Design a low-cost RF energy harvesting/scavenging circuit

NB: Experience with RF energy-harvesting or energy-scavenging circuits is required. Item 1: - Design an RF energy harvesting circuit to power a consumable/disposable device. - Design of the antenna is not required. The antenna type will be a resonant small-loop antenna. - The frequency will be fixed. - The frequency will most likely be 50 kHz. - Future design changes may require the device to work at a different frequency, from about 2 kHz to 60 kHz. Please consider this in the design and state how a change in the frequency would change the design. - The power available from the antenna will be very low. - The signal from the antenna will be a very low voltage, noisy sinusoid. - State the minimum input voltage level that your circuit can work with. - The energy should be stored at approximately 1.5 volts. - Specify some different options for the energy storage capacity (e.g. different sized capacitors). - At the minimum input voltage level, state the time to reach full charge. Ideally this would be less than about 10 minutes. - The components should be readily available and not too small, as the PCB will be prototyped by hand. - Provide a circuit diagram and listing of the components with supplier and prices. Item 2: - Produce a version of the circuit which stores the energy at about 22.5 volts. - Other requirements the same as Item 1. Item 3: - Produce a PCB layout for the two designs. - The layout should be suitable for rapid prototyping using an inkjet printed circuit. The printing process is described at: [login to view URL] - This means that the layout can be up to the size of an A4 piece of paper. A6 paper size is also convenient. - It should be a single-sided layout. - The traces should be relatively wide to minimize their resistance. - Test points should be provided in the layout so that the amount of energy stored may be measured.