This study presents the design of a phase correlator for a digital frequency discriminator (DFD) that operates in the 2.0-6.0GHz frequency range. The accuracy of frequency discrimination as determined by the isolation of the correlator mixer was analyzed, and LO-RF isolation was found to have a significant effect on the frequency discrimination error by deriving various analytic equations related to the LO-RF isolation and phase performance. We propose a novel technique (phase sector compensation) to improve the accuracy of frequency discrimination. The phase sector compensation technique improved phase error by canceling the DC offset of the I and Q signals for only the frequency bands where the mixer's LO-RF isolation was below a specified limit. In the 2.0-6.0GHz range, the phase error of the designed phase correlator was decreased from 4.57° to 4.23° (RMS), and the frequency accuracy was improved from 1.02MHz to 0.95MHz (RMS). In the 4.8-6.0GHz range, the RMS phase error was improved from 5.59° to 4.12°, the frequency accuracy was improved from 1.24MHz to 0.92MHz, and the performance of the DFD correlator was improved by 26.3% in the frequency sector where LO-RF isolation was poor. Overall, the DFD correlator performance was improved by LO leakage compensation.

In this paper, a new effective C/N0 theoretical model for global navigation satellite system (GNSS) receiver is proposed, in the presence of continuous wave interference (CWI). The proposed model is derived based on an interesting finding, correlator may output direct current (DC) in the presence of CWI. The DC introduced by CWI eventually leads to increase of carrier power estimation. It is totally different from current assumption that interference just causes noise power increase after correlation. The proposed model is verified by simulation.

The Start-frame-delimiter (SFD) is crucial in packet-based communications system since it indicates the end of preamble and the start of a frame. In 802.15 smart utility network system, the function of SFD is extended. Two different SFDs are used for achieving frame synchronization and at the same time, to differentiate coded and uncoded packets. This paper proposes a systematic method for the selection of SFD pair for FSK based systems. The design method is adopted by 802.15.4g Task Group with the backward compatibility to IEEE 802.15.4d systems taken into account. Four selection criteria are specified and discussed to determine the pair of sequences providing least packet error detection rate with the consideration of eliminating the adjacent channel image signal commonly occurred in the low IF receiver. The probability of false alarm and miss detection is analyzed to verify the effectiveness of the proposed selection method. The simulation results confirm that error frame detection rate of 1e-3 can be achieved with selected SFD sequences. The proposed method for selection of SFD pairs ensures a robust packet header and thus better payload protection. The SFD design approach is applicable to other packet-based wireless communication FSK systems with the support of more than one SFD sequence.

In this letter, we first present a new construction method for uncorrelated binary periodic Complementary sequence sets (CSS). Next, the uncorrelated periodic CSSs are used as pilot sequences for multiple-input multiple-output (MIMO) channel estimation. Later on, we propose a low-complexity periodic correlator. Finally, simulation results verify the optimality of pilot sequences for MIMO channel estimation.

A low power impulse radio ultra-wideband (IR-UWB) receiver for DC-960 MHz band is proposed in this paper. The proposed receiver employs multiple DC power-free charge-domain sampling correlators to eliminate the need for phase synchronization. To alleviate BER degradation due to an increased charge injection in a subtraction operation in the sampling correlator than that of an addition operation, a comparator with variable threshold (=offset) voltage is used, which enables an addition-only operation. The developed receiver fabricated in 1.2 V 65 nm CMOS achieves the lowest energy consumption of 17.6 pJ/bit at 100 Mbps in state-of-the-art correlation-based UWB receivers.

The critical problem of the pseudo-noise (PN) code acquisition system is the contradiction between the acquisition performance and the calculation complexity. This paper presents a low cost correlator (LCC) structure that can search for two PN code phases in a single accumulation period by eliminating redundant computation. Compared with the part-parallel structure that is composed of two serial correlators (PARALLEL2), the proposed LCC structure has the same performance while saves about 22% chip area and 34% power consumption if uses the Carry-look-ahead (CLA) adder, 17% chip area and 25% power consumption if uses the Ripple-carry (RPL) adder.

This letter presents a new TR-UWB receiver exploiting frequency components of UWB pulses. This is accomplished by separating frequency-components of UWB pulses into real and imaginary parts, independently correlating and effectively combining them. We analytically show this scheme improves the output SNR compared with a conventional one using complex correlation. This will also be justified by simulation results.

Improving GPS positioning accuracy requires an understanding of the inner workings of GPS receivers. However, the necessary hardware and software for research is prohibitively expensive. It is almost impossible to modify the correlator and functions of signal acquisition and tracking in commercial GPS hardware. The software GPS receiver allows us to access the inner workings of the receiver without significant time or expense. The present paper introduces a prototype software GPS receiver developed by us, which consists of a commercial RF-module and PC-based signal processing software. In addition, the software GPS receiver is shown herein to enable evaluation and mitigation of the code multipath error with the outputs of a software multi-correlator, which can be implemented easily in a software GPS receiver, with the aid of maximum likelihood criteria.

A seven-port wave-correlator based vector network analyzer is proposed. The seven-port wave-correlator is a combination of two six-port wave-correlators which share common components. Furthermore, the complex wave ratio measurement accuracy is improved since the input signals can be directly detected by the side-arm ports. A seven-port wave-correlator is fabricated using microstrip branch line couplers. The performance of the wave-correlator and the constructed network analyzer are evaluated, and the measurement accuracy is confirmed.

A finite impulse response (FIR) core based on the cascoded class AB SI technique is presented for low power wireless transceivers. Accomplished through both architectural and circuit developments, the filter's features include high speed, low power consumption, small silicon area and compatibility with standard CMOS process. For feasibility and performance assessments, an 8-tap 16 MS/s SI FIR filter with 5-bit coefficients and a 31-tap 80 MS/s SI matched filter (MF) for despreading task in future WCDMA receivers are demonstrated via simulations.

This paper presents a new automatic-frequency control (AFC) configuration capable of removing wide range frequency offsets (up to about 0.625 fs, where fs is signal symbol rate). The new configuration consists of an AFC that removes frequency offsets between 0.125 fs and another AFC that detects the frequency offset range coarsely between 0.625 fs. This paper describes the principle of the new AFC configuration. The proposed AFC configuration employs four correlators to enhance the acquisition range. It also adopts the reverse modulation scheme to decrease the acquisition time. The performance of the new AFC configuration is confirmed via computer simulations. It is shown that the proposed configuration can accommodate wide range frequency offsets as well as reduce the acquisition time.

This paper describes the experimental approach of the Direct Optical Switching (DOS) CDM Radio-on-Fiber (RoF) system. Improved carrier-to-interference ratio (CIR) performance by using an Optical Polarity Reversing Correlator (OPRC) in comparison to using a single switch decoder is experimentally obtained. In addition, CIR performance deterioration due to degradation of the extinction ratio of the optical switch decoder is clarified from the theoretical and experimental viewpoints. Finally, we confirmed that CIR performance is improved more by using an M-sequence whose weight is even numbered than by using an odd numbered one.

We propose an extended one-shot decorrelating detector (EOS-DD) which may be viewed as a generalized double window multiuser detector (DW-MD) for asynchronous direct-sequence code-division multiple-access (DS/CDMA) systems in frequency selective fading environments. The EOS-DD extends a processing window and the received signal over an extended window is utilized for decorrelating. The effects of the window size on BER performance are investigated by numerical analysis. Analysis and simulation show that the EOS-DD is superior to the one-shot decorrelating detector (OS-DD) and finite memory length truncated decorrelating detector (FIR-DD) in terms of noise enhancement and near-far resistance. It is also shown that the EOS-DD with window size 4 can provide significantly improved performance compared to the EOS-DD with window size 2.

A new analog correlator circuit is proposed for direct sequence code division multiple access (DS-CDMA) demodulator. The circuit consists of only 16 switches, 4 capacitors and 2 level shifters. Control sequence requires only three clock phases. Simulation with code length of 127 reveals that the proposed circuit has a good ability to cancel off the charge error and dissipates 3.4mW at 128MHz. The circuit had been designed using a 0.6µm CMOS process. The area of 256µm 245µm is estimated to be 9 times smaller compared to other reported equivalent analog correlators.

As a new type of a linear decorrelating receiver, the Pseudo-Decorrelator was presented for asynchronous code division multiple access systems in [6]. In this paper, the concept of the Pseudo-Decorrelator is extended to derive a suboptimal receiver for WCDMA uplink systems in a Rayleigh fading environment. Starting with the analysis of the multiple access components of the decision statistics, a non-square cross-correlation matrix for each bit is obtained. This cross-correlation matrix is then inverted and the inverted matrix is applied to the decision statistics obtained from a conventional receiver. Simulation results are presented for K-user systems over a Rayleigh fading channel. The effects of the synchronization errors, such as time delays and carrier phase errors, are also examined through simulations in this paper.

In this paper, we discuss power spectrum overlapping of wideband/narrowband signals and wideband/wideband signals for increasing transmission efficiency. Here, in order to eliminate cross signal interference among those signals, we propose a generalized zero-forcing type decorrelating detection. Our numerical results show that, with the decorrelating detector, the overlapped wideband/wideband signal transmission can much improve the transmission efficiency. This implies that, for a given frequency bandwidth, in order to increase the information transmission rate, we should employ two different kinds of direct sequence spread spectrum-based signals with each power spectrum appropriately overlapped, not taking a single carrier-based approach nor an orthogonal multi-carrier approach.

Digital logic frequency detector whose operation is based on the analog quadricorrelator is presented. Proposed circuit consists of conventional digital logic devices without an alog elements. Therefore, it has superior reliabilities over component drifts or aging effects. Frequency linear discrimination range is 100% of the reference clock rate.

This letter newly proposes the polarity-reversing type photonic receiving scheme based on bipolar correlation for optical CDMA signal in radio highway. The proposed scheme can more improve the limitation of the number of radio base stations connected to radio highway and more reduce the peak laser power at the radio base station than the conventional unipolar type receiving scheme using prime codes.

This paper proposes a new multiuser detector, quasi-decorrelating detector (QDD), for a synchronous CDMA system. The QDD has the same complexity as that of decorrelator detector (DD) although it uses feedback loops, the number of which is adjustable to balance the near-far resistance and noise enhancement. The results show that the QDD outperforms the DD under various operational conditions. The impact of different spreading codes on the performance of the QDD is studied. It is shown that the Gold code is the best spreading code suitable for the QDD.

A direct-conversion receiver with a full digital logic FSK demodulator is presented. It is developed from the quadricorrelator which is known as a frequency detector. We show that the performance of the receiver converges to that of the analog quadricorrelator receiver as the number of mixing axes increases, and obtain the optimum filter bandwidth by computer simulation.