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AM FILTER AS WSSB FILTER WITH NEW "IF" EQUIVALENT FREQUENCY

IP.com Disclosure Number: IPCOM000006087D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2001-Dec-03
Document File: 4 page(s) / 117K

Publishing Venue

Motorola

Related People

Moshe Ben-Ayun: AUTHOR [+3]

Abstract

As is shown in AM Mode, the "IF" bandwidth required for audio signal detection is 2 x audio band- Most modern radios consist of dual conversion width. receiver, including two "IF" (Intermediate Frequency) stages. The first "IF" at high frequency is in order to In SSB Mode, the "IF" bandwidth required is the prevent image spurious. The second "IF" at low same as the audio bandwidth. frequency uses narrow band crystal filter providing the required selectivity. Let us assume audio bandwidth of 2.7kHz.

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MOTOROLA INC. Technical Developments Volume 12 April 1991

AM FILTER AS WSSB FILTER WITH NEW "IF" EQUIVALENT FREQUENCY

by Moshe Ben-Ayun, Yehuda Edry and Tamar lscovici

1) GENERAL As is shown in AM Mode, the "IF" bandwidth required for audio signal detection is 2 x audio band- Most modern radios consist of dual conversion width.
receiver, including two "IF" (Intermediate Frequency)
stages. The first "IF" at high frequency is in order to In SSB Mode, the "IF" bandwidth required is the prevent image spurious. The second "IF" at low same as the audio bandwidth.
frequency uses narrow band crystal filter providing the
required selectivity. Let us assume audio bandwidth of 2.7kHz.

The complete receive path realization block AM Mode - "IF" bandwidth is - 2 x 2.7kHz = diagram is described in Figure 1. 5.4kHz

  The receiver operates with several modes of operation: SSB (Single Side Band), NSSB (Narrow Band SSB), WSSB (Wide Band SSB) and AM (Amplitude Modulation). Each mode has a dedicated crystal filter.

  In the new method, which is described here, we use the AM filter for wide band SSB mode with new "IF" equivalent frequency.

2) AM AND WSSB MODES - FREQUENCY SPECTRUM ANALYSIS

  The most common way to realize the SSB Modulation is by filtering technique. A filtering technique, to form a single side band signal illustrated in Figure 2, is justified by the fact that all the information necessary to reconstruct Y(T) is completely contained in positive (or negative) portion of G(W).

The difference between the frequency spectrum at the second "IF" stage is shown in Figure 3.

SSB Mode - "IF" bandwidth is - 2.7kHz

3) DESCRIPTION OF THE INVENTION

As demonstrated before, the "IF" filter bandwidth required for AM Mode is 2 x SW, refer to SSB Mode.

  In the new method, we use the AM crystal filter for new mode of operation - wideband SSB.
(2...