Browse Prior Art Database

DUAL BAND RECEIVER

IP.com Disclosure Number: IPCOM000008960D
Original Publication Date: 1999-Jan-01
Included in the Prior Art Database: 2002-Jul-26
Document File: 2 page(s) / 83K

Publishing Venue

Motorola

Related People

Wong Sie Hui: AUTHOR [+3]

Abstract

Presently, Greatwall and Pagoda pagers have auto-roaming channels restricted to the same 280Mhz or 322Mhz bands.

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MO-LA Technical Developments

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DUAL BAND RECEIVER

by Wong Sie Hui, Tan Soon Kuan and Thay Choon Teck

BACKGROUND

  Presently, Greatwall and Pagoda pagers have auto-roaming channels restricted to the same 280Mhz or 322Mhz bands.

  Proposed in this article is a dual band receiver that allows roaming in both 280Mhz and 322Mhz bands. Furthermore, this concept can be extended to cover the VHF band as well. Such a dual band receiver would also make manufacturing easier as the same receiver can be used for both frequency bands. This is different from the usual practice of having two separate receivers corresponding to the two bands.

SOLUTION

  Figure 1 shows a block diagram of a conven- tional dual-conversion receiver that employs a fre- quency synthesizer for its first local oscillator. Circuitries from the first mixer down to the backend stage are common regardless of the frequency of operation.

  Consider an operating frequency range of 278 to 286Mhz and 322 to 328Mhz for the 280Mhz and 322Mhz bands respectively. The usual method of using low-side injection for the 1st LO will result in a VCO frequency range of 130.05 to 134.05Mhz and 152.05 to 155.05Mhz for the 280Mhz and 322Mhz bands respectively, assuming a 1st IF of
17.9Mhz. This spread of 25Mhz (130.05Mhz to

155.05Mhz) would be difficult to achieve for a syn- thesizer that operates on a 2-volt supply. To get around this problem, we propose using high-side injection for the 280Mhz band and low-side injec- tion for the 322Mhz band. This would translate...