Multi‐layered PCB distributed filter

Abstract

In this paper, multi‐layered print circuit board distributed resonators and filters are introduced. Here, the individual elements of the distributed resonator are made as part of a multi‐layered print circuit board, commonly used in the circuitry of transceiver boards. In this way, the unused real estate available on the board is used effectively. As a demonstrator of the proposed technology, a 2‐pole filter fabricated using a 5‐layer substrate and consisting of a matrix of 11 × 11 elements per resonator is fabricated and its performance is measured. Due to a large number of individual elements, which perform dimensional averaging of manufacturing inaccuracies, the filter obtained in this way not only requires no post‐production tuning, but it also has an extremely low profile of 5o, which is the lowest profile to be reported in the literature. The filter was made to operate at a centre frequency of 1.8 GHz with an absolute bandwidth of 65 MHz. The measured and computed results are in good agreement.

Ceramic‐elements‐based distributed resonators and filters

“…The second reason lies with the fact that the elements in the horizontal and vertical planes are closer to each other compared to the elements laid out Table 1. Performance comparison of PCB distributed 11 × 11 resonators of [7] and proposed ceramic-elements based distributed resonator 1 also indicates that the proposed ceramicelements based resonator has the potential to exhibit the highest Q u factors and optimal volume utilisation, however that is dependent on the quality of the ceramic materials and, ultimately cost. Nevertheless, Table 1 sheds light on the achievable gains using the proposed approach.…”

“…The second reason lies with the fact that the elements in the horizontal and vertical planes are closer to each other compared to the elements laid out along the diagonal lines. A comparison between the proposed resonator and the multi‐layered PCB distributed resonator [7] is presented in Table 1, both made to operate at a frequency of 3.35 GHz. The two ceramic materials used for the purpose of this comparison have the following dielectric properties: The first material [10] has ε r = 40 and the Q u * f product of 65,000, yielding its tan( δ ) = 5.5 × 10 −5 , while the second material [11] has ε r = 37 and the Q u * f product of 1,050, corresponding to tan( δ ) = 3.3 × 10 −3 , both at 3.35 GHz.…”

“…The two ceramic materials used for the purpose of this comparison have the following dielectric properties: The first material [10] has ε r = 40 and the Q u * f product of 65,000, yielding its tan( δ ) = 5.5 × 10 −5 , while the second material [11] has ε r = 37 and the Q u * f product of 1,050, corresponding to tan( δ ) = 3.3 × 10 −3 , both at 3.35 GHz. The multi‐layered PCB resonator of [7], has an average dielectric permittivity of ε r = 3.11 and tan( δ ) = 1.8 × 10 −3 . Table 1 also indicates that the proposed ceramic‐elements based resonator has the potential to exhibit the highest Q u factors and optimal volume utilisation, however that is dependent on the quality of the ceramic materials and, ultimately cost.…”

“…The original distributed resonator concept has been successfully demonstrated in [3][4][5][6][7], using conductive individual resonant elements, where it was shown that extremely low profiles are achievable. It was further shown in [7] that a distributed resonator implemented in a multi-layered PCB achieves an unloaded Q-factor of about 300, for a resonator profile of about 5 o . The principle of operation of the distributed resonator is wellexplained in [3][4][5][6][7], and primarily relies on the general theory of coupled resonator systems, which states that resonators in isolation operate at a higher frequency compared to the case when they are coupled to each other.…”

“…It was further shown in [7] that a distributed resonator implemented in a multi-layered PCB achieves an unloaded Q-factor of about 300, for a resonator profile of about 5 o . The principle of operation of the distributed resonator is wellexplained in [3][4][5][6][7], and primarily relies on the general theory of coupled resonator systems, which states that resonators in isolation operate at a higher frequency compared to the case when they are coupled to each other. The number of resonant elements, together with the extent of their mutual coupling ultimately determine the reduction of the profile of the resonator obtained in this way.…”