Mmds integrated down converter




















The reference oscillator utilizes phase lock loop circuitry and is located on the separate daughter board to minimize the potential for digital noise in the RF circuits This signal is delivered into a divider circuit and is then transferred into the phase comparator for comparison to a reference signal from the stable reference oscillator If any differences are detected, the control circuit adjusts the voltage control output V co and delivers it back over line B to oscillator Noise and signal interference are minimized by 1 separating the reference oscillator onto a second printed circuit board, 2 spacing the separate printed circuit board from the oscillator board, and 3 orienting the bottom ground plane of the second printed circuit board to face the bottom ground plane of the oscillator board.

The spacing and the orientation of ground planes and are illustrated in FIGS. Once the RF signal on lines is mixed to the desired output frequency by circuit , the output signal is delivered on lines into the bandpass filter The bandpass filter filters the output signal on lines according to customer requirements but usually in the range of MHz. The filtered signals are delivered on lines to the output amplifier which functions to amplify the signals with approximately 18 dB gain.

Finally, the coax 32 is connected directly to the output of the amplifier and delivered as shown in FIG. It is to be expressly understood that a number of different electronic circuits could be utilized as a down converter for MMDS applications and that the present invention is not to be limited to the application of a particular design. The two portions are designed to fit together to form a weatherproof housing as shown.

The driven elements and are held within the housing by pedestals A sub-reflector is held within the housing by slots Also shown in FIG. Printed circuit board at the feed end has three formed slots , , and Driven element is inserted into slot while driven element is inserted into slot Connection leg of the driven element is soldered to top ground plane and bottom ground plane of oscillator board The balun center conductor has its end soldered to copper pads and It is to be expressly understood that the design of balun could vary and that the teachings of the present invention are not limited to the design illustrated.

As can be observed, the driven elements and are directly soldered to the oscillator board to directly input the RF filter A separate coax is not required. The advantages of this direct connection are 1 the elimination of a weather seal, 2 lower insertion loss, 3 lower cost, and 4 improved impedance matching.

As shown in FIGS. The front end filter shield has the bottoms of its opposing sides and opposing ends soldered to the ground top plane of the oscillator board and to the bottom ground plane Opposing arcuate cutouts are not soldered to the ground plane so as to provide signal pathways. Three ground clips are soldered to the filter shield as shown in FIG. The ground clips are designed to firmly abut the inside sidewalls of the support boom The four ground clips firmly position and hold the input end of the oscillator board , connected to the driven elements and , in place within the support boom The four ground clips also provide electrical contact with the interior sidewalls of the metal support boom.

The end is also shown fully supported and positioned within the interior of the boom by the ground clips and The four ground clips and firmly electrically contact the grounded metallic boom to provide substantial shielding of the input R filter and to prevent unwanted signals from propagating into the hollow interior of the boom and into the downstream circuitry of the down converter.

For example, the front end filter shield eliminates the potential for out of band including IF frequencies passing through the cavity of the boom and entering the active circuitry of the down converter. The boom is fully grounded to the shield which in turn is grounded to the ground planes and It is to be expressly understood that a number of different configurations for designing the shield of the present invention could be utilized.

In FIGS. The coax bracket formed of solid conductive material e. The end of the oscillator board has two opposing ground pads and with the output signal lead disposed there between. Lead is connected to the output of amplifier The coax bracket has two legs and On the external opposing sides of each leg, and , are soldered two ground clips Each leg and has a formed slot which is designed to slip over end In other words, the upper and lower edges of the slots are soldered on both sides and of the ground plane.

This provides a solid electrical ground connection. The center conductor is mounted through the innerbarrel and the center conductor is soldered to the strip The ground sheath of coax 32 is crimped to the innerbarrel Crimp ring is used to accomplish this. In this fashion, the ground sheath is fully grounded to the coax bracket which in turn is fully grounded to the ground plane of the circuit board to prevent unwanted signals from entering the boom via the coax or the end of the boom nearest the antenna.

The ground clips center the end of the oscillator board within the hollow interior of boom in a fashion set forth in FIG. The ground clips also fully ground the end of the board to the internal sides of the support boom It is clear that the down converter circuitry is fully integrated into the boom. In comparison to standard separate down converters, the housing for the down converter is eliminated as well as the windload associated therewith. The coax connects directly with the coax shield at a point which is fully grounded.

It is to be expressly understood that the claimed invention is not to be limited to the description of the preferred embodiment but encompasses other modifications and alterations within the scope and spirit of the inventive concept. We claim: 1. The system of claim 1 wherein said support boom is formed in a square cross-sectional shape. The system of claim 1 wherein said RF filter shield is formed from solid conductive material.

The system of claim 1 wherein said coax ground shield is formed from solid conductive material. The system of claim 5 wherein said support boom is formed in a square cross-sectional shape. The system of claim 5 wherein said RF filter shield is formed from solid conductive material. The unit was originally designed to work with or without this microcontroller. Just remove the microcontroller board completely, by desoldering the feedthroughs on the IF amplifier side.

Undo all the screws on the microcontroller board. Desolder the LED and remove. The microcontroller board should then come straight out. Jumper the locations shown in the following photograph. You can take power from this juncture to light an LED to indicate power. Use a Ohm resistor in series with the LED. Take the LED to ground on the LED side of the casing by means of an earthing screw from the vacated microcontroller board.

If it is intended to use the downconverter as a receive converter for the 13cm SSB portion, then a crystal change can perhaps be avoided. Locking is very reliable, but the loading of standard 10MHz crystals is not quite optimum, and the PLL output is around KHz or so too high.

This cannot be trimmed out. A 2GHz LO does make the use of a scanner quite straightforward however, as one can easily add the '2' in front of the displayed frequency. Changing the LO in the case of using the converter at MHz is mandatory. The author is currently attempting to establish crystal specification, and will add this when it is determined.

The PLL being the 'next one up' from the one in the Cal Amp would suggest that crystal characteristics are going to be very similar. I will presume that you have read the retuning procedure for the stripline filter on the cal-amp downconverter, and will not duplicate the proceedings here.

The striplines are however thinner, and more dexterity is required to work in the confined area. The results however are very good. Attack points are at the extremes of the strip fingers and also on the width of the input and output striplines, and also the large rectangular bulge on the second strip from the right on the photograph. Improving the IF amplifier response. The filter exhibits a low pass characteristic and starts to roll off after MHz.

The sampler is no longer required, some gain goes down the plug because of this. An inductive trap in the first filtering stage prior to the first MMIC amplifier also provides sharp rolloff from HF to past MHz, which is not needed.

To optimise the first section leading from the IF port of the mixer PCB to the first MMIC, we remove the 56nH inductor if present see later in this section , remove one of the 1nF capacitors which is now suplus, and bridge this with a small piece of wire or tinned foil.

The section between the output of the first and input of the second MMIC can be improved by removing all parts that comprise the sampler and merely coupling the two mmics together with a solitary 1nF SMD cap. The filter could be the aforesaid high pass design or could be designed as a band-pass filter in the range of about to MHz.

The low noise amplifier provides sufficient gain to establish overall noise figure. The output of the low noise amplifier is delivered over lines to the sub-harmonic mixer and oscillator It is to be understood that any suitable mixer design such as an active or single diode design could be utilized. In the preferred embodiment, the oscillator is a single bi-polar transistor in a common collector configuration.

Frequency stability is achieved by locking the oscillator to a stable reference oscillator which is delivered over line from the daughter board , as shown in FIGS. The reference oscillator utilizes phase lock loop circuitry and is located on the separate daughter board to minimize the potential for digital noise in the RF circuits This signal is delivered into a divider circuit and is then transferred into the phase comparator for comparison to a reference signal from the stable reference oscillator If any differences are detected, the control circuit adjusts the voltage control output V co and delivers it back over line B to oscillator Noise and signal interference are minimized by 1 separating the reference oscillator onto a second printed circuit board, 2 spacing the separate printed circuit board from the oscillator board, and 3 by orienting the bottom ground plane of the second printed circuit board to face the bottom ground plane of the oscillator board.

The spacing and the orientation of ground planes and are illustrated in FIGS. Once the RF signal on lines is mixed to the desired output frequency by circuit , the output signal is delivered on lines into the band pass filter The band pass filter filters the output signal on lines according to customer requirements but usually in the range of MHz. The filtered signals are delivered on lines to the output amplifier which functions to amplify the signals with approximately 18 dB gain.

Finally, the coax 32 is connected directly to the output of the amplifier and delivered as shown in FIG. It is to be expressly understood that a number of different electronic circuits could be utilized as a down converter for MMDS applications and that the present invention is not to be limited to the application of a particular design. Front End Filter Shield. The two portions are designed to fit together to form a weatherproof housing as shown.

The driven elements and are held within the housing by pedestals A sub-reflector is held within the housing by slots Also shown in FIG. Printed circuit board at the feed end has three formed slots , , and Driven element is inserted into slot and has end connection leg soldered to the top and bottom sides of the printed circuit board Connection leg of the driven element is soldered to top ground plane and bottom ground plane of oscillator board The balun center conductor has its end soldered to copper pads and It is to be expressly understood that the design of balun could vary and that the teachings of the present invention are not limited to the design illustrated.

As can be observed, the driven elements and are directly soldered to the oscillator board to directly input the RF filter A separate coax is not required. The advantages of this direct connection are 1 the elimination of a weather seal, 2 lower insertion loss, 3 lower cost, and 4 improved impedance matching. As shown in FIGS. The front end filter shield has the bottoms of its opposing sides and opposing ends soldered to the ground plane of the oscillator board and to the bottom ground plane Opposing arcuate cutouts are not soldered to the ground plane so as to provide signal pathways.

Three ground clips are soldered to the filter shield as shown in FIG. The ground clips are designed to firmly abut the inside sidewalls of the support boom The four ground clips firmly position and hold the input end of the oscillator board connected to the driven elements and in place within the support boom The four ground clips also provide electrical contact with the interior sidewalls of the metal support boom.

The end is also shown fully supported and positioned within the interior of the boom by the ground clips and The four ground clips and firmly electrically contact the grounded metallic boom to provide substantial shielding of the input RF filter and to prevent unwanted signals from propagating into the hollow interior of the boom and into the downstream circuitry of the down converter.

For example, the front end filter shield eliminates the potential for out of band including IF frequencies passing through the cavity of the boom and entering the active circuitry of the down converter.

The boom is fully grounded to the shield which in turn is grounded to the ground planes and It is to be expressly understood that a number of different configurations for designing the shield of the present invention could be utilized.

Coax Bracket. In FIGS. The coax bracket formed of solid conductive material e. The end of the oscillator board has two opposing ground pads and with the output signal lead disposed there between.

Lead is connected to the output of amplifier The coax bracket has two legs and On the external opposing sides of each leg, and , are soldered two ground clips Each leg and has a formed slot which is designed to slip over end In other words, the upper and lower edges of the slots are soldered on both sides and of the ground plane.

This provides a solid electrical ground connection. The center conductor is mounted through the innerbarrel and the center conductor is soldered to the strip The ground sheath of coax 32 is crimped to the innerbarrel Crimp ring is used to accomplish this.

In this fashion, the ground sheath is fully grounded to the coax bracket which in turn is fully grounded to the ground plane of the circuit board to prevent unwanted signals from entering the boom via the coax or the end of the boom nearest the antenna.

The ground clips center the end of the oscillator board within the hollow interior of boom in a fashion set forth in FIG. The ground clips also fully ground the end of the board to the internal sides of the support boom It is clear that the down converter circuitry is fully integrated into the boom. In comparison to standard separate down converters, the housing for the down converter is eliminated as well as the windload associated therewith.

The coax connects directly with the coax shield at a point which is fully grounded. It is to be expressly understood that the claimed invention is not to be limited to the description of the preferred embodiment but encompasses other modifications and alterations within the scope and spirit of the inventive concept.

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