GB2292484A

GB2292484A - Microwave transmit/receive assembly

Info

Publication number: GB2292484A
Application number: GB9416638A
Authority: GB
Inventors: Dilip Panchal; Michael Griffiths; Bharat Patel; David Alexander Cowan
Original assignee: CONTINENTAL MICROWAVE TECHNOLO
Current assignee: CONTINENTAL MICROWAVE TECHNOLO
Priority date: 1994-08-17
Filing date: 1994-08-17
Publication date: 1996-02-21
Anticipated expiration: 2014-08-17
Also published as: GB9416638D0; WO1996005660A1; GB2292484B; AU3229995A

Abstract

A microwave transmit/receive assembly comprising a microwave integrated circuit MIC module mounted on a printed circuit board PCB, and a microwave filter block E. The MIC module comprises a metal baseplate B having a dielectric layer carrying conductive microstrip tracks forming microwave integrated circuitry for processing transmitted and received signals. The printed circuit board carries additional circuitry and the MIC module includes stripline-to-waveguide transitions for coupling signals between the MIC circuits and waveguide interfaces of the filter block. The filter block may be an E-plane filter block and the PCB has an aperture 5 over which the MIC is located and through which the filter block projects. <IMAGE>

Description

MICROWAVE TRANSMIT/RECEIVE ASSEMBLY This invention relates to a microwave transmit/receive assembly, particularly for a microwave radio system.

Microwave radio systems are known which use a common antenna for transmitting and receiving microwave signals.

Hitherto, the microwave-frequency portions of the transmit/receive circuitry have involved several assemblies of relatively complex construction, interconnected by coaxial cables and/or waveguides.

We have now devised a microwave transmit/receive assembly of relatively straightforward and correspondingly less expensive construction, as will be apparent from the following description.

In accordance with this invention, there is provided a microwave transmit/receive assembly which comprises a printed circuit board, a microwave integrated circuit (MIC) module mounted on the printed circuit board, and a microwave filter block, particularly an E-plane filter block, the MIC module comprising a metal base plate having a dielectric face layer which carries conductive tracks forming microstrip transmit and receiver circuitry, the MIC module including stripline-towaveguide transitions for coupling signals between the MIC circuits and respective waveguide interfaces of the filter block.

In an embodiment of the invention to be described herein, the filter block includes an interface to a common transmit/receive antenna. The filter block further comprises waveguide interfaces for signal connection to the MIC and metallic filter foils for processing of the microwave transmit and receive signals.

The conductive paths on the baseplate preferably form microwave components e.g. attenuators, filters and mixers (for signal upconversion or downconversion) for processing the signals to be transmitted via the antenna and for processing the signals received via the antenna.

Discrete components, including active components such as unpackaged semiconductor transistors or diodes, or monolithic microwave integrated circuits (MMIC's) are preferably mounted to the baseplate. Preferably these components are located in respective apertures in the baseplate and held in position by resin or other composition which fills the space within the aperture and surrounding the component, the resin or other composition having been allowed or caused to set so as to bond the component in position.

In the embodiment to be described, the assembly comprises additional circuitry carried on the printed circuit board (or PCB), which is positioned face-to-face against the underside of the MIC baseplate. Connections between the circuits on the MIC and the circuits on the PCB are effected by hermetic transistor header feedthroughs which are secured in holes formed in the MIC baseplate: on the MIC side, bond wires link the MIC circuit tracks to respective conductors of the transistor header whilst, on the PCB side, the transistor header pins plug into through-holes or sockets in the PCB. The transistor header feedthroughs (conventionally used as headers for leaded transistors) are inexpensive components but provide effective electrical connection between the MIC and PCB, particularly for the transfer of DC voltages and UHF and low microwave frequency signals.

It will be appreciated that the microwave transmit/receive assembly in accordance with this invention involves close integration of transmit and receive circuits and of PCB, MIC, and E-plane assemblies. Further, the interconnections between the E-plane filter block and MIC module, and between the MIC module and PCB, are simple, inexpensive yet effective and reliable. In particular, all connections to or from the MIC module are via the inexpensive transistor header feedthroughs for signals below typically 3 Ghz, and via waveguide interfaces for higher frequencies.

An embodiment of this invention will now be described by way of example only and with reference to the accompanying drawings, in which: FIGURE 1 is a plan view of a microwave transmit/receive assembly in accordance with this invention, shown with a cover of the MIC module partially broken away to show details of the latter; FIGURE 2 is a sectional view through the transmit/receive assembly of Figure 1, shown with one of the main halves of the E-plane filter block partially broken away; FIGURE 3 is an end view of the transmit/receive assembly; and FIGURE 4 is an enlarged sectional view to show use of a transistor header to interconnect circuitry on the MIC with circuitry on a printed circuit board and also the mounting of a semiconductor device.

Referring to the drawings, a microwave transmit/receive assembly in accordance with this invention comprises a microwave integrated circuit module MIC mounted to an E-plane filter block E: a printed circuit board PCB carries additional circuitry and has a rectangular aperture 5 over which the MIC module sits, and through which the E-plane filter block projects.

The MIC module comprises a metal baseplate B having a ptfe loaded low loss dielectric layer D carrying conductive microstrip tracks T forming microwave integrated circuitry as will be described. The baseplate B is formed with four apertures 1, 2, 3, 4 which provide microstrip-to-waveguide transitions: the MIC module is bolted to the end of the Eplane filter block so that the transition apertures 1 to 4 align with openings in the end of the filter block, these openings forming the input and output ports to waveguide channels of the filter block with choke grooves CH to provide high isolation between the waveguides. Over each transition aperture, a backshort BS is mounted: in Figure 1, the backshort for transition aperture 4 is shown partly broken away to show the probe which projects across the transition aperture from the microstrip circuitry on the baseplate B.The MIC module further comprises a covering lid C, the rim of which fits onto a recessed ledge running around the periphery of the baseplate B and is bonded to it to provide a hermetic seal for the assembly: the lid C also has internal partitions P which fit into corresponding grooves formed in the top side of the baseplate B in order to provide isolation between circuit elements.

For interconnecting the circuitry on the MIC module and the circuitry on the printed circuit board PCB, the MIC module baseplate B is formed with a number of circular holes into each of which a transistor header (e.g. T072 style) is bonded, as shown for transistor header TH in Figure 4. On the MIC side, bond wires W link the MIC circuit tracks to the individual conductors of the transistor header, and on the PCB side, the transistor header pins plug into sockets S formed through the PCB and which link to the PCB tracks Tl. The various transistor headers (shown for example at TH1, TH2 .... in Figure 1) are used to transfer DC voltages and UHF or low microwave frequency signals between the PCB and MIC.

The MIC module carries circuits for processing signals to be transmitted and for processing received signals, in stripline form. Various semiconductor chips M are also mounted to the MIC baseplate, and bonded to the tracking T with wire links W.

Figures 2 and 3 show the E-plane filter block, which is formed of two main halves 10,12 bolted together with filter foils clamped between them: Figure 2 shows the filter block with one half broken away, to show the waveguide channels and the filter foils FL3, FL4, FL5. The diplexer port 14 is, in use, connected to the common transmit/receive antenna of the microwave radio system.

Claims

1) A microwave transmit/receive assembly which comprises a printed circuiit board, a microwave integrated circuit (MIC) module mounted on the printed circuit board, and a microwave filter block, the MIC module comprising a metal baseplate having a dielectric face layer which carries conductive tracks forming microstrip transmit and receive circuitry, the MIC module including stripline-to-waveguide transitions for coupling signals between the MIC circuits and respective waveguide interfaces of the filter block.

2) A microwave transmit/receive assembly as claimed in claim 1, wherein the filter block comprises an E-plane filter block.

3) A microwave transmit/receive assembly as claimed in claim 1 or 2, wherein the filter block includes an interface to a common transmit/receive antenna.

4) A microwave transmit/receive assembly as claimed in any preceding claim, wherein the filter block comprises waveguide interfaces for signal connection to the MIC and metallic filter foils for processing of the microwave transmit and receive signals.

5) A microwave transmit/receive assembly as claimed in any preceding claim, wherein the conductive paths on the baseplate form microwave components for processing the signals to be transmitted via the antenna and for processing the signals received via the antenna.

6) A microwave transmit/receive assembly as claimed in claim 5, wherein the conductive paths on the baseplate form attenuators, filters and mixers for signal upconversion and downconversion.

7) A microwave transmit/receive assembly as claimed in any preceding claim, wherein discrete components are mounted to the baseplate.

8) A microwave transmit/receive assembly as claimed in claim 7, wherein the discrete components comprise unpackaged semiconductor transistors or diodes, and/or monolithic microwave integrated circuits.

9) A microwave transmit/receive assembly as claimed in claim 7 or 8, wherein the discrete components are located in respective apertures in the baseplate.

10) A microwave transmit/receive assembly as claimed in claim 9, wherein each said discrete component is held in position on the baseplate by means of a composition which fills the space within the aperture and surrounds the component, the composition having been allowed or caused to set so as to bond the component in position.

11) A microwave transmit/receive assembly as claimed in any preceding claim, wherein all connections to and from the MIC module are effected via transistor header feedthroughs for signals below 3GHZ, and via waveguide interfaces for higher frequencies.

12) A microwave transmit/receive assembly as claimed in any preceding claim wherein the printed circuit board carries additional circuitry which is positioned face-to-face against the underside of the MIC baseplate.

13) A microwave transmit/receive assembly substantially as herein described with reference to the accompanying drawings.