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Low–Power Commercial, Automotive, and Appliance Connections
Published in Paul G. Slade, Electrical Contacts, 2017
An insulation displacement connection (IDC) is also used as a method for attaching the cable to the terminal. As shown in Figure 6.7, the cable is fed into an IDC slot. During insertion, insulation to the cable is cut, the slot is forced to expand, and an electrical contact with the wire is made. Examples of such a termination method were reported in the literature [6–8]. The inherent advantage of IDC connection is the consistent contact force between the wire and the IDC slot. Also, such termination process is attractive for automation because the cables going to the same connector can be terminated simultaneously. On the other hand, crimping and soldering are done individually.
Introduction to Biosensors and Bioelectronics
Published in George K. Knopf, Amarjeet S. Bassi, Smart Biosensor Technology, 2018
George K. Knopf, Amarjeet S. Bassi
In general, capacitive biosensors take advantage of the changes in dielectric properties of an electrode surface when exposed to the analyte. Capacitive measurement may be the change in the capacitance between two metal conductors in close proximity with the recognition element immobilized between them (i.e., interdigitated electrodes) (Hobdell 1979). An example of an interdigitated capacitor (IDC) in a low-pass electrical filter circuit is shown in Figure 1.4. The IDC electrodes are often printed directly on the sensor substrate. The IDC behaves similarly to an electrical plate capacitor composed of two parallel metal plates separated by a specified distance with a dielectric material inserted between them (Berggren et al 2001). The capacitance is C=εε0Ad where ε is the dielectric constant of the medium between the plates, ε0 = 8.885419 pF/m (permittivity of free space), A is the area of the plates, and d is the distance between them. The equation states that when there is a change in the dielectric property ε of the material between the plates, there will be a corresponding change in capacitance. Due to the low dielectric constant of the analyte (e.g., bacteria) compared with the solution (e.g., urine) there will be a change in the dielectric properties between the electrodes, causing an alteration in the capacitance. Furthermore, the capacitance and sensor sensitivity will increase as the distance between the two conductors decreases. It is also important that the passivation layer between the electrode and binding agent have a very high dielectric constant. Typically, a thin 1-μm-thick parlyene polymer layer covers the conductors (IDC traces) to reduce the Faradic currents in the circuit.
Interdigital Capacitor Based Compact Microstrip Bandpass Filter with Wide Stopband
Published in IETE Journal of Research, 2021
A bandpass filter (BPF) is one of the most important parts of the devices working in microwave frequency range. With the rapid development of modern communication systems, more and more miniaturized microstrip filters with excellent performances are required [1–2]. In general, there are three typical methods available for designing BPFs [3]. The first method is by introducing transmission zeros (TZs) in the passband, the second one is by adding several resonators and the last one is by using higher order resonant modes of the stepped impedance resonators or stub loaded resonators [4–6]. Among them stepped impedance resonators (SIR) based designs are more popular for their higher order resonant modes. But such traditionally designed filters provide a limited degree of freedom and also suffer from large electrical size. Size reduction and spurious suppression [7–8] of such filters are major issues in planar microwave filter design. Nowadays, the interdigital structures are being used widely to design bandpass filters as it allows suitable integration and miniaturization of the circuit [9–11]. The interdigital capacitor (IDC) uses the capacitance which occurs across a narrow gap between copper conductors. These structures allow to increase the electrical length within the smaller region [12–13]. The susceptance can be varied by varying the number of fingers of interdigital capacitors. To reduce the circuit size and to improve the performance, defected ground structures (DGS) and defected microstrip structures (DMS) are usually used. Similar to DMS, DGS can acquire slow wave characteristics and can improve stopband performance. Compared to the common methods of employing DMS or stubs to improve stopband performance [14–16], the DGS structures are preferred as they do not disturb the signal integrity on the signal plane.