233 results about "Roll-off" patented technology

A tunable duplexer circuit is described, wherein the frequency response as well as bandwidth and transmission loss characteristics can be dynamically altered, providing improved performance for transceiver front-end applications. The rate of roll-off of the frequency response can be adjusted to improve performance when used in duplexer applications. A method is described where the duplexer circuit characteristics are optimized in conjunction with a specific antenna frequency response to provide additional out-of-band rejection in a communication system. Dynamic optimization of both the duplexer circuit and an active antenna system is described to provide improved out-of-band rejection when implemented in RF front-end circuits of communication systems. Other features and embodiments are described in the following detailed descriptions.

A system and a method for code division multiple access (CDMA) communication. The system includes fixed terminals communicating with a central base station. The terminals in protection sectors of each sector are configured to employ codes from different sets of codes to overcome potential mutual interference between sectors on account of antenna radiation pattern roll-off. The remaining codes, preferably the majority of the available codes, are used in any one of a plurality of basic sectors, each of which separates the protection sectors of a respective sector. For an even number of sectors in a cell, the available codes are partitioned into three groups, two for the protection sectors and one for the basic sectors. For an odd number of sectors in a cell, the available codes are partitioned into four groups, three for the protection sectors and one for the basic sectors. Protection sectors are relatively narrow but broad enough to counteract the potential mutual interference between sectors.

Differential input fail safe circuitry is disclosed that detects missing or too low differential signals combined with a frequency lower than a frequency limit where a final safe condition is detected and signaled. The output signal form the fail safe circuitry is held in a given state that is an invalid representation of the differential input signal. A frequency detector, complementary offsetting auxiliary amplifiers with limit frequency roll offs are used to detect the fail safe condition. In addition a delay circuit is used that requires the fail safe condition to exist for some time before the fail safe circuit is active. Initialization circuitry ensures a proper power up conditions where the circuitry is enabled to detect the fail safe conditions and guarantees a reliable fail safe irrespective of the previous state of the signal.

A filter system including a low pass filter having a response which rolls off towards a crossover frequency and a high pass filter having a complementary response which rolls off towards the crossover frequency. The responses are arranged such that the combined response of the filters is substantially constant in amplitude at least in the region of the crossover frequency. The response of the low pass filter is defined by a low pass complex transfer function having a first numerator and a first denominator. The response of the high pass filter is defined by a high pass complex transfer function having a second numerator and a second denominator. The desired response is obtained when the second denominator is substantially the same as the first denominator and the sum of the first and second numerators has substantially the same squared modulus as the first or second denominator.

Several techniques are disclosed for isolating either heart or breath rate data from a photoplethysmograph, which is a time domain signal such as from a pulse oximeter. The techniques involve the use of filtering in the frequency domain, after a Fast Fourier Transform (FFT) has been conducted on a given photoplethysmograph also references as a given set of discrete time-domain data. The filtering may be applied to an identified fundamental frequency and one or more harmonics for heart related parameters. The filter may be truncated to the frequency data set and further applied multiple times to improve roll off. After filtering, an Inverse FFT (IFFT) is used to reconstruct the time-domain signal, except with undesirable frequency content eliminated or reduced. Calculation or measurement of parameters is then conducted on this reconstructed time-domain signal.

A dual polarized variable beam tilt antenna (10) having a plurality of offset element trays (12) each supporting pairs of dipole elements (14) to orient the dipole element pattern boresight at a downtilt. The maximum squint level of the antenna is a consistent downtilt off of boresight and which is at the midpoint of the antenna tilt range. The antenna provides a high roll-off radiation pattern through the use of Yagi dipole elements configured in this arrangement, having a beam front-to-side ratio exceeding 20 dB, a horizontal beam front-to-back ratio exceeding 40 dB, and is operable over an expanded frequency range.

A system and method is provided which suppresses relative intensity noise in a fiber optic gyroscope by taking advantage of the frequency response of erbium fiber. In operation, the gain provided by the erbium fiber is added to the gain of the other components in the feedback loop to provide for stable loop performance up to about 250 kHz. The frequency response of the erbium fiber of about 3 kHz also provides a 6 db per octave roll-off, which, when used in a negative feedback control loop for controlling the current flowing to the gyroscope light source, allows for a relative intensity noise control loop with a bandwidth much greater than 3 kHz; this may be used in high performance gyroscope applications.

In a wireless network having an access point and at least one wireless end device, the access point is operable to differentiate between normal communications and interference from another device in order to capture a sample of the interference, determine whether the interference originates from a known type of device, and prompt remedial actions such as moving communications to a distant channel, increasing transmission power, changing data rate, and packet fragmentation based on whether the interference originates from a known type of device. Interference pulse duration may be used to at least initially narrow the possible sources of interference. Pulse period may be employed to differentiate between interference sources which exhibit similar pulse duration. If pulse duration and period are not sufficient to identify the interference source then other characteristics may be examined, such as pulse waveform, roll off and period in relation to local power frequency. In the case of microwave interference it is generally best to move to a distant channel. Increased transmission power and packet fragmentation can be used to maintain communications while scanning for a new channel.

A method for controlling a filter, a transmitter, a receiver and an apparatus are provided. The apparatus comprises a filter configured to filter signal blocks to be transmitted in a cyclic transmission form and a controller configured to select a roll-off factor of the filter for a signal block depending on whether transmission is performed in a synchronous or an asynchronous mode.

A transmission circuit includes: a modulated signal generator for outputting a modulated signal; an envelope detector for outputting an amplitude modulated voltage; an amplitude roll-off LPF for attenuating the amplitude modulated voltage by using a damping property represented by an exponential function in which an argument is exponentially proportional to a frequency; a power-supply-voltage generator for generating a power supply voltage in accordance with an amplitude value of the amplitude modulated voltage; a phase detector for outputting a phase modulated signal; a phase roll-off LPF for attenuating the phase modulated signal by using a damping property represented by an exponential function in which an argument is exponentially proportional to an offset frequency with respect to a center frequency; and an RF power amplifier.

A base station for use in a wireless network that communicates according to a multi-carrier protocol. The base station receives an uplink signal transmitted by a first subscriber station. The first subscriber station transmits using a configurable spectral shaping filter and a selectable modulation order. The base station determines a required bandwidth efficiency associated with the first subscriber station and, in response to the determination, selects a first modulation order and a first filter parameter to be used by the first subscriber station. Advantageously, the base station selects the first modulation order and the first filter parameter in order to maximize a power efficiency of the first subscriber station while maintaining the required bandwidth efficiency.

By removing a portion of a halo region or by avoiding the formation of the halo region within the extension region, which may be subsequently formed on the basis of a re-grown semiconductor material, the threshold roll off behavior may be significantly improved, wherein an enhanced current drive capability may simultaneously be achieved.

The invention discloses a filtering antenna with low profile, wide band and high gain. The antenna comprises an electromagnetic super-surface radiator and a feed part. The electromagnetic super-surface is constituted by non-uniformly small electrical units and is used as a high-efficiency radiator so that the bandwidth and gain of antenna are increased. At the same time, radiation zero points can be produced, and frequency selectivity can be increased through adjusting roll-off degree of an upper edge of a pass-band. According to the antenna, discrete micro-strip coupling slits are creatively used for feeding; metal via holes are introduced in between the micro-strip and floor; good filtering effect of low frequency stop band is guaranteed; roll-off degree of pass-band lower edges is increased. According to the invention, electromagnetic super-surface with filtering effect is creatively designed and is applied in filtering antenna; the antenna structure is simple and no complicated filtering circuit is used; The height is only 0.06[lambda]0; 10dB impedance bandwidth is 28.4%; antenna loss is low and efficiency reaches up to 95%; in-band average gain is 8.2dBi; out-band rejection is over 20dB; the stop-band is wide.

A fully-integrated continuous-time active complex bandpass IF filter that may contain transmission zeros yielding much sharper roll-off than that of an all-pole filter is implemented using transconductors and capacitors only. Each of the filter second-Order sections realizes a pair of complex poles and a may realize a double imaginary axis zero. Since the transconductors are electronically tunable the positions of filter zeros and poles are adjustable using an automatic tuning system. In each filter section the value of different transconductors are modified to separately change the pole frequency, its Q-factor and the zero frequency. Each pole and zero are separately tuned, which achieves a higher level of tuning accuracy than in case where all poles and zeros were adjusted simultaneously.

A surface-acoustic-wave filter couples a two-port surface-acoustic-wave resonator filter circuit coupled in parallel or in series with a two-port impedance circuit. The two-port impedance circuit has an impedance that creates a pole of attenuation, by making the open-circuit impedance of the surface-acoustic-wave filter equal to the short-circuit impedance. High attenuation over a wide range of stopband frequencies is obtained in this way, combined with steep roll-off between the passband and stopband.