Abstract:
In method of communicating with a deployed communication system, for example a transponder (40), a response signal is received from the transponder (40) in response to an interrogation signal that has been transmitted to the transponder (40) at a first carrier frequency (210). The response signal comprises (i) the interrogation signal shifted by the transponder to a second, different, carrier frequency (220), the second carrier frequency (220) being separated from the first carrier frequency by a shift frequency, (ii) a message signal from the transponder (40), carried on the shifted interrogation signal (220), and (iii) unwanted signals, at the first carrier frequency (210), resulting from reflections of the interrogation signal. A low-pass filter (110) has a cut-off frequency lower than the shift frequency. The response signal is mixed with a signal at a frequency separated from the second carrier frequency by no more than the cut-off frequency of the low-pass filter (110) minus half the bandwidth of the message signal to produce a downshifted signal comprising the shifted interrogation signal further shifted to a frequency lower than the cut-off frequency and the unwanted signals shifted to a frequency (210') higher than the cut-off frequency. The low-pass filter (110) is used to remove the unwanted signals from the downshifted signal and thereby to produce a filtered downshifted signal. The message signal is extracted from the filtered downshifted signal.
Abstract:
An electron beam window (20) is formed with six diamond panes (21) to transmit an electron beam (15). The panes (21) are formed in a cylindrical disc (17) of single crystal or of polycrystalline diamond such that each pane (21) is surrounded by a thicker integral peripheral rim (22) which conducts heat away from the panes (21). A heat sink ring (35) can be fitted to the outer cylindrical surface of the peripheral rim (22). A scanning means (36) indexes the electron beam (15) sequentially through each pane (21). The use of diamond panes reduces the electron beam energy converted to heat in each pane (21), the thicker peripheral rim (22) increases cooling of the panes (21), and the scanning movement (37) reduces the temperature rise of the panes (21).
Abstract:
A sensor (10) for detecting an incident RF signal having a carrier frequency, and for estimating said carrier frequency, comprises a plurality of filters (70-73), each allowing passage of signals over a different band of frequencies from the band of frequencies over which passage of signals is allowed by the others of the plurality of filters (70-73), and a plurality of detectors (80-83). Each filter (70-73) is associated with at least one of the plurality of detectors (80-83), and said at least one detector (80-83) is arranged in use to generate an output signal if the incident RF signal results in a signal in the band of frequencies passed by the filter (70-73) with which the detector (80- 83) is associated. Generation of the output signal by the detector (80-83) indicates in which of the frequency bands the incident RF signal has been detected. Between arrival of the incident RF signal at the sensor (10) and generation of the output signal indicating in which of the frequency bands the incident RF signal has been detected, there is a delay of not more than 1 microsecond.
Abstract:
A method of manufacturing a curved circuit assembly comprises providing a circuit board (80) having a surface and a plurality of recesses (10) opening onto the surface. The surface includes a plurality of conductive tracks (30). A circuit assembly is formed by placing an electronic component (20) within each of said recesses (10) and forming a conductive join (50) between the electronic component (20) and at least one of the conducting tracks (30). The circuit assembly is then bent.
Abstract:
The invention comprises a feed horn (10) illuminating a circular flat panel (12) formed from a high impedance surface structure. By controlling the resonant frequencies of the individual elements of the array, a controlled phase shift profile is applied across the surface of the panel to an incident phase front spherically spreading from the feed antenna so as to reflect that wavefront in a particular direction or impose a certain desired beam shape. The principles are reciprocal so a receiving system can also be achieved or indeed a simultaneous transmit and receive operation can be supported. The phase controlled reflecting plate advantageously performs focussing to the feed and beam scanning or beam shaping. This concept of feed to a phased reflector plate allows the power distribution to be implemented in free space. In addition, the active component at each array element affecting the resonant frequency is a single varactor tuning diode per element with negligible power dissipation since it operates in reverse bias or a MeMs switch network. A further embodiment is described comprising a transmissive panel with phase shifting elements implemented in MeMs technology coupled to each element of the array. Calibration techniques are described that correct for non-systematic errors in the phase shifts on reflection which would corrupt the beam shape and pointing direction in a practical environment. These can be performed repeatedly, interleaved with the radar or communications waveforms passing through the antenna.
Abstract:
An electron beam window (20) is formed with six diamond panes (21) to transmit an electron beam (15). The panes (21) are formed in a cylindrical disc (17) of single crystal or of polycrystalline diamond such that each pane (21) is surrounded by a thicker integral peripheral rim (22) which conducts heat away from the panes (21). A heat sink ring (35) can be fitted to the outer cylindrical surface of the peripheral rim (22). A scanning means (36) indexes the electron beam (15) sequentially through each pane (21). The use of diamond panes reduces the electron beam energy converted to heat in each pane (21), the thicker peripheral rim (22) increases cooling of the panes (21), and the scanning movement (37) reduces the temperature rise of the panes (21).