recognition code, each channel spacing used will be represented by a unique code which will be modulated with RF carrier during transmission. With this mechanism, radios with different channel spacing settings can communicate well with other radios perfectly, without the worry of having distortion at recovered audio signal.

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Channel spacing recognition code

Authors

Hooi Woi Jie, Chua Chong Keat

Abstract

Large frequency spectrum has been allocated to radios with different frequency bands, such as VHF, UHF range 1 and range 2. With the increasing need of wireless communication, frequency bandwidth has become one of the limitations. Going forward, there might be a need to reduce the channel spacing to be smaller than 12.5 kHz to ensure efficient use of frequency bandwidth.

By introducing channel spacing recognition code, each channel spacing used will be represented by a unique code which will be modulated with RF carrier during transmission. With this mechanism, radios with different channel spacing settings can communicate well with other radios perfectly, without the worry of having distortion at recovered audio signal.

Disclosed are 2 methods to recognize channel spacing used by modulating special codes and constant tone deviation during transmission.

Large frequency spectrum has been allocated to radios with different frequency bands, such as VHF, UHF range 1 and range 2. With the increasing need of wireless communication, frequency bandwidth has become one of the limitations. Going forward, there might be a need to reduce the channel spacing to be smaller than 12.5 kHz to ensure efficient use of frequency bandwidth. These are 2 disclosed methods in this paper:

A)                 Channel Spacing Recognition based on special codes

Figure 1: Transmission of Channel Spacing Recognition based on special codes.

 

Figure 1 is showing transmission of Channel Spacing Recognition based on special codes. Each channel spacing (for example 12.5kHz channel spacing or 25kHz channel spacing) will be represented by a unique code. For instance, 12.5 kHz channel spacing will carry the code ‘AB’ while 25 kHz channel spacing will be represented by code ‘CD’. When transmission occurs, the codes associated with specific channel spacing will be modulated and transmitted with RF (Radio Frequency) carrier. Receiver will decode the transmitted signal to find out what channel spacing is the other radio using. After this, the microprocessor of the receiving radio will be programmed to the channel spacing which is similar to transmitted radio.  The signal will be demodulated according to the transmitted channel spacing. This method does not require additional circuitry to implement but needs extra software codes to support the feature.

                   Figure 2: Flowchart on Channel Spacing Recognition based on special codes.

Referring to Figure 2 the flowchart illustrated is performs the following:

I)                     Tx radio:             

At process chart 1: During Transmission, ASFIC (Audio/Signaling Filter Integrated  Circuit) in Tx (Transmitted) radio will generate the unique code (“AB” for 12.5kHz channel spacing or “CB” for 25kHz channel spacing) and then to be frequency modulated onto the frequency carrier.

II)                   Rx Radio:

At process chart 2: While Rx (Received) rad...