Telecommunications – Receiver or analog modulated signal frequency converter – Frequency modifying or conversion
Reexamination Certificate
1999-07-15
2001-08-14
Bost, Dwayne (Department: 2681)
Telecommunications
Receiver or analog modulated signal frequency converter
Frequency modifying or conversion
C455S323000, C455S318000, C455S319000, C455S327000, C333S025000, C333S116000
Reexamination Certificate
active
06275689
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a double-balanced mixer comprising a diode ring which is connected with respective balancing circuit portions for a local oscillator signal and for a high frequency signal and with a capacitively-loaded conductor branch for an intermediate frequency signal.
2. Prior Art
A double-balanced mixer of this type is disclosed in the article by W. Brinlee, K. Varian and M. Pavio, entitled “A Novel Planar Double-Balanced 6-8 GHz MMIC Mixer”, IEEE MTT Symposium Digest, 1994, Session TV1A-2. The diode ring of this double-balanced mixer comprises four diodes connected side-by-side whose connecting lines form an asymmetric figure 8. The respective balancing circuit portions for the RF signal and for the local oscillator signal comprise two conductor lines coupled with each other, between which concentrated capacitances are provided from amplification of the coupling. Its design is made difficult because of the use of concentrated capacitances, especially when exact electrical properties are desired at very high frequencies (30 GHz). The conductor branch for the intermediate frequency signal is purely capacitatively loaded, whereby troublesome resonances can arise in certain cases.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a double-balanced mixer of the above-described type, in which the inputs for the local oscillator signal and for the RF signal are decoupled from each other as much as possible and conversion losses are minimized.
This object and others which will be made more apparent hereinafter are attained in a double-balanced mixer comprising a diode ring, respective balancing circuit portions for a local oscillator signal and for a high frequency signal connected with the diode ring and a capacitively-loaded conductor branch for an intermediate frequency signal connected with the diode ring.
According to the invention each balancing circuit portion has a first coupler comprising two strip lines and a second coupler comprising an interdigital coupler. Each first coupler is connected to a respective first symmetric input of the diode ring and each second coupler is connected to a respective second symmetric input of the diode ring. The first and second couplers of each balancing circuit portion are connected with each other via their gates and two other gates of the first couplers form respective asymmetric signal inputs for the local oscillator signal and the high frequency signal respectively.
It is comparatively easy to design a balancing circuit portion comprising planar conductors so that exact electrical properties are obtained. Also both balancing circuit portions assembled from two coupling devices are suitable for obtaining a high isolation between the local oscillator signal and the high frequency signal.
According to a preferred embodiment of the invention the interdigital coupler comprises at least four strip lines extending beside each other, of which two non-neighboring strip lines are connected with each other at one end. The balancing circuit portions are constructed preferably so that each first coupler has a first gate connected with the first symmetric input of the diode ring, a second gate connected to ground, a third gate forming one input for the local oscillator signal or the high frequency signal and a fourth gate connected with the second coupler. Each second coupler has a first gate connected with the second symmetric input of the diode ring, a second gate connected to ground, a third gate not connected or open and a fourth gate connected with the fourth gate of the first coupler.
Preferably inductively-acting conductor sections and capacitors bridging both inputs are connected between the symmetric inputs of the diode ring for the local oscillator signal and the connecting gates for the balancing circuit portion for the local oscillator signal. Also respective capacitors are connected in another preferred embodiment between the symmetric inputs of the diode ring for the high frequency signal and the connecting gates of the balancing circuit portion for the high frequency signal.
The diode ring advantageously comprises four diodes, which are arranged beside each other. The connecting lines between the diodes are arranged in the form of an asymmetric numeral “8” and the conductors are connected and dimensioned so that the diodes are tuned opposite to each other. This is a very compact arrangement, which guarantees a good separation between the local oscillator signal and the high frequency signal.
The conductor branch for the intermediate frequency signal connection comprises preferably two coupled conductors of length &lgr;/4, which are connected to the diode ring with the respective connectors for the high frequency signal. Each conductor is connected via an RC circuit portion to ground, whereby undesired resonances are suppressed.
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patent: 5678225 (1997-10-01), Kobayashi
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;A Monolithic Hybrid Broadband Compensated Balun, by A.M. Pavio et al., 1990 IEEE MTT-S Digest, pp. 483-486.
“Three Balun Designs for Push-Pull Amplifiers”, Application Note, TRW, Z99.
Maas S: “A Broadband Planar Monolithic Ring Mixer”, IEEE Microwave and Millimeter-Wave Monolithic Circuit Symposium, IEEE pp. 51-52.
“A Novel Planar Double-Balanced 6-18 GHZ MMIC Mixer”, by Wayne R. Brinlee, Karl R. Varian, Anthony M. Pavio, IEEE MTT Symposium Digest, 1994, Session TV 1A-s.
Bost Dwayne
Contee Joy K.
Robert & Bosch GmbH
Striker Michael J.
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