US 4,811,425 AGranted

Apparatus for reducing the effects of local oscillator leakage in mixers employed in zero IF receivers

AssigneeITT Avionics, A Division of ITT Corporation

InventorIrwin Feerst

Life of this patent

Estimating the term…

Loading patent…

Abstract

Apparatus for reducing the effects of mixer leakage in a zero IF transmission system includes first and second mixers having relatively equal leakage amounts from an oscillator port to an input port, with the input port of said first mixer adapted to receive a zero IF receiver input signal and with the output port of said first mixer capacitively coupled to the input port of the second mixer. The oscillator ports of the first and second mixers are coupled to a local oscillator output, with the output ports of said first and second mixers coupled respectively to an adder and subtractor circuit to provide respectively a DC signal indicative of the leakage and an output signal indicative of the magnitude of said input signal as effected by leakage to thereby enable the determination of said input signal after mixing.

Claims12

Dependent claims

Apparatus for reducing the effects of local oscillator leakage in mixing circuits, comprising:

first and second mixing means having an input port, a local oscillator port and an output port and each undesirably exhibiting a leakage from said local oscillator port to said input port whereby a given level of local oscillator signal couples to said input port,
a local oscillator having an output coupled to said local oscillator ports of said first and second mixing means,
means coupled to said input port of said first mixing means for applying a modulated input signal thereto of a given frequency,
means for capacitively coupling said input port of said second mixing means to said output port of said first mixing means,
adder means having a first input coupled to the output port of said first mixing means and a second input coupled to the output port of said second mixing means to provide at an output a DC signal indicative of the leakage between said input and oscillator ports,
subtractor means having a first input coupled to the output port of said first mixing means and a second input coupled to the output port of said second mixing means to provide at an output a signal indicative of said input signal as mixed with said local oscillator frequency and as further effected by said leakage whereby said signals from said subtractor means and from said adder means may be combined to produce a signal which is truly indicative of said input signal irrespective of said leakage signal.

3 more elements

Apparatus for reducing the effects of local oscillator leakage in a mixer circuit whereby said leakage undesirably occurs between an oscillator port of said mixer and a signal input port to cause said mixer to undesirably provide an output signal including components due to said leakage signal wherein a zero IF system said signal at said input port and said local oscillator signal are relatively of the same frequency to cause an undesired DC component to appear at said mixer output due to said leakage signal comprising:

first and second mixers each having an input port, a local oscillator port and an output port, with each mixer exhibiting a given leakage between said local oscillator port and said input port,
means for applying an input signal to said input port of said first mixer,
means for applying a local oscillator signal to said local oscillator ports of said first and second mixers,
means for coupling the output of said first mixer to the signal input of said second mixer,
means coupled to the outputs of said first and second mixers for respectively adding and subtracting said outputs to provide output signals from each of the adding and subtracting operations which may be combined to produce a signal which is indicative of the input signal and relatively independent of the magnitude of said leakage signal.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/001,712Filed 9 Jan 1987
Granted: 7 Mar 1989
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

H03D 7/165
Multiple-frequency-changing: at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature
H04B 15/06
The interference being caused by substantially sinusoidal oscillations, e.g. in a receiver or in a tape-recorder: by local oscillators of receivers
H03B 2202/08
Aspects of oscillators relating to reduction of undesired oscillations: reduction of undesired oscillations originated from the oscillator in…
H03B 2202/088
Reduction of undesired oscillations originated from the oscillator in circuit elements external to the oscillator by means associated with the…:…