Bi-mode millimeter wave mixer
AssigneeHughes Aircraft Company
InventorsJoseph M. Baird, Paul M. Schwartz
Life of this patent
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Abstract
The specification describes a means and method for mixing millimeter wave RF energy of one chosen transverse electric (TE) waveguide mode with a local oscillator signal of another chosen TE waveguide mode, and such mixing is accomplished by applying those RF and local oscillator signals to a pair of reverse poled and parallel connected mixer diodes. These mixer diodes are connected at a chosen location within a rectangular waveguide and between top and bottom walls thereof and are symmetrically spaced across the width of the waveguide with respect to the center or a/2 location in the guide, with "a" being the width dimension in the guide. An IF output signal is derived at a common output node for the mixer diodes.
Claims15
A balanced waveguide mixer structure for generating an intermediate frequency (IF) output signal in response to the mixing of local oscillator and incoming RF input signals, comprising:
- (a) means including a rectangular waveguide for propagating RF and local oscillator signals to a chosen location within said waveguide and in preselected modes of waveguide propagation, and
- (b) means including a pair of parallel-connected and reverse-poled mixer diodes connected at said chosen location between top and bottom walls of said waveguide, said diodes symetrically spaced along the width dimension of said waveguide with respect to the one-half width location in said waveguide and further positioned at predetermined width locations along said width dimension of said waveguide for generating said IF signals at a circuit node common to both of said diodes.
A method for mixing RF input and local oscillator signals to obtain an intermediate frequency (IF) output signal, including:
- (a) propagating RF input and local oscillator signals having preselected waveguide modes to a chosen location in a rectangular waveguide,
- (b) providing a pair of parallel-connected and reverse-poled mixer diodes at said chosen location and symmetrically spaced along the width dimension of said waveguide with respect to the one-half width location in said waveguide and
- (c) positioning said diodes at predetermined width locations along said width dimension of said waveguide for generating an intermediate frequency output signal proportional to the difference currents flowing in said mixer diodes.
A balanced mixer for generating an intermediate frequency output signal in response to the mixing of local oscillator and incoming RF signals, and with an optimized mixer conversion efficiency comprising:
- (a) a rectangular waveguide of a predetermined width, a, corresponding to wave propagation frequencies in the range of between two and three times the cut-off frequency of the TE.sub.10 mode of wave propagation and a predetermined height, b, such that the ratio of b/a precludes propagation therein of the TE.sub.01 waveguide mode,
- (b) a first mixer diode connected between opposing walls of said rectangular waveguide and at a location approximately 1/4 the total width dimension, a, thereof,
- (c) a second mixer diode connected between said opposing walls of said rectangular waveguide and located at a distance of approximately 3/4 of the total width dimension, a, thereof, said diodes being connected in parallel with reverse polarities,
- (d) means coupled to said rectangular waveguide for applying a local oscillator signal of the TE.sub.20 mode of propagation to said first and second mixer diodes,
- (e) means coupled to said rectangular waveguide for applying an input RF signal of the TE.sub.10 propagation mode to said first and second mixer diodes, and
- (f) means including a circuit node common to said first and second mixer diodes for conducting an intermediate frequency output signal therefrom as a result of differential currents in said first and second mixer diodes.
A method for mixing millimeter wave RF energy out to 300 GHz or higher with a local oscillator signal to thereby generate an IF output signal in a rectangular waveguide including a pair of oppositely-poled parallel connected mixer diodes therein, comprising:
- (a) selecting a rectangular waveguide of a height-to-width aspect ratio corresponding to propagation frequencies in a range of between 2 and 3 times the ratio of the RF input frequency to the cut-off frequency of the TE.sub.10 mode of wave propagation in said waveguide, and precluding propagation therein of all waveguide modes except the TE.sub.10 and TE.sub.20 modes,
- (b) applying the TE.sub.20 propagation mode of local oscillator energy to said diodes, and
- (c) applying the TE.sub.10 propagation mode of RF input energy to said diodes, whereby the superimposition of the transverse electric field vectors of said TE.sub.10 and TE.sub.20 propagation modes at said diodes generate sum and difference currents therein for efficiently producing an output IF signal.
The method defined in claim 13 which includes aligning the two maxima points on the TE.sub.20 field vector pattern with the respective positions of the mixer diodes in said waveguide and then summing the superimposed TE.sub.10 field vectors of RF energy and TE.sub.20 field vectors of local oscillator input energy to provide an optimum of energy addition and subtraction at said diodes, thereby optimizing the IF conversion efficiency at said diodes.
A balanced mixer for generating an intermediate frequency output signal in response to the mixing of local oscillator and incoming RF input signals comprising:
- (a) a waveguide having a pair of parallel-connected and reverse poled mixer diodes connected between top and bottom walls thereof and spaced symmetrically with respect to the one-half width dimension, a/2, thereof, where the width, a, has a value which is related to the RF input signal free space wavelength, .lambda., and to the local oscillator signal free space wavelength, .lambda..sub.LO, by the expression ##EQU2## and by the expression ##EQU3## respectively.
Dependencies are inferred from the claim text.