Abstract: Radio frequency (RF) receivers and methods to spread spectral energy of spurious responses of mixers over a frequency band are disclosed. For example, a receiver includes first and second mixers, and first and second variable frequency oscillators (VFOs). The first mixer is configured to receive an RF signal and provide an intermediate frequency (IF) signal. The second mixer is coupled with the first mixer and configured to receive the IF signal and provide a baseband signal. The first VFO is coupled with the first mixer and configured to provide a first angle modulated LO signal. The second VFO is coupled with the second mixer and configured to provide a second angle modulated LO signal. The first and second mixers provide a stable frequency downconversion.

Abstract: An electromagnetic interference (EMI) signal is processed by digitizing the EMI signal, generating a plurality of overlapping time records from the digitized EMI signal, applying a window function to the plurality of overlapping time records to produce a plurality of modified time records, wherein the window function has a substantially flat top, and performing a fast Fourier transform (FFT) on each of the modified time records to produce a plurality of corresponding amplitude envelopes.

Abstract: A radio communication system a primary station and a secondary station operating according to two (or more) two-way communication modes. An uplink and/or a downlink communication channel is present for the first mode, but only one of an uplink and a downlink channel is present for the second mode. Modifications to the protocols of the first and second modes enable the traffic for an absent communication channel of one mode to be carried by the corresponding channel of the other mode.

Abstract: A personal communications apparatus comprises a first part, having a microphone (114), and a second part, having a loudspeaker (118). The first part is adapted to be worn on a user's wrist (202) and the second part is adapted to be worn on their finger. In use, the user's hand is held up to the side of their head, thereby placing the microphone (114) adjacent to their mouth and the loudspeaker (118) adjacent to their ear. Communication between first and second parts of the apparatus is by means of signals transmitted via the user's skin. In a non-illustrated embodiment the second part is adapted to be worn on the ear.

Abstract: A low IF receiver suitable for use in cellular and cordless telephones and TV tuners, comprises input signal receiving means(10), quadrature related frequency down conversion means including first and second mixing means(14, 15) having first inputs(12, 13) coupled to the input signal receiving means and a local oscillator means(16) for generating a local oscillator signal having a frequency offset from a nominal centre frequency of the input signal coupled to second inputs(18, 19) of the first and second mixing means, a channel selectivity polyphase filtering means(20) for selecting a wanted channel signal from outputs of the first and second mixing means, means(26, 28, 30) for detecting when the quality of the frequency down converted signal becomes unacceptable due a large adjacent channel interfering component and means responsive to said detection for changing the local oscillator frequency by at least twice the low IF or one channel bandwidth to displace the large interfering component outside the bandwi

Abstract: A radio communication system comprising a primary station (100) and a secondary station (110) operates according to two (or more) two-way communication modes. An uplink (124) and/or a downlink (122) communication channel is present for the first mode, but only one of an uplink and a downlink (126) channel is present for the second mode. Modifications to the protocols of the first and second modes enable the traffic for an absent communication channel of one mode to be carried by the corresponding channel of the other mode.

Abstract: An integrated receiver in which in order to permit ac-coupling between stages and to remove the effects of strong directly detected amplitude modulated interfering signals lying within the input band of the receiver, the input signal is frequency down converted using a local oscillator signal which provides an intermediate frequency (F.sub.if) which lies above the frequency of the directly detected interferer (F.sub.AMP). The outputs from the frequency down converters (14, 16, 18, 20) are ac coupled to filtering means the outputs of which are applied to an equalizer (52). The filtering means may comprise a polyphase filter (50), the frequency response of which is distorted by the ac coupling capacitors (54, 56). By applying the outputs of the filtering means to the equalizer (52) substantially all the distortion introduced by the ac coupling capacitors (54, 56) on the filter response is removed to provide an acceptable signal for detection and recovery of the modulating signal.

Abstract: A radio receiver (16) for direct sequence spread spectrum signals incorporates a quadrature zero-IF architecture, means for comb filtering (36,37) the two quadrature related channels (I and Q) and a means of non-coherent demodulation of each channel; the non-coherent demodulating means comprising delays (40,41) and mixers (42,43). This process obviates the need for locally generated versions of the spreading code used to produce the signals and considerably shortens the time-consuming process of correlating the received and the locally generated codes at receiver switch-on.

Abstract: Signals from a number of NAVSTAR global positioning system (GPS) satellites (11,12,13,14) are received by a receiver (16) in a vehicle (15) and a segment of the signals is stored in a memory (18) prior to retransmission by a transmitter (19). A base station (35) receives these transmissions from the mobile unit using a first receiver (36). The base station also receives signals directly from the NAVSTAR GPS satellites using a second receiver (38). A control and calculating apparatus (37) within the base station can determine the ephemeris (course) information for the satellites and can measure the transmission times or propagation delays of signals between the satellites and the vehicle and with this information the control and calculating apparatus can calculate the position of the vehicle unit.

Abstract: When fewer than three of the satellites of a satellite global positioning system (GPS) such as NAVSTAR are visible to a user (15), the user cannot obtain independent positional information from the system. Since a satellite (11) in such a system is moving with respect to a user (15), its signals are received with a Doppler offset from their normal centre frequency and the frequency offset due to the satellite motion alone is calculable for a user at an approximate location from a given satellite. An additional Doppler frequency offset will result from any movement of the user. The magnitude of the additional frequency shift, in conjunction with the known speed (m) of the user, can be used to calculate the angle between the satellite motion (V.sub.1) and the user's motion and since the direction of the former is known, the user's heading from local North (N) can be calculated in instances where only one or two GPS satellites (11,12) are visible to a user.

Abstract: A target detection system is provided for examining picture signals of a scene which may contain a target signal (15,16) to be detected against background signals (17,18). The image is divided into sub-images and sub-stores are provided one each for the sub-images (19). The values of a set of features, such as brightness, volume or quietness, of the background and target picture signals associated with each sub-image in the respective sub-store are calculated and stored. The statistical distributions of the background and target features in each sub-store to set a target decision threshold, in feature terms, for each sub-image are calculated. The feature values of an incoming picture signal in a sub-image are compared with the decision threshold in the associated sub-store to provide a target detection signal. Each sub-image threshold relates to the image status in that particular sub-image. A lower false alarm rate with a higher detection probability is provided.

Abstract: A zero-IF radio receiver circuit comprises an input filter (3), quadrature mixers (9,10), d.c.-blocking capacitors (24,26) and a demodulator (22). The circuit is partly integrated on a semiconductor chip and an inductive component of the input filter comprises one or more of the chip bond-wires. In order to compensate for the inevitable variation of the inductance of these bond-wires from circuit to circuit part of the signal from the local oscillator (12) is added to the input signal before its application to the input filter and the d.c. component of the resulting output from one mixer (10), which component is representative of the phase shift of the local oscillator signal produced by the input filter and hence of any tuning error of this filter, is applied to a tuning control input (30) of the filter to reduce the error. Alternatively the tuning control signal may be adjusted to maximize the sum of the squares of the d.c.

Abstract: A surface acoustic wave device comprises a transducer 1 consisting of two electrodes 2 and 3 deposited on the surface of a substrate 4. Transducer 1 is a slanted chirped transducer with short fingers 5 and 6 to focus any acoustic wave generated in the transducer to a position along a line 8 spaced from transducer dependent on the frequency of the signal.

Abstract: Signals from a number of NAVSTAR global positioning system (GPS) satellites (11,12,13,14) are received by a receiver (16) in a vehicle (15) and a segment of the signals is stored in a memory (18) prior to retransmission by a transmitter (19). A base station (35) receives these transmissions from the mobile unit using a first receiver (36). The base station also receives signals directly from the NAVSTAR GPS satellites using a second receiver (38). A control and calculating apparatus (37) within the base station can determine the ephemeris (course) information for the satellites and can measure the transmission times or propagation delays of signals between the satellites and the vehicle and with this information the control and calculating apparatus can calculate the position of the vehicle unit.