Wave transmission lines and networks – Coupling networks – Balanced to unbalanced circuits
Patent
1995-03-28
1998-09-01
Lee, Benny
Wave transmission lines and networks
Coupling networks
Balanced to unbalanced circuits
333 33, H01P 5107
Patent
active
058015990
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a waveguide to microstrip transition where a waveguide probe is passed from the waveguide through a circuit board before connecting to the microstrip line. The invention also relates to a microstrip to microstrip transition where a signal carried on the microstrip requires to pass through a multilayer circuit board. The invention is particularly related to transitions for use with radio frequency signals.
DESCRIPTION OF THE RELEVANT PRIOR ART
In a double-sided or multilayer circuit board which is connected to a waveguide, one way in which signals may be taken from the waveguide to the board requires a probe to pass through the waveguide wall and the board so that when the probe protrudes into the waveguide it will pick up signals propagating in the waveguide. In order for such an arrangement to work properly it is necessary to connect the probe to a microstrip conductor. This is typically done by drilling a hole in the circuit board prior to etching the board then fitting a probe in the drilled hole. This arrangement would provide a low loss transition as long as there is no or little loss of signal into the board's materials, such as polytetrafluoroethylene (PTFE) and (FR4), and the probe passing through the board's materials does not present too great a mismatch. However, signal loss into the board's materials is generally significant thereby. resulting in over 1 dB. of loss. This is unacceptable for a low-noise receiver. It is believed that the ground planes on each side of the FR4 act as a parallel plate waveguide into which signals can couple resulting in extra losses and also changing the impedance of the transition causing a mismatch to the microstrip line. Any mismatch will also result in loss of signal.
An object of the present invention is to provide an improved transition which obviates or mitigates at least one of the aforementioned disadvantages.
SUMMARY OF THE INVENTION
In its broadest aspect this is achieved by providing a plurality of plated holes in a circuit board and disposing these plated holes around the RF waveguide or microstrip to microstrip transition and connecting these plated holes to ground. This results in a transition with a substantially improved performance which has much less loss than the prior art arrangement.
In a preferred arrangement all the holes, including the hole receiving the probe are plated through-holes for reasons of simplicity and cost. In an alternative arrangement blind holes can be used The plurality of holes can be provided in a multilayer board or in a double-sided board.
Conveniently, four of these plated through-holes are disposed around the waveguide or microstrip to microstrip probe and are ideally placed on the circumference of a circle centered on the probe. The holes are in close proximity to the feedthrough.
According to one aspect of the present invention there is provided an RF waveguide to circuit transition wherein a waveguide probe passes through a circuit board and is connected to a signal conductor on the circuit board, the circuit board having a ground plane, a plurality of plated holes disposed in proximity to and spaced around the waveguide probe such that the transition impedance is as close as possible to the characteristic impedance of the microstrip line, the plated holes being coupled to the ground plane to minimize leakage of signals carried by the probe into the board. Preferably, the holes are plated through-holes. Alternatively, the holes are plated blind holes. Preferably also the probe hole is plated.
Preferably also, four plated holes are disposed around the periphery of the waveguide probe. Conveniently the plated holes being placed on the circumference of a circle centred on the probe. Alternatively, three, five or any suitable number of holes may be used to achieve satisfactory performance.
It has been found that four such plated through-holes provide satisfactory results, but the spacing of the holes is important in relation to the feed-through, holes requir
REFERENCES:
patent: 2877429 (1959-03-01), Sommers
patent: 3895435 (1975-07-01), Turner et al.
patent: 4080579 (1978-03-01), Fassett
patent: 4494083 (1985-01-01), Josefsson et al.
patent: 4562416 (1985-12-01), Sedivic
patent: 4754239 (1988-06-01), Sedivec
patent: 4846696 (1989-07-01), Morelli et al.
patent: 5045820 (1991-09-01), Leicht et al.
patent: 5057798 (1991-10-01), Moye et al.
patent: 5258727 (1993-11-01), DuPuis et al.
patent: 5280253 (1994-01-01), Deki et al.
Baird Andrew Patrick
Flynn Stephen John
Cambridge Industries Limited
Lee Benny
LandOfFree
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