An assembly for shielding an implanted medical device from the effects of high-frequency radiation and for emitting magnetic resonance signals during magnetic resonance imaging. The assembly includes an implanted medical device and a magnetic shield comprised of nanomagnetic material disposed between the medical device and the high-frequency radiation. In one embodiment, the magnetic resonance signals are detected by a receiver, which is thus able to locate the implanted medical device within a biological organism.

Magnetic resonance imaging coated assembly

To reduce the impact of image frequencies generated by mixing an incident carrier signal down to a relatively low intermediate frequency signal used in subsequent signal processing, a mixing frequency is selected such that the generated intermediate frequency signal has a frequency offset relative to DC that is substantially that of a single channel spacing between frequency adjacent incident carrier signals, as shown in FIG. 2. Image rejection is further improved through the integration of a current-driven polyphase filter (36) directly between an input stage (Q1 to Q4) and a mixer stage (Q5 to Q12) of an image reject mixer (FIG. 4) such as to mitigate quadrature divergence between separate in-phase and quadrature paths within the image reject mixer.

Image reject mixer, circuit, and method for image rejection

A method of controlling operation of a wireless device configured in a zero intermediate frequency architecture including a DC loop and a gain loop. The method includes processing energy in a wireless medium to generate a corresponding receive signal, monitoring the receive signal via a predetermined measurement window, detecting a changed condition in the channel, holding the gain feedback control loop at a constant gain level, and operating the DC loop in an attempt to search a stable DC value for the receive signal while the gain loop is held constant. A first case is DC saturation, where the gain is held constant until DC is controlled. A second case is clear channel assessment, where a prior stored gain setting is applied to the gain loop after detecting the end of the packet. A third case is preparation for receiving an expected acknowledgement packet after transmitting a packet, where again a prior stored gain setting is applied to the gain loop and DC is searched.

Packet acquisition and channel tracking for a wireless communication device configured in a zero intermediate frequency architecture

A passive harmonic switch mixer is shown that is immune to self mixing of the local oscillator greatly reducing leakage noise, pulling noise, and flicker noise when used in a direct conversion receiver or direct conversion transmitter circuit. The passive harmonic switch mixermixes an input signal received on an input port with an in-phase oscillator signal and a quadrature-phase oscillator signal and outputs an output signal on an output port. Because the quadrature-phase oscillator signal is the in-phase oscillator signal phase shifted by 90 Â°, the passive harmonic switch mixer operates with a local oscillator running at half the frequency of the carrier frequency of an RF signal. Additionally, because the passive harmonic switch mixer has no active components, the DC current passing through each switch device is reduced and the associated flicker noise of the mixer is also greatly reduced.

Passive harmonic switch mixer

A single chip RF communication system and method is provided including a transmitter and a receiver The RF communication system in accordance with the present invention can include an antenna that receives/transmits RF signals, a PLL that generates multi-phase clock signals having a frequency different from a carrier frequency and a reference signal having the carrier frequency, a demodulation-mixer that mixes the received RF signals with the multi-phase clock signals having the frequency different from the carrier frequency to output signals having a frequency reduced relative to the carrier frequency, two stage amplification that amplifies a selected channel signal to a required dynamic level, and an A/D converting unit for converting the RF signals from the mixing unit into digital signals The two stage amplification can provide the selected channel signal with sufficient gain, even when an adjacent channel signal is output by the demodulation mixer with greater amplitude or power

Single chip cmos transmitter/receiver and method of using same

A quadrature mixer architecture that mixes the in-phase and quadrature phases within the same cell. The input voltage is applied to the base of a voltage conversion transistor, which converts the input voltage into a bias current on the collector of the voltage conversion transistor. Four mixer transistors have their emitters connected to the collector of the drive transistor so as to receive the bias current. The bases of a first pair of the upper transistors are fed with the in-phase components (e.g., 0 and 180°), while the bases of the other pair of transistors are fed with the quadrature phase components (e.g., 90 and -90° of a local oscillator). The collectors of the mixer transistors are taken as the four output components of the circuit, I out , I out .sbsb.--, Q out , and Q out .sbsb.--.

Quadrature mixer method and apparatus

A multi-band phase locked loop employing multiple, switchable voltage controlled oscillators. A single PLL is provided having a different voltage controlled oscillator for each desired frequency band of operation. The transfer function of the phase detector in the phase locked loop is switched responsive to the particular band selected so as to maintain the loop natural frequency at the same point regardless of other changes in the loop transfer function that are associated with operating at alternate frequencies, such as, but not limited to, changes in the frequency slope of the voltage controlled oscillators and changes in the division ratio of the loop divider circuit.

Jorgen Bojer

Papers

Quadrature mixer method and apparatus

Multiband phase locked loop using a switched voltage controlled oscillator