Radio Frequency (RF) & Wireless Design

The most common mistake for someone to make when selecting the correct RF coax, wire, antenna, PCB, or waveguide connector is choosing the connector and then trying to make it work. This is a common mistake where the mechanical features or interface take a higher or highest priority in the design requirements. This will lead to major headaches and multiple iterations of frustration before (hopefully) getting it right for the RF to actually function or to obtain the performance results that you expect.

So how do you avoid this mistake ? Well you design the interconnection pieces around the frequency of interest with the amount of RF power being delivered and then with the amount of RF power losses that can be expected or tolerated. This translates to the RF Power Budget spreadsheet being the first place to start.

In a proper RF design the RF Power Budget spreadsheet is the guiding tool that determines the proper initial selection of RF components. This is because in an RF system, RF power losses and gains can be considerable and the magnitude of these effects can be vetted out early to determine the significance in the downstream and upstream circuit paths.

Typically RF power is determined by signal strength, the distance necessary to travel, and the amount of recovery of the signal due to losses in the path (path loss) of travel. This may not simply be point to point, but also from RF reflections from many objects along the way. Each wave may travel with variations in time delays (phase) that can add up to an accumulated signal.

Also the polarization (horizontal and vertical) wave orientations will affect the amount of signal recovery from the RF sensor (antenna or waveguide) also determining how much RF power is recovered.

Since RF power is in logarithmic scales receiver sensitivities up to 160 dBi or 10^16 or 10,000,000,000,000,000 are possible !! However losses over this are also possible !! So there may not be any signal recovered. Therefore every nuance in every part must be considered and therefore even the dumb coax connector.

By analyzing the frequency first, the power losses next, the interfaces (wire, cable, PCB, waveguide), and lastly the mechanical requirements can the proper choice be made.

And be aware that most RF components do have many RF connector options even if the manufacturer does not specifically call them out on their website or datasheets. Do NOT assume that you needs are not available ordering choices !! It may be simply an email or phone call to get what you need or want.

Also all connectors are rated to a frequency based upon the -3dB power point which translates to a 50% power loss, which is not a good thing. So over designing with an RF connector that is only about half of the available bandwidth is a smart decision (e.g. WiFi 5.6 GHz using a TNC or N-type rated at 11 GHz rather than a really good BNC rated at 6 GHz).