Device for rejection of the image signal of a signal converted to an intermediate frequency

• US 5,678,220 A
• Filed: 05/24/1995
• Issued: 10/14/1997
• Est. Priority Date: 06/06/1994
• Status: Expired due to Fees

• Current Assignee: Orange S.A.
• Original Assignee: Orange S.A.
• Inventors: Fournier, Jean Michel
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Nguyen, Lee
• Application Number:
  US08/449,616
• Time in Patent Office: 874 Days
• Field of Search: 455/285, 455/302, 455/303, 455/304, 455/296, 327/355, 327/362
• US Class Current: 455/302
• CPC Class Codes: H03D 7/165 at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature combined with amplitude demodulation H03D1/2245, combined with angle demodulation H03D3/007; N-path filters H03H19/002

Abstract

In a device for rejecting the image signal of a signal converted to a predetermined intermediate frequency, a local oscillator supplies a local signal at a frequency chosen according to the frequency of the signal and the intermediate frequency. A first phase-shifter has two passive phase-shifter cells including resistive and capacitive components and respectively connected to the output of the oscillator to supply two mixer signals in phase quadrature. Two mixers receive an input signal containing a signal and its image signal and a respective mixer signal and supply two intermediate signals at the intermediate frequency. A second phase-shifter comprises two passive phase-shifter cells comprising resistive and capacitive components and respectively connected to the outputs of the two mixers to introduce a further phase quadrature relationship between the two intermediate signals. A summing device connected to the outputs of the two passive phase-shifter cells of the second phase-shifter eliminates the image signal.

Claims

1. Device for rejecting the image signal of a signal converted to a predetermined intermediate frequency, comprising:

a local oscillator supplying a local signal at a frequency chosen according to the frequency of the signal and the intermediate frequency,

a first phase-shifter having two passive phase-shifter cells including resistive and capacitive components and respectively connected to the output of said oscillator to supply two mixer signals in phase quadrature,

two mixers each receiving an input signal containing said signal and said image signal and a respective one of said two mixer signals and supplying two intermediate signals at said intermediate frequency,

a second phase-shifter comprising two passive phase-shifter cells comprising resistive and capacitive components and respectively connected to the outputs of said two mixers to introduce a further phase quadrature relationship between said two intermediate signals, and

image signal eliminator means comprising a summing device connected to the outputs of said two passive phase-shifter cells of said second phase shifter, wherein one of said two passive phase-shifter cells of said two phase-shifters is connected to one of said mixers and includes a resistive-capacitive cell and the other cell connected to said mixer includes a capacitive-resistive cell such that said resistive-capacitive cell is followed by a capacitive-resistive cell, and one of said two passive phase-shifter cells of said two phase-shifters is connected to the other mixer and includes a capacitive-resistive cell and the other cell connected to said mixer includes a resistive-capacitive cell such that said capacitive-resistive cell is followed by a resistive-capacitive cell, and

one input of said summing device is an inverting input and said device is realized in an integrated technology.

2. Device according to claim 1 wherein said eliminator means include a voltage-controlled gain amplifier connected between one input of said summing device and the output of the corresponding passive phase-shifter cell of said second phase-shifter and said gain is controlled by the control voltage of said local oscillator.

3. Device according to claim 2 wherein the gain of said amplifier is controlled by the control voltage of the local oscillator and a selected external voltage.

4. Device for rejecting the image signal of a signal converted to a predetermined intermediate frequency, comprising:

a local oscillator supplying a local signal at a frequency chosen according to the frequency of the signal and the intermediate frequency,

a first phase-shifter having two passive phase-shifter cells including resistive and capacitive components and respectively connected to the output of said oscillator to supply two mixer signals in phase quadrature,

two mixers each receiving an input signal containing said signal and said image signal and a respective one of said two mixer signals and supplying two intermediate signals at said intermediate frequency

a second phase-shifter comprising two passive phase-shifter cells comprising resistive and capacitive components and respectively connected to the outputs of said two mixers to introduce a further phase quadrature relationship between said two intermediate signals, and

image signal eliminator means comprising a summing device connected to the outputs of said two passive phase-shifter cells of said second phase-shifter, wherein said eliminator means include a voltage-controlled gain amplifier connected between one input of said summing device and the output of the corresponding passive phase-shifter cell of said second phase-shifter and said gain is controlled by the control voltage of said local oscillator.

5. Device according to claim 4 wherein the gain of said amplifier is controlled by the control voltage of the local oscillator and a selected external voltage.