TriMode probes enable engineers to make the single-ended, differential, and common-mode signal
measurements required for high-speed bus analysis, without moving or changing probes.
In comparison to their single-ended frequency filter counterparts, differential filters are generally capable to maintain sufficient SNR, are characterized by lower total harmonic distortion (THD), feature high common-mode signal
rejection (CMRR), and furthermore with reduced input noise .
The paper also contains a fully-differential (F-D) form of the proposed filter because of the benefits of F-D structures when compared to single-ended (S-E) circuits such as better power supply rejection ratio, greater dynamic range of the processed signals, lower harmonic distortion and greater attenuation of common-mode signal
. F-D circuits have also some drawbacks, namely the area taken on the chip is larger which results in increased power consumption and more complex design in comparison to single-ended structures .
The device includes a unique common-mode regulation loop to regulate the common-mode signal
across the tank.
Alternatively, simpler structures based on etched defected ground structures (DGS) can be used to suppress the common-mode signal
. Dumbbell  and UH-shaped  DGSs have been periodically etched in the ground plane, below a pair of coupled strips signal line, to reject the common-mode noise.
These filters should be able to produce the desired differential-mode frequency responses and reduce the common-mode signal
interference at the same time, which is essential in increasing the signal-to-noise-ratio (SNR) in the receiver and improving the efficiency of the dipole antenna in the transmitter.
The ECG signal consists of three main components: the actual (differential) ECG signal, the differential electrode offset, and the common-mode signal
The center node is used for accessing the residual common-mode signal
. The AD8500 micropower precision CMOS operational amplifier features a maximum supply current of 1 [micro]A, a maximum offset voltage of 1 mV, and a typical input bias current of 1 pA.
and the undesired common-mode signal
Vcm = (Vin+) - (Vin-)
LCL is measured by applying a common-mode signal
to the cable.
It is a simple exercise in circuit analysis to demonstrate that this transmission line configuration will present twice the odd-mode impedance to a differential signal and two separate even-mode impedances to a common-mode signal
. Since any signal can be decomposed in its differential- and common-mode components, this model will predict propagation of any combination of differential-and common-mode signals
, accurately representing the behavior of the differential transmission line pair.
Second, balanced signal lines have that extra dimension of freedom: the common-mode signal
. We have to plan what we want to do with it as part of our design process.