In this paper, a high-efficiency high-power rectenna with a bridge diode and the diode on antenna (DoA) topology is discussed. First, the topologies of rectifiers and rectennas are discussed to indicate the direction for obtaining highly efficient rectification. Rectifiers with well-matched diode pairs, as double voltage and bridge rectifiers, can reactively terminate even order harmonics, and is suitable for highly efficient operation. A rectenna with the DoA topology is suitable for a direct connection between the highly functional antenna and the rectifier diodes to remove lossy circuit portions. Next, the formulas for the rectification efficiency of the bridge rectifier are demonstrated with the behavioral model. The indicated formulas clarify the fundamental limitation on the rectification efficiency, which is the design goal in case of the DoA topology. Finally, we demonstrate a 5.8 GHz band 1 W rectenna with the bridge diode and the DoA topology. The bridge rectifier that is directly connected to the inductive high-impedance antenna achieved a rectification efficiency of 92.8% at an input power of 1 W. This is close to the fundamental limitation due to the diode performance.

This letter presents a low spurious frequency setting algorithm for a triple tuned type PLL synthesizer driven by a DDS. The triple tuned PLL synthesizer is based on a single PLL configuration with two variable frequency dividers. The DDS is employed for a reference source of the PLL. The proposed algorithm determines appropriate frequency tuning values of the DDS frequency and the division ratios of two frequency dividers. The division ratios are selected to achieve a desired output frequency while the low spurious condition of the DDS has been maintained. A 5 to 10 GHz synthesizer with frequency step of 500 kHz demonstrated spurious level below -46 dBc with improvement of 13 dB.

This paper presents an even harmonic quadrature mixer (EH-QMIX) with a simple filter configuration and an integrated LTCC module including LNAs, band rejection filters (BRFs), and the proposed EH-QMIX for W-CDMA direct conversion receiver (DCR). Since the DCR has no spurious responses, a BRF instead of a high-Q band pass filter can be applicable for eliminating undesired signals and it can be built in the LTCC substrates easily. As LO frequency is half of RF frequency in the EH-QMIX, diplexer can be composed of simple filters and it can be also integrated in the substrates. As a result, the whole RF circuits of the EH-DCR using a proposed EH-QMIX are integrated in the LTCC module and miniaturization of the receiver is achieved. Moreover, in order to suppress the degradation of the amplitude and the phase imbalances in the quadrature mixer caused by interferences of signals, RF characteristics of the circuits in the mixer such as reflection coefficients, isolations are discussed. A developed LTCC module shows good performances for W-CDMA direct conversion receiver.

A model of bilateral interaction in the auditory nervous system was presented on the basis of digital-chemical-analog functions of neuro-synaptic circuits in order to analyze the mechanism of cross correlational information processing for sound localization. The system was composed of a bilateral pair of auditory relay nuclei, i.e., cochlear neclei, superior olives, and inferior colliculei as well as a pair of trapezoid bodies which connect contralateral cochlear nucleus and ipsilateral superior olive. The model could detect interaural phase differences using the interaction of excitatory and inhibitory postsynaptic potentials evoked by the respective ipsilateral and contralateral putputs of the cochlear nuclei rather than Bergeijk's or, originally, Békésy's travelling waves on phase detection cells. The two parameters on sound image, lateralization index and probability fusion were introduced as the difference and the sum of the bilateral outputs of superior olives, respectively. The effect of 'phase-intensity trade' as well as 'time-intensity trade' was simulated in the model to compare with the experimental results. Dominancy for binaural information processing was discussed and the possibility of inter- and intra-modal information processing involving temporal operations among analogous postsynaptic potentials from various sensory inputs was suggested.

This paper presents an even harmonic mixer using self-biased anti-parallel diode pair (APDP). A proposed self-biased APDP is composed of a pair of diodes and self-bias series resistors. At high LO injection level, rectified current is generated by the diodes and reverse voltage is applied to the diodes by the self-bias resistor. Therefore, rapid degradation of conversion loss at high LO input level can be avoided. The effect of self-bias resistor is explained by using simplified behavior model and harmonic balance method, and is evaluated by the measurements of an L-band even harmonic type direct conversion mixer.

This paper presents novel phase-continuous frequency hopping (FH) control for a direct frequency synthesizer (DFS) using a quadrature mixer driven by two direct digital synthesizers (DDSs). To achieve wideband FH in both of the lower and the upper sidebands of a local frequency in a quadrature mixer, the proposed DFS decreases or increases the phase of DDS output signals corresponding to frequency offset from a local frequency of the quadrature mixer. To realize phase decrement, the proposed method adds a complement number in a phase accumulator of a DDS, while a conventional DDS does not use phase decrement but uses a switchable combiner. In addition, as the phase accumulator output changes continuously by summing phase increment, the proposed method always assures phase continuity of a DFS output signal, which ends up suppressing sidelobe level of frequency hopped signals. The calculation and measurement results indicate that a sidelobe of a signal spectrum using the proposed phase continuous method is approximately 10 dB better than that using a conventional phase discontinuous method.

This paper describes the distortion characteristics of an even harmonic type direct converter (EH-DC) used in earth stations for CDMA satellite communications. Direct conversion technique is known as a method to simplify circuit topologies of microwave transceivers. In satellite communications, multi carriers which have high and nearly equal level are provided to a quadrature mixer of the EH-DC. Hence, the third-order intermodulation degrades receiving characteristics. In this paper, we show the relationship between the distortion characteristics and noise figure of the EH-DC for CDMA satellite communication systems. Furthermore, we show NPR of even harmonic quadrature mixers caused by the third-order intermodulation. Experimental results in X-band indicate that the proposed EH-DC has almost the same BER characteristics compared with a heterodyne type transceiver.

An even harmonic quadrature mixer (EH-QMIX) with a balanced configuration is proposed for a direct conversion receiver. The unit even harmonic mixer (EHMIX) used for I/Q paths consists of two anti parallel diode pairs (APDPs) and a pair of diplexers. When the second harmonic of LO (2LO) from the LO section is applied to the LO port as a spurious component, a conventional single-ended EHMIX using APDP converts the 2LO leakage from the LO section into the baseband and the d.c. offset and the self-detected LO noise arise at the baseband degrade the sensitivity. This proposed balanced EHMIX configuration can cancel out the 2LO leakage in itself. Therefore, the d.c. offset and the LO noise are significantly suppressed and the degradation of the sensitivity can be avoided. The suppression characteristic of the d.c. offset and the LO noise are verified by the simulation and the measurements. By using this balanced configuration, the fabricated EH-QMIX achieves wider frequency band characteristic than that of the single-ended EH-QMIX, and it shows 20% relative bandwidth at L-band.