Staggered tuning

The poles of the circuit are easy to manipulate to achieve the desired response because of the amplifier buffering between stages.

Applications include television IF amplifiers (mostly 20th century receivers) and wireless LAN.

Staggered tuning also increases the steepness of passband skirts and hence improves selectivity.

This can be a problem in very narrow band applications where essentially only one spot frequency is of interest, such as a local oscillator feed or a wave trap.

[5] Both synchronously tuned and stagger-tuned schemes have a number of advantages over schemes that place all the tuning components in a single aggregated filter circuit separate from the amplifier such as ladder networks or coupled resonators.

The resonators in aggregated circuits, on the other hand, will all interact with each other, particularly their nearest neighbours.

The gain A(s), of one stage of this amplifier is given by; This can be written in a more generic form, that is, not assuming that the resonators are the LC type, with the following substitutions, Resulting in, The gain expression can be given as a function of (angular) frequency by making the substitution s = iω where i is the imaginary unit and ω is the angular frequency The frequency at the band edges, ωc, can be found from this expression by equating the value of the gain at the band edge to the magnitude of the expression, Solving this for ωc and taking the difference between the two positive solutions finds the bandwidth Δω, and the fractional bandwidth B, The overall response of the amplifier is given by the product of the individual stages, It is desirable to be able to design the filter from a standard low-pass prototype filter of the required specification.

[9] A popular choice for a polynomial with ripple is the Chebyshev response for its steep skirt.

The poles so calculated can then be used to define the tuned circuits of the individual stages.

This expression is greatly simplified if the cutoff frequency of the prototype, ω'c, is set to the final filter bandwidth ω0B/Qeff.

[12] Staggered tuning has advantages in VLSI for radio applications such as wireless LAN.

[13] The low spread of component values make it much easier to implement in integrated circuits than traditional ladder networks.