Abstract:
A delay locked loop circuit (200) in which multiple outputs are produced. A single delay line (24) is shared among multiple tap selection circuits (256A, 265B, 265C). Fixed phase shifts (412) can be introduced between multiple outputs. A modulating signal can be used in the tap selection processing to produce digital amplitude, frequency and/or phase modulation.
Abstract:
A communication device (100) includes first (104) and second (108) mixers for producing first in-phase and quadrature phase component, respectively. Additional zero-crossing points are efficiently generated by adding and subtracting the in-phase and quadrature components in a summer (116) and a subtractor (118), respectively. The additional zero-crossing points are generated by the formation of second in-phase and quadrature components. A zero-crossing detector (128) is used for detecting zero crossings using the first and second in-phase components and the first and second quadrature phase components.
Abstract:
A digital frequency synthesizer circuit with spur compensation includes a demodulator circuit (118) for demodulating the output signal (116) of the synthesizer's accumulator (108). Demodulator (118) also inverts the signal, and provides an inverted demodulated output signal (142) which is then coupled to the synthesizer clock (124) after passing through a gain stage (122) in order to modulate the synthesizer clock (124) with a compensation signal (146). The compensated clock signal (140) is then sent to accumulator (108) in order to substantially cancel out any jitter in the accumulator's output signal (116). The modulation signal (MOD IN) which is digitally applied to accumulator (108) is applied in analog fashion to the gain stage (122) in order to prevent the desired modulation signal (MOD IN) from being canceled in the output signal (116).
Abstract:
A balanced mixer circuit (200) includes a first balanced input (RF(+) and RF(-)), a second balanced input (LO(+) and LO(-)), and a balanced output (OUT+ and OUT-). The balanced mixer circuit (200) also includes a mixer (210) for mixing a first signal with a second signal. The mixer (210) further includes a first input and second input which is coupled to the second input of the balanced mixer circuit (200). The balanced mixer circuit (200) also includes a pair of couplers (204 and 206) for coupling the first input of the mixer circuit (200) to the first input of the mixer (210). Each of the pair of couplers (204 and 206) includes a feedback circuit (202 and 208) for improving the performance of the balanced mixer circuit (200).
Abstract:
An RSSI signal for indicating the strength of a received signal in a zero IF receiver is provided. The RSSI signal and the received signal level are logarithmically proportional. The received signal is mixed down in a down mixer (120), and produces a ZIF signal (125) having a substantially low frequency. The ZIF signal (125) is applied to an up mixer (140), and the output of the up mixer is applied to an AGC circuit (150). The AGC circuit (150) maintains the ZIF signal level constant by lowering the gain of the down mixer (120), after the received signal level has exceeded a threshold level. A first RSSI circuit (160) provides a first RSSI signal (165), when the received signal level is below the threshold level. A second RSSI circuit (190) provides a second RSSI signal (195), when the received signal is above the threshold level. Diodes provide a logarithmic transfer function for the first and second RSSI circuits. The first and second RSSI signals are summed together, by a summer (140), to provide a logarithmic RSSI signal.
Abstract:
A radio frequency signal received by a receiver (10) is processed via a voltage-to-current converter (7) to provide a current signal (50) to an integrated IF filter (15). The IF filter (15) is constructed and arranged such that the filter has a capacitive element (64) across its input (62). The current signal and filter arrangement operate to alleviate the problem of the increasing intermodulation and desensitization which would otherwise degrade the performance characteristics of the receiver.
Abstract:
A receiver (202) has a down-conversion receiver (304) for transforming a signal (201) from a first operating frequency to a second frequency that is lower than the first operating frequency, and a receiver filter (308) with chopper stabilization for filtering unwanted portions of the signal (306) at the second operating frequency and for generating a final filtered signal (203) at the second operating frequency.
Abstract:
Un émetteur-récepteur radio (100) est couplé à la source d'un signal de référence (13) et comporte un mode de réception et un mode de transmission. L'émetteur-récepteur (100) comprend un premier changeur de fréquence (16), un premier commutateur de couplage sélectif (S1). Le premier changeur de fréquence (16) est couplé de manière à recevoir un signal d'entrée possédant une fréquence d'entrée, afin de mélanger le signal d'entrée avec le signal de référence pour produire un premier signal. Le premier signal possède une fréquence sensiblement inférieure à la fréquence d'entrée. Le premier filtre passe-bas (20) est couplé au premier changeur de fréquence (16) pour produire un premier signal filtré. Le premier commutateur de couplage sélectif (S1) se connecte au premier changeur de fréquence et au filtre passe-bas (20) quand l'émetteur-récepteur radio (100) est en mode de réception et se déconnecte du premier changeur de fréquence (16) et du filtre passe-bas (20) quand l'émetteur-récepteur radio (100) est en mode de transmission, de ce fait éliminant pratiquement les perturbations transitoires.