I've read a paper describing the modelling of a half-wave rectifier based on Schottky diode (Schottky model.jpg). The model is well-known, however, the author explains the scheme of such circuit and fabricates the prototype differently (please see two other figures). I do not understand why the diode's cathode is actually connected to ground? It is supposed to connected to the load as shown in the first image! Here is the description of the author: " Diode’s cathode is connected to the ground which locates at the position that magnetic field reaches its first valley to obtain maximum current in the circuit". Is there any mistake in these? Any advises are highly appreciated.
Dear Minh Lam,
one has to look at the circuits from both points of view, of low frequency (or DC) current/voltage and of RF current/voltage.
For the low frequency source, L2, diode, and load R1 (resp. RF choke 5, diode 4, and load 7) are connected in series; so, the order of the components has no influence on the resulting impedance, and hence, for a given LF voltage, on the LF current.
For the high frequency source, in the first circuit the diode and the load (R1 and C1) are arranged in series while in the second circuit it's only the diode (apart from the matching network). Not knowing the values of the components and voltages, yet assuming a low RF voltage, I guess that the diode is not used as a rectifier but provides a variable impedance controlled by the low frequency signal. In this case, the two circuits differ in that the absolute value of the impedance is lower and the relative variation of the impedance is larger in the second circuit (as seen from the RF source) as compared to the first circuit.
In the prototype, the impedance of the diode (together with the components marked 9) seems to control the amplitude of the RF signal at the coax connector resp. at the antenna; so, it looks like a case of amplitude modulation. Not knowing the purpose, I'm not sure whether it is a receiving antenna as source and an output signal at the connector, or an external source at the connector and a transmitting antenna.
Hope this helps.
please read my book (The American University Laboratories For Electrical Engineering Part 1)
It has one part on this.
As Joerg said both circuits are equivalent. The diode may be connected to ground for practical considerations. If the diode bias current is controlled by R1 shunted by the rf by pass capacitor C1 connected in series with the diode as in circuit (a) or connected in series with the choke of the low frequency source the effect is the same for the low frequency circuit and diode. However it may not be the case when taken the output at V0 node. Putting R1 and C1 as in the model circuit will cause the parasitic of C and R affecting the output high frequency. This circuit is a an AM circuit.
Best wishes
The diode based rectifier is a non linear system.
The diode has two states.
One state is an open circuit.
The second is a .7 V battery in series with a small resistance.
please read my book (The American University Laboratories For Electrical Engineering Part 3).
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